Organic Marine Geochemistry 9780841209657, 9780841211407, 0-8412-0965-0

Table of contents :
Title Page......Page 1
Half Title Page......Page 3
Copyright......Page 4
ACS Symposium Series......Page 5
FOREWORD......Page 6
PdftkEmptyString......Page 0
PREFACE......Page 7
Biomarkers......Page 8
Humic Substances......Page 9
Volatile Organic Substances......Page 11
Literature Cited......Page 12
2 Molecular Geochemical Indicators in Sediments......Page 16
Molecular Indicators in Sediments......Page 17
Distributions of Marker Compounds in Marine Sediments......Page 28
Conclusions......Page 34
Literature Cited......Page 36
3 Sedimentary Lipids and Polysaccharides As Indicators for Sources of Input, Microbial Activity, and Short-Term Diagenesis......Page 39
Results and Discussion......Page 42
Literature Cited......Page 66
4 Phenolic and Lignin Pyrolysis Products of Plants, Seston, and Sediment in a Georgia Estuary......Page 68
Methods......Page 69
Results and Discussion......Page 70
Summary......Page 79
Literature Cited......Page 80
5 Characterization of Particulate Organic Matter From Sediments in the Estuary of the Rhine and from Offshore Dump Sites of Dredging Spoils......Page 82
Experimental......Page 83
Results and Discussion......Page 85
Literature cited......Page 95
6 Origin of Organic Matter in North American Basin Cretaceous Black Shales......Page 97
Experimental Methods......Page 98
Results and Discussion......Page 100
Summary......Page 108
Literature Cited......Page 111
7 The Biogeochemistry of Chlorophyll......Page 113
Experimental......Page 114
Results and Discussion......Page 115
Literature Cited......Page 130
8 Structural Analysis of Aquatic Humic Substances by NMR Spectroscopy......Page 133
Solution versus solid state NMR......Page 134
13C-NMR......Page 135
Solution NMR......Page 140
Solid state NMR......Page 143
Conclusions......Page 145
Literature Cited......Page 146
9 Structural Interrelationships among Humic Substances in Marine and Estuarine Sediments As Delineated by Cross-Polarization/Magic Angle Spinning 13C NMR......Page 147
Methods......Page 148
Results......Page 150
Discussion......Page 159
CONCLUSIONS......Page 160
LITERATURE CITED......Page 161
10 Early Diagenesis of Organic Carbon in Sediments from the Peruvian Upwelling Zone......Page 163
Lipid Biomarkers......Page 164
NMR Studies of Sedimentary Organic Matter......Page 165
Experimental......Page 166
Results and Discussion......Page 168
Literature Cited......Page 176
11 The Biogeochemistry of Polychlorinated Biphenyls in the Acushnet River Estuary, Massachusetts......Page 178
Results and Discussion......Page 180
General Discussion......Page 198
Acknowledgments......Page 199
Literature Cited......Page 200
12 Polychlorinated Biphenyls and Hydrocarbons Distributions among Bound and Unbound Lipid Fractions of Estuarine Sediments......Page 202
Methods......Page 203
Sample Descriptions......Page 206
Results and Discussion......Page 207
Conclusions......Page 215
Literature Cited......Page 216
13 Fate of Carbonized Coal Hydrocarbons in a Highly Industrialized Estuary......Page 219
Methods and Materials......Page 220
Results......Page 222
Discussion and Conclusions......Page 230
Literature Cited......Page 232
14 Hydrocarbon Contamination from Coastal Development......Page 233
Methods......Page 234
Results and Discussion......Page 238
Conclusions......Page 248
Literature Cited......Page 249
15 Distribution of Trace Organics, Heavy Metals, and Conventional Pollutants in Lake Pontchartrain, Louisiana......Page 251
Sampling Sites......Page 252
Analytical Methods......Page 254
Discussion of Results......Page 255
Conclusions......Page 261
Acknowledgments......Page 273
Literature Cited......Page 274
16 Seasonal Cycles of Dissolved Methane in the Southeastern Bering Sea......Page 275
Methods......Page 276
Physical Setting......Page 277
Seasonal Distributions of Dissolved Methane......Page 279
Processes Controlling the Distribution of Methane......Page 285
Inter-Annual Variations of Dissolved Methane......Page 294
Acknowledgments......Page 297
Literature Cited......Page 298
17 Stable Hydrogen and Carbon Isotopic Compositions of Biogenic Methanes from Several Shallow Aquatic Environments......Page 300
Methods......Page 302
Model of Methane Formation......Page 304
Importance of Alternate Methanogenic Substrates......Page 305
Methane Oxidation......Page 306
Ancillary Data......Page 307
Atmospheric Methane Isotopic Composition......Page 311
Summary......Page 313
Literature Cited......Page 314
18 Polybromomethanes A Year-Round Study of Their Release to Seawater from Ascophyllum nodosum and Fucus vesiculosis......Page 317
METHODS......Page 318
RESULTS AND DISCUSSION......Page 319
Literature Cited......Page 325
19 Biogeochemical Cycling of Sulfur Thiols in Coastal Marine Sediments......Page 326
Experimental......Page 327
Results and Discussion......Page 328
Summary and Conclusions......Page 338
Literature Cited......Page 340
20 Speciation of Dissolved Sulfur in Salt Marshes by Polarographic Methods......Page 342
Experimental......Page 344
Results and Discussion......Page 347
Field Results......Page 352
Acknowledgments......Page 355
Literature Cited......Page 356
21 Chemical Speciation in High-Complexation Intensity Systems......Page 358
Trace Metal Complexation in Natural Systems......Page 360
Experimental Examination of Mixed Ligand Stability Constants......Page 363
Summary and Conclusions......Page 367
Literature Cited......Page 368
22 The Adsorption of Organomercury Compounds from Seawater onto Sedimentary Phases......Page 369
Results and Discussion......Page 375
Literature Cited......Page 380
23 Effects of Humic Substances on Plutonium Speciation in Marine Systems......Page 382
Results......Page 384
Discussion......Page 386
Literature Cited......Page 387
24 The Interaction of Trace Metal Radionuclides with Humic Substances......Page 389
Materials and Methods......Page 390
Results......Page 393
Discussion......Page 405
Conclusions......Page 409
Literature Cited......Page 410
Author Index......Page 413
A......Page 414
B......Page 415
C......Page 416
D......Page 417
G......Page 418
H......Page 419
L......Page 420
M......Page 421
P......Page 422
S......Page 424
T......Page 425
Z......Page 426

Citation preview

Organic Marine Geochemistry

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

ACS SYMPOSIUM SERIES 305

Organic Marine Geochemistry Mary L. Sohn, EDITOR Florida Institute of Technology

Developed from a symposium sponsored by the at the 189th Meeting of the American Chemical Society, Miami Beach, Florida, April 28-May 3, 1985

American Chemical Society, Washington, DC 1986

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

Library of Congress Cataloging-in-Publication Data Organic marine geochemistry. (ACS symposium series; 305) "Developed from a symposium sponsored by the Division of Geochemistry at the 189th Meeting of the American Chemical Society, Miami Beach, Florida, April 28-May 3, 1985." Includes bibliographies and index. 1. Organic geochemistry—Congresses. 2. Marine sediments—Congresses. 3. Estuarine sediments— Congresses. I. Sohn, Mary L., 1952. Society. Division of Geochemistry Chemical Society. Meeting (189th Fia.) IV. Series. QA516.5.07235 1986 551.46Ό83 86-3429 ISBN 0-8412-0965-0

Copyright © 1986 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 UNT IED STATES OF AMERC IA American Chemical Society, Library 1155 16th St., N.W. Washington, D.C. 20036 In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

ACS Symposium Series M . Joan Comstock, Series Editor Advisory Board Harvey W. Blanch University of California—Berkele

Donald E Moreland

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

W. D. Shults Oak Ridge National Laboratory

Martin L . Gorbaty Exxon Research and Engineering Co.

Geoffrey K. Smith Rohm & Haas Co.

Roland F. Hirsch U.S. Department of Energy

Charles S.Tuesday General Motors Research Laboratory

Rudolph J . Marcus Consultant, Computers & Chemistry Research

Douglas B. Walters National Institute of Environmental Health

Vincent D. McGinniss Battelle Columbus Laboratories

C . Grant Willson I B M Research Department

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

FOREWORD SYMPOSIUM SERIES

The ACS was founded in 1974 to provide a medium for publishing symposia quickly in book form. The format of the Serie

IN CHEMISTRY SERIE

ADVANCES

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 Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

PREFACE

BOTH ORGANIC AND INORGANIC AREAS

of water-column and sediment geochemistry have recently served as the focus of much research. This book deals with major advances in organic marine and estuarine geochemistry, as well as the effects of organic substances on the speciation and distribution of inorganic and organometallic substances. The organization of this book is such that it should prove useful not only as a collection of related research articles, but also as a reference and a text suitable for graduate and advanced undergraduate courses in organi marin geochemistry The authors of the chapter their respective areas of specialization. Basic geochemical topics such as structures are included as well as diagenesis of organic natural products. Also discussed are anthropogenic pollutant substances in the marine environment and the effect of diagenesis and cycling on the distribution and fate of both toxic and nontoxic substances. I hope the combination of review and application chapters has produced a book that will be useful to many people in diverse fields. Without the enthusiasm and cooperation of the exceptional authors and the encouragement of the former chairmen of the Geochemistry Division (F. Miknis, T. Weismann, and G. Helz), this book never would have materialized. In addition, I would like to thank my husband, Rolf, for assisting in the drafting of tables and figures and for helping with the organization of the book. I am also indebted to the Geochemistry Division for its support in sponsoring the symposium from which this book was developed and to The Petroleum Research Fund, administered by the American Chemical Society, for partial support of the symposium.

MARY L. SOHN Florida Institute of Technology Melbourne, FL 32901 May 14, 1985

ix

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

1 Organic Marine Geochemistry An Overview Mary L. Sohn Department of Chemistry, Florida Institute of Technology, Melbourne, F L 32901

The use of modern hyphenated methods such as GC-MS have proven invaluable to the task of assigning specific sources to specific organic compounds isolated from marine sediments, suspended particulate matter, interstitial water and seawater. Early chapters of this volume discuss the correlation of various classes of compounds isolate sediments with source bacteria, phytoplankton, zooplankton and nonbiological components such as anthropogenic input, petroleum seepage, and the weathering of "mineral" deposits. Biomarkers A biological marker (or "biomarker") may be defined as "a compound the structure of which can be interpreted in terms of a previous biological origin." Since the isolation and identification of metalloporphyrins in bitumens by Treibs (2) in the 1930's and their correlation with tetrapyrroles of chlorophylls, implying a biological origin for petroleum, an enormous amount of progress has been accomplished in this area of research. In order to be a useful biomarker, a compound must retain enough of its original structure to be identified as a modified version of the original biological parent compound. The retention of the carbon backbone of biologically generated alcohols, in alkanes isolated from sediments and petroleum fractions, includes the classic cases of pristane and phytane as diagenetic products of phytol (the alcohol which esterifies the carboylic acid group in chlorophyll-a) and 5 ,-cholestane from cholesterol. Other examples of the usefulness of alkanes as biomarkers include correlations of various n-alkanes to bacterial populations (3), and the association of C -steranes with marine versus nonmarine input (originally as C -sterols) (4). Another factor commonly used as a source indicator with respect to alkanes is the carbon number distribution. Briefly, n-alkane distributions with carbon number maxima in the 17-21 range (C -C ) originate largely from aquatic algal sources, while maxima characterized by higher carbon numbers are 30

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0097-6156/ 86/ 0305-0001 $06.00/ 0 © 1986 American Chemical Society

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

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ORGANC I MARN IE GEOCHEMSITRY i n d i c a t i v e o f h i g h e r p l a n t i n p u t ( l e a f waxes o f t e r r e s t r i a l p l a n t s ) £l, 5 ) . I n a d d i t i o n , 2 3 ~ 3 3 n - a l k a n e s w i t h a p r e ­ dominance o f an odd number o f carbons t o an even number o f carbons (OEP) i s a l s o i n d i c a t i v e o f t e r r e s t r i a l h i g h e r p l a n t i n p u t (_1, 6-9) a l t h o u g h l o s s o f odd numbered carbon predominance can o c c u r w i t h m a t u r i t y ( 5 ) . Thus, a l t h o u g h p e t r o l e u m i s b e l i e v e d t o be o f b i o l o g i c a l o r i g i n , p e t r o l e u m i n p u t i s c h a r a c t e r i z e d by a l a c k o f odd t o even predominance (O.E.P. = 1.0). The i s o t o p i c c o m p o s i t i o n o f a l k a n e s and o f o t h e r c l a s s e s o f compounds can a l s o be used as a g e n e r a l s o u r c e i n p u t i n d i c a ­ t o r . I s o t o p i c f r a c t i o n a t i o n r e s u l t i n g from t h e m e t a b o l i c p a t h ­ ways i n v o l v e d i n t h e s y n t h e s i s o f b i o l o g i c a l l y produced compounds, when p r e s e r v e d i n a d i a g e n e t i c p r o d u c t , i s f r e q u e n t l y used t o d i f f e r e n t i a t e between t e r r e s t r i a l and a q u a t i c s o u r c e s . Hydrogen and carbon i s o t o p i c c o m p o s i t i o n s o f b i o g e n i c methanes from s h a l l o w a q u a t i c environments i s d i s c u s s e d i n a l a t e r c h a p t e r of t h i s volume (R. A. Burk l i t y o f carbon i s o t o p i M e s o z o i c sediments i s d i s c u s s e d by R.M. J o y c e and E. S. Van Vleet. Many o t h e r c l a s s e s o f l i p i d s b e s i d e s a l k a n e s have proven t o be v a l u a b l e b i o m a r k e r s , i n c l u d i n g f a t t y a c i d s , s t e r o l s , amino a c i d s , p o l y s a c c h a r i d e s , g l y c e r o l s , wax e s t e r s , p o r p h y r i n s and many i s o p r e n o i d s . The g r e a t e r t h e e x t e n t o f a l t e r a t i o n o f a compound by d i a g e n e t i c p r o c e s s e s , t h e h a r d e r i t i s t o c o r r e l a t e t h e p r o d u c t t o t h e b i o l o g i c a l p r e c u r s o r . However, t h e s u c c e s s i v e changes undergone by t h e p r e c u r s o r m o l e c u l e can sometimes be deduced from t h e s t r u c t u r e o f t h e p r o d u c t . I n t h e s e cases t h e "biomarker i s a l s o a g e o c h e m i c a l marker and may be r e f e r r e d t o as a b i o g e o c h e m i c a l i n d i c a t o r . F o r example, s t e n o l t o s t a n o l r a t i o s can be used as an i n d i c a t o r o f sediment o x i c i t y . High s t e n o l / s t a n o l r a t i o s are i n d i c a t i v e of o x i d i z i n g r a t h e r than r e d u c i n g environments ( 1 , 2 0 ) . P e r y l e n e p r o v i d e s an i n t e r e s t i n g example o f a PAH o f d i s p u t e d o r i g i n , w h i c h may prove t o be a r e l i a b l e i n d i c a t o r o f syn-and p o s t - d e p o s i t i o n a l a n o x i a when p r e s e n t i n g r e a t e r t h a n t r a c e amounts ( 1 1 ) . I n d i c a t o r s o f t h e b i o g e o c h e m i s t r y o f c h l o r o p h y l l and t h e temperature dependence o f c h l o r o p h y l l d i a g e n e s i s i s r e v i e w e d i n t h e c h a p t e r by J.W. Louda and E. W. Baker. Other c h a p t e r s i n t h i s volume concerned w i t h s o u r c e i n p u t markers and g e o c h e m i c a l i n d i c a t o r s i n c l u d e t h o s e by S.C. B r a s s e l l and G. E g l i n t o n , J.W. de Leeuw, J . Whelan e t a l . , J . J . Boon e t a l . , R.M. Joyce and E. S. Van V l e e t . C

C

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Humic Substances Compared t o t h e w e l l d e f i n e d s t r u c t u r e s and i n t e r r e l a t i o n s h i p s o f t h e d i s c r e t e m o l e c u l a r b i o m a r k e r s and g e o c h e m i c a l i n d i c a t o r s d i s c u s s e d above, r e l a t i v e l y l i t t l e i s known about marine humic s u b s t a n c e s . Whether t h e major s o u r c e o f i n p u t t o d i s s o l v e d and s e d i m e n t a r y marine humic s u b s t a n c e s i s o f t e r r i g e n o u s o r marine o r i g i n i s s t i l l o c c a s i o n a l l y debated i n t h e l i t e r a t u r e , a l t h o u g h most i n t e r p r e t a t i o n s p o i n t towards marine p l a n k t o n i c s o u r c e s ^ ( 1 2 - ^ ) , based most c o n v i n c i n g l y on i s o t o p i c r a t i o s , GC-MS, H and C NMR and i n f r a r e d s y ^ c t r a ( 1 5 - 1 7 ) . Stuermer e t a l (12) propose a c o m b i n a t i o n o f C and H/C r a t i o s as a

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

1.

SOHN

3 Organic Marine Geochemistry

s o u r c e i n p u t i n d i c a t o r o f t e r r e s t r i a l v e r s u s marine d e r i v e d humic substances. One o f t h e most u s e f u l t o o l s f o r d e t e r m i n i n g i n p u t s o u r c e s , f u n c t i o n a l group c o n t e n t and diagçnetic r e l a t i o n s h i p s between h u m ^ f r a c t i o n s has proven t o be C NMR. The e a r l y a p p l i c a t i o n s of C NMR t o humic s u b s t a n c e s were done by s o l u t i o n NMR and were t h u s l i m i t e d t o base s o l u b l e humic and f u l y ^ c a c i d s ( 1 6 , 18, 1 9 ) . The subsequent a p p l i c a t i o n o f s o l i d - s t a t e C NMR t o humic samples has a l l o w e d f o r d i r e c t comparisons between s o l u b l e and i n s o l u b l e f r a c t i o n s a s ^ e l l as between humic s u b s t a n c e s from d i v e r s e environments. C NMR a n a l y s i s o f s o l i d samples i s made p o s s i b l e by t h e u s e o f c r o s s p o l a r i z a t i o n and magic a n g l e s p i n n i n g (CP/MAS). C r o s s p o l a r i z a t i o n i s a s e n s i t i v i t y enhancing technique i n which t h e a p p l i c a t i o n o|^radio frequency p u l s e s a t t h e resonance f r e q u e n c i e s o f H and C establishes contact between t h e two p o p u l a t i o n s a l l o w i n g f o r ^ c r o s s p o l a n i z a t i o n ( i . e . p a n s i e r of magnetization C p o p u l a t i o n . Magi s e v e r a l kHz a t an a n g l e o f 54.7 r e l a t i v e t o t h e e x t e r n a l l y a p p l i e d magnetic f i e l d ) m i n i m i z e s l i n e b r o a d e n i n g due t o c h e m i c a l s h i f t a n i s o t r o p y (20-21) The c o m b i n a t i o n o f t h e s e t e c h n i q u e s w i t h h i g h power d e c o u p l i n g and f o u r i e r t r a n s f o r m a n a l y s i s has y i e l d e d h i g h r e s o l u t i o n s p e c t r a which can provide r e l i a b l e e s t i m a t e s o f v a r i o u s carbon t y p e s , ( 2 1 - 2 4 ) . The i m p o r t a n t q u e s t i o n o f t h e r e l i a b i l i t y o f q u a n t i f i c a t i o n of s o l i d s t a t e C NMR r e s u l t s can be answered i n p a r t by r e l a x a t i o n s t u d i e s and t h e measurement o f r e l a x a t i o n c o n s t a n t s (25-27) and i s d i s c u s s e d i n g r e a t e r d e t a i l by M.A. W i l s o n and A.H. G i l l a m i n a l a t e r c h a p t e r o f t h i s volume. Q u a n t i f i c a t i o n o f t h e a r o m a t i c c o n t e n t ( f ) o f marine humic and f u l v i c a c i d s by CP/MAS C NMR has demonstrated t h a t t h e s e s u b s t a n c e s have low a r o m a t i c i t i e s r e l a t i v e t o t e r r e s t r i a l c o u n t e r p a r t s ( 1 6 , 2 8 ) . The low a r o m a t i c ( h i g h a l i p h a t i c ) c o n t e n t o f marine humic s u b s t a n c e s i s a r e s u l t o f t h e i r i n s i t u p r o d u c t i o n . Higher p l a n t s a s s o c i a t e d w i t h t e r r e s t r i a l environments c o n t r i b u t e l i g n i n t o s o i l humic s u b s t a n c e s . The l a c k o f l i g n i n i n marine p l a n t s r e s u l t s i n a low a r o m a t i c i t y o f marine humic s u b s t a n c e s a l t h o u g h c o a s t a l sediments may c o n t a i n h i g h l e v e l s o f v a s c u l a r p l a n t r e s i d u e s ( 2 9 ) . L i g n i n i s an a r o m a t i c based n a t u r a l polymer c h a r a c t e r i z e d by methoxyl group s u b s t i t u t i o n s on t h e benezene r i n g s t r u c t u r e . These l i g n i n - a s s ^ c i a t e d methoxyl groups t y p i c a l l y produce a d i s t i n c t i v e C NMR peak w h i c h i s n o r m a l l y i n t e r p r e t e d as a s o u r c e marker f o r t e r r e s t r i a l i n p u t . However, as d i s c u s s e d i n t h e c h a p t e r by M.A. W i l s o n and A.H. G i l l a m , c o n t r i b u t i o n s from o t h e r carbon t y p e s ( p o s s i b l y amino a c i d carbon) may c o n t r i b u t e t o t h i s s i g n a l . The r e l a t i v e l y new t e c h n i q u e o f d i p o l a r dephasing i s c a p a b l e o f d i s t i n g u i s h i n g between t e r r e s t r i a l l i g n i n methoxyl s i g n a l s and o t h e r p r o t o n a t e d carbons w h i c h may r e s o n a t e i n t h e m e t h o x y l r e g i o n o f t h e spectrum. D i p o l a r dephasing t a k e s advantage o f d i f f e r e n t r e l a x a t i o n r a t e s o f v a r i o u s t y p e s o f carbon and u t i l i z e s t h i s phenomenon t o d i s t i n q u i s h between p r o t o n a t e d and n o n p r o t o n a t e d carbon ( 2 6 ) . The u t i l i z a t i o n o f d i p o l a r dephasing i n s t u d y i n g t h e d i a g e n e t i c changes undergone by o r g a n i c m a t t e r i n marine sediments i s d i s c u s s e d i n a c h a p t e r by W.T. Cooper e t a l . . &

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

4

ORGANC I MARN IE GEOCHEMSITRY Recent advances i n t h e s t r u c t u r a l i n t e r r e l a t i o n s h i p s among humic substances o f marine and e s t u a r i n e sedimentary o r i g i n i s d i s c u s s e d i n t h e c h a p t e r by P.G. Hatcher and W.H. Orem. O r g a n i c P o l l u t a n t s i n t h e M a r i n e Environment The b i o g e o c h e m i s t r y o f o r g a n i c p o l l u t a n t s i n marine systems i s o f enormous economic and e n v i r o n m e n t a l impact. The e n v i r o n m e n t a l b e h a v i o r o f p o l y c h l o r i n a t e d b i p h e n y l s ( P C B s ) has been s t u d i e d r a t h e r e x t e n s i v e l y because o f t h e i r d e t r i m e n t a l e f f e c t s on human h e a l t h and on l i v i n g marine r e s o u r c e s (30-32). As d i s c u s s e d i n t h e c h a p t e r s by J.W. F a r r i n g t o n e t a l . , due t o r e c e n t advances i n gas c a p i l l a r y chromotographic methods, i t i s now p o s s i b l e t o s t u d y t h e b i o g e o c h e m i s t r y o f i n d i v i d u a l PCB's r a t h e r t h a n t h a t o f combined i n d u s t r i a l m i x t u r e s o f PCB's (33-36). I n o r d e r t o r e a l i s t i c a l l y assess t h e r i s k s t o animal h e a l t h , i t i s important t o be a b l e t o work w i t h i n d i v i d u a l PCB l e v e l s r a t h e r t h a n w i t h u n r e s o l v e d m i x t u r e s becaus terms o f t o x i c i t y ( 3 7 ) The c o n t a m i n a t i o n o f c o a s t a l marine environments by a n t h r o p o g e n i c hydrocarbon i n p u t i s a l s o a m a t t e r o f u r g e n t concern w i t h r e s p e c t t o human h e a l t h and p r e s e r v a t i o n o f n a t u r a l r e s o u r c e s . Hydrocarbon c o n t a m i n a t i o n by o i l s p i l l s c a n o f t e n be t r a c e d t o s o u r c e s by f i n g e r p r i n t i n g t e c h n i q u e s . An e x c e l l e n t r e v i e w o f c u r r e n t developments i n t h i s f i e l d i s p r e s e n t e d by E.S. Van V l e e t ( 3 8 ) i n c l u d i n g d i s c u s s i o n s on computer i n t e r f a c e d t o t a l f l u o r e s c e n c e , t r a n s m i s s i o n i n f r a r e d s p e c t r o s c o p y , GC and GC-MS, t r a c e m e t a l a n a l y s i s e t c . . The c o r r e l a t i o n o f hydrocarbons w i t h p e t r o l e u m s o u r c e s i s f r e q u e n t l y h i n d e r e d by d i f f e r e n t i a l w e a t h e r i n g . F o r a d e t a i l e d d i s c u s s i o n on t h e w e a t h e r i n g o f p e t r o l e u m i n t h e marine environment, t h e r e a d e r i s r e f e r r e d t o a c u r r e n t l i t e r a t u r e r e v i e w ( 3 9 ) . I n t h i s volume, t h e f i n g e r p r i n t i n g o f hydrocarbon c o n t a m i n a t i o n from s p e c i f i c l a n d use a c t i v i t i e s , s u p p o r t e d by GC-MS a n a l y s i s o f p o l y n u c l e a r a r o m a t i c compounds (PNA) a r e d i s c u s s e d by R.H. P i e r c e e t a l . and by E.B. Overton e t a l . , w h i l e f i n g e r p r i n t i n g o f hydrocarbon c o n t a m i n a t i o n from c a r b o n i e d c o a l p r o d u c t s ( c r e o s o t e and c o a l t a r ) i s d e s c r i b e d by T.L. Wade e t a l . . f

V o l a t i l e Organic

Substances

The d e c o m p o s i t i o n o f complex o r g a n i c substances by m i c r o b i a l marine p o p u l a t i o n s r e s u l t s i n t h e i n s i t u p r o d u c t i o n o f b i o g e n i c methane, w h i c h i s found i n t r a c e amounts i n a l l f r e s h and s a l t w a t e r s . The r e l a t i v e importance o f a c e t a t e a s s i m i l a t i o n and CO^ r e d u c t i o n as p r i m a r y methanogenic pathways i s d i s c u s s e d i n t h e c h a p t e r by R.A. Burke and W.M. S a c k e ^ . I n t h e past, these pathways were s t u d i e d by t h e u s e o f C labelled substrates. However, t h e a u t h o r s demonstrate t h e advantages o f u s i n g s t a b l e hydrogen and carbon i s o t o p i c c o m p o s i t i o n s o f b i o g e n i c methanes t o e v a l u a t e t h e r e l a t i v e c o n t r i b u t i o n s from t h e s e two pathways. S e a s o n a l d i s t r i b u t i o n s o f methane a r e d i s c u s s e d i n t h e c h a p t e r by J.D. C l i n e e t a l . . V o l a t i l e h a l o g e n a t e d methanes a r e a l s o produced i n s i t u i n the marine environment and have been found t o be a s s o c i a t e d w i t h marine macroalge ( 4 0 ) . The r e l e a s e o f t h e s e h a l o g e n a t e d methanes

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

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SOHN

5 Organic Marine Geochemistry

i n t o c o a s t a l seawater has a l s o been demonstrated (41-43) and i s of e n v i r o n m e n t a l c o n c e r n . A s e a s o n a l s t u d y o f t h e r e l e a s e o f polybromomethanes i s d e s c r i b e d i n t h e c h a p t e r by P.M. Gschwend and J.K. MacFarlane. Organic - Inorganic I n t e r a c t i o n s The major i n f l u e n c e o f o r g a n i c marine s u b s t a n c e s on t h e p a r t i t i o n i n g and s p e c i a t i o n o f i n o r g a n i c and o r g a n o m e t a l l i c s u b s t a n c e s i s d i s c u s s e d i n t h e c l o s i n g c h a p t e r s o f t h i s volume. C o m p l e x a t i o n , a d s o r p t i o n and/or r e d u c t i o n o f i o n s and compounds by o r g a n i c m a t t e r i n marine and b r a c k i s h systems g r e a t l y a f f e c t t h e c y c l i n g and b i o a v a i l a b i l i t y o f many p o t e n t i a l n u t r i e n t s and t o x i c substances. The c o m p l e x a t i o n of m e t a l i o n s by humic s u b s t a n c e s i s a w e l l documented phenomenon (44-51). Due t o t h e u b i q u i t o u s n a t u r e o f these n a t u r a l l y occurrin important r o l e i n determinin o t h e r s u b s t a n c e s i n b o t h t e r r e s t r i a l and a q u a t i c environments (52-56). I n o r d e r t o p r e d i c t o r model t h e p a r t i t i o n i n g o f a p a r t i c u l a r m e t a l i o n i n a g i v e n environment, i t i s e s s e n t i a l t o be a b l e t o e v a l u a t e t h e magnitude of t h e i n t e r a c t i o n between t h e p e r t i n e n t components o f t h e environment ( t h e s u b s t r a t e s ) and t h e m e t a l i o n . When d e a l i n g w i t h t h e v a r i o u s s o l i d phases w h i c h may be p r e s e n t , a d s o r p t i o n o f t h e i o n onto each phase ( c l a y , sand, s i l t , hydrous m e t a l o x i d e s , humus) can be s t u d i e d v i a t h e e v a l u a t i o n o f a d s o r p t i o n i s o t h e r m s ( 5 6 ) . I n t h e s o l u t i o n phase, c o m p l e x a t i o n i s an i m p o r t a n t p r o c e s s w h i c h competes w i t h i o n - p a i r f o r m a t i o n and subsequent p r e c i p i t a t i o n . The s t r e n g t h o f t h e c o m p l e x a t i o n r e a c t i o n can be measured by e v a l u a t i o n o f a c o n d i t i o n a l f o r m a t i o n c o n s t a n t . (57-59, 4 6 ) . A d s o r p t i o n o f d i s s o l v e d s u b s t a n c e s onto suspended m a t t e r i s a p r i m a r y p r o c e s s i n t h e removal o f d i s s o l v e d substance from t h e water column and subsequent c o n c e n t r a t i o n i n sediments. The major r o l e p l a y e d by adsorbed o r g a n i c c o a t i n g s on p a r t i c u l a t e m a t t e r i s w e l l known (60, 6 1 ) . The p r o c e s s e s o f c o m p l e x a t i o n and a d s o r p t i o n i n marine systems and t h e i r e f f e c t s on t h e s p e c i a t i o n o f v a r i o u s i o n s and compounds a r e d i s c u s s e d i n t h e c l o s i n g chapters. Literature 1.

