Organic Marine Geochemistry - American Chemical Society

9 Structural Interrelationships among Humic Substances in Marine and Estuarine Sediments 13

As Delineated by Cross-Polarization/Magic Angle Spinning C NMR Patrick G. Hatcher and William H . Orem

Downloaded by UNIV OF PITTSBURGH on June 21, 2013 | http://pubs.acs.org Publication Date: April 21, 1986 | doi: 10.1021/bk-1986-0305.ch009

U.S. Geological Survey, Reston, VA 22092

Nuclear magnetic resonance studies of the s t r u c t u r a l composition of humic substances in marine and estuarine sediments have p r o v i d e d a w e a l t h of i n f o r m a t i o n regarding the mode of formation for these macromolecular organic substances. The NMR data show that humic acids are highly aliphatic in nature. The aliphatic structures are thought to be derived from macromolecular residues of algae and other micro-organisms and have a high degree of branching and cross-linking. Fulvic acids, the most soluble of the humic substances, are generally unlike their less soluble counterparts, humic acids and humin, i n that they appear to be mostly composed of carbohydrates and/or polyuronic acids. The i n t e r r e l a tionships among f u l v i c acids, humic acids, and humin in a variety of marine and estuarine sediments suggests that humin is the parent material from which humic and f u l v i c acids are formed. The pathway for this formation appears to be oxidative, either chemical or biological oxidation. F u l v i c acids are metabolic products of b a c t e r i a l degradation of plant remains, whereas humic acids appear to be oxidized s t r u c t u r a l equivalents of the macromolecular i n s o l u b l e humin i n sediments receiving most of their contibutions from algal or micr o b i a l biomass. This humin probably originates from primary macromolecular structures i n algae and/or bacteria and is concentrated in sediments by a process of selective preservation during early diagenesis. Humin from some coastal marine and estuarine sediments appears to contain a significant proportion of refractory, coal-like materials. In these sediments, humic acids bear no structural relationship to the humin. The use of nuclear magnetic resonance spectroscopy for s t r u c t u r a l studies of humic substances has become commonplace since some of the This chapter not subject to U.S. copyright. Published 1986, American Chemical Society

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

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e a r l y work of V i l a and o t h e r s (1), Stuermer and Payne ( 2 ) , W i l s o n and Goh 03), and H a t c h e r and o t h e r s ( 4 ) . T h e s e e a r l y s t u d i e s r e l i e d on s o l u t i o n H and C NMR t o d e r i v e s t r u c t u r a l i n f o r m a t i o n on humic s u b s t a n c e s , p r i m a r i l y humic and f u l v i c a c i d s , t h a t are s o l u b l e i n a s u i t a b l e s o l v e n t , u s u a l l y 0.5 Ν NaOD. The development of a t e c h n i q u e t h a t was c a p a b l e o f e x a m i n i n g s o l i d s , s o l i d - s t a t e ^ C NMR u s i n g c r o s s p o l a r i z a t i o n w i t h m a g i c - a n g l e s p i n n i n g (CPMAS), p r o v i d e d an o p p o r t u n i t y t o not o n l y examine s o l u b l e humic substances but a l s o the i n s o l u b l e humin (5.-JL) and w h o l e s o i l (9-11). Such a c a p a b i l i t y has f o r the f i r s t time a l l o w e d f o r d i r e c t c h e m i c a l s t r u c t u r a l comparisons b e t w e e n t h e v a r i o u s h u m i c f r a c t i o n s i n m a r i n e and e s t u a r i n e s e d i ments. Some of these comparisons were made e a r l i e r f o r marine s e d i ments (6). T h i s paper p r o v i d e s new d a t a f o r e s t u a r i n e sediments and attempts t o p r o v i d e a more c o m p l e t e a n a l y s i s of the s t r u c t u r a l i n t e r relationships. S o l i d - s t a t e ^ C NMR i s the method of c h o i c e i n t h i s study f o r a number of reasons. F i r s t , the method i s not l i m i t e d by s o l u b i l i t y , a l l o w i n g i n t e r c o m p a r i s o n s among a l l h u m i c i s o l a t e s i n c l u d i n g t h e i n s o l u b l e humin. We f e l t i t important t h a t humin be c o m p a r a t i v e l y examined because our p r e v i o u s s t u d i e s (7_, 8) have suggested t h a t t h i s humic f r a c t i o n may be the p r e c u r s o r from w h i c h humic a c i d s o r i g i n a t e . Second, the CPMAS t e c h n i q u e i s more s e n s i t i v e and p r o v i d e s a spectrum we f e e l i s more r e p r e s e n t a t i v e of carbon s t r u c t u r e s than s o l u t i o n C NMR. F i n a l l y , the s t r u c t u r a l i n f o r m a t i o n o b t a i n e d by NMR i s f a r more u s e f u l f o r i n t e r c o m p a r i s o n p u r p o s e s t h a n t h a t o b t a i n e d f r o m many o t h e r o r g a n i c g e o c h e m i c a l m e t h o d s s u c h as i n f r a r e d s p e c t r o s c o p y , p y r o l y s i s / g a s chromatography/mass s p e c t r o m e t r y (Py/GC/MS), e l e m e n t a l a n a l y s i s , and o t h e r s . The s p e c t r a l d a t a p r o v i d e s a s t r i k i n g v i s u a l p r e s e n t a t i o n t h a t e n a b l e s r a p i d s t r u c t u r a l i n t e r c o m p a r i s o n s among humic f r a c t i o n s . Though the d a t a cannot p r o v i d e d e t a i l e d d i s c r i m i n a t i o n a t the m o l e c u l a r l e v e l l i k e Py/GC/MS and s i m i l a r t e c h n i q u e s , major s t r u c t u r a l d i f f e r e n c e s a r e r e a d i l y d i s c e r n a b l e w i t h NMR. When used i n c o m b i n a t i o n w i t h o t h e r o r g a n i c g e o c h e m i c a l t e c h n i q u e s , C NMR becomes a p o w e r f u l t o o l f o r c h e m i c a l s t r u c t u r a l d e t e r m i n a t i o n s . 1


