The Chemistry of Acid Rain. Sources and Atmospheric Processes 9780841214149, 9780841211933, 0-8412-1414-X

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Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.fw001

The Chemistry of Acid Rain

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.fw001

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

ACS

SYMPOSIUM

SERIES

349

The Chemistry of Acid Rain

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.fw001

Sources and Atmospheric Processes Russell W. Johnson, EDITOR Allied Signal Engineered Materials Research Center

Glen E . Gordon, EDITOR University of Maryland

William Calkins, ASSOCIATE EDITOR Wilmington, DE

A. Z. Elzerman, ASSOCIATE EDITOR Environmental Systems Engineering

Developed from asymposiumsponsored by the Divisions of Petroleum Chemistry, Inc., Nuclear Chemistry and Technology, Environmental Chemistry, and Fuel Chemistry at the 191st Meeting of the American Chemical Society, New York, New York, April 13-18, 1986

American Chemical Society, Washington, DC 1987 In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

L i b r a r y of Congress Cataloging-in-Publication Data American Chemical Society. Meeting (191st: 1986: New York, NY.)

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.fw001

The chemistry of acid rain: sources and atmospheric processes Russell W. Johnson, Glen E. Gordon, editors, p. cm.—(ACS symposium series; 349) "Developed from a symposium sponsored by the Division of Petroleum Chemistry...at the 191st Meeting of the American Chemical Society, New York, N.Y., April 13-18, 1986." Includes bibliographies and indexes. ISBN 0-8412-1414-X 1. Acid rain—Congresses. 2. Atmospheric chemistry—Congresses. 3. Air—Pollution— Congresses. I. Johnson, Russell W., 1948. II. Gordon, Glen, 1935. III. American Chemical Society. Division of Petroleum Chemistry. IV. Title. V. Series. TD196.A25A42 628.5'32-dc19

1986

87-19404 CIP

Copyright © 1987 American Chemical Society All Rights Reserved. The appearance of the code at the bottom of the first page of each chapter in this volume indicates the copyright owner's consent that reprographic copies of the chapter may be made for personal or internal use or for the personal or internal use of specific clients. This consent is given on the condition, however, that the copier pay the stated per copy fee through the Copyright Clearance Center, Inc., 27 Congress Street, Salem, M A 01970, for copying beyond that permitted by Sections 107 or 108 of the U.S. Copyright Law. This consent does not extend to copying or transmission by any means—graphic or electronic—for any other purpose, such as for general distribution, for advertising or promotional purposes, for creating a new collective work, for resale, or for information storage and retrieval systems. The copying fee for each chapter is indicated in the code at the bottom of the first page of the chapter. The citation of trade names and/or names of manufacturers in this publication is not to be construed as an endorsement or as approval by ACS of the commercial products or services referenced herein; nor should the mere reference herein to any drawing, specification, chemical process, or other data be regarded as a license or as a conveyance of any right or permission, to the holder, reader, or any other person or corporation, to manufacture, reproduce, use, or sell any patented invention or copyrighted work that may in any way be related thereto. Registered names, trademarks, etc., used in this publication, even without specific indication thereof, are not to be considered unprotected by law. PRINTED IN THE UNITED STATES OF AMERICA

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

ACS Symposium Series M . Joan Comstock, Series Editor

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.fw001

1987 Advisory Board Harvey W. Blanch University of California—Berkeley

Vincent D. McGinniss Battelle Columbus Laboratories

Alan Elzerman Clemson University

W. H . Norton J. T. Baker Chemical Company

John W. Finley Nabisco Brands, Inc.

James C . Randall Exxon Chemical Company

Marye Anne Fox The University of Texas—Austin

E . Reichmanis AT&T Bell Laboratories

Martin L . Gorbaty Exxon Research and Engineering Co.

C . M . Roland U.S. Naval Research Laboratory

Roland F. Hirsch U.S. Department of Energy

W. D. Shults Oak Ridge National Laboratory

G . Wayne Ivie USDA, Agricultural Research Service

Geoffrey K. Smith Rohm & Haas Co.

Rudolph J. Marcus Consultant, Computers & Chemistry Research

Douglas B. Walters National Institute of Environmental Health

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.fw001

Foreword The ACS SYMPOSIUM SERIES was founded in 1974 to provide a medium for publishing symposia quickly in book form. The format of the Series parallels that of the continuing ADVANCES IN CHEMISTRY SERIES except that, in order to save time, the papers are not typeset but are reproduced as they are submitted by the authors in camera-ready form. Papers are reviewed under the supervision of the Editors with the assistance of the Series Advisory Board and are selected to maintain the integrity of the symposia; however, verbatim reproductions of previously published papers are not accepted. Both reviews and reports of research are acceptable, because symposia may embrace both types of presentation.

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.pr001

Preface DURING T H E PAST D E C A D E , acid deposition, more commonly called "acid rain" has been the air pollution problem of highest concern in the United States. It has caused serious political friction between environmentalists and power companies, between states that burn coal for electric power production and those upon whom the acid rain falls, and even between the United States and Canada, where many citizens feel they are victims of acid exported from the United States. To those who are not experts in atmospheric chemistry, it seems simple enough: What goes up must come down. If you want less acid rain, reduce emissions of sulfur and nitrogen oxides that produce it. However, the atmosphere is a complex system and if we do not understand the formation and deposition of acids, there is a definite possibility that we will devise solutions costing tens of billions of dollars without significantly lessening the severity of problems that have been attributed to acid rain. Although the mechanism for the production and deposition of acid are not yet fully understood, atmospheric chemists and meteorologists have been studying these problems in depth for the past several years and have made considerable progress. Methods and instruments for reliable measure­ ments of key species in air and clouds have been developed and exploited in field studies. Rates of reactions important in the formation of acids, sulfates, and nitrates have been measured. Huge amounts of reliable field data have been accumulated. Models have been developed and are being tested against bodies offielddata. The objective of this volume is to describe recent advances in the understanding of the sources and chemistry of acidic species in the atmosphere.

We thank the authors for their contributions to this Volume. R U S S E L L W. J O H N S O N

Allied Signal Engineered Materials Research Center Des Plaines, IL 60017-5016 GLEN

Ε.

GORDON

University of Maryland College Park, MD 20742 July 20, 1987 xi

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Chapter 1

A Decade of Acid Rain Research Glen E. Gordon

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch001

Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742

M u c h progress has been made i n our understanding of the sources, formation and deposition o f acid and sulfate. Large field studies can be conducted with good quality control o f analyses and data. In the gas phase, ∙OH radicals are known to be capable of converting SO to sul­ fate fast enough to be important. Rates for Η O , O and O i n cloud droplets are fast under certain conditions. However, serious gaps i n our knowledge still exist, especially methods for measuring and predict­ ing dry deposition and estimates ofthe supply of reactants to active cloud systems. A focal point for development of the U. S. control strategy is the Regional A c i d Deposition M o d e l ( R A D M ) . Uncertainties i n some features o f the model are likely to be so large that it may not provide credible predictions i n a time soon enough to be useful to legis­ lators or regulators. H y b r i d receptor models may be able to provide some answers for sulfur species more quickly, although RADM should ultimately yield more detailed predictions for more species. M a n y prob­ lems attributed to acid rain, especially damage to trees at high altitudes, may be largely due to some other species, e.g., H O or O . 2

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In the late 1940s and the 1950s, concerns about air pollution increased enormously because of episodes such as the London F o g o f 1952, the Donora, P A episode of 1948, and other similar incidents. The air was physically being cleaned up by use of electrostatic precipitators to remove most visible emissions; however, large amounts of S 0 were being released in metropolitan areas, and it was felt that the SO^ com­ bined with particles and droplets i n the air was responsible for the abnormally high death and illness rates observed during the episodes. London attacked its problems by a variety of clean-up methods, the most important being the banning o f coal-burning in individual living units, resulting in a considerable improvement i n both air quality and local climate! The main U . S. response was restrictions on the use of high sulfur fuels within metropolitan areas, which had the effect of forcing in-town sources to switch to low sulfur oil and gas and for new plants to have tall stacks and be built outside of cities. A s documented by Altshuller CI), these measures reduced urban levels of S 0 to nearly rural levels. Nearly simultaneously with the U . S. success i n reducing urban S 0 levels, the Community Health and Environmental Surveillance System ( C H E S S ) reported that adverse health effects result not from S 0 itself, but from the secondary sulfates and 2

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0097-6156/87/0349-0002$06.00/0 © 1987 American Chemical Society

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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Η ^ 0 formed by atmospheric chemical reactions after release of primary S 0 (2). Furthermore, the moves taken to reduce S 0 concentrations i n cities simply moved the sources to rural areas and increased the altitudes of release, but did not reduce the total amount released. Since S 0 is converted slowly to sulfate over long distances, concentrations o f particulate sulfates were nearly as great over large rural areas of the eastern U . S. as i n cities (1). N o t only were these ubiquitous sulfates of concern because o f health effects, but it was soon recognized that particulate sulfates were largely responsible for the haze that blankets huge areas of the East during Summer (3), even the "smoke" of the Great Smoky Mountains, which had previously been attributed to particles formed from terpenes emitted by trees. This set of problems related to the release of SCX, mainly by coal-fired power plants, was the impetus for large field studies, especially the Sulfur Regional Experiment ( S U R E ) , supported by the Electric Power Research Institute (EPRI) (see G . M . H i d y , This Volume). A t about this point i n the mid-1970s, results of C H E S S were discounted, largely because of the measurement methods used (2). This does not necessarily mean that sulfates are not harmful to humans, but that we have no proof that they are. This would have removed much of the impetus for studies of atmospheric S 0 and sul­ fates; however, at about that time, Likens and others (4) published contour plots of the p H o f rainfall i n the Eastern U . S. for the mid-1950s and the mid-1970s which purported to show that the acidity of precipitation had increased greatly over this period. Earlier, Swedish scientists had observed increasing acidity of lakes i n Scan­ dinavia, causing many species of fish to disappear from affected lakes. The decrease of fish life i n many lakes of N e w England and Upper N e w Y o r k State was thought by many to be the result o f acid rain. Later, damage to trees, especially high on mountain slopes, both i n Europe and i n the northeast U . S., was attributed to acid deposition. Since about two-thirds of the acid of rainfall is F ^ S C ^ and one-third, H N 0 , the focus of atmospheric research in the eastern U . S. continued to be on sulfur species and, secondarily, nitrogen species. Just when acid deposition was becoming the atmospheric research priority in the East, people i n the West were becoming increasingly concerned about visibility de­ gradation, again a problem largely caused by sulfates. Ironically visibility degradation is o f much greater concern i n the West, where visibility is much better than it is i n the East! The reason appears to be that mountains of the West can be seen for distances of 100 k m or more when haze levels are low, whereas the topography o f the East and buildings i n areas where most people live prevent one from seeing more than about 20 k m even i n clear air. Thus, atmospheric research in the eastern U . S. has been dominated by the need for a better understanding of sulfur species, first because of presumed human health effects o f SO9, then because of human health effects of sulfates, and now because of effects of sulfate and acid upon plant and animal life (and, to a lesser extent, on buil­ ding materials, statues, etc.) i n the East, and because of visibility degradation i n the West. The huge increase of population and automobile traffic i n the Los Angeles Basin during W o r l d W a r Π gave rise to a new air pollution phenomenon called "smog", which was found to result from atmospheric reactions of hydrocarbons, C O and nitrogen oxides ( Ν Ο ) during frequent strong inversions in the Basin under influence of abundant sunshine i n southern California. Originally the "photochemical smog" phenomena of southern California was seen as quite a different problem from the SO^-and-fog problem of London and the eastern U . S., i n part because episodes of the latter tended to occur i n F a l l and Winter, whereas smog is usually associated with warm weather and sunshine. Indeed, i n the earlier years, when concentrations of sulfur oxides and particles were much higher in cities, the phenomena may have been different However, under today's conditions, the two sets o f problems clearly are closely related. Huge veils of particulate haze that blanket entire regions of the East 4

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now occur mainly between M a y and October. Improved knowledge of gas-phase kinetics resulting from studies of photochemical smog and of stratospheric problems of supersonic transports and chlorofluorocarbon compounds during the early 1970s has revealed many connections between sulfur chemistry and photochemistry because of the involvement of highly reactive transient species such as hydroxyl radicals ( Ό Η ) , as well as of more stable oxidants produced by photochemistry, e.g., 0 , F ^ O ^ In recent years, most air pollution alerts i n eastern cities have occurred be­ cause o f high levels of oxidants (mainly 0 ) during Summer, when sulfate levels are also very high. 3

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Present Knowledge about A c i d Rain A s demonstrated by papers presented at this Symposium, the increase of our know­ ledge about acid deposition i n recent years has been enormous. The S U R E project (Hidy, This Volume) demonstrated that huge field projects can be conducted with good quality control of samples, analyses and data. K o k , Tanner (This Volume) and others have developed highly sophisticated systems for measuring concentrations of many species, including the very important Η 2 θ , in clouds and clear air with air­ craft. In the area of mechanisms, we know that oxidation by - O H radicals is the dominant gas-phase reaction i n the conversion of S 0 to H S 0 and sulfate (5). Fur­ thermore, we know that oxidation i n solution by F ^ O ^ is rapid and that by 0 and O^ (the latter catalyzed by metal ions or carbon soot) can oe important under some condi­ tions (6; Schwartz, This Volume). Despite these advances, large gaps i n our knowledge still exist. A s demonstrated by many papers i n this symposium, methods for collection and analysis of wet depo­ sition are well established, but understanding o f dry deposition remains poor. The Environmental Protection Agency (EPA) does not plan to do routine direct measure­ ments of dry deposition for the time being. A t most network stations, airborne con­ centrations w i l l be measured and dry deposition rates w i l l be calculated from them (Hicks et al.. This Volume). Some stations w i l l be equipped to do fast response eddy-correlation and airborne concentration measurements for further research on the method and comparison with results from nearby stations that w i l l measure only air­ borne concentrations over longer averaging times (7, £ ) . Although the importance of Ό Η radicals is clear and millions o f dollars have been spent, no reliable, portable i n ­ strument for real-time measurement of their concentrations at low altitudes has been developed. W e know that the reaction of H 0 with S 0 i n cloud droplets is fast, but little is known about the supply o f F ^ O j to cloud droplets, which may limit the amount of sulfate formed. Some of our largest areas of ignorance involve in-cloud processes. Most clouds evaporate, releasing any sulfate formed as sulfate aerosol. However, there is not usually enough airborne sulfate present to account for the sulfate i n rain simply by washout o f sulfate aerosol beneath the clouds (2). Thus, it appears that much of the sulfate brought down by rain must be formed i n the clouds that are causing the rain. There is a lot of "action" i n large storm clouds, e.g., strong updrafts and mixing, which may provide a good environment for extensive chemical reactions. However, the clouds must be supplied with reactants i f sulfate is to be formed, and it's not clear if this happens. Unfortunately, most in-cloud studies have been conducted i n gentle clouds. W e may never be able to study large storm clouds, but investigators of the P R E C P project (PRocessing o f Emissions by Clouds and Precipitation) have devel­ oped methods for studying air flowing into and out of such systems (10, H ) . A recent study by Dickerson etal. (11) demonstrated that air pollutants are rapidly transported to the upper troposphere by thunderstorms. After being transported to such high altitudes, they have much longer residence times and can be transported much greater distances than can pollutants confined to low altitudes. Thus, one of the most serious deficiencies i n our knowledge is the almost complete lack of vertical 2

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concentration profiles of important species, with the exception of data from airplane spirals conducted during intensive study periods of the S U R E project. Fortunately, a decision has been made recently to include vertical profile measurements i n the stu­ dies designed to provide data for model testing (8).

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch001

Can W e Provide Timely Information for Design of Control Strategies? The National A c i d Precipitation Assessment Program ( N A P A P ) is under pressure to provide information needed for development of strategies for control of acid precipi­ tation by about 1989. A n important focal point of N A P A P research is the Regional A c i d Deposition M o d e l ( R A D M ) , a huge Eulerian model requiring input of large amounts of meteorological and source-emissions data. The model includes modules for treatment of transport and mixing of pollutants, chemical reactions i n the gas and liquid phases, in-cloud processes, and wet and dry deposition. The hope is that of making R A D M sufficiently reliable, as shown by tests against appropriate field data, that effects of various control strategies can be assessed by varying the input sourceemissions data and observing predicted changes in airborne concentrations and depo­ sition of various species (8). Some modules of R A D M (including the gas-phase chemistry module discussed by Stockwell, This Symposium) have been constructed, but none has been well tested. There are so many uncertainties, including those dis­ cussed above, that there is considerable doubt i f R A D M can be demonstrated to be reliable in time to be useful for development of control strategies. The recent move of R A D M development from the National Center for Atmospheric Research ( N C A R ) to the State University of N e w Y o r k ( S U N Y ) at Albany w i l l surely slow it down by several months. The U . S . and Canadian agencies dealing with the acid precipitation problem have been meeting to design coordinated field studies that should provide appropriate data for testing R A D M (8). A major component of the cooperative effort w i l l be the Oper­ ational Evaluation Network supported by the electric-power industry via E P R I , an extension of the work previously done via the Utilities Deposition Network. Re­ quests for proposals for many o f the EPA-sponsored portions of the work, including the vertical profile measurements, were released in Jan., 1987. The target date for providing reliable source-receptor relationships by R A D M has unfortunately slipped to 1991. A t present, we cannot say with certainty that reductions i n emissions of S 0 and N O w i l l cause a proportional decrease in deposition of sulfur and nitrogen species. In their thorough review of this problem i n 1983, the "Calvert Committee" of the National Academy of Sciences/National Research Council ( N A S / N R C ) summarized their findings with the carefully worded statement (6): "If we assume that other factors, including meteorology, remain unchanged, the annual average concentration of sulfate in precipitation at a given site should be reduced in proportion to a reduction in S0 and sulfate transported to that site from a source or region of a sources. If ambient concentrations ofNO , nonmethane hydrocarbons, and basic substances (such as ammonia and calcium carbonate) remain unchanged, a reduction in sulfate deposition will result in at least as great a reduction in the deposition of hydrogen ion." However, even this statement was not accepted by some critics, especially those of the Department of Energy laboratories (12), who requested and received major fund­ ing for the P R E C P project designed to investigate "non-linear" dependence of depo­ sition of species upon emissions. Even i f one accepts the conclusion of the N A S / N R C Committee, there is still a question of the distance scale for transport and depo­ sition of sulfur and nitrogen species. F o r example, i f emissions are reduced i n Ohio, w i l l the effects be mostly local, or w i l l they extend appreciably into upper N e w Y o r k State and N e w England? 2

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W h i l e the research community has been trying to provide reliable answers, pressure has been building, both internally and from Canada, for Congress to legis­ late controls. T w o major bills for gradual phase-in of controls were under serious consideration during 1986. If we do not soon provide a scientific basis for decisions, they w i l l probably be made without our involvement. It w i l l surely be a devastating blow to the atmospheric research community, who have worked long and hard i n seeking a good understanding of the problem, i f decisions are made without their final results. Unfortunately, this is the nature of environmental regulations, which must often be made on the basis of incomplete information. If this happens, the priority for determining final answers (and with it, some of the funding) w i l l surely be reduced. Not all would be lost, however, as we might be able to learn a great deal by following changes resulting from implementation of controls on the release of S 0 andNO .

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Are There Alternative Research Strategies? C o u l d the research community and those who fund research devise a strategy for pro­ viding answers that, while not as intellectually satisfying as predictions based on a reliable R A D M , are credible? In my view, we could provide data on sulfur species i n ways that save both money and time. If I were today required to devise a control strategy based on our present knowledge, I would base it on an empirical "engineer­ ing" model published by Fay et al. (13). Their model is a transfer function between the emissions of S 0 by state and the observed deposition contours. The model con­ tains little meteorological data except for an annual average wind vector i n the Ohio River Valley (towards the Northeast) and a parameter for uniform dispersion in all directions obtained from least-squares fitting of the data. The model apportions sul­ fate observed at various stations to S 0 emissions from the various states, but it is obviously useful only for averaging times of one year or more. The model of Fay et al. is crude, but one could do better by using "hybrid recep­ tor models." M o s t conventional models used by E P A and other agencies, including the R A D M , are source-based models i n which source emissions are treated by dis­ persion models, which may also include chemical reactions and deposition, as i n the case of R A D M . Receptor models involve measurement of concentrations of many species and other parameters (e.g., w i n d speeds and directions, mixing heights, etc.) to identify sources of the airborne materials (14). Receptor models have mostiy been used in urban areas to identify sources of airborne particles based on their elemental concentrations (e.g., V are N i from oil-fired power plants, Pb from motor vehicles). Recently, receptor models have begun to be applied to regional and global scale problems. A "hybrid" receptor model is one that combines the receptor model with some aspects o f conventional source-based models. Rahn and Lowenthal (15,16) proposed a set of ratios of concentrations o f six elements (V, M n , Sb, Z n , A s and In) to that of Se on airborne particles as indicators of the origins of air masses from various large regions of North America and other continents. They used the tracer patterns to apportion the areas of origin of particles collected during each of many sampling periods at Underhill, V T and Narragansett, RI, determined the ratio of sulfate concentrations to those of the tracers for various seasons, and used the ratios to assign observed sulfate to the source regions. In disagreement with most current minking, they find that about half of the sulfate i n New England is of fairly local origin. While there has been much criticism of the details o f their method, the basic idea may provide a useful approach to apportion­ ment o f sulfate. Lewis and Stevens (This Volume and 17) have provided a useful framework for hybrid receptor modeling i n which one calculates concentrations of various sulfur species relative to those o f some tracer that is fairly unique to the sulfur source, e.g., Se as a tracer from coal-fired power plants. Equations are written for S 0 conversion 2

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to sulfate and for deposition of gaseous SO^ and particulate sulfate and Se vs. time (or distance, assuming a wind velocity). Kitto and Anderson (This Volume) note that gas-phase Β may be an excellent gas-phase tracer for coal-fired power plants, simula­ ting the deposition features o f S 0 , but not being converted to some other species, as S 0 is. Gordon and Olmez (18) performed calculations of ratios o f B/SOn, S0 /Se, S 0 / S 0 , etc. i n a crude model of air masses moving up the Ohio River Valley and into the Northeast. Their results were i n surprisingly good agreement with measure­ ments by Kitto and Anderson and by Fogg and Rahn (19). However, when Tuncel et al. (This Volume) attempted more detailed fits to absolute concentrations of the sulfur species and Se vs. distance up the Ohio River Valley, they obtained poor agreement with any reasonable choices of parameters. It was impossible to account for the observed amounts of sulfate at a rural station i n Kentucky without greatly overpredicting its concentrations at stations farther up the Valley. Lewis and Stevens (This Volume) gave a preliminary account of the application of the hybrid receptor model to data collected i n the 1983 Deep Creek Lake experiment Samples were col­ lected from several coal-fired power plants upwind o f an ambient site near Deep Creek Lake, M D that is strongly influenced by emissions from those plants. Data on concentrations of gas- and particulate-phase sulfur and particulate Se were used to calculate an S 0 conversion rate of about 6%/hr, which is quite reasonable for A u ­ gust conditions. More data w i l l be available soon from the Deep Creek Lake experi­ ment, which w i l l allow investigators to perform more thorough tests and development of hybrid receptor models. The most sophisticated of the hybrid models is that of Samson et al. (presented by Keeler, This Symposium). They calculate back trajectories for each sampling period of a large data set and assume that sources o f observed species are normally distributed about the trajectory, with a dispersion parameter that increases with dis­ tance from the receptor. B y weighting the backward trajectories by observed con­ centrations during the sampling periods, they build up contours of potential strengths of the observed species i n source areas around the receptor. Their model also has provision for treating dry deposition between the source areas and the receptor and, most important, they have constructed a gridded precipitation data set, which allows them to determine the extent o f rain or snow that falls through specific air masses associated with each sampling period. One can, thus, include assumptions about the fraction o f airborne material removed as a function of precipitation intensity and dura­ tion. This w i l l allow them to include the effects o f precipitation much more directly than i n any other model of which I am aware. They might discover, for example, that the transport o f acid and sulfate precursors from the Ohio River Valley to the North­ east is governed strongly by whether or not any rain falls on the air mass during its transit. One of the most important projects i n progress i n the field o f hybrid receptor modeling is the Allegheny Mountain study by Pierson et al. of Ford Motor Co.(This Volume). Concentrations of many ions, major, minor and trace elements in airborne particles, rain, dew and fog and other parameters were measured at Allegheny M t , P A and Laurel H i l l , 35 k m to the northwest, from 5 to 28 A u g 1983, approximately simultaneously with the Deep Creek Lake studies discussed above. These two huge data sets are now nearly complete and ready for detailed interpretations by the partici­ pants and other researchers in the field. In particular, Keeler is working with the F o r d group to apply the Samson method to the data. In my view, hybrid receptor models are the most likely approach for provide reasonable answers to the sulfate deposition problem within a time that they might be of use in influencing controls that may be imposed on S 0 and N O sources. This does not mean that there is no need for further field studies. The Allegheny M t . and Deep Creek Lake data sets were taken so close together that one would feel much safer i f similar data were available at several other sites, e.g., the three sites of the Ohio River Valley study (20) and one or two sites to the northeast o f Allegheny M t , 2

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say Whiteface M L , N Y and Underhill, V T , which have been well studied i n the past. Furthermore, as noted above, there is still a strong need for vertical concentration profiles. The recent work of Dickerson et al. (11) shows that we cannot develop a reliable model without inclusion of vertical movements of pollutants. A n irony of the acid-deposition problem is that the sulfur problem could be understood quickly and at an affordable cost i f one could release radioactive S 0 from some coal-fired plants along with normal S 0 . Feasibility calculations indicate that this could be done with radiation exposures to the general public well within guidelines, as S decays by weak β emission with an 87-day half life (21). Nuclear detection methods are so sensitive that very little activity needs to be observed to ob­ tain valid measurements. Radioactive sulfur is the perfect tracer of the dispersion, transport, tranformation and deposition of normal sulfur. Samples of sulfur enriched in certain stable isotopes could, i n principle, be used as tracers, but i n the M A T E X (Massive Aerometric Tracer Experiment) Feasibility Study, H i d y et al. (22) found that the cost of stable isotopes would be prohibitive. N o one has very seriously pro­ posed the use of radioactive sulfur because of public fears of exposure. Perhaps with the much greater exposures many people now find they are receiving from natural radioactivity in their houses, they w i l l be less concerned about a small exposure from an experiment. H i d y et al. investigated many schemes for tracing the behavior o f sulfur i n the atmosphere, mainly by releases of non-reactive tracers from S 0 sour­ ces. However, the non-reactive tracers provide information only about dispersion and transport, but not reaction and deposition. The overall uncertainties i n determin­ ing the behavior o f sulfur using only non-reactive tracers are predicted to be so large that H i d y et al. did not recommend that such experiments be initiated at this time. Ondov and K e l l y (23) are developing a promising tracer for particles o f certain sizes based on the use of enriched isotopes of certain rare earth elements. 3 5

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Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch001

3 5

2

What Is the Larger Picture? Those of us involved i n acid deposition research become so deeply involved i n the subject that we may lose sight of the overall problem. Several important points i n this regard were made by D r . J. Laurence K u l p , Director o f N A P A P , i n mformal com­ ments during the Symposium. H e noted the recent emphasis on damage to trees, especially i n the forests of Germany. In general, the damage is worst for species growing near the tops of mountains. A s they are frequently bathed i n fog, some may feel that their problems are caused by direct deposition of fog droplets. However, K u l p noted that stresses o f many kinds increase with altitude until one reaches the timberline, above which no species can survive. Thus, trees at higher elevations are quite vulnerable to many effects, the most frequent of which is drought. Other things such as parasites can affect trees. In regard to air pollution effects, he noted that ozone, at levels frequently encountered today, is known to have deleterious effects on field crops such as soybeans and tobacco. H e pointed out that recent evidence sug­ gests that F L O ^ itself may produce damage to trees. Thus, we must keep i n mind that die acid ancfsulfate we are studying are just one of many possible causes of the dam­ ages that have been ascribed to acid precipitation. A s i n the case of many environ­ mental problems, there may be a synergism between a combination of pollutants such as acid or sulfate and oxidants such as 0 and F L 0 . If it turns out that the damage to trees results largely from oxidants, the detailed studies of atmospheric chemistry related to acid formation as being done under N A P A P w i l l be needed for development of optimal control strategies in addition to the shorter term hybrid approaches to the understanding of sulfur species discussed above. Even i f these more complex studies related to R A D M are not available until the early 1990s, they w i l l be of ultimate value. A s noted by Woodman and Cowling in a recent review of damage to forests (24), it is unlikely that factors responsible for tree damage w i l l be identified sooner than mat. 3

2

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

1.

GORDON

A Decade of Acid Rain Research

9

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch001

Literature Cited 1. Altshuller, A. P. Environ. Sci. Technol. 1980,14, 1337. 2. Report prepared for the Committee on Science and Technology, U. S. House of Representatives, "The Environmental Protection Agency's Research Program with Primary Emphasis on the Community Health and Environmental Surveillance System." U. S. Govt. Printing Office, Washington, D. C., 1976. 3. Weiss, R. E.; Waggoner, A. P.; Charlson, R. J.; Ahlquist, N. C. Science 1977, 195, 979. 4. Cogbill, C. V.; Likens, G. E. Water Resources Res. 1974, 10, 1133. 5. Calvert, J. G.; Stockwell, W. R. Environ. Sci. Technol. 1983, 17, 428A. 6. Committee on Atmospheric Transport and Chemical Transformation in Acid Precipitation, "Acid Deposition: Atmospheric Processes in Eastern North America"; National Academy Press: Washington, D. C., 1983. 7. Hicks, Β. B. Water. Air Soil Pollut 1986, 30, 75. 8. Durham, J.; Dennis, R.; Laulainen, N.; Renne, D.; Pennell, B.; Barchett, R.; Hales, J. "Regional Eulerian Model Field Study and Evaluations: Proposed Management and Technical Approaches," EPA Office of Research and Development, Aug., 1986. 9. Newman, L. E. Presented at the American Chemical Society Nat'l. Meeting, Honolulu, Hawaii, Mar. 1979. 10. Michael, P., ed. "PRECP - The Department of Energy's Program on NonLinearity of Acid Precipitation Processes, Summary of FY1984-1985 Operational Plan," Brookhaven Nat'l. Laboratory Informal Report No. BNL-34842, May, 1984. 11. Dickerson, R. R.; Huffman, G. J.; Luke, W. T.; Nunnermacker, L. J.; Pickering, Κ. E.; Leslie, A. C. D.; Lindsey, C. G.; Slinn, W. G. N.; Kelly, T. J.; Daum, P. H.; Delany, A. C.; Greenberg, J. P.; Zimmerman, P. R.; Boatman, J. F.; Ray, J. D.; Stedman, D. H. Science 1987, 235, 460. 12. Committee on Science and Technology, U. S. House of Representatives, Hearings on "Acid Rain: Implications for Fossil R&D," U. S. Govt. Printing Office, Washington, D. C., 1983. 13. Fay, J. Α.; Golomb, D.; Kumar, S. Atmos. Environ. 1980, 14, 355. 14. Hopke, P. K. "Receptor Modeling in Environmental Chemistry"; WileyInterscience: New York, 1985. 15. Rahn, Κ. Α.; Lowenthal, D. H. Science 1984, 223, 132. 16. Rahn, Κ. Α.; Lowenthal, D. H. Science 1985, 228, 275. 17. Lewis, C. W.; Stevens, R. K. Atmos. Environ. 1985, 19, 917. 18. Gordon, G. E.; Olmez, I. In "Receptor Methods for Source Apportionment"; Pace, T. G., Ed.; APCA: Pittsburgh, PA, 1986; pp. 229-238. 19. Fogg, T. R.; Rahn, K. A. Geophvs. Res. Lett. 1984, 11, 854. 20. Shaw, R. W.; Paur, R. J. Atmos. Environ. 1983, 17, 1431; 2031. 21. Michael, P. Presented at NAPAP Review, Boston, MA, Aug. 1983. 22. Hidy, G. M.; Hansen, D. Α.; Bass, A. "Feasibility and Design of the Massive Aerometric Tracer Experiment (MATEX)," Electric Power Research Institute Report No. EA-4305, 1985. 23. Ondov, J. M.; Kelly, R. Unpublished data, University of Maryland and National Bureau of Standards, 1986. 24. Woodman, J. N.; Cowling, Ε. B. Environ. Sci. Technol. 1987, 21, 120. RECEIVED

March 2, 1987

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Chapter 2

Subcontinental Air Pollution Phenomena G. M. Hidy

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch002

Desert Research Institute, P.O. Box 60220, Reno, NV 89506

This paper discusses aspects of the accumulating body of observations characterizing deposition of airborne acid forming substances. Of p a r t i c u l a r interest are sulfur and nitrogen oxides species. The focus of the observations and interpretation is on subcontinental (or regional) scale phenomena extending over areas of 10 km . Spatial and temporal distributions of ambient sulfur oxide (or sulfate) and nitrogen oxide (or nitrate) concentrations and p r e c i p i t a t i o n chemistry are summarized as they r e f l e c t dry and wet deposition. Comparisons are given between conditions in the eastern and western United States. The importance of v a r i a b i l i t y in deposition exposure, within year and from year-to-year, is outlined. Evidence of linkage between source emissions and receptor measurements is included to complete the discussion. 6

2

f

S i n c e the m i d - 1 9 7 0 s , i n c r e a s i n g i n t e r e s t has emerged i n the e n v i r o n mental consequences o f the l a r g e s c a l e d e p o s i t i o n o f a t m o s p h e r i c contaminants. The d e p o s i t i o n o f a c i d - f o r m i n g c o n s t i t u e n t s , sulfate and n i t r a t e , i s o f p a r t i c u l a r c o n c e r n f o r p o t e n t i a l l y adverse ecological effects. These s p e c i e s d e r i v e from the o x i d a t i o n o f s u l f u r d i o x i d e (S0^) and n i t r o g e n o x i d e s (NO and N0^). Over most i f not a l l of the N o r t h American C o n t i n e n t , e m i s s i o n s o f t h e s e gases are b e l i e v e d to be dominated by man's a c t i v i t i e s , e s p e c i a l l y from f o s s i l f u e l c o m b u s t i o n , and the p r o d u c t i o n or r e f i n i n g o f m e t a l s . The " s c a l e " of exposure f o r d e p o s i t i o n c o v e r s exposure from p o l l u t a n t s i n l a r g e , s u b c o n t i n e n t a l a r e a s , the o r d e r o f 10^ km^. a l t h o u g h r e g i o n a l ambient a i r c o n c e n t r a t i o n s are w e l l below l e v e l s

0097-6156/87/0349-0010S06.00/0 © 1987 American Chemical Society

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

2.

11

Subcontinental Air Pollution Phenomena

HIDY

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch002

mandated by the U.S. C l e a n A i r A c t , d e p o s i t i o n c o n d i t i o n s may s t i l l be s u f f i c i e n t l y l a r g e i n some areas t o cause l o n g term e f f e c t s , p a r t i c u l a r l y i n remote, s u s c e p t i b l e a r e a s . There a r e no known d i r e c t p u b l i c h e a l t h e f f e c t s o f d e p o s i t i o n , and o t h e r r e g i o n a l e f f e c t s a r e h y p o t h e t i c a l , except p o s s i b l y f o r s u r f a c e water q u a l i t y . Thus, t h e r e i s g r e a t c o n c e r n f o r r e a l i z i n g " s i g n i f i c a n t b e n e f i t s " from l a r g e i n c r e a s e s i n i n c r e m e n t a l c o s t s o f p o l l u t i o n c o n t r o l t o address d e p o s i t i o n e x p o s u r e . S p e c i f i c a t i o n s o f " b e n e f i t " from r e d u c t i o n o f d e p o s i t i o n has r e q u i r e d a major investment i n s t u d i e s o f a i r b o r n e a c i d - f o r m i n g s u b s t a n c e s and t h e i r consequences t o a q u a t i c and t e r r e s t r i a l e c o systems. A major p a r t o f these s t u d i e s has r e s u l t e d i n c o n s i d e r a b l y improved knowledge o f the s u l f a t e and n i t r a t e d e p o s i t i o n c o n d i t i o n s i n N o r t h America, as w e l l as knowledge o f the a t m o s p h e r i c p r o c e s s e s a f f e c t i n g these d i s t r i b u t i o n s . In t h i s paper, a s p e c t s o f the c u r r e n t s t a t e o f knowledge i n d e p o s i t i o n p a t t e r n s a r e summarized, w i t h n o t e s about u n r e s o l v e d i s s u e s . D i s t r i b u t i o n of Deposition

Exposure

D e p o s i t i o n o f a t m o s p h e r i c c o n t a m i n a n t s takes p l a c e i n two p r i n c i p a l forms — d r y , by a b s o r p t i o n o f gases o r by p a r t i c l e c o l l e c t i o n at a s u r f a c e , and — wet, by s c a v e n g i n g and d e p o s i t v i a p r e c i p i t a t i o n . A t h i r d form ( " o c c u l t " d e p o s i t i o n ) i s sometimes c i t e d — the c o l l e c t i o n o f m a t e r i a l on s u r f a c e s v i a f o g o r m i s t . Of the t h r e e , the b u l k o f our knowledge c e n t e r s on wet d e p o s i t i o n . A l t h o u g h some ambient c o n c e n t r a t i o n d a t a have been a c q u i r e d , the d a t a a r e v e r y l i m i t e d i n t e m p o r a l and s p a t i a l c o v e r a g e . Data a r e v i r t u a l l y none x i s t e n t i n remote w e s t e r n a r e a s , p a r t i c u l a r l y i n a l p i n e areas where ecosystems a r e b e l i e v e d to be s u s c e p t i b l e . A few e x p l o r a t o r y measurements o f f o g d e p o s i t i o n have been o b t a i n e d a t mountain s i t e s , but no s y s t e m a t i c m o n i t o r i n g has been attempted. The f o g component i s not d i s c u s s e d f u r t h e r h e r e ; a v a i l a b l e o b s e r v a t i o n s suggest t h a t c l o u d s and f o g have h i g h e r c o n c e n t r a t i o n s o f a c i d formers than p r e c i p i t a t i o n ( b u t a p p a r e n t l y c a r r y a r e l a t i v e l y s m a l l p a r t o f the t o t a l burden i n most s i t u a t i o n s ) . E a s t e r n U n i t e d S t a t e s (EUS). The r e g i o n a l l y r e p r e s e n t a t i v e d i s t r i b u t i o n o f ambient s u l f u r o x i d e s and n i t r o g e n o x i d e s over the n o r t h e a s t e r n U n i t e d S t a t e s was f i r s t c h a r a c t e r i z e d i n the l a t e 1970*s from d a t a taken i n the S u l f a t e R e g i o n a l Experiment (SURE). The r e s u l t s have been r e p o r t e d i n s e v e r a l p u b l i c a t i o n s ( 1 ) . Concentra3 t i o n s o f S 0 i n t h e E a s t range from 6-26 yg/m , and p a r t i c u l a t e 3 s u l f a t e c o n c e n t r a t i o n s a r e 4-8 yg/m . The SURE NO and N0~ data 2are u n c e r t a i n i n q u a l i t y compared w i t h the SO^ (SO^ + S0^ ) d a t a 9

1

X

because o f measurement a m b i g u i t i e s .

Estimated

average

ambient

3 nitrate believed

concentrations t o be n i t r i c

range from 0.3-0.5 yg/m , much o f which i s a c i d vapor.

NO

concentration

distributions

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

12

T H E CHEMISTRY OF ACID RAIN

were l e s s w e l l c h a r a c t e r i z e d , but range, m a i n l y as N0^.

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch002

E v i d e n c e shows t h a t the

are

ambient

reported

i n the

concentrations

7-20

yg/m

o f SO

and NO χ χ i n the EUS are l i n k e d w i t h b r o a d areas o f h i g h e m i s s i o n d e n s i t y a s s o c i a t e d w i t h m e t r o p o l i t a n areas and heavy i n d u s t r i a l i z a t i o n . Comparison between r e g i o n a l l y r e p r e s e n t a t i v e c o n c e n t r a t i o n s i n w o r l d remote a r e a s , and those o b s e r v e d i n the EUS show e l e v a t i o n s o f a f a c t o r o f ten i n mean c o n c e n t r a t i o n s , w i t h s h o r t term average con­ c e n t r a t i o n s even h i g h e r than b a s e l i n e c o n d i t i o n s . E l e v a t e d c o n c e n t r a t i o n s o f s u l f a t e and n i t r a t e a s s o c i a t e d w i t h zones o f h i g h e m i s s i o n d e n s i t y are a l s o found i n p r e c i p i t a t i o n . The g e o g r a p h i c a l c o n c e n t r a t i o n d i s t r i b u t i o n s i n p r e c i p i t a t i o n are s i m i l a r to those found f o r a i r b o r n e s u l f a t e (SO and NO emission χ χ d i s t r i b u t i o n s are s i m i l a r i n the EUS). A l t h o u g h d i r e c t measurements are e x t r e m e l y l i m i t e d , the dry component of d e p o s i t i o n can be e s t i m a t e d q u a l i t a t i v e l y from d a t a n o t i n g t h a t the d e p o s i t i o n r a t e i s the product o f a d e p o s i t i o n v e l o c i t y and ambient c o n c e n t r a t i o n o b s e r v a t i o n s at ground l e v e l . F o r example, t a k i n g s u i t a b l e v a l u e s o f d e p o s i t i o n v e l o c i t y , l i s t e d f o r example i n T a b l e I I , and d a t a from the SURE ( 2 ) , e s t i m a t e s of the annual average dry d e p o s i t i o n r a t e f o r s u l f u r are the o r d e r o f 6-60 kgS/ha-yr i n the E a s t . T h i s i s compared w i t h v a l u e s of 4-16 kgS/ha-yr i n wet d e p o s i t i o n . A l t h o u g h dry d e p o s i t i o n l e v e l s o f Ν 0 have not been r e p o r t e d , they would be lower than s u l f u r , s i n c e the ambient c o n c e n t r a t i o n s are s i m i l a r but the d e p o s i t i o n v e l o c i t y i s smaller. Wet d e p o s i t i o n of n i t r a t e based on a v a i l a b l e d a t a i n 1980 i s 2-7 kgN/ha-yr. Comparison between d e p o s i t i o n components f o r c o n d i t i o n s i n EUS i n d i c a t e s t h a t the dry component w i l l s u b s t a n t i a l l y exceed the wet component near s o u r c e s . T h i s r e s u l t s from ambient c o n c e n t r a t i o n s f o r SO^ average about 10-20 ppb, and N0^ c o n c e n t r a t i o n exceed 10 ppb χ

near s o u r c e s (

m ο se m g oc »-} 2?

H SC

2.

HIDY

Subcontinental Air Pollution Phenomena

< S" 5 g £ £

80 70 60 50 40 30 g 20 S "0 8

I

ο

^

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch002

|i|

SC PF ΚΑ ΑΙ BO WS WH IT PS CV IL

35 4.30 Ζ 225 0 σ-

φ

NO;

il*

I

S 15 ëUJ .0 m

•à · r*i r*i f*l n f*l Ο 0 SC PF KA Al BD WS WH IT PS CV IL u SQ

' l i f t n ή FI

SC PF KA Al BO WS WH IT PS CV IL REMOTE AREAS EASTERN U.S.

F i g u r e 1. Comparison between p r e c i p i t a t i o n c o n c e n t r a t i o n s i n w o r l d remote a r e a s ( l e f t ) , the e a s t e r n U.S. ( r i g h t ) and the w e s t e r n s t a t e s (WS). The range shown f o r the f i r s t two c a t e g o r i e s i s the s t a n d a r d d e v i a t i o n o f a n n u a l mean v a l u e s . For the w e s t e r n s t a t e s , the range i s the v a l u e s f o r d i f f e r e n t s i t e s o b s e r v e d between 1981 and 1984. (Data f o r the f i r s t two from G a l l o w a y e t a l , 3; f o r t h e w e s t e r n s t a t e s , H i d y & Young, E n v i r o n . Res. & T e c h . , u n p u b l . r e p o r t ) ( D a t a r e p r o d u c e d w i t h p e r m i s s i o n from R e f . 3. C o p y r i g h t 1984 AAAS).

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

15

16

T H E CHEMISTRY OF ACID RAIN

A l a s k a ( P F ) , K a t h e r i n e , A u s t r a l i a (ΚΑ) , Amsterdam I s l a n d , I n d i a n Ocean, ( A I ) , and Bermuda, A t l a n t i c Ocean (BD). The e a s t e r n U.S. s i t e s i n c l u d e M u l t i s t a t e A t m o s p h e r i c Power P r o d u c t i o n P o l l u t i o n Study (MAP3S) s i t e s at W h i t e f a c e M o u n t a i n , NY (WH) I t h a c a , NY ( I T ) , P e n n s y l v a n i a S t a t e U n i v e r s i t y ( P S ) , C h a r l o t t e s v i l l e , VA (CV) and Urbana, IL ( I L ) . The w e s t e r n s t a t e s are N a t i o n a l A t m o s p h e r i c D e p o s i t i o n Program (NADP) s i t e s w i t h a c o n t i n u o u s r e c o r d between 1981-1984 ( i n C o l o r a d o , C a l i f o r n i a , Washington, Oregon and A r i z o n a ) . The

comparisons

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch002

equivalent

+

suggests that

[H ]

i n the WUS

to g l o b a l remote c o n d i t i o n s , but

precipitation is 2[SO^ ] and [NO^ ] are

i n t e r m e d i a t e between remote and EUS " p o l l u t e d " c o n d i t i o n s . In b o t h the E a s t and the West, p r e c i p i t a t i o n s u l f a t e tends to be l a r g e r than n i t r a t e c o n c e n t r a t i o n s , except near l a r g e s o u r c e s of NO i n the West, χ An i n t e r e s t i n g f e a t u r e o f WUS p r e c i p i t a t i o n i s t h a t the annual average s u l f a t e c o n c e n t r a t i o n s are w e l l c o r r e l a t e d w i t h c a l c i u m + 2(Figure 2). [H ] i s much l e s s w e l l c o r r e l a t e d w i t h e i t h e r [SO^ ] or

[NO^

ively.

] —

correlation

coefficient

This

is quite different

( r ) = 0.577 and

from EUS

0.546

respect­

c o n d i t i o n s where the

anions

+

are w e l l c o r r e l a t e d w i t h [ H ] . The r e a s o n f o r the s t r o n g a s s o 2+ = c i a t i o n between [Ca ] and [SO^ ] i n w e s t e r n p r e c i p i t a t i o n may be a s s o c i a t e d w i t h s c a v e n g i n g o f gypsum r i c h s o i l d u s t , or may be r e l a t e d to r e a c t i o n s of scavenged l i m e s t o n e dust and s u l f u r i c a c i d . F i g u r e 2 suggests a range f o r the i n f l u e n c e of s o i l d u s t , and a v a l u e f o r a s u l f a t e background. A l i n e o f s l o p e u n i t y can be drawn t h r o u g h the d a t a

p o i n t s at SO^

This

concentrations

i s s t o i c h i o m e t r i c a l l y c o n s i s t e n t with 2+ . 2z e r o Ca c o n c e n t r a t i o n i s 5 y e q / l SO^ .

with

1:1

slope

line

suggesting

i n f l u e n c e d component

(excess

than 20

The

This value

a g l o b a l p r e c i p i t a t i o n background e x p e c t e d 2shown i n F i g u r e 1. Above 20 yeq/1 SO^ , there the

less

CaSO,.

peq/l.

i n t e r c e p t at . is consistent

from remote

sites

i s d e v i a t i o n from

the i n f l u e n c e of a n o n - s o i l dust 2SO^ ). T h i s component c o u l d be

i d e n t i f i e d w i t h u n n e u t r a l i z e d a c i d i c a i r p o l l u t i o n o v e r the WUS. From F i g u r e 1, the average o f the " e x c e s s " s u l f a t e over the West would be about 5 y e q / l , much s m a l l e r than l e v e l s found i n the EUS. Measurements of ambient c o n c e n t r a t i o n s of s p e c i e s i n remote l o c a t i o n s o f the West are v e r y l i m i t e d . However, the few t h a t e x i s t show the western r u r a l l e v e l s much lower than i n the E a s t . Typical examples are l i s t e d i n T a b l e I I .

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

2.

HIDY

Table I I .

Deposition Velocity (cm/sec)

1 ppb

2

S0

E s t i m a t e s o f Annual Dry D e p o s i t i o n F o r R u r a l / B a c k g r o u n d Areas i n the West ( A f t e r H i d y & Young, E n v i r o n . , Res. & Tech., unpublished report)

Typical Concentration*

Species S0

2 4

17

Subcontinental Air Pollution Phenomena

~

2

yg

/m

E s t i m a t e d Dry Deposition Rate** (kg/ha-yr)

0.5 3

2

0.2

0^3

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch002

Total N0

1 ppb

2

HN0

0.5

3

N0 "

0.5

3

ppb ug/m

3

2.3

0.1

0.2

1.0

0.9 0Λ

0.2 Total

**As s u l f u r & These v a l u e s

nitrogen are used w i t h d e p o s i t i o n v e l o c i t i e s

o f w e s t e r n dry ively

are

1.1

deposition.

Wet

0.8-4.6 kgS/ha-yr. and

deposition

to g i v e 2-

of SO^

0.7-2.3 kgN/ha-yr.

and

an NO^

estimate respect­

These r a t e s

are

g e n e r a l l y w e l l below the l e v e l s i n the EUS. In the West, dry d e p o s i t i o n i s a s i m i l a r l e v e l as wet deposi­ t i o n f o r S and Ν i n many a r e a s , except near s o u r c e s and i n a r i d d e s e r t c o n d i t i o n s where wet d e p o s i t i o n i s n e g l i g i b l e . S i n c e measure­ ments o f wet d e p o s i t i o n a r e t a k e n i n v a l l e y s w i t h low p r e c i p i t a t i o n , they u n d e r e s t i m a t e the wet component somewhat f o r a l p i n e ( e c o l o g i ­ c a l l y susceptible) conditions. The a l p i n e and s u b a l p i n e a r e a s i n the West have much h i g h e r a n n u a l p r e c i p i t a t i o n r a t e s than lower elevations. Variability C h a r a c t e r i z a t i o n of v a r i a b i l i t y i n d e p o s i t i o n i s important f o r bounding u n c e r t a i n t i e s i n exposure l e v e l s . A l s o t h i s a s p e c t o f depo­ s i t i o n i s c r u c i a l t o d e s c r i b i n g the " p r e d i c t a b i l i t y " o f s o u r c e receptor r e l a t i o n s h i p s (SRRs)(4). With a c q u i s i t i o n o f o b s e r v a t i o n s over a p e r i o d o f y e a r s , the v a r i a b i l i t y i n d e p o s i t i o n r a t e s has become b e t t e r known. L i k e the r e s u l t of a l l atmospheric processes, d e p o s i t i o n i s h i g h l y v a r i a b l e at a g i v e n s i t e and between s i t e s ; and w i t h i n y e a r , or from y e a r - t o year. V a r i a b i l i t y i n o b s e r v a t i o n s d e r i v e s from the measurement p r o c e s s i t s e l f , changes i n i n p u t ( e m i s s i o n s ) , and the " s t o c h a s t i c " c h a r a c t e r of a t m o s p h e r i c p r o c e s s e s i n f l u e n c i n g e m i t t e d m a t e r i a l b e f o r e i t i s r e t u r n e d to the e a r t h . The u n c e r t a i n t i e s i n the measurement p r o c e s s f o r p r e c i p i t a t i o n have been d e f i n e d

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

THE CHEMISTRY OF ACID RAIN

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch002

18

quantitatively. F o r wet d e p o s i t i o n , s a m p l i n g i s i d e n t i f i e d as the major a r e a o f measurement u n c e r t a i n t y , e s p e c i a l l y f o r snow. T y p i c a l t o t a l v a r i a b i l i t y i n concentration of species i n bulk samples i s shown f o r s u l f a t e i n F i g u r e 3. These d a t a c o n t a i n v a r i a t i o n s t h a t i n c l u d e a measurement component and the i n f l u e n c e o f a t m o s p h e r i c changes. The d a t a are r e p o r t e d f o r monthly samples i n the U.S. G e o l o g i c a l Survey (USGS) network of New York S t a t e . The d a t a r e p r e s e n t one of the l o n g e s t r e c o r d s a v a i l a b l e , from 1965 to 1984. The y e a r - t o - y e a r changes at the s i t e , show a s m a l l , s y s t e m a t i c downward d r i f t i n annual median s u l f a t e c o n c e n t r a t i o n on which i s superimposed a monthly v a r i a b l e component. The normal range of monthly ( w i t h i n y e a r ) v a r i a t i o n i s shown by the s t a n d a r d d e v i a t i o n , and the range o f v a l u e s i n a y e a r are a l s o shown. Two o u t l i e r p o i n t s are i n c l u d e d which cannot be r a t i o n a l i z e d by measurement u n c e r t a i n t y , but are out o f the s t a t i s t i c a l l y e x p e c t e d r a n g e . T h i s r e c o r d i l l u s t r a t e s w e l l t h a t s e v e r a l y e a r s of d a t a are needed to e s t a b l i s h a mean c o n d i t i o n , and p r o v i d e a b a s i s f o r d e s c r i b i n g "natural" variability. V a r i a b i l i t y i n dry d e p o s i t i o n i s p a r t l y r e f l e c t e d i n ambient c o n c e n t r a t i o n s , which v a r y o v e r a much wider range than e s t i m a t e s o f emissions. T h i s range i s a s c r i b e d to m e t e o r o l o g i c a l i n f l u e n c e ( 1 ) . A l a r g e and i l l - d e f i n e d v a r i a t i o n i n dry d e p o s i t i o n stems from surface conditions. Key to change i s the m o i s t u r e on a s u r f a c e as w e l l as b i o l o g i c a l a s s i m i l a t i o n c a p a b i l i t y ; both change d i u r n a l l y and s e a s o n a l l y ( 2 ) . I n t e r s i t e v a r i a b i l i t y has been s t u d i e d f o r both ambient c o n c e n t r a t i o n d a t a ( 1 ) , and f o r wet d e p o s i t i o n ( 5 ) . I n t e r s i t e 2c o r r e l a t i o n s f o r ambient SO^ and SO^ c o n c e n t r a t i o n s i n the EUS show d r a m a t i c d i f f e r e n c e s i n s p a t i a l

scale.

SO^

concentrations

have

h i g h l y l o c a l i z e d p a t t e r n s of c o r r e l a t i o n t h a t e x c l u d e a r e g i o n a l character. In c o n t r a s t , a i r b o r n e s u l f a t e c o r r e l a t i o n s are h i g h l y regional in character. S p a t i a l v a r i a b i l i t y i n s u l f a t e i s dominated by two to t h r e e components t h a t can be i d e n t i f i e d w i t h p r e v a i l i n g , persistent meteorological conditions (1). The s p a t i a l s c a l e of i n t e r s i t e c o r r e l a t i o n d i f f e r s somewhat w i t h l o c a t i o n . However, the average p a t t e r n f o r wet s u l f a t e and n i t r a t e c o r r e l a t i o n i s shown w i t h s p a c i n g of s t a t i o n s i n F i g u r e 4. The graphs r e p r e s e n t an a g g l o m e r a t i o n o f c o r r e l a t i o n d a t a between 1981 and 1984 f o r more than 20 EUS s i t e s . The d i s t a n c e over which c o r r e l a t i o n o c c u r s f o r s u l f a t e extends almost to 2000 km, but c o r r e l a t i o n d e c r e a s e s r a p i d l y below l e s s than 0.5 w i t h i n 100 km. A s i m i l a r p a t t e r n i s found f o r n i t r a t e , except the s t a t i o n s p a c i n g r e f l e c t i n g no c o r r e l a t i o n i s l e s s than f o r s u l f a t e ( a p p r o x i m a t e l y 1200 km). The i n t e r s i t e c o r r e l a t i o n s i l l u s t r a t e w e l l the r e g i o n a l c h a r a c t e r of s u l f a t e and n i t r a t e d e p o s i t i o n i n the EUS. Circumstant i a l e v i d e n c e f o r a s i m i l a r s p a t i a l s c a l e o f i n f l u e n c e a l s o has been r e p o r t e d f o r the West ( 6 ) . V a r i a b i l i t y i n d e p o s i t i o n p a t t e r n s may be a s s o c i a t e d w i t h c e r t a i n dominant m e t e o r o l o g i c a l p a t t e r n s ( 1 ) . As noted above, ambient c o n d i t i o n s can be c l a s s i f i e d m e t e o r o l o g i c a l l y . Some e v i dence f o r such a c l a s s i f i c a t i o n a l s o e x i s t s f o r wet d e p o s i t i o n ( 5 ) .

