Anaerobic sediment species

Sorption of Phosphate and Arsenic Species by Anaerobic Sediments... 

Arsenic speciation in anaerobic sediments is controlled by both microbially mediated transformations of species and by abiotic chemical processes including adsorption. The two... 

Figure 19 1 Processes in the sediment nitrogen cycle. Hashed lines reflect aerobic processes while solid lines reflect anaerobic processes. Species in hashed circles are gaseous.

The oxidation of organic matter in anaerobic sediments can utilize a number of species as oxidants, of which sulfate is the most important. In seawater at pH values close to 8, sulfate-reducing bacteria metabolize organic matter according to the following simplified equation ... 

When the overall oxidation state of a system is desired, unless a water is obviously anaerobic (e.g., it has an H2S odor) one should first attempt to measure dissolved oxygen as an index of system redox state. Eh measurements are unlikely to be stable and thermodynamically meaningful in surface-waters, except in acid waters (where ferrous and ferric species are usually present). Eh measurements may be stable and meaningful in anaerobic sediments or groundwaters, when species of iron, sulfur, and manganese dominate the redox chemistry, but otherwise are of qualitative value only. 

The accumulation of nnacceptable concentrations of mercury in fish occurs largely as a result of bioaccumulation of methyl mercnry np the food chain to the top predator fish, which are the most desired species. Methyl mercnry forms largely in the anaerobic sediments of water bodies and then moves up through several trophic levels. 

Delgado, M. C. and N. L. Wolfe. 1992. Structure-activity relationships for the reduction of / -substituted nitrobenzenes in anaerobic sediments. Presented at the American Chemical Symposium on the Oxidation-Reduction Transformations of Inorganic and Organic Species in the Environment, San Francisco, CA, April... 

Defining I, B Schink (1989b) Two new species of anaerobic oxalate-fermenting bacteria, Oxalobacter vibrioformis sp. nov., and Clostridium oxalicum sp. nov., from sediment samples. Arch Microbiol 153 79-84. 

N limited. Nutrient availability also affects the composition of plant communities species richness and the presence of rare species often decline as nutrient availability increases beyond some threshold (Bedford et al., 1999). In addition to the inflow of nutrients with the water and sediment, there are complicated interactions between hydrology and nutrient availability that affect productivity and decomposition. Transformations of N and P under anaerobic conditions are discussed in Section 4.3. 

Bacterial anaerobes including Desulfovibrio, Desulfomonas, and Desulfotomaculum are known sulfate-reducing species. They can survive in fresh, brackish, and sea water and are present in most soils and sediments containing sulfate and sulfite compounds. Enzymes which promote the conversion of sulfates and sulfites to metal sulfides through chemical reduction are present in these bacteria. Iron sulfide, FeS, is a product of this process. 

Tne question of the source molecule occurrence must be addressed. The coincidence in anaerobic environments of ammonia and reduced divalent sulfur species, which includes hydrogen sulfide, bisulfide anion and sulfide dianion, has been given adequate recognition. (See for example references 36,37.) The coincidence of polysulfide and ammonia has already been noted in an earlier part of this report (1). Polysulfide has been found in tidal and salt marsh sediments as well (38). 

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