NMR

1 3

1J

Methods Humic and f u l v i c a c i d s as w e l l as h u m i n w e r e i s o l a t e d f r o m t h e s a m p l e s d e s c r i b e d i n T a b l e I by s t a n d a r d m e t h o d s (6_). I n s h o r t , humic and f u l v i c a c i d s a r e e x t r a c t e d w i t h 0.5 Ν NaOH under Humic a c i d s a r e p r o t o n a t e d on an i o n e x c h a n g e r e s i n , p r e c i p i t a t e d by a c i d i f y i n g t o pH 2, s e p a r a t e d by c e n t r i f u g a t i o n , and l y o p h i l y z e d . The s o l u b l e f u l v i c a c i d s a r e c o n c e n t r a t e d by u l t r a f i l t r a t i o n and lyophilyzed. Humin, t h e r e s i d u e a f t e r t r e a t m e n t w i t h NaOH, i s t r e a t e d w i t h c o n c e n t r a t e d HC1:HF t o r e m o v e a l a r g e p o r t i o n o f t h e m i n e r a l m a t t e r and h y d r o l y z a b l e s u b s t a n c e s s u c h as p r o t e i n s and polysaccharides· D r i e d h u m i c s u b s t a n c e s were a n a l y z e d by p l a c i n g them i n a b u l l e t - t y p e r o t o r machined from K e l - F . CPMAS C NMR s p e c t r a were o b t a i n e d on a Chemagnetics CMC 100S/200L spectrometer o p e r a t i n g at a f i e l d s t r e n g t h o f 2.35 T e s l a . A p p r o x i m a t e l y 10,000 - 50,000 s c a n s w e r e o b t a i n e d w i t h a 1 s d e l a y and 1 ms c o n t a c t t i m e . Spinning speeds of 3 t o 3.5 kHz were a c h i e v e d t o m i n i m i z e s p i n n i n g sidebands. 1 3


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T a b l e I . Sample l o c a t i o n s and d e s c r i p t i o n s


Sample Name

L o c a t i o n and D e s c r i p t i o n

Mangrove Lake

Samples c o l l e c t e d i n Mangrove Lake, Bermuda, a s m a l l m a r i n e l a k e l o c a t e d o n the n o r t h e a s t e r n c o r n e r of t h e i s l a n d . A c o r e (5.5m i n depth) of t h e o r g a n i c r i c h s a p r o p e l a t t h e bottom o f t h e l a k e was o b t a i n e d .

Potomac R i v e r ( f l u v i a l )

Sample o f humic a c i d was o b t a i n e d from G. Diachenko (U.S. Department o f A g r i c u l t u r e ) . S e d i m e n t was c o l l e c t e d a t P o i n t o f Rocks, M a r y l a n d , i n t h e Potomac R i v e r .

Potomac R i v e r ( e s t u a r i n e ) Samples were c o l l e c t e d a t the mouth o f the Potomac R i v e r n e a r P i n e y P o i n t , M a r y l a n d . A 1-m c o r e was o b t a i n e d . New Y o r k B i g h t

Samples were c o l l e c t e d on t h e C o n t i n e n t a l S h e l f , 10 n a u t i c a l m i l e s s o u t h e a s t of Rockaway P o i n t , New York.

Hudson Canyon

Samples were c o l l e c t e d a t t h e head o f t h e H u d s o n C a n y o n i n the New Y o r k B i g h t 100 n a u t i c a l m i l e s e a s t o f Rockaway P o i n t , New Y o r k , i n 266m o f water.

W a l v i s Bay

Samples were c o l l e c t e d on t h e C o n t i n e n t a l S h e l f , W a l v i s Bay, Namibia (South West A f r i c a ) i n 846m o f w a t e r . S u r f a c e sediment was c o l l e c t e d on C r u i s e AII-93-3 of t h e A t l a n t i s I I i n 1975 by J.W. F a r r i n g t o n (Woods H o l e Océanographie Institution).

Georgia s o i l

S u r f i c i a l s o i l sample was c o l l e c t e d from a f a l l o w a g r i c u l t u r a l f i e l d near Kingsland, Georgia.


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Results F u l v i c acids. M a r i n e sedimentary humic substances s o l u b l e i n base and a c i d ( f u l v i c a c i d s ) have p r e v i o u s l y been examined by *H and ^ C NMR (12). The dominant s t r u c t u r a l components were p o s t u l a t e d t o be p o l y s a c c h a r i d e - l i k e substances, probably p o l y u r o n i c a c i d s . Solidstate C NMR s p e c t r a o f f u l v i c a c i d s i s o l a t e d f r o m a number o f marine and e s t u a r i n e sediments a r e shown i n F i g u r e 1. M a j o r peaks a t 72 and 106 ppm b e t r a y t h e o v e r w h e l m i n g presence o f p o l y s a c c h a r i d e l i k e s u b s t a n c e s , a n d , a s shown b y H a t c h e r a n d o t h e r s ( 1 2 ) , t h e moderate peak f o r c a r b o x y l o r amide carbon a t 175 ppm suggests t h a t these p o l y s a c c h a r i d e s a r e more l i k e p o l y u r o n i d e s . A r o m a t i c carbons (110 t o 160 ppm) a r e d e c i d e d l y minor components. A l i p h a t i c carbons (0-50 ppm) a r e a l s o m i n o r c o m p o n e n t s . *H NMR s p e c t r a shown by H a t c h e r and o t h e r s (12) i n d i c a t e t h a t these a l i p h a t i c s t r u c t u r e s a r e h i g h l y branched. I t i s n o t e w o r t h y t h a t f u l v i c a c i d s f r o m a e r o b i c and a n a e r o b i c sediments and from o f f s h o r e marine and e s t u a r i n e sediments a l l have