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch002

2.

19

Subcontinental Air Pollution Phenomena

HIDY

30 • 26 • 26 24 · 22 · 20 H 16 · 16 14 · 12 10 8 6420-

r = Ν ζ

0.922 69

Sulfate Concentration (ueq/l) 1981

+

1982

Ο

1983

F i g u r e 2. C o r r e l a t i o n between c a l c i u m and s u l f a t e c o n c e n t r a t i o n i n western p r e c i p i t a t i o n . Data f o r 1981-1984 - a n n u a l a v e r a g e s o f NADP s t a t i o n s . (From H i d y & Young, E n v i r o n . Res. & Tech., unpubl. report.)

15.0 12.5

10.0

ε

7.5

Lu 2

5.0

2.5

0

-25 65

I 70

I 75

i 80

I

WATER YEAR BEGINNING

F i g u r e 3. Trend i n a n n u a l median v a l u e s of s u l f a t e c o n c e n t r a t i o n i n b u l k d e p o s i t i o n samples a t H i n c k l e y , NY ( c r o s s e s ) . V a r i a b i l ­ i t y i s a l s o i n d i c a t e d i n the b o x p l o t by the s t a n d a r d d e v i a t i o n s (-) and the range ( v e r t i c a l b a r s ) and o u t l i e r s (0, ·)(Reproduced w i t h p e r m i s s i o n from Ref. 4. C o p y r i g h t 1984 APCA).

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

THE CHEMISTRY OF ACID RAIN

20

0.5

SULFATE 1980 0.4

0.3 -\

0.2

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch002

0.1

-0.1

1

'

1

I 800

400

I ' 1200

ι

'

-ι—ι—ι—ι—r-

I ' 1600

2000

2400

1NTERSITE DISTANCE (km)

-1 0

ι

ι

ι 400

ι

ι

ι

ι 800

ι

ι

ι

ι

ι

1200

ι

ι

ι

-

π 1 ι γ~~ι I

1600

2000

r~ 2400

INTERSITE DISTANCE (km)

F i g u r e 4. S c a l e o f r e g i o n a l phenomena i n p r e c i p i t a t i o n s u l f a t e and n i t r a t e a s i n d i c a t e d by i n t e r s i t e c o r r e l a t i o n s . Data a r e an average o f s e v e r a l s i t e s i n EUS. (Reproduced w i t h p e r m i s s i o n from R e f . 5. C o p y r i g h t 1985 E l e c t r i c Power R e s e a r c h I n s t . ) .

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

2.

HIDY

21

Subcontinental Air Pollution Phenomena

Source-Receptor

Relationships.

U l t i m a t e l y the m i t i g a t i o n t o the e n v i r o n m e n t a l e f f e c t s o f a c i d depo­ s i t i o n r e q u i r e s d e c r e a s e i n exposure through e m i s s i o n r e d u c t i o n . There has been c o n s i d e r a b l e debate about how much and where r e d u c t i o n s can be a c h i e v e d from p r a c t i c a l p l a n n i n g f o r SO^ and Ν 0 χ

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch002

e m i s s i o n r e d u c t i o n . An important a s p e c t o f the p r e d i c t a b i l i t y i s s u e l i e s i n the u n c e r t a i n t i e s i n the n o n - l i n e a r c h a r a c t e r o f a t m o s p h e r i c processes a f f e c t i n g d e p o s i t i o n rates ( 2 ) . Perhaps the b e s t e v i d e n c e f o r e s t a b l i s h i n g a d i r e c t l y p r o p o r ­ t i o n a l r e l a t i o n s h i p between e m i s s i o n change i s comparison between long term t r e n d s l i k e t h o s e shown i n F i g u r e 3 w i t h e m i s s i o n changes over the same time p e r i o d . Such a d i r e c t r e l a t i o n i s suggested i n sulfate

(and p o s s i b l y NO^

) d a t a i n b u l k d e p o s i t i o n taken

a t Hubbard

Brook, NH ( e . g . , F i g u r e 5 ) . An average d e c r e a s e i n s u l f a t e o f about 2%/yr between 1970 and 1982 ( n o t shown i n F i g u r e 5) i s e s s e n t i a l l y the same as t h a t e s t i m a t e d from d e c r e a s e i n r e g i o n w i d e SO^ e m i s s i o n s (4,7). With the d i s c u s s i o n o f s p a t i a l c o r r e l a t i o n above, i t i s l o g i c a l to expect t h a t any r e l a t i o n between e m i s s i o n s and r e g i o n a l l y r e p r e ­ s e n t a t i v e d e p o s i t i o n measurements s h o u l d be c o n s i s t e n t f o r s e v e r a l sites. To t e s t t h i s , t h e Hubbard Brook r e s u l t s were compared w i t h l i m i t e d d a t a from the USGS b u l k d e p o s i t i o n network, p r i m a r i l y l o c a t e d i n New Y o r k S t a t e ( 4 ) . The s t a t i o n s s e l e c t e d a r e r u r a l and are w i t h i n 550 km o f one a n o t h e r . Q u a l i t a t i v e comparison o f t r e n d i n d i c a t o r s i n t h e d a t a a r e summarized i n T a b l e I I I . Table I I I .

Parameter

3

Summary o f Apparent T r e n d s i n Annual Median P r e c i p i t a t i o n C h e m i s t r y Data from the USGS S i t e s and Hubbard Brook (1965-1980) S i t e s (Reproduced w i t h p e r m i s s i o n from Ref. 4, C o p y r i g h t 1984 APCA)

Hubbard Brook Precipitation +

Hinckley Canton NY NY 0 0 0

2

SO, " 4_ N0 " 3

NH, 4 pH

+

Trend

Mays P t . NY

Salamanca NY 0

Athens PA 0

0

0

0+

+0

+

0

+

0

+

0

+

+

+

0

+

-

0

+

indicators

-

0

0

a r e : (+) upward, (-) downward, and (0) no t r e n d .

These i n d i c a t o r s a r e based on e s t i m a t e d s i g n i f i c a n t change by s t a t i s t i c a l t e s t i n g ( 4 ) . The summary i n d i c a t e s t h a t the t r e n d s a r e not c o n s i s t e n t f o r s u l f a t e , o r f o r o t h e r c o n s t i t u e n t s . S p a t i a l and temporal w e i g h t i n g a l s o have been used on the USGS d a t a t o o b t a i n y e a r l y averaged s u l f a t e d e p o s i t i o n f o r New Y o r k

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch002

T H E CHEMISTRY OF ACID RAIN

1964-65

66-67

68-69

70-71

72-73

74-75

76-77

F i g u r e 5. Comparison between EUS S O 2 and ΝΟχ e m i s s i o n s and a n n u a l w e i g h t e d c o n c e n t r a t i o n s o f SO^-, N O 3 , and NH^ i n b u l k d e p o s i t i o n a t the Hubbard Brook E x p e r i m e n t a l F o r e s t from 1964 to 1977. L i n e t h r o u g h e m i s s i o n s i s drawn t h r o u g h e s t i m a t e s each f i v e y e a r p e r i o d from 1965. (From H i d y , 8 ) .

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

2.

HIDY

23

Subcontinental Air Pollution Phenomena

State. B i l o n i k ' s r e s u l t s (9) i n d i c a t e a maximum i n s u l f a t e d e p o s i ­ t i o n i n the 1971-1973 p e r i o d as compared w i t h an apparent EUS SO^ e m i s s i o n s maximum between 1970 and 1975. Since d e p o s i t i o n r a t e l s a d i m e n s i o n a l l y c o n s i s t e n t parameter w i t h e m i s s i o n r a t e , these r e s u l t s q u a l i t a t i v e l y tend to s u p p o r t an SO emission-deposition r e l a t i o n ­ s h i p f o r the EUS. 2The l a c k of s p a t i a l c o n s i s t e n c y i n r e l a t i n g SO^ concentration

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch002

to SO^

emissions

may

be

the r e s u l t

of d i f f e r e n c e s

i n the

influence

o f s o u r c e s near a g i v e n s i t e , t o an i n a d e q u a t e q u a n t i t a t i v e d a t a base, or to m e t e o r o l o g i c a l d i f f e r e n c e s i n exposure. A t e s t of the f i r s t f a c t o r was attempted, c a l c u l a t i n g the e f f e c t o f r e g i o n a l l y d i f f e r e n t e m i s s i o n changes on d i f f e r e n t r e c e p t o r s , a c c o u n t i n g f o r r e d u c t i o n i n source e f f e c t w i t h d i s t a n c e from the UMACID model ( 5 ) . The r e s u l t s o f the c a l c u l a t i o n are g i v e n i n F i g u r e 6. The r e c e p t o r l o c a t i o n s are western New Y o r k S t a t e (WNY); N o r t h C e n t r a l P e n n s y l v a n i a (NCPA); Muskoka, Ont.; W h i t e f a c e M o u n t a i n , NY (WFM); and n o r t h e a s t e r n New Hampshire (VT-NH). There are c l e a r l y geo­ g r a p h i c a l d i f f e r e n c e s i n e x p e c t e d changes w i t h SO^ e m i s s i o n s a f t e r 1965, and the s u l f a t e d e p o s i t i o n change s h o u l d not n e c e s s a r i l y be l i n e a r s i n c e the apparent e m i s s i o n s were not c h a n g i n g l i n e a r l y over the p e r i o d . N e v e r t h e l e s s , a down t r e n d i n s u l f a t e s h o u l d have been o b s e r v e d c o n s i s t e n t l y i f m e t e o r o l o g i c a l v a r i a b i l i t y was s i m i l a r from site-to-site. These r e s u l t s are ambiguous. The a m b i g u i t y d e r i v e s i n p a r t from s u b r e g i o n a l d i f f e r e n c e s i n e m i s s i o n change over the EUS. The Hubbard Brook d a t a a r e c o n s i d e r e d h i g h e r q u a l i t y than the USGS s e t ( 7 ) . Thus, the Hubbard Brook d a t a are r e l i e d upon f o r supporting a linear source-receptor r e l a t i o n s h i p . A test tion

sulfate

for proportionality a l s o has

between SO^

been attempted

e m i s s i o n s have dominated SO^

emissions

f o r the West

emissions

i n the WUS.

(6).

and

precipita­

Smelter

These

emissions

changed by more than annual

averaged

50% over the 1980-1984 p e r i o d . A n a l y s i s o f 2[SO^ ] d a t a from NADP f o r s e v e r a l w e s t e r n s i t e s

(mostly i n Colorado) provided c i r c u m s t a n t i a l evidence f o r a propor­ t i o n a l SRR. These r e s u l t s were c h a l l e n g e d by o t h e r s (10, 11). However, r e a n a l y s i s of the same d a t a f o r monthly v a r i a t i o n appears to g i v e a s t r o n g e r case f o r p r o p o r t i o n a l i t y (Oppenheimer, Μ., E p s t e i n , D., N a t u r e , i n p r e s s ) over d i s t a n c e s o f i n f l u e n c e beyond 1000 km. The new a n a l y s i s a l s o p l a c e s i n p e r s p e c t i v e w i t h i n y e a r ( s e a s o n a l ) , and y e a r - t o - y e a r v a r i a b i l i t y . The r e a s o n f o r the s t r e n g t h o f p r o p o r t i o n a l i t y r e l a t i o n s h i p i n the w e s t e r n d a t a r e l a t i v e to the E a s t i s not a p p a r e n t ; however, i t may be r e l a t e d to the s i z e o f the e m i s s i o n change " s i g n a l " i n the m e t e o r o l o g i c a l " n o i s e " compared w i t h h i s t o r i c c o n d i t i o n s i n the East. In e s t i m a t i n g the r e l i a b i l i t y o f t h e o r e t i c a l p r e d i c t i o n s , i t i s i m p o r t a n t to take i n t o account the y e a r - t o - y e a r v a r i a b i l i t y i n SRRs e s t i m a t e d from m e t e o r o l o g i c a l t r a n s p o r t . The p r e d i c t i o n - r e l i a b i l i t y q u e s t i o n i s c e n t r a l to c o n s t r u c t i n g a c o s t e f f e c t i v e p r a c t i c a l

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

THE CHEMISTRY OF ACID RAIN

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch002

24

Ol 1950

1

1

1

I

I

I

1955

1960

1965

1970

1975

1980

YEAR

F i g u r e 6. E s t i m a t e d c o n t r i b u t i o n to wet d e p o s i t i o n o f s u l f a t e from e m i s s i o n s i n the e a s t e r n U.S. and s o u t h e a s t e r n Canada based on 1978 m e t e o r o l o g y . The wet d e p o s i t i o n i n d e x i s the d e p o s i t i o n r a t e i f m e t e o r o l o g y were the same i n each y e a r . The p e r c e n t a g e change shown on each l i n e c o r r e s p o n d s to the c a l c u l a t e d r e d u c t i o n i n wet d e p o s i t i o n from e m i s s i o n change, w i t h m e t e o r o l o g i c a l c o n d i t i o n s assumed to be u n i f o r m from y e a r to year. The e x p e c t e d r a n g e of u n c e r t a i n t y i n e s t i m a t e o f wet d e p o s i t i o n u s i n g a c t u a l p r e c i p i t a t i o n r a t h e r than 1978 l e v e l s a r e i n d i c a t e d by squares and v e r t i c a l b a r s . (Reproduced w i t h p e r m i s s i o n from Ref. 4. C o p y r i g h t 1984 APCA).

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch002

2.

HIDY

Subcontinental Air Pollution Phenomena

25

design f o r s e l e c t i v e emission c o n t r o l improving d e p o s i t i o n i n d i s ­ tant, s u s c e p t i b l e areas. A c t u a l o b s e r v a t i o n a l d a t a are v e r y l i m i t e d through which t e s t s of model v a l i d i t y and performance can be made. Data t o t e s t the s e n s i t i v i t y o f such c a l c u l a t i o n s are even l e s s available. An e x p l o r a t o r y a n a l y s i s o f the range o f v a r i a b i l i t y t h a t may be expected was attempted by Samson et a l (see H i d y e t a l , 5, p. I I - 2 98). T h e i r c a l c u l a t i o n s used a c t u a l m e t e o r o l o g i c a l d a t a t o e s t i m a t e a geographical d i s t r i b u t i o n of " n a t u r a l p o t e n t i a l " f o r emissions from a source a r e a to r e a c h a r e c e p t o r a r e a . I f wind c o n d i t i o n s e x i s t such t h a t wind blows a l l the time from the source over the r e c e p t o r , f o r example, t h i s p o t e n t i a l would be u n i t y . C a l c u l a t i o n s of " n a t u r a l p o t e n t i a l " were made u s i n g m e t e o r o l o g i c a l d a t a f o r several years. The y e a r - t o - y e a r v a r i a t i o n i n n a t u r a l p o t e n t i a l d i s t r i b u t i o n i s shown i n F i g u r e 7 f o r the EUS. The example c o n c e r n s the Upper Ohio R i v e r V a l l e y source complex. Near to the source a r e a and downwind ( e a s t w a r d ) , t h e r e i s a 20% v a r i a b i l i t y i n n a t u r a l p o t e n t i a l , w h i l e at g r e a t e r d i s t a n c e s and upwind (westward), the c o e f f i c i e n t o f v a r i a t i o n i n p o t e n t i a l i n c r e a s e s . These c a l c u l a t i o n s g i v e at l e a s t a q u a l i t a t i v e p i c t u r e o f the r e l i a b i l i t y i n a i r t r a n s ­ p o r t c o n d i t i o n s i n f l u e n c i n g SRRs, p i c k i n g a s i n g l e t e s t y e a r . If the wind f i e l d and m i x i n g c o n d i t i o n s were the o n l y source o f v a r i a b i l i t y , the p r e d i c t i o n s c o u l d be r e a s o n a b l y r e l i a b l e i n c e r t a i n key a r e a s . However, o t h e r v a r i a t i o n such as a i r c h e m i s t r y , c l o u d s c a v e n g i n g and p r e c i p i t a t i o n are a d d i t i o n a l f a c t o r s unaccounted f o r i n such c a l c u l a t i o n s . A number of workers have become concerned about such q u e s t i o n s so t h a t r e s e a r c h i n u n c e r t a i n t i e s has expanded. U n f o r t u n a t e l y , the o b s e r v a t i o n s d e s c r i b i n g c h e m i c a l v a r i a b i l i t y i n both dry and wet d e p o s i t i o n are v e r y l i m i t e d f o r d i r e c t s t u d y . There i s need f o r a major investment i n f i e l d programs to a c q u i r e such d a t a . Summary. T h i s paper has summarized c e r t a i n f e a t u r e s o f o b s e r v a t i o n s c h a r a c t e r ­ i z i n g dry and wet d e p o s i t i o n o f a i r b o r n e a c i d f o r m i n g s p e c i e s , i n p a r t i c u l a r , s u l f a t e and n i t r a t e . The r e g i o n a l or s u b c o n t i n e n t a l c h a r a c t e r o f d e p o s i t i o n d i s t r i b u t i o n s over the U n i t e d S t a t e s i s noted. Example d a t a are c i t e d showing d i f f e r e n c e s i n c h a r a c t e r i s t i c d e p o s i t i o n between the West and the E a s t . The West e x p e r i e n c e s s u l f a t e and n i t r a t e d e p o s i t i o n w e l l below t h a t found i n the E a s t , but l a r g e r than g l o b a l remote s i t e s are s u g g e s t e d . Relating acidity to s u l f a t e and n i t r a t e i n the West i s confounded by the s t r o n g a s s o ­ c i a t i o n between c a l c i u m and s u l f a t e i n western p r e c i p i t a t i o n . Dry and wet d e p o s i t i o n have s i m i l a r r a t e s f a r from s o u r c e s ( b o t h i n the E a s t and the W e s t ) . S u l f a t e tends to dominate a c i d s p e c i e s i n p r e ­ c i p i t a t i o n , except near l a r g e s o u r c e s o f Ν 0 . χ

M e t e o r o l o g i c a l p r o c e s s e s , e m i s s i o n changes and measurement u n c e r t a i n t y l e a d to v a r i a b i l i t y i n d e p o s i t i o n r a t e s . Deposition measurements are u n c e r t a i n m a i n l y from a m b i g u i t i e s i n sampling t e c h ­ niques. M e t e o r o l o g i c a l v a r i a b i l i t y produces p o t e n t i a l l y l a r g e w i t h i n y e a r and y e a r - t o - y e a r d i f f e r e n c e s i n exposure to d e p o s i t i o n .

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch002

26

T H E CHEMISTRY OF ACID RAIN

F i g u r e 7. V a r i a t i o n i n y e a r - t o - y e a r t r a j e c t o r y c a l c u l a t i o n s b e g i n n i n g from t h e upper Ohio R i v e r V a l l e y . The c u r v e s r e p r e s e n t the c o e f f i c i e n t of v a r i a t i o n i n the d i s t r i b u t i o n s of annual " n a t u r a l p o t e n t i a l " o f m a t e r i a l r e l e a s e d i n t h e upper Ohio R i v e r V a l l e y r e a c h i n g l o c a t i o n s downwind from t h i s s o u r c e a r e a . (Redrawn and r e p r o d u c e d w i t h p e r m i s s i o n from R e f . 5. Copyright 1985 E l e c t r i c Power R e s e a r c h I n s t . ) .

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

2.

HIDY

27

Subcontinental Air Pollution Phenomena

The r e l i a b l e e s t i m a t i o n of source impact on r e c e p t o r c o n d i t i o n s i s d i f f i c u l t from t h e o r y because of undetermined u n c e r t a i n t i e s . I n f e r e n c e from comparison between e m i s s i o n s and measurements o f f e r s an a l t e r n a t i v e to c a l c u l a t i o n s . Measurements i n the E a s t have y i e l d e d ambiguous s o u r c e - r e c e p t o r r e l a t i o n s h i p s . However, e v i d e n c e s u g g e s t s t h a t r e c e n t changes i n s u l f a t e d e p o s i t i o n i n the West are l i n k e d w i t h r e l a t i v e l y l a r g e changes i n SO^ e m i s s i o n s from n o n f e r r o u s m e t a l s m e l t e r s , e s p e c i a l l y i n New Mexico and A r i z o n a . the

M e t e o r o l o g i c a l v a r i a b i l i t y needs to be c o n s i d e r e d i n r e l i a b i l i t y of source-receptor c a l c u l a t i o n s .

estimating

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch002

Acknowledgments P a r t o f t h i s s t u d y was d e r i v e d from r e s e a r c h sponsored by the E l e c t r i c Power R e s e a r c h I n s t i t u t e and West A s s o c i a t e s , I n c .

Literature Cited 1.

The Sulfate Regional Experiment: Report of Findings, EA-190(3), Electric Power Research Institute: Palo Alto, CA, 1983. 2. Acid Deposition; Atmospheric Processes in Eastern North America, National Academy of Sciences, 1983. 3. Galloway, J . N.; Likens, G. E.; Hawiey, M. E. Science: 1984, 226, 829-831. 4. Hidy, G. M.; Hansen, D. Α.; Henry, R. C.; Ganesan, K.; Collins, J . J . Air Poll. Contr. Assn. 1984, 31, 333-354. 5. Feasibility and Design of the Massive Aerometric Tracer Experiment (MATEX), EA-4305 (2), Electric Power Research Institute: Palo Alto, CA, 1985. 6. Oppenheimer, M.; Epstein, C.; Yuhnke, R. Science 1985, 229, 854-858. 7. Acid Deposition. Long Term Trends, National Academy of Sciences, 1986. 8. Hidy, G. M. Proc. 2nd Nat'l. Symposium on Acid Rain, Pittsburgh Chamber of Commerce, Pittsburgh, PA, 1982. 9. Bilonik, R. A. Atmos. Environ. 1985, 19, 1829-1845. 10. Hidy, G. M. Science 1986, 233, 10. 11. Newman, L . ; Benkovitz, C. Science 1986, 233, 11-12. RECEIVED February 3, 1987

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Chapter 3

Acid Deposition and Atmospheric Chemistry at Allegheny Mountain 1

1

1

1

1

W. R. Pierson , W. W. Brachaczek , R. A. Gorse, Jr. , S. M. Japar , J. M. Norbeck , and G. J. Keeler 2

1

Research Staff, Ford Motor Company, P.O. Box 2053, Dearborn, MI 48121 Department of Atmospheric and Oceanic Sciences, University of Michigan, Ann Arbor, MI 48109

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch003

2

In August, 1983, members of the Research Staff of Ford Motor Company c a r r i e d out a field experiment at two r u r a l s i t e s i n south­ western Pennsylvania involving various aspects of the a c i d deposition phenomenon. This presentation will focus on the wet (rain) deposi­ t i o n during the experiment, as w e l l as the r e l a t i v e importance of wet and dry deposition processes for n i t r a t e and sulfate at the s i t e s . Other aspects of the experiment have been discussed elsewhere: the chemistry of dew and its role in acid deposition (1), the dry deposition of HNO3 and SO2 to surrogate surfaces (2), and the role of elemental carbon in light absorption and of the latter in visibility degradation (3). EXPERIMENTAL

The experiment was conducted August 5-28, 1983 on abandoned radio towers atop Allegheny Mountain (elevation 838 meters) and Laurel Hill (elevation 850 meters, 35 km NW of Allegheny Mountain) i n southwestern Pennsylvania ( F i g . 1 ) . Both s i t e s are heavily forested and experience little l o c a l v e h i c l e traffic. A t t h e A l l e g h e n y M o u n t a i n s i t e a t m o s p h e r i c a e r o s o l and gas measurements, and l i g h t - s c a t t e r i n g and c o n d e n s a t i o n - n u c l e i - c o u n t m e a s u r e m e n t s , w e r e made a t o p t h e t o w e r 14 t o 17 m e t e r s a b o v e t h e ground. Wind speed and d i r e c t i o n , and atmospheric temperature, p r e s s u r e and h u m i d i t y , were c o n t i n u o u s l y r e c o r d e d . R a i n ( a n d dew) was c o l l e c t e d i n a 5 0 0 m^ mowed c l e a r i n g 60 m e t e r s n o r t h o f t h e tower. R a i n was c o l l e c t e d o n a n e v e n t b a s i s 1.8 m e t e r s above t h e ground i n t o t a r e d p o l y e t h y l e n e b o t t l e s , u s i n g a w e t - o n l y c o l l e c t o r (Wong L a b o r a t o r i e s M a r k V ) , e q u i p p e d w i t h a r e t r a c t i n g l i d a c t u a t e d by a r a i n s e n s o r . The s t a n d a r d c o l l e c t o r b u c k e t was s u p p l a n t e d b y a 30.5-cm diameter polyethylene funnel f i t t e d into the tared c o l l e c t i o n bottle. T h e r a i n f a l l a m o u n t ( i n mm o r i n 1 / m ) w a s d e t e r m i n e d f r o m the sample w e i g h t and the c o l l e c t o r geometry. T h e s a m p l i n g s e t u p was similar at Laurel H i l l . As s o o n as e a c h r a i n s t o p p e d , t h e s a m p l e was r e m o v e d , c a p p e d , and r e f r i g e r a t e d a t t h e s i t e . I t was t h e n t r a n s p o r t e d t o t h e f i e l d l a b o r a t o r y i n S o m e r s e t (midway b e t w e e n t h e s i t e s ) where i t was weighed and kept r e f r i g e r a t e d (never f r o z e n ) . The a n a l y t i c a l 2

0097-6156/87/0349-0028$06.00/0 © 1987 American Chemical Society

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

3.

Acid Deposition and Atmospheric Chemistry

PIERSON ET AL.

29

p r o c e d u r e s w e r e s i m i l a r t o t h o s e p r e v i o u s l y d e s c r i b e d ( 1 ) f o r dew samples. Q u a n t i t i e s m e a s u r e d i n c l u d e d pH, c o n d u c t i v i t y , t o t a l t i t r a t a b l e a c i d , a n d ( b y i o n c h r o m a t o g r a p h y ) SO^", NO3", NO2" , PO^", F", C I " , a n d B r " . The u n u s e d p o r t i o n s o f t h e r a i n s a m p l e s w e r e t r a n s p o r t e d t o Dearborn, s t i l l r e f r i g e r a t e d . Some 7 m o n t h s l a t e r t h e y w e r e r e ­ a n a l y z e d ; t o s e l e c t e d s a m p l e s H 2 O 2 was a d d e d b e f o r e a n a l y s i s ( f i n a l [ H 2 O 2 ] = 1.5%) t o make c e r t a i n t h a t a l l S ( I V ) h a d b e e n o x i d i z e d t o sulfate. A t t h i s t i m e NH^ , Na a n d Κ w e r e d e t e r m i n e d b y i o n c h r o m a ­ tography . A t m o s p h e r i c N O 2 , S O 2 , a n d O3 w e r e m e a s u r e d b y v a r i o u s m e t h o d s ( 1 , 4, 5 ) . l i g h t s c a t t e r i n g was m e a s u r e d b y i n t e g r a t i n g n e p h e l o meters. H N U 3 ( g ) a n d a e r o s o l N O 3 " w e r e m e a s u r e d b y t h e dénuder d i f f e r e n c e m e t h o d ( 6 - 8 ) u s i n g M g O - c o a t e d dénuder t u b e s a n d n y l o n membrane f i l t e r s , w i t h i o n c h r o m a t o g r a p h i c n i t r a t e d e t e r m i n a t i o n on a l k a l i n e f i l t e r e x t r a c t s . V a l i d ammonia d a t a w e r e n o t o b t a i n e d d u r i n g any o f t h e r a i n p e r i o d s . A e r o s o l s a m p l e s were c o l l e c t e d on f i l t e r s o f v a r i o u s t y p e s ( i n c l u d i n g i m p a c t o r s and v i r t u a l i m p a c t o r s ) and a n a l y z e d f o r H , ΝΗ^ , S 0 4 , and o t h e r components. The f i l t e r , dénuder, a n d impinger s a m p l e s w e r e c o l l e c t e d i n 1/2to 24-hour p e r i o d s s y n c h r o n i z e d w i t h each other but not g e n e r a l l y w i t h the onset or stop of r a i n . A c c o r d i n g l y i t s h o u l d be u n d e r s t o o d t h a t , i n t h e t r e a t m e n t that f o l l o w s , the atmospheric c o n c e n t r a t i o n s of a e r o s o l components, HNO3, a n d i m p i n g e r S O 2 t h a t we w i l l a s s o c i a t e w i t h t h e r a i n s a m p l e s a r e t h e average c o n c e n t r a t i o n s over the s e v e r a l - h o u r p e r i o d d u r i n g which the g i v e n r a i n o c c u r r e d , and n o t t h e c o n c e n t r a t i o n s j u s t d u r i n g the r a i n itself. I n s p e c t i o n o f t h e c o n t i n u o u s S O 2 , Ν 0 , O 3 , CNC a n d b t r a c e s i n d i c a t e s t h a t use o f the l o n g e r p e r i o d does not m a t e r i a l l y i n f l u e n c e the r e s u l t s .

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch003

+

+

+

=

χ

R E S U L T S AND

DISCUSSION

Rain Chemistry. The c h a r a c t e r i s t i c s o f t h e 17 r a i n e v e n t s a t t h e two s i t e s a r e s u m m a r i z e d a n d c o m p a r e d i n T a b l e 1 t o t h e dew s a m p l e s a n d t h e one s e t t l e d f o g w a t e r s a m p l e c o l l e c t e d a t A l l e g h e n y Mountain (1). (The dew was s a m p l e d i n a m a n n e r t h a t e x c l u d e d p r i o r dry d e p o s i t i o n . The r e p r e s e n t a t i v e n e s s o f t h e f o g w a t e r s a m p l e i s u n k n o w n - o t h e r f o g s o c c u r r e d b u t no s a m p l e s w e r e c o l l e c t e d . ) A number o f c o n c l u s i o n s c o n c e r n i n g r a i n a r e e v i d e n t f r o m T a b l e 1: •The r a i n was a c i d i c , w i t h t h e v o l u m e - a v e r a g e d pH o f 3.5 being p e r h a p s s o m e w h a t l o w e r t h a n t h a t o f t h e a v e r a g e summer r a i n i n the n o r t h e a s t (9-14). •H " a c c o u n t e d f o r a b o u t 9 0 % o f t h e t o t a l r a i n a c i d i t y . •The r a i n H c o u l d be a c c o u n t e d f o r i n t e r m s o f H 2 S O 4 and H N O 3 . •The S 0 4 / N 0 3 ~ e q u i v a l e n t s r a t i o o f a b o u t 3.7 i n t h e r a i n was c o m p a r a b l e t o t h a t c h a r a c t e r i s t i c o f summer r a i n s i n t h e n o r t h e a s t , i . e . , a b o u t 2.3 t o 4 ( 9 - 1 7 ) . •The L a u r e l H i l l r a i n s w e r e a b o u t 1 0 % m o r e c o n c e n t r a t e d i n a l l s p e c i e s than those c o l l e c t e d a t A l l e g h e n y M o u n t a i n ( i n agreement w i t h atmospheric a e r o s o l and t r a c e gas c o n c e n t r a t i o n s a t t h e sites). 4

+

=

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

30

dew

T H E CHEMISTRY OF ACID RAIN

When t h e c o m p o s i t i o n o f t h e r a i n i s c o m p a r e d w i t h t h a t o f t h e and t h e f o g , a number o f p o i n t s emerge: •While the ranges i n i o n c o n c e n t r a t i o n s , i n c l u d i n g H , are wider i n dew s a m p l e s , t h e r a n g e s o v e r l a p s o t h a t t h e dew was qualita­ t i v e l y s i m i l a r to d i l u t e r a i n . •The S 0 ^ / N 0 3 " c o n c e n t r a t i o n r a t i o i n t h e r a i n was a b o u t 3.7 e q u i v a l e n t s p e r e q u i v a l e n t v s . a r a t i o o f a b o u t 2.5 i n t h e dew. T h i s i s n o t s u r p r i s i n g s i n c e s i g n i f i c a n t amounts o f s u l f a t e are i n t r o d u c e d i n t o r a i n by n u c l e a t i o n s c a v e n g i n g (18) w h i l e a e r o s o l s u l f a t e d e p o s i t i o n t o dew i s m i n i m a l ( 1 ) . (In fact, at A l l e g ­ h e n y M o u n t a i n ( 1 ) S O 2 was r e s p o n s i b l e f o r a b o u t 8 0 % o f t h e dew S0 ".) •There i s l i t t l e evidence of the presence of S(IV) i n the r a i n a n d f o g w a t e r s a m p l e s ( t h a t i s , no s i g n i f i c a n t i n c r e a s e i n s u l f a t e was s e e n b e t w e e n t h e p r o m p t a n d d e l a y e d a n a l y s e s ) . By c o n t r a s t , t h e r e i s e v i d e n c e o f c o n s i d e r a b l e S ( I V ) (up t o 40%) r e m a i n i n g u n o x i d i z e d i n t h e dew a t t h e e n d o f t h e n i g h t ( 1 ) . •The c h e m i s t r y o f t h e one s e t t l e d f o g w a t e r s a m p l e i s s i m i l a r t o t h a t o f t h e more c o n c e n t r a t e d rains. +

=

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch003

4

A c i d Deposition Fluxes i n Rain. Table 2 l i s t s cumulative a m o u n t s o f v a r i o u s s p e c i e s d e p o s i t e d p e r u n i t a r e a i n r a i n , dew and fog d u r i n g the experiment. T a b l e 2 a l s o shows t h e f l u x e s o b t a i n e d by d i v i d i n g t h e a c c u m u l a t i o n b y t h e sum o f c o l l e c t i o n t i m e s . The

CITIES

H •

INOUSTRIALOR POPULATIONO17000)CENTERS

Δ

COAL- FIRED POWER PLANTS > 1000

MW

χ (L E.LIVERPOOL o| 8 CHESTER . J Λ ALIQUIPPA

ί ! \ » \ I WEIRTON

F i g u r e 1. The Pennsylvania.

site

PITTSBURGH METROAREA "

of

the

field

experiment i n

southwestern

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

4

+

+

2+

2

2 +

"

"

delayed

"

"

η

prompt

"

"

"

„

106%

115 (67-271)

1.15 122

111%

(109-220)

1.16

(6-21)

262 (138-700) 8.5

(251-575)

299

256 (125-700)

8 (3-25)

(249-575)

86 (63-202) 294

68 (41-252)

373

81 (14-251)

0.99 159 107%

1.27 42 (10-137) 94%

26

387

73 (10-254)

5 (0.3-16)

230

32 (3-138)

-

0.6-1.3

0. 6-1.0

0. 7 (0.1-2.0)

155

41 (14-99)

70 (48-159)

53 (15-116) 39 (8-99)

340 144

91 (5.5-347)

350

3.47

Fog (n - l )

8 (0-55)

311 (257-550)

(3.5-5.3)

108 (16-382)

4.0

Dew (n - 15)

70 (61-119)

290 (178-741)

(3.3-3.6)

349 (317-615)

3.5

Rain - L a u r e l (n - 5) a

Volume-weighted averages are the amount o f a given species deposited per u n i t area throughout the experiment d i v i d e d by the amount o f water deposited per u n i t area throughout the experiment. The prompt and delayed s u l f a t e data are, r e s p e c t i v e l y , the f i e l d - l a b o r a t o r y r e s u l t s and the re-analyses 7 months l a t e r .

Does not include a l l fog events.

Λ accounted f o r

Λ, jumho cm*^

ϊ on balance Σ+/Σ-

α­

SO4 "

3

N0 "

2

N0 "

Na , K , M g , C a

+

NH

H+

324 (227-763)

T i t r a t a b l e acid,

/ieq/liter

3.5 (3.1-3.75)

Rain - Allegheny (n - 12)

s e t t l e d fogwater (volume-weighted averages) *

Comparison of r a i n p r o p e r t i e s a t Allegheny and L a u r e l , August 1983, with Allegheny dew and

PH

Table 1.

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch003

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch003

32

T H E CHEMISTRY OF ACID RAIN

g r e a t e r f r e q u e n c y o f r a i n a t A l l e g h e n y M o u n t a i n p r o d u c e d a b o u t a 4f o l d greater accumulation o f a l l i o n i c species there than a t L a u r e l Hill. T h i s r e f l e c t s t h e r a n d o m n e s s o f summer c o n v e c t i v e p r e c i p i t a ­ t i o n ( a p p r o x i m a t e l y 7 0 % o f t h e r a i n a t A l l e g h e n y M o u n t a i n was convective i n nature). C o m p a r i s o n o f t h e d e p o s i t i o n e f f i c i e n c i e s o f r a i n , dew a n d f o g a t A l l e g h e n y M o u n t a i n shows t h a t d u r i n g t h e 2 1 - d a y e x p e r i m e n t , r a i n was r e s p o n s i b l e f o r t h e d e p o s i t i o n o f 60 t i m e s m o r e a c i d i t y ( t o g e t h e r w i t h r e l a t e d s p e c i e s ) t h a n w a s d e p o s i t e d d u r i n g dew p e r i o d s o r w i t h settled fogwater. P r e c i p i t a t i o n i n t h e v i c i n i t y o f A l l e g h e n y M o u n t a i n i s a b o u t 107 cm p e r y e a r ( 1 9 ) , o r c l o s e t o t h e r a t e r e c o r d e d i n T a b l e 2. I f t h e r a t i o b e t w e e n d e p o s i t i o n b y r a i n a n d d e p o s i t i o n t o dew d u r i n g t h e sampling p e r i o d i s a l s o r e p r e s e n t a t i v e o f t h eyear, then i t f o l l o w s t h a t t h e a n n u a l t o t a l a c i d d e p o s i t e d i n r a i n i s v e r y r o u g h l y 60 t i m e s a s g r e a t a s t h a t d e p o s i t e d t o dew o r i n s e t t l e d fogwater. S c a v e n g i n g R a t i o s f o r S0/, a n d N O 3 " b y R a i n . I f i t i s a s s u m e d t h a t t h e c o n c e n t r a t i o n o f a p o l l u t a n t i n p r e c i p i t a t i o n i s dependent on i t s c o n c e n t r a t i o n i n t h e a i r i n which t h ep r e c i p i t a t i o n forms, then t h e scavenging r a t i o , , c a nbe d e f i n e d as i - Ci /Ci =

W

r

a

Table 2. Deposition t o t a l s and deposition

fluxes associated

with r a i n a t

Allegheny and Laurel, August 1983; Allegheny dew and s e t t l e d fogwater shown f o r comparison Rain-Allegheny (n - 12)

Rain-Laurel (η - 5)

Dew (n - 15)

Fog (η - 1)

August 7-27 Accumulations: 2

Water g/m

T i t r a t a b l e a c i d peq/m H+

2

+

NH

S 0 " prompt 4

delayed

4513

295

(~210)

a

14800

4017

247

(~200)

a

a

(~590)

898

22

(~185)

88

(~140)

a

"

13100

3799

197

(~230)

a

"

13400

3860

220

(~230)

a

2

Water mg/m /sec

+

times) 1700

700

5

2

550

244

0.53

1.2

"

490

217

0.44

1.1

T i t r a t a b l e a c i d neq/m /sec

3.3

+

n

85

49

0.04

0.5

N0 _

w

115

60

0.16

0.8

NH

4

3

2

S 0 " prompt 4

delayed

a

1113

Fluxes (accumulations/collection

H

16500

2722

3440

3

2

12940

2570

4

_

N0

51000

"

440

206

0.35

1.28

"

450

209

0.39

1.24

Order-of-magnitude estimate, based on the estimate that 5 times as much was deposited during the experiment as i n the one 10-hour sample that was analyzed.

The représenta

tiveness o f the sample composition i s not known.

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

3.

a

33

Acid Deposition and Atmospheric Chemistry

PIERSON ET AL.

r

where C and Cj_ a r e t h e volume c o n c e n t r a t i o n s o f s p e c i e s i i n a i r ( e q u i v a l e n t s p e r cubic meter o f a i r ) and i n the r a i n w a t e r (equiva­ l e n t s p e r cubic meter o f l i q u i d water, i . e . , m i l l i - e q u i v a l e n t s p e r liter). The c a l c u l a t i o n o f s c a v e n g i n g r a t i o s u s i n g g r o u n d - l e v e l a t m o s p h e r i c d a t a f u r t h e r assumes t h a t t h e g r o u n d - l e v e l p o l l u t a n t d a t a are r e p r e s e n t a t i v e o f the a i r scavenged by a p r e c i p i t a t i n g cloud. This assumption appears a t l e a s t p a r t i a l l y j u s t i f i e d a t l o c a t i o n s remote enough from sources f o r v e r t i c a l m i x i n g t o have o c c u r r e d ( 1 8 ) . Washout r a t i o s f o r a e r o s o l S 0 4 a n d f o r t o t a l N O 3 " (HNO3 + a e r o s o l N O 3 " ) a r e p r e s e n t e d i n T a b l e 3. These washout r a t i o s p r e s u p p o s e , i n a c c o r d a n c e w i t h B a r r i e ' s t r e a t m e n t ( 1 8 ) , t h a t SO2 does not c o n t r i b u t e t o the r a i n S 0 a n d t h a t b o t h HNO3 a n d a e r o s o l N O 3 " contribute to the rain NO3'. Accordingly, the sulfate ratios are upper l i m i t s on W ; and t h e N O 3 " r a t i o s r e p o r t e d a r e c l o s e t o , and only s l i g h t l y less ^than, f o r HNO3 a l o n e s i n c e HNO3 i s h i g h l y s o l u b l e and dominates the ^total NO3". T h u s f r o m T a b l e 3, =

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch003

4

W

. - < a e r o s o l SO^

W... u

HNO3

=>

=

9 χ 10

5

19 χ 1 0

5

These r e s u l t s a r e s i m i l a r t o d a i l y - a v e r a g e d v a l u e s r e p o r t e d by B a r r i e (18) f o r s i t e s i n e a s t e r n Canada ( 1 9 7 8 - 1 9 8 1 ) . H i s mass scavenging r a t i o s , m u l t i p l i e d b y 890 ( t h e r a t i o b e t w e e n t h e d e n s i t y o f w a t e r a n d t h a t o f a i r a t t h e 838-m a l t i t u d e o f A l l e g h e n y M o u n t a i n i n o r d e r t o match u n i t s ) , g i v e t h e f o l l o w i n g averages f o r 4 remote l o c a t i o n s : W - 9 χ 1 0 t o 14 χ 1 0 f o r a e r o s o l S 0 ; W = 19 χ 1 0 t o 26 χ 4-10 f o r t o t a l N O 3 " ( H N O 3 + a e r o s o l N O 3 " ) . Forgone suburban/rural s i t e B a r r i e o b t a i n s \J = 10 χ 1 0 , W ^ = 11 χ 1 0 . S0 t-JM03 5

5

5

=

4

SQ

5

5

5

4

E s t i m a t i o n o f Wet a n d D r y A c i d . N O 3 " . a n d S0/^ Deposition Budgets a t Allegheny Mountain. To g a u g e t h e r e l a t i v e i m p o r t a n c e o f wet and d r y d e p o s i t i o n , t h e w e t - d e p o s i t i o n measurements need t o be accompanied by d r y - d e p o s i t i o n estimates. Nighttime dry deposition to dew was m e a s u r e d i n t h e p r e s e n t e x p e r i m e n t ( 1 ) , b u t we l a c k g o o d e s t i m a t e s o f d r y d e p o s i t i o n a t n i g h t w h e n dew was a b s e n t a n d , m o r e i m p o r t a n t , we l a c k a g o o d e s t i m a t e o f d r y d e p o s i t i o n d u r i n g t h e d a y when d e p o s i t i o n v e l o c i t i e s a r e e x p e c t e d t o be l a r g e s t . To d e a l w i t h t h i s d e f i c i e n c y two a l t e r n a t i v e a p p r o a c h e s a r e a d o p t e d a s f o l l o w s . F i r s t , n y l o n a n d T e f l o n 1 4 2 - m m - d i a m e t e r membrane f i l t e r s w e r e s e t o u t as s u r r o g a t e c o l l e c t i o n s u r f a c e s above t h e canopy a t A l l e g ­ h e n y d u r i n g d a y l i g h t on f i v e days d u r i n g t h e 1983 e x p e r i m e n t , t o gauge t h e r e l a t i v e i m p o r t a n c e o f a e r o s o l N O 3 " and S 0 4 d e p o s i t i o n ( o n T e f l o n ) a n d t h e d e p o s i t i o n o f HNO3 a n d S 0 ( n y l o n - T e f l o n d i f f e r e n c e ) (2). The a p p l i c a b i l i t y o f s u r r o g a t e s u r f a c e s t o r e a l o n e s , h o w e v e r , i s q u e s t i o n a b l e on s e v e r a l grounds. F o r HNO3 t h e s t i c k i n g e f f i c i e n c y to n y l o n i s p r o b a b l y (20) 100%; f o r SO2 t h e s t i c k i n g e f f i c i e n c y i s l e s s t h a n 100% b u t g r e a t e r than z e r o ( 2 1 ) ; and s t i c k i n g e f f i c i e n c i e s a r e b y n o means t h e o n l y i s s u e . The s e c o n d a p p r o a c h i s t o u s e t h e m e a s u r e d a m b i e n t c o n c e n t r a ­ tions i n combination with deposition v e l o c i t i e s reported i nthe literature (21-23). The t w o a p p r o a c h e s g i v e e f f e c t i v e l y t h e same r e s u l t s . For e x a m p l e , t h e a v e r a g e HNO3 d e p o s i t i o n v e l o c i t y m e a s u r e d b y m i c r o m e t e o r o l o g i c a l m e t h o d s a b o v e a f o r e s t i n e a s t T e n n e s s e e o r o n summer =

=

2

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

(Meq/1)

4

S07

Rain*

653

704 1181

44o

213

176

811

276

138

230

3

4

5

755

755

773

650

537

542

13

14

15

252

273

573

2

3

4

average

377

158

830

2.0 χ 10

17.3 x 10

(9.5

± 5.6)

χ

10

15.2 χ 10

864 1044

3.0 χ 10

17.3 x 10

7.0 χ 10

660

1066

754

7.1 χ 10

8.6 χ 10

849

3.8 χ 10

849

18.0 χ 10

849

980

13.1 χ 10

6.5 χ 10

41

5

5

5

5

5

5

5

5

194

72

63

135

161

252

212

79

139

5

5

150

63

63

70

58

(Meq/1)

Rain N0~

5

5

5

5

5

5

12.9 χ 10

4.7 χ 10

5.9 x 10

so=

w

^Results from the delayed analyses where available

392

1

226

755

284

12

Laurel H i l l

388

163

700

6

10

681

681

653

44o

260

207

213

2

3 3

103

117

83.8

78.5

77.8

41.6

81.7

74.6

74.6

74.6

154

87.5

43.4

21.3

21.3

55.8

55.8

3

8.6 χ 10 16.6 χ 10

5

5

5

5

5

5

5

5

5

5

5

5

5

5

5

5

8.0 χ 10

32.5 x 10

19.7 x 10

33.8 χ 10

28.4 χ 10

10.6 χ 10

9.0 χ 10

4.7 x 10

34.6 χ 10

29.6 χ 10

29.6 χ 10

12.5 x 10

10.4 χ 10

VNO

w

(19 + 11) χ 10

(neq/m )

t o t a l N0~

36.6

75.9

70.0

70.0

70.0

153

73.7

27.9

19.5

19.5

46.9

46.9

(neq/m )

M 0

Rain Scavenging Ratios f o r SO^ and N0~

(neq/m"

so

1

3

(neq/m )

Aerosol

2

Allegheny Mountain

Rain #

Table 3

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch003

3.

Sources of NO3"

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch003

August 5-28,

and SC>4~ deposition at Allegheny Mountain,

1983

a

N0

_

804

3

2

Rain (12 events) Fog

(1 event)

Dew

(15 events)

(neo/m *)

3440

Dry - without dew

Based on deposition to nylon surrogate substances not depositing to nylon

4

13400

140

230

88

220

2400

1 ^equivalent — 1 μπιοίε; f o r S 0

b

5000

e

2 μequivalents — 1 /zmole.

surfaces; does not

(e.g.,

E

2

(ueq/m )

For NO3"

35

Acid Deposition and Atmospheric Chemistry

PIERSON ET AL.

include

NO2).

Based on the measurement of dry deposition to nylon surrogate

surfaces

we

estimate that SO2 contributed about 5000 /xeq/m of dry deposition to the 2

S04

=

total.

Aerosol S04

=

adds another 300 μeq/m

2

or l e s s .

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

T H E CHEMISTRY OF ACID RAIN

36

d a y s o v e r a n I l l i n o i s p a s t u r e ( 2 2 ) i s a b o u t t h e same a s t h e 2.5 + 1.5 cm/sec m e a s u r e d b y t h e s u r r o g a t e c o l l e c t o r s ( t o g e t h e r w i t h atmosp h e r i c c o n c e n t r a t i o n s ) i n the present experiment. T h e 0.5 c m / s e c S O 2 d e p o s i t i o n v e l o c i t y t o the surrogate c o l l e c t o r s i s i n the range r e p o r t e d t o v e g e t a t i o n (23) ( a v e r a g e - 0 . 7 c m / s e c ) . T h e 0.05 c m / s e c d e p o s i t i o n v e l o c i t y o f a e r o s o l S O ^ t o the surrogate c o l l e c t o r s i s i n the range g i v e n i n the l i t e r a t u r e (23). The r e s u l t s e m p l o y i n g d a y t i m e d r y d e p o s i t i o n e s t i m a t e s f r o m t h e s u r r o g a t e c o l l e c t o r s a r e g i v e n i n T a b l e 4; t h e s e e s t i m a t e s p r e s u p p o s e t h a t t h e f i v e d a y s a r e r e p r e s e n t a t i v e . W h i l e r a i n a c c o u n t e d f o r some 60% o f t h e N O 3 ' d e p o s i t i o n , d r y d e p o s i t i o n o f HNO3 i n t h e a b s e n c e o f dew a p p e a r s a l s o t o b e i m p o r t a n t . T h i s s i m i l a r t o t h e e s t i m a t e made by H u e b e r t (22) i n t h e I l l i n o i s e x p e r i m e n t t h a t HNO3 d r y d e p o s i t i o n accounted f o r 48% o f the NO3" wet/dry d e p o s i t i o n . For S 0 ^ deposit i o n , r a i n i s a g a i n t h e d o m i n a n t medium; h o w e v e r , t h e d r y d e p o s i t i o n o f S O 2 may a l s o b e i m p o r t a n t . The c o n t r i b u t i o n s o f d r y - d e p o s i t e d a e r o s o l n i t r a t e a n d s u l f a t e , n o t l i s t e d i n T a b l e 4, w e r e s m a l l ( a b o u t 5%) a t t h e s i t e . I f we now s u p p o s e t h a t S O 2 i s t a n t a m o u n t t o H 2 S O 4 i n a c i d i f y i n g p o t e n t i a l , o n g r o u n d s t h a t S O 2 r e a d i l y o x i d i z e s t o H 2 S O 4 , a n d i f we r e c a l l t h a t the NO3" and S 0 ^ i n the rain/dew/fog samples can be r e g a r d e d a s m o s t l y HNO3 a n d H 2 S O 4 , t h e n t h e t o t a l s t r o n g a c i d d e p o s i t e d i n the experiment can be a p p o r t i o n e d from T a b l e IV r o u g h l y as f o l l o w s : 47% = H2SO4 i n r a i n (34% S O 2 s c a v e n g i n g , 1 3 % a e r o s o l S O ^ scavenging) 2 3 % = S O 2 d r y d e p o s i t i o n w i t h o u t dew 16% = HNO3 i n r a i n 1 1 % = H N O 3 d r y d e p o s i t i o n w i t h o u t dew

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch003

=

=

3%

= HNO3

and H2SO4

i n f o g a n d dew +

At the r a t e s i m p l i e d b y Table IV, t o t a l wet and dry H d e p o s i t i o n w o u l d b e a b o u t 300 moles H / h e c t a r e / m o n t h - i n A u g u s t . +

ACKNOWLEDGMENTS We a r e p l e a s e d t o a c k n o w l e d g e t h e a s s i s t a n c e o f t h e P e n n s y l v a n i a T u r n p i k e C o m m i s s i o n i n p r o v i d i n g a c c e s s a n d e l e c t r i c power t o t h e two s i t e s a n d h e l p i n g u s s e t u p t h e e x p e r i m e n t ; we a r e e s p e c i a l l y i n d e b t e d t o W a r r e n E. K i p p , R o b e r t E. D a v i s , N e v i n A. M i l l e r , C a r l Baker a n d the crew a t the A l l e g h e n y Mountain Tunnel, and the C h i e f Engineer and Deputy E x e c u t i v e D i r e c t o r o f the P e n n s y l v a n i a Turnpike C o m m i s s i o n , R o b e r t H. K l u c h e r . A t F o r d , we a r e i n d e b t e d t o R i c h a r d F l o y d , L e e C. W e s t w o o d , Y. T. L i u , a n d G. E. F i s h e r f o r t h e i r p a r t i c i p a t i o n i n the chemical a n a l y s i s . Ford p a r t i c i p a n t s i n the f i e l d e x p e r i m e n t i t s e l f i n c l u d e d K a r e n M. A d a m s , J a m e s W. B u t l e r , A n n C. C l e a r y , J a m e s C. D z i a d o s z , L a r r y P. H a a c k , Thomas J . K o r n i s k i , W i l l i a m K. O k a m o t o , a n d M i c h a e l J . R o k o s z . J e f f r e y M. M a s t e r s , f o r m e r l y o f the U n i v e r s i t y o f Michigan, p a r t i c i p a t e d i n the f i e l d and handled the o n - s i t e meteorology. P r o f . P e r r y J . Samson o f t h e U n i v e r s i t y o f M i c h i g a n a s s i s t e d i n the t r a j e c t o r y a n a l y s i s and meteorology. We t h a n k W i l l i a m J . C o u r t n e y o f N o r t h r o p S e r v i c e s a n d Thomas G. D z u b a y , C h a r l e s W. L e w i s , a n d R o b e r t K. S t e v e n s o f E P A / E S R L for t h e i r c o l l a b o r a t i o n i n c l u d i n g f i e l d i n t e r c a l i b r a t i o n and the use

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

3.

PIERSON ET AL.

Acid Deposition and Atmospheric Chemistry

37

of their instruments. We a r e g r a t e f u l t o E . E u g e n e W e a v e r , who r e t u r n e d from F o r d r e t i r e m e n t to h e l p , w i t h A d e l e Weaver, on the f i e l d experiment. We t h a n k P r o f . J a m e s A . L y n c h o f t h e P e n n s y l v a n i a S t a t e U n i v e r s i t y f o r s h a r i n g d e t a i l e d r a i n d a t a w i t h us from h i s Laurel H i l l site. O u r w o r k was s u p p o r t e d i n p a r t b y t h e N a t i o n a l Science Foundation under I n d u s t r y / U n i v e r s i t y Cooperative Research G r a n t NO. A T M - 8 5 0 7 2 8 2 t o t h e U n i v e r s i t y o f M i c h i g a n .

LITERATURE CITED

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch003

(1)

(2)

(3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21)

Pierson, W.R., Brachaczek, W.W., Gorse, R.A., Jr., Japar, S.M. and Norbeck, J.M., Paper No. 85-7.4, Air Pollution Control Association 78th Annual Meeting, Detroit, June (1985); J. Geophys. Res. 91, 4083 (1986). Japar, S.M., Brachaczek, W.W., Gorse, R.A., Jr., Norbeck, J.M. and Pierson, W.R., presented at Muskoka '85: International Symposium on Acidic Precipitation, Minett, Ontario, September (1985). Japar, S.M., Brachaczek, W.W., Gorse, R.A., Jr., Norbeck, J.M., and Pierson, W.R., Atmos. Environ. 20, 1281 (1986). Holdren, M.W. and Spicer, C.W., Environ, Sci. Tech., 18, 113 (1984). Pierson, W.R., Brachaczek, W.W., Truex, T.J., Butler, J.W., and Korniski, T.J., Annals N.Y. Acad. Sci. 338, 145 (1980). Appel, B.R., Tokiwa, Υ., and Haik, Μ., Atmos. Environ. 15, 283 (1981). Shaw, R.W., Jr., Stevens, R.K., Bowermaster, J . , Tesch, J.W., and Tew, E., Atmos. Environ. 16, 845 (1982). Spicer, D.W., Howes, J.E., Jr., Bishop, T.A., Arnold, L.H., and Stevens, R.K., Atmos. Environ. 16, 1487 (1982). Bowersox, V.C. and de Pena, R.G., J. Geophys. Res. 85, 5614 (1980). Bowersox, V.C. and Stensland, R.G., Paper No. 81-6.1, Air Pollution Control Association 74th Annual Meeting, Philadelphia, June (1981). Altwicker, E.R. and Johannes, A.H., Paper No. 81-6.2, Air Pollution Control Association 74th Annual Meeting, Philadelphia, June (1981) Pack, D.H., Atmos. Environ. 16, 1145 (1982). Hales, J.M., et al, Atmos. Environ. 16, 1603 (1982). Pratt, G.C. and Krupa, S.V., Atmos. Environ. 17, 1845 (1983). Galloway, J.N. and Likens, G.E., Atmos. Environ. 15, 1081 (1981). Henderson, R.G. and Weingartner, Κ., Atmos. Environ. 16, 1657 (1982) Wilson, W.E. and Husar, R.B., Society of Automotive Engineers Technical Paper Series, Paper No. 830647 (1983). Barrie, L.A., J. Geophys. Res. 90, 5789 (1985). National Oceanographie and Atmospheric Administration, Climates of the States. Vol. 2 (Gale Research Co., Detroit (1978)), P. 852. Durham, J.L. and Stockburger, L., Atmos. Environ. 20, 559 (1986). Fowler, D., Atmos. Environ. 12, 369 (1978).

