Freshwater environments, dissolved organic

Contaminated bed sediments exist at numerous locations in the United States and around the world. These result mainly from past indiscriminate pollution of our aquatic environments and consist of freshwater and marine bodies including streams, lakes, wetlands, and estuaries. The bed sediments contain many hydrophobic organic compounds and metal ions that in the course of time act as sources of pollutants of the overlying aqueous phase. There are a number of transport pathways by which pollutants are transferred to the aqueous phase from contaminated sediments. One of the lesser known, but potentially important, modes of transport of pollutants from bed sediments is by diffusion and advection of contaminants associated with colloidal-size dissolved macromolecules in pore water. These colloids are measured in the aqueous phase as dissolved organic compounds (DOCs). (These are defined operationally as particles with a diameter smaller than 0.45 micrometer.)... 

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. 

GUhs, P.L., J.C. McGeer, G.L. Mackie, et al. 2010. The effect of natural dissolved organic carhon on the acute toxicity of copper to larval freshwater mussels (glochidia). Environ. Toxicol. Chem. 29 2519-2528. 

Depositional and Diagenetic Behavior of Sulfur. The key controls on sulfur behavior in freshwater-lake, saline-lake, and marine sediments include the concentration of reactants for bacteriogenic H2S formation and sulfide-mineral formation. Table IV illustrates the relative importance of the independent reactants (organic matter, dissolved sulfate, and iron) in each of the lacustrine environments studied. We have shown that in saline... 

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