1,3

ι ο A J

similar C NMR s p e c t r a . The a b u n d a n c e o f p o l y s a c c h a r i d e s and structural s i m i l a r i t y i n t h i s f r a c t i o n precludes attempts t o c o r r e l a t e s o u r c e s o f s e d i m e n t a r y o r g a n i c m a t t e r on t h e b a s i s o f s t r u c t u r a l d i f f e r e n c e s . The u n i f o r m s t r u c t u r a l c h a r a c t e r a l s o suggests t h a t t h e p r o c e s s l e a d i n g t o t h e p r o d u c t i o n o f f u l v i c a c i d s i s u b i q u i t o u s . I f p o l y u r o n i d e s a r e t h e l i k e l y s t r u c t u r a l components of f u l v i c a c i d s , then i t i s l i k e l y t h a t these components d e r i v e from a l g a l o r m i c r o b i a l remains known t o be e n r i c h e d i n p o l y u r o n i d e s . The c l a s s i c a l d e f i n i t i o n o f f u l v i c a c i d s i s n o t v e r y s p e c i f i c . Many b i o c h e m i c a l substances such as p r o t e i n s , sugars, and f a t t y a c i d s w o u l d f a l l u n d e r t h i s c l a s s i f i c a t i o n . T h e s e s u b s t a n c e s , i n many i n s t a n c e s , c a n h a r d l y be c o n s i d e r e d " h u m i c " i n n a t u r e . B u t , i f one uses t h e c l a s s i c a l d e f i n i t i o n o f f u l v i c a c i d s these substances a r e i n c l u d e d . No doubt t h e o b s e r v a t i o n s made above t h a t p o l y s a c c h a r i d e l i k e s u b s t a n c e s c o n s t i t u t e the major components o f sedimentary f u l v i c acids i s p a r t l y a t t r i b u t a b l e t o the fact that the operational d e f i n i t i o n c l a s s e s p o l y u r o n i d e s as f u l v i c a c i d s . I t i s n o t t h e i n t e n t of t h i s paper t o d i s c u s s t h e m e r i t s o f u s i n g t h e c l a s s i c a l o p e r a t i o n a l d e f i n i t i o n f o r f u l v i c a c i d s a s o p p o s e d t o one's p e r c e p t i o n o f what t r u e f u l v i c a c i d s a r e . We know f a r t o o l i t t l e a b o u t t h e c o m p o s i t i o n o f h u m i c i s o l a t e s and a b o u t t h e i r o r i g i n t o b e g i n d i s c u s s i o n s o f whether they a r e h u m i f i e d o r not. We t h e r e f o r e chose t o use o p e r a t i o n a l d e f i n i t i o n w i t h r e c o g n i t i o n t h a t w e l l d e f i n e d s t r u c t u r a l e n t i t i e s c a n s o m e t i m e s be a p a r t o f what i s isolated. Humic a c i d s . CPMAS ^ NMR s p e c t r a o f r e p r e s e n t a t i v e m a r i n e and e s t u a r i n e humic a c i d s a r e shown i n F i g u r e 2 . S o l u t i o n *H and NMR and s o l i d s t a t e NMR s p e c t r a o f m a r i n e s e d i m e n t a r y h u m i c a c i d s have p r e v i o u s l y been d e s c r i b e d by H a t c h e r and o t h e r s (4) and Dereppe and o t h e r s (13). These s p e c t r a showed t h a t marine sedimentary humic a c i d s a r e p r e d o m i n a n t l y composed o f p a r a f f i n i e s t r u c t u r e s t h a t have a r e l a t i v e l y h i g h d e g r e e o f b r a n c h i n g , compared t o l o n g - c h a i n a l k y l structures. Aromatic s t r u c t u r e s a r e g e n e r a l l y d e p l e t e d i n m a r i n e h u m i c a c i d s whose s o u r c e i s p r e d o m i n a n t l y f r o m a l g a l o r m i c r o b i a l detritus.


ORGANIC MARINE GEOCHEMISTRY


Potomac R i v e r (estuarine)

Hudson Canyon

I ' ' ' ' I • • • • ι • • • • ι • • • • ι • • • • ι ' • ' ' I ' ' ' ' I ' '

300

200

100

0

ppm

Paraffinic-C Carbohydrate/Ether-C • •H

·

Aromatic-C

Carboxyl/Amide-C

Aldehyde/Ketone-C 1 3

F i g u r e 1. R e p r e s e n t a t i v e CPMAS C NMR s p e c t r a o f f u l v i c from marine and e s t u a r i n e sediments.


acids


HATCHER AND OREM

Potomac R i v e r


Potomac R i v e r

(fluvial)

(estuarine)

New York B i g h t

W a l v i s Bay

Mangrove Lake ( s u r f i c i a l )

Mangrove Lake (4m depth)

• · • · · · · * ' ' ' 1 ' ' ' ' I 1

300

200

1 1

' ' I ' ' ' ' I ' ' ' ' I " " I •

100

0

1 1

•—· •—'

1

ρριτ

ParaffWc-C

Carbohydrate/Ethor-C Aroma tlc-C

Carboxyl/AmWe-C

AkJehyde/Ketone-C 1 3

F i g u r e 2. R e p r e s e n t a t i v e CPMAS C NMR s p e c t r a o f h u m i c a c i d from marine and e s t u a r i n e sediments.

American Chemical Society Library

1155 16th

St., N.W.