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

38

T H E CHEMISTRY OF ACID RAIN

22) Huebert, B.J. and Robert, C H . , J. Geophys. Res. 90, 2085 (1985) . (23) Schmel, G.A., Atmos. Environ. 14, 983 (1980).

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch003

RECEIVED May 15, 1987

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Chapter 4

The Western Atlantic Ocean Experiment 1

2

3

4

James N. Galloway , Thomas M. Church , Anthony H. Knap , Douglas M. Whelpdale , and John M. Miller 5

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch004

1

Department of Environmental Sciences, University of Virginia, Charlottesville, VA 22903 College of Marine Studies, University of Delaware, Newark, DE 19711 Bermuda Biological Station, St. Georges West 1-15, Bermuda Atmospheric Environment Service, 4905 Dufferin Street, Downsview, Ontario M3H 5T4, Canada National Oceanic and Atmospheric Administration, 8060 13th Street, Silver Spring, MD 20910

2

3

4

5

The Western Atlantic Ocean Experiment (WATOX) investi­ gates the flux and fate of sulfur, nitrogen, and tracemetal and trace-organic compounds eastward from North America. Using a variety of sampling platforms (ships, aircraft, islands), samples of gases, aerosols, and precipitation have been used to determine the impact of North America on atmospheric chemical cycles of the western A t l a n t i c Ocean. This paper provides an overview of the results obtained since WATOX began i n 1980. The Western A t l a n t i c Ocean E x p e r i m e n t (WATOX) i s d e s i g n e d t o d e t e r ­ mine the amount and the f a t e o f s e l e c t e d s u l f u r , n i t r o g e n , m e t a l and o r g a n i c compounds advected e a s t w a r d from N o r t h A m e r i c a . The s p e c i f i c a t m o s p h e r i c f l u x e s b e i n g i n v e s t i g a t e d are d e p i c t e d i n F i g u r e 1 and e x p l a i n e d i n T a b l e I ; the p a r t i c i p a t i n g u n i v e r s i t i e s and agencies are l i s t e d i n T a b l e I I . T h i s paper p r e s e n t s a b r i e f o v e r v i e w o f the approach we are u s i n g t o a c h i e v e the a b o v e - s t a t e d o b j e c t i v e s and summarizes our a c c o m p l i s h m e n t s . The measurement program has two components, l o n g - t e r m and i n t e n s i v e . F o r the l o n g - t e r m component, data c o l l e c t i o n t o d e t e r ­ mine the c o m p o s i t i o n o f wet d e p o s i t i o n a t Lewes, D e l a w a r e , and on Bermuda began i n 1980. I n 1984, another s i t e was added a t A d r i g o l e , I r e l a n d . From 1981 t o 1985 d u r i n g M a y - O c t o b e r , p r e c i p i t a t i o n sam­ p l e s were a l s o c o l l e c t e d on two s h i p s c r u i s i n g w e e k l y between New York C i t y , Bermuda, and Nassau. P r e c i p i t a t i o n - c h e m i s t r y data from the t h r e e l a n d - b a s e d s i t e s and from the s h i p s were used t o c a l c u l a t e

0097-6156/87/0349-0039$06.00/0 © 1987 American Chemical Society

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

THE CHEMISTRY OF ACID RAIN

40

T a b l e I . WATOX F l u x e s and Methods (see F i g . 1) D e t e r m i n a t i o n Methods

F l u x e s from F i g . 1 A.

B.

Emission to North atmosphere

American

A d v e c t i o n eastward

C. Wet d e p o s i t i o n

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch004

Dry d e p o s i t i o n D.

Atmospheric t r a n s f o r m a t i o n s

E.

E m i s s i o n from sea s u r f a c e

F.

Advection eastward

L i t e r a t u r e search C a l c u l a t i o n s ; land-based and a i r c r a f t sampling F i e l d measurements on s h i p s , on Bermuda, and a t Lewes, DE C o n c e n t r a t i o n measurements on s h i p s , on Bermuda, and a t Lewes, DE C a l c u l a t i o n s ; atmospheric measurements C a l c u l a t i o n s ; e s t i m a t e s from literature C a l c u l a t i o n s ; land-based, s h i p based, and a i r c r a f t sampling

Table I I . Members o f t h e WATOX Consortium Investigator and Agency J . N. Galloway University of Virginia C h a r l o t t e s v i l l e , VA

WATOX d i r e c t o r Atmospheric d e p o s i t i o n o f S and Ν compounds and o r g a n i c a c i d s

T. M. Church U n i v e r s i t y o f Delaware Newark, DE

Atmospheric d e p o s i t i o n o f t r a c e m e t a l elements

A. H. Knap Bermuda B i o l o g i c a l S t a t i o n S t . Georges, Bermuda

Atmospheric d e p o s i t i o n o f t r a c e o r g a n i c compounds

J . M. M i l l e r NOAA S i l v e r S p r i n g , MD

T r a n s p o r t and air-mass

D. M. Whelpdale T r a n s p o r t and air-mass Atmospheric Environment S e r v i c e T o r o n t o , Canada J . Boatman NOAA B o u l d e r , CO

Aircraft

trajectories

trajectories

coordination

r a t e s o f wet d e p o s i t i o n and t o t r a c k a i r masses e a s t w a r d from N o r t h America. The i n t e n s i v e component o f the WATOX measurement program (Intensives) involves p e r i o d i c sampling t o a s c e r t a i n the processes c o n t r o l l i n g t h e t r a n s p o r t , t r a n s f o r m a t i o n , and d e p o s i t i o n o f

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch004

4.

GALLOWAY ET AL.

The Western Atlantic Ocean Experiment

41

m a t e r i a l s t o t h e w e s t e r n A t l a n t i c Ocean. D u r i n g t h e seven I n t e n ­ s i v e s t h a t have a l r e a d y t a k e n p l a c e (Table I I I ) , each o f w h i c h l a s t e d from one t o f o u r weeks, i n s t r u m e n t s s p e c i f i c a l l y d e s i g n e d t o d e t e r m i n e a t m o s p h e r i c c o n c e n t r a t i o n s o f gas and a e r o s o l s p e c i e s were p l a c e d a t land-based s i t e s and on s h i p s and a i r c r a f t . F o r each I n t e n s i v e , s c i e n t i s t s from i n s t i t u t i o n s t h a t were n o t p a r t o f t h e WATOX c o n s o r t i u m were i n v i t e d t o p a r t i c i p a t e i n such a way as t o complement t h e s k i l l s and r e s e a r c h a b i l i t i e s o f the permanent WATOX personnel. The f i r s t two I n t e n s i v e s (WATOX-82 and WATOX-83, see Table I I I ) i n v e s t i g a t e d changes i n t h e c o m p o s i t i o n o f a i r p a r c e l s t h a t t r a v e l from N o r t h A m e r i c a t o Bermuda. D u r i n g WATOX-82 and WATOX-83, s c i e n ­ t i s t s from G e n e r a l Motors and the U n i v e r s i t y o f M i a m i measured c o n c e n t r a t i o n s o f t r a c e gases and a e r o s o l s a t Lewes, Delaware, and H i g h P o i n t , Bermuda. WATOX-84, t h e t h i r d I n t e n s i v e , used d a t a from samples c o l l e c t e d onboard t h e RV K n o r r as i t t r a v e l e d between N o r t h A m e r i c a and A f r i c a . These d a t a were used t o support t h e gas and a e r o s o l d a t a from WATOX82 and WATOX-83 and t o t e s t new s h i p b o a r d p r e c i p i t a t i o n - c o l l e c t i o n instruments. WATOX-82, -83, and -84 sampled a i r i n the marine boundary l a y e r . These s e a - l e v e l measurements gave no i n f o r m a t i o n about uppera i r t r a n s p o r t . To overcome t h i s d e f i c i e n c y , t h e f o u r t h t h r o u g h t h e seventh I n t e n s i v e s i n c o r p o r a t e d d a t a c o l l e c t e d onboard two NOAA r e s e a r c h a i r c r a f t , t h e NOAA WP-3D and the NOAA K i n g A i r . (See Table I I I f o r t h e s p e c i f i c s p e c i e s measured.) B o t h a i r c r a f t c a r r i e d s a m p l i n g and a n a l y t i c a l equipment d e s i g n e d t o d e t e r m i n e the v e r t i c a l and h o r i z o n t a l c h e m i c a l s t r u c t u r e o f t h e atmosphere. F o r WATOX-85 the K i n g A i r f l e w m i s s i o n s e a s t o f Newport News, V i r g i n i a , and a d j a c e n t t o Bermuda d u r i n g passages o f w i n t e r c o l d f r o n t s between N o r t h A m e r i c a and Bermuda. D u r i n g these f l i g h t s a t m o s p h e r i c gases and a e r o s o l s were sampled and the data were r e c o r d e d as a f u n c t i o n o f a l t i t u d e and l a t i t u d e . We used b o t h a i r c r a f t f o r WATOX-86A. The WP-3D (based a t McGuire A i r F o r c e Base, New J e r s e y ) f l e w p a r a l l e l t o the c o a s t between Newfoundland and F l o r i d a and t h e K i n g A i r (based a t Eanscom F i e l d near Boston, M a s s a c h u s e t t s ) f l e w a course o f f Cape Cod. WATOX 86-B used o n l y t h e K i n g A i r d u r i n g t h r e e weeks i n F e b r u a r y o f 1986. Data from b o t h 86-A and -B were used t o a n a l y z e f u r t h e r the v e r t i c a l and the h o r i z o n t a l c h e m i c a l s t r u c t u r e o f t h e atmosphere. WATOX-86C used t h e K i n g A i r out o f Bermuda t o d e t e r m i n e t h e a d v e c t i o n f l u x e s o f s u l f u r and n i t r o g e n s p e c i e s when a i r f l o w was c o n t r o l l e d by t h e Bermuda High and thus unimpacted by e m i s s i o n s from N o r t h America. Summary o f F i n d i n g s E a s t w a r d A d v e c t i o n o f S and Ν from N o r t h America. To make an i n i ­ t i a l e s t i m a t e o f t r a n s p o r t and a d v e c t i o n e a s t w a r d from N o r t h A m e r i c a , M i l l e r and H a r r i s (1) have c a l c u l a t e d back t r a j e c t o r i e s from Bermuda and have developed a f l o w c l i m a t o l o g y c o v e r i n g seven y e a r s — f r o m January 1975 t o December 1981. U s i n g the GAMBIT-1 model from the NOAA A i r Resources L a b o r a t o r y , t h i s group has produced 10day back t r a j e c t o r i e s f o r t h e 850-mb l e v e l , on a d a i l y b a s i s , c o v e r ­ ing t h i s seven-year p e r i o d . M i l l e r and H a r r i s (1,) have adopted a

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

T H E CHEMISTRY OF ACID RAIN

42

T a b l e I I I . WATOX I n t e n s i v e s

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch004

Name/Date

Location

Platform

WATOX-82 August

Lewes Bermuda

Ground (G, A, P) Ground (G, A, P)

WATOX-83 February

Lewes Bermuda

Ground (G, A, P) Ground (G, A, P)

WATOX-84 May

Atlantic R. V. K n o r r (Dakar t o (G, A, P) Boston)

WATOX-85 Mar/Apr

Lewes Bermuda

Ground (G, A, P) Ground (G, A, P)

S p e c i e s Measured Gas: NO, NO . S 0 CO A e r o s o l : NO? SO^, t r a c e metals P r e c i p i t a t i o n : Major i o n s , trace metals, organic acids, trace organics CO Gas: NO, Ν 0 , S 0 , A e r o s o l : N O 3 , SO^, t r a c e metals P r e c i p i t a t i o n : Major i o n s , trace metals, organic acids, trace organics Gas: H N 0 , S 0 DMS A e r o s o l : NO3 "SO^, t r a c e metals, organic acids P r e c i p i t a t i o n : Major ions, trace metals, organic acids, trace organics Gas: NO, Ν 0 , t o t a l S, CO, CO3, t r a c e o r g a n i c s Aerosol: trace metals, NO3, 0

χ

2

3

0

χ

so

4

P r e c i p i t a t i o n : Major i o n s , trace metals, organic acids, trace organics WATOX-86A January

WATOX-86B February

Lewes Bermuda McGuire AFB Hanscom Field

Lewes Bermuda Hanscom Field

Ground (P) Ground (P) WP-3D (G, A) K i n g A i r (G, A)

Ground (P) Ground (P) K i n g A i r (G, A)

Gas: H N 0 , 3

Lewes Bermuda Bermuda

Ground (P) Ground (P) K i n g A i r (G, A)

N 0 , ΝΟ 2

χ

2

Gas: H N 0 , 3

PAN, NO,

N 0 , Ν0 2

χ

S 0 , DMS, CO, O 3 , t r a c e organics, organic acids A e r o s o l : Trace metals, N O 3 , 2

so WATOX-86C June

PAN, NO,

S 0 , DMS, CO, O 3 , t r a c e organics, o r g a n i c a c i d s A e r o s o l : NO^"", S 0 ^ ~ , t r a c e metals, organic acids, trace organics P r e c i p i t a t i o n : Major i o n s , o r ­ ganic a c i d s , trace organics

4

P r e c i p i t a t i o n : Major ions, o r ­ ganic a c i d s , t r a c e o r g a n i c s Gas: HNO,, PAN, NO, N 0 , Ν 0 S 0 , DMS, CO, O 3 , t r a c e organics, organic acids Aerosol: Trace metals, NO3, 2

χ

2

so

4

P r e c i p i t a t i o n : Major i o n s , o r ­ ganic a c i d s , t r a c e o r g a n i c s NOTE: (G) means t h a t gas was c o l l e c t e d , precipitation.

(A), a e r o s o l , ( P ) ,

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch004

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GALLOWAY ET

AL.

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c l a s s i f i c a t i o n scheme t h a t s t r a t i f i e s a i r f l o w as a f u n c t i o n of compass s e c t o r . T h i s c l a s s i f i c a t i o n shows t h a t , f o r a l m o s t 60% o f the seven y e a r s , t h e r e was a d i r e c t f l o w o f a i r o f f the N o r t h American continent. To d e t e r m i n e the a d v e c t i o n r a t e of S and Ν eastward from N o r t h A m e r i c a , Whelpdale and h i s c o l l e a g u e s (2) c a l c u l a t e d a i r - m a s s advec­ t i o n as a f u n c t i o n of l a t i t u d e and a l t i t u d e ( F i g u r e 2). Then, u s i n g r e p r e s e n t a t i v e g r o u n d - l e v e l and above-ground c o n c e n t r a t i o n s o f t r a c e s u l f u r and n i t r o g e n s p e c i e s , G a l l o w a y and h i s c o l l e a g u e s (3) c a l c u ­ l a t e d a d v e c t i o n f l u x e s o f S and Ν by c o m b i n i n g the l o n g i t u d i n a l and a l t i t u d i n a l v a r i a t i o n s of a i r - m a s s f l u x w i t h the l o n g i t u d i n a l and a l t i t u d i n a l v a r i a t i o n s of the a t m o s p h e r i c c o n c e n t r a t i o n s o f S and Ν compounds ( F i g u r e s 3 and 4). They r e p o r t a b r o a d maximum i n S and Ν t r a n s p o r t between 38° Ν and 52° N. Of the S and Ν e m i t t e d t o the atmosphere of e a s t e r n N o r t h A m e r i c a , about 34% and 22-69%, r e s p e c ­ t i v e l y , are advected eastward. T r a n s p o r t a t a l l a l t i t u d e s up t o a t l e a s t 5.5 km i s i m p o r t a n t . Impact of N o r t h A m e r i c a n E m i s s i o n s on Wet D e p o s i t i o n t o the W e s t e r n A t l a n t i c Ocean. Wet d e p o s i t i o n has been c o l l e c t e d by event d u r i n g WATOX at two s i t e s on Bermuda, one s i t e near Lewes, Delaware, and on b o a r d s h i p s . These w e t - d e p o s i t i o n samples have been a n a l y z e d f o r a c i d i c s p e c i e s , m e t a l s , and o r g a n i c compounds. T h i s s e c t i o n d i s ­ cusses our i n t e r p r e t a t i o n of the marine p r e c i p i t a t i o n - c h e m i s t r y d a t a and the r e s u l t s o f our a n a l y s e s as w e l l as the i n f l u e n c e o f N o r t h A m e r i c a n e m i s s i o n s on p r e c i p i t a t i o n c o m p o s i t i o n . I n i n t e r p r e t i n g m a r i n e p r e c i p i t a t i o n - c h e m i s t r y data, the d i f ­ f e r e n t i a t i o n of s e a - s a l t and n o n - s e a - s a l t (or excess s e a - s a l t ) com­ ponents i s e s s e n t i a l . U n c e r t a i n t i e s i n such c a l c u l a t i o n s a r i s e from the u n c e r t a i n t i e s r e g a r d i n g (1) the c o m p o s i t i o n of seawater, (2) the a n a l y s e s , (3) the amount of d r y - d e p o s i t e d sea s a l t i n the samples, (4) the v a l i d i t y of assuming a p u r e l y marine source f o r the s e a - s a l t r e f e r e n c e s p e c i e s , and (5) the v a l i d i t y of assuming no f r a c t i o n a t i o n d u r i n g o r a f t e r the p r o d u c t i o n o f s e a - s a l t a e r o s o l s . Xeene and h i s c o l l e a g u e s at the U n i v e r s i t y of V i r g i n i a (4) assessed these u n c e r ­ t a i n t i e s and e v a l u a t e d the assumptions by a n a l y z i n g the c o m p o s i t i o n o f p r e c i p i t a t i o n c o l l e c t e d on Bermuda. They r e p o r t s i g n i f i c a n t c o n c e n t r a t i o n s of l o c a l l y d e r i v e d a l k a l i and a l k a l i n e e a r t h m e t a l s as w e l l as evidence of the i n f l u e n c e of c o n t i n e n t a l and n o n - s e a - s a l t marine sources of excess S O ^ " c o n c e n t r a t i o n s . These o b s e r v a t i o n s suggest t h a t the p a s t assumptions i n v o l v e d i n s e a - s a l t c o r r e c t i o n s are not always v a l i d . T h e r e f o r e , t o s e l e c t the a p p r o p r i a t e r e f e r ­ ence s p e c i e s , i n d i v i d u a l d a t a s e t s s h o u l d be e v a l u a t e d u s i n g o b j e c ­ tive c r i t e r i a . The c o n c e n t r a t i o n of excess components i n p r e c i p i t a t i o n i s the d i f f e r e n c e between the t o t a l c o n c e n t r a t i o n and the s e a - s a l t compo­ nent of the t o t a l c o n c e n t r a t i o n . There are o f t e n l a r g e u n c e r ­ t a i n t i e s a s s o c i a t e d w i t h excess c o n c e n t r a t i o n s r e s u l t i n g from s m a l l d i f f e r e n c e s between l a r g e numbers. Hawley, G a l l o w a y , and Keene ( U n i v e r s i t y of V i r g i n i a , C h a r l o t t e s v i l l e , u n p u b l i s h e d data) have d e r i v e d a nomogram t e c h n i q u e t o d e t e r m i n e the u n c e r t a i n t y i n v o l v e d knowing o n l y the t o t a l c o n c e n t r a t i o n of the element i n q u e s t i o n (e.g., SO^-), the t o t a l N a c o n c e n t r a t i o n , and the r e s p e c t i v e a n a l y +

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

THE CHEMISTRY OF ACID RAIN

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Western Atlantic Ocean

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F i g u r e 1. A c o n c e p t u a l overview o f the f l u x e s b e i n g i n v e s t i g a t e d i n WATOX and t h e i r method o f measurement (see a l s o T a b l e I ) .

F i g u r e 2. Net a i r f l u x as a f u n c t i o n o f l a t i t u d e and a l t i t u d e . ( R e p r i n t e d w i t h p e r m i s s i o n from r e f . 2. 1984 Pergamon J o u r n a l s . )

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch004

GALLOWAY ET AL.

The Western Atlantic Ocean Experiment

Sulfur (Tg.y ) 1

F i g u r e 3. Net s u l f u r f l u x as a f u n c t i o n o f l a t i t u d e and a l t i t u d e ( R e p r i n t e d w i t h p e r m i s s i o n from r e f . 3. 1984 Pergamon J o u r n a l s . )

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch004

F i g u r e 4. altitude. Journals.)

Net n i t r o g e n f l u x as a f u n c t i o n of l a t i t u d e and ( R e p r i n t e d w i t h p e r m i s s i o n from r e f . 3. 1984 Pergamon

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch004

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excess c o n c e n t r a t i o n s as a f u n c t i o n o f excess and t o t a l c o n c e n t r a ­ t i o n s . A t p o i n t A, where the t o t a l and excess S0^~ c o n c e n t r a t i o n s are 60 μeq/l and 18 μο^/1, r e s p e c t i v e l y , the r e l a t i v e s t a n d a r d e r r o r o f the c a l c u l a t e d excess c o n c e n t r a t i o n i s 20%. However, a t p o i n t B, the e r r o r i s 4 0 % due t o the g r e a t e r c o n t r i b u t i o n o f s e a - s a l t SO^". T h i s i l l u s t r a t e s t h a t the e r r o r s o f the c a l c u l a t e d excess c o n c e n t r a ­ t i o n are not o n l y a f u n c t i o n o f the a n a l y t i c a l u n c e r t a i n t i e s b u t a l s o o f the r e l a t i v e abundance o f the excess and s e a - s a l t components (see a l s o 4). The use o f the s i t e on Bermuda t o c o l l e c t p r e c i p i t a t i o n t h a t i s c h e m i c a l l y r e p r e s e n t a t i v e o f the marine environment assumes t h a t Bermuda i t s e l f does n o t i n f l u e n c e the amount o r c o m p o s i t i o n o f the p r e c i p i t a t i o n . Because the i s l a n d i s l o w and narrow, i t s c o n f i g u r a ­ t i o n d i d not i n f l u e n c e the amount (5.) a l t h o u g h i t c o u l d a f f e c t t h e composition. I n a n a l y s e s o f p r e c i p i t a t i o n from two s i t e s on B e r ­ muda, the s e a - s a l t and excess C a ^ components o f p r e c i p i t a t i o n were found t o i n c r e a s e as a r e s u l t o f t u r b u l e n c e a t the s e a / l a n d and a i r / l a n d i n t e r f a c e s , r e s p e c t i v e l y (Galloway, J . N.; Tokos, J . J . ; Whelpdale, D. M; Knap, A. H., U n i v e r s i t y o f V i r g i n i a , C h a r l o t t e s ­ v i l l e , u n p u b l i s h e d data). A l s o f o r samples taken from p r e c i p i t a t i o n c o l l e c t i o n s i t e s downwind o f the i s l a n d , c o n c e n t r a t i o n s o f excess SO^ and H were s l i g h t l y i n c r e a s e d by l o c a l sources. However, t h e impact o f the i s l a n d on the t o t a l excess SO^ and H c o n c e n t r a t i o n s was s m a l l r e l a t i v e t o the o f f - i s l a n d sources. WATOX a l s o used s h i p s as p l a t f o r m s t o c o l l e c t p r e c i p i t a t i o n f o r c h e m i c a l a n a l y s e s . To t e s t the impact on the p r e c i p i t a t i o n c o m p o s i ­ t i o n o f the f o s s i l f u e l s used by the s h i p s f o r p r o p u l s i o n , G a l l o w a y , Knap, and Church (6) had p r e c i p i t a t i o n samples c o l l e c t e d on the windward and l e e w a r d b r i d g e wings o f two s h i p s s a i l i n g between New York and Bermuda. They r e p o r t t h a t the samples from the windward b r i d g e wings are u n a f f e c t e d by the s h i p and are thus r e p r e s e n t a t i v e o f marine p r e c i p i t a t i o n and a p p r o p r i a t e f o r use i n a n a l y s e s o f the major c h e m i c a l c o n s t i t u e n t s sought. As p a r t o f the WATOX r e s e a r c h on the major i n o r g a n i c s p e c i e s i n wet d e p o s i t i o n i n the w e s t e r n A t l a n t i c Ocean, J i c k e l l s and h i s c o l l e a g u e s (2) sampled r a i n c o l l e c t e d on Bermuda between May 1980 and May 1981. They s t a t e t h a t t h e r e i s a s t r o n g c o r r e l a t i o n between the presence o f s u l f u r i c and n i t r i c a c i d s and the m e t e o r o l o g i c a l back t r a j e c t o r i e s o f Bermuda storm systems t o the N o r t h A m e r i c a n c o n t i n e n t . T h i s suggests the long-range t r a n s p o r t o f a c i d - r a i n p r e c u r s o r s t o Bermuda from the N o r t h A m e r i c a n c o n t i n e n t . The r e s u l t s o f the work by J i c k e l l s and h i s c o l l e a g u e s i s supported by the a n a l y s e s r e p o r t e d by G a l l o w a y , Knap, and Church (6) o f p r e c i p i ­ t a t i o n data c o l l e c t e d on b o a r d s h i p s i n the w e s t e r n A t l a n t i c Ocean. I n a d d i t i o n , the a n a l y s e s o f f o u r y e a r s o f w e t - d e p o s i t i o n data c o l l e c t e d on Bermuda by event a l s o supported these c o n c l u s i o n s ( G a l l o w a y , J . N.J A r t z , R. S.*, Keene, W. C ; C h u r c h , T. M.; Knap, A. H., U n i v e r s i t y o f V i r g i n i a , C h a r l o t t e s v i l l e , u n p u b l i s h e d data). U s i n g the NOAA ARL a i r - m a s s t r a j e c t o r y model, the WATOX r e s e a r c h e r s s t r a t i f i e d v o l u m e - w e i g h t e d averages o f p r e c i p i t a t i o n c o m p o s i t i o n by compass s e c t o r . The r e s u l t s o f these s t r a t i f i c a t i o n s f o r excess SO^~ ( F i g u r e 6) showed t h a t Bermuda was an i d e a l s a m p l i n g p l a t f o r m f o r a i r t h a t , a t t i m e s , was d i r e c t l y i m p a c t e d by anthropogenic t i c a l u n c e r t a i n t i e s . JFiguçe 5 shows «the, r e l a t i v e s t a n d a r d e r r o r o f +

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American unemicai Society Library

1155 16th St., N.W.R., el al.; In The Chemistry of Acid Rain; Johnson, ACS Symposium Series; American Chemical Society: Washington, DC, 1987. Washington, D.C. 20036

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F i g u r e 5. R e l a t i v e s t a n d a r d e r r o r o f excess s u l f a t e as a f u n c t i o n o f t o t a l and excess s u l f a t e c o n c e n t r a t i o n s (Hawley, M. E.j G a l l o w a y , J . N.; Keene, W. C, U n i v e r s i t y o f V i r g i n i a , C h a r l o t t e s v i l l e , unpublished data).

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F i g u r e 6. Volume-weighted excess SO^ c o n c e n t r a t i o n i n Bermuda p r e c i p i t a t i o n as a f u n c t i o n o f a i r - m a s s t r a j e c t o r y .

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch004

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sources i n N o r t h A m e r i c a and, a t o t h e r t i m e s , was impacted by a i r the c o m p o s i t i o n of w h i c h was more c o n t r o l l e d by marine p r o c e s s e s . Church et a l . (8.), i n p r e s e n t i n g a d d i t i o n a l i n f o r m a t i o n d e r i v e d from WATOX r e s e a r c h , r e p o r t on the ocean's i n f l u e n c e on p r e c i p i t a ­ t i o n from storms t h a t l e a v e the N o r t h American c o n t i n e n t and t r a n s i t over the w e s t e r n A t l a n t i c . They pay p a r t i c u l a r a t t e n t i o n t o t h i s o c e a n i c i n f l u e n c e on the s u l f u r and n i t r o g e n p r e c u r s o r s o f a c i d r a i n s . They f u r t h e r r e p o r t t h a t , a l t h o u g h sea s a l t c o n t r i b u t e s over h a l f (by w e i g h t ) o f the s a l t i n p r e c i p i t a t i o n a t the c o a s t and o v e r t h r e e q u a r t e r s of the s a l t i n p r e c i p i t a t i o n a t Bermuda, most s u l f a t e (90% at the c o a s t and 50% a t Bermuda) i s i n excess o f sea s a l t . S i n c e G a l l o w a y , L i k e n s and Hawley (9) have found t h a t p r e c i p i t a t i o n on Bermuda has s i g n i f i c a n t l y more excess SO^"", NO^"", and H than more remote marine a r e a s , Church and h i s c o l l e a g u e s (8) have a t t r i ­ buted these components to the long-range t r a n s p o r t o f s u l f u r and n i t r o g e n p r e c u r s o r s i n the marine t r o p o s p h e r e w i t h the s u l f u r i c - a c i d component d o m i n a t i n g . B e s i d e s u s i n g s h i p s t o c o l l e c t p r e c i p i t a t i o n t o be a n a l y z e d f o r major i o n s as r e p o r t e d by G a l l o w a y , Knap, and Church (6), WATOX-84 a l s o used s h i p s t o sample p r e c i p i t a t i o n , gases, and a e r o s o l s t o d e t e r m i n e the m e t a l , o r g a n i c , and major S and Ν 0 s p e c i e s . Church and h i s c o l l e a g u e s (10) have r e p o r t e d on a c r u i s e a c r o s s the N o r t h A t l a n t i c from Dakar, Senegal, t o Woods Hole, M a s s a c h u s e t t s , t h a t t r a n s i t e d the area o f 18°-48° N, 18°-70° W d u r i n g the s p r i n g . Dif­ f e r e n t a i r masses t h a t i n f l u e n c e the N o r t h A t l a n t i c are a n a l y z e d from s h i p b o a r d samples o f a i r c o l l e c t e d d u r i n g t h i s c r u i s e . These samples have been a n a l y z e d f o r a e r o s o l s (N, S, sea s a l t ) , gases (S02* DMS, MSA, HNO^, s y n t h e t i c o r g a n i c s ) , and p r e c i p i t a t i o n (major i n o r g a n i c i o n s , o r g a n i c a c i d s , and t r a c e elements). The r e s u l t s of these a n a l y s e s showed t h a t the c o m p o s i t i o n o f the l o w e r atmosphere over the N o r t h A t l a n t i c i s s t r o n g l y i n f l u e n c e d by c o n t i n e n t a l a i r masses. When a i r masses have o r i g i n s t h a t have passed over areas o f high emission i n North A f r i c a ( e a s t e r l i e s ) or North America (wester­ l i e s ) w i t h i n 1-2 days, the c o n c e n t r a t i o n s o f a c i d p r e c u r s o r s and s y n t h e t i c hydrocarbons i n the a i r and o f s t r o n g a c i d s , t r a c e m e t a l s , and, t o a l e s s e r e x t e n t , o r g a n i c a c i d s i n p r e c i p i t a t i o n approach those found i n e a s t e r n N o r t h America. Even o f f the n o r t h w e s t c o a s t of A f r i c a , t r a j e c t o r y a n a l y s e s l i n k the M e d i t e r r a n e a n r e g i o n w i t h a e r o s o l and p r e c i p i t a t i o n c h e m i s t r y s u g g e s t i v e o f biomass o r p e t r o ­ leum b u r n i n g . The burden o f a t m o s p h e r i c d e p o s i t i o n t o the g r e a t e r N o r t h A t l a n t i c may i n f l u e n c e the o c e a n i c s u r f a c e c h e m i s t r y of t h i s region. U s i n g t e c h n i q u e s developed f o r the s a m p l i n g and a n a l y s e s o f t r a c e m e t a l s i n marine p r e c i p i t a t i o n by Tramantano, S c u d l a r k , and C h u r c h ( E n v i r o n . S c i . T e c h n o l . . i n p r e s s ) , C h u r c h e t a l . ( i l ) and J i c k e l l s e t a l . (12) have a l s o r e p o r t e d on c o n c e n t r a t i o n measure­ m e n t s o f t h e t r a c e m e t a l s Cd, Cu, Fe, Mn, N i , Pb, V, and Zn i n wet d e p o s i t i o n a t Lewes, Delaware, and on Bermuda. The purpose o f t h i s f a c e t o f the WATOX r e s e a r c h was t o a s s e s s the sources o f , the t r a n s ­ p o r t t o , and the wet d e p o s i t i o n o f t r a c e m e t a l s t o the w e s t e r n A t l a n t i c Ocean d u r i n g nonsummer months. At t h i s t i m e o f the y e a r , t r a c e m e t a l s are l i k e l y t o be t r a n s p o r t e d by a w e s t e r l y a i r - m a s s f l o w from N o r t h A m e r i c a t o the open A t l a n t i c . Church and h i s c o l ­ leagues r e p o r t t h a t the c o n c e n t r a t i o n s and wet d e p o s i t i o n of t r a c e χ

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

T H E CHEMISTRY OF ACID RAIN

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m e t a l s are g r e a t e r i n samples from the Delaware c o a s t than from those on Bermuda, the o r d e r a t b o t h s i t e s i s s i m i l a r (Fe > Zn > Pb > Cu, Mn, N i > V > Cd). The t r a c e - m e t a l e n r i c h m e n t f a c t o r s f o r a l l m e t a l s b u t Mn (based on c r u s t a l Fe) a r e s i g n i f i c a n t l y g r e a t e r than u n i t y ; a g a i n the o r d e r i s t h e same i n samples from the Delaware c o a s t as f r o m t h o s e f r o m B e r m u d a (Cd > Pb > Z n > Cu > N i > V). T h i s evidence suggests common N o r t h A m e r i c a n sources f o r the t r a c e m e t a l s found i n w e s t e r n A t l a n t i c p r e c i p i t a t i o n as w e l l as t h e i m p o r t a n t a t m o s p h e r i c t r a n s p o r t o f t r a c e m e t a l s t o the A t l a n t i c Ocean. The c a l c u l a t i o n s u s i n g enrichment f a c t o r s from Na-based s e a - s a l t a e r o s o l i n d i c a t e t h a t the r e c y c l i n g o f t r a c e m e t a l s from the sea s u r f a c e , a l t h o u g h g e n e r a l l y not c o n s i d e r e d t o be i m p o r t a n t , c o u l d be a p o t e n t i a l l y s i g n i f i c a n t p r o c e s s c o n t r i b u t i n g t o the Mn and V e n r i c h m e n t s found i n p r e c i p i t a t i o n samples from t h e open w e s t e r n A t l a n t i c . C u t t e r and Church (13) have d e t e r m i n e d s e l e n i u m s p e c i e s i n w e s t e r n A t l a n t i c p r e c i p i t a t i o n so t h a t t h e e m i s s i o n sources u s i n g t h i s s u l f u r analogue, w h i c h i s e n r i c h e d i n f o s s i l f u e l s ( p r i m a r i l y c o a l ) , can be more e x a c t l y i d e n t i f i e d . The r e s u l t s show a c o r r e l a t i o n o f b o t h t o t a l Se and the Se IV:Se V I r a t i o w i t h i n c r e a s i n g p r o t o n s and excess s u l f u r i n p r e c i p i t a t i o n from Lewes, Delaware, and on Bermuda. T h e i r h y p o t h e s i s i s t h a t , a l t h o u g h some reduced forms (1 nM/kg) may come from background o c e a n i c e m i s s i o n s , most o x i d i z e d Se i s a r e f l e c t i o n o f f o s s i l - f u e l e m i s s i o n s from N o r t h America. As p a r t o f the WATOX program t o i n v e s t i g a t e the long-range t r a n s p o r t o f components from N o r t h A m e r i c a t o the w e s t e r n A t l a n t i c , Knap (14) has r e p o r t e d on t r a c e - o r g a n i c c o n t a m i n a n t s i n 51 samples of p r e c i p i t a t i o n c o l l e c t e d on Bermuda from 1 October 1982 t o 1 A p r i l 1983. He p r e s e n t s data on a l p h a and gamma isomers o f h e x a c h l o r o cyclohexane (HCH), c h l o r d a n e , and d i e l d r i n and n o t e s t h e presence o f PCBs and p h t h a l a t e e s t e r s i n some samples a l t h o u g h they are n o t quantified. The r a i n w a t e r c o n c e n t r a t i o n s o f t h e compounds t h a t he does q u a n t i f y v a r y and the s i z e o f events are n o t a p p a r e n t l y r e l a t e d to t h e c o n c e n t r a t i o n s , i n d i c a t i n g p o s s i b l e gas-phase scavenging. A l l t h e compounds on w h i c h Knap r e p o r t s i n d i c a t e a s e a s o n a l i t y w i t h g e n e r a l l y h i g h e r c o n c e n t r a t i o n s i n the w i n t e r months. The HCH and d i e l d r i n c o n c e n t r a t i o n s show a c o r r e l a t i o n w i t h a i r - m a s s t r a j e c t o r y — s t o r m s o r i g i n a t i n g i n the s o u t h e a s t e r n N o r t h A t l a n t i c have c o n c e n t r a t i o n s a f a c t o r o f f o u r l o w e r t h a n storms o r i g i n a t i n g west of Bermuda. Knap concludes t h a t p r e c i p i t a t i o n i s d e p o s i t i n g some p e s t i c i d e s and s y n t h e t i c o r g a n i c c h e m i c a l s t o the N o r t h A t l a n t i c Ocean. A l t h o u g h HCOOH and CH^COOH are i m p o r t a n t c h e m i c a l c o n s t i t u e n t s of c l o u d w a t e r and p r e c i p i t a t i o n , we do not y e t know t h e s o u r c e s f o r these compounds i n the atmosphere. I n a paper d i s c u s s i n g t h e i r r e s e a r c h on o r g a n i c a c i d s i n wet d e p o s i t i o n , Keene and G a l l o w a y (15) r e p o r t on 465 p r e c i p i t a t i o n samples from 14 c o n t i n e n t a l and marine s i t e s around the w o r l d t h a t were a n a l y z e d i n an a t t e m p t t o i d e n t i f y the source o f HCOOH and CH^COOH. Of these samples, 133 were c o l l e c t e d as p a r t o f the WATOX program. They a l s o r e p o r t t h a t c o n t i n e n t a l p r e c i p i t a t i o n d u r i n g growing seasons c o n t a i n s h i g h e r a b s o l u t e c o n c e n t r a t i o n s o f o r g a n i c a c i d s and h i g h e r r a t i o s o f HCOOj (HCOOH ^ + HCOO"") t o CH^OOj. (CH COOH + CHjCOO") than do marine p r e c i p i t a t i o n and c o n t i n e n t a l p r e c i p i t a t i o n d u r i n g nongrowing seasons. The c o n c e n t r a t i o n s o f BCOOrj. and CH^COO^. i n p r e c i p i t a t i o n a t most ft

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In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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l o c a t i o n s are a l s o h i g h l y c o r r e l a t e d . These r e s u l t s support the h y p o t h e s i s t h a t o r g a n i c a c i d i t y i n p r e c i p i t a t i o n may o r i g i n a t e from two major s o u r c e s : v o l a t i l e v e g e t a t i v e c o n s t i t u e n t s over c o n t i n e n t s and an unknown, weaker source i n b o t h c o n t i n e n t a l and marine regions. R e l a t i v e t o s i m i l a r r a t i o s of ECOOj. t o CH^COOrj. i n the aqueous phase, d i f f e r e n c e s i n p r e c i p i t a t i o n pH r e s u l t i n l a r g e r e g i o n a l d i f f e r e n c e s i n c a l c u l a t e d e q u i l i b r i u m vapor-phase c o n c e n t r a t i o n s . The mechanism by w h i c h p r o p o r t i o n a t e c o n c e n t r a t i o n s of HCOO-j. and CHgCOOj are m a i n t a i n e d i n the aqueous phase has not y e t been d e t e r ­ mined. Comparisons between p r e c i p i t a t i o n f r o m impacted and t h a t from remote r e g i o n s i n d i c a t e t h a t a n t h r o p o g e n i c e m i s s i o n s , a l t h o u g h pos­ s i b l y i m p o r t a n t near l a r g e p o p u l a t i o n and i n d u s t r i a l c e n t e r s , are p r o b a b l y not major s o u r c e s o f o r g a n i c a c i d s i n p r e c i p i t a t i o n over b r o a d g e o g r a p h i c r e g i o n s (£). G a l l o w a y and h i s c o l l e a g u e s ( U n i v e r ­ s i t y o f V i r g i n i a , C h a r l o t t e s v i l l e , u n p u b l i s h e d data) a l s o found t h a t the r e g i o n where a storm o r i g i n a t e d d i d not have a s i g n i f i c a n t i n f l u e n c e on the amount of o r g a n i c a c i d s d e p o s i t e d on Bermuda by precipitation. T h i s evidence s u p p o r t e d the h y p o t h e s i s t h a t o r g a n i c a c i d s found i n the remote marine t r o p o s p h e r e might have a l o c a l , p o s s i b l y b i o g e n i c , source. The Impact of N o r t h A m e r i c a n E m i s s i o n s on the C o m p o s i t i o n o f the Atmosphere over the W e s t e r n A t l a n t i c Ocean. As p a r t o f WATOX-82 (August 1982) and WATOX-83 (January and F e b r u a r y 1983), G e n e r a l Motors Research L a b o r a t o r i e s o p e r a t e d a i r - m o n i t o r i n g s i t e s on the A t l a n t i c c o a s t near Lewes, Delaware, and on the southwest c o a s t of Bermuda, 1250 km t o the s o u t h e a s t o f the Delaware s i t e . T h e i r o v e r a l l purpose was t o s t u d y the t r a n s f o r m a t i o n s of the p r i n c i p a l a c i d - p r e c i p i t a t i o n p r e c u r s o r s , Ν 0 and SO s p e c i e s , as t h e y were t r a n s p o r t e d under c o n d i t i o n s not c o m p l i c a t e d by e m i s s i o n s from l o c a l sources. Three papers have r e s u l t e d from t h i s s t u d y (16. 17. 18). I n the f i r s t paper, W o l f f and h i s c o l l e a g u e s (16) d e s c r i b e the measurements o f gas and p a r t i c u l a t e s p e c i e s found i n the Lewes samples and the c o m p o s i t i o n and sources o f s u l f a t e a e r o s o l . On the average, the t o t a l - s u s p e n d e d - p a r t i c u l a t e (TSP) c o n c e n t r a t i o n a t Lewes i s 27.9 μg/m w h i l e the PM10 (mass o f p a r t i c l e s w i t h d i a m e t e r s £ 10 |im) c o n c e n t r a t i o n i s 22.0 pg/m , o r 79% o f the TSP. The PM10 c o n s i s t s of 6.1 pg/m of c o a r s e p a r t i c l e s (CPM, d i a m e t e r s = 2.5 μιη to 10 um) and 15.9 μg/m o f f i n e p a r t i c l e s (FOM, d i a m e t e r s < 2.5 um). On a mass b a s i s , the most i m p o r t a n t c o n s t i t u e n t s of the f i n e - p a r t i c u l a t e f r a c t i o n are s u l f a t e compounds a t 50% and o r g a n i c compounds at 30%. The mean l i g h t - e x t i n c t i o n c o e f f i c i e n t c o r r e s p o n d s to a v i s u a l range o f from 18 km t o 20 km. Most o f the e x t i n c t i o n can be a t t r i b u t e d t o s u l f a t e (60%) and o r g a n i c carbon (13%). P a r t i c l e - s i z e measurements show t h a t the mass median aerodynamic d i a m e t e r f o r b o t h s p e c i e s i s 0.43 um. This i s a larger p a r t i c l e s i z e f o r carbons than has p r e v i o u s l y been r e p o r t e d and r e s u l t s i n a more e f f i c i e n t l i g h t - s c a t t e r i n g a e r o s o l . W o l f f and h i s c o l l e a g u e s (16) conclude t h a t t h e i r p r i n c i p a l - c o m p o n e n t a n a l y s e s i n d i c a t e t h a t c o a l - c o m b u s t i o n e m i s s i o n s from the m i d w e s t e r n U n i t e d S t a t e s are the most s i g n i f i c a n t source o f the s u l f a t e found i n Lewes d u r i n g the summer and w i n t e r . χ

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The second paper by W o l f f and h i s c o l l e a g u e s (17) r e p o r t s on the t r a n s f o r m a t i o n s o f a e r o s o l and gaseous s p e c i e s over the w e s t e r n A t l a n t i c Ocean d u r i n g t r a n s p o r t from N o r t h A m e r i c a . They w r i t e t h a t the c o n c e n t r a t i o n s and c o m p o s i t i o n o f f i n e - a e r o s o l and t r a c e - g a s s p e c i e s on Bermuda are governed by the type o f a i r mass i n f l u e n c i n g the i s l a n d . During i n c u r s i o n s of a i r from the n o r t h e a s t e r n U n i t e d S t a t e s , w h i c h are most f r e q u e n t d u r i n g the w i n t e r , they have found h i g h e r c o n c e n t r a t i o n s o f a n t h r o p o g e n i c a l l y d e r i v e d s p e c i e s , such as S0 "~, HN0 , S 0 , 0 , Pb, Se, and e l e m e n t a l carbon. H i g h e r S 0 ~ c o n c e n t r a t i o n s are a s s o c i a t e d w i t h h i g h e r c o n c e n t r a t i o n s o f the c o a l - b u r n i n g t r a c e r Se and of HNO^ and 0 · The l a t t e r two r e l a t i o n ­ s h i p s suggest a p h o t o c h e m i c a l r o l e and an a s s o c i a t i o n of HN0 w i t h c o a l b u r n i n g . S 0 i s s t r o n g l y a s s o c i a t e d w i t h the o i l - b u r n i n g t r a c e r , V. W o l f f and h i s c o l l e a g u e s r e p o r t i n t r u s i o n s o f a i r from the n o r t h e a s t e r n U n i t e d S t a t e s d u r i n g the F e b r u a r y 1983 I n t e n s i v e (WATOX-83). However, t h e r e were a l s o some i n t r u s i o n s d u r i n g the August 1982 I n t e n s i v e (WATOX-82) a l t h o u g h the summer was dominated by a s o u t h e a s t e r l y f l o w c o n t a i n i n g h i g h c o n c e n t r a t i o n s o f f i n e c r u s t a l m a t e r i a l , p r o b a b l y from the Sahara Desert. A l t h o u g h W o l f f e t a l . (17) f i n d t h a t t h e r e are more i n t r u s i o n s from N o r t h A m e r i c a d u r i n g the summer, they a l s o f i n d t h a t t h e r e are some d u r i n g the w i n t e r . T h e i r r e s e a r c h shows t h a t days w i t h a s o u t h e a s t e r l y a i r f l o w are a s s o c i a t e d w i t h h i g h l e v e l s of S i , T i , K, Fe, Ca, and Mn as w e l l as the l o w e s t e n r i c h m e n t f a c t o r s f o r a l l anthropogenic s p e c i e s . The e n r i c h m e n t f a c t o r s f o r the c r u s t a l spe­ c i e s are g e n e r a l l y independent of w i n d d i r e c t i o n f o r K. They go on t o suggest t h a t woodburning i n the n o r t h e a s t e r n U n i t e d S t a t e s may be the source of the h i g h e r Κ e n r i c h m e n t f a c t o r s found d u r i n g the w i n t e r . They used t h e i r Bermuda Ν 0 and S 0 data t o make a rough e s t i m a t e of the f l u x e s of these s p e c i e s i n the l a s t 1500 km from N o r t h A m e r i c a t o a n o r t h / s o u t h l i n e 1250 km e a s t of the U n i t e d S t a t e s , w h i c h passes through Bermuda. S i g n i f i c a n t amounts o f b o t h Ν Ο and S 0 advected o f f the E a s t Coast reached Bermuda and the f l u x e s appear t o be c o n s i s t e n t w i t h the f l u x e s c a l c u l a t e d by G a l l o ­ way e t a l . (3.). I n the t h i r d paper t h a t r e s u l t e d from the WATOX r e s e a r c h i n w h i c h the G e n e r a l Motors R e s e a r c h L a b o r a t o r i e s took p a r t , G i b s o n , Korsog, and W o l f f (18) compare the a t m o s p h e r i c c o n c e n t r a t i o n s o f t r a c e - o r g a n i c s p e c i e s from samples a t Lewes, Delaware, t o those from Bermuda. T h e i r purpose was t o a s c e r t a i n the t r a n s f o r m a t i o n r e a c ­ t i o n s of n i t r o a r o m a t i c , p o l y c y c l i c o r g a n i c m a t t e r (POM), and benso(a)pyrene (BaP) d u r i n g t r a n s p o r t from N o r t h America. They r e p o r t t h a t the r a t i o s of 1 - n i t r o p y r e n e and h y d r o x y n i t r o p y r e n e s t o i n e r t marker s p e c i e s ( f i n e - p a r t i c u l e l e a d , s e l e n i u m , and e l e m e n t a l carbon) are c o n s i d e r a b l y h i g h e r at a remote s i t e on Bermuda than i n D e l a ­ ware. G i b s o n and h i s c o l l e a g u e s suggest t h a t these n i t r o a r o m a t i c POM are formed i n a t m o s p h e r i c r e a c t i o n s . The r a t i o of BaP t o the marker s p e c i e s i s s i m i l a r at the two s i t e s , w h i c h does not r e f l e c t the expected l o s s o f BaP i n a t m o s p h e r i c p h o t o c h e m i c a l r e a c t i o n s . 4

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The I n f l u e n c e of N o r t h A m e r i c a n E m i s s i o n s on the S u r f a c e Ocean. The i n c r e a s e d d e p o s i t i o n of f i x e d n i t r o g e n t o an ocean has the p o t e n t i a l t o a f f e c t the p r i m a r y p r o d u c t i v i t y i n the s u r f a c e of t h a t ocean. Knap and h i s c o l l e a g u e s (19), i n t h e i r WATOX-related r e s e a r c h on the

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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i n f l u e n c e of i n o r g a n i c f i x e d n i t r o g e n ( n i t r a t e and ammonium) on the s u r f a c e ocean, a n a l y z e d two y e a r s of p r e c i p i t a t i o n data f o r n i t r a t e and ammonium c o n c e n t r a t i o n s . They conclude t h a t , on the average, p r e c i p i t a t i o n plays only a minor part i n p r o v i d i n g inorganic f i x e d n i t r o g e n f o r p r i m a r y p r o d u c t i v i t y i n o l i g o t r o p h i c ocean areas. They b e l i e v e t h i s t o be t r u e i n s p i t e of the c o n s i d e r a b l e i n c r e a s e of n i t r a t e from anthropogenic sources found i n r a i n w a t e r over the p a s t 100 y e a r s . However, p r e c i p i t a t i o n i s an e p i s o d i c p r o c e s s and the d e p o s i t i o n r a t e of f i x e d n i t r o g e n i s not the same f o r a l l events. Of the t o t a l i n o r g a n i c f i x e d n i t r o g e n , 40% i s wet d e p o s i t e d by o n l y 11% of the 126 events e v a l u a t e d by Knap and h i s c o l l e a g u e s . Based on t h i s , they s p e c u l a t e d t h a t o c c a s i o n a l " h o t " events may be i m p o r t a n t on s h o r t t i m e (about one day) and space (a few hundred kilometers) scales. The WATOX data on a t m o s p h e r i c i n p u t s of t r a c e m e t a l s i n t o and out of the Sargasso Sea i n the N o r t h A t l a n t i c have been used, i n a s s o c i a t i o n w i t h sediment r e c y c l i n g r a t e s , t o generate a p p r o x i m a t e l y s e l f - c o n s i s t e n t budgets f o r a range of t r a c e elements i n the S a r ­ gasso Sea. Only f o r A l , Fe, Mn, and V are a d d i t i o n a l l a t e r a l o c e a n i c i n p u t s n e c e s s a r y t o c l o s e such budgets f o r the w e s t e r n A t l a n t i c . Thus f o r Cu, N i , Zn, Pb, and C d — a l l of w h i c h are en­ r i c h e d on a t m o s p h e r i c p a r t i c u l a t e s — a t m o s p h e r i c d e p o s i t i o n r e p r e ­ sents the l a r g e s t i n p u t to the w e s t e r n A t l a n t i c . Much of the Cd, N, and Zn i s r e c y c l e d along w i t h n u t r i e n t s and these are then l a r g e l y e x p o r t e d from the w e s t e r n A t l a n t i c . Sedimentary r e c y c l i n g of the Cu may account f o r much of the t o t a l Cu f l u x t o the sediments as measured w i t h sediment t r a p s . J i c k e l l s and h i s c o l l e a g u e s (20) conclude t h a t , i f the a t m o s p h e r i c c o n c e n t r a t i o n s of Cd, Cu, N i , Pb, and Zn are c u r r e n t l y e n r i c h e d i n w e s t e r n A t l a n t i c p r e c i p i t a t i o n by anthropogenic p r o c e s s e s , then the a t m o s p h e r i c i n p u t t o the Sargasso Sea must have i n c r e a s e d by as much as two o r d e r s o f magnitude s i n c e p r e h i s t o r i c times. Knap, B i n k l e y , and Dueser (21) used the WATOX d a t a on atmos­ p h e r i c i n p u t s of t r a c e o r g a n i c s t o the s u r f a c e of the Sargasso Sea i n c o n j u n c t i o n w i t h data f r o m sediment t r a p s t o i n v e s t i g a t e the f l u x of contaminant substances t o the deep Sargasso Sea. They had a sediment t r a p moored 3200 m below the ocean s u r f a c e f o r two y e a r s t o study the c o n c e n t r a t i o n s o f p o l y c h l o r i n a t e d byphenyls (PCBs), c h l o r danes, and d i e l d r i n . These r e s e a r c h e r s r e p o r t a deep-sea f l u x of PCBs of 1.6 μg/m^ y r , w h i c h i s s u r p r i s i n g l y s i m i l a r t o the atmos­ p h e r i c f l u x of these compounds of 1.6-3.1 μg/m^ y r c a l c u l a t e d from the measured c o n c e n t r a t i o n s of the WATOX-82. They conclude t h a t , because t h e i r data c o r r e l a t e w e l l w i t h the data on o r g a n i c carbon, the d e p o s i t i o n mechanism t o the sediment i s p r o b a b l y a s s o c i a t e d w i t h biogenic particles. Beyond the Western A t l a n t i c Ocean. Whelpdale and h i s c o l l e a g u e s ( W h e l p d a l e , D.M.; E l i a s s e n , Α.; G a l l o w a y , J . N.; D o v l a n d , H.; M i l l e r , J. M. T e l l u s , i n p r e s s ) have examined the t r a n s p o r t of N o r t h A m e r i c a n s u l f u r e m i s s i o n s a c r o s s the n o r t h A t l a n t i c Ocean t o Europe. I n a r e v i e w of a v a i l a b l e p r e c i p i t a t i o n - s u l f a t e data from the n o r t h A t l a n t i c and a d j a c e n t c o a s t a l r e g i o n s , they r e p o r t a c o n c e n t r a t i o n f i e l d c o n s i s t e n t w i t h known source d i s t r i b u t i o n s and m e t e o r o l o g i c a l f a c t o r s . The excess s u l f a t e c o n c e n t r a t i o n o f marine background

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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p r e c i p i t a t i o n i s 6-8 μβς/1 and excess [SO^ ] decreases from >50 μeq/l w i t h o f f s h o r e f l o w s a t the N o r t h A m e r i c a n e a s t c o a s t and t o 8-15 μβς/1 w i t h onshore f l o w s a t the European west coast. T h i s decay i s c o n s i s t e n t w i t h a d i s t a n c e c o n s t a n t o f 2400 km and a r e s i ­ dence t i m e o f a p p r o x i m a t e l y 80 hours and, i n t u r n , c o r r e s p o n d s t o a t r a n s - A t l a n t i c f l u x o f a n t h r o p o g e n i c s u l f u r o f 0.3-0.4 Tg/yr. Whelpdale e t a l . r e p o r t f u r t h e r on a second independent e s t i m a t e based on the a p p l i c a t i o n o f a c l i m a t o l o g i c a l d i s p e r s i o n model t h a t accounts f o r l o n g - t e r m average d i f f u s i o n , wet and d r y d e p o s i t i o n , and t o S 0 ~ t r a n s f o r m a t i o n . U s i n g t h i s model, they c a l c u l a t e a f l u x o f N o r t h A m e r i c a n a n t h r o p o g e n i c s u l f u r a t t h e European west c o a s t o f 0.2 Tg/yr, w h i c h agrees w i t h t h e f i r s t e s t i m a t e . At t h e d i s t a n c e o f t h e European west c o a s t , N o r t h A m e r i c a n a n t h r o p o g e n i c e m i s s i o n s account f o r a p p r o x i m a t e l y 4 μeq/l i n p r e c i ­ pitation. T h i s i s l e s s t h a n t h e m a r i n e background o f 6-8 μβς/1 and much l e s s t h a n t h e annual average excess [SO^] v a l u e o f a p p r o x i ­ m a t e l y 30 μeq S / l a p p r o p r i a t e f o r much o f the c o a s t a l r e g i o n . Whelp­ d a l e e t a l . c o n c l u d e , t h e r e f o r e , t h a t , on the average, the amount o f N o r t h A m e r i c a n a n t h r o p o g e n i c s u l f u r r e a c h i n g Europe i s s m a l l com­ p a r e d t o t h a t from o t h e r s o u r c e s .

