7 Chemistry of Dissolved Organic Matter in Rivers, Lakes, and Reservoirs Downloaded by UNIV OF QUEENSLAND on April 26, 2016 | http://pubs.acs.org Publication Date: May 5, 1994 | doi: 10.1021/ba-1994-0237.ch007
J . A . Leenheer U.S. Geological Survey, Water Resources Division, Denver, C O 80225
Recent investigations provide new insight on the structural chemistry of dissolved organic matter (DOM) in freshwater environments and the role of these structures in contaminant binding. Molecular models of DOM derived from allochthonous and autochthonous sources show that short-chain, branched, and alicyclic structures are terminated by carboxyl or methyl groups in DOM from both sources. Allochthonous DOM, however, had aromatic structures indicative of tannin and lignin residues, whereas the autochthonous DOM was characterized by aliphatic alicyclic structures indicative of lipid hydrocarbons as the source. DOM isolated from different morphoclimatic regions had minor structural differences.
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H E G E O C H E M I S T R Y O F DISSOLVED ORGANIC MATTER (DOM) i n n a t u r a l
waters was recently r e v i e w e d i n a textbook b y T h u r m a n (I). I n the extensive b o d y of literature he r e v i e w e d , average d i s s o l v e d organic c a r b o n ( D O C ) concentrations v a r i e d as follows: 0.7 m g / L for g r o u n d w a t e r , 1.0 m g / L for p r e c i p i t a t i o n , 2.0 m g / L for o l i g o t r o p h i c lakes, 5.0 m g / L for rivers, 10.0 mg/ L for e u t r o p h i c lakes, 15 m g / L for marshes, a n d 30 m g / L for bogs. T h e various sources a n d relative abundance of D O C i n natural waters are d e p i c t e d i n F i g u r e 1. O n l y about 2 0 % of the D O M i n natural waters consists o f identifiable c o m p o u n d s that i n c l u d e carbohydrates, carboxylic acids, a m i n o acids, a n d hydrocarbons (I). T h e r e m a i n i n g 8 0 % o f D O M (generally d e f i n e d as h u m i c substances) consists o f c o m p l e x , e n v i r o n m e n t a l l y altered residue o f plant, bacterial, a n d fungal o r i g i n , of moderate m o l e c u l a r w e i g h t (500-5000 d a l tons). T h i s p r e d o m i n a n t l y acidic u n d e f i n e d D O M has b e e n classified b y
This chapter not subject to U . S . copyright Published 1994 American Chemical Society
Baker; Environmental Chemistry of Lakes and Reservoirs Advances in Chemistry; American Chemical Society: Washington, DC, 1994.
Baker; Environmental Chemistry of Lakes and Reservoirs Advances in Chemistry; American Chemical Society: Washington, DC, 1994.
Figure 1. Allochthonous and autochthonous sources of dissolved organic carbon in natural waters. (Reproduced with permission from reference 1. Copyright 1985 Kluwer Academic Publishers.)
Downloaded by UNIV OF QUEENSLAND on April 26, 2016 | http://pubs.acs.org Publication Date: May 5, 1994 | doi: 10.1021/ba-1994-0237.ch007
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