D.C. 20036

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


148


The spectrum o f humic a c i d from an a l g a l s a p r o p e l from Mangrove L a k e (4m d e p t h ) shown i n F i g u r e 2 i s c h a r a c t e r i s t i c o f s u c h m a r i n e humic a c i d s . Note t h e strong signals for paraffinic, c a r b o h y d r a t e / e t h e r , a n d c a r b o x y l / a m i d e c a r b o n s a t 30, 72, a n d 175 ppm, r e s p e c t i v e l y . C a r b o h y d r a t e s h a v e b e e n shown t o be p r e s e n t i n humic a c i d i s o l a t e s , p r o b a b l y e x i s t i n g a s u r o n i c - a c i d - 1 i k e carbohydrates (4). The s p e c t r u m o f h u m i c a c i d s f r o m s u r f i c i a l sediments i n Mangrove Lake ( F i g u r e 2) shows a g r e a t e r p r o p o r t i o n o f c a r b o h y d r a t e s i g n a l s , p r o b a b l y representing b i o l o g i c a l degradation p r o d u c t s from e a r l y d i a g e n e t i c r e a c t i o n s . H a t c h e r and o t h e r s (7) and S p i k e r a n d H a t c h e r (14) showed t h a t e a r l y d i a g e n e s i s l e a d s t o t h e d e g r a d a t i o n and r e m o v a l o f c a r b o h y d r a t e s i n Mangrove Lake s a p r o p e l . Presumably, these degraded o r p a r t i a l l y degraded c a r b o h y d r a t e s c o u l d become i n c o r p o r a t e d i n h u m i c a c i d i s o l a t e s , e s p e c i a l l y i f t h e y c o n t a i n c a r b o x y l f u n c t i o n a l g r o u p s . Y i e l d s o f humic a c i d s from Mangrove Lake sediments a r e l o w (2%); thus i t i s l i k e l y that carbohydrates o r u r o n i c a c i d - l i k e carbohydrates, u s u a l l y a major f r a c t i o n of the t o t a l sapropel i n s u r f i c i a l l a y e r s , a r e being i n c o r p o r a t e d i n t o h u m i c a c i d i s o l a t e s . The c a r b o h y d r a t e s a r e most l i k e l y i n c o r p o r a t e d i n humic a c i d s from Mangrove Lake because the s a p r o p e l i s i n i t s i n i t i a l stages o f d i a g e n e s i s and, as such, s t i l l c o n t a i n s s i z e a b l e q u a n t i t i e s o f c a r b o h y d r a t e s (7.). A t depth, where the s a p r o p e l has been d i a g e n e t i c a l l y a l t e r e d f u r t h e r , c a r b o h y d r a t e s are m i n o r components o f humic a c i d s , whereas t h e p a r a f f i n i c s t r u c t u r e s , a l l u d e d t o above, are dominant. A s s o c i a t e d w i t h the p a r a f f i n i c s t r u c t u r e s a r e c a r b o x y l / a m i d e g r o u p s ( 1 7 5 ppm) a n d a l c o h o l i c / e t h e r i c g r o u p s o t h e r t h a n c a r b o h y d r a t e s (70 ppm). Note a l s o t h a t a s m a l l p e a k i s o b s e r v e d a t a b o u t 50 ppm. P e a k s i n t h i s r e g i o n a r e u s u a l l y a s s i g n e d t o m e t h o x y 1 o r amino g r o u p s . B e c a u s e m e t h o x y l carbons i n humic a c i d s are u s u a l l y a s s o c i a t e d w i t h a r o m a t i c s t r u c t u r e s (from l i g n i n - l i k e substances) and because c o n t r i b u t i o n s o f a r o m a t i c , l i g n i n - d e r i v e d components a r e l a c k i n g i n Mangrove Lake, t h e peak a t 50 ppm i s p r o b a b l y t h a t o f amino groups. The e l e m e n t a l d a t a w h i c h i n d i c a t e a p p r o x i m a t e l y 4 t o 5 p e r c e n t n i t r o g e n i n t h e s e humic a c i d s (7) a r e i n a c c o r d w i t h t h i s assignment. Solid-state C NMR s p e c t r a o f humic a c i d s from o t h e r m a r i n e and e s t u a r i n e sediments ( F i g u r e 2) show peaks i n s i m i l a r r e g i o n s as t h o s e noted f o r the Mangrove Lake humic a c i d s , but the r e l a t i v e i n t e n s i t i e s v a r y c o n s i d e r a b l y . Most m a r i n e and e s t u a r i n e humic a c i d s c o n t a i n few c a r b o h y d r a t e - l i k e s t r u c t u r e s , a s t h e p e a k s f o r c a r b o h y d r a t e s a t 72 and 106 ppm are minor. T h i s p r o b a b l y i s because these sediments a r e more a d v a n c e d d i a g e n e t i c a l l y t h a n t h o s e f r o m M a n g r o v e L a k e . The y i e l d s o f humic a c i d s a r e g r e a t e r than t h o s e from Mangrove Lake (6) and i t i s l i k e l y t h a t l e s s e x t r a c t a b l e c a r b o h y d r a t e - l i k e m a t e r i a l from undegraded p l a n t d e t r i t u s has been i n c o r p o r a t e d . The content o f aromatic carbon v a r i e s c o n s i d e r a b l y i n m a r i n e and e s t u a r i n e humic a c i d s , but i s , i n a l l c a s e s , g r e a t e r t h a n t h a t o f Mangrove Lake humic a c i d s . T h i s i s p r o b a b l y a r e f l e c t i o n o f t h e g r e a t e r c o n t r i b u t i o n o f v a s c u l a r p l a n t - d e r i v e d m a t e r i a l w h i c h can be expected t o provide l i g n i n - l i k e components r i c h i n a r o m a t i c s t r u c t u r e s . Note t h a t the humic a c i d s from f l u v i a l sediments o f t h e Potomac R i v e r a r e t h e most a r o m a t i c . P e a k s a t 150 a n d 55 ppm a r e c h a r a c t e r i s t i c of oxygen-substituted aromatic carbons t y p i c a l l y a s s o c i a t e d w i t h l i g n i n o f v a s c u l a r p l a n t s . Humic a c i d s from New Y o r k



9.

HATCHER AND

OREM

NMR

Structural Studies of Humic Substances

149

B i g h t s e d i m e n t s ( F i g u r e 2) a l s o c o n t a i n c o n s i d e r a b l e q u a n t i t i e s o f l i g n i n - d e r i v e d s t r u c t u r e s , as e x p e c t e d , because l a r g e q u a n t i t i e s o f sewage s l u d g e and dredge s p o i l s are b e i n g dumped a t the s i t e . Sediment s from W a l v i s Bay, a c o a s t a l u p w e l l i n g zone o f f t h e west c o a s t o f A f r i c a , and e s t u a r i n e muds f r o m t h e l o w e r P o t o m a c R i v e r c o n t a i n h u m i c a c i d s t h a t show l e s s e r p r o p o r t i o n s o f aromatic s t r u c t u r e s t h a n those mentioned above. T h e i r NMR s p e c t r a ( F i g u r e 2) v e r y n e a r l y approximate t h o s e of m a r i n e a l g a l o r m i c r o b i a l d e t r i t u s (Mangrove Lake s a p r o p e l ) . The c a r b o h y d r a t e s i g n a l s (72 ppm) a r e l e s s , however, p r o b a b l y r e f l e c t i n g the f a c t t h a t a g r e a t e r degree of d e c o m p o s i t i o n o f a l g a l biomass has o c c u r r e d i n t h e s e sediments. L i k e humic a c i d s from Mangrove Lake, p a r a f f i n i c s t r u c t u r e s are dominant. I n summary, s o l i d - s t a t e NMR s p e c t r a o f h u m i c a c i d s f r o m m a r i n e and e s t u a r i n e s e d i m e n t s r e v e a l some d i a g e n e t i c s t r u c t u r a l changes. I n r e c e n t l y d e p o s i t e d and w e l l p r e s e r v e d marine sediments s u c h as t h o s e f r o m M a n g r o v e L a k e , Bermuda, c a r b o h y d r a t e s and p a r a f f i n i c s t r u c t u r e s c o n s t i t u t e the major s t r u c t u r a l e n t i t i e s . B u r i a l o r i n c r e a s i n g degree o f d e c o m p o s i t i o n , l e a d s t o the d i m i n u t i o n o f c a r b o h y d r a t e s , w h e r e u p o n p a r a f f i n i c s t r u c t u r e s become dominant. I n m a r i n e sediments d e r i v e d from a l g a l o r m i c r o b i a l s o u r c e s , t h a t a r e more exposed t o d e c o m p o s i t i o n , p a r a f f i n i c s t r u c t u r e s predominate i n humic a c i d s . Such i s the case f o r sediments f r o m W a l v i s Bay and the l o w e r Potomac R i v e r e s t u a r y . I t i s important to note that these l a t t e r sediments c o n t a i n humic a c i d s t h a t h a v e a p r e d o m i n a n t l y a l g a l or m i c r o b i a l s i g n a t u r e even though s u b s t a n t i a l c o n t r i b u t i o n s of t e r r e s t r i a l m a t e r i a l s are e x p e c t e d due t o t h e i r p r o x i m i t y t o s o u r c e s of such c o n t r i b u t i o n s . The h i g h a l g a l p r o d u c t i v i t y and o r g a n i c r i c h s e d i m e n t a c c u m u l a t i o n r a t e s f o r t h e l o w e r P o t o m a c , as w e l l as t h e s t a b l e i s o t o p i c c o m p o s i t i o n s of the s e d i m e n t a r y o r g a n i c m a t t e r (E.C. S p i k e r , p e r s o n a l communication), a r e c o n s i s t e n t w i t h a f i n d i n g t h a t a l g a l d e t r i t u s i s the major c o n t r i b u t o r t o sedimentary carbon. Thus the NMR d a t a f o r humic a c i d s a r e c o n s i s t e n t w i t h t h i s c o n c l u s i o n . As o n e e x a m i n e s h u m i c a c i d s f r o m s e d i m e n t s w h e r e l a r g e t e r r e s t r i a l o r v a s c u l a r p l a n t i n p u t s a r e e x p e c t e d , the CPMAS C NMR s p e c t r a show h i g h e r p r o p o r t i o n s o f a r o m a t i c carbons and n o t a b l e peaks f o r l i g n i n - l i k e c o n t r i b u t i o n s a t 55 and 150 ppm. Such d i s t i n c t i o n s c o u l d p o s s i b l y be u s e d t o e s t i m 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 o f v a s c u l a r p l a n t r e s i d u e s t o the sediments. A J

