WP20 Contaminated Harbor and River Sediment
Wednesday, 16 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(MCL-1117-823244) What activated carbon amendment teaches us about PCB bioavailability.

McLeod, P¹, Luoma, S², Luthy, R, ¹ Stanford University, Stanford, CA, USA² United States Geological Survey, Menlo Park, CA, USA

ABSTRACT- Predicting PCB bioavailability from contaminated sediments remains a top challenge for scientists and engineers. Such predictive capability would be very useful in assessing biological risk at a given site and modeling the potential outcomes of sediment remediation, including activated carbon amendment. In this work, we combine knowledge of sediment geochemistry and species-specific biology to help us achieve a better understanding of PCB bioavailability for two clam species (brackish-water, deposit-feeding Macoma balthica and freshwater, filter-feeding Corbicula fluminea) from three different sediments (Hunters Point, CA; Grasse River, NY; and Lake Hartwell, SC). Our 28-day laboratory bioaccumulation tests performed with Macoma and Corbicula show that activated carbon amendment can reduce PCB uptake in these sediment-dwelling organisms by up to one order of magnitude or more. However, the observed PCB bioaccumulation differs significantly between clam species and among sediment from different sites. Our results suggest that sediment-PCB binding characteristics, the transfer of PCBs from sediment to activated carbon, PCB homolog distributions, and organism feeding traits all influence PCB bioavailability for sediment treated with activated carbon. A biodynamic model which integrates these factors is assessed for its ability to quantitatively predict the clam tissue PCB concentrations observed in our experiments. The model expresses PCB uptake by organisms as a function of uptake from sediment, uptake from water, and contaminant elimination. Our results suggest that a biodynamic model is a useful tool for understanding the dynamics of PCB transfer from sediment to benthic organisms.

Key words: polychlorinated biphenyls, bioavailability, biodynamic modeling, activated carbon