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Pierce, R.H.; Olney, C.E.; F e l b e c k , G.T. Geochim. Cosmochim. A c t a 1974, 38, 1061-1073. Ballschmiter, K.; Zell, M. F r e z e n i u s Z. A n a l . Chem. 1980, 302, 20-31. D u i n k e r , J.C.; Hillebrand, M.T.J. E n v i r o n . Sci. T e c h n o l . 1983, 17, 449-456 Mullin, M.D.; P o c h i n i , C.M.; M c C r i n d l e , S.; Romkes, M.; S a f e , S.H.; S a f e , L.M. E n v i r o n . Sci. T e c h n o l . 1984, 18, 468-476. D u i n k e r , J.C.; Hillebrand, M.T.J.; Boon, J.P. N e t h e r l a n d s J . Sea. Res. 1983, 17, 19-38. Kimbrough, R.D. "Halogenated B i p h e n y l s , T e r p h e n y l s , N a p h t h a l e n e s , D i b e n z o d i x i n s and R e l a t e d P r o d u c t s . Elsevier/North H o l l a n d B i o m e d i c a l P r e s s : New Y o r k , 1980, 406 pp. Van Vleet, E.S. Mar. Techn. Soc. J. 1984, 18, 11-23. Payne, J.R.; McNabb 18, 11-23. Hewson, W.D.; Hager, L.P. J. P h y c o l 1980, 16, 340. Gschwend, P.M.; M a c F a r l a n e , J.K.; Newman, K.A. S c i e n c e 1985, 227,1033. D r y s s e n , D.; F o g e l q u i s t , E. Oceanol. A c t a 1981, 4, 313. L o v e l o c k , J.E.; Maggs, R . J . ; Wade, R . J . N a t u r e 1973, 256, 193. Adhikari, M.; H a z r a , G.C. J . I n d i a n Chem. Soc. 1972, 49, 947-951. A r d a k a n i , M.; Stevenson, F . J . Soil Sci. Soc. Am. P r o c . 1972, 36, 884-890. Gamble, D.S.; S c h n i t z e r , M.; Hoffman, I. Can. J o u r n . Chem. 1970, 48, 3197-3204. Gamble, D.S. A n a l . Chem. 1980, 52, 1901-1908. M a n t o u r a , R.F.C.; Riley, J.P. A n a l y t . Chim. A c t a 1975, 78, 193-200. M a n t o u r a , R.F.C.; D i c k s o n , Α.; Riley, J.P. Est. C o a s t . Mar. Sci. 1978, 6, 387-408. Mills, G.L.; Hanosn, A.K. Jr.; Q u i n n , J.G.; Lammela, W.R.; Chasteen, N.D. Mar. Chem. 1982, 11, 355-377. Piotrowicz, S.R.; Harvey, G.R.; Boran, D.A.; W e i s e l , C.P.; S p r i n g e r - Y o u n g , M. Mar. Chem. 1984, 14, 333-346. Nissenbaum, Α.; Swaine, D.J. Geochim.Cosmochim. A c t a . 1976, 40, 809. R a s h i d , M.A.; Leonard, J.D. Chem. G e o l . 1973, 11, 89-97. T h e i s , T.L.; S i n g e r , P.C. I n "Trace M e t a l s and M e t a l - O r g a n i c I n t e r a c t i o n s in Natural Waters"; S i n g e r , P.C., Ed.; Ann A r b o r S c i e n c e Publishers, 1973. W a l l a c e , G.T. Mar. Chem. 1982, 11, 379-394. D a v i e s - C o l l e y , R . J . ; N e l s o n , P.O.; W i l l i a m s o n , K . J . E n v i r o n . Sci. T e c h n o l . 1984, 18, 491-499. Gamble, D.S.; S c h n i t z e r , M.; K e r n d o r f f , H. Geochim. Cosmochim. A c t a 1983, 47, 1311-1323. C l a r k , J.S.; T u r n e r , R.C. Soil Sci. 1969, 107, 8-11. Elgala, Α., El-Damaty, Α.; Abel-Latif, I . Z. Pflanz.Rodenk. 1976, 3, 293-300.

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8

60. Davis, J.A.; Leckie, J.O. Environ. Sci. Technol. 1978, 12, 1309-1315. 61. Balistrieri, L.S.; Brewer, P.G.; Murray, J.W. Deep-Sea Res. 1981, 28A, 101-121. RECEIVED December 10, 1985

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

2 Molecular Geochemical Indicators in Sediments S. C. Brassell and G. Eglinton Organic Geochemistry Unit, School of Chemistry, University of Bristol, Bristol BS8 1TS, United Kingdom

Sediments from contemporary aquatic environments contain a diversity of compounds that provide an assessment of the sources of their organic matter. These components include lipids with structural features that are indicative of their biological origins. Thus, specific diterpenoids and triterpenoid contributions fro Similarly, among the numerous sterols recognised in sediments many are diagnostic of their algal origins, notably 4α-methylsterols derived from dinoflagellates. Several lipid types characterise contributions from bacteria; for example, acyclic isoprenoid alkanes arising from methanogens. Illustrative examples of such diagnostic lipid distributions show the possibilities for differentiating between sediments receiving allochthonous terrigenous organic matter and those dominated by autochthonous algal and bacterial contributions. Within the hydrocarbon distributions, by contrast, several features can denote non-biological sources of organic components, such as the weathering of ancient sediments, o i l seepage and o i l spillage. A further development in environmental assessment using molecular indicators stems from the recent recognition that the unsaturation of specific lipids contributed to sediments by cocco1ithophorid algae provide a measure of water temperatures. This paper concentrates on three aspects o f the application of molecular organic geochemistry to the interpretation of the biological origins of sedimentary organic matter and t h e u s e o f such information i n the evaluation of depositional environments. First, the basis

0097-6156/86/0305-0010$06.75/0 © 1986 American Chemical Society

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

2.

BRASSELL AND EGLN ITON

11 Molecular Geochemical Indicators

for the assignment of s p e c i f i c compounds as diagnostic markers for the contributions of particular biota to sediments i s c o n s i d e r e d and i l l u s t r a t i v e examples of such molecular indicators are given. Second, the sedimentary distributions of such components a r e d i s c u s s e d and the p o s s i b i l i t i e s for their use i n the q u a l i t a t i v e assessment of contributions from different biological sources to sediments i s addressed. T h i r d , one group of l i p i d s which occur w i d e l y i n marine sediments, namely long-chain (£37 to C ) alkenones, are considered i n terms of their potential to provide an assessment of oceanic water temperatures i n the shallow subsurface from the sedimentary molecular record. The s t a n d a r d m e t h o d o l o g y used i n i n v e s t i g a t i o n s of the organic constituents of sediments typically involves t h e i r e x t r a c t i o n , the or compound class an i d e n t i f i c a t i o n by g a s c h r o m a t o g r a p h y (gc) and c o m p u t e r i s e d gas chrornatography-ma ss s p e c t r o m e t r y (gc-ms). Details of such procedures are not given here, b u t c a n be f o u n d i n the references cited. Molecular

Indicators

in

Sediments

The development of molecular markers as indicators of biological contributions to sedimentary organic matter relies on t h e i n f o r m a t i o n from the l i p i d composition of appropriate organisms. Such information i s often scant. Therefore, existing data i s used to propose working hypotheses t h a t c a n be m o d i f i e d o r amended when additional information becomes available. The underlying rationale for this approach i s the tacit assumption that the biochemical pathways of lipid biosynthesis i n different organisms are not n e c e s s a r i l y uniform at the present time, nor have they been over geological history. Rather, i t seems that the lipid compositions of biota have been tailored throughout evolution t o meet t h e i r environmental needs. Hence, the d i s c r e p a n c i e s and s i m i l a r i t i e s between the lipids of different organisms c a n be u s e d to assess their generic relationships leading to chemotaχ onomy. Such chemotaxonomic description of organisms using l i p i d components relies on the information obtained from the analysis of both laboratory cultures and natural populations of individual species. The assignment of a given compound recognised i n sediments to a specific biological source i s based on s u c h c l a s s i f i c a t i o n s aided by information from environmental a n a l y s e s , such as the investigation of sediments thought to receive dominant inputs from a particular s p e c i e s or class of organism. Indeed, the v e r i f i c a t i o n of the b i o l o g i c a l source and significance of individual lipid components of geochemical interest i s often best served by studies designed to evaluate t h e i r o r i g i n s i n a chosen environment.

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

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ORGANC I MARN IE GEOCHEMSITRY

For some y e a r s i t has been h e l d t h a t d i n o f 1 a g e 1 l a te s are the biological source of the 4ol-methylsterols that occur, frequently as abundant components, in marine sediments (1.2.2^· a s s i g n m e n t s were i n i t i a l l y based on the widespread literature concerning 4o(-methylsterols in cultured dinof1age1 lates (£) and the abundance of these compounds in sediments known to receive major c o n t r i b u t i o n s from t h i s c l a s s of algae. The d i s t r i b u t i o n s of 4 e C - m e t h y l s t e r o l s , and a l s o 4o(-methylstanones, observed in the bottom sediments of P r i e s t Pot, a s m a l l lake i n the English Lake D i s t r i c t , were almost identical to those recognised in a bloom of the d i n o f l a g e l l a t e £Ϊ£ίΐΐίϋΐΐ1 i—EluiSLliii c o l l e c t e d f r o m t h e o v e r l y i n g w a t e r s ( 5 ) . This study demonstrated t h a t P j _ i° ™!li£!Lii t 4-me t h y l s t e r o i d s in Priest Pot sediments and, in more general terms, provided convincing evidence in support of the link between sedimentar presumed b i o l o g i c a l source S

u

c

n

P e

i s

t

h

e

s

o

u

r

c

e

o

f

n

e

O v e r a l l , there are c l e a r i n d i c a t i o n s that particular organic c o m p o n e n t s may be specific to s i n g l e or multiple biological sources or, alternatively, may be non-diagnostic of their biological origins. In simple terms an individual component, or the distribution of a specific compound class, may be representative of contributions to sedimentary lipids from either algal, terrigenous higher plant or bacterial sources. Not a l l components, however, can be p l a c e d i n t o one of these three classes; for example, some o c c u r in a l l three, some may only occur in animals, whereas the o r i g i n s of others are unknown. In a d d i t i o n t o c o n s i d e r a t i o n s of their ultimate biological origins individual compounds in sediments can be either unaltered biosynthetic products or, alternatively, derivatives formed by diagenetic / catagenetic processes, which retain structural elements that attest to their original biological source. Most biological marker compounds o c c u r r i n g in sediments can be considered as m a r k e r s o f one of the following five groups: (i) ηon-diagnostic components (i i ) algae ( i i i ) terrigenous higher plants (iv) bacteria (ν ) un k n o w n ' E x a m p l e s o f i n d i v i d u a l c o m p o n e n t s h e l d t o be repres­ entative of these five categories are shown in Figures 1-5. The majority are known lipid constituents of organisms, whereas others are either diagenetic products or of an as yet undefined origin. The compounds chosen provide an i l l u s t r a t i v e , rather than a comprehensive, indication of the range of structural types in each category. Most of them have been d i s c u s s e d elsewhere in a fuller review paper (6), together with other structurally similar examples. Also, the individual compounds and compound d i s t r i b u t i o n s biοsyηthe s i s e d by, and held to be diagnostic for, algal, terrigenous higher plant and 1

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

2.

BRASSELL AND EGLN ITON

13 Molecular Geochemical Indicators

bacterial inputs to recent sediments are published elsewhere (3^). Within categories ( i i ) , ( i i i )and ( i v ) i n d i v i d u a l m a r k e r c o m p o u n d s c a n be u n i q u e l y r e p r e s e n t a t i v e of a particular species, genus or class of organism. Alternatively, they c a n be n o n - s p e c i f i c components which occur widely i n d i f f e r e n t , but perhaps distantly related, families. Clearly, s i m i l a r i t i e s i n the l i p i d compositions of related species or genera may r e f l e c t their ancestral l i n k s , w h e r e a s d i f f e r e n c e s may s t e m f r o m t h e d i v e r g e n c e o f their biosynthetic pathways. Non-diagnostic biological markers. The components considered t o be n o n - d i a g n o s t i c i n d i c a t o r s (Figure 1) a r e likely to be those that play a fundamental role i n biosynthetic processes. For example, essential constituents of cell structures ( e . g . membranes) or similar physiologica to many d i f f e r e n t type ubiquitously. Hexadecanoic acid, f o r example, i s a typical c o n s t i t u e n t o f t h e membranes o f numerous l a n d and aquatic plants, animals and b a c t e r i a . I t may b e p r e s e n t in the form o f wax esters or t ri acy 1 g l ycer o l s but i s generally of l i t t l e value i n differentiating between contributions to sediments from i t s various sources. Similarly squalene i s the biosynthetic p r e c u r s o r o f many triterpenoids and, thus, occurs widely i n organisms. Cholesterol, like hexadecanoic acid, i s a constituent of the cell membranes of many different families of organisms, with the notable exception of bacteria. I t acts as a ' r i g i d i f i e r ' i n cell membranes. I t i s a prominant sterol o f many algae and land plants, and i s often the only sterol component of copepods. Tocopherols are held to play an important role i n ph ο t osyn t he t ic processes. Hence, they are abundant i n many photosynthetic organisms, including higher plants, algae and c y a n o b a c t e r i a ( 7 ) ,making them n o n - d i a g n o s t i c m a r k e r s of the sources of sedimentary organic matter. Algal indicators. Individual marker compounds indicative of sediment contributions from algae (Figure 2 ) may occur in both marine and l a c u s t r i n e environments, a l t h o u g h their source species w i l l differ. Indeed, botryococcene i s the only component shown which has y e t t o be recognised i n both environmental regimes. Carotenoids are perhaps the most s o u r c e s p e c i f i c l i p i d c o n s t i t u e n t s o f o r g a n i s m s . For example, diatoxanthin occurs only i n diatoms and can therefore be regarded as a highly specific marker f o r their contributions to sediments. I t s absence i n a sediment, however, cannot be t a k e n as e v i d e n c e f o r the l a c k o f d i a t o m c o n t r i b u t i o n s t o o r g a n i c m a t t e r , due t o i t s l a b i l i t y . Indeed, this l a b i l i t y makes carotenoids of l i m i t e d use as markers of the sources of organic matter i n most s e d i m e n t a r y environments, with the notably exception of relatively s h a l l o w water systems, such as p o s t - g l a c i a l lakes ( 8 ) . Recent work (2,5) has provided convincing

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

14

ORGANC I MARN IE GEOCHEMSITRY

Ο )H HEXADECANOIC ACID (PLANTS Sc ANIMALS)

(WIDESPREAD,

CHOLESTEROL EXCEPT FOR

BACTERIA)

o< -TOCOPHEROL ( PHOTOSYNTHETIC ORGANISMS) Figure 1. Compound structures, names and b i o l o g i c a l origins of examples of ηo n - d i a g n o s t i c indicators of the sources o f sedimentary organic matter.

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

2. BRASSELL AND EGLN ITON Molecular Geochemical Indicators

DIATOXANTHIN

(DIATOMS)

4-METHYLG0RG0STAN0L (DINOFLAGELLATES)

HEPTATRIACQNTA-15#22-DIEN-2-0NE

(COCCOLITHOPHORIDS)

BOTRYOCOCCENE

03

• CJ LO < Q)

—

3 Ό bO ·Η •Η ϋ b-, AL

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

3.

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Sedimentary Lipids and Polysaccharides

39

h e x a d e c y l e t h e r i n b o v i n e c a r d i a c muscle (11) i n d i c a t e s t h a t s t e r o l e t h e r s as such o c c u r i n n a t u r e . L o n g - c h a i n ketones as such a r e known to o c c u r i n p l a n t waxes ( 1 2 ) . I n p l a n t s they are b i o s y n t h e s i z e d v i a the c o r r e s p o n d i n g hydrocarbons and the d i s t r i b u t i o n p a t t e r n s o f t h e hydrocarbons and m i d - c h a i n ketones i n p l a n t s are t h e r e f o r e v e r y s i m i l a r and are c h a r a c t e r i z e d by a s t r o n g odd over even predominance. The m i d - c h a i n ketones p r e s e n t i n t h i s sediment e x t r a c t do not a t a l l r e f l e c t the h y d r o c a r b o n p a t t e r n and do have a s t r o n g even over odd predominance ( I I ) . 0

|M-N|

3.

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45

Sedimentary Lipids and Polysaccharides

4 - M e t h y l s t e r o i d s . A l t h o u g h 4 - m e t h y l s t a n o l s and 4-methylsteranes a r e known t o o c c u r i n r e c e n t and a n c i e n t sediments, f o r some time t h e i r o r i g i n was n o t v e r y w e l l understood (24,25). However, a f t e r t h e s t r u c t u r a l e l u c i d a t i o n o f t h e so c a l l e d " B l a c k Sea S t e r o l " as 4amethyl-5a(H)-A -23,24-dimethyl-cholesten-33-ol ( d i n o s t e r o l , XI) i n e x t r a c t s from t h e B l a c k Sea s a p r o p e l l a y e r ( U n i t I I ) an o r i g i n from d i n o f l a g e l l a t e s became obvious ( 2 ) . 22

R = H, CH ; R = H, CH3, C H x

XII

3

2

2

5

XI

XIII

Ever s i n c e , d i n o s t e r o l and many o t h e r 4 - m e t h y l s t e r o l s ( X I I ) , i n c l u d i n g 4 - m e t h y l s t e r o i d k e t o n e s , have been encountered i n many sediments (8,26,10). The l a r g e v a r i e t y o f 4 - m e t h y l s t e r o i d s encountered i n a B l a c k Sea U n i t I sediment and t h e i r modes o f o c c u r r e n c e v e r y s t r o n g l y s u p p o r t an o r i g i n from d i n o f l a g e l l a t e s due to the s t e a d i l y i n c r e a s i n g knowledge o f s t e r o i d s o c c u r r i n g i n many s p e c i e s o f d i n o f l a g e l l a t e s ( 8 , 2 7 ) . There a r e good reasons t o b e l i e v e t h a t t h e r a t i o o f d i n o s t e r o l t o g o r g o s t e r o l s ( X I I I ) , c a l c u l a t e d from sediment e x t r a c t s can i n f o r m us about the r e l a t i v e amount o f f r e e and s y m b i o t i c a l l y l i v i n g d i n o f l a g e l l a t e s i n t h e d e p o s i t i o n a l environment (28). Because d i a g e n e t i c a l pathways o f s t e r o i d s have been s t u d i e d t h o r o u g h l y (4_), i t c a n be concluded t h a t 4 - m e t h y l d i a s t e r e n e s and - s t e r a n e s p r e s e n t i n a n c i e n t sediments and o i l s r e p r e s e n t t h e g e o l o g i c a l f a t e o f these d i n o f l a g e l l a t e s t e r o l s . T h i s i s , u n f o r t u n a t e l y , one o f t h e few examples where we b e l i e v e t h a t we understand b o t h t h e o r i g i n and t h e f a t e o f a group o f sedimentary compounds. I n t h e above d i s c u s s e d examples we have d e a l t w i t h sedimentary o r g a n i c compounds which p r o b a b l y occur as such i n l i v i n g organisms. H e r e a f t e r s e v e r a l examples w i l l be d i s c u s s e d i n which i n f o r m a t i o n i s a l s o o b t a i n e d about d i a g e n e t i c pathways. P r i s t - l - e n e . A l t h o u g h p r i s t - 1 - e n e (XIV) does n o t o c c u r i n e x t r a c t s o f sediments, i t i s a major, sometimes the most abundant p y r o l y s i s p r o d u c t o f o r g a n i c m a t t e r i n immature sediments ( 2 9 ) .

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

ORGANIC MARINE GEOCHEMISTRY

46

Very r e c e n t l y i t was demonstrated t h a t t o c o p h e r o l m o i e t i e s i n kerogen are l i k e l y p r e c u r s o r s of p r i s t - l - e n e ( F i g u r e 7) ( 3 0 ) . T h i s i d e a was s u p p o r t e d by the f a c t t h a t t o c o p h e r o l s a r e w i d e l y d i s t r i b u t e d i n p h o t o s y n t h e t i c t i s s u e s and t h a t they a l s o o c c u r as such i n s e v e r a l r e c e n t sediments ( 3 1 ) . I t i s tempting t o conclude t h a t d u r i n g " n a t u r a l p y r o l y s i s " the g e n e r a t e d p r i s t e n e w i l l be t r a n s f o r m e d t o the w e l l known component, p r i s t a n e , i n a n c i e n t sediments and o i l s . T h i s example n i c e l y i l l u s t r a t e s t h a t we have t o be v e r y c a r e f u l when we conclude t h a t a c y c l i c i s o p r e n o i d hydrocarbons such as p r i s t a n e o r i g i n a t e from the c h l o r o p h y l l s i d e c h a i n , p h y t o l , based s o l e l y on structural similarities. L o l i o l i d e s and d i h y d r o a c t i n i d i o l i d e . A l t h o u g h l o l i o l i d e s as such o c c u r i n l i v i n g systems the r e c e n t l y d i s c o v e r e d sedimentary l o l i o l i d e s (XV, X V I , X V I I ) i s o l a t e d from Namibian S h e l f diatomaceous ooze a r e thought t o be compounds which have been g e n e r a t e d by v e r y e a r l y stage d i a g e n e t i c a of the water column ( 3 2 )

DlH-ACT.

IS0-L0L.

XV XVI The c o n v e r s i o n suggested i n F i g u r e furanoxides reported e a r l i e r (33). i n f o r m us about a p o s s i b l e o r i g i n , subsequent t r a n s f o r m a t i o n of these maturation.

LOL.

XVII 8 might proceed v i a the 5,8 A l t h o u g h the s t r u c t u r a l f e a t u r e s n o t h i n g can be s a i d about m o l e c u l e s upon i n c r e a s i n g

A - n o r - s t e r a n e s and De-A-steranes. D e - A - s t e r o i d ketones ( X V I I I ) , hydrocarbons (XIX) and A - n o r s t e r a n e s (XX) were shown t o be p r e s e n t i n e x t r a c t s from Cretaceous b l a c k s h a l e s i n the N o r t h C e n t r a l Apennines (34,35). The D e - A - s t e r o i d a l compounds a r e thought t o be i n d i c a t i v e o f a d i a g e n e t i c a l pathway as shown i n F i g u r e 9. A similar pathway has been suggested f o r 3 - o x y - t r i t e r p e n o i d s ( 3 6 ) . A l t h o u g h A - n o r - s t e r a n e s a r e not known t o o c c u r i n l i v i n g systems, some sponges can b i o s y n t h e s i z e 33-hydroxymethyl-A-norsteranes from d i e t a r y s t e r o l s (37). T h e r e f o r e i t i s t e m p t i n g t o suggest t h a t the A - n o r - s t e r a n e s o r i g i n a t e from c e r t a i n sponges and t h a t t h e i r e x i s t a n c e i n sediments i s the r e s u l t of a s p e c i f i c d i a g e n e t i c r o u t e ( F i g u r e 10).

XIX

XVIII

R=H, CH , C H 2

3

2

5

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

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Figure

Sedimentary Lipids and Polysaccharides

7. T o c o p h e r o l s as p r e c u r s o r s

F i g u r e 9.

f o r p r i s t e n e and p r i s t a n e

P o s s i b l e d i a g e n e t i c pathway f o r D e - A - s t e r o i d s .

F i g u r e 10. P o s s i b l e d i a g e n e t i c pathway f o r A-nor s t e r o i d a l hydrocarbons.

American Chemical Society Library 1155 16th St., N.W. In Organic Marine Geochemistry; Sohn, M.; Washington, D.C. 20038 ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

48

ORGANIC MARINE GEOCHEMISTRY

The above d i s c u s s e d l o l i o l i d e s , A - n o r - s t e r a n e s and De-A-steranes, a r e thought t o c a r r y i n f o r m a t i o n about p a r t i c u l a r d i a g e n e t i c pathways s i n c e i t i s assumed t h a t these compounds do not r e f l e c t compounds w h i c h , as s u c h , o c c u r i n l i v i n g b i o t a Once a c e r t a i n pathway i s proven, the p r e c u r s o r m o l e c u l e i n f o r m a t i o n about the b i o l o g i c a As mentioned i n the i n t r o d u c t i o n , the i n f o r m a t i o n c o n t e n t of sedimentary o r g a n i c compounds can a l s o be e x p r e s s e d by t h e i r mode o f o c c u r r e n c e . A g e n e r a l a n a l y t i c a l procedure was s e t up t o d i s c r i m i n a t e l i p i d s which can be e x t r a c t e d as s u c h , which are r e l e a s e d a f t e r subsequent base t r e a t m e n t , and those which are r e l e a s e d a f t e r subsequent a c i d treatment ( F i g u r e 11). Complex l i p i d s p r e s e n t i n the f i r s t e x t r a c t can be f u r t h e r s t u d i e d a f t e r s a p o n i f i c a t i o n . The f i n a l r e s i d u e can be i n v e s t i g a t e d by o t h e r c h e m i c a l d e g r a d a t i o n r e a c t i o n s o r by f l a s h p y r o l y s i s . E x t r a c t s o b t a i n e d a r e not f u r t h e r s e p a r a t e d but are d e r i v a t i z e d and a n a l y z e d by GC and GC-MS (38,39). S i n c e b a c t e r i a l c o n t r i b u t i o n s t o sediments a r e thought t o be much more i m p o r t a n t than o r i g i n a l l y expected i n the o r g a n i c geochemistry f i e l d (40), e x a c t l y the same procedure as s k e t c h e d above was a p p l i e d t o numerous b a c t e r i a and t o s e v e r a l r e c e n t sediments ( 4 1 ) . R e s u l t s a r e shown h e r e f o r the p h o t o s y n t h e t i c s u l p h u r b a c t e r i u m Rhodobacter s u l f i d o p h i l u s and f o r a M e d i t e r r a n e a n s a p r o p e l ( S 7 , 250,000 y r . ) . F i g u r e 12 shows the GC-traces of the d i r e c t l y e x t r a c t a b l e l i p i d s ( - F r e e - ) , the l i p i d s r e l e a s e d a f t e r base treatment o f the f i r s t r e s i d u e (-0H~-) and the l i p i d s a f t e r a c i d treatment of the second r e s i d u e (-H -). Major compounds i n b o t h the f r e e and 0 H ~ - f r a c t i o n s are the mono u n s a t u r a t e d and s a t u r a t e d C i e " and C i e - f a t t y a c i d s and p h y t o l . I n t h i s b a c t e r i u m t h e r e o b v i o u s l y i s not v e r y much d i f f e r e n c e between the f r e e and e s t e r i f i e d l i p i d s . The t h i r d GC-trace (-H -), however, shows a c o m p l e t e l y d i f f e r e n t p a t t e r n . The major components are 3-hydroxy f a t t y a c i d s r e p r e s e n t i n g a v e r y p a r t i c u l a r d i s t r i b u t i o n p a t t e r n ( C I I + . Q , ^20:1 10) i n b o t h samples and a s m a l l even o v e r odd predominance of the n-alkanes i s noted i n the gypsum sample. Extended Al7(21)

-hopenes a r e p r e s e n t i n the m a r l . The most abundant compounds i n the gypsum sample are 14α(Η),17α(H)- and 143(H),173(H)pregnanes and homopregnanes. F u r t h e r , a more or l e s s t y p i c a l p a t t e r n of α,3-norhopane, a,3-hopane and gammacerane i s p r e s e n t i n t h i s sample. S e v e r a l of these phenomena have been n o t i c e d b e f o r e (45) i n sediments w h i c h might have been d e p o s i t e d under h y p e r s a l i n e c o n d i t i o n s . Some f e a t u r e s were a l s o observed i n a r e c e n t Sabkha environment ( 3 9 ) . T a b l e Table I I . C h a r a c t e r i s t i c Sedimentary Environments Phenomena; - phytane >> p r i s t a n e (phythenes; d i p h y t a n y l e t h e r s ) - i s o p r e n o i d and o t h e r thiophenes and t h i o l a n e s ? - pregnanes and homopregnanes

ι ι - even-odd predominance n - a l k a n e s - norhopane/hopane/gammacerane d i s t r i b u t i o n *

c

30~ 35 c

1

—

17(21) hopenes ù C 3 0 - C 3 5 hopanes

Origin; h a l o p h y l i c (archae)bacteria; photosynthetic sulphur b a c t e r i a ; cyanobacteria; sulphate reducing b a c t e r i a ; d u n a l i e l l a . (sabkha's; lagoons; " S o l a r L a k e " , e v a p o r i t i c b a s i n s ) .