Humin. Humin, t h e f r a c t i o n o f h u m i c m a t e r i a l t h a t i s i n s o l u b l e i n a l k a l i , h a s o f t e n b e e n r e f e r r e d t o as k e r o g e n , p r o t o k e r o g e n , o r s t a b l e r e s i d u e i n the geochemical 1 i t e r a t u r e ( 1 5 - 1 7 ) . Because i t e x i s t s as a r e s i d u e and i s a d m i x e d w i t h i n o r g a n i c c o m p o n e n t s o f sediments, which g e n e r a l l y c o n s t i t u t e the s i z e a b l e p o r t i o n of the t o t a l w e i g h t , i t has been n e c e s s a r y t o c o n c e n t r a t e the humin p r i o r t o analysis. The most common means of a c h i e v i n g t h i s i s by r e m o v a l of m i n e r a l m a t t e r . U s u a l l y , the sediment r e s i d u e from a l k a l i e x t r a c t i o n i s t r e a t e d w i t h c o n c e n t r a t e d HC1 m i x e d i n a 1:1 v / v r a t i o w i t h 48% aqueous HF. Carbohydrates and p r o t e i n s are s e l e c t i v e l y h y d r o l y z e d i n the p r o c e s s , but these s u b s t a n c e s cannot s t r i c t l y be c a l l e d humic i n nature. T h e i r r e m o v a l f r o m t h e s e d i m e n t a l l o w s us t o e x a m i n e r e f r a c t o r y o r g a n i c m a t t e r or s t a b l e r e s i d u e . Of c o u r s e , we must c o n c e r n o u r s e l v e s w i t h t h e e f f e c t o f s u c h t r e a t m e n t on t h e h u m i c


150


material. S e d i m e n t s f r o m M a n g r o v e L a k e , Bermuda p r o v i d e i d e a l samples f o r t e s t i n g the e f f e c t of a c i d treatment because the carbon content of the whole s a p r o p e l i s h i g h enough t o o b t a i n CPMAS C NMR d i r e c t l y w i t h o u t c o n c e n t r a t i o n . F i g u r e 3 shows t h e NMR s p e c t r a o f a l g a l s a p r o p e l near the sediment s u r f a c e (0.2 m) and a t depth (2.9m), h u m i n o b t a i n e d a f t e r a l k a l i e x t r a c t i o n , and h u m i n a f t e r HF/HC1 treatment. Note t h a t v e r y l i t t l e d i f f e r e n c e e x i s t s between s p e c t r a o f t h e w h o l e s a p r o p e l and t h e h u m i n a f t e r alkali-extraction. C a r b o h y d r a t e s (peaks a t 72 and 106 ppm) a r e major c o n t r i b u t o r s t o the s a p r o p e l i n the s u r f a c e i n t e r v a l s and d i m i n i s h i n c o n c e n t r a t i o n w i t h depth. H a t c h e r and o t h e r s (7) have d e s c r i b e d the d i a g e n e t i c t r e n d s as b e i n g a t t r i b u t a b l e t o d e g r a d a t i o n and l o s s of c a r b o h y d r a t e s w i t h s e l e c t i v e p r e s e r v a t i o n of the i n s o l u b l e , m a c r o m o l e c u l a r p a r a f f i n i c s u b s t a n c e s , w h i c h are the dominant components of humin. When t r e a t e d w i t h HF/HC1, t h e h u m i n i s a l t e r e d , p r i m a r i l y by l o s s o f c a r b o h y d r a t e s . Peak i n t e n s i t i e s f o r n o n - c a r b o h y d r a t e m o i e t i e s ( p a r a f f i n i c s t r u c t u r e s ) remain r e l a t i v e l y unchanged, t o the extent t h a t can be d e t e c t e d by NMR. T h u s , h u m i n t r e a t e d w i t h HF/HC1 i s p r i m a r i l y a l t e r e d by r e m o v a l o f c a r b o h y d r a t e s . T h i s i s e s s e n t i a l l y t h e same p r o c e s s t h a t i s the r e s u l t of e a r l y d i a g e n e t i c t r a n s f o r m a t i o n s d e s c r i b e d a b o v e ( 7 ) . B e c a u s e c a r b o h y d r a t e s c a n n o t be c o n s i d e r e d '•humic" i n n a t u r e (18). the HF/HC1 r e m o v a l of c a r b o h y d r a t e s i s u s e f u l i n a l l o w i n g i n t e r c o m p a r i s o n s among t h e v a r i o u s h u m i c f r a c t i o n s o f sediments. S o l i d - s t a t e C NMR s p e c t r a o f h u m i n , i s o l a t e d by t h e HF/HC1 t r e a t m e n t , from v a r i o u s r e p r e s e n t a t i v e m a r i n e and e s t u a r i n e sediments a r e shown i n F i g u r e 4. Humin f r o m M a n g r o v e L a k e was d e s c r i b e d as b e i n g e s s e n t i a l l y composed o f p a r a f f i n i c s t r u c t u r e s (30 ppm) c o n t a i n i n g c a r b o x y 1 / a m i d e (175 ppm) and e t h e r i c c a r b o n (70 ppm) f u n c t i o n a l groups (7). The low a r o m a t i c i t y ( 7%) i s t y p i c a l of humin f r o m a l g a l and m i c r o b i a l s o u r c e s . The p e a k a t 70 ppm c a n be a t t r i b u t e d t o e t h e r or a l c o h o l - l i k e s t r u c t u r e s because the compounds t h a t a r e u s u a l l y c h a r a c t e r i s t i c of t h i s resonance, the c a r b o h y d r a t e s , h a v e most l i k e l y b e e n r e m o v e d by t h e a c i d t r e a t m e n t . S p e c t r a of humin from o t h e r samples examined here a l s o show an i n t e n s e peak a t 30 ppm f o r p a r a f f i n i c s t r u c t u r e s , b u t t h e r e l a t i v e p r o p o r t i o n o f a r o m a t i c c a r b o n (130 ppm) i n c r e a s e s s i g n i f i c a n t l y i n some s a m p l e s . Those h a v i n g s t r o n g c o n t r i b u t i o n s from a l g a 1 / m i c r o b i a l s o u r c e s , n a m e l y s e d i m e n t s f r o m W a l v i s Bay and t h e H u d s o n C a n y o n , show a g r e a t e r p r o p o r t i o n of p a r a f f i n i c s t r u c t u r e s . The i n c r e a s e d amounts o f a r o m a t i c c a r b o n s when compared t o h u m i n f r o m M a n g r o v e L a k e p r o b a b l y r e f l e c t s i n c r e a s e d c o n t r i b u t i o n s from v a s c u l a r p l a n t s . Humin i s o l a t e s from sediments of the New Y o r k B i g h t and Potomac R i v e r e s t u a r y have s p e c t r a t h a t are n o t a b l y d i f f e r e n t i n that a r o m a t i c carbons are the dominant components. The s p e c t r a r e s e m b l e t h a t o f humin i s o l a t e d i n the same manner from an a e r o b i c s o i l from s o u t h e r n G e o r g i a ( F i g u r e 5). However, u n l i k e the humin from s o i l w h i c h shows a s i g n i f i c a n t peak f o r c a r b o x y l carbon (175 ppm), s p e c t r a of humin from the New Y o r k B i g h t and the Potomac R i v e r do not d i s p l a y a d i s c r e e t p e a k a t 175 ppm a n d a p p e a r t o be d e p l e t e d of c a r b o x y 1 / a m i d e g r o u p s . E l e m e n t a l d a t a f o r t h e s e h u m i n s (19) a r e c o n s i s t e n t w i t h t h e NMR r e s u l t s . A t o m i c H/C r a t i o s o f l e s s t h a n 0.8 a r e n o t t y p i c a l o f h u m i c m a t e r i a l b u t more l i k e t h o s e o f h i g h l y aromatic c o a l or c o a l - l i k e p r o d u c t s . The NMR s p e c t r a a l s o r e s e m b l e


