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PT15 Contaminated Harbour and River Sediment
(PT243) Predicting PAH partitioning in highly impacted sediments.
Walker, S1, Dickhut, R2, Chisholm-Brause, C3, 1 U.S. Naval Research Laboratory, Washington, DC, USA2 Virginia Institute of Marine Science, College of William and Mary, Gloucester Point, VA, USA3 Applied Research Center, College of William and Mary, Newport News, VA, USA
ABSTRACT- The partitioning of polycyclic aromatic hydrocarbons (PAHs) between porewaters and surficial sediments was examined in the Elizabeth River, VA, a highly industrialized urban estuary, with elevated concentrations and multiple sources of PAHs. Based on the results of linear regression analyses, surface sediment samples from the Elizabeth River and the James River, VA, were categorized into two groups: those exhibiting two-phase equilibrium partitioning, dominated by organic carbon (8%), soot carbon (47%) or multiple phases, such as creosote, coal, soot, and other organic matter (29%); and those indicating three-phase equilibrium, with the potential influence of dissolved organic carbon (16%). Of those exhibiting two-phase equilibrium partitioning, the majority of the samples demonstrated a higher affinity for organic matter than for n-octanol. PAH partitioning to soot carbon was dominant in samples located adjacent to a coal-fired power plant in which the relative abundance of soot carbon ranged 22-64% of the total organic carbon in the sediments. PAH partitioning to creosote was indicated in samples located adjacent to two former wood-treatment facilities, as evidenced by observed PAH partition coefficients that exceeded values predicted by combined organic carbon and soot carbon partitioning models. PAH partition coefficients were predicted, on average, to within a factor of four using combined organic/soot carbon partitioning models. However, partitioning to creosote and coal, the two primary sources of PAHs to Elizabeth River sediments, must also be considered to accurately estimate PAH partition coefficients. Overall, few sediment samples exhibited a potential influence of PAH partitioning to dissolved organic carbon (DOC). While DOC alone failed to accurately predict observed partition coefficients, incorporation of soot carbon into the DOC model improved model fits for the majority of the samples by up to a factor of 10 or more.
Key words: partitioning, PAHs, urban
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