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(241) Contaminant Loads to the Tidal Anacostia River.
Schultz, Cherie*,1, Buckley, Andrea1, Miller, Jason1, Velinsky, David2, Murphy, Timothy3, Foster, Greg4, Hahn, Simeon5, Buchman, Michael6, 1 Interstate Commission on the Potomac River Basin, Rockville, MD, US2 Academy of Natural Sciences, Philadelphia, PA, US3 Metropolitan Washington Council of Governments, Washington, DC, US4 George Mason University, Fairfax, VA, US5 NOAA, Philadelpha, PA, US6 NOAA, Seattle, WA, US
ABSTRACT- The Anacostia River, draining a predominantly urban watershed in Maryland and the District of Columbia, has been identified as a Region of Concern by the USEPA`s Chesapeake Bay Program. The Anacostia Watershed Toxics Alliance has sponsored data collection and the development of a predictive model to evaluate remediation scenarios for contaminants including metals, PCBs, PAHs and chlordane. Surficial bed sediments have been characterized by chemical analyses of 128 samples. Storm water monitoring data is available to estimate metals and organics loads from the upstream tributaries, which drain 72% of the basin. Metals loads from the city`s separate storm (SS) sewer and combined sewer (CS) systems have been estimated from historical data, and organic contaminant load data are currently being collected. A model has been constructed to simulate sediment transport dynamics and contaminant loading, fate and transport. Total loads for zinc, lead, and copper are estimated to be 16100, 8300, and 4600 kg/yr, respectively, with upstream areas found to be the dominant source. The SS system makes the largest contribution to metals loads on a mass per unit area basis. Less than 10% of the metals load is derived from the CS system. Model predictions for metals match available water column data, and long-term simulations for metals agree well with observed spatial patterns of surficial bed sediment concentrations, lending confidence to load estimates. However, preliminary model results for PCBs indicate that 90% of load is currently unaccounted for. This suggests that the watershed is fairly inhomogeneous in terms of PCB source areas, and data will be required from a more representative number of subwatersheds in order to characterize PCB loads.
Key words: sediments, metals, PCBs, fate and transport model
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