F u r t h e r work i s necessary to b e t t e r understand and a p p l y the obvious i n f o r m a t i o n p r e s e n t . For example, one wonders whether the h i g h p h y t a n e / p r i s t a n e r a t i o i s the r e s u l t of r e l a t i v e l y h i g h amounts of phytenes and/or d i p h y t a n y l e t h e r s p r e s e n t i n ( h a l o p h i l i c ) archaeb a c t e r i a and i s not a t a l l an i n d i c a t i o n f o r a n o x i c i t y (46,47). The i s o p r e n o i d thiophene compound shown i n F i g u r e 16 has been observed i n o t h e r sediments a l s o ( 4 8 ) . I n s p e c t i o n of the so c a l l e d a r o m a t i c h y d r o c a r b o n f r a c t i o n of the m a r l sample w i t h GC-FID, GC-FPD and GC-MS r e v e a l e d the abundant presence of t h i s compound. Moreover, t h i s f r a c t i o n i s composed, f o r the most p a r t , of o r g a n i c s u l p h u r compounds, as can be judged from the GC-trace shown i n F i g u r e 18. Other i s o p r e n o i d t h i o p h e n e s , s h o r t c h a i n and l o n g c h a i n benzo-

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

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Sedimentary Lipids and Polysaccharides

cholestane

300

275

250

Ph

225

200

Pr

175

150

F i g u r e 16. GC-trace of the h y d r o c a r b o n f r a c t i o n (non adduct) of the m a r l e x t r a c t of S a r s i n a sediment.

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986. J3

C M

F i g u r e 18. GC-trace o f the a r o m a t i c h y d r o c a r b o n f r a c t i o n o f t h e m a r l e x t r a c t o f S a r s i n a sediment.

C

ISOPRENOID THIOPHENES

A UNKNOWNS

BEN ZOT HIOPHENES

• •

3

Η

m g

χ

> 2 ζ m Ο m

Ο

Ο 73 Ο >

3.

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Sedimentary Lipids and Polysaccharides

57

thiophenes are a l s o major compounds i n t h i s f r a c t i o n . A t the moment we can o n l y s p e c u l a t e about the o r i g i n of t h e s e new o r g a n i c s u l p h u r compounds. I t was shown by comparison w i t h a s y n t h e s i z e d s t a n d a r d , t h a t one of these i s o p r e n o i d thiophenes o c c u r r e d as a s i n g l e s t e r e o ­ isomer i n a C a r i a c o Trench sediment sample ( 4 8 ) . T h e r e f o r e , we assume t h a t t h e s e compounds a r e formed d u r i n g the v e r y e a r l y stages of d i a g e n e s i s . Even a d i r e c t o r i g i n from organisms ( s u l p h u r r e d u c i n g o r o x i d i z i n g b a c t e r i a ) cannot be r u l e d out a t t h i s s t a g e . A f u r t h e r s e p a r a t i o n by column chromatography y i e l d e d v a r i o u s f r a c t i o n s of the S a r s i n a a r o m a t i c h y d r o c a r b o n f r a c t i o n . Homologous s e r i e s of n - a l k y l thiophenes w i t h p e c u l i a r d i s t r i b u t i o n p a t t e r n s were observed by mass - chromatography g e n e r a t e d a f t e r a n a l y s i s of a p a r t i c u l a r f r a c t i o n by GC-MS (see F i g u r e 19). The C i s u b s t i t u t e d na I k y 1 t h i o p h e n e s (m/z = 111) e x e m p l i f i e d an i d e n t i c a l p a t t e r n as the n-alkane p a t t e r n ; a c l e a r odd/even predominance and C29 as the major component. The C 2 ~ s u b s t i t u t e d n - a l k y l thiophenes (m/z = 125) showed s i m i l a r p a t t e r n s but i n t h i and C30 i s now the major the C 3 - and C ^ - s u b s t i t u t e d n - a l k y l thiophenes (m/z = 139 and 153 r e s p e c t i v e l y ) traces are observed. Although t h i s k i n d of d i s t r i b u t i o n p a t t e r n i n f o r m a t i o n i s v e r y c l e a r i n i t s e l f , the e x p l a n a t i o n has t o await f u r t h e r s t u d i e s . The c h a r a c t e r i s t i c p a t t e r n s i n d i c a t e , however, t h a t an o c c u r r e n c e of compounds p o s s e s s i n g l o n g c h a i n n - a l k y l thiophene m o i e t i e s i n l i v i n g b i o t a i s not u n l i k e l y . A n o t h e r s t r i k i n g d i s t r i b u t i o n p a t t e r n was observed f o r i s o m e r i c m i x t u r e s of n - a l k y l t h i o l a n e s observed i n a f r a c t i o n o f R o z e l P o i n t o i l . F i g u r e 20 shows the GC-FPD t r a c e of t h i s f r a c t i o n . E v e r y major peak c o n s i s t s o f numerous isomers ( d i f f e r e n t v a l u e s f o r η an m but per peak η + m = c o n s t a n t ) of these t h i o l a n e s . I t i s remarkable t o see t h a t the o v e r a l l d i s t r i b u t i o n p a t t e r n i s v e r y s i m i l a r t o f a t t y a c i d p a t t e r n s i n young sediments. T h i s might be a n o t h e r i n d i c a t i o n t h a t these t h i o l a n e s are e i t h e r formed d u r i n g e a r l y stages i n the d i a g e n e s i s o r t h a t they a r e p r e s e n t as such or i n a f u n c t i o n a l i z e d form i n organisms. The above mentioned o r g a n i c s u l p h u r compounds r e p r e s e n t new i n f o r m a t i o n but more work i s n e c e s s a r y t o t r a c e t h e i r o r i g i n . To summarize, i t can be s t a t e d t h a t a t t h i s moment our knowledge about the i n f o r m a t i o n c o n t e n t of sedimentary o r g a n i c compounds i s i n c r e a s i n g s t e a d i l y . However, much more work i s n e c e s s a r y t o b e t t e r u n d e r s t a n d the d i f f e r e n t ways by w h i c h the i n f o r m a t i o n c o n t e n t s are e x p r e s s e d b e f o r e a l l i n f o r m a t i o n can be used e f f i c i e n t l y t o r e c o n s t r u c t p a l e o - e n v i r o n m e n t s . To b e t t e r u n d e r s t a n d the i n f o r m a t i o n c a r r i e d by sedimentary o r g a n i c m o l e c u l e s we have t o tune our a n a l y t i c a l e x t r a c t i o n and i s o l a t i o n p r o c e d u r e s i n such a way t h a t modes of o c c u r r e n c e s of l i p i d s and t o t a l l i p i d p r o f i l e s are o p t i m a l l y expressed without l o s i n g s t r u c t u r a l i n f o r m a t i o n of i n d i v i d u a l compounds or compound c l a s s d i s t r i b u t i o n p a t t e r n s .

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

58

ORGANIC MARINE GEOCHEMISTRY

1200

1700

F i g u r e 19. Mass chromatograms showing t h e d i s t r i b u t i o n p a t t e r n s of s e v e r a l groups o f n - a l k y l t h i o p h e n e s p r e s e n t i n a S a r s i n a m a r l aromatic hydrocarbon f r a c t i o n .

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986. χ =18

C20-isopr.?

x=22

H

C m 2 m + 1 —ζ3~

F PD-Trace

c

H

n 2n+1

F i g u r e 20. GC-FPD-trace o f an a r o m a t i c h y d r o c a r b o n f r a c t i o n r e v e a l i n g the d i s t r i b u t i o n p a t t e r n s o f n - a l k y l t h i o l a n e s i n R o z e l Point o i l .

x=16

R O Z E L POINT OIL - T O L U E N E F R A C T I O N 4

•5"

D m r m m c

ORGANIC MARINE GEOCHEMISTRY

60

Literature Cited 1. Ourisson, G.; Albrecht, P.; Rohmer, M. Pure Appl. Chem. 1979, 51, 709-729. 2. Boon, J.J.; Rijpstra, W.I.C.; de Lange, F.; de Leeuw, J.W.; Yoshioka, M.; Shimizu, Y. Nature 1979, 227, No. 5692, 125-127. 3. de Leeuw, J.W.; van der Meer, F.W.; Rijpstra, W.I.C.; Schenck, P.A. In "Advances in Organic Geochemistry 1979"; Douglas, A.G.; Maxwell, J.R., Eds.; Pergamon Press, Oxford, 1980; p. 211. 4. Mackenzie, A.S.; Brassell, S.C.; Eglinton, G.; Maxwell, J.R. Science 1982, 217, 491-504. 5. Simoneit, B.R.T. Geochim. Cosmochim. Acta 1977, 41, 463. 6. ten Haven, H.L.; de Leeuw, J.W.; Schenck, P.A. Geochim. Cosmochim. Acta 1985, in press. 7. Cranwell, P.A. Org. Geochem. 1984, 7, 25-37. 8. de Leeuw, J.W.; Rijpstra, W.I.C.; Schenck, P.Α.; Volkman, J.K. Geochim. Cosmochim. 9. Boon J.J.; de Leeuw 10. Brassell, S.C. Ph.D. Thesis, Bristol University, Bristol, 1980. 11. Funasaki, J.; Gilbertson, J.R. J. Lipid Res. 1968, 9, 766-768. 12. Kolattukudy, P.E.; Croteau, R.; Buckner, J.S. In "Chemistry and Biochemistry of Natural Waxes"; Kolattukudy, P.E., Ed.; Elsevier; Amsterdam, Oxford, New York, 1976; p. 294. 13. de Leeuw, J.W.; Rijpstra, W.I.C.; Schenck, P.A. Geochim. Cosmochim. Acta 1981, 45, 2281-2285. 14. Smith, D.J. Ph.D. Thesis, Bristol University, Bristol, 1984. 15. Liefkens, W.; Boon, J.J.;de Leeuw, J.W. Neth. J. of Sea Res. 1979, 13(3/4), 479-486. 16. Chappe, B.; Michaelis, W.; Albrecht, P. In "Advances in Organic Geochemistry 1979"; Douglas, A.G.; Maxwell, J.R., Eds.; Pergamon Press, Oxford, 1980, p. 265. 17. Boon, J.J.; van der Meer, F.W.; Schuyl, P.J.W.; de Leeuw, J.W.; Schenck, P.A. Init. Rep. of the Deep Sea Drill. Proj. XL. 1978, 627-637. 18. Marlowe, I.T.; Brassell, S.C.; Eglinton, G.; Green, J.C. In "Advances in Organic Geochemistry 1983"; Schenck, P.Α.; de Leeuw, J.W.; Lijmbach, G.J.W., Eds.; Pergamon Press, Oxford, 1984, p. 135. 19. Volkman, J.K.; Eglinton, G.; Corner, E.D.S.; Sargent, J.R. In "Advances in Organic Geochemistry 1979"; Douglas, A.G.; Maxwell, J.R., Eds.; Pergamon Press, Oxford, 1980, p. 219. 20. Marlowe, I.T.; Green, J.C.; Neal, A.C.; Brassell, S.C.; Eglinton, G.; Course, P.A. Br. Phycol. J. 1984, 19, 203-216. 21. Klok, J.; Cox, H.C.; Baas, M.; Schuyl, P.J.W.; de Leeuw, J.W.; Schenck, P.A. Org. Geochem. 1984, 7, No. 1, 73-84. 22. Klok, J.; Cox, H.C.; Baas, M.; de Leeuw, J.W.; Schenck, P.A. Org. Geochem. 1984, 7, No. 2, 101-109. 23. Klok, J.; Baas, M.; Cox, H.C.; de Leeuw, J.W.; Rijpstra, W.I.C.; Schenck, P.A. In "Advances in Organic Geochemistry 1983"; Schenck, P.Α.; de Leeuw, J.W.; Lijmbach, G.J.W.; Eds.; Pergamon Press, Oxford, 1984, p. 265. 24. Mattern, G.; Albrecht, P.; Ourisson, G. Chem. Comm. 1970, 15701571. 25. Rubinstein, I.; Strausz, O.P. Geochim. Cosmochim. Acta 1979, 43, 1387-1392.

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

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26. Gagosian, R.B.; Smith, S. Nature 1979, 277, 287-289. 27. Kokke, W.C.M.C.; Fenical, W.; Djerassi, C. Phytochem. 1981, 20, 127-134. 28. Djerassi, C. Pure Appl. Chem. 1981, 53, 873-890. 29. Larter, S.R.; Solli, H . ; Douglas, A.G.; de Lange, F . ; de Leeuw, J.W. Nature 1979, 279, No. 5712, 405-408. 30. Goossens, H; de Leeuw, J.W.; Schenck, P.Α.; Brassell, S.C. Nature 1984, 312, No. 5993, 440-442. 31. Brassell, S.C.; Eglinton, G.; Maxwell, J.R. Biochem. Soc. Trans. 1983, 11, 575-586. 32. Klok, J.; Baas, M . ; Cox, H.C.; de Leeuw, J.W.; Schenck, P.A. Tetr. Hedr. Lett. 1984, 25, No. 48, 5577-5580. 33. Repeta, D . J . ; Gagosian R.B.; In "Advances in Organic Geochemistry 1981"; Bjorøy, M . , Ed.; John Wiley, Chichester, 1983; p. 380. 34. van Graas, G.; de Lange, F . ; de Leeuw, J.W.; Schenck, P.A. Nature 1982, 296, No. 5852, 59-61. 35. van Graas, G.; de Lange 1982, 299, No. 5882 36. Schmitter, J.M.; Arpino, P.J.; Guiochon, G. Geochim. Cosmochim. Acta 1981, 45, 1951-1955. 37. Bohlin, L.; Sjöstrand, U . ; Djerassi, C. JCS Perkin I 1981, 10231028. 38. Goossens, H . ; de Leeuw, J.W.; Rijpstra, W.I.C.; Meijburg, G . J . ; Schenck, P.A. Geochim. Cosmochim. Acta, submitted. 39. de Leeuw, J.W.; Sinninghe Damsté, J.S.; Klok, J.; Schenck, P.Α.; Boon, J.J. In "Hypersaline Ecosystems - The Gavish Sabkha"; Krumbein, W.E., Ed.; Springer, Heidelberg; 1985, p. 350. 40. Ourisson, G.; Albrecht, P . ; Rohmer, M. Scient. Amer. 1984, 251, 34-41. 41. Goossens, H . ; Rijpstra, W.I.C.; Düren, R.R.; de Leeuw, J.W.; Schenck, P.A. Org. Geochem. submitted. 42. Lechevalier, M.P. C r i t . Rev. Microbiol. 1977, 7, 109-210. 43. Galanos, C.; Lüderitz, O.; Rietschel, E.T.; Westphal, O. In "Biochemistry of Lipids II"; Goodwin, T.W., Ed.; University Park Press, Baltimore, 1977; V o l . 14, p. 239. 44. Rossignol-Strick, M . ; Nesteroff, W.; Olive, P.; Vergnaud-Grazzini, C. Nature 1982, 295, 105-110. 45. Sinninghe Damsté, J.S.; ten Haven, H . L . ; de Leeuw, J.W.; Schenck, P.A. Org. Geochem., submitted. 46. Didyk, B.M.; Simoneit, B.R.T.; Brassell, S.C.; Eglinton, G. Nature 1978, 272, 216-222. 47. Holzer, G.; Oro, J.; Tornabene, T.G. J. of Chromat. 1979, 186, 795-809. 48. Brassell, S.C.; Lewis, C.A.; de Leeuw, J.W.; de Lange, F . ; Sinninghe Damsté, J.S. Nature, submitted. RECEIVED September 23, 1985

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

4 Phenolic and Lignin Pyrolysis Products of Plants, Seston, and Sediment in a Georgia Estuary 1

1

2

Jean K. Whelan , Martha E. Tarafa , and Evelyn B. Sherr 1

Chemistry Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543 University of Georgia Marine Institute, Sapelo Island, GA 31327

2

Phenolic and lignin pyrolysis products measured i n plants, seston, and sediment i n a Georgia estuary together with isotopic data suggest that vascular plant material is present i n estuarine organic matter pools. The pyrolysis products together with isotopic patterns of this obtained from Spartina. The pyrolysis-GC-MS data also gave indications of changes i n distribution of methoxy phenolic compounds i n going from plant materials to soils and seston, which could be due to either degradation processes or to a change in source in seston and sediments. These phenolic and methoxyphenolic pyrolysis products have generally not been detected to date i n either surface or sub-surface deep ocean sediments from several areas of the world. The combination of isotopic data, together with lignin and higher plant pyrolysis products, appears to provide a useful method of determining plant sources of organic matter i n estuaries. Determining the plant origins of organic matter i n coastal waters and sediments is of interest to geochemists and to écologiste i n answering specific questions regarding the sources and fates of carbon in these systems. For Georgia salt marsh estuaries, the i n i t i a l view was that most of the organic carbon present in the suspended material (seston) i n the water column, as well as i n the marsh soils and estuarine sediment, and which supported the estuarine food web, was derived from production of the marsh cordgrass, Spartina alterniflora (1-2). This concept has had to be modified based on stable carbon isotope analysis (3-5). Although the d i s tinctive isotopic signature of Spartina Γ = -12 to -13 ° / ) is present in the salt marsh soils and marsh animals, there is l i t t l e isotopic evidence for significant amounts of Spartina-derived organic matter i n the seston and sediment of the open estuary. Instead, there appears to be a large background of 00

0097-6156/ 86/ 0305-0062S06.00/ 0 © 1986 American Chemical Society

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

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Phenolic and Lignin Pyrolysis Products 1 J

o r g a n i c carbon w i t h an i s o t o p i c c o m p o s i t i o n ( δ C o f -18 t o -24°/ ) depleted in compared to that of Spartina. S t a b l e carbon i s o t o p e a n a l y s i s a l o n e , however, cannot be used t o determine whether t h i s m a t e r i a l o r i g i n a t e s p r i m a r i l y from i n s i t u * phytoplankton production ( 6 C o f -20 t o -26°/ ) o r r e p r e s e n t s a m i x t u r e o f a l g a l carbon and S p a r t i n a d e t r i t u s w i t h t e r r e s t r i a l organic m a t t e r (

π

> Ζ

Ο Ο

WHELAN ET AL.

Phenolic and Lignin Pyrolysis Products

3 -

1

1 DSS

1Η

10 30 10 10 -

si

4 Η 30

-

RS

S-13 S--M

3

10 -

•I

I

:l

10 10

-Ι

S-12 S--I5 MCH

1 5 3

SS

5!

BR Sedg

1 3

1

10

1

•

1 "3

I

Η

WR

1

Spar I

CL

θ

C

D

Ε

F

6

H

I

J

F i g u r e 2. L e v e l s o f v a n i l l y l d e r i v a t i v e s i n p y r o l y s i s p r o d u c t s of G e o r g i a e s t u a r y samples. Sample code: R i v e r s e s t o n (>52 Pm) ( R S ) ; Doboy Sound s e s t o n ( >52 μπι) (DSS); sediment from open creekbed ( S - 1 3 ) ; sediment from t i d a l c r e e k (marsh c r e e k b a n k ) ( S - l l ) ; sediment from t i d a l c r e e k (marsh c r e e k bed) ( S - 1 2 ) ; sediment from open e s t u a r y (Doboy m u d f l a t ) ( S - 1 5 ) ; mixed c y p r e s s and hard-wood (MCH); swamp s o i l ( S S ) ; b l a c k r u s h (BR); sedge ( s e d g ) ; w i l d r i c e (WR); and S p a r t i n a ( S p a r ) . See F i g u r e 1 f o r compound i d e n t i f i c a t i o n .

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

ORGANIC MARINE

GEOCHEMISTRY

RS

^

50H

DSS

0:

I

10H

L

1010S-15 10-

ζ:

10-

BLANK MCH

1030

"

ss"

F i g u r e 3. L e v e l s o f s y r i n g y l derivatives among pyrolysis p r o d u c t s from a G e o r g i a e s t u a r y . Same sample and compound codes as f o r F i g u r e s 1 and 2.

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

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69

Phenolic and Lignin Pyrolysis Products

RS DSS -

S-13

-

S--I2 S-i5

e

M C H ! :

F i g u r e 4. Levels p y r o l y s i s products F i g u r e s 1 and 2.

miscellaneous phenolic Same sample and compound

and methoxy codes as i n

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

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the carbon s k e l e t o n s o f methoxy-phenolic p y r o l y s i s products are n o t d r a s t i c a l l y d i f f e r e n t from t h o s e found i n t h e p a r e n t l i g n i n (15-16, 18-19) and t h a t s t r u c t u r e s o f l i g n i n p y r o l y s i s p r o d u c t s r e p o r t e d h e r e a r e p r o b a b l y t h e same as t h o s e p r e v i o u s l y r e p o r t e d (11, 14). I n a d d i t i o n , two o f the samples a n a l y z e d i n t h i s work a r e a l s o b e i n g a n a l y z e d by p y r o l y s i s GCMS i n t h e l a b o r a t o r y o f Dr. Jap Boon i n the N e t h e r l a n d s w h i c h w i l l a l l o w comparison o f our mass s p e c t r a w i t h those of a u t h e n t i c standards. Because the bonded phase c a p i l l a r y GC columns b e i n g used i n b o t h l a b o r a t o r i e s have the same l i q u i d phase ( J . Boon, p r i v a t e communication), i t was asumed i n t h e p r e s e n t work t h a t t h e r e l a t i v e o r d e r o f GC e l u t i o n o f i s o m e r i c p y r o l y s i s p r o d u c t s was t h e same as i n R e f . (11) and i n o t h e r work o f S a i z - J i m e n e z and de Leeuw ( u n p u b l i s h e d m a n u s c r i p t ) . The v a n i l l y l and s y r i n g y l p y r o l y s i s p r o d u c t s shown i n F i g u r e 1 a r e p r o b a b l y c o r r e c t , a l t h o u g h t h e s e s t r u c t u r e s w i l l have t o be checked by comparison t o a u t h e n t i c s t a n d a r d s i n f u t u r e work. The mass s p e c t a l computer gav t h a n 900 out o f a p o s s i b l on the I n c o s d a t a system) t o the s t r u c t u r e s shown i n F i g u r e 1 f o r compounds A-C, F, G, I , and M. The mass s p e c t r a f o r a l l o f t h e s e compounds a r e f a i r l y u n i q u e , as shown i n T a b l e I I . The computer i d e n t i f i e d compounds D, £ and H ( w h i c h p o s s e s s e d almost i d e n t i c a l mass s p e c t r a ) as p r o p e n y l v a n i l l y l compounds. The proposed s t r u c ­ t u r e s shown i n F i g u r e 1 a r e based on the f a c t t h a t the p a r e n t l i g n i n c o n t a i n s o n l y s t r a i g h t ( r a t h e r than branched) C3 c h a i n s bonded t o t h e p h e n y l groups (18-19) and on t h e e x p e c t e d GC e l u t i o n o r d e r based on Réf. ( 1 1 ) . A f o u r t h compound, J i n F i g u r e 1, was a l s o i d e n t i f i e d by the computer as p r o p e n y l benzene. I t i s p r o ­ posed t h a t t h i s compound c o n t a i n s a h y d r o x y l o r a l k o x y l group ( o r some o t h e r e a s i l y e l i m i n a t e d group) bonded t o a s t r a i g h t C3 s i d e c h a i n w h i c h i s e l i m i n a t e d d u r i n g e l e c t r o n impact f r a g m e n t a t i o n t o produce a mass spectrum v e r y s i m i l a r t o t h a t o f t h e c o r r e s p o n d i n g o l e f i n (20). S i m i l a r arguments a p p l y t o the p r o p e n y l s y r i n g y l compounds Κ and L. Compounds Τ and V were i d e n t i f i e d by the mass s p e c t a l com­ p u t e r as 3, 4-dimethoxyphenol and t r i m e t h o x y p h e n o l , r e s p e c t i v e l y . However, l i b r a r y s p e c t r a do n o t always c o n t a i n t h e c o r r e c t r e f e r ­ ence isomers ( 1 1 ) . I n a d d i t i o n , because p y r o l y s i s p r o d u c t s t r u c ­ t u r e s Τ and V i n F i g u r e 1 have been i d e n t i f i e d as abundant s y r i n g y l l i g n i n p y r o l y s i s p r o d u c t s ( 1 1 ) , and because i s o m e r s o f t e n g i v e v e r y s i m i l a r mass s p e c t r a ( 2 0 ) , we propose t h a t compounds Τ and V a r e actually the u n s u b s t i t u t e d and methyl syringyl derivatives, respectively. A number o f o t h e r p y r o l y s i s p r o d u c t s b e l i e v e d t o be e i t h e r phenols o r methoxyphenols d e r i v e d from h i g h e r p l a n t s were a l s o i d e n t i f i e d i n the sample s e t . I d e n t i f i c a t i o n o f t h e s e , i n c l u d i n g Ν t h r o u g h Ρ and S i n F i g u r e 4, a r e l e s s c e r t a i n t h a n t h o s e d i s ­ cussed above so t h a t s t r u c t u r e s a r e n o t proposed. Compounds Q l , Q2, and U, w h i c h produce v e r y s i m i l a r mass s p e c t r a and, t h e r e f o r e , a r e proposed t o be i s o m e r i c ( 2 0 ) , were i d e n t i f i e d w i t h a h i g h degree o f c o n f i d e n c e by t h e mass spec computer as t h e d i p h e n o l i c s t r u c t u r e shown i n F i g u r e 1. Compounds R l and R2, w h i c h a l s o appear t o be i s o m e r i c , gave mass s p e c t r a v e r y s i m i l a r ( b u t not