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch004

4

Summary Over t h e p a s t few y e a r s , p a r t i c i p a n t s i n the WATOX program have been a b l e t o e s t i m a t e the e a s t w a r d a d v e c t i o n o f s u l f u r , n i t r o g e n , and t r a c e - m e t a l and t r a c e - o r g a n i c s p e c i e s from N o r t h A m e r i c a as w e l l as t h e i r impact on t h e p r e c i p i t a t i o n and s u r f a c e w a t e r s o f the w e s t e r n A t l a n t i c Ocean. The data base c o m p i l e d by the WATOX c o n s o r t i u m , a l t h o u g h e x t e n s i v e , i s s m a l l r e l a t i v e t o t h e s i z e o f the r e g i o n and the degree o f s p a t i a l and t e m p o r a l v a r i a b i l i t y o f t h e measured components. Thus, r e s e a r c h on the impact o f N o r t h A m e r i c a n e m i s ­ s i o n s on the atmosphere and on t h e s u r f a c e w a t e r s o f the w e s t e r n A t l a n t i c Ocean c o n t i n u e s . We a r e s t i l l u s i n g a i r c r a f t , i s l a n d s , and s h i p s t o i n v e s t i g a t e the changes i n t h e N o r t h A m e r i c a n plume as i t t r a n s i t s the A t l a n t i c Ocean, the a t m o s p h e r i c t r a n s p o r t o f m a t e r i a l s a c r o s s t h e A t l a n t i c , and the impact o f a t m o s p h e r i c d e p o s i t i o n i n t h e surface ocean. Acknowledgments T h i s paper i s a c o n t r i b u t i o n from t h e Western A t l a n t i c Ocean E x p e r i m e n t (WATOX) and the Bermuda B i o l o g i c a l S t a t i o n . We g r a t e ­ f u l l y acknowledge t h e support o f the N a t i o n a l Oceanic and Atmos­ p h e r i c A d m i n i s t r a t i o n o f t h e U n i t e d S t a t e s , the Canadian A t m o s p h e r i c Environment S e r v i c e , and the Bermuda government. We a l s o thank W i l l i a m Keene and A l e x Pszenny f o r t h e i r c o n s t r u c t i v e comments. We acknowledge and a p p r e c i a t e t h e t y p i n g s e r v i c e s o f Brenda M o r r i s and the e d i t o r i a l t a l e n t s o f M a r y - S c o t t M a r s t o n .

Literature Cited 1. Miller, J . M.; Harris, J . M. Atmos. Environ. 1985, 19, 409-414. 2. Whelpdale, D. M.; Low, T. B.; Kolomeychuk, R. J. Atmos. Environ. 1984, 18, 1311-1327.

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch004

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GALLOWAY ET AL.

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3. Galloway, J. N.; Whelpdale, D. M.; Wolff, G. T. Atmos. Environ. 1984, 18, 2595-2608. 4. Keene, W. C.; Pszenny, A. A. P.; Galloway, J. N.; Hawley, M. E. J . Geophys. Res. 1986, 91, 6647-6658. 5. Nemkosky, M. J., Jr. Local Area Forecaster's Handbook, Naval Oceanographie Command Detachments: Bermuda, 1980. 6. Galloway, J. N.; Knap, A. H.; Church, T. M. J. Geoohvs. Res. 1983, 88, 10,859-10,864. 7. Jickells, T.; Knap, Α.; Chprch, T.; Galloway, J.; Miller, J. Nature 1982, 297, 55-57. 8. Church, T. M.; Galloway, J. N.; Jickells, T. D.; Knap, A. H. J. GeophYs. Res. 1982, 87, 11,013-11,018. 9. Galloway, J. N.; Likens, G. E.; Hawley, M. E. Science 1984, 226. 829. 10. Church, T. M.; Whelpdale, D. M.; Andreae, A. O.; Galloway, J. N.; Keene, W. C.; Knap, A. H.; Tokos, J. J. EOS 1986, 67, 896. 11. Church, T. M.; Tramantano, J. M.; Scudlark, J. R.; Jickells, T. D.; Tokos, J. J.; Knap, A. H.; Galloway, J. N. Atmos. Environ. 1984, 18, 2657-2664. 12. Jickells, T. D.; Knap, A. H.; Church, T. M. J. Geophvs. Res. 1984, 89, 1423-1428. 13. Cutter, G.; Church, T. Nature 1986, 322, 720-722. 14. Knap, A. H. EOS 1985, 66, 833. 15. Keene, W. C.; Galloway, J. N. J. Geophvs. Res. 1986, 91, 14,466. 16. Wolff, T. G.; Kelly, Ν. Α.; Ferman, Μ. Α.; Ruthkosky, M. S.', Stroup, D. P.; Korsog, P. E. J. Air Pollut. Control Assoc. 1986, 36* 585-591. 17. Wolff, G. Τ.·, Ruthkosky, M. S.; Stroup, D. P.; Korsog, P. E.; Ferman, Μ. Α.; Stedman, D. H.; Wendel, G. J. Atmos. Environ. 1986, 20, 1229-1239. 18. Gibson, T. L.; Korsog, P. E.; Wolff, G. T. Atmos. Environ. 1986, 20, 1575-1578. 19. Knap, A.î Jickells, T.; Pszenny, Α.; Galloway, J. Nature 1986, 320. 158-160. 20. Jickells, T. D.; Church, T. M.; Dueser, W. G.; Knap, A. H.; Tramantano, J. M. Int. Conf. Heavy Metals in Environment, Vol. 2, 1986, pp. 347-349. 21. Knap, A. H.; Binkley, K. S.; Dueser, W. G. Nature 1986, 319, 572-574. RECEIVED

March 14,

1987

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Chapter 5

Hybrid Receptor Models C. W. Lewis and R. K. Stevens

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch005

Atmospheric Sciences Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711

A hybrid receptor model is defined as a specified mathematical procedure which uses not only the ambient species concentration measurements that form the input data for a pure receptor model, but in addition source emission rates or atmospheric dispersion or transformation information characteristic of dispersion models. By utilizing more information hybrid receptor modeling promises improved source apportionment estimates or, more fundamentally, consideration of problems that are inaccessible in terms of classical receptor modeling. Several examples of hybrid receptor modeling are reviewed, emphasizing the great variety in possible approaches, and in the choice of input versus output quantities. A simple illustration is given of a hybrid receptor model applied to the comprehensive ambient-source-meteorological data base collected at Deep Creek Lake, Maryland during summer 1983. A hybrid receptor model is any procedure for estimating the sources of ambient a i r pollutants at a receptor s i t e , which makes use of both receptor and dispersion (source) modeling approaches. Thus, not only are the ambient species measurements which form the input data for a pure receptor model used, but also source emission rates or atmospheric dispersion or transformation information c h a r a c t e r i s t i c of dispersion models. By exp l o i t i n g simultaneously the strengths of the two complementary approaches we expect to minimize t h e i r individual weaknesses. The natural domain of hybrid receptor models is in the treatment of reactive a i r pollutants, such as p a r t i c u l a r organics, S02/sulfate and N O / n i t r a t e . In the (non-exhaustive) review of existing hybrid receptor models which follows we hope to i l l u s t r a t e the variety of possible approaches, and the f l e x i b i l i t y in the choice of input data versus calculated outputs, depending on what information is available. Finally, a comprehensive ambient-source meteorological data base collected at Deep Creek Lake, Maryland, x

This chapter is not subject to U.S. copyright. Published 1987, American Chemical Society

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

5.

LEWIS AND STEVENS

Hybrid Receptor Models

during summer 1983 is described and used in a simple application of one hybrid receptor model. Hybrid Receptor Model Examples

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch005

Reactive Organic Chemical Mass Balance (Friedlander). In the original formulation of the CMB receptor model (1) i t was recog­ nized that the fractional amounts of various chemical species emitted by a source are not necessarily conserved during the transport of the species to the receptor s i t e . This could occur through both physical ( d i f f e r e n t i a l dispersion or deposition) or chemical (removal due to atmospheric reactions) processes. This p o s s i b i l i t y was acknowledged by writing the CMB equations in the form c

i

I ij

=

a

a

J

ij j

(*)

s

where C-j is the concentration of species i measured at the recep­ tor s i t e , a-jj ( a) r i g h t o r d i n a t e a r e chosen so t h a t the same c o o r d i n a t e on each s c a l e r e p r e s e n t s the c o n d i t i o n o f phase e q u i l i b r i u m . D e p a r t u r e from the u n i f o r m p r o f i l e a t the "bulk' ( r =oo) v a l u e r e p r e s e n t s the i n a b i l i t y o f mass t r a n s p o r t to m a i n t a i n the reagent concen­ t r a t i o n as the reagent i s consumed by aqueous-phase r e a c t i o n . (Reproduced w i t h p e r m i s s i o n from Ref. 28. C o p y r i g h t 1986 Lewis P u b l i s h e r s , I n c . ) 1

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch008

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f o r such treatment are o u t l i n e d i n Ref. (Γ7). Alternatively, i f m a s s - t r a n s p o r t l i m i t a t i o n i s a b s e n t , model e v a l u a t i o n s would be greatly simplified. From the above o u t l i n e , the m a s s - t r a n s p o r t problem i s seen to c o n s i s t of c o u p l e d boundary v a l u e problems ( i n gas and aqueous phase) w i t h an i n t e r f a c i a l boundary c o n d i t i o n . C l o u d d r o p l e t s are s u f f i c i e n t l y s p a r s e ( t y p i c a l s e p a r a t i o n i s of o r d e r 100 drop r a d i i ) t h a t drops may be t r e a t e d as independent. For c l o u d d r o p l e t s ( d i a m e t e r ~5 ym t o ~40 \im) both gas- and aqueous-phase masst r a n s p o r t are dominated by m o l e c u l a r d i f f u s i o n . The f l u x a c r o s s the i n t e r f a c e i s g i v e n by the m o l e c u l a r c o l l i s i o n r a t e times an accommodation c o e f f i c i e n t (a < 1) t h a t r e p r e s e n t s the f r a c t i o n of c o l l i s i o n s l e a d i n g to t r a n s f e r of m a t e r i a l a c r o s s the i n t e r f a c e . Magnitudes of mass-accommodation c o e f f i c i e n t s a r e n o t w e l l known g e n e r a l l y and t h i s h o l d s e s p e c i a l l y i n the case of s o l u t e gases upon aqueous s o l u t i o n s . For t h i s reason α i s t r e a t e d as an a d j u s t ­ a b l e parameter, and we examine the v a l u e s of α f o r which i n t e r f a c i a l mass-transport l i m i t a t i o n i s s i g n i f i c a n t . Values of α i n the range 10~6 to 1 have been assumed i n r e c e n t s t u d i e s ( e . g . , 18). As noted below, r e c e n t e x p e r i m e n t a l s t u d i e s have y i e l d e d measurements of t h i s i m p o r t a n t q u a n t i t y f o r systems of i n t e r e s t i n cloud chemistry. S o l u t i o n of the coupled m a s s - t r a n s p o r t and r e a c t i o n problem f o r a r b i t r a r y c h e m i c a l k i n e t i c r a t e laws i s p o s s i b l e o n l y by numer­ i c a l methods. The problem i s g r e a t l y s i m p l i f i e d by d e c o u p l i n g the time dependence of m a s s - t r a n s p o r t from t h a t of c h e m i c a l k i n e t i c s ; the m a s s - t r a n s p o r t s o l u t i o n s r a p i d l y r e l a x to a pseudo steady s t a t e i n view of the s m a l l dimensions of the system ( 1 9 ) . The gas-phase d i f f u s i o n problem may be s o l v e d p a r a m e t r i c a l l y i n terms of the net f l u x i n t o the drop. I n the case of f i r s t - o r d e r or p s e u d o - f i r s t o r d e r c h e m i c a l k i n e t i c s an a n a l y t i c a l s o l u t i o n to the problem of coupled aqueous-phase d i f f u s i o n and r e a c t i o n i s a v a i l a b l e ( 1 9 ) . These s o l u t i o n s , t o g e t h e r w i t h the i n t e r f a c i a l boundary c o n d i t i o n , s p e c i f y the c o n c e n t r a t i o n p r o f i l e of the reagent gas. I n t u r n the e x t e n t of d e p a r t u r e of the r e a c t i o n r a t e from t h a t c o r r e s p o n d i n g to s a t u r a t i o n may be determined. F i n a l l y c r i t e r i a have been developed (17,19) by which i t may be a s c e r t a i n e d whether or not there i s a p p r e c i a b l e ( e . g . , 10%) l i m i t a t i o n to the r a t e of r e a c t i o n as a consequence of the f i n i t e r a t e of mass t r a n s p o r t . These c r i t e r i a are l i s t e d i n T a b l e 1. E x a m i n a t i o n of Mass-Transport L i m i t a t i o n . The a v a i l a b i l i t y of c r i t e r i a f o r m a s s - t r a n s p o r t l i m i t a t i o n a l l o w s e x a m i n a t i o n of the importance of such l i m i t a t i o n In r e p r e s e n t a t i v e s i t u a t i o n s . This i s c o n v e n i e n t l y a c h i e v e d by means of graphs, as shown i n F i g u r e s 9 and 10 f o r the S ( l V ) - 0 3 S(IV)-H202 r e a c t i o n s , r e s p e c t i v e l y . Here the i n e q u a l i t i e s i n T a b l e 1 are r e p r e s e n t e d as l i n e s i n a plane whose c o o r d i n a t e s are l o g k d ) and l o g H ( o r l o g H*). Each of the s e v e r a l c r i t e r i a thus appears as a s t r a i g h t l i n e i n t h i s p l a n e . The sense of the f i g u r e i s t h a t m a s s - t r a n s p o r t l i m i t a ­ t i o n i s absent ( i . e . , 1 0 " " 3 , l i t t l e o r no m a s s - t r a n s p o r t l i m i t a t i o n i s i n d i ­ c a t e d f o r most c o n d i t i o n s . Accommodation C o e f f i c i e n t Measurements. R e c e n t l y Lee and Tang ( 2 0 ) have p r e s e n t e d measurements o f the accommodation c o e f f i c i e n t s o f 0 ^ and S O 2 on aqueous s o l u t i o n . I n the case of O 3 a v a l u e of 5 χ 1 0 " ^ i s r e p o r t e d . I t i s seen by e x a m i n a t i o n o f F i g u r e 9 t h a t an accom­ modation c o e f f i c i e n t of t h i s magnitude i s w e l l above the v a l u e t h a t would l e a d t o i n t e r f a c i a l m a s s - t r a n s p o r t l i m i t a t i o n under c i r c u m ­ s t a n c e s of i n t e r e s t , i n t e r s e c t i n g the O 3 l i n e o n l y a t pH > 6 , w e l l

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

8.

Aqueous-Phase Reactions in Clouds

SCHWARTZ

105

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beyond the onset of aqueous-phase m a s s - t r a n s p o r t l i m i t a t i o n . For S O 2 o n l y a lower l i m i t to the accommodation c o e f f i c i e n t has been d e t e r m i n e d , v i z . , α ^ 2 χ 10"3. However even t h i s v a l u e i s s u f f i ­ c i e n t l y g r e a t to r u l e out m a s s - t r a n s p o r t l i m i t a t i o n under most c i r c u m s t a n c e s of i n t e r e s t . Thus, the S(IV) curve i n F i g u r e 9 ( O 3 r e a c t i o n ) c r o s s e s the α = 2 χ 10"3 i n t e r f a c i a l bound o n l y a t pH 5.7, and i n F i g u r e 10 ( H 2 O 2 r e a c t i o n ) l i e s e n t i r e l y below t h i s bound. E v i d e n t l y no i n f o r m a t i o n i s a v a i l a b l e p e r t i n e n t to the massaccommodation c o e f f i c i e n t of H 2 O 2 on aqueous s o l u t i o n t h a t would p e r m i t assessment of the r o l e of i n t e r f a c i a l m a s s - t r a n s p o r t l i m i t a ­ t i o n of t h i s important r e a c t i o n . N i t r o g e n Oxide R e a c t i o n s . E x a m i n a t i o n of p o s s i b l e aqueous-phase r e a c t i o n s of n i t r o g e n d i o x i d e and p e r o x y a c e t y l n i t r a t e has r e v e a l e d no r e a c t i o n s of importance to c l o u d c h e m i s t r y (21,22). This s i t u a ­ t i o n i s a consequence of the low s o l u b i l i t i e s and/or low r e a c t i v i ­ t i e s of these gases w i t h substances expected to be p r e s e n t i n c l o u d w a t e r , a l t h o u g h s t u d i e s w i t h a c t u a l p r e c i p i t a t i o n samples would be v a l u a b l e i n c o n f i r m i n g t h i s s u p p o s i t i o n . NO2 has been shown (23) to r e a c t w i t h d i s s o l v e d S ( I V ) , but the d e t a i l s of the mechanism and r a t e of t h i s r e a c t i o n remain to be e l u c i d a t e d . An i n - c l o u d r e a c t i o n of importance a t n i g h t and p o s s i b l e a l s o d u r i n g the day i s the uptake of n i t r i c a c i d by gas-phase r e a c t i o n s NO2

+

NO3

O3 +

—> NO2

NO3 —>

+

O2

N2O5

f o l l o w e d by uptake of N 2 O 5 and/or N O 3 by c l o u d w a t e r and aqueousphase r e a c t i o n (24, 25). Q u a n t i t a t i v e e v a l u a t i o n of the r a t e of t h i s p r o c e s s a w a i t s d e t e r m i n a t i o n of the s o l u b i l i t y and r e a c t i v i t y o f N O 3 and N 2 O 5 as w e l l as d e t e r m i n a t i o n of mass-accommodation coefficients. F i e l d Measurements F i e l d measurements, i n a d d i t i o n to p r o v i d i n g c o n c e n t r a t i o n s and o t h e r s i t u a t i o n a l data n e c e s s a r y f o r k i n e t i c e v a l u a t i o n s , a l s o a l l o w i n f e r e n c e s to be drawn about the o c c u r r e n c e of chemical r e a c ­ tions i n clouds. Such i n f e r e n c e s i n c l u d e the f o l l o w i n g : 1. G r e a t e r a c i d i t y of cloudwater (measured by the r a t i o [ H ] / ( [ N 0 - ] + 2 [ S 0 4 ] ) or [H+]/[NH +]) than i n c o r r e s p o n d i n g c l e a r - a i r (26) i s i n d i c a t i v e of the o c c u r r e n c e of a c i d forma­ t i o n by i n - c l o u d r e a c t i o n . 2. G r e a t e r f r a c t i o n a l c o n v e r s i o n of S O 2 to c l o u d w a t e r s u l f a t e than o f N O 2 to c l o u d w a t e r n i t r a t e (27) i s i n d i c a t i v e of more e x t e n ­ s i v e i n - c l o u d o x i d a t i o n of S O 2 than of N O 2 . 3. An apparent mutual e x c l u s i v i t y of gas-phase S O 2 and aqueous H 2 O 2 observed i n n o n - p r e c i p i t a t i n g l i q u i d - w a t e r s t r a t i f o r m c l o u d s , i . e . , one or the o t h e r s p e c i e s p r e s e n t but never b o t h a t a p p r e c i a b l e c o n c e n t r a t i o n s ( 2 7 ) , i s c o n s i s t e n t w i t h the H202~S(IV) r e a c t i o n proceeding to c o m p l e t i o n i n such c l o u d s . These i n f e r e n c e s from f i e l d measurements p r o v i d e support f o r the a p p l i c a b i l i t y of e v a l u a t i o n s of c l o u d c h e m i s t r y based upon l a b o r a ­ tory studies. +

=

3

4

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

106

THE CHEMISTRY OF ACID RAIN

Conclusions Techniques a r e a t hand to e v a l u a t e the r a t e s of aqueous-phase a c i d formation reactions i n clouds. Such e v a l u a t i o n s i n d i c a t e t h a t o x i ­ d a t i o n of S O 2 by H 2 O 2 and O 3 can be i m p o r t a n t i n - c l o u d r e a c t i o n s f o r assumed r e p r e s e n t a t i v e reagent c o n c e n t r a t i o n s and o t h e r c o n d i ­ t i o n s . R a p i d aqueous-phase r e a c t i o n s do n o t appear to be i n d i c a t e d f o r o x i d a t i o n o f n i t r o g e n o x i d e s to n i t r i c a c i d .

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch008

Acknowledgments T h i s work was supported by the N a t i o n a l A c i d P r e c i p i t a t i o n Assess­ ment program through the PRECP p r o j e c t funded by the U.S. Depart­ ment o f Energy and was performed under the a u s p i c e s of the U n i t e d S t a t e s Department of Energy under C o n t r a c t No. DE-AC02-76CH00016.

Literature Cited 1. Calvert, J . G.; Stockwell, W. R. Acid generation in the tro­ posphere by gas-phase chemistry. Environ. Sci. Technol. 1983, 17, 428A-442A. 2. Calvert, J. G.; Stockwell, W. R. Mechanism and rates of the gas-phase oxidations of sulfur dioxide and nitrogen oxides in the atmosphere. In SO2, NO and NO2 Oxidation Mechanisms: Atmo­ spheric Considerations; Calvert, J . G., Ed.; Butterworth: Boston, 1984; pp. 1-62. 3. Twomey, S. Atmospheric Aerosols; Elsevier: Amsterdam, 1977; pp. 143-164. 4. Levine, S. Z.; Schwartz, S. E. In-cloud and below-cloud scavenging of nitric acid vapor. Atmos. Environ. 1982, 16, 1725-1734. 5. For a discussion of cloud microphysical properties see e.g. Pruppacher, H. R. and Klett, J . D. Microphysics of Clouds and Precipitation; D. Reidel: Dordrecht, 1978. 6. Ho, W. W.; Hidy, G. M.; Govan, R. M. Microwave measurements of the liquid water content of atmospheric aerosols. In Advances in Environmental Science and Technology; Hidy, G. M. et al., Eds.; Wiley: New York, 1980; Vol. 9, pp. 215-236. 7. Schwartz, S. E.; White, W. H. Kinetics of reactive dissolu­ tion of nitrogen oxides into aqueous solution. In Advances in Environmental Science and Technology; Schwartz, S. Ε., Ed.; Wiley: New York, 1983: Vol. 12, pp. 1-116. 8. Penkett, S. Α.; Jones, B. M. R.; Brice, Κ. Α.; Eggleton, A. E. J. The importance of atmospheric ozone and hydrogen per­ oxide in oxidising sulphur dioxide in cloud and rainwater. Atmos. Environ. 1979, 13, 123-137. 9. Erickson, R. E.; Yates, L. M.; Clark, R. L.; McEwen, D. The reaction of sulfur dioxide with ozone in water and its possi­ ble atmospheric significance. Atmos. Environ. 1977 , 11, 813-817. 10. Schwartz, S. E. Gas-Aqueous Reactions of Sulfur and Nitrogen Oxides in Liquid-Water Clouds. In SO , NO and NO2 Oxidation Mechanisms: Atmospheric Considerations; Calvert, J . G., Ed.; Butterworth: Boston, 1984; pp. 173-208. 2

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

8.

SCHWARTZ

11.

12.

13.

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch008

14.

15. 16.

17.

18. 19.

20.

21. 22.

23.

24.

Aqueous-Phase Reactions in Clouds

107

For a recent review see Calvert, J . G.; Lazrus, Α.; Kok, G. L.; Heikes, B. G.; Walega, J. G.; Lind, J . ; Cantrell, C. A. Chemical mechanisms of acid generation in the troposphere. Nature 1985, 317, 27-38. Kok, G. L.; Heikes B. G.; Lazrus, A. L. Gas and aqueous phase measurements of hydrogen peroxide. Symposium on Acid Rain; I. Sources and Atmospheric Processes, Division of Petroleum Chemistry, Inc.; American Chemical Society, preprints, 1986, Vol. 31, No. 2, pp. 541-544. Heikes, B. G.; Kok, G. L.; Lazrus, A. L.; Walega, J. G. Η2Ο2, O3 and SO2 measurements in the lower troposphere over the eastern U.S.A. during fall. J. Geophys. Res. 1987, in press. Tanner, R. L . ; Markovits, G. Y.; Ferreri, Ε. M.; Kelly, T. J. Sampling and determination of gas-phase hydrogen peroxide fol­ lowing removal of ozone by gas-phase reaction with nitric oxide. Anal. Chem. 1986, 58 1857-1865. Kelly, T. J.; Daum, P. H.; Schwartz, S. E. Measurements of peroxides in cloudwater and rain. J. Geophys. Res. 1985, 90, 7861-7871. Lee, Y.-N.; Shen, J.; Klotz, P. J . ; Schwartz, S. E.; Newman, L. Kinetics of the hydrogen peroxide-sulfur(IV) reaction in rainwater collected at a northeastern U.S. site. J. Geophys. Res. 1986, 91, 13264-13274. Schwartz, S. E. Mass-transport considerations pertinent to aqueous-phase reactions of gases in liquid-water clouds. In Chemistry of Multiphase Atmospheric Systems; Jaeschke, W., Ed.; Springer: Heidelberg, 1985; pp. 415-471. Chameides, W. L. The photochemistry of a remote marine stratiform cloud. J . Geophys. Res. 1984, 89, 4739-4755. Schwartz, S. E. and Freiberg, J. E. "Mass-transport limita­ tion to the rate of reaction of gases in liquid droplets: Application to oxidation of SO2 in aqueous solutions. Atmos. Environ. 1981, L5, 1129-1144. Tang, I. N.; Lee, J. H. Accommodation coefficients of ozone and sulfur dioxide: Their implications on SO2 oxidation in cloud water. American Chemical Society Symposium Series, 1987; this volume. Lee, Y.-N.; Schwartz, S. E. Evaluation of the rate of uptake of nitrogen dioxide by atmospheric and surface liquid water. J. Geophys. Res. 1981, 86, 11971-11983. Lee, Y.-N. Atmospheric aqueous-phase reactions of nitrogen species; Kinetics of some aqueous-phase reactions of peroxyacetyl nitrate. Conference on Gas-Liquid Chemistry of Natural Waters; Brookhaven National Laboratory, 1984; BNL 51757, Papers 20, 21. Lee, Y.-N.; Schwartz, S. E. Kinetics of oxidation of aqueous sulfur(lV) by nitrogen dioxide. In Precipitation Scavenging, Dry Deposition, and Resuspension; Pruppacher, H. R., Semonin, R. G., Slinn, W. G. Ν., Eds.; Elsevier: New York, 1983; pp. 453-470. Heikes, B. G.; Thompson, A. M. Effects of heterogeneous pro­ cesses on NO3, HONO, and HNO3 chemistry in the troposphere. J. Geophys. Res. 1983, 88, 10883-10895.

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

THE CHEMISTRY OF ACID RAIN

108

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25.

Chameides, W. L. The possible role of NO3 in the nighttime chemistry of a cloud. J . Geophys. Res. 1985, 91, 5331-5337. 26. Daum, P. H.; Schwartz, S. E.; Newman, L. Acidic and related constituents in liquid water stratiform clouds. J. Geophys. Res. 1984, 89, 1447-1458. 27. Daum, P. H.; Kelly, T. J.; Schwartz, S. E.; Newman, L. Measurements of the chemical composition of stratiform clouds. Atmos. Environ. 1984, 18, 2671-2684. 28. Schwartz, S. E. Chemical conversions in clouds. Aerosols: Research, Risk Assessment and Control Strategies; Lee, S. D., Schneider, T., Grant, L. D., Verkerk, P. J., Eds.; Lewis: Chelsea, MI, 1986; pp. 349-375. 29. Overton, J. Η., Jr. Validation of the Hoffmann and Edwards' S(IV)-H202 Mechanism. Atmos. Environ. 1985, 19, 687-690. 30. Hoigné, J.; Bader, H.; Haag, W. R.; Staehelin, J . Rate con­ stants of reactions of ozone with organic and inorganic com­ pounds in water-III. Water Res. 1985, 19, pp. 993-1004. 31. Martin, L. R. Kinetic studies of sulfite oxidation in aqueous solution. In SO2, NO and NO2 Oxidation Mechanisms: Atmo­ spheric Considerations; Calvert, J. G., Ed.; Butterworth: Boston, 1984; pp. 63-100. RECEIVED May 15, 1987

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Chapter 9

Accommodation Coefficients of Ozone and SO : Implications on SO Oxidation in Cloud Water 2

2

I. N.

Tang J. H. Lee

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch009

Environmental Chemistry Division, Brookhaven National Laboratory, Upton, NY 11973

Interfacial mass t r a n s f e r of t r a c e gases i n t o aqueous pnase is i n v e s t i g a t e d in a UV a b s o r p t i o n - s t o p flow apparatus. F o r the first t i m e , the mass accommodation coefficients are d e t e r m i n d f o r O 3 (5.3x10 ) and f o r SO2 (>2x10 ). The results are i n c o r p o r a t e d i n t o a s i m p l e model c o n s i d e r i n g the coupled interfacial mass t r a n s f e r and aqueous c h e m i s t r y in c l o u d d r o p s . I t i s shown t h a t dissolution of O 3 into a drop is f a s t com­ pared w i t h its subsequent o x i d a t i o n of d i s s o l v e d SO2. In addition, the c o n v e r s i o n r a t e of S ( I V ) to S ( V I ) i n aqueous drops by ozone r e a c t i o n s i s not limited by interfacial resistance. -4

-2

I n t e r f a c i a l mass t r a n s f e r i s an i m p o r t a n t c o n s i d e r a t i o n i n many dynamic p r o c e s s e s i n v o l v i n g the t r a n s p o r t of a gaseous s p e c i e s a c r o s s a gas-liquid interface. I n p a r t i c u l a r the r a t e of t r a c e gas i n c o r p o ­ r a t i o n i n t o aqueous drops i n the atmosphere has r e c e n t l y r e c e i v e d much a t t e n t i o n because of i t s r e l e v a n c e to a c i d p r e c i p i t a t i o n ( 1 , 2 ) . I n the p r e s e n t paper, mass accommodation c o e f f i c i e n t measurements are r e p o r t e d f o r O 3 and S O 2 on water s u r f a c e s , u s i n g an UV a b s o r p t i o n stop flow t e c h n i q u e . The r e s u l t s are i n c o r p o r a t e d i n t o a s i m p l e model c o n s i d e r i n g the c o u p l e d i n t e r f a c i a l mass t r a n s f e r and aqueous c h e m i s t r y i n aqueous d r o p s . Some i m p l i c a t i o n s of the measured accom­ modation c o e f f i c i e n t s on the o x i d a t i o n of S O 2 by O 3 i n c l o u d water are d i s c u s s e d . Experimental A d e t a i l e d d e s c r i p t i o n of the apparatus shown i n F i g u r e 1 and the e x p e r i m e n t a l procedure w i l l be g i v e n e l s e w h e r e . H e r e , i t s u f f i c e s to summarize as f o l l o w s . The experiments were c a r r i e d out i n a thermos t a t e d r e a c t i o n c e l l c o n s t r u c t e d of a r e c t a n g u l a r P y r e x tube, 4 cm χ 8 cm i n c r o s s s e c t i o n and 38 cm i n l e n g t h , and p l a c e d w i t h i t s

0097-6156/87/0349-0109$06.00/0 © 1987 American Chemical Society

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

THE CHEMISTRY OF ACID RAIN

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch009

110

l e n g t h i n a h o r i z o n t a l p o s i t i o n . The c e l l was equipped w i t h an o p t i ­ c a l window on e i t h e r end, gas i n l e t and o u t l e t on the top, and l i q u i d i n l e t and o u t l e t on the bottom. L i q u i d water was c i r c u l a t e d through the lower p o r t i o n o f the c e l l by an a l l - T e f l o n diaphragm pump, whereas t r a c e q u a n t i t i e s o f O 3 o r S O 2 i n a h u m i d i f i e d c a r r i e r gas was f l o w i n g c o n c u r r e n t l y i n the upper space. The system was designed t o operate a t low p r e s s u r e , t h e r e f o r e , very p r e c i s e flow and p r e s s u r e c o n t r o l s were e s s e n t i a l to m a i n t a i n the r e q u i r e d s t a b i l i t y d u r i n g an experiment. An UV l i g h t beam, o b t a i n e d w i t h an i n t e n s i t y - r e g u l a t e d d e u t e r i u m lamp and a n a r r o w - s l i t monochromator, passed through the gas phase between two p e r f e c t l y a l i g n e d p i n h o l e s mounted i n f r o n t o f the o p t i ­ c a l windows. An EMR 541-N PM tube, w i t h an a p p r o p r i a t e i n t e r f e r e n c e f i l t e r p l a c e d immediately b e f o r e i t , was used i n c o n j u n c t i o n w i t h a s s o c i a t e d e l e c t r o n i c s to c o n t i n u o u s l y m o n i t o r the UV i n t e n s i t y as a means of measuring changes i n c o n c e n t r a t i o n of the reagent g a s . I n a t y p i c a l e x p e r i m e n t , the system was pumped down to a s p e c i ­ f i e d t o t a l p r e s s u r e , and a t the same time the f l o w r a t e s o f the aqueous phase and the h u m i d i f i e d c a r r i e r gas were c a r e f u l l y a d j u s t e d to m a i n t a i n a s t a b l e f l o w . O 3 or S O 2 from a r e s e r v o i r was l e a k e d i n t o the c a r r i e r gas through a p r e c i s i o n needle v a l v e . As soon as a steady l i g h t i n t e n s i t y was o b t a i n e d , two s o l e n o i d v a l v e s on the gas i n l e t and o u t l e t of the r e a c t i o n c e l l were c l o s e d and a t h i r d s o l e ­ n o i d v a l v e on the by-pass l i n e opened. The gas phase i n the r e a c t i o n c e l l became stagnant and the l i g h t i n t e n s i t y i n c r e a s e d w i t h time as the reagent gas was being absorbed i n t o the aqueous phase. R e s u l t s and D i s c u s s i o n System A n a l y s i s . Because of the s i m p l i f i e d c e l l geometry and w e l l d e f i n e d o p e r a t i n g c o n d i t i o n s , a o n e - d i m e n s i o n a l m a t h e m a t i c a l model i s adequate f o r d e s c r i b i n g the mass t r a n s p o r t i n the gas phase. The d i f f e r e n t i a l e q u a t i o n i s g i v e n by Θ0

at

2

D

dC a 2

(1)

Y

where C i s the reagent gas c o n c e n t r a t i o n a t time t , y the v e r t i c a l c o o r d i n a t e e x p r e s s i n g the d i s t a n c e between the g l a s s w a l l (y = 0) and the g a s - l i q u i d i n t e r f a c e ( y = A ) . The i n i t i a l c o n d i t i o n i s r e p r e ­ sented by C = C , a t t = 0; 0 < y < A 0

and

(2)

the boundary c o n d i t i o n s a r e ac

0, a t y = 0; t > 0

ay and

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

(3)

9.

Accommodation Coefficients of Ozone and

TANG AND LEE

111

S0

2

Here, D i s the d i f f u s i v i t y of the reagent gas i n the gaseous medium, V the mean m o l e c u l a r speed of a Maxwell-Boltzraann gas, and α the mass accommodation c o e f f i c i e n t . The standard s o l u t i o n i s r e a d i l y o b t a i n e d (3) as f o l l o w s : C(t,y) C

m

~ n-1

0

2Lcos(S yM)

^

n

(2 + L + 3

2

)cos3

L

η

where β

are p o s i t i v e r o o t s of the

η

3tan3

=

^

(5)

(!^)t 1

\

I

/

η

equation

L

=

—

(6)

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch009

4D E q u a t i o n (5) i n d i c a t e s t h a t by m o n i t o r i n g the gas c o n c e n t r a t i o n change as a f u n c t i o n of time, the accommodation c o e f f i c i e n t may be deduced u s i n g a computer program. However, p r e c a u t i o n s must be undertaken to s a t i s f y the boundary c o n d i t i o n t h a t the s u r f a c e concen­ t r a t i o n of the d i s s o l v e d gas must be n e g l i g i b l e a t a l l times. This can be a c c o m p l i s h e d i n p r i n c i p l e by a g i t a t i o n and by a d d i t i o n of p r o p e r c h e m i c a l reagents i n the aqueous phase to remove the d i s s o l v e d gas as q u i c k l y as i t i s absorbed. In a d d i t i o n , the system must be operated a t s u f f i c i e n t l y low p r e s s u r e so t h a t the gas-phase r e s i s ­ tance i s much s m a l l e r than i n t e r f a c i a l r e s i s t a n c e . R e s u l t s . For O 3 , experiments were made w i t h both n i t r o g e n and h e l i u m as c a r r i e r gas i n the p r e s s u r e range of 29 to 85 t o r r , c o v e r i n g an e f f e c t i v e d i f f u s i v i t y range of 1.46 to 5.61 cm^/sec. Data were taken a t three d i f f e r e n t temperatures, namely, 0, 10 and 19°C The e f f e c t s of added c h e m i c a l reagent on the apparent accommodation c o e f f i c i e n t , a , were s t u d i e d u s i n g pure w a t e r , NaOH and Na2S03 s o l u t i o n s . As shown i n F i g u r e 2, the decay of O 3 w i t h time under a g i v e n c o n d i t i o n behaves as expected from the mathematical s o l u t i o n and i s q u i t e reproducible. I n pure w a t e r , as shown i n F i g u r e 3, a has a s m a l l v a l u e of 1.7x10*7 r e s u l t of the water s u r f a c e being q u i c k l y s a t u r a t e d by O3. I t i n c r e a s e s o n l y s l i g h t l y to a v a l u e of 6 x l 0 ~ ? by the a d d i t i o n of 0.05N NaOH, i n d i c a t i n g the slow r e a c t i o n of OH" w i t h d i s s o l v e d O3. However, a i n c r e a s e s d r a m a t i c a l l y to a v a l u e of 4.5x10"^ upon adding o n l y 8xlO"^M Na2S03» I t c o n t i n u e s to i n c r e a s e w i t h i n c r e a s ­ i n g Na2S03 c o n c e n t r a t i o n s u n t i l i t l e v e l s o f f a t a v a l u e of (5.3*±Ό.4)χ10"4, where the e r r o r s r e p r e s e n t one standard d e v i a t i o n e v a l u a t e d from a t o t a l of 79 measurements i n the p l a t e a u r e g i o n as shown i n F i g u r e 3. The f a c t t h a t a no l o n g e r changes w i t h s u l f i t e c o n c e n t r a t i o n i n d i c a t e s t h a t an u l t i m a t e or t r u e v a l u e of accommoda­ t i o n c o e f f i c i e n t f o r O 3 on water s u r f a c e s has now been reached. S i m i l a r experiments were c a r r i e d out w i t h S O 2 i n helium c a r r i e r gas. P r e l i m i n a r y r e s u l t s i n d i c a t e d t h a t a i n c r e a s e d from ~ 5 x l 0 ' i n pure water to ~ 2 x l 0 - ^ i n 0.05N NaOH s o l u t i o n . These v a l u e s of a are about two o r d e r s of magnitude l a r g e r than those of O 3 under i d e n t i c a l e x p e r i m e n t a l c o n d i t i o n s . When 0.2% H 2 O 2 s o l u t i o n ( a t pH = 13) was used, a i n c r e a s e d to about l x l 0 ~ 3 . F u r t h e r experiments w i t h s o l u ­ t i o n s of h i g h e r H 2 O 2 c o n c e n t r a t i o n s showed t h a t the mass accommoda­ t i o n c o e f f i c i e n t of S02 would be g r e a t e r than 2 x l 0 " . No h i g h e r a

a

a s

a

a

a

5

a

a

a

3

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch009

THE CHEMISTRY OF ACID RAIN

F i g u r e 2.

O3 decay i n h e l i u m c a r r i e r gas.

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

9.

Accommodation Coefficients of Ozone and

TANG AND LEE

S0

2

113

v a l u e s c o u l d be o b t a i n e d f o r SO2 s i n c e H2O2 a t h i g h c o n c e n t r a t i o n s decomposed e x c e s s i v e l y on v e s s e l w a l l s , thereby i n t e r f e r i n g w i t h the measurement. However, i t was d i s c o v e r e d t h a t NaCIO was a v e r y e f f e c t i v e reagent f o r SO2 o x i d a t i o n i n aqueous s o l u t i o n s . U s i n g NaCIO, the v a l u e o f a f o r SO2 i n c r e a s e d to 2 x l 0 ~ and p o s s i b l y h i g h e r . The f i n a l v a l u e c o u l d n o t be measured w i t h good p r e c i s i o n s i n c e d i f f u s i o n a l p r o c e s s e s a l s o became i m p o r t a n t i n c o n t r o l l i n g mass t r a n s p o r t r a t e s a t such h i g h a v a l u e s . T h e r e f o r e , 2 x l 0 " r e p r e s e n t s the lower bounds of a f o r SO2. 2

a

2

a

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch009

a

Model S t u d i e s . The o x i d a t i o n o f d i s s o l v e d SO2 i n water has been the s u b j e c t o f numerous s t u d i e s i n the p a s t decade, and i t s atmospheric s i g n i f i c a n c e r e g a r d i n g a c i d p r e c i p i t a t i o n needs no f u r t h e r e l a b o r a t i o n h e r e . However, most of the e a r l i e r s t u d i e s (4-7) have been devoted to aqueous c h e m i s t r y o n l y . R e c e n t l y , Schwartz and F r e i b e r g (8) have c o n s i d e r e d the importance of mass t r a n s f e r p r o c e s s e s i n l i m i t i n g the S(IV) o x i d a t i o n r a t e s i n aqueous drops. Chameides (9) has made a r a t h e r comprehensive model study o f the p h o t o c h e m i s t r y of a s t r a t i f o r m c l o u d i n a remote r e g i o n of the marine atmosphere. He concludes t h a t the r a t e o f SO2 c o n v e r s i o n to s u l f u r i c a c i d i s s e n s i t i v e to a v a r i e t y o f parameters i n c l u d i n g the accommodation c o e f f i c i e n t s o f the reagent gases such as S02, H2Û2, HO2 and OH. U n f o r t u n a t e l y , however, no accommodation c o e f f i c i e n t measurements have been r e p o r t e d i n the l i t e r a t u r e f o r these gases. I t would, t h e r e f o r e , be i n t e r e s t i n g to examine how i m p o r t a n t the newly measured accommodation c o e f f i c i e n t s would be i n the c o n v e r s i o n of S(IV) to S(VI) i n a water d r o p l e t . A simple model i s s e t up, which c o n s i d e r s o n l y aqueous c h e m i s t r y and gas-phase mass t r a n s f e r o f O3 and SO2 to a c l o u d d r o p l e t . A t t = 0, the d r o p l e t i s exposed to an atmosphere c o n t a i n i n g c o n s t a n t c o n c e n t r a t i o n s o f SO2 and O3. The aqueous c o n c e n t r a t i o n s of S(IV) and S(VI) a r e then c a l c u l a t e d as a f u n c t i o n o f time. The c h e m i c a l r e a c t i o n s c o n s i d e r e d i n the model a r e l i s t e d i n Table I , t o g e t h e r w i t h the a p p r o p r i a t e c o n s t a n t s used i n the c a l c u l a t i o n . The r a t e e x p r e s s i o n f o r gas-phase mass t r a n s f e r i s g i v e n by dC

3ϋγ

dt

a RT

, .

2

s

a

where a i s the d r o p l e t r a d i u s , R the gas c o n s t a n t , Τ the a b s o l u t e temperature, p the p a r t i a l p r e s s u r e of the reagent gas i n the b u l k gas phase and p a t the d r o p l e t s u r f a c e . Here, p i s r e l a t e d to the Henry's law c o n s t a n t , H, by s

a

a

Ρ

a

=

C — Η

(8)

and γ, a k i n e t i c c o r r e c t i o n f a c t o r to the Maxwell's e q u a t i o n (γ = 1 ) , can be e v a l u a t e d by one o f the s e v e r a l e x p r e s s i o n s proposed i n the l i t e r a t u r e ( 1 0 ) . F o r p r a c t i c a l purposes, however, these e x p r e s s i o n s y i e l d v e r y s i m i l a r v a l u e s . Consequently, the f o l l o w i n g e x p r e s s i o n due to Fukuta and W a l t e r (11) was used i n the p r e s e n t study:

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

THE CHEMISTRY OF ACID RAIN

114

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch009

•3

®-H

6

io- k

-

(5 0.05 Ν NaOH

Ο IO" ' 0 7

1

H 0 2

1 2

1

1 1 1 1 4 6 [no S0 ] χ ΙΟ M

1

" 8

2

2

3

F i g u r e 3 . Apparent accommodation c o e f f i c i e n t of O 3 as a f u n c t i o n of Na2S03 c o n c e n t r a t i o n i n aqueous s o l u t i o n .

10°

IO

1

IO TIME/sec 2

IO

3

IO

4

F i g u r e 4. C o n v e r s i o n of S ( I V ) to S ( V I ) i n d r o p l e t by ozone oxidation.

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

^S02(aq)

+

S02(g)

S02(aq)

^

HSO4-

NBS: ES:

+

=

+

=

+

2

H+

+ o

+ 02

I.

7

w

K

6

K K

5

K

=

=

=

=

=

H 4

=

-

8

exp[1120(l/T

= l/298])M

l/298)]M

1x10-14 e x p [ - 6 7 1 6 ( l / T

-

0.018222T)]M

NBS

ES

NBS

NBS

NBS

(4)

(4)

NBS

References

B u t t e r w o r t h and C o . , L t d . ,

l/298)]M

e x p [ 2 . 3 0 2 6 ( - 4 7 5 . 1 4 / T + 5.0435 -

6xl0~

-

atm-1

sec-1

sec"l

l/298)]M

exp(-10,500/RT)M~l

exp[3120(l/T

1 7

1.7x10-2 e x p [ 2 0 9 0 ( l / T

1.23

l.OxlO

1.0x1014 e x p ( - 1 1 0 0 0 / R T ) M - l

1 / 2 9 8 ) ] M atm-1

=

-

S o l u b i l i t y Constants

1.15x10-2 e x p [ 2 3 6 0 ( l / T

Rate,

=

*3

*2

Hi

Equilibrium,

S O 2 O x i d a t i o n b y Ozone i n D r o p l e t

N a t i o n a l B u r e a u o f S t a n d a r d s T e c h n i c a l Note 2 7 0 - 1 , 1965. " E l e c t r o l y t e S o l u t i o n s b y R . A . R o b i n s o n and R . H . S t o k e s , " 1959.

H+

+ H

=

5F=^H+ + O H -

S 0 4

=F=^ S 0 3

HSO3-

H2O

S04

HSO4""

H2O ^ H S O 3 -

+ S03= —>

—>

03(aq)

HSO3-

+

^ 0 3 ( a q )

0 3 (aq)

03(g)

Reactions

Table

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch009

116

THE CHEMISTRY OF ACID RAIN

Y

(9)

-

a + (4D/Va) Note t h a t the terra c o n t a i n i n g α i n the denominator accounts f o r interfacial resistance. E q u a t i o n (7) was combined w i t h a p p r o p r i a t e chemical r e a c t i o n r a t e e x p r e s s i o n s to y i e l d a s e t of coupled d i f f e r e n t i a l e q u a t i o n s e x p r e s s i n g r a t e s of change i n the d i s s o l v e d O 3 and S(IV) c o n c e n t r a ­ t i o n s . The equations were then s o l v e d n u m e r i c a l l y w i t h the u s u a l c o n s t r a i n t s of e l e c t r o n e u t r a l i t y and the a p p r o p r i a t e i o n i c e q u i l i b r i a g i v e n i n Table I . F i g u r e 4 shows the r e s u l t s of a case c a l c u l a t i o n performed f o r the f o l l o w i n g c o n d i t i o n s : a « 10 um; Τ - 283 Κ; ρ(0β) = 300 ppb; p(S02> - 1 ppb; α(0 ) = 5χ10~ ; a ( S 0 ) - 2 x l 0 ~ , l x l O " * , l x l O " ; and i n i t i a l d r o p l e t pH = 7. I n F i g u r e 4 [ S ( I V ) ] * i s the s a t u r a t i o n molar c o n c e n t r a t i o n of S(IV) i n the absence of O 3 and, t h e r e f o r e , the curves r e p r e s e n t the time e v o l u t i o n of [ S ( I V ) ] and [ S ( V I ) ] n o r m a l i z e d to [S(IV)1* s o l e l y f o r the convenience of comparing and p l o t t i n g the calculated results. I t i s i n t e r e s t i n g to observe t h a t i n a l l cases [ S ( I V ) ] always r i s e s to a peak and then f a l l s o f f g r a d u a l l y . I n c o n t r a s t , [ S ( V I ) ] c o n t i n u e s to i n c r e a s e as the o x i d a t i o n r e a c t i o n goes on. It indi­ c a t e s a dynamic process i n which the s t a t i o n a r y - s t a t e concept does not seem to apply to the s u l f u r s p e c i e s . On the c o n t r a r y , the c a l c u ­ l a t i o n ( r e s u l t s not shown here) i n d i c a t e s t h a t the d r o p l e t q u i c k l y becomes s a t u r a t e d w i t h d i s s o l v e d O 3 and, s h o r t l y a f t e r , m a i n t a i n s a s t e a d y - s t a t e [ O 3 ] c l o s e to s a t u r a t i o n f o r a long time, even though the accommodation c o e f f i c i e n t of O 3 used i n the c a l c u l a t i o n i s as low as the measured v a l u e , 5 x l 0 " . I n a d d i t i o n , the e f f e c t of i n t e r f a c i a l S O 2 mass t r a n s f e r on o x i d a t i o n i s not c o n s i d e r e d a p p r e c i a b l e s i n c e the curves c a l c u l a t e d f o r ot(S02) = 1 are almost i d e n t i c a l to those c a l c u l a t e d f o r a(S02) = 2 x l 0 ~ . Only when

CH C00"/H* 2

2

(CH C00)

2

#

(5)

3

q

and/or

#

CH /C0 3

2

(6)

The f a t e of the r a d i c a l s produced v i a R e a c t i o n 6 i s c u r r e n t l y being investigated. I n i t i a l r e s u l t s i n d i c a t e the f o r m a t i o n of o r g a n i c p e r o x i d e s and suggest the i n t e r m e d i a t e f o r m a t i o n of p e r o x y - r a d i c a l s (Kormann, C. ; Bahnemann, D. W. ; Hoffmann, M. R. u n p u b l i s h e d r e s u l t s ) . W i t h the i n h i b i t i o n of charge r e c o m b i n a t i o n c o n d u c t i o n band e l e c t r o n s a r e now a v a i l a b l e t o reduce m o l e c u l a r oxygen y i e l d i n g H 0 (Reaction 2). The observed steady-state c o n c e n t r a t i o n o f hydrogen p e r o x i d e can be u n d e r s t o o d as a c o m p e t i t i o n between R e a c t i o n s 2 and 7. 2

2

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

10.

Photocatalytic Formation of Hydrogen Peroxide

BAHNKMANN ET AL.

125

H 0 ELECTRODE 2

2

1cm

CELL

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch010

LIGHT IR-FILTER M0N0CHR0- UV- Γ FILTER MATOR SOURCE (HoO) MAGNETIC (450 W) STIRRER

IBM PC/AT

A/DCONVERTER (MBC)

OXIDASE METER (YSI)

F i g u r e 1. E x p e r i m e n t a l c o n f i g u r a t i o n u s e d f o r i r r a d i a t i o n s and hydrogen p e r o x i d e d e t e c t i o n .

T I M E / MIN.

Figure 2. H 0 f o r m a t i o n upon i l l u m i n a t i o n o f a n aqueous c o l l o i d a l s u s p e n s i o n o f z i n c o x i d e i n t h e p r e s e n c e o f 2 mM a c e t a t e ( o t h e r exp. cond. a r e g i v e n i n t h e f i g u r e ) . 2

2

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

THE CHEMISTRY OF ACID RAIN

126

H 0 2

2e"(cb)

2

+

+

2H aq

-*

2H 0

(7)

2

4

The value [ H 0 ] ( s s ) = 1.2·10" M measured i n air-saturated s o l u t i o n s ( [ 0 ] ( s s ) = 2.4·10" M) s u g g e s t s t h a t R e a c t i o n 7 i s about t w i c e a s e f f i c i e n t a s t h e i n i t i a l d i o x y g e n r e d u c t i o n . H 0 i s a l s o produced i n t h e absence o f h o l e scavengers p r o v i d e d t h e r i g h t c a t a l y s t i s used. F i g u r e 3 shows t h e f o r m a t i o n of hydrogen p e r o x i d e upon bandgap i l l u m i n a t i o n o f a n oxygenated aqueous s u s p e n s i o n o f T i 0 c o a t e d w i t h C o ( I I ) T S P w h i c h a c t s a s a n e l e c t r o n r e l a y t o t r a n s f e r e " ( c b ) o n t o 0 (Hong, A. P.; Bahnemann, D. W. ; Hoffmann, M. R. J . Phvs. Chem. a c c e p t e d f o r p u b l i c a t i o n 12/12/86). I t i s c l e a r l y o b v i o u s from F i g u r e 3 t h a t t h e same s t e a d y - s t a t e c o n c e n t r a t i o n o f H 0 i s reached once t h e system i s p e r t u r b e d by t h e a d d i t i o n o f H 0 d u r i n g p r o l o n g e d i r r a d i a t i o n . As i n t h e case o f ZnO no f o r m a t i o n o r d e p l e t i o n o f hydrogen p e r o x i d e i s o b s e r v e d i n t h e absence o f l i g h t . An o c t a h e d r a l l y c o o r d i n a t e d s u r f a c e complex, e.g., T i - 0 ~ - C o ( I I I ) T S P - 0 ~ * , has been identified as the c a t a l y t i c a l l y active species i n the T i 0 - C o ( I I ) T S P system. W i t h d i o x y g e n b e i n g bound i n t h e form o f s u p e r o x i d e , 0 ~ · , t h i s complex p r o v e d t o be e x t r e m e l y s t a b l e b u t a c t s a s a n e f f e c t i v e a c c e p t o r f o r c o n d u c t i o n band e l e c t r o n s p r o d u c e d upon i r r a d i a t i o n o f t h e b u l k T i 0 : 2

2

4

2

2

2

2

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch010

2

2

2

2

2

2

2

2

2

T i - 0 " - C o ( I I I ) T S P - 0 " - + e " ( c b ) -» T i - 0 " - C o ( I I I ) T S P - H 0 2

+ H 0

2

The aquo complex formed e " ( c b ) t o form a reduced with 0

2

2

(8)

i n R e a c t i o n 8 r e a d i l y accepts another m e t a l c e n t e r w h i c h then q u i c k l y r e a c t s

2

Ti-0"-Co(II)TSP-H 0

+

2

0

-»

2

Ti-0~-Co(III)TSP-0 "*

(9)

2

y i e l d i n g a g a i n t h e s t a b l e 0 ~· complex. H 0 i s formed i n quantum y i e l d s c l o s e t o 5 0 % b y t h i s r e a c t i o n sequence. The observed n e t f o r m a t i o n o f H 0 i n d i c a t e s t h a t t h e v a l e n c e band h o l e s , h ( v b ) , a r e a b l e t o o x i d i z e water v i a R e a c t i o n 3. The low s t e a d y - s t a t e c o n c e n t r a t i o n s [ H 0 ] ( s s ) w h i c h a r e reached d u r i n g these experiments ( 5 - 25 μΜ depending on t h e n a t u r e o f t h e c a t a l y s t ) suggest t h a t o x i d a t i o n o f H 0 v i a 2

2

2

2

2

+

2

2

H 0 2

2

+

+

2h (vb)

-*

0

2

+

2

2

+

2H aq

(10)

e f f i c i e n t l y competes w i t h R e a c t i o n 3. When p r e s e n t a t h i g h c o n c e n t r a t i o n s , hydrogen p e r o x i d e c a n a l s o compete w i t h m o l e c u l a r oxygen ( R e a c t i o n 9) f o r t h e open c o o r d i n a t i o n s i t e on C o ( I I ) T S P : Ti-0"-Co(II)TSP-H 0 2

+ H 0 2

2

-» T i - 0 " - C o ( I I I ) T S P - 0 H

+ OH"

(11)

R e a c t i o n 11 i s a n a l o g o u s t o R e a c t i o n 8 i n t h a t i t l e a d s t o t h e o v e r a l l r e d u c t i o n o f H 0 b y two e " ( c b ) . The major d i f f e r e n c e 2

2

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

10.

