Hydrogeochemical Fate of Pharmaceutical Chemicals Discharged into a Tidal Freshwater Estuary

Abstract The tidal freshwater Potomac River (TFPR) in the metropolitan Washington, DC region receives wastewater discharge from eight major wastewater treatment plants with the potential to alter water quality. A total of 90 pharmaceutical chemicals and personal care products (PPCPs) were analyzed in surface water and sediments using solid-phase extraction and QuEChERS, respectively, in conjunction with liquid-chromatography tandem mass spectrometry-multiple reaction monitoring quantitation (LC-MS/MS-MRM). There were 52 PPCPs quantified in both surface water and sediment. The most frequently quantified PPCPs in water included caffeine, fexofenadine, nicotine, sulfamethoxazole, hydrochlorothiazide, MDA, desvenlafaxine, and metoprolol ranging from 10 to 360 ng/L, and in sediment included diphenhydramine, escitalopram, desvenlafaxine, fexofenadine, sertraline and triclocarban ranging from 20 to 120 ng/g (dry weight). Comparisons of PPCP constituents in WTP discharge and adjacent surface water showed altered compositions reflecting dispersal and transformation processes acted quickly following contact of effluent with surface water. Although the PPCPs were present at their highest concentrations in surface water near the WTP discharge zones, the concentrations rapidly attenuated yielding mainstem TFPR PPCP concentrations that did not show elevated concentrations along the freshwater reach of the tidal range in the estuary. The concentrations in sediment also decreased within 1-km from the tributary shoals to the mainstem river. Two prominent seasonal trends were evident in surface water between May to September for many PPCPs correlating with use patterns and temperature.