1 3

1 3


In Organic Marine Geochemistry; Sohn, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986. 1 3

2.9m depth

F i g u r e 3. CPMAS C NMR s p e c t r a o f s a p r o p e l , h u m i n , a n d démineraiized humin from two i n t e r v a l s i n a c o r e from Mangrove Lake, Bermuda.

0.2m depth


152



i J

F i g u r e 4. R e p r e s e n t a t i v e CPMAS C NMR s p e c t r a o f démineraiized humin from marine and e s t u a r i n e sediments.



9. HATCHER AND OREM


humin-HF/HCI


153


154


those o f c o a l , w i t h l i t t l e o r no c a r b o x y l peaks and broad, u n r e s o l v e d p e a k s f o r m o s t l y a r o m a t i c c a r b o n s ( 2 0 ) . The p r e s e n c e o f c o a l a n d c o a l - l i k e m a t e r i a l s i n e s t u a r i n e sediments i s not unexpected. The p r e s e n c e o f c o a l has b e e n n o t e d i n s e d i m e n t s o f t h e C h e s a p e a k e Bay ( 2 1 ) . S t o r m r u n o f f a n d sewage f r o m New Y o r k C i t y , w h i c h a r e b o t h c o l l e c t e d and dumped i n t h e New Y o r k B i g h t , a r e a l s o l i k e l y t o c o n t a i n c o a l - d e r i v e d s u b s t a n c e s . C e r t a i n l y , dredge s p o i l s from t h e H u d s o n - R a r i t a n e s t u a r y , w h i c h a r e a l s o dumped i n the New Y o r k B i g h t , are l i k e l y t o c o n t a i n c o a l - l i k e substances as w e l l . The p o s s i b i l i t y e x i s t s t h a t c a r b o x y l f u n c t i o n a l groups and t h e c h e m i c a l c o m p o s i t i o n o f t h e h u m i n f r o m t h e two s a m p l e s i n q u e s t i o n h a v e b e e n a f f e c t e d by t h e HF/HC1 t r e a t m e n t . D e c a r b o x y l a t i o n and h y d r o l y s i s o f p r o t e i n a c e o u s substances by s t r o n g a c i d treatment i s p o s s i b l e and c y c l i z a t i o n o f c a r b o h y d r a t e s , i f present, t o form aromatic groups c o u l d a l s o take p l a c e . T h i s seems u n l i k e l y , c o n s i d e r i n g t h a t a s i m i l a r treatment o f Mangrove Lake s a p r o p e l , t h a t i s r i c h i n c a r b o h y d r a t e s and c a r b o x y l f u n c t i o n a l groups, d i d not produce such components. We b e l i e v e t h a t t h e h i g h l y aromatic s t r u c t u r e s are i n d i g e n o u s and p o s s i b l y i n d i c a t i v e o f c o n t r i b u t i o n s o f c o a l - l i k e m a t e r i a l . Based on the r e l a t i v e l y low y i e l d o f humin i n t h e s e two sediments, t h e c o n t r i b u t i o n o f c o a l - l i k e m a t e r i a l may be r e l a t i v e l y minor.