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

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i d e n t i c a l ) t o thymol shown i n F i g u r e 1. T h e r e f o r e , we propose t h a t t h e s e two compounds, w h i c h o c c u r r e d w i d e l y i n t h e sample s e t , a r e terpene d e r i v a t i v e s r e l a t e d t o thymol. Computerized GCMS d a t a o f o t h e r samples o b t a i n e d from more marine sediments have a l s o been examined f o r the p o s s i b l e presence o f l i g n i n - d e r i v e d p y r o l y s i s p r o d u c t s (Whelan, u n p u b l i s h e d d a t a ) . Three marine g o r g o n i a n ( c o r a l ) samples showed o n l y t r a c e s o f com­ pound w h i c h might be G and o f a d i a l k y l p h e n o l . M a r i n e copepods, two sediment samples from a sub-bottom d e p t h o f 788 m n e a r the Canary I s l a n d s , a sediment sample from a sub-bottom d e p t h o f 564 m i n the Japan Trench, and two s u r f a c e sediment samples from t h e P e r u u p w e l l i n g r e g i o n a l l showed no t r a c e s o f t h e p y r o l y s i s p r o d u c t s shown i n F i g u r e s 1-4 (determined by c a r e f u l s e a r c h e s o f mass chromatograms o f t h e masses shown i n T a b l e 1) w i t h t h e p o s s i b l e e x c e p t i o n of compound U. The f a c t t h a t t h e s e marine samples g e n e r a l l y do not produce t h e s e p h e n o l i c and methoxy p h e n o l i c compounds s u p p o r t s the non-marine, most p r o b a b l As shown i n F i g u r e 1, t h r e e g e n e r a l groups o f p h e n o l i c p y r o l y ­ s i s p r o d u c t s were found i n t h e samples a n a l y s e d : v a n i l l y l p h e n o l s , s y r i n g y l p h e n o l s , and m i s c e l l a n e o u s p h e n o l i c and methoxy compounds. The r e l a t i v e p r o p o r t i o n s o f t h e i n d i v i d u a l p r o d u c t s i n t h e v a r i o u s samples i n each o f the t h r e e groups a r e p r e s e n t e d r e s p e c t i v e l y i n F i g u r e s 2-4. The v a n i l l y l type o f p h e n o l i c s t r u c t u r e i s produced i n the l i g n i n o f a l l v a s c u l a r p l a n t s (18-19). L e v e l s o f v a n i l l y l p h e n o l i c p y r o l y s i s p r o d u c t s were h i g h i n the p l a n t s , swamp s o i l , and i n s e s t o n i n the Altamaha R i v e r and i n Doboy Sounds ( F i g u r e 2 ) . In t h r e e of the e s t u a r i n e sediment samples, however, t h e s e compounds were e i t h e r u n d e t e c t e d o r found i n o n l y t r a c e amounts ( F i g u r e 2 ) . The a c e t y l d e r i v a t i v e , A, was c o n c e n t r a t e d i n swamp s o i l , i n r i v e r and e s t u a r i n e s e s t o n , and i n t h e S p a r t i n a creekbank sediment (S-ll). We p o s t u l a t e t h a t the s e s t o n and sediment have a s i g n i f i ­ cant c o n t r i b u t i o n from swamp s o i l , o r more l i k e l y a l l o f t h e s e o r g a n i c p o o l s have a s i m i l a r p l a n t - d e r i v e d component w h i c h produces a h i g h e r p r o p o r t i o n o f t h e a c e t y l s t r u c t u r e upon p y r o l y s i s . The l a t t e r h y p o t h e s i s i s s u p p o r t e d by the presence o f the v a n i l l y l compound J i n s i g n i f i c a n t amounts o n l y i n S p a r t i n a and i n t h e S p a r t i n a marsh creekbank sediment ( S - l l ) . The low o r n o n - e x i s t e n t l e v e l s o f t h i s compound i n t h e o t h e r samples s u g g e s t s t h a t S p a r t i n a i s the major c o n t r i b u t o r o f h i g h e r p l a n t c a r b o n t o marsh creekbank sediment. However, i f t h i s h y p o t h e s i s i s c o r r e c t , i t i s d i f f i c u l t t o see why the s y r i n g l p r o d u c t s (K-M i n , F i g u r e 3) s h o u l d be p r e s e n t i n S p a r t i n a but m i s s i n g i n Sediment S - l l . F i v e s y r i n g y l d e r i v a t i v e s (compounds K-M, T, and V, F i g u r e 1) were d e t e c t e d among t h e p y r o l y s i s p r o d u c t s ( F i g u r e s 2-4). S y r i n g y l phenols a r e a l s o c h a r a c t e r i s t i c o f l l g n i n s , but o c c u r i n q u a n t i t y o n l y i n angiosperm p l a n t s C7; 18-19). S m a l l amounts o f t h r e e d i f f e r e n t a c e t y l and p r o p e n y l s y r i n g y l p y r o l y s i s p r o d u c t s were produced by w i l d r i c e and sedge ( F i g u r e 3 ) , w h i l e o n l y two o f t h e s e s t r u c t u r e s were o b t a i n e d from S p a r t i n a and the mixed c y p r e s s and hardwood t r e e l e a v e s . A much l a r g e r p r o p o r t i o n o f the a c e t y l d e r i v a t i v e , compound M, was found i n swamp s o i l and Doboy Sound

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s e s t o n , s u g g e s t i n g a common o r g a n i c source f o r t h e s e two p o o l s o f organic matter. Somewhat e l e v a t e d l e v e l s o f t h e s e t h r e e s y r i n g y l compounds o c c u r r e d i n r i v e r s e s t o n . The l o w e r p r o p o r t i o n o f com­ pound M t o L a s compared t o t h e Doboy Sound s e s t o n may I n d i c a t e a l e s s degraded o r a d i f f e r e n t p l a n t s o u r c e c o n t r i b u t i n g t o s e s t o n i n the r i v e r . The open e s t u a r y sediment samples, S-13 and S-15, had s y r i n g y l s t r u c t u r e s w h i c h p r o b a b l y came from p l a n t d e b r i s . I n c o n t r a s t , t h e creekbank s e d i m e n t , w h i c h had abundant v a n i l l y l s t r u c t u r e s , showed o n l y t h e u n s u b s t i t u t e d s y r i n g y l compound, T. The absence o f o t h e r s y r i n g y l s t r u c t u r e s i n sediment S - l l i s some­ what s u r p r i s i n g i f S p a r t i n a i s t h e main source o f p l a n t m a t e r i a l t o t h i s s e d i m e n t , s i n c e two a d d i t i o n a l s y r i n g y l s t r u c t u r e s ( L and M) were found among t h e S p a r t i n a p y r o l y s i s p r o d u c t s . F i g u r e 4 shows l e v e l s o f o t h e r phenoxy and methoxy p y r o l y s i s p r o d u c t s (N t h r o u g h S and U, some o f w h i c h a r e shown i n F i g u r e 1 ) w h i c h might be d e r i v e d from l i g n i n and/or o t h e r h i g h e r p l a n t material. The s p e c i f i c i t of higher plant m a t e r i a work. Q l and Q2 appear t o be a c e t y l d i p h e n o l i c s t r u c t u r e s , w h i l e b o t h R l and R2 were i d e n t i f i e d by t h e computer a s r e l a t e d t o t h y m o l (see F i g u r e 1 ) . B o t h t y p e s o f s t r u c t u r e s may be t y p i c a l o f h i g h e r p l a n t s , but a r e n o t n e c e s s a r i l y d e r i v e d from l i g n i n . Thymol ( R l and R2) i s a monoterpene w h i c h o c c u r s w i d e l y i n h i g h e r p l a n t s ( 2 1 ) . F o r t h e G e o r g i a e s t u a r y samples, t h e p l a n t s , swamp s o i l , s e s t o n , and sediment S - l l from t h e t i d a l creekbank a l l showed s i m i l a r d i s t r i b u t i o n s o f compounds Q2 and R l . Compound 0 a l s o o c c u r r e d as a p y r o l y s i s p r o d u c t i n t h e s e samples, w i t h t h e amount b e i n g more e n r i c h e d i n sedge t h a n i n t h e o t h e r p l a n t s . These com­ pounds a r e e i t h e r a b s e n t o r p r e s e n t i n l o w e r l e v e l s i n t h e s p e c t r a o f p y r o l y s i s p r o d u c t s from t h e o t h e r sediment samples: S-13, S-12 and S-15. The r e s u l t s a r e c o n s i s t e n t w i t h t h e v a n i l l y l product d i s t r i b u t i o n ( F i g u r e 2) and suggest t h a t t h e s e p y r o l y s i s p r o d u c t s a l s o a r i s e from v a s c u l a r p l a n t s and t h a t t h e r e i s a s i g n i f i c a n t v a s c u l a r p l a n t c o n t r i b u t i o n t o t h e s e s t o n and creekbank sediment. The s m a l l e r amounts o f compounds 0, Q2, and R l i n t h e open e s t u a r y sediments i n d i c a t e e i t h e r a l e s s e r i n f l u e n c e o r a more d i a g e n e t i c a l l y a l t e r e d higher p l a n t carbon. P y r o l y s i s p r o d u c t s N, R2, P, S, U, and V, shown i n F i g u r e 4, were more s p e c i f i c t h a n t h o s e d i s c u s s e d above. Compound V was produced o n l y by sedge, b l a c k r u s h , mixed c y p r e s s and hardwood l e a v e s , and i n s m a l l e r amounts, by swamp s o i l . The presence o f t h i s compound i n sediment S-15, b u t n o t i n o t h e r s e s t o n o r sediment samples, s u g g e s t s t h e c o n t r i b u t i o n o f s p e c i f i c h i g h e r p l a n t s t o t h i s sediment sample. The o c c u r r e n c e o f compound P, i n sediment S-15 and Doboy Sound s e s t o n , b u t n o t i n t h e h i g h e r p l a n t s a n a l y z e d o r i n swamp s o i l may i n d i c a t e a f a i r l y s p e c i f i c marine p r e c u r s o r f o r t h i s p a r t i c u l a r p y r o l y s i s product. I n a d d i t i o n t o t h e a n a l y s e s o f l i g n i n p r o d u c t s by PGCMS a s d i s c u s s e d h e r e , one sample o f e s t u a r i n e s e d i m e n t , comparable t o sample S-15, was a n a l y z e d f o r l i g n i n o x i d a t i o n p r o d u c t s by t h e CuO o x i d a t i o n method ( 2 2 ) . The d i s t r i b u t i o n o f v a r i o u s t y p e s o f p h e n o l i c compounds i n t h e sediment I s compared t o t h a t o f S p a r t i n a

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

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WHELANETAL.

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a l t e m i f l o r a and o t h e r t y p e s o f p l a n t s p r e v i o u s l y a n a l y z e d w i t h the CuO method (7) i n T a b l e I I I .

T a b l e I I I . Comparison o f t h r e e l i g n i n parameters d e t e r m i n e d f o r an e s t u a r i n e sediment sample w i t h t h o s e o f S p a r t i n a a l t e m i f l o r a and o t h e r v a s c u l a r p l a n t s . S/V wt. r a t i o o f s y r i n g y l t o v a n i l l y l p h e n o l s ; C/V wt. r a t i o o f c i n n a m y l t o v a n i l l y l p h e n o l s ; Co/Fe wt. r a t i o o f the c i n n a m y l p h e n o l s p-coumaric a c i d and f e r u l i c a c i d . m

s

β

Sample E s t u a r i n e sediment *Spartina a l t e m i f l o r a Other nonwoody angiosper Angiosperm woods Gymnosperm nonwoody t i s s u e Gymnosperm woods

S/V

C/V

Co/Fe

1.24 1.1

0.46 1.0

2.89 0.84

0.02 0

0.49 0

5.0 0

* p l a n t d a t a from Ref.

7.

The l i g n i n s i g n a t u r e i n t h i s sediment sample most c l o s e l y resembles t h a t o f nonwoody angiosperm t i s s u e , but i t does n o t f i t w e l l w i t h the s p e c i f i c d i s t r i b u t i o n o f l i g n i n phenols o b t a i n e d f o r S p a r t i n a . T h i s r e s u l t i s c o n s i s t e n t w i t h t h o s e o b t a i n e d by PGCMS, even though the s p e c i f i c r e l a t i o n between o x i d a t i v e and p y r o l y t i c l i g n i n d e g r a ­ d a t i o n p r o d u c t s has n o t y e t been d e t e r m i n e d . Thus, sediment S-15 does not show the same p y r o l y s i s p r o d u c t s as S p a r t i n a i n F i g u r e s 2-4. The s t r o n g e s t p h e n o l i c p y r o l y s i s s i g n a l i n S-15 i s most l i k e t h o s e o f swamp s o i l and Doboy Sound s e s t o n as shown i n F i g u r e 3 and c o n s i s t s o f a r e l a t i v e l y s t r o n g s y r i n g y l component i n c o m p a r i ­ son t o o t h e r sediment samples. S e v e r a l sediment samples from the M i s s i s s i p p i Fan i n the G u l f o f Mexico d i d show t r a c e s o f compound U. These sediments s h o u l d have been h e a v i l y i n f l u e n c e d by t e r r i g e n o u s o r g a n i c m a t t e r . How­ e v e r , i t i s not c u r r e n t l y known t o what depths l i g n i n s s u r v i v e i n deep sea sediments ( 6 ) . I t has r e c e n t l y been shown t h a t v a n i l l y l and p-hydroxy l i g n i n a r e p a r t i a l l y p r e s e r v e d i n some b u r i e d woods f o r p e r i o d s o f up t o 2500 y e a r s ( 2 3 ) . We p l a n t o r e a n a l y z e DSDP M i s s i s s i p p i Fan samples, a l o n g w i t h more h e m i p e l a g i c types of marine s e d i m e n t s , i n f u t u r e work t o l o o k i n d e t a i l f o r the com­ pounds i n F i g u r e 1. Summary D e t e r m i n i n g the r e l a t i v e c o n t r i b u t i o n s o f marine and t e r r e s t r i a l p l a n t o r g a n i c carbon t o t h e p o o l s o f o r g a n i c m a t t e r i n c o a s t a l systems i s o f t e n d i f f i c u l t . I n G e o r g i a s a l t marsh e s t u a r i e s , the major s o u r c e s o f o r g a n i c m a t t e r a r e i n s i t u p h y t o p l a n k t o n produc-

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t i o n , d e t r i t u s from t h e marsh g r a s s S p a r t i n a a l t e m i f l o r a , and t e r r e s t r i a l p l a n t m a t e r i a l i n t r o d u c e d by r i v e r f l o w . S t a b l e carbon i s o t o p e s t u d i e s i n d i c a t e t h a t , a l t h o u g h S p a r t i n a carbon i s p r e s e n t i n s a l t marsh sediment and t o some e x t e n t i n sediment i n t h e open e s t u a r y , t h e r e i s a l a r g e background of ^C-depleted organic m a t t e r i n sediment and i n suspended p a r t i c u l a t e m a t e r i a l w h i c h c o u l d come e i t h e r from p h y t o p l a n k t o n o r from t e r r e s t r i a l m a t e r i a l . I n o r d e r t o c l a r i f y t h e s o u r c e o f t h i s m a t e r i a l , samples o f e s t u a ­ r i n e v a s c u l a r p l a n t s , s e s t o n , and sediment were a n a l y s e d f o r con­ t e n t and c o m p o s i t i o n o f p h e n o l i c and methoxy p h e n o l i c p y r o l y s i s p r o d u c t s by p y r o l y s i s and subsequent gas chromatography and mass s p e c t r o m e t r y . Some o r a l l o f t h e s e p r o d u c t s ( p a r t i c u l a r l y t h e methoxy p h e n o l s ) a r e proposed t o be d i a g n o s t i c l i g n i n p y r o l y s i s products. These p r o d u c t s , w h i c h a r e n o t produced by more marine samples, appear t o be d i a g n o s t i c o f t e r r i g e n o u s p l a n t s . Based on t h e s e a n a l y s e s , S p a r t i n a has a unique s i g n a t u r e w h i c h a l s o appeared i n a sample o f s u r f a c e a S p a r t i n a marsh. Sedimen open e s t u a r i n e s i t e s showed v e r y l i t t l e o f t h e s e p y r o l y s i s p r o d u c t s , and t h e c o m p o s i t i o n d i d n o t match t h a t o f S p a r t i n a . Suspen­ ded m a t e r i a l i n t h e e s t u a r y had a s t r o n g e r s i g n a l w h i c h resembled t h a t o f t r e e l e a v e s and s o i l i n c o a s t a l f r e s h w a t e r swamps. S e s t o n and some sediment i n t h e open e s t u a r y a l s o c o n t a i n e d p h e n o l i c ( p r o b a b l y n o n - l i g n i n ) p y r o l y s i s p r o d u c t s w h i c h were n o t p r e s e n t i n the p l a n t s and w h i c h were p r o b a b l y o f marine o r i g i n . One e s t u a r i n e sediment sample was i n d e p e n d e n t l y a n a l y s e d f o r l i g n i n CuO o x i d a t i o n p r o d u c t s v i a gas chromatography. The c o m p o s i t i o n o f t h e l i g n i n p r e s e n t i n t h i s sample resembled t h a t o f some non-woody angiosperm t i s s u e s from t h e swamp, b u t d i d n o t c l o s e l y match t h e l i g n i n p r o d u c t s found f o r S p a r t i n a . I t appears t h a t o r g a n i c carbon d e r i v e d from v a s c u l a r p l a n t s i s p r e s e n t i n e s t u a r i n e s e s t o n and sediment, b u t S p a r t i n a may n o t be t h e p r i m a r y s o u r c e f o r t h i s material. Acknowledgments T h i s work was s u p p o r t e d by g r a n t s from t h e Sapelo I s l a n d R e s e a r c h F o u n d a t i o n t o E. S h e r r and by 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 OCE83-00485 t o J . K. Whelan and J . M. Hunt. We a r e g r a t e f u l t o Dr. John Hedges f o r l i g n i n o x i d a t i o n p r o d u c t a n a l y s i s o f one o f our sediment samples, and t o D r s . J i m A l b e r t s , Chuck Hopkinson, John E r t e l and John Hedges f o r t h e i r comments on t h e m a n u s c r i p t . Thanks a l s o go t o Dr. N e l s o n Frew f o r mass s p e c t r a and t o C h r i s t i n e B u r t o n and R i c h a r d Sawdo f o r t e c h n i c a l a s s i s t a n c e . C o n t r i b u t i o n No. 6055 o f t h e Woods Hole Océanographie I n s t i t u t i o n and No. 546 of t h e U n i v e r s i t y o f G e o r g i a M a r i n e I n s t i t u t e .

Literature Cited 1. 2.

Teal, J . M . , Ecology 1962, 43, 614-624. Odum, E. P.; De La Cruz, A. A. In "Estuaries"; Lauff, G. H . , Ed.; AMER. ASSOC. ADV. SCIENCE: Washington, D.C., 1967; pp. 383-388.

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

4. WHELAN ET AL. Phenolic and Lignin Pyrolysis Products

3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18 19. 20. 21. 22. 23.

Haines, Ε. B. Oikos, 1977, 19, 254-260. Haines, Ε. B . ; Montague, C. L. Ecology 1979, 60, 48-56. Sherr, Ε. B. Geochim. Cosmochim. Acta 1982, 46, 1227-1232. Hedges, J. I.; Mann, D.C. Geochim. Cosmochim. Acta 1979, 43, 1809-1818. Hedges, J. I.; Mann, D.C. Geochim. Cosmochim. Acta 1979, 43, 1803-1807. Hedges, J. I.; Parker, P.L. Geochim. Cosmochim. Acta 1976, 40, 1019-1029. Hedges, J. I.; Turin, H. J.; Ertel, J. R. Limnol. Oceanogr. 1984, 29, 35-45. Ertel, J. R.; Hedges, H. I. Geochim. Cosmochim. Acta 1984, 48, 2065-2074. Saiz-Jimenez, C.; de Leeuw, J. W. Org. Geochem. 1984, 6, 417-422. Bracewell, J. M.; Robertson, G. W.; Williams, B. L. J. Anal. Appl. Pyr. 1980, 2 Sigleo, A. C.; Hoering Acta 1982, 46, 1619-1626. Van de Meent, D.; DeLeeuw, J.W.; Schenek, P.A. J. Anal. Appl. Pyr. 1980, 2, 249-263. Obst, J. R. J. Wood Chem. Technol. 1983, 3, pp. 377-397. Martin, F . ; Saiz-Jimenez, C.; Gonsalez-Vila, F. J. Holzforschung 1979, 33, 210-212. Whelan, J. K . ; Fitzgerald, M. G.; Tarafa, M. Environ. S c i . Tech. 1983, 17, 292-298. Sarkanen, Κ. V. In "The Chemistry of Wood"; Browning, B. L., Ed.; R. E. Krieger Publishing Co.: Florida, 1963 (reprinted 1981); pp. 249-311. Sarkanen, Κ. V . ; Ludwig, C. H. "Lignins"; Wiley-Interscience: New York, 1981. Biemann, K. "Mass Spectrometry"; McGraw Hill: N.Y. 1962; pp. 87-95. Buchanan, M.A. In "The Chemistry of Wood", Browning, B. L., ed.; R. E. Krieger Publishing Co.: Florida, 1963; pp. 324-325. Hedges, J. I.; E r t e l , J. R. Anal. Chem. 1982, 54, 174-178. Hedges, J. I.; Cowie, G. L.; E r t e l , J. R.; Barbour, R. J.; Hatcher, P.G. Geochim. Cosmchim. Acta 1985, 49, 701-711.

RECEIVED October 31, 1985

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5 Characterization of Particulate Organic Matter From Sediments in the Estuary of the Rhine and from Offshore Dump Sites of Dredging Spoils 1

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Jaap J. Boon , B. Brandt-de Boer , Wim Genuit , Jan Dallinga , and E. Turkstra 1

FOM-Institute for Atomic and Molecular Physics, Kruislaan 407, 1098SJAmsterdam, The Netherlands D. B. W. RIZA, P.O. Box 17, Lelystad, The Netherlands

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Screening of estuarine and marine sediment samples by automated pyrolysis mass spectrometry combined with factor-discriminant analysi tion related to the geographical position and the sources of the organic matter. The mass spectral data give preliminary information about the organic matter composition. Analysis of the characteristic mass peaks m/z=86 and 100 by PMSMS and PGCMS points to bacterial polyalkanoates in the mud fraction of the river sediments. These and other pyrolysis products show that sewage sludge with degraded lignocellulose material and bacterial biomass is an important source of particulate organic matter in river sediment of this heavily populated area in the Netherlands. Extensive sedimentation of particulate matter from fluvial and marine origin takes place in the estuary of the Rhine, particularly in the harbors along the New Waterway, downstream from Rotterdam. Yearly about 20 million m^ of this mud is dredged and dumped into the North Sea (1). As these sediments have trapped organic and inorganic pollutants such as Cr, Cu, Hg, Cd, Pb, Zn and Ni, a considerable pollutant load is imposed on the North Sea ecosystem either directly by the outflowing river water or indirectly by dredging and dumping (2). Detailed knowledge on the molecular level about the fate of the riverine particulate organic matter and its associated pollutant cocktail is still limited. The complex processes which occur in the mixing area between fluvial and marine water in the estuary, result in sediments with characteristics of aquatic and marine origin, mixed up or maybe even reacted with each other in some ways. When these sediments are dredged and dumped offshore, the sedimentary material is exposed to open sea conditions with increased chances of resuspension and resedimentation and consequently a new diagenetic regime for the organic matter. In order to study aspects of the fate of these sediments, we have studied sedimentary particulate matter from sites in the estuary of the Rhine downstream from Rotterdam, from several dredging spoil dumpsites offshore (Loswal Noord), and from sediments of the Flemish 0097-6156/ 86/ 0305-0076$06.00/ 0 © 1986 American Chemical Society

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Banks i n t h e Southern N o r t h Sea. The o r g a n i c c o m p o s i t i o n o f t h e mud f r a c t i o n from t h e s e sediments was i n v e s t i g a t e d by C u r i e - p o i n t p y r o ­ l y s i s mass s p e c t r o m e t r i e t e c h n i q u e s , whereas m e t a l c o n t e n t , % o r g a n i c c a r b o n , carbon i s o t o p e s , c a r b o n a t e and mud c o n t e n t were determined s e ­ p a r a t e l y on the same sediments. A l t h o u g h t h e a n a l y s i s of e s t u a r i n e p a r t i c u l a t e s f o r t h e l a t t e r c h a r a c t e r i s t i c s i s w i d e l y known, the use­ f u l n e s s o f p y r o l y s i s methods f o r t h e c h a r a c t e r i z a t i o n of the o r g a n i c m a t t e r f r a c t i o n s has been demonstrated o n l y r e c e n t l y . The f a t e of sewage sludge i n t h e B o s t o n h a r b o r was t r a c e d w i t h t h e r m a l d i s t i l l a t i o n - p y r o l y s i s GCMS ( 3 ) . C o l l o i d a l m a t t e r i n Chesapeake Bay was c h a ­ r a c t e r i z e d by stepwise" p y r o l y s i s GCMS ( 4 ) . The f a t e o f o r g a n i c mate­ r i a l s and m e t a l s i n t h e r i v e r Rhine delïïâ and i n t h e I J s s e l m e e r was i n v e s t i g a t e d by C u r i e - p o i n t p y r o l y s i s mass s p e c t r o m e t r y and -GCMS ( 5 ) . P y r o l y s i s mass s p e c t r o m e t r y was used f o r the e v a l u a t i o n o f the o r g a n i c m a t t e r i n the e s t u a r i e s of the Ems (6) and G i r o n d e ( 7 ) . These s t u d i e s demonstrated a good c o r r e l a t i o n between PMS d a t a , c a r b o n i s o t o p e s and o t h e r v a r i a b l e s The p y r o l y s i s method f o r a g e n e r a l c h a r a c t e r i z a t i o n of the o r g a n i c m a t t e r from the s e d i ments. We d e s c r i b e here the r e s u l t s from s c r e e n i n g of e s t u a r i n e and open sea sediment samples by automated p y r o l y s i s low v o l t a g e mass s p e c t r o m e t r y combined w i t h f a c t o r - d i s c r i m i n a n t a n a l y s i s . C h a r a c t e r i s ­ t i c mass peaks r e s u l t i n g from t h i s procedure were i n v e s t i g a t e d i n more d e t a i l by p y r o l y s i s - t a n d e m mass s p e c t r o m e t r y and p y r o l y s i s p h o t o i o n i z a t i o n GCMS. Experimental Sampling and Sample P r e p a r a t i o n . Samples were c o l l e c t e d by a team from the N e t h e r l a n d s I n s t i t u t e f o r Sea Research ( T e x e l ) and R i j k s w a t e r s t a a t ( t h e M i n i s t r y o f T r a n s p o r t and P u b l i c Works) by a b o x c o r e r ( N o r t h Sea s t a t i o n s ) and Van Veen grab (Rhine s t a t i o n s ) . F i g u r e 1 shows a map w i t h the sample l o c a t i o n s ( f o r d e t a i l s , see ( 8 ) ) . S e d i ­ ment samples were t a k e n from t h e b o x c o r e r o r the grab and i m m e d i a t e l y a f t e r w a r d s resuspended i n f i l t e r e d (0.45 ym) sea o r r i v e r w a t e r ; the s u s p e n s i o n a f t e r s e t t l i n g o f the sand f r a c t i o n was passed over a 50 m i c r o n s i e v e t o a Whatman GFF f i l t e r w i t h a diameter o f 9 cm under g e n t l e s u c t i o n . A f t e r f i l t r a t i o n the f i l t e r e d p a r t i c u l a t e m a t t e r was washed w i t h d e s t i l l e d water t o remove sea s a l t s . The f i l t e r s w i t h t h e i r sediments were s t o r e d i n g l a s s p e t r i e d i s h e s and f r o z e n . Gene­ r a l l y f i v e b o x c o r e s (coded by l e t t e r ) were t a k e n i n one sampling a r e a (coded by number), whereas i n the Rhine e s t u a r y u s u a l l y t h r e e s e p a r a ­ te samples were grabbed i n d i f f e r e n t p a r t s of the r i v e r bed. Samples from the N o r t h Sea were t a k e n between 22 and 24 November 1983. Sam­ p l e s i n the New Waterway (Rhine e s t u a r y ) were t a k e n on 2 F e b r u a r y 1984. Samples f o r p y r o l y s i s a n a l y s i s were t a k e n f r o m the f i l t e r s and resuspended i n water immediately b e f o r e a n a l y s i s . A l i q u o t s of these s u s p e n s i o n s (about 50 micrograms of dry m a t t e r ) were t r a n s f e r r e d t o the f e r r o m a g n e t i c sample w i r e s and d r i e d i n vacuo. Samples were ana­ l y z e d immediately afterwards i n q u a d r u p l i c a t e . P y r o l y s i s Mass Spectrometry and M u l t i v a r i a n t Data A n a l y s i s . The au­ tomated p y r o l y s i s mass s p e c t r o m e t e r and the m u l t i v a r i a n t d a t a a n a l y ­ s i s by f a c t o r - d i s c r i m i n a n t a n a l y s i s ( f . d . a . ) procedure used have been

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

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F i g u r e 1. D i s c r i m i n a n t f u n c t i o n s c o r e map o f t h e p y r o l y s i s mass s p e c t r a of t h e sample s i t e s and t h e i r g e o g r a p h i c a l p o s i t i o n a l o n g the New Waterway (Rhine e s t u a r y ) and i n t h e N o r t h Sea. The numbers i n d i c a t e sampling a r e a s , t h e l e t t e r codes sample s i t e s w i t h i n an area.