Photocatalytic Formation of Hydrogen Peroxide

BAHNEMANN ET AL.

Yll

between t h e z i n c o x i d e and t h e T i 0 - C o ( I I ) T S P systems i s t h a t t h e s u r f a c e complex ( C o ( I I ) T S P ) a c t s a s a n e l e c t r o n r e l a y i n one c a s e while sacrificial e l e c t r o n donors such a s a c e t a t e are a p r e r e q u i s i t e f o r i n t e r r u p t i o n of the e"/h recombination i n the other case. F o l l o w i n g t h e s t u d i e s o f t h e s e r a t h e r w e l l - d e f i n e d model systems a e r a t e d aqueous s u s p e n s i o n s o f d e s e r t sand p a r t i c l e s were i r r a d i a t e d ( X ( e x ) = 350 nm) i n t h e p r e s e n c e o f sodium a c e t a t e . The v e r y r a p i d f o r m a t i o n o f a s t e a d y - s t a t e c o n c e n t r a t i o n o f 0.2 uM H 0 upon i l l u m i n a t i o n i s shown i n F i g u r e 4. T h i s , however, decays v e r y q u i c k l y when t h e l i g h t i s t u r n e d o f f . A similar d e p l e t i o n i s a p p a r e n t when H 0 i s added i n t h e d a r k . I f the l i g h t i s t u r n e d on d u r i n g t h i s decay p e r i o d a s t e a d y - s t a t e o f 0.2 uM i s a g a i n e s t a b l i s h e d . These c y c l e s c a n be r e p e a t e d many t i m e s w i t h o u t any a p p a r e n t l o s s i n a c t i v i t y . I t has a l r e a d y been demonstrated ( 1 5 ) t h a t d e s e r t sand c o n t a i n s m i n e r a l s such a s hematite, a-Fe 0 , and a n a t a s e , Ti0 , and c a n thus be photocatalytically active. We e n v i s i o n a mechanism s i m i l a r t o t h a t p r o p o s e d f o r t h e model systems above t o a c c o u n t f o r t h e observed formation of H 0 on d e s e r t sands. I n t h i s case the e"/h p a i r ( R e a c t i o n 1) i s i n t e r c e p t e d b y t h e donor a c e t a t e ( R e a c t i o n s 5 a n d 6 ) l e a v i n g e ~ ( c b ) b e h i n d t o reduce 0 v i a R e a c t i o n 2. The e f f i c i e n t d e s t r u c t i o n o f H 0 , on t h e o t h e r hand, might be caused b y m e t a l i o n c o n t a m i n a n t s (M ) a d s o r b e d on t h e sand p a r t i c l e s (81-85). Hydrogen p e r o x i d e c a n thus r e a c t w i t h M i n a F e n t o n type r e a c t i o n ( 8 6 ) , 2

+

2

2

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch010

2

2

2

3

2

2

2

+

2

2

2

x+

x +

M

x +

+

H 0 2

2

-»

i x + 1 ) +

M

+ OH"

f o l l o w e d by t h e f r e e r a d i c a l R e a c t i o n s H 0 2

+

2

13 t o 17

(12)

(87.88). (13)

->

Η 0

Η0 ·

τ-

ο ~·

+

Η aq

(14)

-»

Η 0

+

ο

(15)

-»

Η 0

+

Η 0 · + 0 "· + Η aq 2

0Η·

0Η· 2

2

2

+

+

2

2

2

2

Η0 · 2

+

2

2

Η0 ·

+

0Η·

0Η·

+

0Η·

2

+

2

Η 0 2

ο

2

2

(16) (17)

overal1 the in results This reaction sequence disproportionation of H 0 and thus explains i t s rapid disappearance i n the dark. F i n a l l y , a word o f c a u t i o n s h o u l d be added r e g a r d i n g o t h e r p o s s i b i l i t i e s t o p h o t o g e n e r a t e hydrogen p e r o x i d e i n s u c h a n i l l - d e f i n e d n a t u r a l system. I n s p i t e of the r i g o r o u s p r e - t r e a t m e n t i t i s p o s s i b l e t h a t t r a c e amounts o f o r g a n i c a d s o r b a t e s a r e s t i l l p r e s e n t on t h e d e s e r t sand samples employed i n t h i s study. On t h e o t h e r hand, i t i s w e l l documented t h a t n a t u r a l l y o c c u r r i n g humic type m a t e r i a l s c a n a l s o be photochemical l y a c t i v e (89). Thus we cannot exclude the p o s s i b i l i t y t h a t p a r t o f t h e o b s e r v e d r a t h e r low s t e a d y - s t a t e 2

2

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

128

THE CHEMISTRY OF ACID RAIN

hi> on

' -5 mM H 02 o ô b e d

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch010

2

0 0

30

60

75 165

180

210

240

255

Time (min)

F i g u r e 3. F o r m a t i o n and d e p l e t i o n o f H 0 upon i r r a d i a t i o n ( X ( e x ) = 366 nm) o f a n oxygenated aqueous s u s p e n s i o n o f 0.3 g T i 0 - C o ( I I ) T S P / l a t pH 12. 2

2

2

time/min F i g u r e 4. F o r m a t i o n and d e p l e t i o n o f H 0 upon i l l u m i n a t i o n a n d i n t h e d a r k o b s e r v e d i n a n a e r a t e d aqueous s u s p e n s i o n o f Death V a l l e y d e s e r t sand ( o t h e r exp. cond. a r e g i v e n i n t h e f i g u r e ) . 2

2

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

10.

129

Photocatalytic Formation of Hydrogen Peroxide

BAHNEMANN ET AL.

c o n c e n t r a t i o n o f H 0 i s formed v i a t h e d i r e c t e x c i t a t i o n o f such molecules. Further experiments a r e c u r r e n t l y being performed to d i f f e r e n t i a t e between these pathways. 2

2

C o n c l u d i n g Remarks We have shown that hydrogen peroxide c a n be produced photocatalytically i n the presence of semiconductor p a r t i c l e s . Quantum y i e l d s up t o 5 0 % and s t e a d y - s t a t e c o n c e n t r a t i o n s between 0.2 and 120 μΜ H 0 have been observed. While the reduction of m o l e c u l a r oxygen by e ~ ( c b ) seems t o be t h e most l i k e l y p r o c e s s f o r H 0 - f o r m a t i o n , o x i d a t i o n o f water by h ( v b ) s h o u l d i n p r i n c i p l e y i e l d t h e same p r o d u c t s . I t i s t h e o b s e r v a t i o n o f hydrogen p e r o x i d e p r o d u c t i o n upon t h e i l l u m i n a t i o n o f a n a e r a t e d aqueous s u s p e n s i o n o f d e s e r t sand p a r t i c l e s t h a t p r e s e n t s t h e most i n t r i g u i n g r e s u l t o f t h i s s t u d y . Submicron sand p a r t i c l e s a r e v e r y abundant i n t h e atmosphere where they a c t a s c o n d e n s a t i o n n u c l e i ( 9 0 ) . T h e i r involvement a s catalysts and/or photocatalysts i n chemical transformations o c c u r r i n g i n n a t u r a l environments h a s so f a r been n e g l e c t e d even though they a r e r a t h e r p e r s i s t e n t i n t h e atmosphere with h a l f - l i v e s o f s e v e r a l days b e f o r e p r e c i p i t a t i o n t a k e s p l a c e . We p r o p o s e t h e s u r f a c e r e a c t i o n o f p h o t o c a t a l y t i c a l l y formed H 0 with sulfur d i o x i d e ( S 0 ) and n i t r o u s o x i d e s (N0 ) as an a d d i t i o n a l pathway f o r t h e f o r m a t i o n o f a c i d r a i n . Even though due to i t s metal-catalyzed dismutation the steady-state c o n c e n t r a t i o n o f H 0 observed i n t h e d e s e r t sand e x p e r i m e n t was r a t h e r low, i t may n e v e r t h e l e s s be h i g h enough t o y i e l d r e a s o n a b l e q u a n t i t i e s o f o x i d a t i o n p r o d u c t s l i k e H S 0 o r HN0 . Further experiments a r e i n progress t o study the p h o t o c a t a l y t i c a c t i v i t y of n a t u r a l systems. 2

2

+

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch010

2

2

2

2

2

2

X

2

2

4

3

Acknowledgment We g r a t e f u l l y acknowledge t h e f i n a n c i a l s u p p o r t o f t h e U.S. EPA (CR812356-01-0 a n d R811612-01-0) a n d i n p a r t i c u l a r we want t o thank D r s . D o n a l d C a r e y and M a r c i a Dodge f o r t h e i r s u p p o r t .

Literature Cited 1. Hoffmann, M. R.; Kerr, J. Α.; Calvert, J. G. Chemical Transformation Modules for Eulerian Acid Deposition Models. Vol.11: The Aqueous-Phase Chemistry; NCAR, Boulder, 00, 1984. 2. Hoffmann, M. R.; Boyce, S. D. Advances in Environmental Science and Technology; Schwartz, S. Ε., Ed.; Wiley, New York, 1983, 12, 147. 3. Hoffmann, M. R.; Jacob, D. J. SO NO, and NO Oxidation Mechanisms: Atmospheric Considerations; Calvert, J. G., Ed.; Acid Precipitation Series - Vol. 3; Teasley, J. I., Series Ed.; Butterworth, Boston, MA, 1984, 101. 4. Jacob, D. J.; Hoffmann, M. R. J. Geophys Res. 1983, 88, 6611. 2,

2

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5. Kok, G. L . ; Darnall, K. R.; Winer, Α. Μ., Pitts, J. Ν., Jr.; Gay, B. W. Environ. Sci. Tech. 1978, 12, 1077. 6. Kok, G. L. Atmos. Environ. 1980, 14, 653. 7. Richards, L. W.; Anderson, J. Α.; Blumenthal, D. L . ; McDonald, J. Α.; Kok, G. L. Atmos. Environ. 1983, 17, 911. 8. Schwartz, S. E. Annals of the New York Academy of Sciences, Section of Environmental Sciences 1985, xx, xxx. 9. Seinfeld, J. H. Atmospheric Chemistry and Physics of Air Pollution; John Wiley & Sons, New York, NY, 1986, 236. 10. Chameides, W. L . ; Davis, D. D. J. Geophvs Res. 1982, 87, 4863. 11. Zika, R. G.; Saltzman, E.; Chameides, W. L . ; Davis, D. D. J. Geophvs. Res. 1982, 87, 5015. 12. Graedel, T. E.; Goldberg, Κ. I. J. Geophys. Res. 1983, 88, 865. 13. Chameides, W. L. J. Geophys. Res. 1984, 88, 4739. 14. Fendler, J. H. J. Phys. Chem. 1985, 89, 2730. 15. Schrauzer, G. N.; Strampach, N.; Hui, L. N.; Palmer, M. R.; Saleshi, J. Proc. Natl. Acad. Sci. USA 1983, 80, 3873. 16. Seinfeld, J. H. Atmospheric Chemistry and Physics of Air Pollution; John Wiley & Sons, New York, NY, 1986, 26. 17. Stumm, W.; Morgan, J. J. Aquatic Chemistry; John Wiley & Sons, New York, NY, 1981, 238. 18. Bard, A. J. Science 1980, 207, 139. 19. Rothenburger, G.; Moser, J.; Gratzel, M.; Serpone, N.; Sharma, D. K. J. Am. Chem. Soc. 1985, 107, 8054. 20. Izumi. I.; Dunn, W. W.; Wilbourn, K. O.; Fan, F. F.; Bard, A. J. J. Phys. Chem. 1980, 84, 3027. 21. Harvey, P. R.; Rudham, R.; Ward, S. J. Chem. Soc. Faraday Trans. 1 1983, 79, 2975. 22. Herrmann, M.-M.; Mozzanega, M.-N.; Pichat, P. J. Photochem. 1983, 22, 333. 23. Fox, Μ. Α.; Chen, C.-C.; Park, H.-H.; Younathan, J. N. ACS Symp. Ser. 1985, 278, 69. 24. Brown, G. T.; Darwent, J. R. J. Chem. Soc. Faraday Trans. 1 1984, 80, 1631. 25. Bahnemann, D.; Henglein, Α.; Spanhel, L. Faraday Discuss. Chem. Soc. 1984, 78, 151. 26. Gerischer, H. Topics in Applied Physics 1979, 31, 115. 27. Latimer, W. M. Oxidation Potentials. 2nd Edition; Prentice-Hall, New York, NY, 1952, 38-50. 28. Baur, E.; Neuweiler, C. Helv. Chim. Acta 1927, 10, 901. 29. Böhi, J. Helv. Chim. Acta 1929, 12, 121. 30. Chari, C. N.; Qureshi, M. J. Indian Chem. Soc. 1944, 21, 97. 31. Chari, C. N.; Qureshi, M. J. Indian Chem. Soc. 1944, 21, 297. 32. Markham, M. C.; Laidler, K. J. J. Phys. Chem. 1953, 57, 363. 33. Rubin, T. R.; Calvert, J. G.; Rankin, G. T.; MacNevin, W. M. J. Am. Chem. Soc. 1953, 75, 2850. 34. Calvert, J. G.; Theurer, K.; MacNevin, W. M. J. Am. Chem. Soc. 1954, 76, 2575. 35. Stephens, R. E.; Ke, B.; Trivich. D. J. Phys. Chem. 1955, 59, 966.

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36. 37. 38. 39. 40. 41. 42. 43.

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch010

44. 45. 46. 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65.

66.

Photocatalytic Formation of Hydrogen Peroxide

131

Kuriacose, J. C.; Markham, M. C. J. Catalysis 1962, 1, 498. Morrison, S. R.; Freund, T. J. Chem. Phys. 1967, 47, 1543. Harbour. J. R.; Hair. M. L. J. Phys. Chem. 1977, 81, 1791. Harbour. J. R.; Hair. M. L. J. Phys. Chem. 1979, 83, 652. Hair. M. L.; Harbour. J. R. Adv. Chem. Ser. 1980, 184, 173. Pappas. S. P.; Fischer. R. M. J. Paint Technology 1974, 46, 65. Cundall. R. B.; Rudham. R.; Salim. M. S., T. Chem. Soc. Faraday Trans. 1 1976, 72, 1642. Harbour, J. R.; Hair, M. L. "Magnetic Resonance in Colloid and Interface Science". Fraissard, J. P.; Resing, Η. Α., Eds.; Riedel Publ. Co. 1980, 431. Harbour, J. R.; Tromp, J . ; Hair. M. L. Can. J. Chem. 1985. 63. 204. Rao. M. V.; Rajeshwar. K.; Pal Verneker. V. R.; DuBow. J. J. Phys. Chem. 1980, 84, 1987. Salvador. P.; Decker. F. J. Phys. Chem. 1984, 88, 6116. Rives-Arnau, V. J. Electroanal. Chem. 1985, 190, 279. Jaeger. C. D.; Bard. A. J. J. Phys. Chem. 1979, 83, 3146. Anpo. M.; Shima. T.; Kubokawa. Y. Chem. Lett. 1985, 1799. Serwicka, E. Colloids and Surfaces 1985, 13, 287. Baur, E.; Perret, A. Helv. Chim. Acta 1924, 7, 910. Perret, A. J. Chim. Phys. 1926, 23, 97. Hada, H.; Yonezawa, Y.; Saikawa, M. Bull. Chem. Soc. Jpn. 1982, 55, 2010. Nishimoto, S.-I.; Ohtani, B.; Kajiwara, H.; Kagiya, T. JL Chem. Soc. Faraday Trans. 1 1983, 79, 2685. Kennedy, D. R.; Ritchie, M.; MacKenzie, J. Trans. Faraday Soc. 1958, 54, 119. McLintock, I. S.; Ritchie, M. Trans. Faraday Soc. 1965, 61, 1007. Stone, F. S. Anal. Real. Soc. Espan. Fis. Quim. 1965. 61, 109. Boonstra, A. H.; Mutsaers, C. Α. Η. A. J. Phys. Chem. 1975, 79, 1694. Boonstra, A. H.; Mutsaers, C. A. H. A. J. Phys. Chem. 1975, 79, 1940. Boonstra, A. H.; Mutsaers, C. Α. Η. A. J. Phys. Chem. 1975, 79, 2025. Munuera, G.; Rives-Arnau, V.; Saucedo, A. J. Chem. Soc. Faraday Trans. 1 1979, 75, 736. Gonzalez-Elipe. A. R.; Munuera. G.; Soria. J. J. Chem. Soc. Faraday Trans. 1 1979, 75, 748. Munuera. G.; González-Elipe, A. R.; Soria, J . ; Sanz, J. J. Chem. Soc. Faraday Trans. 1 1980, 76, 1535. Munuera, G.; Navio, A. Stud. Surf. Sci. Catal. Pt. B. New Horiz. Catal. 1981, 7, 1185. Munuera. G.; González-Elipe. A. R.; Rives-Arnau. V.; Navio, Α.; Malet. P.; Soria. J.; Conesa. J. C.; Sanz. J. "Adsorption and Catalysis on Oxide Surfaces", Che M.; Bond. G. C., Eds.; Elsevier Sci. Publ. 1985, 113. Tanaka. K.; White. J. M. J. Phys. Chem. 1982, 86, 4708.

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

THE CHEMISTRY OF ACID RAIN

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132

67. Tatsumi, K.; Shiotani, M.; Freed, J. H. J. Phys. Chem. 1983, 87, 3425. 68. Yesodharan, E.; Grätzel, M. Helv. Chim. Acta 1983, 66, 2145. 69. Duonghong, D.; Grätzel, M. J. Chem. Soc. Chem. Comm. 1984, 1597. 70. Oosawa, Y.; Grätzel, M. J. Chem. Soc. Chem. Comm. 1984, 1629. 71. Che, M.; Gianello, E.; Tench, A. J. Colloids and Surfaces 1985, 13, 231. 72. Mühlebach, J . ; Müller, K.; Schwarzenbach, G. Inorg. Chem. 1970, 9, 2381. 73. Schwarzenbach, D. Inorg. Chem. 1970, 9, 2391. 74. Bahnemann, D.; Henglein, Α.; L i l i e , J . ; Spanhel, L. J. Phys. Chem. 1984, 81, 709. 75. Patrick, W. Α.; Wagner, Η. B. Anal. Chem. 1949, 21, 1279. 76. Savage, D. J. Analyst (London) 1951, 76, 224. 77. Mönig, J. Diploma thesis, Technical University of Berlin, Germany, 1980, pp. 38-40. 78. Guilbault, G. G.; Brignac, P. J . ; Juneau, M. Anal. Chem. 1968, 40, 1256. 79. Lazrus, A. L . ; Kok, G. L . ; Gitlin, S. N.; Lind, J. Α.; McLaren, S. E. Anal. Chem. 1985, 57, 917. 80. Heller, H. G.; Langan, J. R. J. Chem. Soc. Perkin Trans. 2. 1981, 341. 81. James, R. O.; Healy, T. W. J. Coll. Interface Sci. 1972, 40, 42. 82. James, R. O.; Healy, T. W. J. Coll. Interface Sci. 1972, 40, 53. 83. Huang, C.-P.; Stumm, W. J. Coll. Interface Sci. 1973, 43, 409. 84. Davis, J. Α.; Leckie, J. O. J. Coll. Interface Sci. 1978, 67, 90. 85. Elliott, Η. Α.; Huang, C. P. J. Coll. Interface Sci. 1979, 70, 29. 86. Fenton, H. J. H. J. Chem. Soc. 1894, 65, 899. 87. Haber, F.; Weiss, J. Proc. R. Soc. London Ser. A 1934, 147, 332. 88. Weinstein, J . ; Bielski, Β. H. J. J. Am. Chem. Soc. 1979, 101, 38. 89. Zafiriou, O. C.; Joussot-Dubien, J . ; Zepp, R. G.; Zika, R. G. Environ. Sci. Technol. 1984, 18, 359A. 90. Pruppacher, H. R.; Klett, J. D. Microphvsics of Clouds and Precipitation; D. Riedel Publ. Co., Dordrecht, Holland, 1978. RECEIVED March 16, 1987

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Chapter 11

Direct Kinetic and Mechanistic Study of the OH-Dimethyl Sulfide Reaction Under Atmospheric Conditions A. J. Hynes and P. H. Wine

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch011

Molecular Sciences Branch, Georgia Tech Research Institute, Georgia Institute of Technology, Atlanta, GA 30332 A pulsed l a s e r p h o t o l y s i s - p u l s e d l a s e r induced f l u o r e s cence t e c h n i q u e was employed to study the OH + CH3SCH3 r e a c t i o n in N2, air, and O2 b u f f e r g a s e s . Complex kinetics were o b s e r v e d in the p r e s e n c e o f O2. A four s t e p mechanism i n v o l v i n g hydrogen a b s t r a c t i o n , reversible a d d i t i o n to the sulfur atom, and s c a v e n g i n g o f the ( t h e r m a l i z e d ) adduct by O2 is r e q u i r e d to e x p l a i n all experimental observations. I n one atmosphere o f air, the effective b i m o l e c u l a r r a t e constant decreases m o n o t o n i c a l l y from 1.58 x 10 to 5.2 x 10 cm3 molecule-1 -1 o v e r the l o w e r t r o p o s p h e r i c t e m p e r a t u r e range 250-310K. Over the same t e m p e r a t u r e range the b r a n c h i n g ratio for h y d r o g e n a b s t r a c t i o n i n c r e a s e s m o n o t o n i c a l l y from 0.24 to 0 . 8 7 . -11

-12

S

On a g l o b a l s c a l e , n a t u r a l e m i s s i o n s o f reduced s u l f u r compounds account f o r about 50% o f the t o t a l s u l f u r f l u x i n t o the atmosphere (1-3). Hence, i t i s i m p o r t a n t to u n d e r s t a n d the n a t u r a l s u l f u r c y c l e i n o r d e r t o e s t a b l i s h a "base l i n e " f o r a s s e s s i n g the s i g n i f i c a n c e o f a n t h r o p o g e n i c p e r t u r b a t i o n s ( p r i m a r i l y SO2 e m i s s i o n s ) . DimethyIsulf i d e (DMS) i s the predominant r e d u c e d s u l f u r compound e n t e r i n g t h e atmosphere from t h e oceans ( 4 - 9 ) , and DMS o x i d a t i o n r e p r e s e n t s a major g l o b a l s o u r c e o f S ( V I ) . The a t m o s p h e r i c o x i d a t i o n o f DMS can be i n i t i a t e d by r e a c t i o n w i t h e i t h e r OH o r NO3. I n marine e n v i r o n m e n t s , however, NO3 l e v e l s a r e t y p i c a l l y v e r y low and DMS i s d e s t r o y e d p r i m a r i l y by OH:

OH +

->

CH3SCH2 + H 0

(la)

->

CH S(OH)CH

(lb)

2

CH3SCH3

3

3

0097-6156/87/0349-0133$06.00/0 © 1987 American Chemical Society

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

THE CHEMISTRY OF ACID RAIN

134

A number o f k i n e t i c s s t u d i e s of R e a c t i o n 1 have been r e p o r t e d (10-17). I n a d d i t i o n , s e v e r a l s t e a d y s t a t e photοlys i s - e n d p r o d u c t a n a l y s i s s t u d i e s have r e c e n t l y been r e p o r t e d where c o n c l u s i o n s were drawn c o n c e r n i n g the r e l a t i v e importance o f h y d r o g e n a b s t r a c t i o n and a d d i t i o n t o the s u l f u r atom as r e a c t i o n pathways (18-20). Despite the r a t h e r l a r g e d a t a base, n e i t h e r t h e r a t e c o n s t a n t nor t h e b r a n c h ­ i n g r a t i o f o r R e a c t i o n 1 i s w e l l d e f i n e d . V a l u e s f o r k i have been measured d i r e c t l y u s i n g b o t h f l a s h p h o t o l y s i s (10,11,13,17) and d i s ­ charge f l o w (14,16) t e c h n i q u e s , w i t h r e p o r t e d 298K r a t e c o n s t a n t s r a n g i n g from 3.2 t o 9.8 χ 10~12cm3molecule~l-s~l- and r e p o r t e d a c t i v a ­ t i o n e n e r g i e s r a n g i n g from -352 to +274 c a l m o l e " . A l l direct measurements were c a r r i e d out i n the absence o f t h e p o t e n t i a l l y r e a c t i v e gas 02· Two c o m p e t i t i v e k i n e t i c s s t u d i e s (12,15), b o t h of w h i c h employed one atmosphere o f a i r as t h e b u f f e r gas, r e p o r t 298K r a t e c o n s t a n t s i n agreement w i t h t h e h i g h e r v a l u e s r e p o r t e d i n t h e direct studies. W h i l e t h e r e seems t o be g e n e r a l agreement t h a t the b r a n c h i n g r a t i o f o r Channel l a i s s i g n i f i c a n t , the c o n t r i b u t i o n from Channel l b remains p o o r l y d e f i n e d .

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch011

1

We have employed a p u l s e d l a s e r p h o t o l y s i s - p u l s e d l a s e r i n d u c e d f l u o r e s c e n c e t e c h n i q u e t o c a r r y o u t d i r e c t , r e a l time s t u d i e s o f OH r e a c t i o n s w i t h DMS and DMS-dfc i n N 2 , a i r , and O 2 b u f f e r gases. Both temperature and p r e s s u r e dependencies have been i n v e s t i ­ gated. We f i n d t h a t the o b s e r v e d r a t e c o n s t a n t ( k b = d[0H]/[0H] [DMS]dt) depends on t h e O 2 c o n c e n t r a t i o n . Our r e s u l t s a r e c o n s i s t e n t w i t h a mechanism w h i c h i n c l u d e s an a b s t r a c t i o n r o u t e , a r e v e r s i b l e a d d i t i o n r o u t e , and an adduct + O 2 r e a c t i o n w h i c h competes w i t h adduct d e c o m p o s i t i o n under a t m o s p h e r i c c o n d i t i o n s . Q

s

Experimental A s c h e m a t i c o f t h e apparatus i s shown i n F i g u r e 1. OH was produced by 248 nm ( o r 266 nm i n some e x p e r i m e n t s ) p u l s e d l a s e r p h o t o l y s i s o f H 2 O 2 and d e t e c t e d by o b s e r v i n g f l u o r e s c e n c e e x c i t e d by a p u l s e d t u n ­ a b l e dye l a s e r . F l u o r e s c e n c e was e x c i t e d i n t h e 0 Η ( Α 2 Σ - X^ir) 0-1 band a t 282 nm and d e t e c t e d i n the 0-0 and 1-1 bands a t 309+5 nm. K i n e t i c d a t a was o b t a i n e d by e l e c t r o n i c a l l y v a r y i n g t h e time d e l a y between t h e p h o t o l y s i s l a s e r and the p r o b e l a s e r . S u l f i d e concentra­ t i o n s were measured i n s i t u i n t h e slow f l o w system by UV photometry a t 228.8 nm. +

Results A l l experiments were c a r r i e d o u t under p s e u d o - f i r s t o r d e r c o n d i t i o n s w i t h DMS i n l a r g e excess o v e r OH. E x p o n e n t i a l OH decays were ob­ s e r v e d under a l l e x p e r i m e n t a l c o n d i t i o n s i n v e s t i g a t e d . P l o t s o f k ( t h e p s e u d o - f i r s t o r d e r OH decay r a t e ) v e r s u s DMS c o n c e n t r a t i o n were linear. V a l u e s f o r k b were o b t a i n e d from l i n e a r l e a s t squares d e t e r m i n a t i o n s of t h e s l o p e s o f k v e r s u s [DMS] p l o t s . Measured values f o r k ^ as a f u n c t i o n o f temperature, p r e s s u r e , and O 2 con­ c e n t r a t i o n a r e summarized i n T a b l e I . Important o b s e r v a t i o n s c o n c e r n i n g t h e d a t a r e p o r t e d i n T a b l e I a r e summarized below 1. I n the absence o f 0 , DMS r e a c t s s i g n i f i c a n t l y more r a p i d l y w i t h OH t h a n does DMS-dfc. T h i s s u g g e s t s t h a t under t h e s e experimen­ t a l c o n d i t i o n s (no O 2 ) h y d r o g e n a b s t r a c t i o n i s t h e dominant r e a c t i o n !

0

s

f

Q

s

2

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch011

11.

HYNES AND WINE

The OH and Dimethyl Sulfide Reaction

135

F i g u r e 1. Schematic o f t h e a p p a r a t u s . A C - a b s o r p t i o n c e l l , BPFbandpass f i l t e r , CdL-cadmium lamp, C M - c a p a c i t a n c e manometer, IDf r e q u e n c y d o u b l e r , DG-three c h a n n e l d e l a y g e n e r a t o r , DC-dye l a s e r , EM-emergy m o n i t o r , GI-gas i n l e t , HS-harmonic s e p a r a t o r , HV-high v o l t a g e , ΡA-picoammeter, PD-photodiode, PM-photomultip l i e r , PL-photolysis l a s e r , RC-reaction c e l l , SA-signal a v e r a g e r , T - c h r o t t l e , YL-Nd:YAG l a s e r , 7-54F-Corning 7-54 g l a s s filter.

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

136

THE CHEMISTRY OF ACID RAIN

Table I.

Observed B i m o l e c u l a r Rate C o n s t a n t s as a F u n c t i o n o f Temperature, P r e s s u r e , and 0 Concentration 9

Sulfide

T(K)

P(Torr)

M

Range o f .. k (s ) 1

( a )

k , +2a obs (10- cm molecule^ls" ) -

12

3

1

CH SCH

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch011

3

CD SCD 3

3

3

+

1.7

9.53

+

0.28

160-•13700

4.80

+

0.11

53-•7500

4.75

+

0.15

262

700

air

498- •24900

1?.5

279

700

air

372- •24200

298

40

298

500

N

2

SF

6

298

50

air

151-•8610

4.68

+

0.08

298

130

air

1960- •21800

5.04

+

0.14

298

340

air

310-•28900

5.18

0.34

298

590

air

596- •56100

5.80

+

298

750

air

1850- •65700

6.28

+

0.10

321

700

air

420-•22300

5.43

+

0.30

261

700

air

1080- •50500

11.6

+

1.1

854- •48500

13.5

+

1.2 2.0

266

700

275

700

276 287 287

700

298

450

298

100

°2

0.16

606-•54200

11.9

+

700

°2 air

1650- •47300

9.63

± 0.63

700

air

777-•20100

5.29

+

0.44

593-•23100

6.99

+

0.53

1520- •18900

1.82

+

0.11

193- •19800

2.10

+

0.15

°2 N

2 air

298

300

air

336-•17300

2.68

+

0.09

298

500

air

804-•11700

2.97

+

0.13

298

700

air

672-•18900

3.40

+

0.13

1290- •21200

6.50

+

0.72

817-•16500

3.02

+

0.18

298

700

317

700

321

700

340

700

340

700

361

700

(a) e r r o r s a r e 2σ and r e p r e s e n t

°2 air °2 air °2 air

0.27

620-•13600

3.72

1030- -11470

2.32

+

0.11

547--7880

2.30

+

0.28

1110- -15200

2.66

cision

only

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

0.11

11.

HYNES AND

137

The OH and Dimethyl Sulfide Reaction

WINE

pathway. We have c a r r i e d out c o n v e n t i o n a l FP-RF k i n e t i c s t u d i e s o f OH r e a c t i o n s w i t h a s e r i e s of s u l f i d e s i n argon b u f f e r gas ( 2 1 ) ; r e a c t i v i t y t r e n d s and a c t i v a t i o n e n e r g i e s o b s e r v e d i n t h e s e e x p e r i ­ ments s u p p o r t t h e dominance o f Channel l a when no O 2 i s p r e s e n t . 2. A t 298K, k b i n c r e a s e s as a f u n c t i o n of a i r p r e s s u r e f o r b o t h DMS and DMS-d6 r e a c t i o n s w i t h OH. The s l o p e s o f k b versus ^ a i r pl°ts a r e v i r t u a l l y e q u a l f o r t h e two s u l f i d e s . 3. I n b o t h a i r and O 2 a t 700 T o r r t o t a l p r e s s u r e , k ^ in­ c r e a s e s d r a m a t i c a l l y w i t h d e c r e a s i n g temperature. A l l experimental o b s e r v a t i o n s are c o n s i s t e n t w i t h the f o l l o w i n g mechanism ( w r i t t e n f o r C H 3 S C H 3 b u t i d e n t i c a l f o r C D 3 S C D 3 ) : 0

s

Q

s

0

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch011

OH

+

CH3SCH3

>

CH3SCH2

OH + C H 3 S C H 3 + M CH S(OH)CH

3

+ M

CH S(OH)CH

3

+ 0

3

3

>

H0

(la)

2

CH S(OH)CH 3

+ M

3

(lb)

OH + C H 3 S C H 3

> >

2

+

g

(-lb)

products

(2)

> l o s s by r e a c t i o n w i t h H 2 O 2 and d i f f u s i o n from the d e t e c t o r f i e l d of view

OH

(3)

As mentioned above, i n the absence of O 2 a l l o b s e r v e d OH removal ap­ p e a r s t o be v i a t h e a b s t r a c t i o n r o u t e , i . e . R e a c t i o n l a . A p p a r e n t l y , R e a c t i o n - l b i s v e r y f a s t compared to the time s c a l e o f our e x p e r i ­ ments. However, the adduct l i f e t i m e must be l o n g enough t h a t i t can be scavenged by O 2 i n c o m p e t i t i o n w i t h d e c o m p o s i t i o n b a c k to r e a c t ants. The d r a m a t i c dependence o f k ^ on temperature i s q u a l i t a ­ t i v e l y c o n s i s t e n t w i t h the above mechanism. The a c t i v a t i o n energy f o r R e a c t i o n - l b i s e x p e c t e d t o be q u i t e l a r g e , s o t h e f r a c t i o n o f adduct m o l e c u l e s scavenged by O 2 can i n c r e a s e d r a m a t i c a l l y o v e r a r e l a t i v e l y s m a l l temperature range. A t h i g h O 2 l e v e l s , t h e adduct can be assumed to be i n s t e a d y state. A p p l y i n g the s t e a d y s t a t e a p p r o x i m a t i o n t o t h e above mechan­ ism, one o b t a i n s : 0

,

_

obs

s

k, (T) + X C O i k , (T) + k ( T ) } [ 0 j la la lb l_ 1 T

1 + X(T)[0 ]

γ/ \

'

2

M

1

k (T) * 9

=

" k_ (T) lb

We assume t h a t o v e r the l i m i t e d temperature range 260 r a t e c o n s t a n t s can be e x p r e s s e d i n A r r h e n i u s form: = A

k (T) ±

1

exp

//>

τ

;

- 360K, a l l

(-E /RT).

(5)

±

We have t a k e n the 13 r a t e c o n s t a n t s f o r OH + DMS-d5 measured i n 700 T o r r a i r and 700 T o r r 0 ( T a b l e I) and f i t k g ( T , [ 0 D to E q u a t i o n 4 u s i n g a l e a s t squares f i t t i n g c r i t e r i o n . The s u p e r s c r i p t D i n d i ­ c a t e s the C D 3 S C D 3 a n a l o g o f e q u a t i o n s 1-4. V a l u e s f o r k ^ ( T ) were 2

b s

2

a

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

138

T H E CHEMISTRY OF ACID RAIN

taken from the FP-RF results (21). A j , Α^(Ξ A ^ / A ^ ) and Εχ(Ξ E^-E^ ) were taken as independent variables. By analogy with known activation energies f o r OH addition to C H 3 S H (22), C H 3 S D (22), and C H 3 S S C H 3 (13)» E Ç was fixed at -0.7 kcal/mole. As shown i n Figure 2, equation 4 f i t s the experimental data very well (median residual = 5.3%); we conclude, therefore, that the proposed mechanism does include a l l important reactions. Best f i t parameters are A Ç ^ = 3.04 χ 10~l cm molecule~ls~l, A5 = 5.53 χ 10" cm molecule , and E§/R = 7460K. b

b

2

3

31

3

_1

Implications f o r Atmospheric Chemistry Our results demonstrate that both the e f f e c t i v e rate constant ( k ) and the branching r a t i o (addition versus abstraction) f o r reaction (1) change dramatically as a function of temperature over the lower tropospheric temperature range 250-310K. I t should be be kept i n mind that, f o r purposes of atmospheric modeling, addition followed by decomposition back to OH + C H 3 S C H 3 i s treated as no reaction. The " e f f e c t i v e " addition pathway represents only those adduct molecules which are scavenged by O 2 . A majority of our experiments employed DMS-dg as the s u l f i d e reactant because more information concerning elementary reaction rates could be obtained i n this matter (this aspect of our study i s not discussed i n d e t a i l i n this paper). However, enough experiments were carried out with DMS to demonstrate that, within experimental uncertainty, k values for OH reactions with DMS and DMS-dg d i f f e r only by the difference i n the abstraction rates. The pressure dependence data i n a i r at 298K strongly supports t h i s approximation. Substituting the appropriate Arrhenius parameters into equation 4 leads to the following expression for the temperature dependence of obs 760 Torr a i r (units are cm molecule^s"!) :

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch011

o b g

o b g

k

f

o

r

t

h

e 0

H

+

D

M

S

r

e

a

c

t

i

o

n

i

n

3

1Q

k

=

°

1Q

Texp(-234/T) +8.64x10 exp(7230/T) + 2.68x10 exp(7810/T)

b S

n

1 . 0 4 x l 0 T + 88.1exp(7460/T) (6)

Values f o r k at ten degree i n t e r v a l s have been calculated from equation 6, as have branching ratios f o r abstraction ( B ) and addition ( B ^ ) . The branching ratios were calculated from the relationships Q b g

a b s

a

B

k

/ k

12

abs - l a o b s " 9. 6 x l O - e x p ( - 2 3 4 / T ) / ^ ^

Β ΑΆ = 1 - Β , add abs The results are tabulated i n Table I I .

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

(7)

(8)

139

The OH and Dimethyl Sulfide Reaction

HYNES AND WINE

2 op

1

1

1

I

I

1

1

I

I

Γ

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch011

~Ο····02

IL

I

2.6

3.0

3.4

I

=1

3.8

1000/T0O F i g u r e 2. R e s u l t s o b t a i n e d from u s i n g e q u a t i o n 4 t o s i m u l a t e t h e dependence o f k b on L O 2 ] l t e m p e r a t u r e f o r t h e OH + CD3SCD3 reaction. A l l b i m o l e c u l a r r a t e c o n s t a n t s were measured at a t o t a l p r e s s u r e o f 700 T o r r . The b e s t f i t parameters A Ç , A^, and E^/R a r e g i v e n i n t h e t e x t . E r r o r b a r s a r e 2σ, p r e ­ c i s i o n only. a

0

n

(

s

B

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

140

THE CHEMISTRY OF ACID RAIN Table I I .

τ (Κ)

10^k

Values

, (cm^molecule "'"s obs

250 260 270 280 290 300 310

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch011

f o r Κ , , Β , , and Β ,, obs abs add B

15.8 14.5 12.5 9.8 7.4 5.9 5.2

abs

B

0.24 0.27 0.32 0.42 0.58 0.75 0.87

add

0.76 0.73 0.68 0.58 0.42 0.25 0.13

Under a t m o s p h e r i c c o n d i t i o n s t h e a b s t r a c t i o n r o u t e i s thought t o r e s u l t i n production o f CH3S + H C 0 v i a the f o l l o w i n g r e a c t i o n sequence ( 1 7 , 2 0 ) : 2

OH + C H S C H 3

CH SCH 3

+ 0

2

CH SCH 0 3

2

2

2

3

—

->

2

4- M

>

+ NO

->

2

3

CH SCH 0 3

2

2

(la)

2

+ M

CH SCH 0 + N 0

(9)

2

(10)

CH S + CH 0 + M

(11)

3

>

CH SCH 0 + M 3

H 0 + CH SCH

2

3

2

The u l t i m a t e f a t e o f C H 3 S i s unknown, a l t h o u g h B a l l a , e t a l . (23) report d i r e c t k i n e t i c evidence that t h i s r a d i c a l reacts very r a p i d l y w i t h NO and N 0 b u t n e g l i g i b l y s l o w l y w i t h 0 . P o s s i b l e r o u t e s f o r the adduct + 0 r e a c t i o n i n c l u d e t h e f o l l o w i n g : 2

2

2

-> C H S C H 3

3

+ H0

(12a)

2

(DMSO)

OH

I

CH SCH 3

3

+ 0

2

-> C H 0 3

2

+ CH S0H

(12b)

3

C H S 0 H i s p r o b a b l y c o n v e r t e d t o C H S 0 H ( m e t h a n e s u l f o n i c a c i d ) by r e a c t i o n w i t h 0 w h i l e t h e a t m o s p h e r i c f a t e o f DMSO i s u n c l e a r . DMSO has a v e r y low v a p o r p r e s s u r e and may be r a p i d l y removed v i a heterogeneous processes. A t 298K o u r r e s u l t s demonstrate t h a t r e a c t i o n 1 i n one atmos­ p h e r e o f a i r p r o c e e d s 70% v i a a b s t r a c t i o n and 30% v i a ( i r r e v e r s i b l e ) addition. P h o t o o x i d a t i o n s t u d i e s have been r e p o r t e d by N i k i , e t a l . (18) and Hatakeyama and Akimoto (19), where 298K S 0 y i e l d s from OH i n i t i a t e d o x i d a t i o n o f C H 3 S C H 3 were r e p o r t e d t o b e 22% and 21%, respectively. L a r g e y i e l d s o f m e t h a n e s u l f o n i c a c i d were o b s e r v e d i n both studies. At present, there i s i n s u f f i c i e n t information to a l l o w S 0 p r o d u c t i o n t o be a s s o c i a t e d w i t h e i t h e r t h e a b s t r a c t i o n 3

3

3

2

2

2

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

11.

HYNES AND WINE

The OH and Dimethyl Sulfide Reaction

141

r o u t e o r the a d d i t i o n r o u t e . However, i t s h o u l d be n o t e d t h a t o u r r e s u l t s s u g g e s t t h a t a b s t r a c t i o n i s the dominant r e a c t i o n pathway f o r Τ > 300K w h i l e a d d i t i o n i s the dominant pathway f o r Τ < 270K. Hence, temperature dependent p r o d u c t a n a l y s i s s t u d i e s s h o u l d shed some l i g h t on t h e d e t a i l e d pathways f o r S 0 and CH^SO^H p r o d u c t i o n . 2

Acknowledgment T h i s work was s u p p o r t e d by t h e N a t i o n a l S c i e n c e g r a n t n o . ATM-82-17232.

Foundation through

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch011

Literature Cited 1. 2. 3. 4.

Cullis, D. F.; Hirschler, M. M. Atmos. Environ. 1980, 14, 1263. Moller, D. Atmos. Environ. 1984, 18, 19. Moller, D. Atmos. Environ. 1984, 18, 29. Barnard W. R.; Andreae, M. O.; Watkins, W. E.; Bingemer, H; Georgii, H.-W. J. Geophys. Res. 1982, 87, 8787. 5. Andreae, M. O.; Barnard, W. R.; Amnions, J . M. Ecol. Bull. 1983, 35, 167. 6. Andreae, M. O.; Raemdonck, H. Science 1983, 221, 744. 7. Cline, J . D.; Bates, T. S. Geophys. Res. Lett. 1983, 10, 949. 8. Turner, S. M.; Liss, P. S. J. Atmos. Chem. 1985, 2, 223. 9. Andreae, M. O.; Ferek, R. J.; Bermond, F.; Byrd, K. P.; Engstrom, R. T.; Hardin, S.; Houmere, P. D.; Le Marres, F.; Raemdonck, H.; Chatfield, R. B. J. Geophys. Res. 1985, 90, 12891. 10. Atkinson, R.; Perry, R. Α.; Pitts, Jr., J . Ν. Chem. Phys. Lett. 1978, 54, 14. 11. Kurylo, M. J. Chem. Phys. Lett. 1978, 58, 233. 12. Cox, R. Α.; Sheppard, D. Nature 1980, 289, 330. 13. Wine, P. H.; Kreutter, Ν. M.; Gump, C. Α.; Ravishankara, Α. R. J. Phys. Chem. 1981, 85, 2660. 14. MacLeod, H.; Poulet, G.; LeBras, G. J . Chem Phys. 1983, 80, 287. 15. Atkinson, R.; Pitts, Jr., J. N.; Aschmann, S. M. J. Phys. Chem. 1984, 88, 1584. 16. Martin, D.; Jourdain, J . L . ; LeBras, G. Int. J. Chem. Kinet. 1985, 17, 1247. 17. Wallington, T. J.; Atkinson, R.; Tuazon, E. C.; Aschmann, S. M. Int. J. Chem. Kinet. 1986, 18, 837. 18. Niki, H.; Maker, P. D.; Savage, C. M.; Breitenbach, L. P. Int. J. Chem. Kinet. 1983, 15, 647. 19. Hatakeyama, S.; Akimoto, H. J. Phys. Chem. 1983, 87, 2387. 20. Grosjean, D. Environ. Sci. Tech. 1984, 18, 460. 21. Hynes, A. J.; Wine, P. H.; Semmes, D. H. J. Phys. Chem. 1986, 90, 4148. 22. Wine, P. H.; Thompson, R. J.; Semmes, D. H. Int. J . Chem. Kinet. 1984, 16, 1623. 23. Balla, R. J.; Nelson, H. H.; McDonald, J. R. Chem. Phys. 1986, 109, 101. RECEIVED June 2, 1987

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Chapter 12

SO Oxidation by Hydrogen Peroxide in Suspended Droplets 2

W. A. Jaeschke and G. J. Herrmann

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch012

Center for Environmental Research, J. W. Goethe-University, P.O. Box 11 19 32, D-6000 Frankfurt am Main, Federal Republic of Germany

One of the most significant reactions in the context of acidity in rainwater is the SO2-oxidation by hydrogen peroxide in aqueous solution. Therefore a dynamic flowreactor was constructed, where SO2 removal rates could be investigated in the presence of H2O-containing droplets. The diameter of the suspended droplets was in the size range between 1 μm and 25 μm which is comparable to size distributions observed in atmospheric clouds or fogs. Pseudo first order rate constants of the SO2-Oxidation were mea­ sured at different pH-values. The H2O2-concentration in the droplets was varied between 2 x 10-5m and 10-2m. The obtained second order rate constants were strongly pH– dependent (1,48 x 10 I mol sec at pH 2 and 1,3 x 102 I mol sec at pH 5,5). At H2O2-concent rations above 10-3 m the microphysical transfer of SO2 via droplet interface became the rate determining step. From the experiments an accomodation-coefficient for SO2 could be calculated which was greater than 10 . 5

-1

-1

-1

-1

-1

Recent measurements of g a s - and l i q u i d - p h a s e c o n c e n t r a t i o n s of h y d r o g e n p e r o x i d e i n t h e t r o p o s p h e r e (1,2) s u b s t a n t i a t e t h e n o t i o n t h a t H2O2 is t h e major oxidant leading to the generation of s u l f u r i c a c i d in atmospheric m u l t i p h a s e systems l i k e fogs a n d c l o u d s . T h e o x i d a t i o n of S ( I V ) q r e q u i r e s a p h a s e t r a n s f e r o f g a s e o u s SO2 i n t o t h e s u s p e n d e d d r o p l e t s . T h i s t r a n s f e r represents a c h a i n of c o n s e c u t i v e processes i n c l u d i n g t r a n s p o r t of (S02)g to the d r o p l e t s , p h a s e - t r a n s f e r t h r o u g h the g a s - l i q u i d i n t e r f a c e , t r a n s ­ port of d i s s o l v e d S ( I V ) q in the l i q u i d phase and subsequent o x i d a t i o n of S ( I V ) a q t o S ( V I ) q by d i s s o l v e d H 2 O 2 . B e c a u s e o f t h e c o n s e c u t i v e n a t u r e o f t h i s m u l t i p h a s e o x i d a t i o n p r o c e s s the s l o w e s t step o f the c h a i n d e t e r m i n e s the o v e r a l l rate. Commonly the o v e r a l l rates of s u c h processes o c c u r i n g in a t m o s p h e r i c fog and c l o u d s a r e c a l c u l a t e d by l i n e a r e x t r a p o l a t i o n s f r o m k i n e t i c d a t a g a i n e d i n b u l k - s o l u t i o n e x p e r i m e n t s . It is d o u b t f u l whether the assumed l i n e a r r e l a t i o n s a r e e x i s t i n g in atmospheric systems, e s p e c i a l l y w i t h r e s p e c t t o t h e l i q u i d w a t e r c o n t e n t ( L W C ) o f fogs a n d c l o u d s b e c a u s e t h i s p a r a m e t e r is t h e r e s u l t o f t h e i n t e g r a l o v e r a s p e c t r u m a

a

a

0097-6156/87/0349-0142$06.00/0 © 1987 American Chemical Society

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

12.

S0

JAESCHKE AND HERRMANN

2

Oxidation by Hydrogen Peroxide

143

o f d r o p l e t s i n t h e r a n g e o f 1 ^im < r < 2 0 / j m . In t h i s s i z e r a n g e o f d r o p l e t s b o t h g a s - p h a s e a n d a q u e o u s - p h a s e m a s s t r a n s p o r t of S ( I V ) a q m a y b e c o m e the r a t e - d e t e r m i n i n g step b e c a u s e the o x i d a t i o n r e a c t i o n of S(IV)aq by H2O2 i s a s s u m e d t o be v e r y f a s t . In a d d i t i o n at S 0 2 - m a s s - a c c o m m o d a t i o n c o e f f i c i e n t s b e l o w 1 0 - 2 t h e i n t e r f a c i a l t r a n s p o r t o f S ( I V ) - s p e c i e s may a l s o g o v e r n the rate of the m u l t i p h a s e o x i d a t i o n r e a c t i o n (3).

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch012

Experimental In t h i s s t u d y t h e r a t e o f t h e o x i d a t i o n o f g a s e o u s SO2 by H2O2 c o n t a i n i n g d r o p l e t s in a m u l t i p h a s e s i m u l a t i o n e x p e r i m e n t was i n v e s t i g a t e d . For t h i s purpose a d y n a m i c f l o w r e a c t o r was designed in w h i c h the removal of ( S 0 2 ) g in the g a s - p h a s e and the f o r m a t i o n of S(VI)aq in the l i q u i d phase c o u l d be d e t e r m i n e d . T h e e x p e r i m e n t a l s e t u p ( F i g u r e 1) w a s s i m i l a r t o t h a t d e s c r i b e d i n p r e v i o u s p u b l i c a t i o n s ( 4 - 5 ) . C l e a n a i r , h u m i d i f i e d t o 94 % r . H . , w a s m i x e d w i t h c e r t a i n a m o u n t s o f ( S 0 2 ) g at t h e t o p o f t h e d y n a m i c t u b u l a r f l o w r e a c t o r . The r e a c t i o n m i x t u r e was led t h r o u g h the r e a c t o r w i t h a f l o w r a t e o f 25 l / m i n . D r o p l e t s c o n t a i n i n g H2O2 w e r e g e n e r a t e d by an u l t r a s o n i c d r o p l e t g e n e r a t o r and injected into the r e a c t o r . The d r o p l e t d i a m e t e r s r a n g e d f r o m 0.5 t o 1 2 . 5 Jum r a d i u s ( r ) ( F i g u r e 2 ) . A c o m p i l a t i o n o f e x p e r i m e n t a l d e t a i l s is g i v e n i n T a b l e I. T a b l e I: Pa r amete r

Provided

S0

Cyl inder

2

H 0 2

by

Stok s o l u t i o n

2

HCI

PH Droplet

Experimental

details Monitored

Range 300 2 · 10"

8500 ng/m

-

10"

2

-

5.5

0,5

-

1 2 , 5 /jm

2

3

mol/l

5

Fl u o r e s c e n c e Titration Titration

size

(radius)

Ultra sonic

Light scattering (Partoscope)

. droplet L i q u i d Water

generator

8 · 10"

3

-

7,5

ml/m

94

%

3

Calculated

content Rel.

Humid.

Water

vapour

Temperature

Thermostat.

Hum. indicator (Veisala)

sou rce 25

°C

system

In o r d e r t o a v o i d w a l l e f f e c t s by c o n d e n s a t i o n o f w a t e r v a p o u r at r.H. 100 % i t w a s n e c e s s a r y t o l o w e r t h e v a p o u r p r e s s u r e o f t h e generated droplets u s i n g a n e u t r a l s a l t . Sodium c h l o r i d e (high p u r i t y ) was c h o s e n a n d the c o n c e n t r a t i o n of the d i l u t e d r e s e r v o i r s o l u t i o n of t h i s s a l t w a s set t o 1.5 m o l l"1 s o t h a t t h e d r o p l e t s g e n e r a t e d f r o m t h i s s o l u t i o n w e r e i n t h e r m o d y n a m i c e q u i l i b r i u m w i t h t h e s u r r o u n d i n g m o i s t a i r o f 94 % r . H . i n t h e r e a c t o r . T h e p H - v a l u e o f t h e s o l u t i o n w a s a l t e r e d by a d d i t i o n o f d i f f e r e n t m l - a m o u n t s o f HCI (25%, r e a g e n t g r a d e ) . Each m e a s u r i n g point in the f l o w reactor c o r r e s p o n d s to a f i x e d t r a n s p o r t time of the m u l t i p h a s e m i x t u r e in the r e a c t o r . The t r a n s p o r t

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

THE CHEMISTRY OF ACID RAIN

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch012

144

ZUF/SFB73/001-1/86/D,

F i g u r e 1. Scheme of t h e e x p e r i m e n t a l set up u s e d f o r k i n e t i c s t u d i e s of the S02~oxidation in the presence of H 2 0 2 - c o n t a i n i n g d r o p l e t s . 1. C o m p r e s s o r , 2 . A i r C l e a n e r , 3 . M a s s F l o w C o n t r o l l e r , 4 . V a p o r i z e r , 5 . S 0 2 - s o u r c e , 6. N e b u l i z e r , 7. Pump, 8 . S t o c k s o l u t i o n , 9 . P a r t o s c o p e A , 10. R e a c t i o n c h a m b e r , 11. T h e r m o s t a t , 12. H u m i d i t y Sensor, 13. S 0 2 D e t e c t i o n , 14. S 0 4 - S a m p l i n g , 1 5 . R e c o r d e r .

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

12.

S0

JAESCHKE AND HERRMANN

7

dl dD 10000,25 I /min

3

\xm

-1,5

3

μπΓ ] 1

3

χ10

400·

.1,0χ10

200·

• 0 . 5 χ 103

0

cm"

3

-2,0χ10

600.

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch012

I

dD

800.

145

Oxidation by Hydrogen Peroxide

3

0 0,5

800-

l/min

• 4 χ 10

3

600-

, 3 χ 10

400-

. 2 χ10

200-

• 1 χ 10

0-

3

3

3

- 0

800 «

•2.0 χ 1 0

4

600 ·

• 1.5x10

4

400 •

• 1,0 χ 1 0

200 ·

0,5

0 ·

χ10

4

;

0

600 U5x10^ 400

H

200· 1 χ 10 10

15

20

25

ι 5

10

1 15

1 « 20

25 D ( μ π ι )

-ZUF/SFB73/001-2/86/D«

F i g u r e 2. Size d i s t r i b u t i o n of d r o p l e t s used in the k i n e t i c s t u d i e s . The s i z e d i s t r i b u t i o n w a s m e a s u r e d by a P A R T O S C O P E A at t h r e e d i f f e r e n t f l o w rates in the n e b u l i z e r .

