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ENVIRONMENTAL CHARACTERISTICS AFFECTING REDUCTIVE TRANSFORMATION OF ORGANIC POLLUTANTS IN ANOXIC SEDIMENTS
Citation:
Mack, E. E., J W. Beck, C S. Mazur, AND W J. Jones. ENVIRONMENTAL CHARACTERISTICS AFFECTING REDUCTIVE TRANSFORMATION OF ORGANIC POLLUTANTS IN ANOXIC SEDIMENTS. Presented at 20th Annual Society of Environmental Toxicology and Chemistry Meeting, Philadelphia, PA, November 14-18, 1999.
Description:
Reductive transformations are important processes for determining the fate of organic pollutants in anoxic environments. These processes are most often microbially mediated by both direct and indirect means. For example, specific bacteria transform organic pollutants directly as co-metabolites or as terminal electron acceptors for the conservation of energy. Alternatively, reduced minerals, generated as products of microbial respiration processes, can serve as reductants for a number of organic pollutants either directly or through a mediator such as natural organic matter. The fates of 3 model compounds, nitrobenzene, 2,4 dichlorophenol, and perchloroethylene were followed in sediment microcosms from four sediments of dfferent physicochemical characteristics. These model compounds were chosen for this study because they contain reducible functional groups with dfferent physicochemical properties. The sediments differed in their ambient concentrations of iron, organic matter, salinity and in situ redox potential. All sediments studied were competent for the reductive transformation of nitrobenzene to aniline but, differences in the competency for transformation of 2,4 dichlorophenol and perchloroethylene were observed. Microbially inhibited controls indicated that nitrobenzene reduction is an example of an indirect microbially mediated reductive transformation. The degree that nitrobenzene reduction was coupled to biotic processes in the different sediments correlated with the presence of microbially produced pools of reduced iron minerals (as characterized by CaCl2, ascorbate and HCI extractable fractions). In contrast, direct microbial transformations of 2,4 dichlorophenol and perchloroethylene were affected by specific physicochemical environmental parameters including redox level, pools of oxidizable organic carbon, and the presence of a competent microbial population.