Surface Water Concentrations and Loading Budgets of Pharmaceuticals and Other Domestic-Use Chemicals in an Urban Watershed (Washington, DC, USA)

Pharmaceuticals and domestic-use chemicals (PDCs) are classes of emerging chemical contaminants thought to enter the aquatic environment primarily through wastewater treatment plant (WTP) discharges. The intent of this study was to quantify loadings of PDCs in an urban watershed. The watershed has two major branches but with wastewater discharge occurring in only one of the two major branches. Surface water from the Anacostia River (Washington, DC) was collected in base-flow and storm-flow regimes. Surface water was filtered to separate water and particles, and the PDCs were extracted from water with Oasis HLB solid-phase extraction cartridges and extracted from sediments using microwave-assisted extraction. The PDCs in the extracts were quantified using gas chromatography-mass spectrometry in the form of the trimethylsilyl ether derivatives. The most frequently detected PDC with the highest concentration was bisphenol-A in both branches of the Anacostia River watershed and the least frequently detected PDC was diclofenac. The overall median concentrations for all measured PDCs in surface water ranged from nondetectable to 54.9 ng/l. Alternatively, in the collected WTPs samples, naproxen was observed, with the highest concentration and the median concentrations in WTP effluent ranging from nondetectable to 276 ng/l. Estimates of PDC loadings for February 2006 from WTP effluent showed that < 2% of the downstream load in the NE Branch was derived from WTP discharge. PDC sources other than WTP effluent appear to influence surface water concentrations in the urban Anacostia River watershed.