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d e s c r i b e d r e c e n t l y ( 9 ) . The C u r i e - p o i n t temperature of the f e r r o m a g ­ n e t i c sample w i r e s was 510°C. P y r o l y s i s Tandem Mass S p e c t r o m e t r y , D e t a i l s of the i n s t r u m e n t have been d e s c r i b e d ( 1 0 ) . P y r o l y s i s c o n d i t i o n s were s i m i l a r t o t h o s e used f o r the PMS i n s t r u m e n t . The p y r o l y s a t e was i o n i z e d a t 70 eV and i o n s of i n t e r e s t were s e l e c t e d i n the f i r s t magnetic s e c t o r ( r e s o l u t i o n 500). These i o n s were d i s s o c i a t e d by c o l l i s i o n w i t h h e l i u m atoms (pres­ sure 0.9 P a ) , a c c e l e r a t e d a t 15 kV and a n a l y z e d i n a second magnetic s e c t o r . Ions were d e t e c t e d by s i m u l t a n e o u s i o n d e t e c t i o n u s i n g c h a n n e l p l a t e s , a phosphor s c r e e n and a diode a r r a y camera. T o t a l a n a l y s i s time f o r each i o n i s 8 s. P y r o l y s i s P h o t o i o n i z a t i o n GCMS. D e t a i l s of the i n s t r u m e n t have been d e s c r i b e d e a r l i e r ( 1 1 ) . C u r i e p o i n t p y r o l y s i s was performed i n n i t r o ­ gen which a l s o s e r v e d as the c a r r i e r gas. P y r o l y s i s o c c u r r e d d i r e c t l y i n f r o n t of the c a p i l l a r chamber of the mass s p e c t r o m e t e r w i t h C P - S i l 5-CB (I.D.=0.32 mm, f i l m t h i c k n e s s : 1 micron) was used f o r the s e p a r a t i o n . The oven was programmed from 80-260 C a f t e r a p e r i o d at room temperature d u r i n g p y r o l y s i s of the sample. Argon I resonance photons (11.6 and 11.8 eV) were used f o r i o n i z a t i o n of the GC e f ­ f l u e n t . I o n source temperature was 150°C, P r e s s u r e i n t h e i o n source was 10~2 T o r r and i n t h e vacuum chamber 10"^ T o r r . The quadrupole was scanned a t 1 scan/s over 30 t o 235 amu. R e s u l t s and D i s c u s s i o n Sampling P l a n and Sediment Workup. A number of c h o i c e s have been made i n d e s i g n o f the sampling program. Samples were t a k e n i n l a t e autumn and w i n t e r i n o r d e r t o m i n i m i z e c o n t r i b u t i o n s o f p h y t o p l a n k t o n to t h e bottom sediments. I t was not p o s s i b l e t o sample a l l m a t e r i a l s i n the same time frame. The open sea samples were t a k e n by b o x c o r i n g to m i n i m i z e l o s s o f s u r f a c e sediments d u r i n g s a m p l i n g . G e n e r a l l y the upper f i v e c e n t i m e t e r s were used f o r the i s o l a t i o n o f t h e f r a c t i o n s m a l l e r t h a n 50 m i c r o n s . Each sample a r e a i n F i g u r e 1 c o n s i s t e d of f i v e i n d i v i d u a l sample s i t e s which were s e p a r a t e d by s e v e r a l m i l e s . T h i s r e p l i c a t i o n was chosen f o r s t a t i s t i c a l reasons i n o r d e r t o e v a ­ l u a t e the r e p r o d u c i b i l i t y i n the c o m p o s i t i o n of the o r g a n i c m a t t e r of the sediments i n one a r e a . Samples i n t h e r i v e r were t a k e n on t h e l e f t s i d e , on the r i g h t s i d e and i n the m i d d l e o f the b e d d i n g f o r t h e same r e a s o n s . The s e p a r a t i o n o f mud and sand was n e c e s s a r y f o r the p y r o l y s i s a n a l y s i s , which i s performed on suspended m a t t e r c o a t e d on a m e t a l w i r e o f 0.5 mm, and because sand p a r t i c l e s do not s t i c k t o t h e s e sample c a r r i e r s . As the samples a r e c o n t i n u o u s l y moved about i n the n a t u r a l environment, a r e s u s p e n s i o n procedure was thought t o be a minor d i s t u r b a n c e o f the o r i g i n a l sediment. The washing p r o c e d u r e , i n which d e s t i l l e d water i s passed o v e r the f i l t e r w i t h p a r t i c u l a t e mat­ t e r may however r e s u l t i n l o s s of s o l u b l e o r g a n i c m a t t e r t o g e t h e r w i t h t h e sea s a l t s . T h i s measure has been a p p l i e d i n the e a r l i e r p r o f i l l i n g s t u d i e s of e s t u a r i e s (6,7) w i t h PMS and no n e g a t i v e i n f l u e n c e on the r e s u l t s c o u l d be shown. The t e c h n i c a l advantage i s t h a t the HC1 v o l a t i l i z e d from sea s a l t s d u r i n g p y r o l y s i s a n a l y s i s i s m i n i ­ mized and m a t r i x e f f e c t s on the o r g a n i c m a t t e r p y r o l y s i s p a t t e r n s

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due t o t h e presence o f s a l t s i s a v o i d e d . I t i s c l e a r t h a t i f d i f f e r ­ ences a r e found i n the c o m p o s i t i o n o f the samples d e s p i t e t h i s work­ up, t h e o r g a n i c m a t t e r c h a r a c t e r i s t i c s must be v e r y s t a b l e and s t r o n g ­ l y connected t o the p a r t i c u l a t e m a t t e r f r a c t i o n . S c r e e n i n g by Automated P y r o l y s i s Mass S p e c t r o m e t r y . The t o t a l d a t a f i l e a f t e r a n a l y s i s o f a l l samples i n q u a d r u p l i c a t e c o n s i s t e d o f 172 p y r o l y s i s mass s p e c t r a . A l l samples were s i g n i f i c a n t l y d i f f e r e n t from a p r o c e d u r a l b l a n k . I n the t o t a l f i l e o n l y the mud f r a c t i o n from s t a ­ t i o n 7A ( a l l r e p l i c a t e s ) was s t r o n g l y d i f f e r e n t i n p y r o l y s i s mass spectrum from a l l o t h e r s p e c t r a . The p y r o l y s i s spectrum o f 7A was v e r y s i m i l a r t o the spectrum o f c e l l u l o s e . The c e l l u l o s e i n t h i s s e ­ diment may have o r i g i n a t e d from the o u t f a l l sewer o f The Hague c i t y , which e x i t s nearby. The carbon i s o t o p e δ o f -25.44% (8) p o i n t s to a nonmarine o r i g i n . A f t e r removal of t h e 7A a n a l y s e s from the d a t a f i l e , f a c t o r d i s c r i m i n a n t a n a l y s i s was performed a g a i n and a d i s c r i m i ­ nant f u n c t i o n s c o r e map d i s t a n c e s between the sample rences i n composition. Discriminan of c h e m i c a l s u b s t a n c e s , e x p r e s s e d i n mass peaks, which a r e used f o r a n o p t i m a l d i f f e r e n t i a t i o n . The D-scores can be c o n s i d e r e d as the concen­ t r a t i o n o f these s u b s t a n c e s . P o s i t i v e and n e g a t i v e v a l u e s a r e o b t a i n ­ ed, because c o n c e n t r a t i o n i s e x p r e s s e d r e l a t i v e t o the average concen­ t r a t i o n i n a l l samples. About 50% and 15% o f t h e c h a r a c t e r i s t i c v a r i a n ­ ce i n the d a t a f i l e was e x p l a i n e d i n the f i r s t and second d i s c r i m i n a n t f u n c t i o n s r e s p e c t i v e l y . Instrument r e p l i c a t e s g e n e r a l l y f a l l i n t h e c e n t r o i d ( t h e s t a t i o n number) on the map. I f we c o n s i d e r o n l y the f i r s t D - f u n c t i o n , a s t r i k i n g s e p a r a t i o n between most samples from the r i v e r and the marine s t a t i o n s becomes e v i d e n t . Samples 20A, Β and ^ c o l l e c t e d h i g h e s t upstream near R o t t e r ­ dam, were found t o have the h i g h e s t p o s i t i v e Dj s c o r e s , b u t a l l s t a ­ t i o n s a t 19, 18 and two o f the t h r e e s t a t i o n s a t 17 have p o s i t i v e D-j s c o r e s . Most o f t h e s t a t i o n s from 16 a t the mouth o f the New Wa­ terway near Hoek o f H o l l a n d and a l l open sea s t a t i o n s have n e g a t i v e D^ v a l u e s . The s t a t i o n s w i t h n e g a t i v e D

Ο ω α. 16 27 60 22 14 36 17

id

_Q

•r—

to

-ο •ρ—

to φ -a

(S)

Chlorophyll Derivatives Molar Percentage

18G-1 Β PA 479-3-2 BC-5 SC-6 SC-4 *Sample locations 10G (G.C.,S10): 27 20.2'N χ 1 1 1 3 3 . 6 ^ 18G ( G . C S 1 0 ) : 2 7 0 . 9 ' Ν χ 1 1 1 ° 2 1 . 5 ^ ΒΡΑ ( G . C C S M ) : 23°35.0'Ν χ 107°23.6'W DSDP/IP0D Leg 64, S i t e 479 (GC): 27°50.76'N χ 111°37.49°W BC-5 (Peru,Wh0I): 15°27.6'S χ 75°09.6'W SC-6 (Peru, WH0I): 15°05.1'S χ 75°43.9W SC-4 (Peru, WHOI): 15°03.1'S χ 75 30.3'W G.C. = Gulf of C a l i f o r n i a , S10 = Scripps I n s t i t u t e of Oceanography, WHOI = Woods Hole Océanographie I n s t i t u t i o n . CSM = Colorado School of Mines.

10G-5

Sample*

Table I I .

7.

LOUDA AND BAKER

Biogeochemistry of Chlorophyll

115

ship of pheophytins/pheophorbides/chlorin acids, given in Table I I , are found to be 18/47/34 or 39/37/24 for sediments deposited through oxic or anoxic bottom waters, respectively. The overall increase of pheophorbides plus c h l o r i n acids, r e l a t i v e to water column d e t r i t u s or anoxically deposited sediments, i s taken as a r e f l e c t i o n of the prolonged effects of aerobic heterotrophy during oxic deposition. That i s , benthic fauna, as well as zooplankton, appear able to remove phytol from sedimentary t e t r a p y r r o l e s . O v e r a l l , these marine sediments appear to contain about 30% pheophytins, 40% pheophorbides and 30% purpurin plus c h l o r i n acids at the onset of diagenesis. T h i s , of course, i s only a rough rule-of-thumb. Photic Zone Anoxia. In environments such as meromictic lakes and peat bogs the oxy- and chemo-clines impinge the photic zone. In these cases, anoxigenic photosynthetic bacteria (e.g. Thiorhodacea, Athiorhodacea) contribute not only to overall productivity (5,37,38 but also to the supply of tetrapyrrole pigments i n resultant s e d i ments. That bacteriochlorophyllsediments, an i n t u i t i v e conclusion, i s shown through the analyses of Mangrove Lake (Bermuda) sapropel and sediments from Big Soda Lake (Nevada). Bacteriopheophytin-a has been isolated from both sets of samples, as well as from a South F l o r i d a freshwater peat accumulat i o n (43). Figure 5 i s the e l e c t r o n i c absorption spectrum of bacteriopheophytin-a, and i t s 'dioxy-dideoxo' derivative obtained by borohydride reduction. The unique chromophores and resultant spectra of the bacteriochlorophyll-a derivative makes i n i t i a l estimation of the r e l a t i v e amounts of higher plant and bacterial chlorophylls quite easy. As an example, Figure 5b i s the spectrum of a crude extract of sapropel from Mangrove Lake. In t h i s case, the r a t i o of chlorophyll-a to bacteriochlorophyll-a derivatives as the pheophytins, i s approximately 1.3:1. Large amounts of bacterial carotenoids are also i n evidence from t h e i r characteri s t i c absorption maxima in the blue (ca.420-500nm) region. The main point of t h i s simple study i s t h a t , i n cases such as peat/coal and aquatic sapropel/'paper shale' accumulations, u l t i mate geoporphyrin ( i . e . DPEP-series) precursors beside chlorophyll-a need to be considered. In order to mold bacteriochlorophyll-a into current modified 'Treib's scheme' diagenesis (3-5) only the removal of the 3,4-dihydro and 2-acetyl features are required. That i s , an aromatization and reduction/dehydration. Tetrapyrrole Diagenesis; Increasing Sediment Depth, Age and Temperature. Organic-rich diatomaceous oozes recovered within the oxygen minimum (OMZ) of the northeast slope of the Guaymas Basin (Gulf of C a l i f o r n i a , DSDP/IPOD Leg 64-Site 479. 23) have been found to contain a wide range of chlorophyll derivatives which, with depth, cover the e n t i r e period of early diagenesis (20). Pigments as a Portion of Total Organic Carbon. The value obtained through the d i v i s i o n of tetrapyrrole pigment concentration, in ygsediment dry weight, by the percent organic carbon of the host sediment we have defined as the 'Pigment Y i e l d Index,' or PYI (44). 1

1

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

116

O R G A N I C M A R I N E GEOCHEMISTRY

The plot of PYI versus sub-bottom depth for S i t e 479, including a box-core sample as a surface sediment reference, i s shown in Figure 6. The actual trend, dotted, reveals a series of a l t e r n a t ing highs and lows down to about 200 m, sub-bottom. This most l i k e l y represents corresponding increases and decreases in producti v i t y and the severity of bottom water anoxia ( i . e . paleoenvironment). However, by smoothing the curve we obtain what we suggest i s the trend one might f i n d f o r a hypothetical depositional environment which i s constant through time. Rapid pigment loss occurs within the f i r s t 50 meters of b u r i a l , a f t e r which the rate of loss slows and eventually ceases (Figure 6 ) . During the rapid loss period of early diagenesis i t appears that defunctionalization and destructive reactions are competitive as purpurin and c h l o r i n acids, in addition to phorbides, are present. Later and deeper, defunctionalization of the surviving phorbides continues u n t i l the pigments a t t a i n a higher degree of s t a b i l i t y through aromatization, y i e l d i n g porphyrins of the DPEP-series (cf. Figur phorbide and c h l o r i n acids into proto-kerogen may occur during the e a r l i e r periods of pigment loss from the bitumen f r a c t i o n , though l i t t l e data beyond phenomenological insight (4-5,20,29,34-35) exists to support t h i s supposition. Individual Tetrapyrrole C h a r a c t e r i s t i c of Early Diagenesis. It should be noted that the " i d e n t i f i c a t i o n s ' of individual pigments given below are only t e n t a t i v e . That i s , characterization i s based only upon chromatographic m o b i l i t y , e l e c t r o n i c spectroscopy, d e r i v a t i z a t i o n s with sodium borohydride and copper and comparisons to authentic pigments treated i n l i k e manner. As such, s t r u c t u r a l proof i s not claimed and resultant geochemical reaction scenarious are given only for the chromophore of each pigment type. That i s , t h i s study investigates only diagenetic defunctionalization and offers no insight as to alkyl substituents, beyond inference. Pheophytin-a as an i n i t i a l i s o l a t e , exhibited the e l e c t r o n i c spectrum given as Figure 7. Reaction with borohydride was found to y i e l d the t y p i c a l 9-oxy-deoxo derivative as well (Figure 6, dashed l i n e ) . However, upon submitting pheophytin-a to LPHPLC, 2 forms of t h i s pigment, neither identical to the authentic compound, were found. That i s , as shown i n Figure 8, 'pheophytin-a,' from these sediments were found to exist on a more polar and less polar form, r e l a t i v e to the co-injected standard, and both yielded identical e l e c t r o n i c spectra (cf. Figure 7 ) . Chromatographic m o b i l i t y , including comparison to authentic pheophytin-a, and i t s 'allomer' ( i . e . 10-oxy-pheophytin-a) shows that the more mobile form ('PP-al') may be pyro-pheophytin-a while the more polar form ('PP-a2') i s most l i k e l y the allomer ( i . e . 10-oxy-pheophytin-a 20). In some cases, such as sample 64-481-8-2 (Figure 8 ) , small amounts of "true" pheophytin-a are present. Meso-Pheophorbides. A compound, or s e r i e s , e x h i b i t i n g the e l e c t ronic spectrum ( a l t . chromophore) of meso-pyropheophorbide-a has been i s o l a t e d from S i t e 479 sediments recovered between 72 and 246 meters (15-31°C 23) sub-bottom (20). Figure 9a i s the e l e c t r o n i c spectra of the native pigment and i t s borohydride reduction product. Reaction of each with copper (II) yielded the m é t a l l o -

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

Biogeochemistry of Chlorophyll

LOU DA A N D B A K E R

350

550 WAVELENGTH,

nm

Figure 5. E l e c t r o n i c absorption spectra, (a) bacteriopheophytin-a(solid) and the dioxy-dideoxo derivative (dashed) obtained following reduction with sodium borohydride; and (b) the crude extract of Mangrove Lake (Bermuda) sapropel.

P Y.I

Figure 6. Plot of the 'pigment y i e l d index' (PYI) versus depth of burial f o r DSDP/IPOD S i t e 479 i n the northeastern Guaymas basin slope, Gulf of C a l i f o r n i a (cf. 20).

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

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ORGANIC MARINE GEOCHEMISTRY

Figure 7. E l e c t r o n i c absorption spectra of pheophytin-a(solid) and the 9-oxy=deoxo derivative obtained following reduction with borohydride, (dashed) Isolated from DSDP sample #64-479-5-3 (20).

PPa2

20

' 4 0 ' 6'0 TIME,min.

Figure 8. P a r t i a l LPHPLC chromatograms of "pheophytins-a." (a) Sample 64-481-8-2, (b) sample 64-479-3-2 (dashed = co-injected authentic pheophytin-a), and (c) p a r t i a l l y a i r - ' a l l o m e r i z e d ' authentic pheophytin-a.

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

7. LOU DA AND BAKER

Biogeochemistry of Chlorophyll

119

meso-phorbide spectra given as Figure 9b. A l l of these spectra and reaction products are consistent with the chromophore of authentic meso-pyropheophorbide-a. The very non-polar nature of the native pigment leads us to propose that t h i s i s 7-R-7-despropio-mesopyropheophorbide-a (R=H,-CH3,-CH2CH3) generated by the reduction of the 2-vinyl-moiety and the decarboxylation of the corresponding phorbide a c i d . Oxydeoxomesopyropheophorbides. Pigments with the chromophore of the 9-oxy-deoxomesopheophorbides were i s o l a t e d from the same s t r a t a as given above for the meso-pyropheophorbides. In these cases, the Soret(S) and band 1 (I) absorption maxima resemble authentic 9-oxydeoxo-mesopyropheophorbide-a (S=396.5,I=646.5nm), i t s Cu chelate (S=402.0, 1=614.5nm), and the pigment was t o t a l l y unreactive to borohydride. This compound, t e n t a t i v e l y 9-oxy-deoxo-mesopyropheophorbide-a, i s of i n t e r e s t as i t offers a clue as to the mode of loss of the 9-ketone moiety inherite appears that the 9-keto then be dehydrated. If t h i s were to occur, the product would contain a highly strained 6,y-cycloetheno moiety. Most l i k e l y , concerted or subsequent and rapid reduction would follow and result i n the common 6,Y-cycloethano type of i s o c y c l i c ring found in geoporphyrins of the DPEP-series. Oxydeoxo-Viny1-Phorbides. Pigments e x h i b i t i n g band I absorption at 651nm, and matching other physiochemical c h a r a c t e r i s t i c s of authent i c 9-oxydeoxo-pyropheophorbide-a, have been reported as being present i n the Gulf of C a l i f o r n i a sediment s u i t e studied herein (20). Lack of s u f f i c i e n t material has precluded further study on these i s o l a t e s . Deoxomesopyropheophorbide-a and 7,8-Dihydro-DPEP. Sedimentary bitumen at or near a level of maturity such that free-base porphyrins are present or dominant also y i e l d tetrapyrroles with e l e c t r o n i c spectra c h a r a c t e r i s t i c of deoxomesopyropheophorbide-a (DOMPP-a). DOMPP-a i s i s o l a t e d , i n the greatest amounts, from the non-polar chromatographic f r a c t i o n s , has an HCL# of c a . 5-7 and, thus, are decarboxylated (7-R-7-despropio:R=-H,-CH3,-CH2CH3) analogs. As such, an alternate semi-systematic name would be 7,8-dihydro DPEP. Mass spectra of one such i s o l a t e (Figure 2) reveals that diagenetic dealkylation has occurred. That i s , at temperatures below that required for the t e t r a p y r r o l e aromatization reaction (e.g. 20-30°C. 4-5),thermal ( v i z . catagenetic) dealkylation i s hardly l i k e l y . Thus, the presence of carbon numbers below C-32, the expected product of 'Treibs' Scheme' geochemistry ( 1 , 6 - 7 ) , most l i k e l y reveals methylene-equivalency losses related to defunctionalization during early diagenesis. The intervention of sedimentary b a c t e r i a l infauna i s t h e o r e t i c a l l y possible and i s being studied. The e l e c t r o n i c spectra of the native pigment (S=393,l=640nm), i s o l a t e d from a Miocene shale of the Sisquoc formation ( C a l i f o r n i a . 24), and numerous diatomaceous oozes from the Gulf of C a l i fornia*"T20), and i t s copper chelate (S=395, I=606nm) match authentic DOMPP-a and CuDOMPP-a, respectively.

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

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ORGANIC MARINE GEOCHEMISTRY

Generation of Chlorin and Purpurin Acids; Fating Functions. S e d i ments of known oxic deposition and/or redeposition have been found to be r e l a t i v e l y enriched i n the highly polar purpurin and c h l o r i n poly-acids (5,20,28,44). The oxidative s c i s s i o n of the i s o c y c l i c ring on the nucleus of chlorophyll and i t s d e r i v a t i v e s , v i a a l l o m e r i z a t i o n , consists of a series of well documented reactions (6-7) and leads to such products as c h l o r i n (e.g. -eA,-ee,-P6) and purpurin (e.g. - 7 , - 9 , - 1 8 ) carboxylic acids (cf. Figure 1 ) . Sediments from the north r i f t of the Guaymas Basin (DSDP/IPOD Leg 64, S i t e 481.20) yielded 2 pigments of t h i s s e r i e s . Given as Figure 10 i s the "electronic spectra of purpurin-18 and c h l o r i n P6 i s o l a t e s from t h i s s i t e . Spectra, chromatographic behavior and r e a c t i v i t y towards borohydride match that of authentic pigments. As i t i s known that allomerization i s possible only with the phorbides which contain the 10-carbomethoxy group (45), we have proposed that competition between the formation of THomers (10-oxyphorbides) and the pyro-(10-H-10-decarbomethoxy major branch point during very early diagenesis (4-5,20). That i s , the generation of allomerized pigments appears t o lead to subsequent pathways which end in pigment destruction. Mechanisms of t e t r a p y r r o l e destruction i n sediments, beyond the purpurinc h l o r i n stages, are t o t a l l y unknown at present. Conversely, generation of the pyro-phorbides, e s s e n t i a l l y protecting the i s o c y c l i c ring from oxidation ( v i z . a l l o m e r i z a t i o n ) , imparts a f i r s t level of s t a b i l i t y to these pigments. Subsequent diagenetic defunctionalization of the pyro-phorbide and aromatization then leads to the DPEP s e r i e s , as given i n previous sections. Possible Oxidation of the 2-Vinyl Moiety; 2-Acetyl (or Formyl) -2-Desvinyl-Pheophorbides. A f i r s t i n d i c a t i o n t n a t , aside from reduction, the vinyl moiety of chlorophyll derivatives might be altered stems from the i s o l a t i o n of a pigment we f i r s t c a l l e d "chlorin 686," a f t e r the spectral type and position of band I absorption. The e l e c t r o n i c spectra of the native and borohydride reduced pigments are given as Figure 11. The hypsochromic s h i f t of 35.5nm ( i . e . 686.5-651.0 nm) i n the p o s i t i o n of band I absorpt i o n i s on the same order as that found for the removal of the auxochrome e f f e c t s of 2 conjugated carbonyl functions from authent i c t e s t pigments (e.g. bacteriopheophytin-a, purpurin-18). These changes do not however mimic the removal of dicarbonyl conjugation from such pigments as pheophorbide-b. Thus, 2 conjugated carbonyl moieties appear to be present and are most l i k e l y located on rings I and V. That i s , on "opposite" side of the macrocycle. The bifurcated nature of the Soret absorpt i o n f o r the native pigment i s reminiscent of the 2 - a c e t y l - 2 desvinyl (46) and 2-formyl-2-desvinyl (47) derivatives of pheophyt i n - a . Should phorbide "686" prove to contain e i t h e r the 2-acetyl or 2-formyl moieties t h i s could e a s i l y and mistakenly we f e e l , i n f e r derivation from bacteriochlorophyll-a or c h l o r o p h y l l - d , respecti v e l y . As t h i s pigments(s) was i s o l a t e d from deep-sea diatomaceous oozes, (Z=747m, DS0P/IP0D S i t e 479. 20,23) s i g n i f i c a n t input of e i t h e r purple photosynthetic bacteria or red algae, respectively, i s u n l i k e l y . Rather, we f e e l , that early diagenetic oxidation of

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

7.

L O U DA AND BAKER

121

Biogeochemistry of Chlorophyll

. τ — ι — τ . . 350 550 750 WAVELENGTH, η m

750

Figure 9. E l e c t r o n i c absorption spectra of (a) decarboxylated mesopyropheophorbide(s)-a and (b) the oxy-deoxo-derivative ob­ tained via borohydride reduction. Sample 64-479-13-1 (20).

350

~ 550 750 WAVELENGTH nm 1

Γ

Figure 10. E l e c t r o n i c absorption spectra of purpurin-18 ( s o l i d ) and chlorin-p6 (dashed)-like compounds isolated from sample 64481A-2-2 (20).

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

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ORGANIC MARINE GEOCHEMISTRY

the 2-vinyl moiety, with potential cleavage to a 2-methyl-2-desvinyl structure akin t o 'Abelsonite' (Ni-2-methyl-2-desvinyl-DPEP. 16) formation, i s a more l i k e l y diagenetic pathway. Conclusion; Modified "Treibs' Scheme" Diagenesis of Chlorophyll. The investigations reported here allow a f i r s t approximation of the diagenesis of chlorophyll to be formulated. The scheme presented as Figure 12 summarizes the proposed reaction sequences, and are, f o r now, r e s t r i c t e d to sedimentary environment. The losses of magnesium and phytol through the combined effects of c e l l u l a r senescence and p r é d a t i o n ( i . e . aerobic heterotrophy) in the water column lead to pheophytin-a and pheophorbide-a becoming the primary chlorophyll-a derivatives deposited in marine sedimentary environments. Though i t i s not known at present, the heterotrophic processes which cleave phytol more than l i k e l y also affect the 10-carbomethoxy group. Studies are underway to invest i g a t e the amounts of pyro-pheophorbides in water column detritus and surface sediments. During very early diagenesi column, 2 key competing or ' f a t i n g ' reactions appear t o d i r e c t subsequent a l t e r a t i o n , i . e . allomerization versus loss of the 10carbomethoxy moiety. In the presence of oxygen, allomerization leads to the oxidative s c i s s i o n of the i s o c y c l i c r i n g . Products found i n oxidative environments include the purpurin and c h l o r i n acids (Figure 11). Tracing the down-hole fate of these compounds has proved f u t i l e , to date. That i s , in cases were oxidation dominates, such as in sediments low i n metabolizable organics ( i . e . P h i l i p p i n e Sea. 48-50), t e t r a p y r r o l e pigments disappear with depth. Thus, we can but surmise that the c h l o r i n acids are destroyed and y i e l d uni d e n t i f i a b l e low molecular weight colorless compounds (LMWCC), Figure 12). It i s t h e o r e t i c a l l y possible to derive various ETI0series porphyrins from c h l o r i n acids (5-7). However, no data yet exists to support t h i s alternate pathway. The loss of the 10-carbomethoxy moiety from the pheophorbides generates the pyropheophorbides and prevents allomerization (45). Based on the down-hole sequencing of pigments at DSDP/IPOD s i t e 479 (20), and past p a r t i a l sequences (4-5,28-29,44), the generation of free-base geoporphyrins, at least of the DPEP-series, appears to follow that given i n Figure 12. I t should be noted that tentative i d e n t i f i c a t i o n s have been made only for the decarboxylated species. However, an analogous series of these pigment types does appear to be present as the f r e e - a c i d ( v i z . 7 - p r o p i o n i c ) analogs. Reduction of the 2-vinyl and 9-keto moieties has been found to occur i n the same s t r a t a and to be unconcerted. Early diagenesis thus y i e l d s meso-and 9-oxydeoxo-pyropheophorbides, with or without the carboxylic acid moeity inherited from c h l o r o p h y l l . Reduction of e i t h e r the 9-keto or 2-vinyl of these d e r i v a t i v e s , respectively, followed by dehydration and, ostensibly, rapid reduction y i e l d s the corresponding deoxomesopyropheorbide-a (DOMPPa). Following the generation of DOMPP-a, again as e i t h e r the carboxylated or decarboxylated forms, increasing thermal stress leads to aromatization and y i e l d s DPE or DPEP, respectively.

