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(612) Assessing Contaminant Distribution in the Anacostia River using Semi-Permeable Mebrane Devices and Filter-feeding Clams.
Doelling Brown, Paige*,1, Pinkney, Alfred, Phelps, Harriette2, 1 U.S. Fish & Wildlife Service, Annapolis, MD, USA2 University of the District of Columbia, Washington, D.C., USA
ABSTRACT- The Anacostia River, a tidal freshwater river passing through Washington, D.C., USA, is one of three toxics regions of concern identified by the Chesapeake Bay Program, largely as a result of the input of PCBs and PAHs which accumulate in sediments and biota. To evaluate potential contaminant sources, semi-permeable membrane devices (SPMDs) and caged Asiatic clams (Corbicula fluminea ) were simultaneously deployed in the fall of 2000. SPMDs were placed at 9 sites in the Anacostia River (6 in the lower tidal portion, 3 in the major tributaries) and at a reference site in the Potomac River estuary. Clams were collected from the reference site, and redeployed to 3 sites near the confluence of the major tributaries. All of lower Anacostia River sites (1.5-1.8 ppm), and some tributary sites (0.8-1.3 ppm) had significantly higher concentrations of tPCBs in SPMDs than the reference site (0.8 ppm). PCBs in the clams from tributaries ranged from 0.36-0.48 ppm, significantly higher than the reference site (0.34 ppm). tPAHs in SPMDs were higher at the lower tidal river sites (12.5-17.5 ppm) and tributaries (12.0-20.7 ppm) than at the reference site (6.7 ppm). Mean tPAHs in clams at the Anacostia tributary sites (≥1 ppm) were significantly higher than at the reference site (0.4 ppm). PCB concentrations in both SPMDs and clams from the Anacostia River were elevated compared to the reference site in the Potomac River, but concentrations appeared to be relatively consistent throughout the tidal river and tributaries. PAH concentrations were also higher in the Anacostia, but more variable by location. Although storm sewer and combined sewer outfalls appeared to be a significant source of contaminants to the lower river, there was also substantial input from the tributaries. Based on these results, substantial source control is recommended as part of the overall Anacostia River restoration plan.
Key words: Anacostia River, PCBs, PAHs, estuary
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