Discussion 1 3

The s o l i d - s t a t e C NMR s p e c t r a o f humin from a l g a l o r m i c r o b i a l l y d e r i v e d sediments are s i m i l a r t o those o f c o r r e s p o n d i n g humic a c i d s . A s i d e from the p r e s e n c e o f c a r b o h y d r a t e s i n humic a c i d s from the Mangrove Lake s a p r o p e l , the s p e c t r a of humins a r e a l m o s t i d e n t i c a l t o those o f humic a c i d s , s u g g e s t i n g a c l o s e s t r u c t u r a l r e l a t i o n s h i p and p o s s i b l y a c l o s e g e n e t i c r e l a t i o n s h i p . Humic a c i d s g e n e r a l l y c o n t a i n more oxygen i n t h e i r e l e m e n t a l a n a l y s i s (6) and we w o u l d suspect t h a t t h i s w o u l d be r e f e l e c t e d i n t h e p r e s e n c e o f more c a r b o x y l , e t h e r / a l c o h o l , and c a r b o n y l groups. I n comparing s p e c t r a o f humic a c i d s and humin from W a l v i s Bay sediments, the i n c r e a s e d c o n t e n t s o f such f u n c t i o n a l groups i n humic a c i d s a r e s u b t l e b u t n o t i c e a b l e as m o s t l y i n c r e a s e d r e l a t i v e i n t e n s i t i e s a t 175 and 190 ppm. Because o f the c l o s e s t r u c t u r a l s i m i l a r i t i e s , we b e l i e v e t h a t humic a c i d s a r e s t r u c t u r a l e q u i v a l e n t s o f humin t h a t have been o x i d i z e d , r e s u l t i n g i n the i n t r o d u c t i o n o f o x y g e n - f u n c t i o n a l groups ( i . e . c a r b o x y l groups). The i n c r e a s e d oxygen f u n c t i o n a l i t y a l l o w s t h e s e s t r u c t u r e s t o be more r e a d i l y e x t r a c t e d b y d i l u t e b a s e . When a c i d i f i e d , t h e c a r b o x y l groups are p r o t o n a t e d , thereby r e d u c i n g s o l u b i l i t y such t h a t t h e o x i d i z e d r e m a i n s p r e c i p i t a t e as humic a c i d s . I n e s t u a r i n e and c o a s t a l sediments s t r o n g s t r u c t u r a l r e l a t i o n s h i p s between humic a c i d s and h u m i n a r e n o t o b s e r v e d ( s e e F i g u r e s 2 a n d 4 ) . T h i s i s most l i k e l y a t t r i b u t a b l e t o the f a c t t h a t h i g h l y r e f r a c t o r y , c o a l - l i k e c o m p o n e n t s d o m i n a t e t h e h u m i n r e s i d u e . These r e f r a c t o r y m a t e r i a l s p r o b a b l y do n o t p r o d u c e h u m i c a c i d s a s r e a d i l y a s m o d e r n p l a n t remainβ u p o n o x i d a t i o n . H o w e v e r , modern p l a n t - d e r i v e d m a t e r i a l s w i t h i n t h e s e d i m e n t , whose d e t e c t i o n b y NMR may be masked by t h e broad peaks o f c o a l - l i k e s u b s t a n c e s , are p r o b a b l y r e s p o n s i b l e f o r the


9. HATCHER A N D O R E M


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p r o d u c t i o n o f humic a c i d s . Thus, t h e humic a c i d s i n these sediments h a v e s t r u c t u r a l f e a t u r e s t h a t a r e l i k e t h o s e e x p e c t e d f r o m modern s o u r c e m a t e r i a l s but t h e humin i s p r o b a b l y n o t r e p r e s e n t a t i v e o f source m a t e r i a l s d e r i v e d from modern carbon.

CONCLUSIONS


A J

S o l i d - s t a t e C NMR p r o v i d e s a v i s u a l p r e s e n t a t i o n o f t h e c h e m i c a l s t r u c t u r a l c o m p o s i t i o n o f humic i s o l a t e s t h a t a l l o w s f o r d i r e c t s t r u c t u r a l i n t e r c o m p a r i s o n s among f u l v i c a c i d s , humic a c i d s , and t h e i n s o l u b l e h u m i n i n m a r i n e and e s t u a r i n e s e d i m e n t s . Though t h e s t r u c t u r a l d e t a i l p r o v i d e d by t h i s t e c h n i q u e i s no more than a "broad b r u s h " e x a m i n a t i o n , such an a p p r o a c h i s u s e f u l from t h e s t a n d p o i n t that gross 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 can provide c l u e s t o the o r i g i n o f humic substances. P r e v i o u s s t u d i e s i n v o l v i n g t h e use o f s o l i d - s t a t e C NMR i n c o m b i n a t i o n w i t h o t h e r o r g a n i c g e o c h e m i c a l and s t a b l e i s o t o p i c a n a l y s e s have l e d t o t h e s u g g e s t i o n t h a t i n s o l u b l e m a c r o m o l e c u l a r h u m i n i s an o r i g i n a l component o f a l g a l / m i c r o b i a l biomass i n m a r i n e s e d i m e n t s and t h a t t h i s m a t e r i a l , r i c h i n p a r a f f i n i c structures, i s s e l e c t i v e l y preserved during e a r l y d i a g e n e s i s (7_). E a r l y d i a g e n e s i s b a s i c a l l y i n v o l v e s d e g r a d a t i o n and l o s s o f m i c r o b i a l l y l a b i l e s u b s t a n c e s s u c h as c a r b o h y d r a t e s , p r o t e i n s , and l i p i d s . W i t h t h i s f r a m e o f r e f e r e n c e we e x a m i n e d s t r u c t u r a l f e a t u r e s o f marine and e s t u a r i n e humic substances by CPMAS C NMR and c o n c l u d e t h e f o l l o w i n g : 1. F u l v i c a c i d s , t h e m o s t s o l u b l e h u m i c f r a c t i o n , a r e p r e d o m i n a n t l y p o l y s a c c h a r i d e s i n a l l m a r i n e and e s t u a r i n e sedimentβ examined. U r o n i c a c i d - l i k e p o l y s a c c h a r i d e s a r e the most l i k e l y entities. F u l v i c a c i d s may be t h e d e g r a d a t i o n p r o d u c t s t h a t e v o l v e d u r i n g d i a g e n e t i c a l t e r a t i o n o f sedimentary p l a n t residues. We e n v i s i o n t h a t m i c r o b i a l d e g r a d a t i o n r e n d e r s p l a n t p o l y s a c c h a r i d e s s o l u b l e , e n t r a i n i n g them i n t o a f u l v i c a c i d f r a c t i o n by d e f i n i t i o n . U l t i m a t e l y , t h i s m a t e r i a l i s degraded f u r t h e r t o C 0 , CH^, and o t h e r l o w m o l e c u l a r w e i g h t o r g a n i c compounds. 2. Humic a c i d s o f m a r i n e and e s t u a r i n e s e d i m e n t s a r e c h a r a c t e r i z e d by m a j o r amounts o f p a r a f f i n i c s t r u c t u r e s t h a t p r e v i o u s s t u d i e s h a v e shown t o be h i g h l y branched and t o c o n t a i n s i g n i f i c a n t q u a n t i t i e s o f c a r b o x y 1 / a m i d e and a l c o h o l / e t h e r c a r b o n . Some h u m i c a c i d s , n a m e l y t h o s e f r o m w e l l preserved s a p r o p e l i c m a r i n e s e d i m e n t s show s i g n i f i c a n t q u a n t i t i e s o f c a r b o h y d r a t e - l i k e s t r u c t u r e s i n c o r p o r a t e d . T h i s , no doubt, i s a r e f l e c t i o n of the s o l u b i l i t y c h a r a c t e r i s t i c s of polysaccharides w h i c h may h a v e some c a r b o x y l f u n c t i o n a l i t i e s ( u r o n i c a c i d groups). 3. Humin v a r i e s w i d e l y i n c o m p o s i t i o n . Sediments d e r i v e d from a l g a l / m i c r o b i a l biomass h a v e h u m i n w i t h p a r a f f i n i c s t r u c t u r e s r e s e m b l i n g those o f c o r r e s p o n d i n g humic a c i d s . E s t u a r i n e o r c o a s t a l marine sediments examined i n t h i s study have humin w i t h h i g h l y aromatic s t r u c t u r e s which resemble c o a l - l i k e materials r a t h e r than modern p l a n t r e s i d u e s . I n t h e s e l a t t e r sediments no s t r u c t u r a l c o r r e s p o n d e n c e e x i s t s between humin and humic a c i d s w h i c h a p p e a r t o more n e a r l y r e f l e c t t h e n a t u r e o f m o d e r n p l a n t l 3