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

7. L O U DA A N D B A K E R

123

Biogeochemistry of Chlorophyll

Figure 11. Electronic absorption spectra of a probable dioxophorbide before ('native,' s o l i d trace) and a f t e r (dashed trace) reduction with borohydride. Isolated from DSDP sample 64-479-5-3 (20). PHEOPHORBIDE-a(PPa)

+ 2 ^ ^ P Y R O - PPa MESOPYRO-PPa

k

2

P U R P U R I N S (e.g-18)

>

CHLORIN5

9-OD-PYRO-PRa

9-OD-MESOPYROPRa

(R = H)

*y. # DEOXOPYRO-PRa

(e.g-F^) ?-*LMWCC

ETIO-PORPHYRINS (C#^30)

DOMPPa" (R=COOH)

I aromatization: - 2 H • NiDPE

DPE

|chelation:-2H^Nr > DPEP

> Ni D P E P

Figure 12. Proposed diagenesis of chlorophyll-a d e r i v a t i v e s . Code: MESO = 2-vinyl reduced to e t h y l ; PYRO = lacks C# 10 carbomethoxy group; 0D = 9-oxydeoxo; asterisk = possible 6,y-cycloetheno intermediate; LMWCC = low molecular weight colorless compounds (cf. Figure 1).

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In conclusion, the early diagenesis of chlorophyll-a derivatives and the generation of the DPEP-series porphyrins roughly p a r a l l e l s the predictions which Professor Treibs made a half a century ago (1). Though certain inroads have been made, much i n the way of structural and mechanistic study remains. That i s , the generation of dealkylated species and the highly l i k e l y incorporation of tetrapyrroles into kerogen during early diagenesis are a l l but unknown. Acknowledgments The authors' are funded by NSF grant #0CE-82-08-107, the support of which i s appreciated. The following people and i n s t i t u t i o n s are h e a r t i l y thanked for samples (see "Experimental" and Table I I ) : The DSDP/IPOD program; B.R.T. Simoneit (U.C.L.A., SIO-Samples); B. Parker and D. Waples (C.S.M.); R. Oremland (U.S.G.S.), P. Hatcher (U.S.G.S.), and R. B. Gagosia Sampling of The Peruvia 0CE-77-26084, 0CE-079-25352 and OCE-80-18436 to W.H.O.I. (R.B.G.,J.W.F.). Mobil Research and Development Corporation (W. L. Orr) i s thanked for shale and petroleum samples and a g r a n t - i n - a i d . Drs. G. Eglinton and G. Wolff are thanked for t h e i r c r i t i c a l reading of the o r i g i n a l manuscript. The patience of Ms. Cora Woodman during the revision of t h i s text i s appreciated. L i t e r a t u r e Cited 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

Treibs, A. Angew. Chem. 1936, 49, 682-6. Baker, E. W. In "Organic Geochemistry;" Eglinton, A. and Murphy M. T. J., Eds.; Springer-Verlag; B e r l i n , 1969; pp. 464-97. Baker, E. W.; Palmer, S. E. In "The Porphyrins Dolphin, D., Ed.; Academic Press: New York, 1978; Vol. I, pp: 486-552. Baker, E. W.; Louda, J. W. In "Advances i n Organic Geochemistry - 1981," Bjoroy, M. et al ., Eds.; John-Wiley: Chichester, 1983: pp. 401-21. Baker, E. W.; Louda, J. W. In "Biological Markers," Johns, R. B., Pergamon: Oxford, i n press. "The Porphyrins," Dolphin, D., Ed.; Academic Press: New York, 1978-1979; Vols. I-VII. "Porphyrins and Metalloporphyrins," Smith, K.M., Ed.; E l s e v i e r : Amsterdam,1975; 910 pp. Lemberg, R.; B a r r e t t , J. "Cytochromes;" Academic Press: London, 580 pp. Quirke, J. M. E.; Eglinton, G.; Maxwell, J. R. J. Am. Chem. Soc., 1979, 101, pp. 7693-7. Quirke, J. M. E.; Shaw, G. J.; Soper, P. D.; Maxwell, J. R. Tetrahedron, 1980, 3G, pp. 3261-7. Quirke, J. M. E.; Maxwell, J. R. Tetrahedron, 1980, 36, pp. 3453-6. Quirke, J. M. E., Maxwell, J. R.; Eglinton, G; Sanders, J. K. M. Tetra. L e t t s . , 1980, 21, pp. 2987-90.

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

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13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34.

35. 36.

Biogeochemistry of Chlorophyll

Quirke, J. M. E.; Eglinton, G.; Palmer, S. E. Baker, E. W. Chem. Geol., 1982, 35, pp. 69-85. Wolff, G. Α.; Murray, M.; Maxwell, J. R.; Hunter, Β. K.; Sanders, J. K. M. J. C. S. Chem. Commun., 1983, pp. 922-4. Fookes, C. J. R. J. C. S. Chem. Commun., 1983, pp. 1474-6. Storm, C. B.; Krane, J.; Skjetne, T.; Telnaes, N.; Brantharer, J. F.; Baker, E. W. Science, 1984, 223, pp. 1075-6. Chicarelli, M. I.; Maxwell, J. R. Tetrahedron Letts., 1984, 25, pp. 4701-4. Gagosian, R. B.; Loder, T.; Nigrell: G.; Mlodzinska, Z.; Love, J.; Kogelschatz, J. W. H. O. I. Tech. Rep., 1980, WHOI-80-1, 77 pp. Henrichs, S. M.; Farrington, J. W. Limol. Oceanogr., 1984, 29, pp. 1-19. Baker, E. W.; Louda, J. W. In "Init. Reps. D.S.D.P.," Curray, J. R.; Moore, D. G.; et al., Eds.; U.S. Govt. Printing Office: Washington, D.C. Cloern, J. E.; Cole 1983, 28, pp. 1049-1061. Hatcher, P. G.; Simoneit, B. R. T.; MacKenzie, F. T.; Neuman, A. C.; Thortenson, D. C.; Gerchakov, S. M. Org. Geochem., 1982, 4, pp. 93-112. Curray, J. R.; Moore, D. G.; et al. "Init. Reps. D.S.D.P. LXIV," U.S. Govt. Printing Office: Washington, D.C., Vol. G4-Part I, 507 pp. Baker, E. W.; Louda, J. W.; Orr, W. L. unpublished data. Petracek, F. J.; Zechmeister, L. Analyt. Chem., 1956, 28, pp. 1484-5. s.; Springer-Verlag; Berlin, 1969; pp. 464-97. Krinsky, N.I. Analyt. Biochem., 1983, 6, 283-302. phin, Holt, A. S. Plant Physiol., 1959, 34, pp. 310-314. Baker, E. W.; Louda, J. W. In "Init. Reps. D.S.D.P.LVI-LVII," Langseth, M.; Okado, H.; et al., Eds.; U.S. Govt. Printing Office: Washington, D.C., Vol. 56/57 - Part 2, pp. 1397-1408. Louda, J. W.; Baker, E. W. In "Init. Reps. D.S.D.P. -LXIII," Yeats, R. S.; Haq, Β. V.; et al., Eds.; U.S. Govt. Printing Office: Washington, D.C., Vol. 63, pp. 785-818. ss: New York, Baker, E. W. J. Am. Chem. Soc. 1966, 88, 2311-5. Baker, E. W.; Yen, T. F.; Dickie, J. P.; Rhodes, R. E.; Clarke, L. E. J. Am. Chem. Soc. 1967, 89, 3631-9. Didyk, B. M.; Alturk:, Y. I. Α.; Pillinger, C. T.; Eglinton, G. Nature 1975, 256, 563-5. Yen, T. F.; Boucher, L. J.; Dickie, J. P.; Tynam, E. C.;em. Vaughn, G. B. J. Inst. Petrol., 1969, 55, pp. 87-99. Baker, E. W.; Palmer, S. E.; Hwang, W. Y. In "Init. Reps.R. D.S.D.P. - XLI," Lancelot, Y.; Seibold, E.; et al., Eds.; U.S. Govt. Printing Office: Washington, D.C., Vol. 41,, pp. 825-37. MacKenzie, A. S.; Quirke, J. M. E.; Maxwell, J. R. In "Advances in Organic Geochemistry - 1979," Douglas, A. G.; Maxwell, J. R., Eds.; Pergamon: Oxford, 1980, pp. 239-48. Holden, M. In "Chemistry and Biochemistry of Plant Pigments, 2nd. Edit.," Goodwin, T. W., Ed.; Academic Press: London, Vol. 2, 1976, pp. 2-37.

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37. Jeffrey, S. W. In "Primary Productivity in the Sea," Falkowski, P. G., Ed.; Plenum: New York, 1980, pp. 33-58. 38. Steele, J. H. "The Structure of Marine Ecosystems;" Harvard Univ. Press: Cambridge (U.S.A.), 1974, 128 pp. 39. Gagosian, R. B. personal communication. 40. Currie, R. I. Nature, 1962, 193, pp. 956-7. 41. Aronoff, S. Adv. Food Res. 1953, 4, pp. 133-84. 42. Orr, W. L.; Emery, Κ. O.; Grady, J. R. Bull. Am. Assoc. Petrol. Geol., 1958, 42, pp. 925-958. 43. Palmer, S. E.; Charney, L. S.; Baker, E. W.; Louda, J. W. Geochim. Cosmochim. Acta, 1982, 46, pp. 1233-41. 44. Louda, J. W.; Palmer, S. E.; Baker, E. W. In "Init. Reps. D.S.D.P.-LVI-LVII," Langseth, M.; Okado, H.; et al., Eds.; U.S. Govt. Printing Office: Washington, D.C., Vol. 56/57 45. Pennington, F. C.; Strain, H. H.; Svec, W. Α.; Katz, J. J. J. Am. Chem. Soc.., 1967, 89, pp. 3875.80. 46. Smith, J. R. L.; Calvin pp. 4500-6. 47. Holt, A. S.; Morley, Η. V. Can. J. Chem., 1959, 37, pp. 507-14. 48. Baker, E. W.; Louda, J. W. In "Init. Reps. D.S.D.P.-LVIII," DeVries-Klein, G.; Kobayashi, K.; et al., U.S. Govt. Printing Office: Washington, D. C., Vol. 58, 1980, pp. 737-9. 49. Pennington, F. C.; Strain, H. H.; Svec, W. Α.; Katz, J. J. J. Am. Chem. Soc.., 1967, 89, pp. 3875.80. D.S.D.P.LVI-LVII," 50. Smith, J. R. L . ; Calvin, M. J. Am. Chem. Soc., 1966, 88,ng pp. 4500-6. 51. Holt, A. S.; Morley, Η. V. Can. J. Chem., 1959, 37, III," pp. 507-14. ; Haq, Β. V.; et al., Eds.; U.S. Govt. Printing 52. Storm, C. B.; Krane, J.; Skjetne, T.; Telnaes, N.; Brantharer, J. F.; Baker, E. W. Science, 1984, 223, pp. 1075-6. ; Yen, T. F.; Dickie, J. P.; Rhodes, R. E.; 53. Baker, E. W.; Louda, J. W. In "Init. Reps. D.S.D.P.-LVIII," deVries-Klein, G.; Kobayashi, K.; et al., Eds.; U.S. Govt.n, Printing Office: Washington, D.C., Vol. 58, 1980, pp. 737-9. 54. Baker, E. W.; Louda, J. W. In "Init. Reps. D.S.D.P.-LX," Hussong, D.; Uyeda, S.; et al., Eds.; U.S. Govt. Printing Office: Washington, D.C., Vol. 60, 1981, pp. 497-500. ps. 55. Baker, E. W.; Louda, J. W. In "Init. Reps. D.S.D.P.-LXI," Larson, R. L . ; Schlanger, S.; et al, Eds.; U.S. Govt. Printing Office: Washington, D.C., Vol. 61, 1980, pp. 619-20. RECEIVED January 15, 1986

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

8 Structural Analysis of Aquatic Humic Substances by NMR Spectroscopy 1

Andrew H . Gillam and Michael A . Wilson

2

1

Institute of Offshore Engineering, Heriot-Watt University, Research Park, Riccarton, Edinburgh, EH14 4AS, Scotland CSIRO Division of Fossil Fuels, P.O. Box 136, North Ryde, NSW 2113, Australia

2

Recently developed techniques i n NMR spectroscopy have been applied to the analysis of marine and estuarine organic material. For example, the advantages of dipolar dephasin types of aliphatic and aromatic structural groups i n these materials are demonstrated. It is shown that methoxy and amino acid carbon of similar chemical shift can be distinguished. Problems in quantifying the different functional groups in marine and estuarine organic material by NMR are discussed and specific examples are given in which nonquantitative data might be expected. It was not so long ago that water chemists were content to measure the amount of dissolved organic carbon in fresh, estuarine or marine waters. At best, a l l that was known of chemical structure was the concentration of trace, albeit important organic compounds. A l l that has now changed and the chemical structure of a l l the dissolved organic substances (humic substances) is being investigated at a detailed level. Although conventional functional group analysis and Fourier transform infra-red spectroscopy are providing useful information, new revelations concerning the chemical structure of these ubiquitous materials have been largely due to developments in 1H- and 13C-NMR spectroscopy. Although some questions need to be answered concerning quantitation, major advances have been made i n determining the aromaticity (fraction of carbon which is aromatic) and carbohydrate content of these substances by NMR. Recently, 'second generation (dipolar dephasing, two dimensional NMR) 13C-NMR experiments have begun to appear i n the coal science literature which are particularly applicable to humic substances. In this paper, some applications of these techniques to the study of the structure of organic materials from aquatic systems are demonstrated. These studies concentrate on: 1) obtaining additional 1

0097-6156/86/0305-O128$06.00/0 © 1986 American Chemical Society

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

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Analysis of Aquatic Humic Substances

i n f o r m a t i o n on s t r u c t u r e , p a r t i c u l a r l y f u n c t i o n a l groups and e s t a b l i s h i n g l i m i t s on q u a n t i t a t i o n .

2)

Experimental The l o c a t i o n and sampling methods o f samples used i n t h i s work have been d e s c r i b e d elsewhere ( 1 - 5 ) . 1H- and 13C-NMR s o l u t i o n s p e c t r a were determined on a J e o l FX90Q spectrometer. The sample (~20 mg) was added t o 0.5 cm^ o f deuterium o x i d e . A few drops of 1 mol dm" 3 sodium d e u t e r o x i d e were added u n t i l the sample d i s s o l v e d . l H - s p e c t r a were o b t a i n e d at 89.99 MHz under homogated d e c o u p l i n g c o n d i t i o n s i n w h i c h the HOD peak produced by a d v e n t i t i o u s water i m p u r i t i e s and p r o t o n exchange was i r r a d i a t e d . The r a d i o f r e q u e n c y (RF) l e v e l of the HOD i r r a d i a t i o n was o p t i m i z e d f o r each sample, i . e . a s u f f i c i e n t RF l e v e l t o reduce the HOD peak t o z e r o was a p p l i e d but not enough t i n the v i c i n i t y of the HO 45° p u l s e and 8K d a t a were a c q u i r e d u s i n g 1500 Hz s p e c t r a l w i d t h . A c q u i s i t i o n time was 2.727 s, w i t h a p u l s e d e l a y of 2.0 s. Approx­ i m a t e l y 1000 scans were c o l l e c t e d f o r adequate s i g n a l t o n o i s e r a t i o . Chemical s h i f t s are quoted w i t h r e s p e c t t o i n t e r n a l t e t r a m e t h y l s i l a n e (TMS) but were measured w i t h r e s p e c t t o e x t e r n a l TMS. A capillary i n s e r t e d i n t o the sample tube was used as a r e f e r e n c e . The v a l u e s so o b t a i n e d were c o r r e c t e d by measuring the c h e m i c a l s h i f t s of n - b u t a n o i c a c i d w i t h r e s p e c t t o b o t h i n t e r n a l and e x t e r n a l TMS. S o l u t i o n 13C-NMR s p e c t r a were determined at 22.5 MHz. 8K d a t a were c o l l e c t e d u s i n g a 7000 Hz s p e c t r a l w i d t h . A c q u i s i t i o n time was 0.584 s. P u l s e d e l a y s of 1.0 t o 5.0 s were used w i t h , and w i t h o u t , i n v e r s e gated d e c o u p l i n g . Up t o 60,000 scans were c o l l e c t e d . 13C-cross p o l a r i z a t i o n magic angle s p i n n i n g (CP-MAS) s p e c t r a were o b t a i n e d on a Bruker CXP-100 i n s t r u m e n t . A r o t o r c o n s i s t i n g of a b a r r e l of boron n i t r i d e and a base o f K e l - F was used. Rotor speed w a s ~ 3 . 8 kHz. R e c y c l e time was v a r i e d from 0.3 t o 1 s. A v a r i e t y of c o n t a c t t i m e s from 0.5 t o 3ms were employed. The Hartmann-Hahn c o n d i t i o n was s e t u s i n g a sample of hexamethylbenzene. Chemical s h i f t s were measured w i t h r e s p e c t t o e x t e r n a l hexamethylbenzene (by s t o r i n g the hexamethylbenzene spectrum i n another computer memory b l o c k ) but are quoted w i t h r e s p e c t t o TMS. I t i s assumed t h a t the c h e m i c a l s h i f t s of hexamethylbenzene w i t h r e s p e c t t o TMS a r e the same i n s o l u t i o n as i n the s o l i d s t a t e . D i p o l a r dephasing experiments were performed by i n s e r t i n g a d e l a y b e f o r e d a t a a c q u i s i t i o n i n w h i c h the d e c o u p l e r was gated o f f . A 180° r e f o c u s s i n g p u l s e a l o n g the s p i n l o c k e d c o o r d i n a t e was i n s e r t e d midway i n the d e l a y p e r i o d . F u l l d e t a i l s are given e l s e ­ where (6) . I n g e n e r a l , d a t a was worked up u s i n g l i n e broadening f a c t o r s of 50 Hz or g r e a t e r f o r 13C o r 1Hz o r l e s s f o r 1H. This i s p a r t i c u l a r l y i m p o r t a n t f o r s o l u t i o n 13C-spectra where s i g n a l t o n o i s e i s poor. S o l u t i o n versus s o l i d s t a t e

NMR

I n p r i n c i p l e , s o l u t i o n or s o l i d s t a t e NMR

can be used t o study the

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s t r u c t u r e o f d i s s o l v e d o r g a n i c carbon. Both methods have advantages and d i s a d v a n t a g e s . The main advantages o f s o l u t i o n NMR a r e : 1. 2.

some degree o f e x t r a r e s o l u t i o n might be expected because o f c o n f o r m a t i o n a l freedom o f t h e o r g a n i c macromolecules; q u a n t i t a t i v e a s p e c t s a r e more f u l l y understood than f o r s o l i d state techniques.

Advantages o f t h e s o l i d s t a t e t e c h n i q u e s a r e : 1.

2.

i n c r e a s e d s e n s i t i v i t y due t o s i g n a l enhancement t e c h n i q u e s , r a p i d r e l a x a t i o n , and t h e f a c t t h a t a h i g h e r c o n c e n t r a t i o n o f n u c l e i a r e between t h e p o l e s o f t h e magnet; no a m b i g u i t y c o n c e r n i n g d e g r a d a t i o n by t h e s o l v e n t s used f o r s o l u t i o n NMR.

1H-NMR To o b t a i n a s o l i d s t a t e NMR spectrum i t i s n e c e s s a r y t o remove i n t e r ­ a c t i o n s from n u c l e i c l o s e l y bonded t o t h e n u c l e u s under i n v e s t i g a t ­ ion. F o r 1 3 C - n u c l e i t h i s i s done through a c o m b i n a t i o n o f magic angle s p i n n i n g and h i g h power p r o t o n d e c o u p l i n g t e c h n i q u e s . In the l a t t e r c a s e , t h e p r o t o n s a r e i r r a d i a t e d c l o s e t o t h e i r resonant frequency. To o b t a i n a h i g h r e s o l u t i o n lH-spectrum o f a s o l i d , h i g h power d e c o u p l i n g t e c h n i q u e s cannot be employed. Moreover, u s i n g magic angle s p i n n i n g a l o n e , t h e r e q u i r e d s p i n n i n g speeds a r e unobtainable. Thus, s p e c t r a o b t a i n e d w i t h c u r r e n t t e c h n o l o g y a r e u n s a t i s f a c t o r y i n t h a t they do n o t g i v e h i g h r e s o l u t i o n i n f o r m a t i o n . A l t h o u g h m u l t i p l e p u l s e t e c h n i q u e s may s o l v e t h i s p r o b l e m ( 7 ) , a t p r e s e n t i t i s n e c e s s a r y t o o b t a i n 1H-NMR s p e c t r a o f e s t u a r i n e and marine o r g a n i c m a t t e r by s o l u t i o n t e c h n i q u e s . This presents other d i f f i c u l t i e s m a i n l y due t o t h e h i g h c o n c e n t r a t i o n o f a d v e n t i t i o u s water. F o r example, even when d e u t e r a t e d s o l v e n t s a r e u s e d , o n l y a broad f e a t u r e l e s s spectrum o f w a t e r i s o b t a i n e d u n l e s s a d d i t i o n a l t e c h n i q u e s a r e employed. One method t h a t h a s been s u c c e s s f u l i s t o c o n t i n u o u s l y gate and i r r a d i a t e t h e w a t e r peak so t h a t t h e s e m o l e c u l e s cannot r e l a x and hence, g i v e an NMR s i g n a l ( F i g u r e 1 ) . F i g u r e 1 a l s o shows s p e c t r a o f m a r i n e , s e a l o c h and t e r r e s t r i a l humic s u b s t a n c e s . The main a p p l i c a t i o n o f 1H-NMR i s t o e s t i m a t e t h e p r o t o n a r o m a t i c i t y o f t h e samples by i n t e g r a t i n g t h e 6-8 ppm r e g i o n a g a i n s t t h e r e s t o f t h e spectrum, and s e c o n d l y , t o measure t h e amount o f b r a n c h i n g i n t h e aliphatic structures. The peak a t < 0.9 ppm a r i s e s from m e t h y l groups a t t h e end o f a l k y l c h a i n s and can be i n t e g r a t e d a g a i n s t t h e other a l i p h a t i c protons. I t s h o u l d be a p p r e c i a t e d t h a t p r o t o n s w h i c h exchange w i t h t h e s o l v e n t a r e n o t observed. 13C-NMR T y p i c a l 13C-spectra f o r humic a c i d s from a range o f s o u r c e s a r e shown i n F i g u r e s 2 and 3. F i v e major r e g i o n s o f resonance can be recognised. These a r e 0-50 ppm ( a l k y l c a r b o n ) , 50-108 ppm ( c a r b o ­ h y d r a t e , a l c o h o l , e t h e r and t h e COOH oC-carbon o f amino a c i d ) , 108160 ppm ( a r o m a t i c c a r b o n ) , 160-200 ppm ( c a r b o x y l i c , e s t e r , amide carbon) and 200-220 ppm ( k e t o n i c o r a l d e h y d i c c a r b o n ) .

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

Analysis of Aquatic Humic Substances

8. GILLAM AND WILSON

8

7

6

5

δ

4 3 (ppm)

ι

ι

I

ι

9

8

7

6

I

2

1

ι

131

0

1

1

1

1

5 4 3 δ (ppm) Chemical shift

2

1

0

F i g u r e 1. H-NMR spectrum o f humic a c i d (242 F I D s ) : (a) w i t h o u t i r r a d i a t i o n o f water peak; (b) w i t h optimum i r r a d i a t i o n o f water peak; (c) w i t h over i r r a d i a t i o n o f w a t e r peak; (d) t e r r e s t r i a l humic a c i d ( L e v i n ) ( r e f n 4 ) ; (e) d i s s o l v e d marine humic a c i d ( r e f n 1 ) ; ( f ) i n t r a c e l l u l a r a l g a l m a t e r i a l ( r e f n 1 ) ; (g) s e a l o c h s e d i m e n t a r y m a t e r i a l . (Reproduced w i t h p e r m i s s i o n from r e f e r e n c e 4. C o p y r i g h t 1983 B l a c k w e l l S c i e n t i f i c P u b l i c a t i o n s . )

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200

100

0

?

J

( ppm)

13

F i g u r e 2. T y p i c a l C-NMR s p e c t r a o f humic s u b s t a n c e s from various sources. (a) t e r r e s t r i a l ( L e v i n ) ( s o l u t i o n ) ( r e f n 5 ) ; (b) t e r r e s t r i a l (Patua) ( s o l u t i o n ) ; ( c ) f r e s h w a t e r a q u a t i c (solution) (refn 2); (d) d i s s o l v e d marine ( s o l i d s t a t e ) ( r e f n 1)

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

8.

GILLAM

133

Analysis of Aquatic Humic Substances

A N D WILSON

Recent developments i n h i g h r e s o l u t i o n 1 3 C - s o l i d s t a t e NMR s p e c t r o s c o p y have demonstrated t h a t a d d i t i o n a l i n f o r m a t i o n can be obtained i f the proton decoupler i s turned o f f f o r a short p e r i o d between i r r a d i a t i n g t h e n u c l e i i n t h e sample under i n v e s t i g a t i o n and o b s e r v i n g t h e i r subsequent b e h a v i o u r ( 8 ) . I f t h e c o r r e c t p e r i o d o f t i m e i s l e f t , ( d i p o l a r dephasing p e r i o d ) , s p e c t r a can be o b t a i n e d from o n l y m e t h y l and non-protonated c a r b o n . However, d u r i n g the d i p o l a r d e p h a s i n g p e r i o d t h e s i g n a l i n t e n s i t i e s o f t h e s e resonances a r e a l s o a t t e n u a t e d , a l b e i t a t d i f f e r e n t r a t e s from t e r t i a r y and secondary carbons. Hence f o r q u a n t i t a t i v e a n a l y s i s o f s t r u c t u r a l groups i n complex m a t e r i a l s such as d i s s o l v e d o r g a n i c m a t t e r i n marine and e s t u a r i n e w a t e r s , knowledge o f t h e decay c o n s t a n t s f o r d i f f e r e n t s t r u c t u r a l groups i s e s s e n t i a l . To t h i s end, the d i p o l a r dephasing b e h a v i o u r o f a wide range of o r g a n i c compounds has been e s t a b l i s h e d ( 9 - 1 2 ) . V a r i o u s types of carbons e x p e r i e n c e a wide range o f 13C-1H i n t e r a c t i o n s . Carbons weakly c o u p l e d t o p r o t o n s e x p o n e n t i a l law g i v e n b I =I°exp(-t,/Tp B

where 1° i s the s i g n a l i n t e n s i t y a t z e r o t i m e and T£ i s t h e e x p o n e n t i a l decay c o n s t a n t f o r t h e s i g n a l i n t e n s i t y . When t h e carbons a r e s t r o n g l y c o u p l e d t o p r o t o n s , e.g. methine and methylene c a r b o n s , t h e s i g n a l decay i s modulated by t h e s t r o n g 13C-1H c o u p l i n g and t h e o v e r a l l decay o f the s i g n a l i n t h e s h o r t t i m e l i m i t i s b e t t e r d e s c r i b e d by t h e e q u a t i o n l

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264

O R G A N I C M A R I N E GEOCHEMISTRY

Table I . S p e c i f i c Compounds Found i n Lake P o n t c h a r t r a i n Sediment Samples as well as the I d e n t i t i e s of Compounds that Comprise the Various Sub-classes of P o l l u t a n t s whose Concentration Trends are Highlighted i n t h i s Report.

Compound name

ο naphthalene a l k y l naphthalenes ο acenaphthene ο acenaphthylene biphenyl a l k y l biphenyls ο fluorene a l k y l fluorenes ο phenanthrene ο anthracene a l k y l phenanthrenes dibenzothiophene a l k y l dibenzothlophenes ο fluoranthene ο pyrene a l k y l pyrenes ο benz(a)anthracene ο chrysene a l k y l chrysenes naphthylbenzothiophene a l k y l naphthylbenzothiophenes ο benzo Fluoranthenes benzo(e)pyrene ο benzo(a)pyrene perylene ο indo(l,2,3-od)pyrene ο dibenzo(a,h)anthracene ο benzo(ghi)perylene ο d i e t h y l phthalate ο bis(ethylhexyl)phthalate ο other phthalates ο DDE DDM ο chlordane ο nonachlor ο PCB Unknown MW = 252 BP = 237

TIC

X X X X

X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X

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TAAH

FP

Phen

DBT

DDT

PCB

C/N

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X X X X

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ο USEPA P r i o r i t y P o l l u t a n t s

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

X X X

Chemicals in Lake Pontchartrain

OVERTON ET AL.

