University of Delaware (Di Toro)Superfund Basic Research ProgramToxicity and Mobilization of Metals and Metal Mixtures in SedimentsProgram Director: Dominic M. Di Toro SummaryThe goal of this research is to develop models for predicting the toxicity and mobilization of individual metals and metal mixtures in sediments. These predictions are critical in evaluating the risk associated with contaminated sediments at Superfund sites. In past Superfund basic research projects, project investigators have developed methods of assessing the toxicity of individual metals - Cd, Cu, Ni, Pb and Zn - for sediments with excess acid volatile sulfides (AVS). The researchers are developing a model that predicts the toxicity of metals in sediments with little or no AVS. This requires a prediction of the partitioning of sediment metals to the other important sediment phases - sediment organic carbon if it is in sufficient supply, and then the other phases (e.g. iron oxyhydroxides) that are important in the aerobic layer of sediments. Project researchers also propose to develop the next generation of models for the prediction of mobilization of metals from sediments that explicitly include the mechanisms of mobilization. They model the mechanisms of metal sulfide oxidation directly and relate them to the cycles of manganese and iron in sediments. The researchers have included such a mechanism involving the Fe(ll)-facilitated oxidation of arsenic in their present project. They propose to extend this work to the oxidation of metal sulfides. The project objectives are:
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