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

146

T H E CHEMISTRY OF ACID RAIN

time is i d e n t i c a l w i t h the p e r i o d of t i m e i n w h i c h t h e ( S 0 ) g c o u l d r e a c t w i t h the H 2 0 2 - c o n t a i n i n g d r o p l e t s . C o n s i d e r i n g the flow rate and the g e o m e t r y o f t h e f l o w r e a c t o r , t h e t o t a l t r a n s p o r t t i m e w a s 340 s e c . When d i s s o l v e d S ( I V ) q i s o x i d i z e d i n t h e d r o p l e t s , t h e a b s o r p t i o n e q u i l i b r i u m between the S ( I V ) a q - c o n c e n t r a t i o n and the ( S 0 2 ) g - c o n c e n t r a t i o n i s d i s t u r b e d . It is c o n t i n u o u s l y r e - e s t a b l i s h e d f o l l o w i n g H e n r y ' s l a w a n d t h e w e l l - k n o w n d i s s o l u t i o n e q u i l i b r i a o f S(IV) i n t h e l i q u i d p h a s e . T h u s a ( S 0 2 ) g - c o n c e n t r a t i o n - g r a d i e n t between t h e i n l e t a n d t h e o u t l e t of t h e r e a c t o r is f o r m e d , w h i c h is r e l a t e d to t h e t r a v e l time of the m i x t u r e . 2

a

Theory

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch012

For

kinetic calculations only S(IV)

a

=

q

S0

the ·

2

S(IV)aq c o n c e n t r a t i o n is

H 0

+ HSO3-

2

+

considered

S0 =

(1)

3

T h e r a t i o o f t h e t h r e e S ( I V ) q s p e c i e s is p H - d e p e n d e n t . It c a n be c a l c u l a t e d f r o m the measured ( S 0 2 ) g by Henry's law e q u i l i b r i u m c o n s t a n t HSO2 " " k n o w n f i r s t a n d s e c o n d i o n i z a t i o n c o n s t a n t s KD1 a n d KD2. a

a n o

t

n

e

w

e

( S 0 S ( I V )

a

q

=

( S 0

S ( I V )

a

q

=

( S 0

2

)

g

. H

)

g

·

S

o

*

2

2

) H 0 ^ j - i g

S

K

2

H

S

(1

0 2

S ( I V )

a

=

q

( S 0

2

)

g

·

Hso

+

2

D1

K

D

( S 0

1

*

K

— [H ]

+

+

2

)

g

H ^

S

o

2

K

D

1

K

D

2

D1 D1 — — ) [ H l K

+

2

(2)

2

H S 0 i n E q u a t i o n 2 i s d e f i n e d as a p s e u d o H e n r y ' s l a w c o e f f i c i e n t that depends on the h y d r o g e n ion c o n c e n t r a t i o n and encompasses the t o t a l i t y of t h e d i s s o l v e d S ( I V ) q s p e c i e s ( 3 ) . The r a t i o between the s p a t i a l d i f f e r e n c e of S(IV)aq in the r e a c t o r , w h i c h c a n be c a l c u l a t e d f r o m t h e ( S 0 2 ) g - g r a d i e n t , a n d t h e c o r r e s p o n d i n g t r a v e l - t i m e i n t e r v a l i s e q u a l t o t h e r e m o v a l r a t e R: 2

a

d[S(IV)]

d [ S ( V I ) ]

R =

a

q

= dt

(3) dt

As the g r a d i e n t of S ( I V ) q is r e l a t e d to the o x i d a t i o n p r o d u c t S ( V I ) q a p p e a r i n g i n t h e d r o p l e t s an i n v e r s e g r a d i e n t o f t h e S ( V I ) a q - c o n c e n t r a t i o n m u s t be n o t i c e a b l e . T h e r e l a t i o n b e t w e e n S ( I V ) - a n d S ( V I ) - c o n c e n t r a t i o n a

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

a

12.

S0

JAESCHKE AND HERRMANN

Oxidation by Hydrogen Peroxide

2

gradients at any given t r a v e l time of the m i x t u r e can be expressed by the f o l l o w i n g general Equation: d[S(IV)]

d[S(VI)]

a q

R =

= dt

ki

a q

d

= ^[5(ΐν)

β ρ

]

(4)

dt

= 1st p r o p o r t i o n a l i t y factor = const.

In order t o determine k*i and the exponent oL in Equation 4 the removal of S(IV) q and the formation of S(VI)aq should be measured d u r i n g the experiments. The r a t e - c o e f f i c i e n t k i was investigated as a f u n c t i o n of d i f f e r e n t experimental c o n d i t i o n s w h i c h a r e listed below: - concentration of l i q u i d water in the reactor (L) - c o n c e n t r a t i o n of hydrogen peroxide in the droplets ([H202laq) - pH of the droplets ([H ] q) These parameters have been v a r i e d d u r i n g several separate e x p e r i ­ mental runs. The r e l a t i v e humidity always was kept constant at 94 % and the temperature in the reactor was set to 25°C. The dependence of the o v e r a l l t r a n s f o r m a t i o n rate R in Equation 4 from the l i q u i d water content L can be expressed by an exponential dependence of k i from L:

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch012

a

+

a

ki k2 β

= k2 x \f

(5)

= 2nd p r o p o r t i o n a l i t y factor = const.

The exponent β represents a possible n o n - l i n e a r relationship between the removal rate R and the l i q u i d water content w h i c h c o u l d be caused by mass-transport-1 imitations. More precisely L is defined by the integral over the size d i s t r i b u t i o n of the droplets used in the experiments.

7Γ = ^

f D

d

3

* N

d

D

The dependence of R from the concentration of H2O2 i n the droplets can also be expressed by an exponential equation: k

k y

3

2

= k

3

χ [H 0 ] 2

2

a q

(6)

= 3 r d p r o p o r t i o n a l i t y factor = const.

were 2f represents the reaction order with respect to the concentration of the o x i d a n t . k represents the rate c o e f f i c i e n t of the o x i d a t i o n reaction in the multiphase system at.a c e r t a i n oH-value·. . 3

American chemical Society. Library 16th N.W.R., el al.; In The Chemistry1155 of Acid Rain;St., Johnson, Washington, 20036 ACS Symposium Series; American ChemicalO.C. Society: Washington, DC, 1987.

148

THE CHEMISTRY OF ACID RAIN

The i n f l u e n c e of the p r o t o n c o n c e n t r a t i o n [ H ] in the d r o p l e t s on o x i d a t i o n o f S ( I V ) q c a n be e x p r e s s e d a s :

the

+

a

ζ k

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch012

k4 ($

3

=

k

χ

4

[ H

+

l

a

(7)

q

= 4th p r o p o r t i o n a l i t y = const,

factor

w h e r e 8 represents the r e a c t i o n o r d e r w i t h respect to the c o n c e n t r a t i o n of hydroni um-ions i n t h e i n d i v i d u a l d r o p l e t s . k4 r e p r e s e n t s the rate c o e f f i c i e n t of the m u l t i p h a s e r e a c t i o n in the p H - r a n g e under i n v e s t i g a ­ tion. In s u m m a r y the dependence of the t r a n s f o r m a t i o n of S(IV)aq to S ( V I ) a q i n t h e s y s t e m c a n be e x p r e s s e d b y c o m b i n i n g E q u a t i o n 2, 4, 5, 6 and 7 as:

-dS[(IV)]

a q

dt

=

k [(S02)gHso ] 4

2

* L *

[ H

2

0

2

l

a

q

[ H

+

l

a

(8)

q

In t h i s e q u a t i o n t h e b r a c k e t s i n d i c a t e m o l a r c o n c e n t r a t i o n s f o r l i q u i d p h a s e s p e c i e s . T h e c o n c e n t r a t i o n o f ( S 0 2 ) g m u s t be g i v e n a s p a r t i a l p r e s s u r e and H*S02 represents the e f f e c t i v e Henry's law constant of S02 c o n s i d e r i n g t h e d i s s o l u t i o n e q u i l i b r i a r e a c t i o n s o f S ( I V ) . A s t o be seen f r o m Equation 8 the t r a n s f o r m a t i o n of ( S 0 2 ) g to S ( V I ) q in a m u l t i p h a s e s y s t e m m u s t be m e a s u r e d a s a f u n c t i o n o f ( S 0 ) L, [ H 2 0 2 l a q a n d [ H ] i n o r d e r t o d e t e r m i n e t h e c o n s t a n t k4 a n d t h e e x p o n e n t s * j3 X a n d £ . a q

a

2

+

g /

/

a

q

t

Results and D i s c u s s i o n In F i g u r e 3 t h e d e c a y s o f t h e S ( I V ) q - c o n c e n t r a t i o n s at v a r i o u s l i q u i d water contents a r e plotted in a s e m i - l o g a r i t h m i c s c a l e a g a i n s t the r e a c t i o n t i m e . T h e e x p e r i m e n t s w e r e p e r f o r m e d at p H = 4 a n d [ H 2 0 2 ] a q = 1 0 " 3 m o l 1-1. T h e f o r m a t i o n o f S ( V I ) a q is p l o t t e d u s i n g t r a n s f o r m a t i o n v a r i a b l e s i n o r d e r t o g a i n c o m p a r a b l e v a l u e s w i t h t h e i n v e r s e g r a d i e n t o f S ( V I ) q . In a l l cases l i n e a r dependences a r e o b t a i n e d w h i c h means that the exponent d - i n E q u a t i o n 8 is e q u a l t o o n e . T h u s t h e S ( I V ) - r e m o v a l c a n be c o n s i d e r e d k i n e t i c a l l y as a p s e u d o - f i r s t - o r d e r r e a c t i o n w i t h r e s p e c t t o S ( I V ) q . T h e d i f f e r e n t s l o p e s o f t h e s t r a i g h t l i n e s i n F i g u r e 3 c o r r e s p o n d to d i f f e r e n t v a l u e s of the l i q u i d water c o n t e n t . These slopes d i r e c t l y represent v a l u e s of k i s i n c e i * = 1 . They a r e c o m p i l e d together w i t h the r e s p e c t i v e v a l u e s of the l i q u i d water content in the t a b l e b e y o n d F i g u r e 3. In o r d e r t o d e t e r m i n e t h e v a l u e o f t h e e x p o n e n t β i n E q u a t i o n 5 t h e values of k i a r e plotted in a l o g - l o g d i a g r a m v e r s u s the c o r r e s p o n d i n g l i q u i d water content (L) (Figure 4). From the slope of the linear a

a

a q

a

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch012

12.

JAESCHKE AND HERRMANN

S0

Oxidation by Hydrogen Peroxide

2

200

149

300 Verweilzeir ( s ]

Symbol S(IV) Ο • χ

S(VI).

ml m

-1

-3

8.3x10 9.1x10" 8.3x10" 3x10 -1 5x10" lxlOp 5xlO L

< 1 0

-4 n chromatography (IC) f o r NO^ , C l , SO^ , Na , and NH. , by flameless atomic absorption spectroscopy (AAS) f o r Pb, and by instrumental neutron a c t i v a t i o n a n a l y s i s (INAA) f o r the s o l u b l e f r a c t i o n of Na, A l , T i , Ca, Cu, V, Mn, In, Br, Sb, As, and Au. 50 ml of the f i l t e r e d =

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

THE CHEMISTRY OF ACID RAIN

206

rainwater was f r o z e n , f r e e z e - d r i e d to r e s i d u e , r e - d i s s o l v e d i n U l t r e x HNO^ and d e i o n i z e d H 0, t r a n s f e r e d to polyethylene Bags, and again f r e e z e - d r i e d to r e s i d u e f o r INAA. I r r a d i a t i o n with thermal neutrons was performed at the Los Alamos Omega West r e a c t o r . The f i r s t i r r a d i a t i o n (shorts) was f o r 5 minutes with a f l u x of 6 * 10 n/cm /sec. Later there was a s e c o n d , i r r a d i a t i o n (longs) f o r 4 hours with a f l u x of 9.7 * 10 n/cm /sec. Shorts were counted on a Ge(Li) d e t e c t o r f o r 5 minutes a f t e r a 5 min. decay and f o r 19 min. a f t e r a 20 min. decay. Longs were counted on a Ge detector f o r 4 hours a f t e r a 3-5 day decay and 8 hours a f t e r a 30 day decay. The f i l t e r s used to remove p a r t i c u l a t e matter from the rainwater samples a l s o were analyzed by INAA to determine the i n s o l u b l e f r a c t i o n of t r a c e metal s p e c i e s . Two pre-washed (ΗΝΟ^, then repeated d i s t i l l e d , d e i o n i z i e d H 0 r i n s e s u n t i l c o n d u c t i v i t y was l e s s than 1 uS/cm) funnel and b o t t l e c o l l e c t o r s were deployed at each s i t e i n response to a weather f o r e c a s t . The s i t e s were operated by community c o l l e g e students, S e a t t l e Water Department personnel, high school teachers and students, and U n i v e r s i t y of Washington personnel. At one ' c o n t r o l s i t e which we operated ourselves a t a r e p r e s e n t a t i v e but p a r t i c u l a r l y i d e a l l o c a t i o n (behind a locked gate on a l a r g e grassy f i e l d which was w e l l removed from t r a f f i c and combustion s o u r c e s ) , ten c o - l o c a t e d samples were c o l l e c t e d to determine the uncontaminated· experimental u n c e r t a i n t i e s . These measurements q u a n t i f y the o v e r a l l experimental u n c e r t a i n t i e s due to the r a i n sampler p r e p a r a t i o n , handling, and t r a n s p o r t to the f i e l d s i t e , rainwater c o l l e c t i o n , sample f i l t r a t i o n and storage, and the a n a l y t i c a l procedures. Table 1 presents these u n c e r t a i n t i e s f o r the 10 c o - l o c a t e d samplers. For r a i n amount, H , S0 "~, As, Sb, Mg, Cl"", and NO^" the measured f i e l d c o l l e c t i o n and chemical a n a l y s i s combined u n c e r t a i n t i e s represented 4-13 percent of the measured c o n c e n t r a t i o n s . For Na , Pb, and Ca the measured u n c e r t a i n t i e s represented 22-26 percent of the measured concentrations.

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch017

2

2

1

1

4

Data Screening The p a i r e d samples which were c o l l e c t e d at each s i t e were compared to the r e s u l t s of the 10 sampler experiment to d e t e c t samples of poor q u a l i t y . This procedure was u t i l i z e d to insure than experimental u n c e r t a i n t i e s d i d not c o n t r i b u t e to the observed v a r i a t i o n i n composition. The variance f o r each species l i s t e d i n Table 1 from the c o n t r o l s i t e was s t a t i s t i c a l l y compared to the variance f o r the p a i r e d samples at a l l s i t e s with an F - t e s t . One of the p a i r e d measurements at a s i t e was r e j e c t e d i f t h e i r variance was s i g n i f i c a n t l y (p UVALDA, GEORGIA Ο => LANCASTER, KANSAS X => UNDERHILL, VERMONT

yo

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oo

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(a) Hydrogen ο

30 -

ο

ο

20 χ

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Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch020

χ

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χ + χ ο — ° *χ +

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τ — m — ι — ι — m —-Ο-τΧ ι—ι—τ—ι—ι—ι—ι SEP OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP OCT 1983 - 1984

(b) Sulfate

χ Χ -χ*

Ο ο

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\ o*xx +

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F i g u r e 3. V a r i a t i o n o f p e r c e n t r e l a t i v e b i a s (weekly d e r i v e d measured/weekly d e r i v e d ) w i t h time f o r hydrogen i o n and s u l f a t e a t t h e G e o r g i a , Kansas and Vermont s i t e s .

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

20.

TOPOL ET AL.

Weekly and Daily

Wet Deposition

Sampling

239

Results

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch020

g e n e r a l l y y i e l d s h i g h e r a n n u a l mean c o n c e n t r a t i o n s t h a n d a i l y sampling, b u t the d i f f e r e n c e s a r e s m a l l , a r e assumed t o be due t o method and n o t s i t e t o s i t e d i f f e r e n c e , and a r e n o t c o n s i d e r e d practically significant. However, a network t h a t changes i t s samp l i n g s c h e d u l e w i l l see t h e b i a s e f f e c t and, a l t h o u g h s m a l l , i t can i n t e r f e r e with trend a n a l y s i s . E f f e c t o f Season on Method B i a s . The e f f e c t o f season on t h e conc e n t r a t i o n b i a s was a l s o examined. F o r t h e f a l l q u a r t e r , t h e 1983 and 1984 d a t a were combined. The median, mean and r e l a t i v e mean b i a s e s f o r t h e weekly d e r i v e d minus weekly measured c o n c e n t r a t i o n s ( f o r a l l s i t e s grouped t o g e t h e r ) and t h e r e s p e c t i v e W i l c o x o n and paired t - t e s t r e s u l t s are presented i n Table I I . S i g n i f i c a n t b i a s i s seen from e i t h e r t h e W i l c o x o n o r t - t e s t f o r n i t r a t e and c a l c i u m i n t h e s p r i n g , and f o r hydrogen i n t h e summer. However,_the f a l l season r e v e a l s s i g n i f i c a n t b i a s by b o t h t e s t s f o r H , SO^, C I , Na , Ca and Mg and f o r K by t h e W i l c o x o n t e s t o n l y . The measured weekly c o n c e n t r a t i o n s a r e l a r g e r t h a n t h e d e r i v e d ones i n a l l t h e s e s i g n i f i c a n t b i a s cases except f o r H . Higher C a and M g concent r a t i o n s , w h i c h g e n e r a l l y a r e from b a s i c s o i l d u s t , a r e e x p e c t e d t o y i e l d lower a c i d i t y ( H ) i n a l l samples. A one-way ANOVA d e t e c t e d s i g n i f i c a n t d i f f e r e n c e s i n b i a s among t h e seasons f o r N O 3 , C I and Mg* o n l y , as shown i n T a b l e I I . The r e s u l t s i n d i c a t e t h a t a m a j o r i t y o f t h e a n a l y t e s show s i g n i f i c a n t b i a s i n t h e f a l l , and t h e l a r g est r e l a t i v e b i a s f o r a l l observables a l s o occurs i n the f a l l . The s i g n i f i c a n t f a l l season b i a s e s a r e d i f f i c u l t t o e x p l a i n . F o r t h e f o u r major i o n s , t h e r e l a t i v e b i a s e s a r e under 13%. The l a r g e b i a s f o r p o t a s s i u m i n d i c a t e s t h a t t h e r e a r e sampling p r o b l e m s , p o s s i b l y due t o a d s o r p t i o n - d e s o r p t i o n from t h e p l a s t i c b u c k e t . These r e s u l t s i n d i c a t e t h a t t h e b i a s i n c o n c e n t r a t i o n between weekly and d a i l y samples i s s i m i l a r f o r most of t h e c o n s t i t u e n t s i n a l l seasons b u t the f a l l . +

+

+

+ 2

+ 2

+

2

Summary and The * *

*

*

Conclusions

r e s u l t s of t h i s study i n d i c a t e that C o n c e n t r a t i o n s o f weekly c o l l e c t e d samples a r e g e n e r a l l y h i g h e r t h a n t h o s e of t h e d e r i v e d weekly samples. No c o r r e s p o n d e n c e o c c u r s between c o n c e n t r a t i o n b i a s f o r t h e major i o n s and t h e b i a s i n p r e c i p i t a t i o n volume c o l l e c t e d . Therefore, the o b s e r v e d b i a s e s cannot be a t t r i b u t e d t o e v a p o r a t i o n . A l t h o u g h many i o n i c c o n c e n t r a t i o n b i a s e s between t h e weekly measured and d e r i v e d samples a r e s t a t i s t i c a l l y s i g n i f i c a n t , t h e i r magnitude i s g e n e r a l l y 0.8 cm Rain Snow

6 156 78 117 1.5

22 138 59 36 0.61

7 398 43 88 2.1

18 1179 27 61 2.3

5 347 44 28 0.64

3 1081 24 15 0.63

where e v e n t s a r e s e p a r a t e d b y p r e c i p i t a t i o n d e p t h . Based on t h i s d i v i s i o n , t h e N0 - c o n c e n t r a t i o n s a r e n o t h i g h e r i n snow events t h a n i n r a i n events. A m u l t i p l e r e g r e s s i o n a n a l y s i s was a l s o performed t o d e t e r m i n e t h e e f f e c t o f p r e c i p i t a t i o n depth and p r e c i p i t a t i o n t y p e (snow v s . r a i n ) on t h e N0 - c o n c e n t r a t i o n . C l o u d temperature was used as a measure o f p r e c i p i t a t i o n t y p e and was c a l c u l a t e d as d e s c r i b e d i n t h e next s e c t i o n . A l t h o u g h N 0 - c o n c e n t r a t i o n s were found t o be i n v e r s e l y c o r r e l a t e d w i t h p r e c i p i t a t i o n volume, t h e r e was no s i g n i f i c a n t c o r r e l a t i o n between N 0 - c o n c e n t r a t i o n s and t e m p e r a t u r e . T h e r e f o r e , a t t h i s l o c a t i o n , t h e lower water c o n t e n t o f snow events 3

3

3

3

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

21.

Chemistry

DASCH

of Wintertime

Wet

245

Deposition

compared t o r a i n events a p p e a r s s u f f i c i e n t t o e x p l a i n t h e h i g h e r NO3- c o n c e n t r a t i o n s found i n snow; t h e r e i s no e v i d e n c e t h a t HN0 i n t h e a i r i s scavenged more e f f i c i e n t l y by snow than by r a i n . 3

S 0 - ~ C o n c e n t r a t i o n s . Based on Tables I and I I , t h e r e c a n be no doubt t h a t S 0 - ~ l e v e l s i n w i n t e r r a i n a r e f a r h i g h e r t h a n i n snow a t t h i s l o c a t i o n , d e s p i t e d i f f e r e n c e s i n p r e c i p i t a t i o n d e p t h . Two p o s s i b l e sources o f the d i f f e r e n c e are t h e f o l l o w i n g : higher ambient S 0 and S 0 - - c o n c e n t r a t i o n s a v a i l a b l e f o r s c a v e n g i n g d u r i n g r a i n events o r h i g h e r S 0 t o S 0 - - c o n v e r s i o n d u r i n g r a i n e v e n t s . These p o s s i b i l i t i e s w i l l be c o n s i d e r e d f u r t h e r . Ambient c o n c e n t r a t i o n s o f p a r t i c l e s and gases were measured a t ground l e v e l d u r i n g t h e 1983-84 and 1984-85 w i n t e r s t o d e t e r m i n e i f h i g h e r c o n c e n t r a t i o n s were a v a i l a b l e f o r scavenging d u r i n g w i n t e r r a i n s and snows. S i n c e t h e ambient d a t a d i d not c o r r e s p o n d t o p a r t i c u l a r p r e c i p i t a t i o n e v e n t s , they were r o u g h l y grouped i n t o snow p e r i o d s and r a i n p e r i o d s . The r e s u l t s o f t h i s g r o u p i n g a r e seen i n T a b l e I I I . Based on a Student T - t e s t , t h e o n l y s t a t i s t i c a l l y s i g n i f i c a n t d i f f e r e n c e s a t t h e 95% c o n f i d e n c e l e v e l i s f o r N 0 which i s A

4

2

4

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch021

2

4

2

T a b l e I I I . C o n c e n t r a t i o n s o f P a r t i c l e s and Gases i n A i r d u r i n g R a i n P e r i o d s and Snow P e r i o d s Ug/m ) 3

Rain

so -4

HN03 2

2

Snow P e r i o d s 3.5±1.9 4.211.9 1.310.78 22110 24110

3.512.1 3.5±1.3 1.4±0.96 19±9.9 17±7.9

N03-

so N0

Periods

h i g h e r d u r i n g snow p e r i o d s . The s u l f u r s p e c i e s a r e a c t u a l l y somewhat h i g h e r d u r i n g snow p e r i o d s than d u r i n g r a i n p e r i o d s . Theref o r e , t h e h i g h e r S 0 - - l e v e l s i n r a i n cannot be a t t r i b u t e d t o h i g h e r l e v e l s o f ambient s u l f u r s p e c i e s a v a i l a b l e f o r s c a v e n g i n g . The o r i g i n o f t h e storm system c o u l d a l s o l e a d t o d i f f e r e n c e s i n p r e c i p i t i o n c o n c e n t r a t i o n s . S u l f u r e m i s s i o n s w i t h i n 480 km o f Warren a r e t w i c e a s h i g h from t h e south o r e a s t as from t h e n o r t h o r west, and N 0 e m i s s i o n s a r e a l m o s t t e n t i m e s h i g h e r from t h e e a s t , south o r west a s from t h e n o r t h ( 3 ) . S i n c e more snow events than r a i n events were from t h e c l e a n e r n o r t h , t h i s might e x p l a i n t h e lower S 0 - ~ l e v e l s i n snow t h a n i n r a i n . To e v a l u a t e t h i s , t h e ground l e v e l wind d i r e c t i o n was d e t e r m i n e d d u r i n g each p r e c i p i t a t i o n p e r i o d based on t h e L o c a l C l i m a t o l o g i c a l D a t a from D e t r o i t M e t r o p o l itan Airport. The d a t a was d i v i d e d i n t o N, E, S, and W q u a d r a n t s . E v e n t s w i t h a wind s h i f t o f more than 100° were e x c l u d e d from t h e analysis. The volume-weighted mean c o n c e n t r a t i o n s a r e shown i n T a b l e IV. Note t h a t t h e number o f events i s s m a l l from some d i r e c tions . The N O 3 - c o n c e n t r a t i o n s a r e lower i n r a i n than snow from a l l d i r e c t i o n s , b u t t h a t can be e x p l a i n e d based on t h e lower p r e c i p i t a t i o n depth i n snows than r a i n s . The S 0 - ~ l e v e l s a r e c o n s i d e r a b l y 4

2

4

4

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

246

THE CHEMISTRY OF ACID RAIN

T a b l e IV.

E f f e c t o f Wind D i r e c t i o n on P r e c i p i t a t i o n C o n c e n t r a t i o n (Meq/L) S0 --

NO 3

4

North East South West

Rain

Snow

Rain

Snow

44 ( 1 ) * 63 (9) 72 (10) 48 (3)

20 15 39 47

16 (1) 35 (9) 31 (10) 28 (3)

20 46 54 48

(5) (4) (7) (2)

(5) (4) (7) (2)

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch021

* V a l u e s i n p a r e n t h e s e s a r e t h e number o f events r e p r e s e n t e d by each mean.

h i g h e r i n r a i n t h a n i n snow f o r t h r e e d i r e c t i o n s . T h e r e f o r e , t h e g r o u n d - l e v e l wind d i r e c t i o n cannot e x p l a i n t h e h i g h e r s u l f a t e l e v e l s i n r a i n than snow. I t i s a l s o p o s s i b l e t h a t snow scavenges p a r t i c u l a t e S 0 - - l e s s e f f i c i e n t l y t h a n r a i n , b u t t h i s cannot be d e t e r m i n e d from t h i s d a t a s e t . However, i n d i c a t i o n s from t h e l i t e r a t u r e suggest t h a t t h e r e v e r s e i s t r u e . Knutson e t a l . (9) r e v i e w e d s e v e r a l s t u d i e s showi n g t h a t snow scavenged p a r t i c l e s f a s t e r t h a n r a i n . Chan and Chung (10) a l s o found a h i g h e r s c a v e n g i n g r a t i o f o r S 0 - - p a r t i c l e s by snow than r a i n . The o t h e r p o s s i b i l i t y t o be c o n s i d e r e d i s t h a t o f g r e a t e r S 0 t o S 0 - - c o n v e r s i o n i n c l o u d water d u r i n g r a i n e v e n t s t h a n d u r i n g snow e v e n t s . The c o n v e r s i o n r a t e w i l l depend on a v a r i e t y o f f a c t o r s i n c l u d i n g t h e S0 c o n c e n t r a t i o n , the c o n c e n t r a t i o n of oxidants such as ozone o r hydrogen p e r o x i d e , and t h e i n c o r p o r a t i o n and r e a c t i o n o f t h e s e s p e c i e s i n c l o u d hydrometeors. The c o n c e n t r a t i o n s o f S 0 and o x i d a n t s a r e u n l i k e l y t o show l a r g e v a r i a t i o n s from December t o e a r l y A p r i l when t h e s e samples were c o l l e c t e d . More l i k e l y , t h e f a c t o r of importance i s t h e s t a t e of the p r e c i p i t a t i o n i n the c l o u d , whether f r o z e n o r l i q u i d , o r t h e r e l a t i v e l e n g t h o f t i m e i n each s t a t e . The s t a t e o f t h e p r e c i p i t a t i o n would a f f e c t b o t h t h e i n c o r p o r a t i o n and r e a c t i o n o f s u l f u r s p e c i e s i n c l o u d d r o p s . F i r s t , d u r i n g t h e f r e e z i n g p r o c e s s , most o f t h e d i s s o l v e d S 0 i s l o s t from t h e d r o p as i n d i c a t e d by experiments o f I r i b a r n e e t a l . ( 1 1 ) . S e c o n d l y , t h e o x i d a t i o n o f t h e r e m a i n i n g d i s s o l v e d S 0 w i t h i n an i c e c r y s t a l w i l l be r e t a r d e d compared t o r e a c t i o n w i t h i n a d r o p l e t . I t has been argued t h a t t h e p r e c i p i t a t i o n s t a t e i s unimportant i n w i n t e r s t o r m s , because a l l c l o u d m o i s t u r e would be e x p e c t e d t o be f r o z e n a t c l o u d l e v e l s , whether i t appeared a s r a i n o r snow a t ground l e v e l ( 5 ) . However, S c o t t found h i g h e r S 0 ~ - l e v e l s i n rimed s n o w f l a k e s where growth o c c u r e d by a c c r e t i o n o f water d r o p l e t s than i n unrimed snowf l a k e s where growth o c c u r r e d by vapor d e p o s i t i o n ( 1 2 ) . We i n v e s t i g a t e d t h e e f f e c t o f t h e temperature i n t h e c l o u d s f o r t h e storms o f t h e f i r s t two w i n t e r s u s i n g t h e upper a i r d a t a from F l i n t , MI. F o r each p r e c i p i t a t i o n e v e n t , t h e c l o u d r e g i o n was r o u g h l y d e f i n e d as t h e a l t i t u d e s w i t h r e l a t i v e h u m i d i t i e s g r e a t e r t h a n 90%. The median temperature i n t h i s a l t i t u d e range was n e x t d e t e r m i n e d . The temperature f o r t h e snow events ranged from -14° C 4

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t o -4° C w i t h a median o f -10° C whereas t h e r a i n o r mixed e v e n t s ranged i n t e m p e r a t u r e from -15° C t o 11° C w i t h a median o f 1° C. Based on t h e s e t e m p e r a t u r e s i t appears t o be u n t r u e t h a t most c l o u d l a y e r s a r e f r o z e n i n the w i n t e r a t t h i s l o c a t i o n , s i n c e drops c a n e a s i l y e x i s t i n a supercooled s t a t e a t these temperatures (13). F i g u r e 1 shows a p l o t o f the S 0 - - / N 0 - r a t i o i n the p r e c i p i t a t i o n as a f u n c t i o n o f c l o u d t e m p e r a t u r e . A h i g h l y s i g n i f i c a n t , p o s i t i v e c o r r e l a t i o n e x i s t s (r=0.75) between the S0 --/N0 - r a t i o and the t e m p e r a t u r e i n the c l o u d . The r a t i o o f S0 --/N0 - i s used, r a t h e r than S 0 - ~ c o n c e n t r a t i o n s , t o n o r m a l i z e f o r t h e e f f e c t o f p r e c i p i t a t i o n d e p t h ; S0 -- i n p r e c i p i t a t i o n a l s o c o r r e l a t e d w i t h c l o u d t e m p e r a t u r e but t o a l e s s e r d e g r e e (r=0.35). I t i s i m p o s s i b l e t o draw a d i v i s i o n between s o l i d - p h a s e and l i q u i d - p h a s e hydrometeors based on t h e c l o u d t e m p e r a t u r e because o f s u p e r c o o l i n g and because c l o u d drops most l i k e l y go t h r o u g h s o l i d and l i q u i d phases as the water c i r c u l a t e s from the low, warmer a l t i tudes t o t h e h i g h , c o o l e r a l t i t u d e s . However, t h i s graph s h o u l d p r o v i d e an i n d i c a t i o n o f t h e s t a t e o f t h e system, w i t h hydrometeors a t the low t e m p e r a t u r e s e x i s t i n g a s i c e c r y s t a l s and hydrometeors a t t h e h i g h e r t e m p e r a t u r e s e x i s t i n g a s l i q u i d drops and a g r a d a t i o n o f c o n d i t i o n s in-between. T h e r e f o r e , t h i s e v i d e n c e s u g g e s t s t h a t t h e h i g h e r S0 ~- l e v e l s i n r a i n than i n snow i s due t o t h e g r e a t e r d i s s o l u t i o n and r e a c t i o n o f S 0 i n l i q u i d d r o p s than i c e c r y s t a l s . C o n v e r s e l y , t h e f a c t t h a t N 0 - c o n c e n t r a t i o n s a r e t h e same i n r a i n and snow i n d i c a t e s t h a t t h e d i s s o l u t i o n o f NOx i n t o d r o p s f o l l o w e d by o x i d a t i o n i s a l e s s i m p o r t a n t p r o c e s s t h a n f o r S 0 . 4

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Discussion Four y e a r s o f w i n t e r p r e c i p i t a t i o n e v e n t s were a n a l y z e d i n terms o f S0 ~- and N 0 - c o n c e n t r a t i o n s t o p r o v i d e i n f o r m a t i o n on the mechanisms by w h i c h t h e s e i o n s a r e i n c o r p o r a t e d i n t o p r e c i p i t a t i o n . N 0 was h i g h e r i n snow than i n w i n t e r r a i n , a s suggested by o t h e r s t u d ies. However, i n t h i s s t u d y the d i f f e r e n c e c o u l d be a t t r i b u t e d t o t h e lower p r e c i p i t a t i o n d e p t h s a s s o c i a t e d w i t h snows than w i t h w i n ter rains. There was no e v i d e n c e t h a t snow scavenged HN0 more e f f i c i e n t l y than r a i n a t t h i s l o c a t i o n . C o n v e r s e l y , S0 -- was f a r h i g h e r i n w i n t e r r a i n s t h a n i n snow. T h i s c o u l d not be e x p l a i n e d i n terms o f t h e ambient l e v e l s o f s u l f u r s p e c i e s o r t h e scavenging o f S0 -- p a r t i c l e s . However, the c l o u d temperatures were h i g h enough i n the c a s e o f r a i n t o suggest t h a t the c l o u d hydrometeors c o u l d have been p r e s e n t as l i q u i d d r o p l e t s r a t h e r than i c e c r y s t a l s . The S0 ~- c o n c e n t r a t i o n s o f the p r e c i p i t a t i o n were c o r r e l a t e d w i t h w i n t e r c l o u d l a y e r t e m p e r a t u r e s . The d a t a suggests t h a t S 0 i s i n c o r p o r a t e d and o x i d i z e d t o S0 -- i n c l o u d s when t h e hydrometeors a r e p r e s e n t as l i q u i d d r o p l e t s . The f a c t t h a t N 0 - l e v e l s a r e t h e same i n b o t h r a i n and snow suggests t h a t i n c o r p o r a t i o n o f n i t r o g e n s p e c i e s i n t o c l o u d water f o l l o w e d by o x i d a t i o n i s l e s s important a process f o r n i t r o g e n than f o r s u l f u r . 4

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American Chemical Society Library 1155Rain; 15th St., N.W. In The Chemistry of Acid Johnson, R., el al.; Washington, D.C. Washington, 20036 ACS Symposium Series; American Chemical Society: DC, 1987.

THE CHEMISTRY OF ACID RAIN

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3.6 "

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Ο

Cloud Temperature (°C)

F i g u r e 1. The i n f l u e n c e of c l o u d t e r m p e r a t u r e on the S O 4 — / N O 3 - r a t i o of w i n t e r p r e c i p i t a t i o n . (Reprinted p e r m i s s i o n from r e f . 14. C o p y r i g h t 1987 Pergamon.)

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

with

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Deposition

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Acknowledgment s I thank Ken Kennedy f o r c o l l e c t i n g samples, Frank L i p a r i , W i l l i a m S c r u g g s , Pat Mulawa, and Rene Vandervennet f o r sample a n a l y s i s and George W o l f f and Sudarshan Kumar f o r h e l p f u l d i s c u s s i o n s .

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch021

Literature Cited 1. Bowersox, V.C.; Stensland, G.J.,"Seasonal Patterns of Sulfate and Nitrate in Precipitation in the United States," 74th Air Pollution Control Meeting, Paper 81-6.1, June 1981. 2. Summers, P.W.; Barrie, L.A., "The Spatial and Temporal Varia­ tion of Sulphate to Nitrate Ratio in Precipitation in eastern North America," presented at Muskoka Conference, September, 1985. 3. Dasch, J.M.; Cadle, S.H. Atmos. Environ. 1985, 19, 789. 4. Topol, L.E. Atmos. Environ., 1986, 20, 347. 5. Raynor, G.S.; Hayes, J.V., In Precipitation Scavenging, Dry Deposition, and Resuspension, Pruppacher, H.R., Semonin, R.G., Slinn, W.G.N., Eds., Elsevier Press, 1983, p 249. 6. Chang, T.Y. Atmos. Environ. 1984, 18, 191. 7. Lipari, F. Anal. Chem. 1984, 56, 1820. 8. Barrie, L.A. J. Geophys. Res. 1985, 90, 5789. 9. Knutson, E.O.; Sood, S.K.; Stockham, J.D. Atmos. Environ. 1976, 10, 395. 10. Chan, W.H.; Chung, D.H.S. Atmos. Environ. 1986, 20, 1397. 11. Iribarne, J.V.; Barrie, L.A.; Iribarne, Α., Atmos. Environ. 1983, 17, 1047. 12. Scott, B.C. J. Applied Met. 1981, 20, 619. 13. Pruppacher, H.R., In Chemistry of the Lower Atmosphere, Rasool, Ed., Plenum Press, NY, 1973, pp 1-67. 14. Dasch, J. M. Atmos. Environ. 1987, 21, 141. RECEIVED

March 25, 1987

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Chapter 22

Pollutant Deposition in Radiation Fog 1

2

Jed M. Waldman , Daniel J. Jacob , J. William Munger, and Michael R. Hoffmann

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch022

Department of Environmental Engineering Science, California Institute of Technology (138-78), Pasadena, CA 91125

A. study of atmospheric pollutant behavior was conducted in the southern San Joaquin Valley of California during periods of stagnation, both with and without dense fog. Measurements were made of gas-phase and aerosol pollutant concentrations, fogwater composition, and deposition of solutes to surrogate surfaces. Deposition rates for major species were 5 to 20 times greater during fogs compared to nonfoggy periods. Sulfate-ion deposition velocities measured during fog were 0.5 to 2 cm s . Rates measured for nitrate ion were generally 50% below those for sulfate, except for acidic fog (pH3 d) for valley air. -1

D e p o s i t i o n d u r i n g fog e p i s o d e s can make a s i g n i f i c a n t c o n t r i b u t i o n to the o v e r a l l f l u x o f p o l l u t a n t s i n c e r t a i n e c o s y s t e m s . Further­ more, when a t m o s p h e r i c s t a g n a t i o n p r e v e n t s normal v e n t i l a t i o n i n a r e g i o n , f o g d e p o s i t i o n may become t h e m a i n r o u t e o f p o l l u t a n t removal. Fogs c a n c o n s e q u e n t l y e x e r t dominant c o n t r o l over p o l l u t a n t l e v e l s i n c e r t a i n environments. The s o u t h e r n San J o a q u i n V a l l e y ( S J V ) o f C a l i f o r n i a i s a

'Current address: Department of Environmental & Community Medicine, UMDNJ-Robert Wood Johnson Medical School, Piscataway, NJ 08854 Current address: Center for Earth & Planetary Physics, Harvard University, Cambridge, MA 02138

2

0097-6156/87/0349~0250$06.00/0 © 1987 American Chemical Society

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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Deposition

in Radiation

251

Fog

r e g i o n prone t o w i n t e r t i m e e p i s o d e s o f atmospheric s t a g n a t i o n . These l e a d t o e l e v a t e d p o l l u t a n t c o n c e n t r a t i o n s and/or dense, widespread f o g s . Major o i l - r e c o v e r y o p e r a t i o n s p l u s widespread a g r i c u l t u r a l and l i v e s t o c k f e e d i n g activités a r e i m p o r t a n t sources o f S 0 , Ν€χ, and NH . i n t h e v a l l e y . A m u l t i - f a c e t e d program o f f i e l d m o n i t o r i n g was conducted i n t h e SJV d u r i n g t h e w i n t e r 1984-85, f o c u s i n g on a s p e c t s o f p o l l u t a n t scavenging and removal i n t h e f o g ladden atmosphere. C o n c e n t r a t i o n s o f major s p e c i e s were measured i n gas, d r y a e r o s o l , and fogwater phases. In a d d i t i o n , d e p o s i t i o n a l f l u x e s were m o n i t o r e d by s u r r o g a t e - s u r f a c e methods. These measure­ ments were employed t o d i r e c t l y assess t h e magnitude o f enhanced removal r a t e s caused by f o g . 2

3

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METHODS F i e l d m o n i t o r i n g was conducted a t two SJV s i t e s , B a k e r s f i e l d A i r p o r t and B u t t o n w i l l o w . Fogwater was sampled by event u s i n g r o t a t i n g - a r m c o l l e c t o r s (RAC) w i t h sampling i n t e r v a l s o f 1 t o 2 h . L i q u i d water c o n t e n t (LWC) v a l u e s were a v e r a g e d o v e r t h e f o g w a t e r s a m p l i n g i n t e r v a l s , c a l c u l a t e d from t h e r a t e o f RAC c o l l e c t i o n . Atmospheric c o n c e n t r a t i o n s o f a e r o s o l , n i t r i c a c i d and ammonia were monitored u s i n g d u a l - f i l t e r methods. T o t a l a e r o s o l samples were c o l l e c t e d on open-faced T e f l o n f i l t e r s operated s i d e - b y - s i d e . N y l o n f i l t e r s and g l a s s - f i b e r f i l t e r s impregnated w i t h o x a l i c a c i d c o l l e c t e d HN0 (g) and N H ( g ) , r e s p e c t i v e l y . Samplers were r u n t w i c e d a i l y (0000 t o 0400 and 1200 t o 1600 P S T ) , except d u r i n g f o g e p i s o d e s , when they were r u n c o n t i n u o u s l y f o r 2 t o 4-h i n t e r v a l s . Further d e t a i l s of sampling methods and s i t e s a r e g i v e n elsewhere ( 1 , 2 ) . 3

3

2

P o l y s t y r e n e p e t r i d i s h e s (154 cm ) w i t h t h e i r l i p (1.2 cm) upwards were deployed t o c o n t i n u o u s l y m o n i t o r f o g and d r y p a r t i c l e deposition. These were changed t w i c e p e r day (0800 and 1600 PST) d u r i n g nonfoggy p e r i o d s o r , more f r e q u e n t l y d u r i n g f o g , c o n c u r r e n t to f i l t e r sampling i n t e r v a l s . P e t r i d i s h e s (PD) were e x t r a c t e d w i t h 10 mL o f d i s t i l l e d , d e - i o n i z e d water immediately f o l l o w i n g t h e end of ambient e x p o s u r e . Subsequent e x t r a c t i o n s i n d i c a t e d t h a t complete r e c o v e r y (i.e.,>90%) was a c h i e v e d . S i d e - b y - s i d e sample comparisons were i n good agreement· The use o f s u r r o g a t e s u r f a c e s t o measure d e p o s i t i o n r a t e s remains c o n t r o v e r s i a l due t o t h e u n c e r t a i n t y i n e x t r a p o l a t i n g these r e s u l t s t o n a t u r a l surfaces, e s p e c i a l l y regarding deposition of gases o r submicron a e r o s o l ( 3 ) . The c o n d i t i o n s i n t h e SJV d u r i n g the f o g / a e r o s o l study a l l o w e d us t o a p p l y s i m p l i f y i n g assumptions regarding t h e dominant d e p o s i t i o n p r o c e s s e s . The v a l l e y i s u n i f o r m l y f l a t , and over 85% o f t h e s u r f a c e cover i s open c r o p l a n d or rangeland. There i s m i n i m a l canopy s t r u c t u r e , e s p e c i a l l y d u r i n g wintertime. On a r e g i o n a l s c a l e , t h e t e r r a i n i s r e l a t i v e l y sparse and r a t h e r i n e f f i c i e n t f o r i m p a c t i o n . Furthermore, winds i n the_SJV u n d e r s t a g n a n t c o n d i t i o n s a r e u s u a l l y q u i t e l i g h t (

3

H

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m g

π

to ON ON

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DOKIYA ET AL.

Deposition

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267

The shadowed area in F i g . 5 shows the amount of sulfate which come from sea s a l t . As seen from the f i g u r e , the contribution of sea s a l t was high at the stations on the Japan Sea side and at Wakkanai in winter time. On the other hand, more than 90% of sulfate did not originate from sea s a l t at the stations on the P a c i f i c side of Honshu Is. and at Sapporo. This indicates that anthropogenic sulfate might be one of the larger sources of sulfate in these s t a t i o n s . Unexpectedly low contribution of sea s a l t sulfate at Ishigaki needs some correction because the bed rocks of the Ryukyu Islands are r i c h in calcium carbonate or coral o r i g i n which might cause the d i f f e r e n t d i s t r i b u t i o n of a l k a l i and a l k a l i n e earth metals in the s o i l material.

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch023

2.

Monthly deposition of soluble chemical components and the p r e c i p i t a t i o n at eleven stations in Japan in 1985

Table 2 and Figs. 2b, 3b, 4b and 5b show the r e s u l t s f o r 1985. The amount of p r e c i p i t a t i o n in 1985 was normal a l l over Japan except for somewhat higher values at Ishigaki and Fukuoka. Though the amount of p r e c i p i t a t i o n was d i f f e r e n t from that of 1984, the depositions of chemical components were similar to those in 1984 as seen in the f i g u r e . As seen in F i g . 5 at the s i t e on the P a c i f i c side was mainly that of sulfate (excess), while at the s i t e s on the Japan Sea side, the amount of sea s a l t originated sulfate cannot be neglected in winter months when snow i s heavy. The general trends were s i m i l a r to those of 1984, except f o r some months at Ishigaki. At Ishigaki, more typhoons occurred in 1985 than in 1984, and these might be the cause of the higher contribution of sea s a l t sulfate in August and in September. 3.

S t a t i s t i c a l analyses data

A p r i n c i p a l component analysis was applied to the data of the chemical components and the amount of p r e c i p i t a t i o n at eleven sampling stations to know the c h a r a c t e r i s t i c s of s t a t i o n s . The eigen vectors for the f i r s t and second components are summarized in Tables 3 and 4. The f i r s t components were characterized by sodium, magnesium, strontium, c h l o r i d e , and sulfate ions which means that the major chemical depositions are s i m i l a r throughout Japan, even though the seasonal v a r i a t i o n d i f f e r e d for the stations on the Japan Sea side and the P a c i f i c side. The second components were characterized by calcium and/or n i t r a t e ions. At the big c i t i e s such as Tokyo, Osaka and Fukuoka, n i t r a t e showed the major contribution in the second components. At Wakkanai, Sapporo, Sendai, Wajima and Yonago, Ca showed the major contribution in the second components. Thus, the second components might show the local c h a r a c t e r i s t i c s . Nitrate ion was supposed to originate from transportation sources. The o r i g i n of Ca, however, f o r these stations might not be i d e n t i c a l , including the high dust caused by automobiles in the spring, dust caused by a g r i c u l t u r a l a c t i v i t i e s , etc.

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

THE CHEMISTRY OF ACID RAIN

268

Table 3 Results of principal component analysis (1984) Station

Contribution

Eigen Vector

Wakkanai

I

0.671

0.43Mg + 0.42C1 + 0.41K + 0.40Na + 0.39Sr

II

0.213

0.70NO + 0.66Ca + 0.24Sr

I

0.568

0.46Na + 0.46Mg + 0.45C1 + 0.44K + 0.34NO

+ 0.369O

Sapporo

3

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch023

+ 0.21SO

Akita

4

3

4

II

0.271

0.67Ca + 0.58Sr + 0.40SO

I

0.591

0.42Na + 0.41 CI + 0.40Sr + 0.39Mg + 0.39SO + 0.32NO 0.80K + 0.22Na - 0.51N0

4

4

3

Sendai

Wajima

II

0.170

I

0.417

II

0.283

I

0.831

3

0.53Na + 0.43SO + 0.41Mg + 0.40NO + 0.39C1 0.60Sr + 0.55Ca + 0.27SO - 0.47K 4

3

4

0.38Na + 0.38Mg + 0.38SO + 0.37Sr + 0.36C1 + 0.34NO + 0.33K + 0.26Ca 4

3

Tsukuba

Tokyo

Yonago

II

0.106

0.77Ca + O.2INO3 - 0.51K

I

0.378

II

0.221

0.47Mg + 0.42SO + 0.41NO +0.40C1 + 0.39Na + 0.28Ca 0.48Ca + 0.40SO + 0.39NO + 0.35Sr - 0.39C1 - 0.33Na

I

0.792

II

0.118

I

0.758

II

0.130

I

0.454

II

0.217

I

0.496

II

0.183

0.48Sr + 0.43C1 + 0.40Ca + 0.39Mg + 0.36SO + 0.30Na O.7ONO3 + 0.48SO - 0.40Na

I

0.353

0.54Ca + 0.47Sr + 0.40Mg +0.20C1 - 0.33K

4

3

4

3

0.39M? + 0.39Sr + 0.39C1 + 0.39SO + 0.38K + 0.37Na +0.30Ca 0.97NO 4

3

0.40SO + 0.39Mg + 0.39C1 + 0.36Sr + 0.35Na + 0.34K + 0.34NO + 0.24Ca 0.78Ca + 0.44Sr 4

3

Osaka

0.49SO + 0.45Mg + 0.43Sr + 0.40C1 + 0.40Ca + 0.22NO 0.57NO + 0.38C1 + 0.29C1 + 0.20SO - 0.40Ca - 0.36Sr - 0.31a 4

3

Fukuoka

Ishigaki

3

4

4

4

- O.3ONO3

II

0.307

0.62SO + 0.47C1 + 0.45Na + 0.37K 4

I:first component, II:second component

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

23.

DOKIYA ET AL.

Deposition

of Chemical

Components

269

in Japan

Table 4 Results of principal component analysis(1985) Station

Contribution

Wakkanai

I

0.615

II

0.245

I

0.596

Sapporo

Eigen Vector 0.44Mg + 0.42Na + 0.42SO + 0.40K + 0.39C1 + 0.30Sr 0.64Ca + 0.50Sr + 0.42NO 4

3

0.44Na + 0.44Mg + 0.44C1 + 0.43K + 0.37SO + 0.27NO 0.70Ca + 0.67Sr

4

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch023

3

Akita

II

0.252

I

0.697

0.41Mg + 0.41Sr + 0.41C1 + 0.40Na + 0.36SO + 0.33K + 0.23NO + 0.22Ca 0.63NO + 0.53Ca + 0.25SO

4

3

Sendai

Wajima

II

0.159

I

0.593

II

0.216

I

0.785

II

0.179

I

0.486

II

0.260

I

0.837

3

4

0.44Mg + 0.44SO + 0.43Na + 0.43C1 + 0.35Sr + 0.29K 0.68Ca + 0.44Sr - 0.44K - 0.38NO 4

3

0.39Na + 0.39K + 0.39Mg + 0.39Sr +0.39C1 + 0.34SO + 0.31NO 0.74Ca + 0.43SO - 0.40NO 4

Tsukuba

Tokyo

3

4

3

0.45Ca + 0.45Mg + 0.41SO +0.40C1 + 0.32Na +0.32K + 0.20Sr 0.66NO + 0.33C1 + 0.32SO - 0.48Na 4

3

4

0.37Na + 0.37Sr + 0.37C1 + 0.36K + 0.36SO + 0.32Ca + 0.31NO 0.68NO +0.43NO + 0.20C1 - 0.32Mg

4

3

Yonago

II

0.085

I

0.635

3

3

0.43Mg + 0.41C1 + 0.39SO + 0.38Na + 0.38Ca + 0.34Sr + 0.28NO 0.73K + 0.35Na - 0.37NO 4

3

Osaka

II

0.196

I

0.540

II

0.189

I

0.647

II

0.191

I

0.818

II

0.128

3

0.4lMg + 0.41C1 + 0.38Na + 0.36K + 0.34Ca + 0.33Sr + 0.33SO 0.59NO + 0.48SO + 0.27C1 - 0.4lNa 4

Fukuoka

Ishigaki

3

4

0.43Mg + 0.42Sr + 0.41C1 + 0.39Na + 0.38SO + 0.37Ca + 0.22K 0.77NO + 0.37SO + 0.27Ca - 0.33Na

4

3

4

0.39K + 0.39Mg + 0.39Sr + 0.39SO + 0.38C1 + 0.35Na + 0.35Ca 0.95NO + 0.23Ca 4

3

I r f i r s t component, II:second component

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

THE CHEMISTRY OF ACID RAIN

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch023

270

Fig. 6

Soil map for assessing the susceptibility to acid rain and the annual S0 (excess) of 11 stations for 1984 and 1985 4

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

23.

DOKIYA ET AL.

Deposition

of Chemical

Components

in Japan

271

For the unusual behavior of potassium ion concentration at Akita in 1984 and Yonago in 1985, shown in the second components, more continuous investigation may be needed to check i t s reproducibility. 4.

The effect of sulfate deposition on the chemistry of s o i l

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch023

The Japanese Society of Soil Science and Plant Nutrition provided the s o i l map f o r assessing the s u s c e p t i b i l i t y of Japanese s o i l s to acid p r e c i p i t a t i o n (7). F i g . 6 shows a summary of the map together with the annual deposition of sulfate (excess) at eleven stations in Japan. The most susceptible and most tolerant areas are distinguished on the map. The s o i l s in unmarked regions of the map have intermediate s u s c e p t a b i l i t y . From the f i g u r e , i t i s seen that the northeastern part of Honshu Is. is r e l a t i v e l y tolerant to acid deposition having r e l a t i v e l y r i c h organic s o i l s even though the chemistry of the s o i l i t s e l f i s f a i r l y a c i d i c owing to i t s volcanic o r i g i n . This can be, therefore, one of the reasons why few typical symptoms of the e f f e c t of acid precipitations have been obvious in t h i s area even though the deposition amount of sulfate was high near the i n d u s t r i a l i z e d area of metropolitan Tokyo. Another point i s that the western part of Honshu Is. i s r e l a t i v e l y susceptible to acid p r e c i p i t a t i o n e s p e c i a l l y on the Japan sea side, thus t h i s should be watched c a r e f u l l y because t h i s area is at down wind of the Continental dust. The source of sulfate can be roughly shown as follows: S 0 " (dep) = S 0 " (sea s a l t ) + S 0 " ( l o c a l ) 4

2

4

2

4

+ S0 " 4

2

2

(transported)

The t h i r d member of the equation should be studied further in r e l a t i o n to the meteorological conditions and other factors which are involved in the long-range transport of gaseous materials. The e f f e c t of acid deposition on s o i l and eventually on land, water and the biosphere should also be studied further. The continuous observation of chemical deposition is needed with more suitable sampling s i t e s and for more chemical components f o r these purposes. References

1. K. Sekiguchi, Y. Hara and A. Ujiiye, Environ. Tech. Lett. Vol 7,263, 1986. 2. T. Okita and Y. Ota, Shissei-taikiosen (Wet Air Pollution), Sangyotosho (Tokyo), p203-231, 1983. 3. E. Yoshimura, A. Hamada and S. Toda, Proc. Annual Meeting, Japan Soc. Anal. Chem., 1984.

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

272

THE CHEMISTRY OF ACID RAIN

4. Y. Dokiya, E. Yoshimura and S. Toda, Proceedings of Pittsburg Conference and Exposition, p528, 1986 5. Y. Dokiya and S. Bessho, Anal. Sci., Vol 2,187, 1986. 6. EML-381, Dept. of Energy (environmental quality), 1980. 7. A. Wada et al, Map for assessing susceptibility of Japanese soils to acid precipitation, Japanese Society of Soil Sci. and Plant Nutrition, 1983.

