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HA2 Urban Stormwater Impacts on Estuaries
() Spatial and temporal changes in trace contaminants in the tidal Anacostia River after precipitation events.
Velinsky, D.1, Riedel, G.2, Ashley, J.3, Foster, G.4, Schultz, C.5, 1 Academy of Natural Sciences-Patrick Center, Philadelphia, PA, USA2 Smithsonian Environmental Research Center, Edgewater, MD, USA3 Philadelphia University, Philadelphia, PA, USA4 George Mason University, Fairfax, VA, USA5 Interstate Commission on the Potomac River Basin, Rockville, MD, USA
ABSTRACT- There are numerous storm and combined sewer outfalls along the non-tidal or tidal portion of the Anacostia River (Washington, D.C.) that can impact the water quality of the river. In 1999 and 2002, water samples were collected during baseflow and directly after multiple precipitation events (0.2 to 4.8 cm over 24hrs) to assess the impact of rain events and subsequent runoff on the water quality of tidal Anacostia River and to identify sources. In addition a time series was obtained in 2002 at multiple stations in the tidal river to follow the changes in concentrations before, during and after a large rain event (4.8 cm). Water samples were analyzed for dissolved and particulate forms of As, Cd, Cu, Hg, Pb, and Zn as well as PCBs, PAHs, and OC pesticides. Significant increases in dissolved concentrations of specific metals (Hg up to 6 ng/L and Cu up to 5 g/L) were observed after rainfalls of greater than 0.4 cm, though there was a slight or no increase in dissolved As (< 1 g/L) and Pb concentrations (0.5 to 3 g/L). Concentrations of dissolved PCBs (0.1 to 4 ng/L) and PAHs (20 to 520 ng/L) increased after most rain events, however the location of the maximum concentration, indicative of sources, was different for these two organic contaminant classes with PAHs appearing to be strongly influenced from watershed sources outside of the urban core while PCBs increased more substantially from runoff within the urban core. In the tidal river, dissolved PCBs, Hg, and Pb concentrations took >4 days to decrease to background levels. Concentrations of contaminants in the suspended particles also showed concentrations changes during each rain event but overall concentrations were lower than those found in surface sediments (dilution). The spatial and temporal changes in these parameters occurred both from the upstream, non-tidal reaches largely dominated by residential urban and suburban land, as well as the lower tidal reaches largely dominated by stormwater runoff and CSOs from the metropolitan area.
Key words: Anacostia River, urban runoff, dissolved trace elements, PCBs and PAHs
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