l 3

2


156



residues being incorporated i n sedimentary organic matter. C o n s e q u e n t l y , a c e r t a i n amount o f c a u t i o n must be e x e r c i z e d when u s i n g a r o m a t i c i t y and p o s s i b l y o t h e r s t r u c t u r a l c h a r a c t e r i s t i c s as source d i s c r i m i n a n t s . 4. F i n a l l y , 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 h u m i c f r a c t i o n s i n m a r i n e and e s t u a r i n e sediments suggest t h a t t h e p a t h w a y f o r h u m i f i c a t i o n i s one o f d e g r a d a t i o n r a t h e r t h a n c o n d e n s a t i o n as proposed by o t h e r s (15. 22). I n s o l u b l e humin, an o r i g i n a l component o f s e d i m e n t a r y d e t r i t u s , i s d e g r a d e d t o s m a l l e r m o l e c u l e s w h i c h become e x t r a c t a b l e and t h e r e b y c l a s s e d as humic a c i d s . F u l v i c a c i d s a r e u l t i m a t e l y f o r m e d by i n t e n s e d e g r a d a t i o n ; but d e g r a d a t i o n p r o d u c t s o f l a b i l e m a c r o m o l e c u l e s o f s e d i m e n t a r y d e t r i t u s s u c h as c a r b o h y d r a t e s a l s o become i n c o r p o r a t e d and, i n f a c t , d o m i n a t e t h e f u l v i c a c i d f r a c t i o n .

LITERATURE CITED 1. 2. 3. 4. 5. 6.

7. 8.

9. 10. 11. 12. 13. 14. 15. 16. 17.

V i l a , F.J.G.; Lentz, H.; Ludemann, H.D. Biochem. Biophys. Res. Commun. 1976, 72, 1063-9. Stuermer, D.H.; Payne, J.R. Geochim. Cosmochim. Acta, 1976, 40, 1109-14. Wilson, M.A.; Goh, K.H. J . Soil Sci., 1977, 28, 645-52. Hatcher, P.G.; Rowan, R.; Mattingly, M.A. Org. Geochem., 1980, 2, 77-85. Hatcher, P.G.; VanderHart, D.L.; Earl, W.L. Org. Geochem., 1980, 2, 87-92. Hatcher, P.G.; Breger, I.A.; Dennis, L.W.; Maciel, G.E. In "Aquatic and Terrestrial Humic Materials", Christman, R.F.; Gjessing, E.T.; Eds.; Ann Arbor Science: Michigan, 1983; Chap. 3. Hatcher, P.G.; Spiker, E.S.; Szeverenyi, N.M.; Maciel, G.E. Nature 1983, 305, 498-501. Hatcher, P.G.; Breger, I.A.; Maciel, G.E.; Szeverenyi, N.M. In "Humic Substances in S o i l , Sediment, and Water"; Aiken, G.; McKnight, D.; Wershaw, R.; MacCarthy, P. Eds., John Wiley: New York, 1985; Chap. 11. Wilson, M.A.; Pugmire, R.J.; Zilm, K.M.; Goh, K.M.; Heng, S.; Grant, D.M. Nature 1981, 294, 648-50. Wilson, M.A.; Pugmire, R.J.; Grant, D.M. Org. Geochem. 1983, 5, 121-9. Preston, C.M.; Ripmeester, J.A. Can. J . Spectrosc. 1982, 27, 99-105. Hatcher, P.G.; Breger, I.A.; Mattingly, M.A. Nature 1980, 285, 560-2. Dereppe, J.M.; Moreaux, C.; Debyser, Y. Org. Geochem. 1980, 2, 117-124. Spiker, E.C.; Hatcher, P.G. Org. Geochem. 1984, 5, 283-90. Huc, A.Y.; Durand, Β. Fuel 1977, 56, 73-80. Stuermer, D.H.; Kaplan, I.R.; Peters, K.E. Geochim. Cosmochim. Acta 1978, 42, 989-97. Pelet, R. In Advances in Organic Geochemistry, 1981, Bjoroy, M., Ed., John Wiley: New York, 1983; pp.241-250.


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18. Stevenson, F.J. Humus Chemistry, Genesis, Composition, Reactions, John Wiley: New York, 1982, Chap. 2. 19. Hatcher, P.G. Ph.D. Dissertation, The University of Maryland, 1980. 20. Miknis, F.P; Sullivan, M.; Bartuska, V.J.; Maciel, G.E. Org. Geochem. 1981, 3, 19-28. 21. Goldberg, E.D.; Hodge, V.; Koide, M.; Griffin, J.; Gamble, E.; Bricker,O.P.; Matisoff, G.; Holdren, G.R. Jr.; Braun, R. Geochim. Cosmochim. Acta 1978, 42, 1413-25. 22. Nissenbaum, Α.; Kaplan, I.R. Limnol. Oceanogr. 1972, 17, 570-2. Downloaded by UNIV OF PITTSBURGH on June 21, 2013 | http://pubs.acs.org Publication Date: April 21, 1986 | doi: 10.1021/bk-1986-0305.ch009

RECEIVED September 23, 1985


Organic Marine Geochemistry - American Chemical Society

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