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch023

RECEIVED May 15, 1987

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Chapter 24

Measurement of Atmospheric Gases by Laser Absorption Spectrometry H. I. Schiff, G. W. Harris, and G. I. Mackay

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch024

Unisearch Associates, 222 Snidercroft, Concord, Ontario L4K 1B5 Canada

The advantages of Tunable Diode Laser Absorption Spectrometry (TDLAS) for measuring trace atmospheric gases are universality, positive identification, good sensitivity and rapid response time. An instrument is described which can measure two gases simultaneously under automatic computer control with detection limits better than 100 parts per trillion and with response times better than 5 minutes. Procedures have been established for the measurement of NO, NO , MNO, NH , H Q and HCHO. These species have been measured under a variety of conditions in smog chambers and in ambient air from mobile laboratories and from aircraft. 2

2

3

3

2

Tunable d i o d e l a s e r a b s o r p t i o n s p e c t r o m e t r y o f f e r s an a t t r a c t i v e method f o r a t m o s p h e r i c measurements atmospheric i n t e r e s t

( 1 ) . Almost a l l gases o f

a b s o r b s i n the 2 t o 1 5 m i c r o n r e g i o n . The v e r y

high s p e c t r a l r e s o l u t i o n of tunable diode l a s e r s permit s e l e c t i o n o f a s i n g l e r o t a t i o n a l - v i b r a t i o n a l l i n e which makes from o t h e r g a s e s v e r y u n l i k e l y .

I f an a c c i d e n t a l

interferences

interference

s h o u l d happen to o c c u r i t can r e a d i l y be i d e n t i f i e d by a change i n l i n e shape and another

l i n e c a n be c h o s e n .

Unequivocal proof of

the absence o f i n t e r f e r e n c e i s o b t a i n e d by measuring the c o n c e n t r a t i o n s at 2 d i f f e r e n t i n t e r f e r e n c e s at 2 d i f f e r e n t

l i n e s . The p r o b a b i l i t y o f

identical

l i n e s i s vanishingly small ( 2 ) .

0097-6156/87/0349-0274$06.00/0 © 1987 American Chemical Society

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

24.

SCHIFF ET

AL.

Measurement

of Atmospheric

275

Gases

To get the d e s i r e d s e n s i t i v i t y and d e t e c t i o n l i m i t a l o n g a b s o r p t i o n p a t h can be o b t a i n e d by u s i n g a m u l t i - p a s s White The a b s o r p t i o n l i n e can be scanned

cell.

i n a f r a c t i o n o f a second

and

the response time o f t h e measurement i s n o r m a l l y l i m i t e d by t h e r e s i d e n c e time o f the sampled gas i n the White c e l l which i s t y p i c a l l y a few

Description

seconds.

of the Instrument

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch024

F i g u r e 1 shows t h e s c h e m a t i c o f a TDLAS system d e s i g n e d t o o p e r a t e i n f i e l d c o n d i t i o n s from a m o b i l e l a b o r a t o r y . Lead s a l t d i o d e s t y p i c a l l y o p e r a t e i n t h e 20 t o 80 Κ range and t h e wavelength r e g i o n over which they emit r a d i a t i o n depends on t h e temperature and c u r r e n t p a s s i n g through them.

the

Temperature c o n t r o l to + .005 Κ i s

p r o v i d e d by t h e c o m b i n a t i o n o f a c l o s e d c y c l e h e l i u m c r y o c o o l e r , a h e a t e r and a s e r v o temperature system. each One

Two

c r y o s t a t s a r e used*

h a v i n g a l a s e r s o u r c e assembly c o n t a i n i n g 4 l a s e r d i o d e s . l a s e r d i o d e from each assembly can be chosen t o p e r m i t

two

gases t o be measured s i m u l t a n e o u s l y . The e m i t t e d r a d i a t i o n from each o f the d i o d e s i s scanned over the s e l e c t e d a b s o r p t i o n f e a t u r e by changing t h e c u r r e n t through the d i o d e . The l a s e r beam from each head i s c o l l e c t e d and f o c u s s e d by an o f f - a x i s p a r a b o l i c m i r r o r , QAP

S

or 0AP

a

and t h e n d i r e c t e d t o a

s e l e c t i o n m i r r o r , S which f l i p s back and f o r t h t o p e r m i t the beam from each o f the d i o d e s t o e n t e r the White c e l l

i n turn.

The 45° a n g l e o f the e n t r a n c e window t o t h e White c e l l t h e l a s e r beam.

splits

Most o f t h e beam p a s s e s through the window i n t o

the White c e l l but about 5% i s r e f l e c t e d through a c e l l

containing

h i g h c o n c e n t r a t i o n s o f t h e t a r g e t gases onto a s e p a r a t e HgCdTe detector.

The o u t p u t from t h i s d e t e c t o r i s used t o l o c k the l a s e r

r a d i a t i o n wavelength t o t h e c e n t e r o f t h e a b s o r p t i o n l i n e . The beam e n t e r s the 1.75 m T e f l o n - l i n e d White c e l l a c o r n e r cube r e f l e c t o r to t h e d e t e c t o r .

containing

5

Ο τι

55 H

§

η s m

ο ο

25.

TANNER

Instrumentation

of Atmospheric

Wet Deposition

Processes

301

Acknowledgments The a u t h o r acknowledges many i n f o r m a t i v e d i s c u s s i o n s w i t h T.J. K e l l y and P.H. Daum. T h i s work was conducted under the a u s p i c e s o f the U.S. Department o f energy under c o n t r a c t No. DE-ÀC02-76CH00016.

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch025

References 1. Tanner, R.L.; Daum, P.H.; Kelly, T.J. Intern. J. Environ. Anal. Chem., 1983, 13, 323-335. 2. Walters, P.T.; Moore, M.J.; Webb, A.H. Atmos. Environ., 1983, 17, 1083-1091. 3. Daum, P.H.; Kelly, T.J.; Schwartz, S.E.; Newman, L. Atmos. Environ., 1984, 18, 2671-2684. 4. Winters, W.; Hogan, Α.; Mohnen, V.; Barnard, S. "ASRC airborne cloud water collection system", Atmospheric Sciences Research Center, State University of New York at Albany, ASRC-SUNYA Publication No. 728, 1979. 5. Huebert, B.J.; Baumgardner, D. Atmos. Environ., 1985, 19, 843-846. 6. Scott, B.C.; Laulainen, N.S. J. Appl. Meteor., 1979, 18, 138-147. 7. Fontijn, Α.; Sabadell, A . J . ; Ronco, R.J. Anal. Chem., 1970, 42, 575-579. 8. Stedman, D.H.; Daby, E.E.; Stuhl, F.; Niki, H. J. Air Poll. Contr. Assoc., 1972, 22, 260-263 (1972). 9. Delany, A.C.; Dickerson, R.R.; Melchoir, F.L., Jr.; Wartburg, A.F. Rev. Sci. Instrum., 1983, 53, 1899-1903. 10. Kelly, T.J. "Modifications of Commercial Oxides of Nitrogen Detectors for Improved Response", Brookhaven National Laboratory, Upton, NY, Report No. BNL-38000, 1986. 11. Tanner, R.L.; Lee, Y.-N.; Kelly, T.J.; Gaffney, J.S. "Ambient HNO3 Measurements-Interference from PAN and Organo-Nitrogen Compounds", presented at the 25th Rocky Mountain Conference, Denver, CO, 1983. 12. D'Ottavio, T.; Garber, R.; Tanner, R.; Newman, L. Atmos. Environ., 1981, 15, 197-203. 13. Garber, R.W.; Daum, P.H.; Doering, R.F.; D'Ottavio, T.; Tanner, R.L. Atmos. Environ., 1983, 17, 1381-1385." 14. Lind, J . ; Kok, G.L. J. Geophys. Res., 1986, 91, 7889-7895. 15. Spicer, C.W.; Holdren, M.W.; Keigley, G.W. Atmos. Environ., 1983, 17, 1055-1058. 16. Singh, H.B.; Salas, L . J . Nature, 1983, 302, 326. 17. Gaffney, J.S.; Fajer, R.; Senum, G.I. Atmos. Environ., 1984, 18, 18215-18218. 18. Lazrus, A.L.; Kok, G.L.; Gitlin, S.N.; Lind, J.A.; McLaren, S.E. Anal. Chem., 1985, 57, 917-920. 19. Kelly, T.J.; Daum, P.H.; Schwartz, S.E. J. Geophys. Res., 1985, 90, 7861-7871. 20. Heikes, B.G. Atmos. Environ., 1984, 18, 1433-1445. 21. Schiff, H.I.; Mackay, G.I. "The Development of a Method for Measuring H2O2 in Real Air Using a Tunable diode Laser Absorption Spectrometer", Final Report of Research Project RP 2023-5, prepared by Unisearch Associates, Inc., for the Electric Power Research Institute, 1984.

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch025

302

THE CHEMISTRY OF ACID RAIN

22. Lazrus, A.L.; Kok, G.L.; Lind, J.A.; Gitlin, S.N.; Heikes, B.G.; Shetter, R.E. Anal. Chem., 1986, 58, 594-597. 23. Tanner, R.L.; Markovits, G.Y.; Ferreri, E.M.; Kelly, T.J. Anal. Chem., 1986, 58, 1857-1866. 24. Groblicki, P.J.; Ang, C.C. "Measurement of H2O2 without Ozone Interference", Proceedings of the Symposium on Heterogeneous Processes in Source-Dominated Atmospheres, New York, 1985, 86-88. 25. Heikes, B.G.; Lazrus, A.L.; Kok, G.L. "Measurements of H2O2 in the Lower Troposphere", presented at the 17th International Symposium on Free Radicals, Granby, CO, 1985. 26. Kok, G.L.; Thompson, K.; Lazrus, A.L.; McLaren, S.E. Anal. Chem., 1986, 58, 1192-1194. 27. Kelly, T.J.; Gaffney, J.S.; Phillips, M.F.; Tanner, R.L. Anal. Chem., 1983, 55, 135-138. 28. Grosjean, D.; Fung, K. Anal. Chem., 1982, 54, 1221-1224. 29. Tanner, R.L.; Meng, Z. Environ. Sci. Technol., 1984, 18, 723-726. 30. Keene, W.C.; Galloway, J.N.; Holden, J.D. J. Geophys. Res., 1983, 88, 5122-5130. 31. Kallend, A.S. "The Fate of Atmospheric Emissions along Plume Trajectories over the North Sea: First Annual Report to EPRI, March, 1979", Central Electric Research Laboratories, Leatherhead, Surrey, England, Report No. RO/L/R 1998, 1979. RECEIVED March 10, 1987

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Chapter 26

Factors Affecting N O Production During Char Oxidation x

Gregory J. Orehowsky, Alan W. Scaroni, and Francis J. Derbyshire

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch026

FuelScience Program, Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802

The oxidation of chars prepared from nitrogen­ -containing precursors has been investigated. Chars produced from the nitrogen-containing compounds acridine and phenanthridine were oxidized at atmospheric pres­ sure at temperatures of 773-873 K. The relative rates of nitrogen and carbon release and the formation of NOx have been determined in relation to char nitrogen con­ tent and precursor type. At 773 Κ carbon was found to be preferentially oxi­ dized at low burnoff; at higher temperatures the rates of carbon and nitrogen oxidation were indistinguishable. The conversion of char nitrogen to NO was dependent upon the char structure and composition, much less NOx being produced from the phenanthridine char. It is assumed that the remainder of the nitrogen is released as N2, presumably formed by the reduction of NO with C and/or CO. The conversion of nitrogen to NO was also found to decrease with increasing oxidation tempera­ ture, char nitrogen content and with sample bed height. x

X

x

A l t h o u g h S 0 e m i s s i o n s a r e most o f t e n i d e n t i f i e d as the p r i n c i p a l p r e c u r s o r s to a c i d r a i n , N 0 e m i s s i o n s a l s o p l a y an i m p o r t a n t r o l e i n a c i d r a i n formation ( 1 ) . B e f o r e methods f o r l i m i t i n g N 0 e m i s s i o n s from s o l i d f u e l combustors can be f u l l y d e v e l o p e d , a more d e t a i l e d u n d e r s t a n d i n g o f the r e a c t i o n c h e m i s t r y o f f u e l bound n t i r o g e n o x i d a ­ t i o n must be o b t a i n e d . D u r i n g c o m b u s t i o n , N 0 i s formed e i t h e r by the r e a c t i o n o f oxy­ gen and a t m o s p h e r i c n i t r o g e n ( t h e r m a l N 0 ) o r the o x i d a t i o n o f chem­ i c a l l y bound n i t r o g e n i n the f u e l ( f u e l N 0 ) . The p r o d u c t i o n o f t h e r m a l N 0 can be m i n i m i z e d by v a r i o u s t e c h n i q u e s which lower the flame t e m p e r a t u r e . The r e d u c t i o n o f t h e r m a l N 0 a l o n e may not lower N 0 e m i s s i o n s to w i t h i n a c c e p t a b l e r e g u l a t o r y l i m i t s . Thus, i t w i l l be n e c e s s a r y to l i m i t f u e l N 0 e m i s s i o n s . There have been a l i m i t e d number o f s t u d i e s which i n d i c a t e t h a t the c o n v e r s i o n o f c h a r n i t r o g e n to N 0 can make a s i g n i f i c a n t c o n t r i ­ b u t i o n to the t o t a l N 0 e m i s s i o n s . The o x i d a t i o n o f c h a r n i t r o g e n X

X

X

X

X

X

X

X

X

X

X

X

0097-6156/87/0349-0304$06.00/0 © 1987 American Chemical Society

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

26.

OREHOWSKY ET AL.

Factors Affecting

NO

x

305

Production

has been found t o account f o r between 20 and 40 p e r c e n t o f t h e t o t a l f u e l N 0 e m i s s i o n s d u r i n g p u l v e r i z e d c o a l combustion (_2). Since f l u i d i z e d bed combustors o p e r a t e a t lower temperatures than p u l v e r i z ­ ed c o a l combustors, more n i t r o g e n i s r e t a i n e d i n t h e c h a r . The c h a r has been shown t o be t h e major c o n t r i b u t o r t o N 0 f o r m a t i o n u n t i l ap­ p r o x i m a t e l y 1200 Κ d u r i n g f l u i d i z e d bed combustion (_3). F u e l n i t r o g e n i s c o n v e r t e d t o N 0 t h r o u g h two pathways; homogen­ eous o x i d a t i o n o f n i t r o g e n - c o n t a i n i n g v o l a t i l e s and heterogeneous ox­ i d a t i o n o f the n i t r o g e n contained i n the char. I t i s the l a t t e r mechanism o f N 0 p r o d u c t i o n t h a t i s t h e s u b j e c t o f t h i s paper. In t h e p r e s e n t work t h e o x i d a t i o n o f n i t r o g e n - c o n t a i n i n g c h a r s p r e p a r e d from model compound p r e c u r s o r s was s t u d i e d . The r e l a t i v e r a t e s o f n i t r o g e n and carbon d e p l e t i o n and t h e mode o f n i t r o g e n r e ­ l e a s e were i n v e s t i g a t e d . The i n f l u e n c e o f t h e c h a r n i t r o g e n c o n t e n t , the p r e c u r s o r c o m p o s i t i o n , and t h e o x i d a t i o n temperature on N 0 p r o ­ d u c t i o n were s t u d i e d . X

X

X

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch026

X

X

Sample P r e p a r a t i o n The n i t r o g e n - c o n t a i n i n g h e t e r o c y c l i c compounds, a c r i d i n e and phenan­ t h r i d i n e , and t h e p o l y c y c l i c a r o m a t i c s , a n t h r a c e n e and phenanthrene, were used as c h a r p r e c u r s o r s . A c r i d i n e has t h e t h r e e - r i n g e d s t r u c ­ t u r e o f a n t h r a c e n e w i t h a n i t r o g e n atom s u b s t i t u t e d f o r a c a r b o n atom i n the 9 p o s i t i o n . S i m i l a r l y , p h e n a n t h r i d i n e i s t h e n i t r o g e n con­ t a i n i n g a n a l o g o f phenanthrene. The n i t r o g e n c o n t e n t s o f b o t h a c r i ­ d i n e and p h e n a n t h r i d i n e a r e 7.8 wt%. The n i t r o g e n c o n t e n t s o f c h a r s p r e p a r e d from these compounds were v a r i e d by b l e n d i n g v a r i o u s amounts o f a c r i d i n e w i t h a n t h r a c e n e and p h e n a n t h r i d i n e w i t h phenanthrene. A l l o f t h e compounds, - 98% p u r i t y , were o b t a i n e d c o m m e r c i a l l y . A l t h o u g h i t i s r e c o g n i z e d t h a t a study o f c o a l c h a r o x i d a t i o n i s v e r y u s e f u l , t h e fundamental u n d e r s t a n d i n g o f the o x i d a t i o n p r o ­ c e s s ( e s ) i s c o m p l i c a t e d by t h e i n d e t e r m i n a t e s t r u c t u r e o f t h e c h a r , by t h e p r e s e n c e o f o t h e r heteroatoms, and by t h e p r e s e n c e o f i n o r g a n ­ i c components, some o f which may p o s s e s s c a t a l y t i c a c t i v i t y . To c i r ­ cumvent these d i f f i c u l t i e s , model compound c h a r p r e c u r s o r s were used i n t h i s r e s e a r c h . The h i g h p u r i t y o f t h e s t a r t i n g m a t e r i a l s ensured t h a t t h e c h a r s were comprised p r i n c i p a l l y o f c a r b o n and n i t r o g e n , w i t h low c o n c e n t r a t i o n s o f hydrogen and a s h . The char p r e c u r s o r s were c a r b o n i z e d a t 823 Κ f o r 90 minutes under a n i t r o g e n p r e s s u r e o f 0.68 MPa i n t u b i n g bomb r e a c t o r s . The carbonaceous r e s i d u e s were s u b s e q u e n t l y heat t r e a t e d a t 1273 Κ f o r 1 hour under argon i n a tube f u r n a c e t o d r i v e o f f r e s i d u a l v o l a t i l e matter. The c a r b o n i z a t i o n was conducted t o i n c r e a s e char y i e l d ; d i ­ r e c t h e a t treatment o f t h e p r e c u r s o r s would r e s u l t i n v e r y low c h a r yeilds. The h i g h heat treatment temperature was chosen t o ensure t h a t a t t h e lower temperature used i n t h e o x i d a t i o n e x p e r i m e n t s , t h e r e would be no v o l a t i l e m a t e r i a l , thus e n s u r i n g t h a t t h e r e a c t i o n was heterogeneous. A i r o x i d a t i o n s o f t h e 1273 Κ c h a r s were performed over t h e temp­ e r a t u r e range o f 773 Κ t o 873 Κ a t a t m o s p h e r i c p r e s s u r e . In these e x p e r i m e n t s , two grams o f c h a r were p l a c e d i n a q u a r t z tube r e a c t o r h e l d v e r t i c a l l y i n a f l u i d i z e d bed sandbath. Preheated a i r , a t a f l o w r a t e o f 1.7 1/m, was passed upward t h r o u g h t h e sample. The c h a r was o x i d i z e d t o t h e d e s i r e d b u r n o f f and t h e r e s i d u a l c h a r was exam­ i n e d t o determine changes i n t h e c o n c e n t r a t i o n o f C, H, and Ν as a

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

306

THE CHEMISTRY OF ACID RAIN

f u n c t i o n o f b u r n o f f . The e f f l u e n t gases were a n a l y z e d by a nondispers i v e i n f r a r e d CO/CO2 a n a l y z e r and a c h e m i l u m i n e s c e n t N 0 a n a l y z e r . The CO/CO2 a n a l y z e r was c a l i b r a t e d u s i n g N as a z e r o gas and a c e r t i ­ f i e d m i x t u r e o f 1.7% C02, 0.7% CO, and b a l a n c e N2 as a span gas. The N 0 a n a l y z e r was c a l i b r a t e d u s i n g a i r as a z e r o gas and a c e r t i f i e d m i x t u r e o f 920 ppra NO and b a l a n c e N2 as a span gas. X

2

X

R e s u l t s and D i s c u s s i o n

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch026

Elemental Analyses o f Chars. E l e m e n t a l a n a l y s e s o f the c h a r s produced a f t e r h e a t t r e a t m e n t a r e p r e s e n t e d i n T a b l e I . The c h a r p r e c u r s o r s had n i t r o g e n c o n t e n t s r a n g i n g from 1.0 t o 7.8 p e r c e n t by weight. The n i t r o g e n c o n t e n t s o f the c o r r e s p o n d i n g c h a r s were lower

Table I.

E l e m e n t a l A n a l y s e s o f 1273 Κ

Chars

C (wt%)

H (wt%)

Ν (wt%)

H/N

13% a c r i d i n e 87% a n t h r a c e n e 38% a c r i d i n e 62% a n t h r a c e n e 64% a c r i d i n e 36% a n t h r a c e n e 100% a c r i d i n e

98.2

0.35

1.16

4.22

96.9

0.37

2.93

1.77

95.9

0.24

4.56

0.74

92.1

0.42

6.66

0.88

13% p h e n a n t h r i d i n e 87% phenanthrene 38% p h e n a n t h r i d i n e 62% phenanthrene 64% p h e n a n t h r i d i n e 36% phenanthrene 100% p h e n a n t h r i d i n e

94.0

0.32

0.98

4.57

93.7

0.55

2.25

3.42

96.4

0.28

3.71

1.06

94.6

0.56

5.25

1.17

Precursor

(mol.)

because o f n i t r o g e n l o s s t o the vapor phase d u r i n g c a r b o n i z a t i o n and heat treatment. I n a d d i t i o n , the p h e n a n t h r i d i n e - p h e n a n t h r e n e chars had lower n i t r o g e n c o n t e n t s than the c o r r e s p o n d i n g a c r i d i n e - a n t h r a cene c h a r s . Carbon and N i t r o g e n R e a c t i v i t i e s i n Pure A c r i d i n e and P h e n a n t h r i d i n e Chars. Chars formed from pure a c r i d i n e and p h e n a n t h r i d i n e were o x i ­ d i z e d t o v a r i o u s l e v e l s o f b u r n o f f and the r e s i d u a l c h a r s were ana­ l y z e d t o d e t e r m i n e t h e changes i n c a r b o n , hydrogen, and n i t r o g e n con­ c e n t r a t i o n (wt%). The a c r i d i n e c h a r was o x i d i z e d a t 773, 798, and 823 Κ and the p h e n a n t h r i d i n e c h a r a t 773 K. Above t h i s t e m p e r a t u r e , due t o i t s h i g h r e a c t i v i t y , the p h e n a n t h r i d i n e c h a r i g n i t e d p r o d u c i n g u n c o n t r o l l e d b u r n o f f . S i n c e the o x i d a t i o n s were performed a t temper­ a t u r e s below the c h a r heat t r e a t m e n t temperature, c a r b o n and n i t r o g e n removal s h o u l d be t h r o u g h o x i d a t i o n o n l y ( i . e . , n o t t h r o u g h d e v o l a t i lization). P l o t s o f the c a r b o n and n i t r o g e n r e t a i n e d i n the c h a r a r e shown as a f u n c t i o n o f weight l o s s i n F i g u r e s 1-4). At 773 K, c a r b o n and n i t r o g e n o x i d a t i o n r a t e s were d i f f e r e n t f o r b o t h the a c r i d i n e and p h e n a n t h r i d i n e c h a r s , F i g u r e s 1 and 2. F o r

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch026

26.

Factors Affecting

OREHOWSKY ET AL.

F i g u r e 1.

NO

Production

x

307

R e t e n t i o n o f A c r i d i n e Char N i t r o g e n as a F u n c t i o n o f B u r n o f f i n A i r a t 773 Κ

ο

•

Nitrogen

•

Carbon

0.4

100

F i g u r e 2.

Retention of Phenanthridine of Burnoff

Char N i t r o g e n as a F u n c t i o n

i n A i r a t 773 Κ

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

THE CHEMISTRY OF ACID RAIN

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch026

308

0

20

40

60

80

100

% Bum-off

F i g u r e 3.

R e t e n t i o n o f A c r i d i n e Char N i t r o g e n as a F u n c t i o n o f Burnoff

i n A i r a t 798 Κ

20

40

60

100

% Burnoff

F i g u r e 4.

R e t e n t i o n o f A c r i d i n e Char N i t r o g e n as a F u n c t i o n o f Burnoff

i n A i r a t 823 Κ

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

26.

Factors Affecting

OREHOWSKY ET AL.

NO

x

309

Production

b o t h c h a r s a t 773 K, carbon was p r e f e r e n t i a l l y o x i d i z e d u n t i l between 30-40% weight l o s s . From t h i s p o i n t , the r a t e o f n i t r o g e n r e l e a s e exceeded t h a t o f carbon and the two c u r v e s i n F i g u r e s 1 and 2 con­ verged. At 798 and 823 Κ ( u n l i k e a t 773 Κ ) , the r a t e s o f carbon and n i t r o g e n o x i d a t i o n appear t o be e q u a l f o r the a c r i d i n e c h a r , F i g u r e s 3 and 4. Char n i t r o g e n enrichment w h i c h o c c u r s a t low b u r n o f f a t 773 K, has been o b s e r v e d d u r i n g the p a r t i a l combustion o f s h a l e p a r t i c l e s (4). The r e s u l t s a t 798 and 823 Κ a r e i n agreement w i t h the r e s u l t s o f Song (_5) f o r the o x i d a t i o n o f a 1750 Κ l i g n i t e char a t 1250 K. It appears t h a t the r a t e s o f o x i d a t i o n o f c h a r c a r b o n and n i t r o g e n a r e e q u a l a t the temperatures o f i n t e r e s t i n p r a c t i c a l combustors. N0 Formation. The mass f r a c t i o n o f c h a r n i t r o g e n e v o l v e d and the p r o p o r t i o n converted to N0 a r e shown as a f u n c t i o n o f c a r b o n l o s s f o r pure a c r i d i n e and p h e n a n t h r i d i n e c h a r s i n F i g u r e s 5 and 6, r e ­ spectively. Carbon l o s s was determined from o n - l i n e m o n i t o r i n g o f CO and C O 2 c o n c e n t r a t i o n s . The c a r b o n l o s s c a l c u l a t e d i n t h i s way was 5% and 7% h i g h e r than t h a t determined by e l e m e n t a l a n a l y s i s o f the r e s i d u a l chars. The p h e n a n t h r i d i n e c h a r had a much lower c o n v e r s i o n of char n i t r o g e n to N0 than d i d the a c r i d i n e c h a r . At 60% c a r b o n l o s s , t h e r e was a 32% c o n v e r s i o n o f c h a r n i t r o g e n to N 0 f o r the a c r i d i n e c h a r , w h i l e f o r the p h e n a n t h r i d i n e c h a r i t was o n l y 14%. A l t h o u g h not d i r e c t l y measured, i t i s assumed t h a t the r e m a i n i n g n i ­ t r o g e n was e v o l v e d as N£. These r e s u l t s i l l u s t r a t e t h a t the c o n v e r ­ s i o n o f char n i t r o g e n t o N 0 i s dependent upon the c h a r p r e c u r s o r , and presumably the way i n which t h i s i n f l u e n c e s the c h e m i c a l and p h y s i c a l s t r u c t u r e o f the c h a r .

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch026

X

X

X

X

X

F i g u r e 7 shows the e x t e n t o f c o n v e r s i o n to N 0 and the t o t a l n i ­ t r o g e n r e l e a s e d from the c h a r as a f u n c t i o n o f weight l o s s f o r the a c r i d i n e c h a r o x i d i z e d a t 823 K. At complete b u r n o f f , 50% o f the char n i t r o g e n was c o n v e r t e d t o N 0 and 50% o f the n i t r o g e n was r e ­ l e a s e d as N£. The r a t i o o f n i t r o g e n r e l e a s e d as N 0 t o the t o t a l n i ­ t r o g e n r e l e a s e d from the c h a r , as shown i n F i g u r e 8, was between 0.45 and 0.50 over the range o f a c r i d i n e c h a r burnoff, from 20 t o 1007o. X

X

X

E f f e c t o f Temperature on C o n v e r s i o n o f Char N i t r o g e n t o N0 . The e f t e c t or o x i d a t i o n temperature upon the p r o p o r t i o n a l r e i e a s e o f N 0 is t a b u l a t e d i n T a b l e I I f o r pure a c r i d i n e and p h e n a n t h r i d i n e c h a r s a t X

X

Table I I . E f f e c t

o f Temperature on C o n v e r s i o n o f Char N i t r o g e n t o A c r i d i n e - (6.66%

Temperature, Κ Ν 0 Conversion, χ

%

Temperature, Κ N0 Conversion, X

%

N) 873 9.2

823 50 Phenanthridine

N0

(5.25%

823 13

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

N) 873 6.1

X

310

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THE CHEMISTRY OF ACID RAIN

Figure 6.

Mass F r a c t i o n o f Ν Released

from P h e n a n t h r i d i n e

Char as a F u n c t i o n o f Carbon C o n v e r s i o n

i n A i r a t 773 Κ

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Factors Affecting

OREHOWSKY ET AL.

α •

0.8

NO

Production

x

y

Total Nitrogen N as NOx

y

Ε ο

•

y

0.4

•

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch026

0.2

/

H

0.0 20

40

80

60

100

% Burn-off

F i g u r e 7.

Mass F r a c t i o n o f N R e l e a s e d Function

of Burnoff

40

from A c r i d i n e Char as a

i n A i r a t 823 K

60

80

% Burn-off

F i g u r e 8.

Ratio o f N Released

as N 0

Function

i n A i r a t 823 K f o r A c r i d i n e Char

of Burnoff

X

to T o t a l N Released

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

as a

312

THE CHEMISTRY OF ACID RAIN

complete b u r n o f f . The c h a r n i t r o g e n t o N 0 c o n v e r s i o n f o r the a c r i ­ d i n e c h a r d e c r e a s e d from 50% t o 9.2% when the f u r n a c e temperature was r a i s e d from 823 Κ t o 873 K. The same c o n v e r s i o n d e c r e a s e d c a . 50% f o r p h e n a n t h r i d i n e char over the same temperature range. Similar re­ s u l t s have been r e p o r t e d by Song (6) f o r the o x i d a t i o n o f a c o a l char at h i g h e r temperatures (1250-1750 K ) . The n i t r o g e n c o n v e r s i o n s r e p o r t e d i n T a b l e I I were measured w i t h the chemiluminescent N 0 a n a l y z e r . D u r i n g the o x i d a t i o n o f the phe­ n a n t h r i d i n e c h a r a t 873 K, no d i f f e r e n c e s were seen i n the i n s t r u m e n t a l l y measured c o n c e n t r a t i o n o f NO and N0 . This indicates that NO and N 2 are the p r i n c i p a l n i t r o g e n s p e c i e s p r e s e n t . Both N H 3 and HCN and can be c o n v e r t e d t o NO by the s t a i n l e s s s t e e l c a t a l y s t i n the a n a l y z e r ( 7 ) . I f e i t h e r o f t h e s e two s p e c i e s were p r e s e n t , the mea­ sured N0 v a l u e would be h i g h e r than the NO v a l u e . The d r a m a t i c d e c r e a s e i n char n i t r o g e n t o N 0 c o n v e r s i o n f o r the a c r i d i n e c h a r cannot be a t t r i b u t e d o n l y t o a 50 Κ i n c r e a s e i n temper­ ature. The c h a r i g n i t e d a t 873 Κ but not a t 823 K. The bed temper­ a t u r e d u r i n g o x i d a t i o n a t 873 Κ was p r o b a b l y c o n s i d e r a b l y h i g h e r than 873 K. The bed temperature d u r i n g o x i d a t i o n o f the p h e n a n t h r i d i n e c h a r a t the f u r n a c e temperature o f 873 Κ i s shown i n F i g u r e 9. A maximum temperature o f 1006 Κ was r e a c h e d w i t h i n 3 minutes and the bed temperature remained 50 Κ h i g h e r than the f u r n a c e temperature even a f t e r 30 m i n u t e s . X

X

X

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch026

X

X

E f f e c t o f Char N i t r o g e n Content on C o n v e r s i o n t o N0 . The e f f e c t o f the c h a r n i t r o g e n c o n t e n t on c o n v e r s i o n t o Ν ϋ i s shown i n F i g u r e 10. The c o n v e r s i o n d e c r e a s e d s l i g h t l y w i t h i n c r e a s i n g n i t r o g e n c o n t e n t f o r the a c r i d i n e - b a s e d c h a r s . Conversion decreased sharply at f i r s t , and t h e n more g r a d u a l l y , w i t h i n c r e a s i n g n i t r o g e n c o n t e n t f o r the p h e n a n t h r i d i n e - b a s e d c h a r s . The c o n v e r s i o n o f f u e l n i t r o g e n t o N 0 has been r e p o r t e d t o d e c r e a s e w i t h i n c r e a s i n g n i t r o g e n c o n t e n t i n c o a l (8) and p e t r o l e u m (9) combustion and i n n i t r o g e n - d o p e d flames (10). The p h e n a n t h r i d i n e - b a s e d c h a r s , w i t h one e x c e p t i o n ( t h e c h a r w i t h 0.98 wt% n i t r o g e n ) had lower c o n v e r s i o n s than the a c r i d i n e - b a s e d chars. T h i s s u g g e s t s f u r t h e r t h a t the c h a r p r e c u r s o r can i n f l u e n c e c h a r n i t r o g e n c o n v e r s i o n t o N0 . X

χ

X

X

The E f f e c t o f Char Sample S i z e on C o n v e r s i o n t o N0 . The e f f e c t o f c h a r sample weight on c o n v e r s i o n o t c h a r n i t r o g e n t o N 0 i s shown i n F i g u r e 11. The c o n v e r s i o n d e c r e a s e s w i t h i n c r e a s i n g sample s i z e o r more i m p o r t a n t l y w i t h i n c r e a s i n g h e i g h t o f the c h a r bed. The lower c o n v e r s i o n t o N 0 w i t h i n c r e a s i n g sample s i z e may be a consequence o f increased r e d u c t i o n of N0 t o N2 by the c h a r bed. The N 0 formed a t the bottom o f the bed i s reduced to N2 as i t passes upward through the bed, as p r e v i o u s l y o b s e r v e d by Baskakov ( 1 1 ) . One or more o f the f o l l o w i n g r e a c t i o n s may be r e s p o n s i b l e f o r l i m i t i n g N0 formation d u r i n g char o x i d a t i o n : X

X

X

X

X

X

CO + NO

-> 0.5

N

2

+

C0

NO + C ^ 0.5

N

2

+

CO

2N0

+ C •> N

2

+

C0

2

2

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

(1) (2) (3)

Factors Affecting

OREHOWSKY ET AL.

NO

Production

x

313

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1100

800

H

.

1

0

«

1

10

·

1

20

30

Time (min)

i g u r e 9.

Bed Temperature as a F u n c t i o n o f Time f o r P h e n a n t h r i d i n e Char O x i d a t i o n i n A i r f o r a Furnace Temperature o f 873 Κ

0 Η—-—ι—-—ι—•—ι—i—ι—-—ι—-—ι— —I 1

0

1

2

3

4

5

6

7

% Nitrogen in Char

F i g u r e 10. C o n v e r s i o n o f Char Ν t o NO Content

x

as a F u n c t i o n o f Char Ν

f o r a Range o f A c r i d i n e and P h e n a n t h r i d i n e -

Based Chars

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch026

314

THE CHEMISTRY OF ACID RAIN

1

0

2

Sample Weight (grams)

F i g u r e 11. E f f e c t

o f A c r i d i n e Char Sample Weignt on

o f Char Ν t o N 0

X

during Oxidation

Conversion

i n A i r a t 873 Κ

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

26.

Factors Affecting

OREHOWSKY ET AL.

NO

x

315

Production

The f i r s t r e a c t i o n i s r e p o r t e d l y slow i n the gas phase ( 1 2 ) . M e t a l c a t a l y s t s a r e o f t e n used t o promote the r e a c t i o n . R e a c t i o n s (2) and (3) have been the s u b j e c t o f o t h e r s t u d i e s i n which s y n t h e t i c m i x t u r e s o f combustion p r o d u c t s were passed over a h e a t e d bed o f carbon p a r t i c l e s . The r e s u l t s have i n d i c a t e d t h a t the r e d u c t i o n of N0 i s enhanced by: (a) i n c r e a s i n g the temperature (13-15), (b) i n c r e a s i n g s u r f a c e a r e a ( 1 3 ) , and ( c ) i n c r e a s i n g the c a r b o n bed h e i g h t ( 1 1 ) . As i n d i c a t e d e a r l i e r i n t h i s work, the con­ v e r s i o n o f c h a r n i t r o g e n t o N 0 was found t o d e c r e a s e w i t h i n c r e a s i n g r e a c t i o n temperature, i n c r e a s i n g sample s i z e , and was dependent on the type o f c h a r p r e c u r s o r . The r e s u l t s o f t h i s study a r e i n a g r e e ­ ment w i t h the c o n c l u s i o n t h a t N 0 f o r m a t i o n i s l i m i t e d by r e a c t i o n s (2) and ( 3 ) . As shown i n F i g u r e 10, the a c r i d i n e - b a s e d c h a r s , w i t h one excep­ t i o n , gave h i g h e r c o n v e r s i o n s o f char n i t r o g e n t o N 0 than d i d the p h e n a n t h r i d i n e - b a s e d c h a r s . The p h e n a n t h r i d i n e c h a r s , w i t h one ex­ c e p t i o n , had a h i g h e r r e a c t i v i t y i n a i r a t 873 Κ than the a c r i d i n e based c h a r s , T a b l e I I I . T h i s would suggest t h a t the p h e n a n t h r i d i n e based c h a r s have a s t r u c t u r e more ammenable t o g a s i f i c a t i o n by oxygen and/or NO . X

X

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch026

X

X

x

T a b l e 3.

Time R e q u i r e d

f o r 50% B u r n o f f f o r 1273 Time t o

Precursor 13% a c r i d i n e - 8 7 % anthracene 38% a c r i d i n e - 6 2 % a n t h r a c e n e 647o a c r i d i n e - 3 6 % a n t h r a c e n e 100% a c r i d i n e

Κ

Chars 50% (minutes)

64.,5 42.,0 49.,0 56.,6

103.,8 22.,3 39..1 34.,9

13% p h e n a n t h r i d i n e - 8 7 % phenanthrene 38% p h e n a n t h r i d i n e - 6 2 % phenanthrene 64% p h e n a n t h r i d i n e - 3 6 % phenanthrene 100% p h e n a n t h r i d i n e

Conclusions T h i s paper has r e p o r t e d on the r e l a t i v e r a t e s o f carbon and n i t r o g e n r e l e a s e and the f a c t o r s a f f e c t i n g N 0 f o r m a t i o n d u r i n g c h a r o x i d a ­ tion. A t 773 Κ and a t low b u r n o f f , carbon was s e l e c t i v e l y o x i d i z e d ; above t h i s temperature, the r a t e s o f c a r b o n and n i t r o g e n o x i d a t i o n were found t o be e q u a l . The c o n v e r s i o n o f char n i t r o g e n t o N 0 was found t o be s t r o n g l y dependent on the c h a r p r e c u r s o r ; the p r o p o r t i o n o f n i t r o g e n c o n v e r t e d t o N 0 was much lower f o r the p h e n a n t h r i d i n e c h a r than the a c r i d i n e c h a r . The n a t u r e o f the c h a r p r e c u r s o r i n ­ f l u e n c e s the c h e m i c a l and p h y s i c a l s t r u c t u r e o f the c a r b o n i z e d p r o d ­ uct. The h i g h r e a c t i v i t y o f the p h e n a n t h r i d i n e c h a r i n a i r s u g g e s t s t h a t i t s s t r u c t u r e may be more a c c e s s i b l e t o d i f f u s i n g gases and t h a t i t may c o n t a i n a h i g h e r p r o p o r t i o n o f carbon a c t i v e s i t e s than the a c r i d i n e char. The p r o p o r t i o n o f the l i b e r a t e d n i t r o g e n which was c o n v e r t e d t o N 0 was a l s o lower f o r the p h e n a n t h r i d i n e than the a c r i d i n e c h a r . I t i s b e l i e v e d t h a t the b a l a n c e o f n i t r o g e n i s r e l e a s e d as N2 due t o the r e d u c t i o n o f N 0 by C and/or CO. A h i g h c o n c e n t r a t i o n o f carbon X

X

X

X

X

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

THE CHEMISTRY OF ACID RAIN

316

a c t i v e s i t e s c a p a b l e o f e f f e c t i n g N 0 r e d u c t i o n would be c o n s i s t e n t w i t h the o b s e r v e d b e h a v i o r o f the p h e n a n t h r i d i n e c h a r s . I t was a l s o found t h a t the c o n v e r s i o n o f r e l e a s e d n i t r o g e n to N0 decreased with i n c r e a s i n g r e a c t i o n temperature, i n c r e a s i n g char n i t r o g e n c o n t e n t ( f o r both a c r i d i n e and p h e n a n t h r i d i n e - b a s e d chars) and w i t h i n c r e a s i n g sample weight (bed h e i g h t ) . I t appears t h a t N 0 r e d u c t i o n c o u l d p r o v i d e an e f f e c t i v e means to f u r t h e r l i m i t the p r o d u c t i o n o f N 0 from c h a r o x i d a t i o n . X

X

X

X

Acknowledgments

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch026

T h i s r e s e a r c h was s u p p o r t e d by the C o a l C o o p e r a t i v e Program o f The P e n n s y l v a n i a S t a t e U n i v e r s i t y and by the A l c o a F o u n d a t i o n .

Literature Cited 1. Smith, I., Nitrogen Oxides from Coal Combustion - Environmental Effects, IEA Coal Research Report Number IC TIS/TR10, October 1980. 2. Pershing, D. W., and Wendt, J. O. L., Ind. Eng. Chem., 18(1), 60, (1979). 3. Pereira, F. J . , Beer, J. Μ., Gibbs, Β., and Hedley, Α. Β., Fifteenth Symposium (International) on Combustion, P. 1149, The Combustion Institute, Pittsburgh, PA, (1974). 4. Manor, Υ., Suuberg, Ε. Μ., Ho, Μ., and Toor, H. L., Nineteenth Symposium (International) on Combustion, P. 1103, The Combustion Institute, Pittsburgh, PA, (1982). 5. Song, Υ. Η., Beer, J. Μ., and Sarofim, A. F., Comb. Sci. Tech., 28, 177, (1982). 6. Song, Υ. Η., Pohl, J. Η., Beer, J. Μ., and Sarofim, A. F., Comb. Sci. Tech., 28, 31, (1982). 7. Mathews, R. D., Sawyer, R. F., and Schefer, R. W., Env. Sci. Tech., 11, 1092, (1977). 8. Pershing, D. W., and Wendt, J. O. L., Sixteenth Symposium (International) on Combustion, P. 389, The Combustion Institute, Pittsburgh, PA, (1977). 9. Turner, D. W., Andrews, R. L., and Siegmund, C. W., Combustion, 44, 21, (1972). 10. Sarofim, A. F., AIChE Symposium Series, No. 148, 71, 51, (1972). 11. Basakov, A. P., Berg, Β. V., Shikov, V. Ν., Volkova, Α. Α., Tsymbalist, Μ. Μ., Turkoman, Α., Ashikhmin, Α. Α., Shul'Man, V. L., Berzrukov, M. V., and Unterbef, O. G., Thermal Engineering, 29, 496, (1982). 12. Fenimore, C. P., J. Am. Chem. Soc., 69, 3143, (1947). 13. Bedjai, G., Orbach, Η. Κ., and Riesenfeld, F. C., Ind. Eng. Chem., 50, 1165, (1958). 14. Fursawa, T., Kunii, D., Oguma, Α., and Yamada, Ν., Kagaku Kogaku, 562, (1977). 15. Shelef, Μ., and Otto, Κ., J. Coll. Interfac. Sci., 31, 73, (1969). RECEIVED May 13, 1987

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Chapter 27

Acid Clusters R. G. Keesee and A. W. Castleman, Jr.

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch027

Department of Chemistry, Pennsylvania State University, University Park, PA 16802

Gas phase molecular aggregates that contain acid molecules have been produced with free jet expansion techniques and detected by using electron impact ionization mass spectrometry. The clusters of aqueous nitric acid paralleled many properties of the condensed phase. Multiple nitric acid molecules were found in the clusters that were sufficiently dilute. The acid molecule was absent in the ionized clusters involving HCl and only water was evident. Experiments also demonstrated the reactivity of ammonia with aqueous nitric acid and sulfur dioxide clusters and of sulfur trioxide with water clusters. The natural occurrence of acid cluster negative ions offers a means to probe the gas phase acid loading of the atmosphere through laboratory and field studies of the ion chemistry.

The l a b o r a t o r y i n v e s t i g a t i o n of a phenomenon such as a c i d r a i n may p r o c e e d a l o n g s e v e r a l avenues. One extreme i n v o l v e s s i m u l a t i o n o f c o n d i t i o n s as i n smog o r c l o u d chambers i n which many p r o c e s s e s may o c c u r d u r i n g the c o u r s e of an e x p e r i m e n t . In t h i s manner, some i d e a of the o v e r a l l p i c t u r e may be g a i n e d . The o t h e r approach i s devoted to u n d e r s t a n d i n g b a s i c p r o p e r t i e s , such as a s p e c i f i c r e a c t i o n r a t e , upon which the l a r g e r p i c t u r e may be b u i l t . The l a t t e r t a c k i s t h a t which i s u n d e r t a k e n i n o u r l a b o r a t o r y . Specif i c a l l y , we a r e examining the c h e m i c a l and p h y s i c a l p r o p e r t i e s of molecular c l u s t e r s . M o l e c u l a r c l u s t e r s can be c o n s i d e r e d t o be the s m a l l e s t s i z e range of an a e r o s o l p a r t i c l e s i z e d i s t r i b u t i o n . N u c l e a t i o n from the gas phase t o p a r t i c l e s o r d r o p l e t s i n v o l v e s , i n t h e i n i t i a l s t a g e s , the f o r m a t i o n of c l u s t e r s . R e s e a r c h on c l u s t e r s p r o v i d e s a v a l u a b l e a p p r o a c h t o u n d e r s t a n d i n g , on a m o l e c u l a r l e v e l , the d e t a i l s of the t r a n s f e r of m o l e c u l e s from the gaseous t o the condensed s t a t e by e i t h e r new p a r t i c l e f o r m a t i o n o r heterogeneous p r o c e s s e s i n c l u d i n g a d s o r p t i o n onto o r d i s s o l u t i o n i n t o p a r t i c l e s .

0097-6156/87/0349-0317$06.00/0 © 1987 American Chemical Society

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

THE CHEMISTRY OF ACID RAIN

318

The o x i d a t i o n of s p e c i e s such as S O 2 , N 0 , and o r g a n i c compounds v i a gas-phase r e a c t i o n s , aqueous phase r e a c t i o n s i n the s o l u t i o n s of d r o p l e t s and a e r o s o l p a r t i c l e s , or s u r f a c e r e a c t i o n s on p a r t i c l e s ( e i t h e r s u r f a c e - g a s or s o l i d - l i q u i d i n t e r f a c e s ) produce a c i d s i n the atmosphere. The r e l a t i v e i m p o r t a n c e of the v a r i o u s mechanisms depends on f a c t o r s such as the a e r o s o l l o a d i n g , r e l a t i v e h u m i d i t y , and s o l a r i n t e n s i t y . The s t u d y of c l u s t e r s i s most r e l e v a n t t o c o n d i t i o n s i n w h i c h gas-phase r e a c t i o n s dominate a c i d p r o d u c t i o n and g a s - t o - p a r t i c l e c o n v e r s i o n proceeds through n u c l e a t i o n . For i n s t a n c e , the p r o p e n s i t y of s u l f u r i c a c i d m o l e c u l e s t o form s m a l l h y d r a t e d c l u s t e r s i s i m p o r t a n t t o the n u c l e a t i n g a b i l i t y of s u l f u r i c a c i d ( 1 ) . A major impetus, w h i c h i s a p p l i c a b l e t o the heterogeneous c h e m i s t r y of the atmosphere as w e l l as o t h e r a r e a s of r e e a r c h , f o r the s t u d y of c l u s t e r s i s the p r o s p e c t t h a t such work w i l l l e a d t o a b e t t e r u n d e r s t a n d i n g of surface i n t e r a c t i o n s ( 2 ) . C o n s e q u e n t l y , knowledge of the p r o p e r t i e s and f o r m a t i o n of c l u s t e r s c o n t a i n i n g a c i d s c o n t r i b u t e s t o an u n d e r s t a n d i n g of some of the p r o c e s s e s i n v o l v e d i n the development of a c i d r a i n . T h i s paper p r e s e n t s an o v e r v i e w of r e s u l t s on the f o r m a t i o n and s t a b i l i t y of b o t h n e u t r a l and i o n i c acid clusters.

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch027

X

Neutral Acid Clusters W i t h f r e e j e t e x p a n s i o n t e c h n i q u e s , we have produced c l u s t e r s of aqueous n i t r i c a c i d (_3 ), h y d r o c h l o r i c a c i d , s u l f u r i c a c i d (4^), pure a c e t i c a c i d ( 5 ) , and s u l f u r d i o x i d e ( 6 ) . For analogy t o b u f f e r i n g , the f o r m a t i o n of c l u s t e r s c o n t a i n i n g ammonia have a l s o been examined. These have i n c l u d e d ammonia w i t h aqueous n i t r i c a c i d (7_)> hydrogen s u l f i d e (7_), and s u l f u r d i o x i d e ( 8 ) . The b a s i c experiment i n v o l v e s e x p a n s i o n of vapor t h r o u g h a n o z z l e , c o l l i m a t i o n of the j e t w i t h a skimmer t o form a w e l l - d i r e c t e d m o l e c u l a r beam, and d e t e c t i o n of c l u s t e r s v i a e l e c t r o n impact i o n i z a t i o n and q u a d r u p o l e mass s p e c t r o m e t r y . Some v a r i a t i o n s i n c l u d e the i n t r o d u c t i o n of a r e a c t i v e gas i n t o vacuum near the e x p a n s i o n as d e s c r i b e d elsewhere (4,8) and the i m p l e m e n t a t i o n of an e l e c t r o s t a t i c q u a d r u p o l a r f i e l d t o examine the p o l a r i t y of the n e u t r a l c l u s t e r s . The e l e c t r i c d e f l e c t i o n t e c h n i q u e i s d e s c r i b e d by Kleraperer and coworkers ( 9 ) . Background on the p r o p e r t i e s of f r e e j e t e x p a n s i o n s i s d e s c r i b e d by Anderson ( 1 0 ) and Hagena ( 1 1 ) . A few i m p o r t a n t p o i n t s t o n o t e f o l l o w . The c l u s t e r d i s t r i b u t i o n s themselves a r e k i n e t i c a l l y quenched due t o a t r a n s i t i o n t o a f r e e m o l e c u l a r f l o w ( e s s e n t i a l l y c o l l i s i o n a l l e s s ) regime a f t e r a s h o r t d i s t a n c e (a few n o z z l e d i a m e t e r s ) from the n o z z l e t i p . The d i r e c t e d m o t i o n of the gas c r e a t e d by the e x p a n s i o n l e a d s t o a c o o l i n g of the t r a n s l a t i o n a l temperature due t o a n a r r o w i n g of the v e l o c i t y d i s t r i b u t i o n o f the m o l e c u l e s i n the j e t . R e l a x a t i o n of i n t e r n a l degrees of freedom a l s o o c c u r s but g e n e r a l l y the quenched temperatures are i n the o r d e r T ( v i b ) > T ( r o t ) > T ( t r a n s ) . W i t h c l u s t e r i n g , the l a t e n t heat of c o n d e n s a t i o n c o n t r i b u t e s t o an e x c i t a t i o n of the i n t e r n a l

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

27.

Acid

KEESEE & CASTLEMAN

319

Clusters

modes o f t h e c l u s t e r w h i c h t h e c o l d c o l l i s i o n s may not f u l l y relax. A f u r t h e r n o t e i s t h a t f o r purposes o f mass i d e n t i f i c a t i o n and detection, the neutral c l u s t e r s are ionized. The i o n i z e d d i s t r i ­ b u t i o n o f c l u s t e r s i z e s may n o t f a i t h f u l l y r e p r e s e n t t h e n e u t r a l s i z e d i s t r i b u t i o n i n a one-to-one correspondence due t o f r a g m e n t a ­ t i o n upon i o n i z a t i o n , i o n s t a b i l i t y , i o n i z a t i o n c r o s s - s e c t i o n s , and mass d i s c r i m i n a t i o n i n t h e s p e c t r o m e t e r . F o r most o f t h e c l u s t e r s d e s c r i b e d h e r e w h i c h i n v o l v e hydrogen b o n d i n g , i o n i z a t i o n o f t h e neutral c l u s t e r usually leads t o a protonated c l u s t e r v i a a r e a c t i o n t y p i f i e d by +

(NH ) (NH ) Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch027

3

3

+

n

NH^N^Vi

+ NH

2

(1)

where t h e i o n i z e d m o l e c u l a r u n i t o f t h e c l u s t e r s p o n t a n e o u s l y reacts w i t h a neighboring molecule (12). The p r o d u c t i o n may be v i b r a t i o n a l l y h o t and undergo f u r t h e r d i s s o c i a t i o n . Attempts t o u n d e r s t a n d t h e s e d i s s o c i a t i o n p r o c e s s e s i n our l a b o r a t o r y (12) as w e l l as o t h e r s (13,14) a r e b e i n g made i n o r d e r t o b e t t e r i n t e r p r e t r e s u l t s such as those d e s c r i b e d below. W i t h t h e s e fundamental p r o c e s s e s i n mind, we can proceed t o d i s c u s s r e s u l t s c o n c e r n i n g acid clusters. I n t h e s t u d y o f aqueous n i t r i c a c i d (_3), d e u t e r a t e d s p e c i e s were used t o a v o i d a m b i g u i t y i n s t o i c h i o m e t r y . C l u s t e r s were produced by t h e e x p a n s i o n o f t h e vapor from heated c o n c e n t r a t e d aqueous n i t r i c a c i d . E l e c t r o n impact i o n i z a t i o n o f t h e c l u s t e r s produced i o n s o f t h e form D ( D N 0 3 ) ( U 2 0 ) y . I n t h e case o f t h e c l u s t e r s c o n t a i n i n g one n i t r i c a c i d m o l e c u l e , a d i s t i n c t l o c a l minimum o f t h e s i g n a l i n t e n s i t y i n t h e s i z e d i s t r i b u t i o n o c c u r s a t the c l u s t e r s i z e D ( D N 0 3 ) ( 0 2 0 ) 4 . S i n c e no e x p l a n a t i o n based on i o n s t a b i i t y seems f e a s i b l e , an a t t r a c t i v e e x p l a n a t i o n o f t h e p o s i t i o n of t h e minimum i s t h a t i t i s i n d i c a t i v e o f some r a t h e r abrupt t r a n s f o r m a t i o n o f t h e p r e c u r s o r n e u t r a l s i n t h i s s i z e range. Such a s i t u a t i o n might occur i f a complex became s u f f i c i e n t l y h y d r a t e d t o e n a b l e t h e f o r m a t i o n o f s o l v a t e d i o n p a i r s . A l a r g e change i n the charge d i s t r i b u t i o n w i t h i n t h e c l u s t e r s h o u l d o c c u r upon s o l v a t i o n t o form an i o n p a i r ΝΟβ-ζΙ^Ο^ΗβΟ*. A more p o l a r s p e c i e s s h o u l d have a l a r g e r c o l l i s i o n r a t e and hence a f a s t e r growth r a t e . T h i s e f f e c t s h o u l d m a n i f e s t i t s e l f i n t h e observed i n t e n s i t y d i s t r i b u t i o n as an i n c r e a s e i n i n t e n s i t y o f t h e l a r g e r s i z e d c l u s t e r s j u s t beyond t h e c l u s t e r t h a t underwent t h e i o n - p a i r formation. R e c e n t l y i o n - p a i r f o r m a t i o n i n c l u s t e r s has been suggested t o e x p l a i n t h e abrupt l i n e w i d t h broadening and s p e c t r a l changes i n t h e f l u o r e s c e n c e o f oi-naphthol(NH3) when η reaches f o u r a p p a r e n t l y t o y i e l d α-naphtholate · (ΝΪ^^ΝΗ^" " ( 1 5 ) . Ab i n i t i o c a l c u l a t i o n s on the h y d r a t i o n o f NH^F (16) and NaH P04 (17_) have shown t h a t as few as s i x water m o l e c u l e s a r e s u f f i c i e n t t o c r e a t e a s o l v a t e d i o n p a i r i n w h i c h t h e i o n s become s e p a r a t e d by s o l v e n t . For c l u s t e r s w i t h more than one n i t r i c a c i d m o l e c u l e , t h e s p e c i e s ( D N 0 3 ) ( D 2 0 ) (l l ) a r e n o t d e t e c t e d even though t h e HNO3 dimer has been o b s e r v e d ( 1 8 ) i n an e x p a n s i o n i n v o l v i n g anhydrous H N O 3 . The i n t e r e s t i n g a n a l o g y i n t h i s c a s e i s t h a t c o n c e n t r a t e d aqueous n i t r i c a c i d s o l u t i o n s a r e p h o t o c h e m i c a l l y and t h e r m a l l y u n s t a b l e and decompose v i a t h e s t o i c h i o m e t r y +

X

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch027

2HN0

2N0

3

2

+ H 0 + 1/2 0 2

(2)

2

A p p a r e n t l y t h e e x o t h e r m i c i t y o f t h e c l u s t e r i n g o r e l e c t r o n impact i o n i z a t i o n s u p p l i e s t h e energy which i n i t i a t e s t h i s d e c o m p o s i t i o n i n t h e c l u s t e r s t h a t c o n t a i n t o o much n i t r i c a c i d compared t o t h e number o f s o l v e n t water m o l e c u l e s . When i n t r o d u c e d as a r e a c t a n t , ammonia appears t o be p r e f e r e n t i a l l y i n c o r p o r a t e d ( v i a H 0 replacement) i n t o c l u s t e r s c o n t a i n i n g HNO3 l e a v i n g t h e pure H 0 c l u s t e r s r e l a t i v e l y u n a f f e c t e d (7_). P r o d u c t i o n s o f t h e form Η ( Η Ν 0 ) ( Ν Η ) ( Η 0 ) w i t h x=0,l, y=0,l,2, and ζ up t o 7 a r e e a s i l y r e s o l v a b l e . Higher c l u s t e r s a r e a l s o o b s e r v e d , b u t w i t h low i n t e n s i t y ; t h e N H 3 / H 0 s t o i c h i o m e t r y was u n r e s o l v e d f o r t h e s e because o f p o o r e r mass r e s o l u t i o n . When t h e v a p o r from a b o i l i n g s o l u t i o n o f 6M HC1 i s expanded, t h e d e t e c t e d c l u s t e r i o n s l a c k HC1 as e v i d e n c e d by t h e absence o f the c h a r a c t e r i s t i c m+2 i s o t o p e due t o ^ ^ C l . On t h e o t h e r hand, t h e o b s e r v e d H ( H 0 ) d i s t r i b u t i o n i s n o t i c e a b l y d i f f e r e n t than t h a t o b t a i n e d i n t h e e x p a n s i o n o f pure water. For instance, the usual prominent d i s c o n t i n u i t i e s a t H ( H 0 ) 4 and H ( H 0 ) i a r e n o t e v i d e n t and a s l i g h t l o c a l minimum i n i n t e n s i t y o c c u r s a t Η ( Η 0 ) ΐ 3 · The i n d i c a t i o n i s t h a t HC1 i s i n i t i a l l y p r e s e n t i n t h e n e u t r a l c l u s t e r but t h a t i o n i z a t i o n l e a d s t o " b o i l i n g o f f " o f HC1. The m o l e c u l a r i o n s H ^ C 1 and H ^ C 1 a r e o b s e r v e d . E x p a n s i o n o f t h e vapor o v e r N H 4 S a l s o r e s u l t s i n an i o n i z e d c l u s t e r d i s t r i b u t i o n i n which one of t h e e x p e c t e d components, namely H S , i s absent ( 7 ) . Q u i t e u n l i k e t h e d i s t r i b u t i o n o b t a i n e d from t h e e x p a n s i o n o f pure ammonia, a s t r o n g l o c a l minimum s i m i l a r t o t h e H ( H N 0 3 ) ( H 0 ) d i s t r i b u t i o n i s present. In o r d e r t o e x p l o r e a d s o r p t i o n and heterogeneous p r o c e s s e s on a molecular s c a l e , i t i s of i n t e r e s t t o study the r e a c t i o n s of gases w i t h c l u s t e r s . We have performed one s e r i e s o f e x p e r i m e n t s i n which ammonia was expanded from t h e n o z z l e and S 0 was i n t r o d u c e d as a r e a c t a n t t h r o u g h t h e a n n u l a r o p e n i n g around t h e n o z z l e , and a n o t h e r s e r i e s i n w h i c h t h e r o l e s o f t h e gases were r e v e r s e d (8). W i t h ammonia i n t r o d u c e d v i a t h e n o z z l e (500 t o r r s t a g n a t i o n p r e s s u r e ) and when t h e S 0 p r e s s u r e b e h i n d t h e o u t e r a n n u l a r o p e n i n g i s 40 t o r r , i o n i z e d c l u s t e r s o f t h e form ( N H 3 ) S 0 and H ( N H 3 ) S 0 a r e d e t e c t e d . When t h e S 0 p r e s s u r e i s r e d u c e d t o 20 t o r r , no e v i d e n c e of S 0 i n c o r p o r a t i o n i n t o t h e ammonia c l u s t e r s i s found. A p e c u l i a r f e a t u r e i s that the unprotonated s p e c i e s e x h i b i t a normal s i z e d i s t r i b u t i o n , whereas t h e p r o t o n a t e d c l u s t e r s are s t r o n g l y peaked a t NH^+N^SO^ On t h e o t h e r hand, i o n i z a t i o n 2

2

+

3

χ

3

ν

2

ζ

2

+

2

n

+

+

2

2

2

+

2

5

+

7

+

2

+

2

n

2

2

+

n

+

n

2

2

2

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

2

27.