140

Phen

BF BEP BAP

Peryl

F i g u r e 8. The q u a n t i t i e s (ppb) and d i s t r i b u t i o n of n i n e p o l y n u c l e a r a r o m a t i c h y d r o c a r b o n s , a t t h r e e sampling s t a t i o n s , i n Lake P o n t c h a r t r a i n s e d i m e n t s . Phen = phenanthrene, F • f l u o r a n t h e n e , Ρ - p y r e n e , Bz • b e n z a n t h r a c e n e , C = c h r y s e n e , BF = b e n z o f l u o r a n t h e n e s , BEP benzo-e-pyrene, BAP =benzo-a-pyrene, P e r y l = p e r y l e n e .

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

266

ORGANIC MARINE GEOCHEMISTRY

Table I I . Concentration o f : T o t a l i d e n t i f i a b l e Compounds/Parent Polynuclear Aromatic Hydrocarbons (Top); PCBs/DDTs (Bottom) i n the Selected Biota Samples Expressed as PPB wet Weight.

Sample L o c a t i o n

April

'82

LP01

LP02

J u l y '82

Oct.

Shrimp * 800/15 3/2

Crab 66/17 1/2

'82

Jan

'83

Clam 360/11 6/6

LP03

Crab 178/48 12/8

LP05

Clam 570/190 130/13

LP07

Croaker 2000/85 180/70

Oyster 140/63 4/1

Crab 44/5 ND/5

Crab 1600/27 100/27 LP10

Spot F i s h 2000/280 200/130

LP15

*

Spot F i s h 130/34 17/14

Croaker 33/4 1/4

Crab 66/4 2/4

Catfish *370/10 ND/1

Contaminated with d i e t h y l h e x y l phthalate.

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

Figure 9. P l o t s showing the sediment c o n c e n t r a t i o n s of (a) barium and (b) l e a d w i t h d i s t a n c e from the s o u t h e r n s h o r e l i n e of Lake P o n t c h a r t r a i n . Sediment samples were c o l l e c t e d on dates as i n d i c a t e d i n F i g u r e 5. C o n t i n u e d on next page.

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15.

OVERTON ET AL.

Chemicals in Lake Pontchartrain

269

among these i s the tremendous r a t e of u r b a n i z a t i o n t h a t has s p r e a d i n r e c e n t decades from the m e t r o p o l i t a n New Orleans area w h i c h occupies a major p o r t i o n of the s o u t h e r n l a k e s h o r e . Because of i t s immediate p r o x i m i t y t o the l a k e and the f a c t t h a t much of t h i s area i s a t or below sea l e v e l , a network of c a n a l s on the east s i d e of the M i s s i s s i p p i R i v e r d r a i n s the area i n t o the l a k e . These c a n a l s a r e c a t c h b a s i n s f o r the s t r e e t d r a i n a g e , stormwater r u n o f f , and p o i n t source d i s c h a r g e s of t r e a t e d , p a r t i a l l y t r e a t e d and u n t r e a t e d sewage. I n a d d i t i o n , many d i s c h a r g e s from s m a l l commercial f a c i l i t i e s a r e made e i t h e r to the sewage systems or d i r e c t l y to the c a n a l s . No major i n d u s t r i a l f a c i l i t i e s ( e . g . p e t r o c h e m i c a l or o r g a n i c c h e m i c a l m a n u f a c t u r i n g ) a r e p e r m i t t e d t o d i s c h a r g e i n t o Lake P o n t c h a r t r a i n . T h e r e f o r e , the major c h e m i c a l i n p u t s of p o l l u t a n t s i n t o the l a k e may be c a t e g o r i z e d as coming from three major source c a t e g o r i e s . These a r e (1) urban stormwater drainage, (2) discharge t r e a t e d t o l e s s than a c c e p t a b l s p i l l s from marine r e l a t e d f a c i l i t i e s and marine v e s s e l s . E x a m i n a t i o n of the data suggest t h a t urban r u n o f f i s r e s p o n s i b l e f o r the g r e a t e r v a r i e t y and the h i g h e r l e v e l s of a n t h r o p o g e n i c c h e m i c a l s i n t r o d u c e d i n t o the l a k e . Sewerage d i s c h a r g e s i n t r o d u c e p o l l u t a n t s t h a t c o n t r i b u t e t o oxygen d e p l e t i o n and e u t r o p h i c a t i o n . The c o n t r i b u t i o n of o i l and other o r g a n i c substances from marine a s s o c i a t e d f a c i l i t i e s and v e s s e l s i s more r e l a t e d t o s p i l l e v e n t s , e i t h e r a c c i d e n t a l or i n t e n t i o n a l , r a t h e r than r e g u l a r , l o n g term i n p u t . Data reviewed t o date i n d i c a t e t h a t s p e c i f i c a r e a s a r e impacted by o i l s and other p e t r o l e u m h y d r o c a r b o n s . Another f a c t o r of s i g n i f i c a n t e n v i r o n m e n t a l i n f l u e n c e i s the a l t e r a t i o n of s a l i n i t y p a t t e r n s i n the s o u t h e a s t e r n and e a s t c e n t r a l r e g i o n of the l a k e o f f the mouth of the MRGO. T h i s h y d r o l o g i e m o d i f i c a t i o n f a c i l i t a t e s the i n t r u s i o n of h i g h l y s a l i n e marine waters from the G u l f of Mexico i n t o Lake P o n t c h a r t r a i n . T h i s s a l t w a t e r i n t r u s i o n i s most pronounced d u r i n g the warm water months (May to O c t o b e r ) of years w i t h normal and below normal r a i n f a l l . I t s e f f e c t s reach t h e i r peak d u r i n g the l a t e summer (August/September) when p r e v a i l i n g s o u t h e r l y and s o u t h e a s t e r l y winds g r e a t l y f a c i l i t a t e the movement of marine waters up the MRGO and i n t o Lake P o n t c h a r t r a i n . Acknowledgments The a u t h o r s would l i k e t o express thanks and a p p r e c i a t i o n t o : D. S a b i n s , W. Tucker, K. C o r m i e r , C. M e l c h i o r , L. Pacca, J . D i x o n , L. Wellman and J . A k i e l a s z e k f o r c o l l e c t i o n of samples; J . M c F a l l and S. A n t o i n e f o r a n a l y s e s of samples; P. B e n o i t , S. Stewart and D. Meyers f o r h e l p i n p r e p a r a t i o n of t h i s m a n u s c r i p t ; and the L o u i s i a n a Department of E n v i r o n m e n t a l Q u a l i t y f o r t h e i r f i n a n c i a l support·

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

270

ORGANIC MARINE GEOCHEMISTRY

Literature Cited 1. Brown, P.W.; Ramos, L.S.; Uyeda, M.Y.; Friedman, A . J . ; MacLeod, W.D. In "Petroleum in the Marine Environment"; Petrakis L . ; Weiss, F.T., Eds.; ADVANCES IN CHEMISTRY SERIES No. 185, American Chemical Society: Washington, D.C., 1980; p. 313. 2. MacLeod, W.D.; Prokaska, P.G.; Gennero, D.D.; Brown, D.W. Anal. Chem., 1982, 54, 386. 3. "Interim Methods for the Sampling and Analyses of Priority Pollutants in Sediments and Fish Tissue," U.S. Environmental Protection Agency, 1981. 4. Wakeham, A.J.; Farrington, J.W.; In "Contaminants and Sediments"; Baker, R.A., Eds.; Science Publishers Inc.: Ann Arbor, 1980; p. 3. 5. Lopez-Avila, V.; Hites, R.A. Environ. Sci. Technol. 1980, 14, 1382. 6. Hamilton, A.E.; Bates Technol. 1984, 18, 72. 7. Eganhouse, R.P.; Blumfield, D.L.; Kaplan, I.R. Environ. Sci. Technol. 1983, 17, 523. 8. Laflamme, R.E.; Hites, R.A. Geochim Cosmochem Acta. 1978, 42, 289. 9. "Review of PCB levels in the environment" US Environmental Protection Agency, 1976. 10. Whipple, W.; Hunter, J.V. I. Water Pollution Control Fed. 1977, 49, 15. 11. Boyden, C.R.; Afton, S.R.; Thorton, I. Estuarine and Coastal Marine Sci. 1977, 9, 303. RECEIVED November 8, 1985

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

16 Seasonal Cycles of Dissolved Methane in the Southeastern Bering Sea 1

2

3

Joel D. Cline , Charles N. Katz , and Kimberly Kelly-Hansen 1

Mobil Research and Development Corporation, Dallas, TX 75234 InterOcean Systems, Inc., San Diego, C A 92123 Pacific Marine Environmental Laboratory, National Oceanic and Atmospheric Administration, Seattle, WA 98115

2

3

Seasonal measurements of dissolved methane were made in the southeastern Bering Sea shelf waters between 1975-1981. Thi environment tha in b i o l o g i c a l a c t i v i t y and climate. For these reasons, and others, t h i s region i s well suited to examine the seasonal d i s t r i b u t i o n s of methane and other biologically-generated gasses. Maximum concentrations of methane were observed in the f a l l of 1981, followed by a minimum in spring. Surface concentrations, on the average, were about 400 nL/L(STP) in fall, dipping to concentrations near 100 nL/L(STP) in spring. Near bottom concentrations were generally higher throughout the region, and in p a r t i c u l a r over St. George Basin, where concentrations in excess of 2500 nL/L(STP) were observed. The sea to a i r f l u x of methane ranged from 0.021 g CH m yr in May 1981 to 0.34 g CH m yr i n October 1980; the mean f l u x was about 0.14 g CH m yr . Based on a t o t a l area of 31.9 x 10 m and correcting for average ice coverage in winter, the annual transport of methane to the atmosphere f o r 1980-81 was 4.6 x 10 g. Seasonal and interannual variations in the concentration methane are large in the southeastern Bering Sea s h e l f . The d r i v i n g force f o r these variations i s the timing and f l u x of organic carbon as well as the severity (i.e., amount of ice cover) of the winters. These observations point to the need for seasonal observations in near shore coastal waters i f meaningful budgets of methane, and presumably other trace gasses, are to be constructed. -2

4

-1

-2

4

-1

4

-1

10

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2

10

0097^6156/86/0305-O272$07.25/0 © 1986 American Chemical Society

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

16.

C L I N E ET AL.

Seasonal Cycles of Dissolved Methane

273

Methane is an ubiquitous trace gas found in a l l marine and freshwaters. Its concentration in the surface waters of the open ocean is near saturation ( 1 - 3 ) , however in some near shore areas, in anoxic basins, and in marine sediments the concentrations are s i g n i f i c a n t l y higher (4, 7) because of increased production rates. The highest production rates of methane are usually r e s t r i c t e d to anoxic environments, but s i g n i f i c a n t rates of production also have been observed in oxic marine water columns (8, 9 ) . The most complete set of published observaTions on the sources, s i n k s , and d i s t r i b u t i o n s of methane in coastal waters is that by researchers at Texas A&M University. Without d e t a i l i n g an exhaustive l i s t of the observations, many of which deal with the thermogenic as well as biogenic sources of methane, the following papers are most relevant to our own discussion of coastal d i s t r i b u tions of methane (7, 10-14). Our intent here 'fs not to summarize the extensive observations of methane in the marine environment, but rather to set the stage for a discussion of seasona environment. There are few studies of the seasonal variations of trace gases in a marine environment, and to our knowledge, none in a high l a t i t u d e , shallow sea, where b i o l o g i c a l influences are apt to be large. In t h i s report, we w i l l s p e c i f i c a l l y examine the seasonal d i s t r i b u t i o n s of dissolved methane in the southeastern Bering Sea and q u a l i t a t i v e l y discuss the physical and b i o l o g i c a l forcing that results in the observed d i s t r i b u t i o n s . Observations discussed in t h i s report were made as a part of an environmental study of Alaskan coastal waters. Methods SamplIinq. Discrete water column samples were obtained with 5-L Niskin bottles attached to a General Oceanics Rosette f i t t e d with Plessey Environmental Systems model 9040 CTD. A 1-L aliquot of seawater was transferred from the Niskin samplers into g l a s s stoppered bottles in such a way that a i r bubbles were not trapped. The bottles were then stored in the dark at approximately 5°C u n t i l analyzed; usually within one hour of sampling. Analysis Concentration. The analysis of methane was accomplished routinely in the f i e l d using a purge and trap technique (15). The method involves removal of the dissolved gases from a 0.2TT"volume of seawater by helium purging. The gasses removed from solution are passed through A s c a r i t e ® , D r i e r i t e ® and Tenax G.C.® traps to remove carbon dioxide, water vapor and heavy hydrocarbons respect i v e l y , before being concentrated on an activated alumina trap held at -196°C. After quantitative removal of the gasses from solution (approx. 6 minutes with a purge rate of 100 mL min" ), the activated alumina trap was warmed to 100°C and the gasses backflushed into a gas chromatograph. 1

Gas Chromatography. Detection and quantitation of methane was carried out on a Hewlett-Packard 5710A gas chromatograph equipped with a flame ionization detector (FID). The column packing used

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

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O R G A N I C M A R I N E GEOCHEMISTRY

was activated alumina, 60-80 mesh (1.8m χ 0.48 cm o . d . ) . The column temperature was held isothermally at 100 C. Quantitation of the methane was obtained by comparing the detector response of a methane gas standard with that of the sample. The FID response was found to be linear with concentration throughout the entire range of methane concentrations encountered in the study. Standard gasses prepared by Matheson Gas Products were i n t e r c a l i b r a t e d with a standard gas analyzed by the National Bureau of Standards (NBS). Analytical precision was generally less than 1% while accuracy, based on the NBS i n t e r c a l i b r a t i o n , was 5%. The detection l i m i t of the method, based on a s i g n a l - t o - n o i s e r a t i o of 2 i s approximately 5 nL CH^ L* seawater (STP). e

1

SalIinity-Temperature-Pressure (Depth). Conductivity, temperature and pressure data were c o l l e c t e d using a Plessey Systems CTD with model 8400 data logger. These sensors were interrogated f i v e times per second fo ( s a l i n i t y ) , and pressure (depth). Data were recorded during the down-cast using a lowering rate of 30 m min" . Niskin bottle samples were taken on every other cast to provide temperature and s a l i n i t y c a l i b r a t i o n . Nominal precision of the s a l i n i t y , temperature and depth measurments was ± 0.02 g k g " , ± 0.02 °C and ± 0.2 m, respectively. 1

1

Physical Setting The survey area, which includes B r i s t o l Bay, i s a broad shelf region located in the southeastern Bering Sea (Figure 1 ) . It i s bounded on the south by the Alaska Peninsula, on the west by the shelf break, and on the north by the coast of Alaska (1(6). The area out to the 200 m isobath i s about 32 χ 1 0 m ; the area-weighted mean depth i s about 70 m. The p r i n c i p a l sources of fresh water are the Kuskokwim and Kvichak r i v e r s , which are located at the northern and eastern boundaries (Figure 1). Estimated discharge of these r i v e r s i s about 47 km annually (17), but there are also numerous small, d i f f u s e sources of fresh water along the e n t i r e c o a s t l i n e . Notable among them i s the Port Mol 1er estuary located along the north side of the Alaska Peninsula. Winter cooling r e s u l t s in a maximum of 60% of the southeastern Bering Sea being covered with ice between the months of December and A p r i l (16). This ice i s largely wind driven from the north, although during severe winters there is local ice formation. Hydrographically, the region i s divided into three domains: coastal waters (z < 50m), middle shelf (50 m < ζ < 100m), and the outer shelf (z > 100m) (LB). The greatest seasonal variations in temperature and salinity"^are found in the coastal zone because of i t s shallow depth and close proximity to sources of fresh water. In contrast to the coastal regime, which i s u n s t r a t i f i e d most of the year because of wind and t i d a l mixing, the middle shelf i s thermally s t r a t i f i e d much of the year. The outer s h e l f , p r i n c i ­ p a l l y St. George Basin (Figure 1 ) , i s characterized by s a l i n i t é s 10

2

3

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

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LONGITUDE W β

Figure 1. Location of the southeastern Bering Sea, showing hydrographie regimes and bathymetry. Also shown in the position of a v e r t i c a l section across the region (see Figure 4 ) . Individual station l o c a t i o n s , which varied from cruise to c r u i s e , are shown on the areal d i s t r i b u t i o n maps.

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

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near 33% and a temperature range of 3-4°C. Surface temperatures and s a l i n i t i e s are somewhat greater in summer. Currents over the shelf are generally weak (19, 20). Along the outer shelf in summer, current t r a j e c t o r i e s trend northwest at speeds of approximately 5 cm/sec. Across the inner s h e l f , currents are weak (~ 1 cm/sec) and counterclockwise. Seasonal D i s t r i b u t i o n s of Dissolved Methane The v e r t i c a l and horizontal d i s t r i b u t i o n s of dissolved methane are not only controlled by b i o l o g i c a l processes, but also by the local hydrography, which has a marked seasonal signature. S t r a t i f i c a t i o n strongly influences the v e r t i c a l transport of methane and other gasses, and is largest where the buoyancy input is the greatest. Warming of the surface layers and the addition of fresh water from land drainage leads to a reduction in the density of the surface waters and subsequent s t r a t i f i c a t i o n . Because s i g n i f i c a n t way the v e r t i c a l transport of methane, a b r i e f description of the seasonal changes in s a l i n i t y and temperature is i n s t r u c t i v e . The coastal regime experiences large seasonal changes in water properties, because of i t s nearness to land and i t s shallow depth. Figure (2a) shows the temperature and s a l i n i t y f i e l d s for the three seasons, superimposed on the l i n e s of constant density {a = (p-1) χ 1000}. A large change in s a l i n i t y is seen in August and is the result of fresh water runoff along the Alaska Peninsula. The lowest s a l i n i t i e s are found near the Kvichak River, and the highest s a l i n i t i e s are found near Unimak Pass. R e l a t i v e l y s a l i n e water entering Unimak Pass is driven c y c l o n i c a l l y around the basin and gradually becomes less s a l i n e due to freshwater d i l u t i o n . Winter and spring are characterized by isohaline conditions (30-32 ° Λ · ) , however the temperature r i s e s from near freezing in winter to 4-8 °C in May. The middle shelf is not so strongly influenced by seasonal changes in s a l i n i t y because i t i s farther removed from land. However, temperatures there range from near freezing in winter to about 10 °C in August ( F i g . 2b). The s a l i n i t y range is 30-32 °/oe, about the same as observed in the coastal zone away from major sources of freshwater. t

Methane: August, 1980. The surface d i s t r i b u t i o n of dissolved methane (nL/L, STP) in August 1980 is shown in Figure 3a. The highest surface concentrations were found near the entrance to Port Mol 1er and near Unimak Pass (see Figure 1 ) . At the entrance to Port Mol 1er, concentrations of dissolved methane were greater than 2500 nL/L (about 35 times the equilibrium value) and decreased along the coast toward the northeast. The d i r e c t i o n of the methane plume marks the mean d r i f t of the coastal current.

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

CLINE ET AL.

Seasonal Cycles of Dissolved Methane

24

26

28

30

SALINITY

32

34

36

(%o)

Figure 2. Temperature and s a l i n i t y f i e l d s for the coastal (a) and middle shelf (b) regions. Surface measurements at each station were averaged and plotted for the three observational periods.

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

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LONGITUDE

β

W

Figure 3 . The surface (a) and near-bottom (b) concentrations of methane (nL/L; S.T.P.) observed in August, 1980. The near-bottom measurements were r o u t i n e l y taken 5 m above the bottom.

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

16.

CLINEETAL.

Seasonal Cycles of Dissolved Methane

279

Over the remainder of the region, concentrations of methane ranged from 300-500 nL/L. The small surface maximum observed near Unimak Pass arises from v e r t i c a l turbulence in Unimak Pass. Near-bottom waters south of the Alaska Peninsula are enriched in methane, which becomes entrained in the northerly flow through the pass. Again, the surface concentrations of methane indicate the mean surface current d r i f t as water moves into the Bering Sea. D i s t r i b u t i o n s of dissolved methane near the bottom ( i . e . , 5m above the bottom) are shown in Figure 3b. The largest accumulations were found over St. George Basin, a topographic depression located on the outer s h e l f . These sediments are fine-grained and r e l a t i v e l y r i c h in organic carbon ( T O C ^ = 1%) (21). Contours of methane concentration generally follow the basin bathymetry, indicating weak c i r c u l a t i o n and a l o c a l i z e d source of methane in the basin. The maximum concentration of methane observed in August 1980 was 2500 nL/L, decreasing to background concentrations of 500 nL/L over the middle shelf. In contrast, concentration and the coastal region were s i m i l a r to the concentrations seen in the surface waters of St. George Basin. Over most of the middle s h e l f , near-bottom concentrations of methane ranged from 400-600 nL/L. An example of cross-shelf variations in water properties and t h e i r influence on the d i s t r i b u t i o n of methane is shown in Figure 4 (see Figure 1 for the location of the v e r t i c a l s e c t i o n ) . The estuarine character of the embayment is c l e a r l y shown by the d i s t r i b u t i o n of s a l i n i t y , where low s a l i n i t y water at the surface moving seaward i s being replaced by higher s a l i n i t y water at depth. High concentrations of methane are evident in the bottom waters of St. George Basin (PL4-PL8) and are the result of increased production and s t r a t i f i c a t i o n . There, v e r t i c a l s t r a t i f i c a t i o n (Figure 4c) r e s t r i c t s the upward transport of methane. In the coastal zone (z < 50m), the concentration of methane is homogeneous with depth, indicating more intense mixing. Methane: January, 1981. In winter, surface concentrations of methane had f a l l e n to 200-400 nL/L, or about 50% of that seen the previous summer (Figure 5a). Once again, the highest surface concentrations were found near the entrance to Port Mol 1er and northeast of Unimak Pass. Ice covered much of the middle shelf and northern coastal regions, which r e s t r i c t e d observations to the southern reaches of the area. The maximum surface concentration of methane observed was 2500 nL/L at the entrance to Port Mol 1er, once again demonstrating that t h i s estuary is a s i g n i f i c a n t source of methane to the coastal regime, even in winter. High concentrations were again evident in the near-bottom waters of St. George Basin (Figure 5b). In contrast to concentrations approaching 2500 nL/L seen the previous August ( F i g . 3b), maximum concentrations had decreased to about 1100 nL/L. Bottom concentrations over the middle shelf were about 200-300 nL/L, the same as the surface waters.

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

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Figure 4. The v e r t i c a l d i s t r i b u t i o n s of s a l i n i t y , temperature, sigma-t ( i . e . , density) and methane observed along PL1-PL24 in August, 1980. See Figure 1 for the location of t h i s section. Sigma-t i s equal to (P-1) Χ 1000, where ρ i s the s p e c i f i c - g r a v i t y seawater.

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

281

Seasonal Cycles of Dissolved Methane

C L I N E ET AL.

.

r,\r s t r i e r

172°

168°

.

,

ι

164°

1

1

160°

LONGITUDE W

1 156°

0

ι 172°

if V

t'(TVMir ι 168°

1

1

164°

»

«

160°

1

156°

LONGITUDE W 0

Figure 5. The surface (a) and near-bottom (b) concentrations of methane (nL/L) observed in January, 1981.

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

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Methane: May, 1981. By late spring, surface concentrations had decreased to about 70 nL/L over much of the middle s h e l f , but remained high in the North Aleutian coastal waters (Figure 6a). The maximum concentration near Port Mol 1er had decreased to about 600 nL/L. Maximum concentrations of methane near the bottom of St. George Basin approached 1200 nL/L, which was about the same concentration seen in January (Figure 6b). Near-bottom concent r a t i o n s over the middle shelf were only s l i g h t l y greater than the concentrations seen in the surface waters. Methane: September 1975 and J u l y , 1976. Concentrations of dissolved methane also were measured in the southeastern Bering Sea in the f a l l of 1975 and again during the following summer. These observations are shown for both surface and near-bottom waters in Figures (7a,b, and 8a,b). As noted e a r l i e r , the highest surface concentrations of methane were near Port 1500 nL/L in July 1976. Measurements were not obtained near the mouth of the estuary in September 1975, so comparable values were not a v a i l a b l e , but the coastal plume appears weaker than that seen in July 1976 (compare Figures 7a and 8 a ) . Over the remainder of the embayment, concentrations were generally less than 100 nL/L, except as previously noted in the coastal zone. Maximum concentrations of methane were again observed in the near-bottom waters of St. George Basin, however, the r e l a t i v e l y large amounts observed in 1980-1981 were s i g n i f i cantly lower in July 1976 (Figure 8b). The near bottom plume was more pronounced in October 1975, but maximum concentrations of 600 nL/L were below the concentrations seen in 1980-1981. T

Processes Controlling the D i s t r i b u t i o n of Methane Internal Sources and Atmospheric Exchange of Methane. Methane i s produced by specialized groups of obligate anaerobic bacteria (22, 23). The formation of methane as a metabolic product r e s u l t s either from the microbial reduction of C O 2 with molecular H , or v i a the fermentation of acetic a c i d . More s t r u c t u r a l l y complex substrates may also serve as electron acceptors/donors, but the end r e s u l t of methanogenesis is to produce methane and C0 as end products (23). Large production rates of methane are apparently only r e a l i z e d in the absence of dissolved oxygen and sulfate ions (6, 24), although methanogenesis and sulfate reduction should not be thought of as mutually exclusive processes (24, 25). While i t may be macroscopically u n r e a l i s t i c to consider methane production in the presence of oxygen and/or sulfate ions, s i g n i f i c a n t amounts of methane can be produced in oxic (9) and s u l f a t e bearing waters (24, 26), presumably within o r g a n i c - r i c h microenvironments. mese microenvironments might be organic p a r t i c l e s in the water column, organic floes at the sedimentwater i n t e r f a c e , or anaerobic metabolism in the gut of planktonic animals. For these reasons, i t is reasonable to 2

2

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

Seasonal Cycles of Dissolved Methane

C L I N E ET AL.

ι 172°

tr\r

/ R'SH + RSH + ( C ^ ^ P ^ O

A l t h o u g h t h i s reagent had o n l y been used i n the p a s t t o p r e s e r v e s t a n d a r d t h i o l s o l u t i o n s , i t was f e l t t h a t i t c o u l d a l s o be employed to q u a n t i f y t h e r e l a t i v e amounts o f -S-S- bound t h i o l s i n s e d i m e n t s . However, s i n c e t r i b u t y l p h o s p h i n e had n o t been p r e v i o u s l y used i n s e a w a t e r media, a p r e l i m i n a r y t e s t was performed t o e v a l u a t e i t s c h e m i c a l b e h a v i o r unde o x i d i z e d g l u t a t h i o n e wer o f 1 μΜ e a c h . T r i b u t y l p h o s p h i n e was a d d e d ( 0 . 5 m l p e r l i t e r s e a w a t e r ) and t h e samples were i n c u b a t e d a t 25 C i n t h e presence o f air. A l i q u o t s were p e r i o d i c a l l y removed f o r t h i o l a n a l y s i s . A f t e r 20 m i n , 95% of t h e d i s u l f i d e s were reduced t o t h i o l s ( F i g u r e 7 ) . The t h i o l s were s t a b l e f o r t h r e e days even i n t h e presence of a i r . A f t e r t h i s p e r i o d , r e o x i d a t i o n o c c u r r e d p r o b a b l y due t o l o s s o f the excess and p r o t e c t i v e phosphine by r e a c t i o n w i t h oxygen. From these t e s t s i t was concluded t h a t t h e phosphine reagent c o u l d be used t o s t u d y t h e r e l a t i v e abundance o f f r e e v e r s u s -S-S- bound t h i o l s i n reducing sediments. Sediment s l u r r i e s were i n c u b a t e d a t 30°C (approximate i n s i t u t e m p e r a t u r e ) w i t h and w i t h o u t t r i b u t y l p h o s p h i n e . A l i q u o t s of p o r e w a t e r were p e r i o d i c a l l y removed f o r t h i o l a n a l y s i s over the f o l l o w i n g 2-4 days. D u r i n g t h e course of t h i s s t u d y , a t o t a l o f 7 s u c h i n c u b a t i o n s were performed on f r e s h l y c o l l e c t e d sediment. R e s u l t s were s i m i l a r i n a l l cases and t y p i c a l l y showed that t r i b u t y l p h o s p h i n e induced a d r a m a t i c and r a p i d r e l e a s e o f bound ( o r o x i d i z e d ) t h i o l s ( T a b l e IV and F i g u r e 8 ) . Bound t h i o l s were p r e s e n t a t a p p r o x i m a t e l y 20 times g r e a t e r c o n c e n t r a t i o n s than f r e e t h i o l s ( i . e . , ^ 9 5 % o f a l l t h i o l s r e l e a s e d from sediment were i n i t i a l l y bound). I f a i r i s not e x c l u d e d d u r i n g the i n c u b a t i o n , r e l e a s e d t h i o l s become r e o x i d i z e d a f t e r s e v e r a l days ( F i g u r e 8) p r o b a b l y due t o t h e o x i d a t i o n o f t h e p r o t e c t i v e phosphine. Addition of fresh t r i b u t y l p h o s p h i n e regenerated the t h i o l s . A d d i t i o n o f t r i b u t y l p h o s p h i n e t o e x t r a c t e d porewater ( p a r t i c l e f r e e ) r e s u l t e d i n o n l y a minor i n c r e a s e i n t h i o l c o n c e n t r a t i o n s . This r e s u l t i n d i c a t e s that the dramatic increases obtained with s l u r r i e s (Table IV and F i g u r e 8) a r e p r o b a b l y due t o r e l e a s e o f t h i o l s bound t o p a r t i c l e s u r f a c e s , a s o p p o s e d t o r e l e a s e f r o m d i s u l f i d e s d i s s o l v e d i n the i n t e r s t i a l water. S u r f a c e b i n d i n g i s most l i k e l y t h r o u g h -S-6- l i n k a g e s , but i t i s a l s o c o n c e i v a b l e t h a t some f r a c t i o n o f t h e r e l e a s e d t h i o l s may be due t o d i s p l a c e m e n t of t h i o l s from m e t a l complexes on p a r t i c l e s u r f a c e s by t h e phosphine n u c l e o p h i l e . However, when an e q u i v a l e n t amount o f a s t r o n g m e t a l complexing agent (EDTA) was s u b s t i t u t e d f o r the phosphine, o n l y n e g l i g i b l e r e l e a s e s o f t h i o l s were o b s e r v e d , suggesting t h a t , f o r t h e sediments s t u d i e d , b i n d i n g by m e t a l

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

19.