Acid

KEESEE & CASTLEMAN

321

Clusters

of p u r e ammonia c l u s t e r s r e s u l t s a l m o s t e x c l u s i v e l y i n p r o t o n a t e d c l u s t e r s due t o the i n t e r n a l c l u s t e r r e a c t i o n ( 3 ) . When s u l f u r d i o x i d e i s i n t r o d u c e d t h r o u g h the n o z z l e and the amount of ammonia b e h i n d the a n n u l a r o p e n i n g v a r i e s f r o m 6 to 50 t o r r , the e x t e n t of ammonia i n c o r p o r a t i o n i n t o the c l u s t e r s d r a m a t i c a l l y i n c r e a s e s w i t h i n c r e a s i n g ammonia p r e s s u r e . Up t o two ammonia m o l e c u l e s were o b s e r v e d to be i n c o r p o r a t e d i n t o the c l u s t e r s w i t h 20 t o r r of ammonia b e h i n d the a n n u l a r o p e n i n g . With 40 t o r r , up t o f o u r N H 3 m o l e c u l e s were o b s e r v e d i n the c l u s t e r s . I n a d d i t i o n , c l u s t e r s c o n t a i n i n g one N H 3 m o l e c u l e become more p r e v a l e n t t h a n the pure ( S 0 ) clusters. The p r o b a b i l i t y t h a t a c l u s t e r of η S 0 m o l e c u l e s c o n t a i n e d one o r more NH3 m o l e c u l e s a p p r o x i m a t e l y d o u b l e d from n=2 to 8 i n a g r a d u a l manner. Based on o n l y the c l u s t e r h a r d - s p h e r e c o l l i s i o n c r o s s - s e c t i o n , a dependence o f n2/3 ( f a c t o r of 4 i n c r e a s e ) might be e x p e c t e d . However, s e v e r a l o t h e r e f f e c t s must a l s o be c o n s i d e r e d i n c l u d i n g the e x t e n t o f d i s s o c i a t i o n upon i o n i z a t i o n , the r e l a t i v e i n t e r n a l t e m p e r a t u r e s o f the c l u s t e r s , and the l i m i t e d number of i n t e r n a l d e g r e e s of freedom i n the c l u s t e r s . +

2

n

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch027

2

o r

a

In g e n e r a l , the o b s e r v e d c l u s t e r d i s t r i b u t i o n s a r e smooth and i n n e i t h e r s e r i e s of e x p e r i m e n t s i s any p r e f e r e n c e f o r a p a r t i c u l a r s t o i c h i o m e t r i c r a t i o a p p a r e n t , e x c e p t f o r NH^+N^SO;? i n the protonated d i s t r i b u t i o n . These e x p e r i m e n t s a l s o d e m o n s t r a t e t h a t the n o z z l e d e s i g n r e s u l t s i n the r e a c t i o n of the s p e c i e s e x i t i n g f r o m the a n n u l a r o p e n i n g w i t h c l u s t e r s of the s p e c i e s i n t r o d u c e d t h r o u g h the i n n e r n o z z l e . The a d d i t i o n o f ammonia t o S 0 clusters was found t o be more e f f e c t i v e t h a n the a d d i t i o n of S 0 to NH3 clusters. Some e x p l a n a t i o n s i n c l u d e a h i g h e r p r o b a b i l i t y of S0 e v a p o r a t i o n upon i o n i z a t i o n , l e s s s e v e r e beam s c a t t e r i n g w i t h N H 3 c o l l i s i o n s on S 0 c l u s t e r s , o r a d i f f e r e n t r e a c t i v i t y (accommodation c o e f f i c i e n t s ) i n the two c a s e s . 2

2

2

2

A s t u d y of the r e a c t i o n of s u l f u r t r i o x i d e w i t h water c l u s t e r s has a l s o been made (4_)· The i o n c l u s t e r s o b s e r v e d i n t h e s e e x p e r i m e n t s were a s e r i e s of p r o t o n a t e d w a t e r c l u s t e r s H ( H 0 ) n w i t h η up to 14 and a n o t h e r l e s s abundant s e r i e s of the form S 0 3 ( H 0 ) H w i t h η up t o 9 . The H + ( H 0 ) s e r i e s c o u l d r e s u l t f r o m the i o n i z a t i o n of u n r e a c t e d w a t e r c l u s t e r s and a l s o from the i o n i z a t i o n of S 0 3 ( H 0 ) c l u s t e r s . The r e l a t i v e d i s t r i b u t i o n of the H (H 0) s e r i e s , however, was not a p p r e c i a b l y a f f e c t e d by t h e i n t r o d u c t i o n of S O 3 . The S03(H 0) H" " d i s t r i b u t i o n was v e r y s i m i l a r i n f o r m t o the H ( H N 0 3 ) ( H 0 ) d i s t r i b u t i o n o b s e r v e d f r o m the e x p a n s i o n of aqueous n i t r i c a c i d vapor i n t h a t a l o c a l i n t e n s i t y minimum ( a t n=4 f o r the S 0 3 ( H 0 ) H d i s t r i b u t i o n ) was o b s e r v e d . The S O 3 f l u x was such t h a t no masses c o r r e s p o n d i n g t o more t h a n one S O 3 m o l e c u l e i n a c l u s t e r were d e t e c t e d . E l e c t r o s t a t i c focusing d e m o n s t r a t e d t h a t the S 0 3 H 0 adduct, e x p e c t e d t o be the i n i t i a l product, r a p i d l y isomerized to H S04« +

2

+

2

n

2

2

n

m

+

2

n

1

2

n

+

2

n

+

2

n

#

2

2

E l e c t r o s t a t i c d e f l e c t i o n e x p e r i m e n t s have shown the a c i d - w a t e r a d d u c t s t o be p o l a r . However, l a r g e r c l u s t e r s e x h i b i t d e f o c u s i n g b e h a v i o r i n d i c a t i v e of a p o l a r i z a b l e , but e s s e n t i a l l y n o n p o l a r , species. Only f o r the pure a c e t i c a c i d c l u s t e r s , s p e c i f i c a l l y the

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

322

THE CHEMISTRY OF ACID RAIN

t r i m e r and i n d i c a t i o n s a l s o f o r t h e pentamer o r l a r g e r was p o l a r i t y o f l a r g e r c l u s t e r s e v i d e n t ( 5 ) . Ionic Acid

Clusters

E x a m i n a t i o n o f t h e c l u s t e r i n g o f n e u t r a l m o l e c u l e s onto i o n s i s a n o t h e r approach t o t h e s t u d y o f a c i d c l u s t e r s . Cluster ions observed i n t h e atmosphere r e f l e c t t h e r o l e o f a c i d s . Strong a c i d s a r e p r e f e r e n t i a l l y c l u s t e r e d t o n e g a t i v e i o n s w h i c h a c t as bases. Under normal a t m o s p h e r i c c o n d i t i o n s , ambient i o n s o f t h e type HS04"(H S04) (HN0 ) or N03"(HN0 ) (the l a t t e r a l s o probably h y d r a t e d i n t h e lower t r o p o s p h e r e ) have been observed throughout the l o w e r atmosphere (19,20). L a b o r a t o r y s t u d i e s have been made o f t h e thermodynamic s t a b i l i t y o f N 0 ~ ( H N 0 ) c l u s t e r s (21,22) and t h e r e a c t i v i t y o f n i t r i c a c i d ( 2 3 ) and s u l f u r i c a c i d "Ç24) w i t h n e g a t i v e i o n s . Through t h e s e s t u d i e s , an u n d e r s t a n d i n g o f the pathways t o t h e p r o d u c t i o n s o f t h e a c i d c l u s t e r s and t h e i r r e l a t i o n s h i p t o t h e gas-phase a c i d l o a d i n g o f t h e atmosphere has been d e v e l o p e d . Consequently, i n c o n j u n c t i o n w i t h these l a b o r a t o r y r e s u l t s , i n s i t u d e t e c t i o n of t h e r e l a t i v e ambient abundance o f t h e s e i o n i c c l u s t e r s a l l o w s e s t i m a t e s t o be made o f t h e gas-phase c o n c e n t r a t i o n o f these a c i d s . Heitman and A r n o l d (19) e s t i m a t e from t h e i r measurements t h a t t h e gaseous a c i d i c s u l f u r c o n c e n t r a t i o n i n t h e 12 t o 8 km a l t i t u d e range i s 1 0 t o 10^ m o l e c u l e s cm""^. Once a g a i n , t h e l a r g e s t u n c e r t a i n t y i n t h e s e r e s u l t s i s f r a g m e n t a t i o n ; i n t h i s case t h e f r a g m e n t a t i o n t h a t o c c u r s upon e x t r a c t i n g ambient i o n s i n t o t h e mass s p e c t r o m e t e r . Recent s t u d i e s i n d i c a t e t h a t o b s e r v a t i o n s o f S 0 o r HS0 a s s o c i a t e d w i t h ambient c l u s t e r i o n s o f t h e s t r a t o s phere p r o b a b l y a r e n o t due t o c l u s t e r i n g w i t h t h e ambient g a s e s , but r e s u l t from f r a g m e n t a t i o n o f s u l f u r i c a c i d i n t h e c l u s t e r i o n s (25). The observed p o s i t i v e i o n s a r e p r o t o n a t e d c l u s t e r s c o n t a i n i n g w a t e r and h i g h p r o t o n a f f i n i t y s p e c i e s such as a c e t o n i t r i l e i n t h e l o w e r s t r a t o s p h e r e (26) o r ammonia i n t h e l o w e r t r o p o s p h e r e ( 2 0 ) . Other h i g h p r o t o n a f f i n i t y s p e c i e s such as p y r i d i n e and p i c o l i n e s may e n t e r i n t o t h e p o s i t i v e i o n c h e m i s t r y o f t h e lower t r o p o s p h e r e ( 2 7 , 2 8 ) . F u r t h e r d i s c u s s i o n o f t h e s e s t u d i e s and t h e e x p e r i m e n t a l t e c h n i q u e s can be found elsewhere ( 2 8 , 2 9 ) . 2

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch027

clusters,

x

3

y

3

3

3

n

n

6

3

3

Acknowledgments Support by t h e Department of Energy, Grant No. DE-ACO2-82-ER60055, and t h e N a t i o n a l S c i e n c e F o u n d a t i o n , Grant No. ATM-82-04010, i s g r a t e f u l l y acknowledged.

Literature Cited 1. Heist, R. H.; Reiss, H. J. Chem. Phys. 1974, 61, 573. 2. Whetten, R. L . ; Cox, D. M.; Trevor, D. J.; Kaldor, A. Surf. Sci. 1985, 156, 8. See also other papers in that volume.

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ch027

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Clusters

323

3. Kay, B. D.; Herman, V.; Castleman, A. W., Jr. Chem. Phys Lett. 1981, 80, 469. 4. Sievert, R.; Castleman, A. W. Jr. J. Phys. Chem. 1984, 88, 3329. 5. Sievert, R.; Cadez, I.; Van Doren, J.; Castleman, A. W., Jr. J. Phys. Chem. 1984, 88, 4502. 6. Castleman, A. W., Jr.; Kay, B. D. Int. J. Mass Spectrom. Ion Proc. 1985, 66, 217. 7. Kay, B. D.; Hofmann-Sievert, R.; Castleman, A. W., Jr. Chem. Phys. 1986, 102, 407. 8. Keesee, R. G.; Kilgore, K.; Breen, J. J.; Castleman, A. W., Jr. J. Aerosol Sci. Tech., in press. 9. Falconer, W. E.; Buchler, Α.; Stauffer, J. L . ; Klemperer, W. J. Chem. Phys. 1968, 48, 312. 10. Anderson, J. B. In "Molecular Beams and Low Density Gas Dynamics"; Wegener, D. P., Ed.; Marcel Dekker:New York, 1974, pp. 1-91. 11. Hagena, O. F. In "Molecular Beams and Low Density Gas Dynamics"; Wegener, D. P., Ed.; Marcel Dekker:New York, 1974, pp. 93-181. 12. Echt, O.; Dao, P. D.; Morgan, S.; Castleman, A. W., Jr. J. Chem. Phys. 1985, 82, 4076. 13. Buck, U.; Meyer, H. Phys. Rev. Lett. 1984, 52, 109. 14. Kamke, W.; Kamke, B.; Kiefl, H. U.; Hertel, I. V. J. Chem. Phys. 1986, 84, 1325. 15. Cheshnovsky, O.; Leutwyler, S. Chem. Phys. Lett. 1985, 121, 1. 16. Odutola, J. Α.; Dyke, T. R. J. Chem. Phys. 1978, 68, 5663. 17. Kollman, P.; Kuntz, I. J. Am. Chem. Soc. 1976, 98, 6820. 18. Lee, W. K.; Prohofsky, E. W. Chem. Phys. Lett. 1982, 85, 98. 19. Heitmann, H.; Arnold, F. Nature. 1983, 306, 747. 20. Perkins, M. D.; Eisele, F. L. J. Geophys. Res. 1984, 89, 9649. 21. Davidson, J . Α.; Fehsenfeld, F. C.; Howard, C. J. Int. J. Chem. Kinet. 1977, 9, 17. 22. Lee, N.; Keesee, R. G.; Castleman, A. W., Jr. J. Chem. Phys. 1980, 72, 1089. 23. Fehsenfeld, F. C.; Howard, C. J.; Schmeltekopf, A. L. J. Chem. Phys. 1975, 63, 2835. 24. Viggiano, Α. Α.; Perry, R. Α.; Albritton, D. L . ; Ferguson, E. E.; Fehsenfeld, F. C. J. Geophys. Res. 1982, 87, 7340. 25. Schlager, H.; Arnold, F. Planet. Space Sci. 1986, 34, 245. 26. Arijs, E.; Brasseur, G. J. Geophys. Res. 1986, 91, 4003. 27. Eisele, F. L . ; McDaniel, E. W. J. Geophys. Res. 1986, 91, 5183. 28. Keesee, R. G.; Castleman, A. W., Jr. J. Geophys. Res. 1985, 90, 5885. 29. Keesee, R. G.; Castleman, A. W., Jr. Ann. Geophys. 1983, 1, 75. RECEIVED May 5, 1987

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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Author Index Anderson, David L., 84 Aoyama, M , 258 Bahnemann, Detlef W., 120 Bhatia, S. C , 170 Brachaczek, W. W., 28 Calkins, William, iii Castleman, A. W., Jr., 317 Chapman, E . G., 219 Charlson, Robert J., 204 Church, Thomas M , 39 Covert, David S., 204 Dasch, Jean Muhlbaier, 242 Derbyshire, Francis J., 304 Dokiya, Y., 258 Drake, J. J., 213 Elzerman, A. Z., iii Galloway, James N., 39 Gertler, A . W., 183 Gordon, Glen E., x,2,6 Gorse, R. Α., Jr., 28 Hall, J. H., Jr., 170 Harris, G . W., 274 Hashimoto, Yoshikazu, 158 Herrmann, G . J., 142 Hicks, Β. B., 196 Hidy, G . M , 10 Hoffmann, Michael R., 120,250 Hong, Andrew P., 120 Hosker, R. P., Jr., 196 Hynes, A . J., 133 Jacob, Daniel J., 250 Jaeschke, W. Α., 142 Japar, S. M , 28 Johnson, Russell W., χ Katsuragi, Y., 258 Keeler, G . J., 28 Keesee, R. G , 317 Kitto, Michael E., 84 Knap, Anthony H., 39 Kormann, Claudius, 120 Landsberger, S., 213 Larson, Timothy V., 204

Lee, J. H., 109 Lev-On, M , 229 Lewis, C. W., 58 Mackay, G. I., 274 Miller, D. R, 183 Miller, John M , 39 Miller, Theresa, 204 Munger, J. William, 250 Norbeck, J. M , 28 O'Loughlin, John F., 204 Olmez, I., 66 Orehowsky, Gregory J., 304 Parrington, J. R., 66 Paur, R. J., 66 Peterson, Richard, 204 Pierson, W. R., 28 Pollack, A . K., 229 Robinson, N. F., 183 Scaroni, Alan W., 304 Schiff, Η. I., 274 Schwartz, Stephen E., 93 Shaw, R. W., Jr., 66 Sklarew, D. S., 219 Stevens, R. K., 58 Stevenson, Margaret N., 204 Sweet, Ian, 204 Tanaka, Shigeru, 158 Tang, I. N., 109 Tanner, Roger L., 289 Toda, S., 258 Topol, L . E., 229 Tuncel, S. G , 66 Vermette, S. J., 213 Vong, Richard J., 204 Waldman, Jed M , 250 Whelpdale, Douglas M , 39 Wine, P. H., 133 Womack, J. D., 196 Yamanaka, Kazuo, 158 Yoshimura, E., 258 Zoller, William R , 204

Affiliation Index Brookhaven National Laboratory, 93,109,289 California Institute of Technology, 250 Desert Research Institute, 10

Atlanta University Center, 170 Atmospheric Environment Service, 39 Bermuda Biological Station, 39

326

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INDEX

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Environmental Monitoring and Services, 229 Ford Motor Company, 28 General Motors Research Laboratory, 242 Georgia Institute of Technology, 133,170 J. W. Goethe-University, 142 Keio University, 158 McMaster University, 213 Meteorological Research Institute, 258 National Oceanic and Atmospheric Administration, 39,196 Pacific Northwest Laboratory, 219 Pennsylvania State University, 304,317

Systems Applications, 229 U.S. Environmental Protection Agency, 58,66 Unisearch Associates, 274 University of Delaware, 39 University of Maryland,x,2,66,84 University of Michigan, 28 University of Nevada System, 183 University of Tokyo, 258 University of Virginia, 39 University of Washington, 204 W. M Keck Laboratories, 120

Subject Index Acid Rain-Continued research, 2-8 susceptibility of soil, 270/ Absorption, H S 0 , 180 See also Acid precipitation Accommodation coefficients Acidic gases, collection from coal-fired calculations, 111 power plants, 84-91 measurements, 104-105 Acridine, nitrogen contents, 305 ozone, 109-116 Acridine char sulfur dioxide, 109-116,154 carbon and nitrogen reactivities, 306-309 Accuracy, estimation for an instrument, 188 conversions of char nitrogen to Acetate ions, introduction into Ν Ο , 312,315 precipitation, 219-227 sample weight effect on conversion to Acetic acid Ν Ο , 314/ atmospheric sources, 50-51 See also Chars clear air observations, 224/ Acridine char nitrogen, retention as formation function of burnoff, 307/, 308/ aerosol scavenging pathway, 223 Advection fluxes, calculation, 41-43 aqueous-phase oxidation pathway, 223-225 Aerosol particle size distribution, gas-phase concentration, 221 molecular clusters, 317 homogeneous gas-phase production, 225 Aerosol scavenging pathway, acetic and Acid, production, 318 formic acid formation, 223 Acid clusters, 317-322 Aerosol species, transformation over the ion-pair formation, 319 western Atlantic, 52 neutral, 318-322 Aerosol sulfate reaction with gases, 320-321 airborne determination, 298 See also Ionic acid clusters, Neutral acid See also Sulfate clusters Air flux, function of latitude and Acid deposition longitude, 44/ Allegheny Mountain, 28-36 Air pollutants, transport, 4 rain, 30 Air sampling—See Interstitial air sampling See also Deposition, Dry deposition, Wet Aldehydes, determination in atmospheric deposition samples, 299 Acid precipitation Allegheny Mountain susceptibility of Japanese soils, 271 acid deposition and atmospheric See also Acid rain chemistry, 28-36 Acid rain deposition budgets for sulfate and alternative research strategies, 6-8 nitrate, 33 formation pathway, 129 Allegheny Mountain study, 7 laboratory investigation, 317 Ammonia nitrogen oxide role, 304 effect on atmospheric acidity, 254 present knowledge, 4 incorporation into acid clusters, 320 A

3

χ

χ

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INDEX

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ix002

Environmental Monitoring and Services, 229 Ford Motor Company, 28 General Motors Research Laboratory, 242 Georgia Institute of Technology, 133,170 J. W. Goethe-University, 142 Keio University, 158 McMaster University, 213 Meteorological Research Institute, 258 National Oceanic and Atmospheric Administration, 39,196 Pacific Northwest Laboratory, 219 Pennsylvania State University, 304,317

Systems Applications, 229 U.S. Environmental Protection Agency, 58,66 Unisearch Associates, 274 University of Delaware, 39 University of Maryland,x,2,66,84 University of Michigan, 28 University of Nevada System, 183 University of Tokyo, 258 University of Virginia, 39 University of Washington, 204 W. M Keck Laboratories, 120

Subject Index Acid Rain-Continued research, 2-8 susceptibility of soil, 270/ Absorption, H S 0 , 180 See also Acid precipitation Accommodation coefficients Acidic gases, collection from coal-fired calculations, 111 power plants, 84-91 measurements, 104-105 Acridine, nitrogen contents, 305 ozone, 109-116 Acridine char sulfur dioxide, 109-116,154 carbon and nitrogen reactivities, 306-309 Accuracy, estimation for an instrument, 188 conversions of char nitrogen to Acetate ions, introduction into Ν Ο , 312,315 precipitation, 219-227 sample weight effect on conversion to Acetic acid Ν Ο , 314/ atmospheric sources, 50-51 See also Chars clear air observations, 224/ Acridine char nitrogen, retention as formation function of burnoff, 307/, 308/ aerosol scavenging pathway, 223 Advection fluxes, calculation, 41-43 aqueous-phase oxidation pathway, 223-225 Aerosol particle size distribution, gas-phase concentration, 221 molecular clusters, 317 homogeneous gas-phase production, 225 Aerosol scavenging pathway, acetic and Acid, production, 318 formic acid formation, 223 Acid clusters, 317-322 Aerosol species, transformation over the ion-pair formation, 319 western Atlantic, 52 neutral, 318-322 Aerosol sulfate reaction with gases, 320-321 airborne determination, 298 See also Ionic acid clusters, Neutral acid See also Sulfate clusters Air flux, function of latitude and Acid deposition longitude, 44/ Allegheny Mountain, 28-36 Air pollutants, transport, 4 rain, 30 Air sampling—See Interstitial air sampling See also Deposition, Dry deposition, Wet Aldehydes, determination in atmospheric deposition samples, 299 Acid precipitation Allegheny Mountain susceptibility of Japanese soils, 271 acid deposition and atmospheric See also Acid rain chemistry, 28-36 Acid rain deposition budgets for sulfate and alternative research strategies, 6-8 nitrate, 33 formation pathway, 129 Allegheny Mountain study, 7 laboratory investigation, 317 Ammonia nitrogen oxide role, 304 effect on atmospheric acidity, 254 present knowledge, 4 incorporation into acid clusters, 320 A

3

χ

χ

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328

THE CHEMISTRY OF ACID RAIN

Ammonia-Continued laser absorption spectrometry, 282-284 Ammonia clusters, sulfur dioxide addition, 320-321 Ammonium ion, predictor of acetic and formic acids, 223 Anion chromatogram, rainwater sample, 163,164/ Anthropogenic emissions, source of organic acids, 51 Antimony, rainwater distribution, 208 Aqueous-phase oxidation pathway, acetic and formic acid formation, 223-225 Aqueous-phase reactions, clouds, 93-106 Aqueous solution, hydrogen peroxide formation, 122 Arrhenius form, rate constants, 137 Arsenic, rainwater distribution, 208 Atlantic Ocean, impact of North American emissions, 43-51 Atmosphere definition of chemical measurement, 290 impact of North American emissions, 51-52 sulfur compounds, 170 Atmospheric acidity, determinant, 254 Atmospheric chemistry, Allegheny Mountain, 28-36 Atmospheric gases absorption, 274 measurement by laser absorption spectrometry, 274-288 measurement requirements, 277-279 Atmospheric oxidants airborne determination, 298 See also Oxidants Atmospheric particles airborne collection, 290 experimental methods in Ohio River study, 67-69 See also Fine particles, Particles Atmospheric Sciences Research Center, 292

Β

Band-gap illumination, titanium dioxide, 126 Bed temperature, phenanthridine char oxidation in air, 313/ Benzo[a]pyrene, reactions during atmospheri transport, 52 Bermuda acid rain precursors from North America, 47-49 precipitation influence, 47 Big leaf model, application, 199 Boron deposition properties similar to sulfur dioxide, 74 mass balance calculations, 85

Boron-sulfur dioxide ratio, Ohio River Valley study, 74-75 Branching ratio calculation, 138-140 OH-dimethylsulflde reaction, 138

C Calcium deposition in Japan, 263,264/ source in Japan, 267 Calibration, laser absorption spectrometry, 277-279,280,282,284,288 Calvert committee, report, 5 Catalysts, hydrogen peroxide formation study, 123 Centrifugal rotor devices, particle removal from air, 290-292 Char nitrogen conversion to N O , 304, 313/ effect on conversion to N O ,312 enrichment, 309 Char oxidation, factors affecting nitrogen oxides production, 304-316 Chars elemental analyses, 306/ preparation in oxidation study, 305-306 sample size, effect on conversion to Ν Ο , 312 time required for 50% burnoff, 315/ See also Acridine char, Phenanthridine chars Chemical mass balance model fits to selected elements in Ohio River Valley, 72/ original form, 59 Chemical mass balances description of use, 84 fine particles, 71,80 Ohio River Valley, 71-73 Chemical measurement, definition, 290 Chemiluminescence light, intensity, 294 Chloride, deposition in Japan, 263 Chromium, enrichment factor values for urban summer rain, 218 Cloud chamber assessing uncertainties, 188 description, 184 diagram, 185/ mean values and standard deviations, 190-191/ operational procedures, 186 sources of experimental variability, 188-189 trace background impurities, 187/ Cloud chemistry, liquid water content influence, 193 χ

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Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ix002

INDEX Cloud droplet gas-aqueous reaction, 95/ mass transport kinetics, 98 reaction of sulfur species, 246 Cloud temperature, effect on sulfate-nitrate ratio in precipitation, 248/ Cloud water anion and cation balance, 186 collection by airborne sampling, 292 hydrocarbon levels, 186-188 hydrogen peroxide formation, 121 sampler, 291/ sulfur dioxide oxidation, 109-116 Clouds acid incorporation mechanisms, 94-96 aqueous-phase reactions, 93-106 collection of supercooled liquid water, 292 composition importance, 93 See also Liquid water clouds Coal, combustion emissions, source of sulfate, 51 Coal char oxidation, purity, 305 Coal-fired power plants collection of particles and acidic gases, 84-91 contribution to atmospheric particles, 71-73 experimental details in collection study, 85-86 gas-phase tracer, 6-7 primary and secondary emissions, 73 uniform vertical concentration, 75 Collection efficiency, ozone chemiluminescence instruments, 294 College Park, M D atmospheric particulate and gas-phase concentrations, 88/ elemental concentrations in air, 89/ Community Health and Environmental Surveillance System, 2-3 Concentration bias, effect of season, 240/ Concentration gradients, S(IV) and S(VI) in sulfur dioxide oxidation, 146-147 Control strategies, need for timely information, 5 Copper, enrichment factor values for urban summer rain, 218 Copper smelter, influence on Puget Sound rainwater, 210 Correlation coefficients acetate-inorganic ion pairings, 222/ formate-inorganic ion pairings, 222/ See also Linear correlation coefficients Criegee intermediates, role in organic ion formation in precipitation, 225 Crustal material, 211 Cyclones, particle removal from air, 290-292

D

Data management, daily vs. weekly sampling study, 232-233 Deep Creek Lake study, 7,62-65 Deposition Allegheny Mountain, 32/ atmospheric contaminants, 11 chemical components in Japanese study, 259 intersite variability, 18 measurement uncertainity, 25-27 sources, nitrate and sulfate at Allegheny Mountain, 35/ United States, 25 variability, 17-20 See also Acid deposition, Dry deposition, Wet deposition Deposition velocity, measurement, 197-199 Desert sand formation of hydrogen peroxide, 127,128/,129 photocatalytically active, 127 Detection limit formaldehyde by laser absorption spectrometry, 284 hydrogen peroxide by laser absorption spectrometry, 284 nitric oxide by laser absorption spectrometry, 279 nitrogen dioxide by laser absorption spectrometry, 280 ozone chemiluminescence instruments, 294 Diffusion dénuder tubes, nitric acid sampling, 297 Diffusion hybrid receptor model, description, 61 Dimethyldisulfide, reaction with O H radical, 174 Dimethylsulfide biomolecular rate constants for oxidation, 136/ oxidation, 133,134-137 Disproportionation, hydrogen peroxide, 127 Droplets generation, dynamic flow reactor, 143 size distribution in sulfur dioxide oxidation study, 145/ Dry deposition estimation, 12 measurements, 33-36,196,199-200 monitoring, comparison with wet deposition, 196-203 nitric acid, 36 understanding, 4 variability, 18 western United States, 17/ See also Acid deposition,Deposition

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THE CHEMISTRY OF ACID RAIN

Dynamic flow reactor design, 143 setup for sulfur dioxide oxidation study, 144/

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ix002

Ε

Eastern United States distribution of deposition, 11-12 See also United States Eddy correlation, description, 196-197 Eddy flux data, 197 submicron sulfate particles, 198/ Effective rate constant determination in OH-dimethylsulfide reaction, 134,136/, 138 temperature dependence for OH-dimethylsulfide reaction, 138 Elemental concentrations, urban summer rain, 215-216 Emission source, sulfur dioxide, 204-211 Emissions natural potential, 25 relationship to deposition measurements, 21 Enrichment factors calculation, 216 particle filters, 86 urban summer rain, 216-218 Ethylenediaminetetraacetate, suppressive effect on S(IV) oxidation, 161/ Eulerian diffusion equations, proper application, 61 Europe, sulfur from North American emissions, 53-54 Extinction coefficient, theoretical relationship, 186

F

Factor analysis, Ohio River Valley airborne particles, 69 Ferric ion, effect on S(IV) oxidation in rainwater, 169 Field measurements, in-cloud reactions, 105 Filterpack methods, modification, 199-200 Filters, effectiveness for air samples, 86-89 Fine particles chemical mass balances, 71 See also Atmospheric particles,Particles Flame photometric detector, sulfur dioxide determination, 298 Fluidized-bed combustion, NO_ formation, ;

Fluorescence, OH-dimethylsulfide reaction, 134 Fog, N(V) scavenging, 254 Fog deposition calculation, 252 experimental details in San Joaquin Valley study, 251 main route of pollutant removal, 250 Fog water acidity, determinant, 254 Formaldehyde aqueous-phase oxidation, 224/ effect on sulfur dioxide oxidation, 186-188 laser absorption spectrometry, 284-288 mixing ratios Glendora, C A , 286/ Raleigh, N C , 287/ Formate-acetate ratio, precipitation samples, 224-225 Formate ions, introduction into precipitation, 219-227 Formic acid atmospheric sources, 50-51 clear air observations, 224/ formation aerosol scavenging pathway, 223 aqueous-phase oxidation pathway, 223 gas-phase concentration, 221 homogeneous gas-phase production, 225 Fossil fuel, source of selenium, 50 Four Corners power plant plume study, 64-65 Free jet expansions, properties, 318-319 Fuel nitrogen, conversion to Ν Ο , 305 χ

G

Gallium, marker for coal-fired plants, 71-73 Gas-aqueous reaction, cloud droplet, 95/ Gas phase, mass transport model, 110 Gas-phase concentration acetic acid, 221 formic acid, 221 organic acids, 226/ Gas-phase kinetic cell, 171 Gas-phase mass transfer, rate expression, 113 Gases, reaction in a cloud droplet, 94 H

Halogens, urban summer rainfall, 213-218 Heavy metals, urban summer rainfall, 213-218 Henry's law coefficient, sulfur dioxide, 146 Homogeneous gas-phase production, acetic and formic acids, 225

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INDEX Hubbard Brook Experimental Forest, annual concentration trends, 22/ Hybrid receptor model, 6,58-65,73-80 application, 91/ comparison of data at two sites, 90-91 definition, 58,73 sulfur concentrations in Ohio River Valley, 78-79/ See also Receptor models Hydration, neutral acid clusters, 320 Hydrocarbons cloud water, 186-188 determination in atmospheric samples, 299 Hydrogen abstraction dimethylsulfide, 140 pathway of the OH-dimethylsulfide reaction, 134-137 Hydrogen ion, bias in wet deposition study, 238/ Hydrogen peroxide ambient air sampling apparatus, 300/ atmospheric production, 120 detection, 123,125/ disproportionation, 127 effect on sulfur dioxide accommodation coefficient, 111-113 Fenton-type reaction, 127 formation from aqueous solution, 122 from desert sand, 128/ from titanium dioxide, 126,128/ from zinc oxide, 124,125/ in situ generation, 121 laser absorption spectrometry, 284-287 major oxidant of S(IV), 142 mass accommodation coefficient, 105 measurement techniques, 298-299 mixing ratios Glendora, C A , 285/ Raleigh, N C , 286/ oxidant power, 120 oxidation of sulfur dioxide, 96-98 photocatalytic formation, 120-129 sulfur dioxide oxidation, 142-156 Hydrogen peroxide-sulfur reaction, mass transport limitation, 104 Hydrometers, division between solid and liquid phase, 247 Hydroxyl radicals, production, 171 I

In-cloud processes description, 183 importance, 93 present knowledge, 4 rate evaluations, 96-105 simulation facility, 183-193

Inductively coupled plasma mass spectroscopy rain samples, 215 results for a water standard, 215/ Industrialization, effect on sulfur and nitrogen oxides, 12 Infrared spectra products of dimethyldisulfide and O H radical reaction, 177/ products of methyl mercaptan and O H radical reaction, 173/ products of sulfur dioxide and O H radical reaction, 178/ Instrumental neutron activation analysis rain samples, 214 results for a water standard, 215/ Instrumentation, field studies of wet deposition processes, 289-300 Intensity, chemiluminescence light, 294 Interfacial mass transfer, importance, 109 Intersite correlations, precipitation concentrations, 20/ Interstitial air sampling, 290-292 Ion-pair formation, acid clusters, 319 Ionic acid clusters description, 322 See also Acid clusters Ionization, neutral acid clusters, 319 Iron, enrichment factor values for urban summer rain, 218 Isomers, H S O molecule, 179 s

J

Japan annual deposition, 260/ deposition of chemical components, 258-271 industrial areas, 258 oxidation rate of S(IV) in rainwater, 158-169 principal component analysis of selected locations, 268-269/

Κ

Kinetics, hydrogen peroxide-sulfur reaction, 98

L

Laboratory operations, daily vs. weekly sampling study, 231

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THE CHEMISTRY OF ACID RAIN

Laser absorption spectrometry, 282-284 description, 275-277 formaldehyde, 284-288 measurement, atmospheric gases, 274-288 nitric acid, 282 nitric oxide, 279-280 nitrogen dioxide, 280-281 schematic diagram, 278/ See also Tunable diode laser absorption spectrometry Lead Deep Creek Lake, 62-63 rainwater concentration in Washington State, 208 Limit of detection—See Detection limit Linear correlation coefficients species in Deep Creek Lake, 63/ See also Correlation coefficients Liquid water content cloud simulation chamber, 192/ dependence of rate constant in sulfur dioxide oxidation, 150/ dependence of sulfur oxidation, 148-151 dependence of transformation rate in sulfur dioxide oxidation, 147 equation, 147 influence on cloud chemistry, 193 measurement in cloud simulation chamber, 184 reproducibility using computer control, 189-193 Liquid water clouds medium for atmospheric chemical chemical reactions, 94 See also Clouds

M Magnesium, deposition in Japan, 263 Manganese, enrichment factor values for urban summer rain, 218 Manganous ion, effect on S(IV) oxidation in rainwater, 169 Marine precipitation data, interpretation, 43 Mass accommodation coefficient, definition, 94 Mass transport limitation hydrogen peroxide-sulfur reaction, 103/ in-cloud reactions, 101-104 influence on sulfur dioxide oxidation by hydrogen peroxide, 151-154 ozone-sulfur reaction, 103/ Matrix isolation, technique description, 171 Maxwell's equation, kinetic correction factor, 113-116 Metal oxides, photocatalytic properties, 121

Methanesulfonic acid absorption, 174 formation from OH-dimethylsulfide reaction, 140-141 S - O H stretch, 174 Method bias distribution for hydrogen ion and sulfate, 235/ effect of season, 239 Methyl mercaptan formation, 176 reaction with O H radicals, 172-174 Model studies, sulfur dioxide oxidation in cloud water, 113-116

Ν

National Oceanic and Atmospheric Administration, dry deposition trial network, 198/ Nernstian behavior, materials, 121 Neutral acid clusters acid-water adducts, 321-322 hydration, 320 ionization, 319 See also Acid clusters New England, sulfate origin, 6 Nitrate atmospheric derivation, 10 concentration effect of precipitation depth and precipitation type, 244-245 wintertime wet precipitation, 244-245 deposition during fog episodes, 254 deposition in Japan, 263,265/ source in Japan, 267 Nitrate-sulfate ratio, fog water, 254 Nitric acid acid clusters, 319 airborne filter measurements, 296/ association with coal burning, 52 determination in air, 294-297 dry deposition, 36 laser absorption spectrometry, 282 measurements at Raleigh, N C , 283/ mixing ratios Cold Creek, Ontario, 285/ State College, PA, 283/ pathways for atmospheric formation, 95/ reactivity with negative ions, 322 sampling by diffusion dénuder tubes, 297 solution decomposition, 320 uptake by gas-phase reactions, 105 Nitric oxide, laser absorption spectrometry, 279-280

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

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INDEX

333

Nitrogen eastward advection from North America, 41-43 released as N O for acridine char, 311/ released from cnar as function of carbon conversion in air, 310/, 311/ Nitrogen dioxide computer screen printouts for aircraft measurements, 278/ laser absorption spectrometry, 280-281 measurements California, 281/ Ontario, 281/ oxidants, 94-96 Nitrogen flux, function of latitude and longitude, 46/ Nitrogen oxides airborne collection, 292-297 conversion on Mo catalyst, 297 generation in laboratory, 174 production during char oxidation, 304-316 Nitrogen peroxide, aqueous-phase reactions, 105 Nitrogen species, scavenging by snowflakes, 242 North American emissions impact on Europe, 53-54 impact on the Atlantic Ocean, 43-51 impact on the atmosphere over the western Atlantic, 51-52 impact on the surface ocean, 52-53 North Atlantic, composition of the lower atmosphere, 49 NO , char oxidation source, 309 NO* detector, 295/,297/

Ohio River Valley study, experimental methods, 67-69 Organic acids, gas-phase concentrations, 226/ Organic anions, concentrations in precipitation, 219/ Organic compounds, determination in atmospheric samples, 299 Organic-inorganic ion relationships, Pearson product moments, 221-223 Organic peroxides, determination in atmospheric samples, 299 Outliers, daily vs. weekly sampling study, 232 Oxidants sulfur and nitrogen dioxides, 94-96 See also Atmospheric oxidants, 298 Oxidation acid production, 318 water, 122 Oxidation rates, carbon and nitrogen in chars, 306-309 Ozone accommodation coefficients, 104-105,109-116 chemiluminescence instruments, 292-294 decay in helium carrier gas, 112/ gas-phase measurement, 298 oxidation of sulfur dioxide in droplet, 115/ reaction with olefins, 225 Ozone-sulfur reaction, mass transport limitations, 104

Ρ

Ο Occult deposition, 11 O H , production from hydrogen peroxide, 134 OH-dimethylsulfide reaction dependence on temperature, 139/ mechanism, 137 mechanistic study under atmospheric conditions, 133-141 O H radicals gas-phase reaction with sulfur compounds, 170 real-time measurement, 4 Ohio River Valley chemical mass balances, 71-73 coal-fired power plants, 68/ distribution of emissions, 26/ elemental concentration patterns, 80 sulfur concentrations in air, 74-75 sulfur dioxide density versus distance, 77 trace elements on fine particles, 66

Particle filters, enrichment factors, 86 Particles collection from coal-fired power plants, 84-91 See also Atmospheric particles, Fine particles Peroxyacyl nitrates (PANs), gas-phase measurement, 298 Pesticides, transport via precipitation, 50 PH dependence of sulfur oxidation by hydrogen peroxide, 151 effect on S(IV) oxidation in rainwater, 159-161 effect on the ozone-sulfur reaction in clouds, 98 rainwater in Japan, 163 Phenanthridine, nitrogen contents, 305 Phenanthridine char nitrogen, retention as function of burnoff, 307/,308/

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334

THE CHEMISTRY OF ACID RAIN

Phenanthridine chars Rainwater carbon and nitrogen reactivities, 306-309 acid deposition fluxes, 30 gasification by oxygen, 315 composition compared with dew and fog, 30 See also Chars concentration and oxidation rate of Photocatalysis, semiconductors, 121-123 S(IV), 158-169 Pollutant deposition, radiation fog, 250-257 description in urban summer rain Pollution control, significant benefits, 11 study, 214 Polycyclic organic matter, reactions during elemental concentrations, 217/ atmospheric transport, 52 factors affecting composition, 211 Potassium, deposition in Japan, 263 ferric and manganous ions, 161 Precipitation geographical mapping, 208 chemical components in Japanese study, 259 ion chromatographic analysis, 165/ collection by airborne sampling, 292 pH during S(IV) oxidation, 163,166/ concentration scavenging ratios for sulfate and excess components, 43-47 nitrate, 32 United States and the world, 15/ source of sulfur and arsenic, 210-211 correlation between calcium and spatial variation of concentrations, 209/ sulfate concentrations in winter, 247 sulfate, 19/ effect of direction on nitrate and sulfate Rainwater chemistry, effect of sulfur levels, 245 dioxide, 204-211 Japan, 259-263 Rate constant measurement uncertainties, 17-18 Arrhenius form, 137 monthly deposition in Japan, 262/ dependence on hydrogen peroxide in sulfur organic acid origin, 51 dioxide oxidation, 152/, 153/, 158/ organic anion concentrations, 219/ hydrogen peroxide-sulfur reaction, 100/ sampling, weekly schedule, 229 sulfur dioxide oxidation in stratus Precipitation chemistry, trends, 21/ clouds, 154 Precipitation collectors, daily vs. weekly sulfur oxidation in the atmosphere, 134 sampling study, 231 Rate expression, gas-phase mass Precision, estimation for an instrument, 188 transfer, 113 Puget sound, meteorology, 204-205 Reactive organic chemical mass balance, 59 Pulsed-laser photolysis, apparatus Receptor models design, 135/ description, 60-61,90 See also Hybrid receptor model Regional Acid Deposition Model, description, 5 Regional-scale receptor modeling, elemental Q concentration patterns, 80 Research, acid rain, 2-8 Quality control procedures, daily vs. weekly sampling study, 231 S

R

Radiation fog pollutant deposition, 250-257 removal times and production rates, 256/ Radioactive tracer, 8 Rain chemistry, Allegheny Mountain study, 29-30 Rain properties, Allegheny Mountain, 31/ Rain samplers experimental uncertainties, 206,207/ location in urban summer rain study, 217/

S(IV) catalytic oxidation, 159 concentration and oxidation rate in rainwater, 158-169 detection limit by ion chromatography, 163 experimental conditions for oxidation in test solutions, 159 factors affecting oxidation rate, 158 linear decay in rainwater, 163,168/ oxidation measured in rainwater, 159,167/, 168/ prevention between sampling and analysis, 161 oxidation rate in fog, 257 oxidation rate with and without catalysts, 159,160/ ozone oxidation, 114/

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INDEX Sample collector, clouds, 293/ Samplers, weekly vs. daily, 230 Samples collection in Japanese deposition study, 259 handling in daily vs. weekly sampling study, 231 Sampling daily vs. weekly, 229-240 location in Japanese study, 260/ San Joaquin Valley deposition rates of major ions, 253/ deposition velocities, 255/ experimental details in fog deposition study, 251 fog, 250-251 nitrate-sulfate ratios, 255/ removal times and production rates in fog, 256/ Sargasso Sea budgets for trace elements, 53 flux of contaminant substances, 53 Scavenging ratios, sulfate and nitrate, 34/ Sea salt effect on acid precipitation, 49 effect on rainwater, 211 source of sodium, 263 source of sulfate, 263-267 Seattle, automotive source of Pb and N 0 , 208 Selenium Deep Creek Lake, 62 seasonal concentration in Ohio River Valley, 75-77 use in hybrid receptor models, 73-74 western Atlantic precipitation, 50 Semiconductor particles, valence band holes, 121 Semiconductors band-gap positions, 121 photocatalysis, 121-123 Site concentration bias, weekly sampling study, 237/ Site method bias, daily vs. weekly sampling study, 233-239 Smog, origin, 3 Snow airborne collection of particles, 292 sulfate concentrations, 245 sulfate scavenging, 246 sulfate-nitrate ratio, 242 Sodium, deposition in Japan, 263 Sodium chloride, reagent for sulfur dioxide oxidation, 113 Source-finding hybrid receptor model, multiple receptor use, 60-61 Source-receptor relationships, 21-25,27 3

Stacked-filter sampler atmospheric particle and gas-phase elements, 87/ schematic diagram, 87/ Statistical testing, daily vs. weekly sampling study, 233 Steady-state approximation, dimethylsulfide oxidation, 137 Stratus clouds, rate constants for sulfur dioxide oxidation, 154 Strontium, deposition in Japan, 263 Subcanopy model, 199 Subcontinental air pollution, 10-27 Sulfate atmospheric derivation, 10 bias in wet deposition study, 238/ concentration correlation with calcium, 16 trend in annual median values, 19/ wintertime wet precipitation, 245-247 deposition during fog episodes, 254 effect on soil chemistry, 271 hybrid receptor model use, 7-8 Japan, 263 deposition rate, eastern North America, 61-62 harmful to humans, 3 hybrid receptor model approach, 73 inhibition in cloud droplets, 220 monthly deposition in Japan, 266/ origin in New England, 6 predictor of acetic and formic acids, 223 rainwater concentration in Washington State, 208 source in Delaware precipitation, 51 See also Aerosol sulfate Sulfate-nitrate ratio, winter precipitation, 242 Sulfate Regional Experiment (SURE), results, 4,11-12 Sulfur concentration Deep Creek Lake, 62/ Ohio River Valley, 76/ urban summer rain, 215-216 deposition association with submicron particles, 202/ particulate and gaseous component, 203 dry and wet deposition rates, 201/,202/ eastward advection from North America, 41-43 enrichment factor values for urban summer rain, 218 hybrid receptor model use, 75,80 measurements in Deep Creek Lake, 64/

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ix002

336

THE CHEMISTRY OF ACID RAIN

Sulfur-Continued oxidation dependence of liquid water content, 148-151 influence of the proton concentration, 148 oxidation by ozone and hydrogen peroxide, 99/ rate constant for oxidation by hydrogen peroxide, 97/ rate constant for oxidation by ozone, 97/ transatlantic flux, 53-54 transport, 80 urban summer rainfall, 213-218 wet and dry deposition comparison, 200-203 Sulfur compounds chemical degradation, 170 gas-phase reaction with O H , 170-181 Sulfur dioxide absorptions, 176-179 accommodation coefficients, 113-116,154 addition to ammonia clusters, 321 airborne determination, 298 aqueous-phase oxidation, 96-98 complex with water, 176-180 conversion to sulfate, 73,246 effect on rainwater chemistry, 204-211 emission sources, 204-211 experimental details of oxidation study, 143 fog deposition, 257 formation from OH-dimethylsulfide reaction, 140-141 Henry's law coefficient, 146 initial reaction with O H radicals, 171 major product of atmospheric sulfur reactions, 180 oxidants, 94-96 oxidation by hydrogen peroxide in suspended droplets, 142-156 by ozone reactions, 116 effect of liquid water content, 189 ratio of S(IV) species, 146 produced during degradation of sulfur compounds, 170 rate of transformation to sulfate, 188 reaction with O H radical, 176-180 reduction, 2 removal via oxidation at various p H levels, 156/ source-receptor relationship, 24/ transformation to S(VI) in a multiphase system, 148 transport lifetimes, 74 vibrational frequency, 172,174 wet vs. dry deposition, 203 Sulfur flux, function of latitude and longitude, 45/

Sulfur-selenium ratios, 74-78 Sulfur trioxide, reaction with water clusters, 321 Sulfuric acid formation in humid atmospheres, 120 pathways for atmospheric formation, 95/ reactivity with negative ions, 322 Surrogate surfaces, used to measure deposition rates, 251 Suspended droplets, sulfur dioxide oxidation by hydrogen peroxide, 142-156

Τ Temperature effect on conversion of char nitrogen to Ν Ο , 309-312 effect on rate constant for OH-dimethylsulfide reaction, 136/ effect on sulfate concentrations in rain, 247 effect on sulfate-nitrate ratio, 246-247 rate constant dependence, 137,138 Titanium dioxide, band-gap illumination, 126 Trace elements budgets, Sargasso Sea, 53 concentrations, fine particles in the Ohio River Valley, 66,70/ importance in airborne particles, 67 linked to sources, 84 variations of atmospheric concentrations, 88/ Trace gas-aerosol transfer atmospheric resistance components, 199 biological resistances, 199 Trace gases dry deposition measurement, 196-197 transformation over the western Atlantic, 52 Trace metals concentrations in wet deposition, 49-50 recycling from the sea surface, 50 Tracer hybrid receptor model application to Deep Creek Lake study, 63-65 secondary sulfate from sulfur dioxide, 59-60 Transformation rate sulfur dioxide oxidation by hydrogen peroxide, 147 sulfur dioxide to sulfate, 188 sulfur oxidation, dependence on pH, 151 Trees, acid rain damage, 8 Triethanolamine, suppressive effect on S(IV) oxidation, 161/ Tunable diode laser absorption spectrometry applications, 274-288 See also Laser absorption spectrometry χ

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

337

INDEX

Publication Date: September 3, 1987 | doi: 10.1021/bk-1987-0349.ix002

U

Western Atlantic Ocean Experiment (WATOX) experimental setup, 39-41 fluxes and methods, 40/,44/ United States intensives, 42/ climatological conditions, 13-14/ members, 40 See also Eastern United States, Western purpose, 39 United States Western United States Urban summer rainfall distribution of deposition, 12-17 elemental concentrations, 216/ See also United States halogens, 213-218 Wet deposition heavy metals, 213-218 comparison of weekly and daily sampling sulfur, 213-218 results, 229-240 Utility Acid Precipitation Study comparison with dry deposition, 196-203 Program, 229 effect of North American emissions, 43 U V absorption-stop flow apparatus, measurement uncertainty, 17-18 description, 109-110,112/ trace metal concentrations, 49 wintertime, 242-248 See also Acid deposition, Deposition Wet deposition processes, instrumentation for field studies, 289-300 Wilcoxin test, advantage over /-test, 233 V Wind direction, effect on precipitation concentration of sulfate and nitrate, 246/ Validity, estimation for an instrument, 188 Winter precipitation Vanadium, enrichment factor values for urban concentrations during rain and snow summer rain, 218 periods, 245/ Vibrational frequencies concentrations of ions, 244/ products of the dimethyldisulfide and O H events separated by depth , 244/ radical reaction, 175/ nitrate and sulfate products of the methyl mercaptan and O H concentrations, 243-247 radical reaction, 172/ sulfate-nitrate ratio, 242 products of the sulfur dioxide and O H Wisconsin Acid Deposition Monitoring radical reaction, 176/ Network, 220 Visibility, degradation, 3 Wood burning, source of potassium enrichment, 52 X W X-ray fluorescence, factor analysis on observed elements in air, 69-71 Wallops Island study, gas-phase boron concentrations, 91 Washington State, map, 209/ Washout ratios, sulfate and nitrate, 33 Water oxidation of dissolved sulfur dioxide, 113 oxidation to hydrogen peroxide, 122 ozone accommodation coefficients, 111 sulfur dioxide accommodation coefficients, 111-113

Ζ

Zinc, enrichment factor values for urban summer rain, 218 Zinc oxide, formation of hydrogen peroxide, 124

In The Chemistry of Acid Rain; Johnson, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1987.