772/o/5 in Coastal Marine Sediments

M O P P E R A N D TAYLOR

1 uM GLUTATHIONE ( O X , )

RED.

GLUT.

I

1 μΜ GLUTATHIONE ( O X . )

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1 M—

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RED.

^

GLUT.

2 μΜ GLUTATHIONE ( R E D . )

r

K

J

/ V L _

U^-Lr

F i g u r e 7 . C l e a v a g e o f o x i d i z e d g l u t a t h i o n e i n s e a w a t e r by t r i b u t y l p h o s p h i n e t o y i e l d reduced g l u t a t h i o n e ( r e d . G l u t . ) ; d e t e c t i o n by f l u o r e s c e n c e d e r i v a t i z a t i o n a n d HPLC. U p p e r : O x i d i z e d g l u t a t h i o n e (luM) alone. Middle: Oxidized glutathione ( l u M ) p l u s t r i b u t y l p h o s p h i n e (50 μΙ/lOOml seawater) r e a c t e d f o r 20 min a t 25 C; Lower : Reduced g l u t a t h i o n e s t a n d a r d (2μΜ) i n seawater.

I n c u b a t i o n time ( h r )

F i g u r e 8. R e l e a s e o f t h i o _ l s ( 3 - m e r c a p t o p r o p i o n a t e - MP a n d m e t h a n e t h i o l - MeS) and HS upon a d d i t i o n o f t r i b u t y l p h o s p h i n e (50μ1 p e r 100 ml s l u r r y ) t o a B i s c a y n e Bay sediment s l u r r y ; incubated at 25 C; control slurries received no tributylphosphine·

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

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O R G A N I C M A R I N E GEOCHEMISTRY

complexation may not be as important as b i n d i n g by -S-S- bond formation. Specific methods for releasing metal bound t h i o l s are being explored.

Table IV. Release of Bound Thiols from Sediment

Incubated Sediment*

3-Mercaptopropionate (μΜ)

Control Slurry*

0.19

Slurry with Tributylphosphine*

6.5

% T h i o l Bound*

97%

Methanethiol

HS~

SO^

(μΜ)

(mM)

(mM)

0.05

4.24 0.071

96%

31%

0%

* 8/24/84; Biscayne Bay i n t e r t i d a l sediment incubated f o r 23h at 25 C; t h i o l s detected i n the "control s l u r r y " (no tributylphosphine added) are interpreted as being i n the unbound (or free) state; t h i o l s detected i n "slurry with tributylphosphine" are interpreted as free plus bound species; the "% t h i o l bound" was calculated from: [(thiols i n tributylphosphine treated s l u r r y ) - ( t h i o l s i n control)] χ 100%/(thiols i n tributylphosphine treated s l u r r y ) .

Summary and Conclusions Thiols are present at s i g n i f i c a n t levels i n reducing, i n t e r t i d a l sediments and apparently arise as a result of interacting b i o t i c (microbial) processes and a b i o t i c reactions (Figure 9). Over 30 t h i o l s were detected, of which methanethiol and 3-mercaptopropionate were present i n the highest concentrations throughout the entire 4 month sampling period. Methanethiol can readily arise through a number of known anaerobic pathways; however, no such pathways have been reported for the formation of 3-mercaptopropionate. I t can be speculated that this compound i s produced by successive anaerobic demethylations of dimethylpropiothetin (DMPT), a major sulfur compound of marine algae and plants. On the other hand, the known anaerobic breakdown pathway of DMPT i s v i a enzymatic cleavage to y i e l d dimethylsulfide and a c r y l i c acid. A c r y l i c acid i s a highly reactive species and, i n zones of active sulfate reduction, i t w i l l readily undergo a Michael addition with HS to yield 3-mercaptopropionate (Figure 6). I f this reaction i s i n fact o c c u r r i n g i n sediments and i n the water column of anoxic basins, a number of important geochemical implications can be inferred. For every mole of DMPT hydrolyzed, up to two moles of organosulfur compounds (dimethylsulfide and 3-mercaptopropionate) are produced. If direct b i o l o g i c a l sources are indeed negligible for the l a t t e r compound, then i t s c o n c e n t r a t i o n and turnover may be used to estimate that of a c r y l i c acid and i n d i r e c t l y that of DMPT hydrolysis

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

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i n the environment. More generally, the results imply that a major chemical pathway f o r the i n c o r p o r a t i o n of s u l f u r i n t o o r g a n i c geopolymers i s by reaction of HS with reactive s i t e s , e.g. o l e f i n i c double bonds, displaceable halogens (39), within sedimentary organic matter. The Michael addition reaction of HS to a c r y l i c acid may be used as a model case of such interactions. Addition of a specific -S-Scleaving reagent, tributylphosphine, to reducing marine sediments resulted i n a dramatic and r a p i d r e l e a s e of t h i o l s i n t o the porewater. The r e s u l t s showed that In the sediments s t u d i e d bound t h i o l s a r e present i n at least 20 times greater concentration than freely dissolved t h i o l s or d i s u l f i d e s . These results imply that another important route f o r the incorporation of sulfur into organic geopolymers may be binding of t h i o l s to reactive s i t e s (e.g., R-SH groups and metal ions) on p a r t i c l e s . The results of this i n i t i a l study indicate that t h i o l s play an a c t i v e r o l e i n the biogeochemica sediments (Figure 9). p a r t i c u l a r , how fast i s the turnover of t h i o l s i n sediments and what organisms are involved? What f r a c t i o n of sedimentary sulfur passes through the t h i o l pool? What are the precursors of the thiols? How do thiol-metal interactions affect the geochemistry (e.g. migration and binding) of heavy metals and t h i o l s i n sediments? How i s b i o t i c and abiotic production of t h i o l s i n porewaters related to the sulfur content and sulfur speciation within organic geopolymers? Acknowledgments We would l i k e to thank R. Cuhel, G.R. Harvey, and G.E. Luther f o r valuable input regarding possible formation routes f o r t h i o l s . F i n a n c i a l support was provided i n part by a grant from the National Institutes of Health (Biomedical Research Support Grant to K.M.) and from the National Science Foundation (OCE-8516020). Literature Cited

1. Balzer, W. In "Marine Organic Chemistry"; Duursma, E.K.; Dawson, R., Eds.; Elsevier: Amsterdam, 1981; Chap. 13. 2. Trudinger, P.A. Phil. Trans. Roy. Soc. 1982, B298, 563-581. 3. Zinder, S.H.; Doemel, W.N; Brock, T.D. Appl. Environ. Microbiol. 1977, 34, 859-860. 4. Altschuler, Z.S.; Schnepfe, M.M.; Silber, C.C.; Simon, F.O. Science 1983, 221, 221-227. 5. Boulegue, J.; Lord, C.J.; Church, T.M. Geochim. Cosmochim. Acta 1982, 46, 453-464. 6. Martin, T.H.; Hodgson, G.W. Chem. Geol. 1973, 12, 189-208. 7. Adams, D.D.; Richards, F.A. Deep-Sea Res. 1968, 15, 471-481. 8. Nissenbaum, Α.; Kaplan, I.R. Limnol. Oceanogr. 1972, 17, 570-582. 9. Dyrssen D.; Haraldsson, C.; Westerlund, S.; Aren, K. Mar. Chem., submitted. 10. Luther, G.W.; Church, T.M.; Giblin, A.E.; Howarth, R.W. In "Organic Marine Geochemistry"; Sohn, M., Ed.; ACS Symposium Series No. American Chemical Society: Washington, D.C., 1986; in press.

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

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11. Cullen, W.R.; McBride, B.C.; Reglinski, J. J. Inorg. Biochem. 1984, 21, 174-194. 12. Mopper, K.; Delmas, D. Anal. Chem. 1984, 56, 2558-2560. 13. Humphrey, R.E.; Potter, J.L. Anal. Chem. 1965, 37, 164-165. 14. Bird, R.P.; Moir, R.J. Aust. J. Biol. Sci. 1972, 25, 835-848. 15. Salsbury, R.L.; Merricks, D.L. Plant Soil 1975, 43, 191-209. 16. Zikakis, J.P.; Salsbury, R.L. J. Dairy Sci. 1969, 52, 2014-2019. 17. Zinder, S.H.; Brock, T.D. Appl. Environ. Microbiol. 1978, 35, 344-352. 18. Cooper, A.J.L. Ann. Rev. Biochem. 1983, 52, 187-222. 19. Bremner, J.M.; Steele, C.G. Adv. Microbial Ecol. 1978, 2, 155-201. 20. White, R.H. J. Mar Res. 1982, 40, 529-536. 21. Vairavamurthy, Α.; Andreae, M.O.; Iverson, R.L. Limnol. Oceanogr. 1985, 30, 59-70. 22. Cantoni, G.L.; Anderson 171-177. 23. Kadota, H.; Ishida, Y. Ann. Rev. Microbiol. 1972, 26, 127-138. 24. Wagner, C; Stadtman, E.R. Arch. Biochem. Biophys. 1962, 98, 331-336. 25. Aneja, V.P.; Overton, J.H., Jr.; Cupitt, J.T.; Durham, J.L.: Wilson, W.E. Tellus 1979, 31, 174-178. 26. Lehninger, A.L. "Biochemistry"; Worth: New York, 1975; 2nd Edition. 27. Maw, G.A.; du Vigneaud, V. J. Biol. Chem. 1948, 176, 1037-1045. 28. Wood, J.M.: Moura, I.; Moura, J.G.G.; Santos, M.H.; Xavier, Α.V.; LeGall, J.; Scandellari, M. Science 1982, 216, 303-305. 29. Naumann, E.; Fahlsbuch, K.; Gottschalk, G. Arch. Microbiol. 1984, 138, 79-83. 30. Tschech, Α.; Pfennig, N. Arch. Microbiol. 1984, 137, 163-167. 31. Noller, C.R. In "Textbook of Organic Chemistry"; W.B. Saunders: Philadelphia, 1966; 3rd Edition; p. 619. 32. Dahlbom, R. Acta. Chem. Scand. 1951, 5, 690-698. 33. Mopper, K.; Dawson, R.; Liebezeit, G.; Ittekkot, V. Mar. Chem. 1980, 10, 55-66. 34. King, G.M.; Klug, M.J. Appl. Environ. Microbiol. 1982, 44, 1308-1317. 35. Henrichs, S.M.; Farrington, J.W.; Lee, C. Limnol. Oceanogr. 1984, 29, 20-34. 36. Jørgensen, N.O.G.; Lindroth, P.; Mopper, K. Oceanolog. Acta 1981, 4, 465-474. 37. Hordijk, K.A.; Cappenberg, T.E. Appl. Environ. Microbiol. 1983, 46, 361-369. 38. Ansbaek, J.; Blackburn, T.H. Microb. Ecol. 1980, 5, 253-264. 39. Schwarzenbach, R.P.; Giger, W.; Schaffner, C.; Wanner, 0. Environ. Sci. Technol. 1985, 19, 322-327. RECEIVED

September 16, 1985

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

20 Speciation of Dissolved Sulfur in Salt Marshes by Polarographic Methods 1

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George W. Luther III , Thomas M . Church , Anne E. Giblin , and Robert W. Howarth 1

Chemistry-Physics Department, Kean College of New Jersey, Union, NJ 07083 College of Marine Studies, University of Delaware, Newark, D E 19716 Ecosystems Center, Marine Biological Laboratory, Woods Hole, M A 02543

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Polarographic techniques are capable of measuring a variety of sulfur species. These species include thiosulfate, sulfite polythionates sulfide organic sulphydryl group polysulfides. Al marsh porewaters as a result of sulfate reduction and the consequent oxidation of sulfide and sulfide minerals. Other wet and instrumental methods generally are not capable of measuring all of these sulfur species or distinguishing between these species. Sulfur speciation in the porewaters of two salt marshes (Great Marsh, Delaware and Great Sippewissett, Cape Cod, Massachusetts) are presented. A major finding is that the porewaters from Great Sippewissett salt marsh are dominated by inorganic sulfur species throughout the depth profile. However, Great Marsh, Delaware porewaters are dominated by organic sulphydryl species at millimolar concentrations from the surface to 12 cm and by inorganic sulfur species below 12 cm. Glutathione may be the thiol principally responsible for the field observations. The physical and geochemical characteristics of the two salt marshes differ widely and appear to be related to the differences in sulfur chemistry. There appears to be an interconversion between the inorganic and organic forms of sulfur in Great Marsh. Pyrite oxidation may be important to the formation of thiols. S u l f u r c a n form a number o f i n o r g a n i c and o r g a n i c s p e c i e s w i t h o x i d a t i o n s t a t e s v a r y i n g from -2 t o +6 and as a r e s u l t undergoes a v a r i e t y of biogeochemical transformations i n the e s t u a r i n e e n v i r o n ­ ment. Target compounds o r i o n s f o r study i n the d i s s o l v e d phase 0097-6156/ 86/0305-0340S06.00/ 0 © 1986 American Chemical Society

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

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are s u l f a t e , s u l f i d e , p o l y s u l f i d e [S(-2) and S ( 0 ) ] , t h i o s u l f a t e , s u l f i t e , p o l y t h i o n a t e s and o r g a n i c compounds such as t h i o l s . Most r e s e a r c h over t h e l a s t s e v e r a l y e a r s has shown t h a t s u l f u r s p e c i e s w i t h i n t e r m e d i a t e o x i d a t i o n s t a t e s a r e p r e s e n t i n porewaters i n s u b s t a n t i a l q u a n t i t i e s and a r e i m p o r t a n t t o many b i o g e o c h e m i c a l processes Q-8). I n p a r t i c u l a r , t h e p a r t i a l l y o x i d i z e d forms o f s u l f u r may be produced bv^ a v a r i e t y of r e a c t i o n s i n c l u d i n g t h e o x i d a t i o n of hydrogen suifideÇl,2), t h e r e d u c t i v e d i s s o l u t i o n o f g o e t h i t e ( 3 ) , the o x i d a t i o n of s u l f i d e m i n e r a l s ( 4 ) and m i c r o b i a l p r o c e s s e s ( 5 ) . I n o r g a n i c p o l y s u l f i d e s a r e i m p o r t a n t t o metal c y c l i n g ( j ) ) and t o p y r i t e f o r m a t i o n Q ) . T h i o s u l f a t e as w e l l as p o l y s u l f i d e s have been l i n k e d t o energy e x p o r t i n s a l t marsh ecosystems(8-10). The f o r m a t i o n of o r g a n i c s u l f u r compounds i n s a l t marsh porewaters i s n o t as w e l l understood(11) as t h e i n o r g a n i c m o i e t i e s a l t h o u g h p r o g r e s s has been made i n c o a s t a l marine s e d i m e n t s ( 1 2 ) . T h e i r presence as t h i o l g e n e r a l l y i n t r a c e amounts(12-16) o r g a n i c s u l f u r compounds t o atmospheric s u l f u r e m i s s i o n s i s p r e s e n t l y an a r e a of i n t e n s e r e s e a r c h ( 1 4 , 1 5 ) . Less appears t o be known about o r g a n i c s u l f u r compounds i n s a l t marsh p o r e w a t e r s . T r a d i t i o n a l t e c h n i q u e s t o measure d i s s o l v e d s u l f u r i n marine porewaters a r e i o d o m e t r i c t i t r a t i o n s and c o l o r i m e t r i c methods based on methylene b l u e c o l o r development. However, these methods(17-19) are n o t c a p a b l e o f measuring a wide v a r i e t y o f s u l f u r s p e c i e s o r d i s t i n g u i s h i n g between s u l f u r s p e c i e s . Major s u l f u r s p e c i e s a r e d e f i n e d as those w i t h c o n c e n t r a t i o n s t y p i c a l l y g r e a t e r than 10 uM. I o d o m e t r i c t i t r a t i o n s can determine s u l f u r i n -1 and -2 o x i d a t i o n s t a t e s as shown i n e q u a t i o n s ( 1 ) through ( 4 ) . However, these t i t r a t i o n s cannot d i s t i n g u i s h between a l l of t h e v a r i o u s forms.

2

S/;

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Thus, i o d o m e t r i c t i t r a t i o n s a r e l i m i t e d t o t h e a n a l y s i s o f pure s t a n d a r d s . The p o p u l a r methylene b l u e c o l o r i m e t r i c t e c h n i q u e s o f C l i n e ( 1 7 ) and G i l b o a - G a r b e r ( 1 8 ) o n l y measure i n o r g a n i c s u l f i d e and not o r g a n i c s u l f u r compounds. UV-VIS s p e c t r o s c o p y can measure a number o f o r g a n i c and i n o r g a n i c s u l f u r compounds but many o f t h e s e compounds have o v e r l a p p i n g peaks and thus cannot be d i s t i n g u i s h e d . I n o r g a n i c and o r g a n i c s u l f u r can be determined by a Raney n i c k e l r e d u c t i o n of many s u l f u r compounds f o l l o w e d by c o l o r i m e t r i c

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measurement o f t h e i n o r g a n i c s u l f i d e formed(19). However, t h i s method cannot d i s t i n g u i s h t h e forms o f s u l f u r r e a d i l y . Therefore, q u a n t i t a t i v e a n a l y s i s o f a l l major s u l f u r compounds i s d i f f i c u l t a t best w i t h these methods. To date o n l y two methods have been a b l e t o g i v e a r a t h e r complete s p e c i a t i o n o f major s u l f u r s p e c i e s i n s a l t marsh p o r e w a t e r s . F i r s t , Boulegue e t a l ( 2 0 , 2 1 ) have used e l e c t r o c h e m i c a l t i t r a t i o n s w i t h UV-VIS s p e c t r o p h o t o m e t r y t o determine o r g a n i c and i n o r g a n i c s u l f u r s p e c i e s i n Great Marsh, Delaware. The t i t r a t i o n s y i e l d s p e c i f i c i n f o r m a t i o n on i n o r g a n i c s u l f i d e S ( - 2 ) , s u l f i t e , t h i o s u l f a t e and p o l y s u l f i d e s and g e n e r a l i n f o r m a t i o n on o r g a n i c compounds. The major drawback t o these t i t r a t i o n s i s t h a t they a r e t e d i o u s . The method a l s o uses UV-VIS s p e c t r o p h o t o m e t r y t o determine t h i o l s and p o l y s u l f i d e s and t o check on i n o r g a n i c s p e c i e s which a r e b e t t e r determined by e l e c t r o c h e m i c a l t i t r a t i o n s . The a n a l y s i s o f i n o r g a n i c and o r g a n i c compounds by UV-VIS s p e c t r o p h o t o ­ metry i s c o m p l i c a t e d by Secondly, Luther e to measure i n o r g a n i c s u l f u r s p e c i a t i o n i n a New England s a l t marsh. T h i o s u l f a t e , s u l f i t e , i n o r g a n i c S(-2) (as p o l y s u l f i d e and s u l f i d e ) and S ( 0 ) p o l y s u l f i d e s were measured. P o l y t h i o n a t e s and t h i o l s were not determined a l t h o u g h each r e a c t a t t h e mercury e l e c t r o d e ( 2 2 , 2 3 ) . The o b j e c t i v e s o f t h i s paper a r e ( 1 ) t o show t h e u s e f u l n e s s o f p o l a r o g r a p h i c t e c h n i q u e s i n d e t e r m i n i n g o r g a n i c s u l f u r and i t s l i k e l y s t r u c t u r e ( s ) , ( 2 ) t o show t h a t p o l a r o g r a p h i c t e c h n i q u e s can p r o v i d e r o u t i n e f i e l d d a t a and ( 3 ) t o compare t h e c h e m i s t r y of major s u l f u r s p e c i e s i n s a l t marsh porewaters from two d i f f e r e n t s a l t marshes - Great Marsh, Delaware and t h e Great S i p p e w i s s e t t Marsh, Cape Cod, M a s s a c h u s e t t s . Experimental Reagents. I o d i n e and t h i o s u l f a t e s t a n d a r d s o l u t i o n s were purchased from F i s h e r S c i e n t i f i c Co.. Sodium s u l f i d e was purchased from A l f a P r o d u c t s and was checked f o r p u r i t y by d i f f e r e n t i a l s c a n n i n g c a l o r i m e t r y (DSC), X-ray d i f f r a c t i o n (XRD) and p o l a r o g r a p h i c methods. F i n a l s t a n d a r d i z a t i o n was by i o d o m e t r i c methods. Pure sodium p o l y s u l f i d e s were prepared and s t a n d a r d i z e d as p r e v i o u s l y described(22). Glutathione(GSH), o x i d i z e d g l u t a t h i o n e , L-cysteine * HC1, D L - p e n i c i 1 1 a m i n e , L - c y s t i n e , D - p e n i c i l l a m i n e d i s u l f i d e , 2-mercaptoethylamine, 3 - m e r c a p t o p r o p r i o n i c a c i d and mercaptos u c c i n i c a c i d were purchased from Sigma Chemical Co.. Methane­ t h i o l , e t h a n e t h i o l , 1 , 2 - e t h a n e d i t h i o l and 2-mercaptoethanol were purchased from Eastman Kodak Co.. The t h i o l s were s t a n d a r d i z e d by i o d o m e t r i c methods. I n t h e case o f m e r c a p t o s u c c i n i c a c i d , i o d o m e t r i c t i t r a t i o n s y i e l d e d 1.3 t h i o l groups p e r f o r m u l a weight r a t h e r than t h e expected 1.0 i n d i c a t i n g an impure sample. The d i s u l f i d e s were used w i t h o u t f u r t h e r p u r i f i c a t i o n . A l l s o l u t i o n s were prepared w i t h deoxygenated and d e i o n i z e d water i n a n i t r o g e n f i l l e d g l o v e bag o r by u s i n g S c h l e n k type apparatus. Apparatus.

Polarograms were r e c o r d e d w i t h a P r i n c e t o n A p p l i e d

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

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Research (PAR) model 174A or 364 system with a model 303 s t a t i c mercury drop electrode (SDME). The SDME c e l l assembly was modified for a SCE reference electrode as described previously(22). Prepurified argon was used to purge the c e l l assembly. Linear Sweep Voltammetry (LSV) was performed at a 50 or 100 mV/s scan rate from 0 to -1.5 V using the SDME i n the hanging mercury drop electrode mode (HMDE). D i f f e r e n t i a l pulse polarography (DPP) and sampled DC polarography (SDC) were performed with a 2 or 5 mV/s scan rate from 0 to -1.5V and a one s drop time for the SDME i n the dropping mercury electrode mode. F i e l d sampling. Marsh cores from Great Sippewissett Marsh, Massachusetts were taken near the eastern most s i t e and i n the short Spartina zone as described i n G i b l i n and Howarth(24). Cores were taken i n August, 1984 at the beginning of senescence. Marsh cores from Great Marsh, Delaware were taken i n June and August 1984 at the s i t e described i handled i n a nitrogen f i l l e cores were sectioned i , presse Reeburg squeezer and f i l t e r e d as previously described(10,25). The f i l t e r e d samples were placed into gas tight syringes u n t i l ready for s p l i t t i n g and analysis. Measurements of pH were made on aliquots of these samples. Sulfur a n a l y t i c a l scheme. The polarographic analysis of many of the major sulfur species which are found i n porewaters has been described i n d e t a i l by Luther et al(22). Tables I and II show the relevant reactions of sulfur species at the mercury electrode. Sulfur species are quantified by the method of standard additions. B r i e f l y , the samples are s p l i t i n the following manner. The f i r s t subsample (5 mL) i s analyzed by LSV or DPP to determine thiosulfate, tetrathionate, and s u l f i t e . A l l samples are a c i d i f i e d with 1M HCL (degassed) to a pH of 5 and then purged to remove s u l f i d e . This step i s necessary to determine s u l f i t e . Replicate measurements are always precise to ±5% and are frequently precise to +1%· The second subsample (2 to 5 mL) i s placed i n an ampoule and spiked with an excess of freshly prepared 0.01 M sodium s u l f i t e and covered with a septum. The ampoule i s l a t e r sealed under nitrogen and heated to 60°C for 2 hours. S u l f i t e reacts with inorganic zerovalent p o l y s u l f i d e , S(0), to form thiosulfate. Thiosulfate i s measured again by LSV or DPP. The difference between the values of thiosulfate i n this subsample and the f i r s t subsample equals the t o t a l S(0) from p o l y s u l f i d e s . A third subsample (25 uL to 500 uL) i s added to 5 mL of a' pH 10 buffer of 0.2 M nitrate/0.2 M bicarbonate as described previously(22,23). This solution i s analyzed by SDC for t h i o l s , d i s u l f i d e s , inorganic S(-2) and inorganic polysulfide S(0). Figure 1 shows the anodic wave for a t h i o l and inorganic S(-2) (negative current) and the cathodic wave for inorganic polysulfide S(0) (positive current) i n two separate f i e l d samples from Great Marsh, Delaware. Figure 2 shows the anodic wave for glutathione and the cathodic wave for i t s d i s u l f i d e i n the pH 10 buffer.

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

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•

-0.5

-1.0

F i g u r e 1. SDC p o l a r o g r a p h i c waves f o r two f i e l d samples from Great Marsh, Delaware.

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F i g u r e 2. SDC polarogram o f g l u t a t h i o n e and o x i d i z e d g l u t a t h i o n e prepared by adding i o d i n e t o g l u t a t h i o n e .

In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

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Speciation of Dissolved Sulfur

L U T H E R ET AL.

S u l f a t e and c h l o r i d e i o n were measured by i o n chromatography u s i n g a Dionex model 20101 system on samples from Great S i p p e w i s s e t t Marsh. On samples from Great Marsh, s u l f a t e i o n was determined g r a v i m e t r i c a l l y as BaSO^ and c h l o r i d e i o n was determined by an a r g e n t o m e t r i c Mohr t i t r a t i o n . R e s u l t s and D i s c u s s i o n Methods. I n a r e c e n t s t u d y ( 2 2 ) , p o l a r o g r a p h y was used t o determine i n o r g a n i c s u l f u r s p e c i e s i n marine porewaters as i n Tables I and II. I n t h a t s t u d y , no t h i o l s o r o r g a n i c p o l y s u l f i d e s were d e t e c t e d

T a b l e I . O x i d a t i o n r e a c t i o n s a t t h e mercury e l e c t r o d e .

(1) 2 S 0 3 ~

+

Hg

>

(2)

2 SO3"

+

Hg

>

Hg(S0 ) "

(3)

SH"

+

Hg

>

HgS

+

Hg

>

HgS

Hg

>

(RS) Hg

2

(4)

S^~

+

+

+

2

H

+

2e~

+

(x-l)S

+

= -0.60 V

2e~

Ε

χ/2

=

+ 2e~

E

l/2

=

"°·

f o r (1) and (2) a r e f o r 0.01 mM s o l u t i o n s i n 0.60 M NaCl.

2

+ 2 e"" E ^