Seasonal variations of emerging organic contaminants (EOCs) in drinking water sources in the Susquehanna River Basin

Abstract. The presence of emerging organic contaminants (EOCs) in surface water bodies can cause adverse effects on non-target organisms. When these surface water bodies are used as drinking water sources, temporal variability in EOC concentrations can potentially impact drinking water quality and human health. To better understand the spatiotemporal variability of EOCs in drinking water sources in Central Pennsylvania, EOCs were evaluated in six drinking water sources during a two-year study (April 2016 – June 2018) in the Susquehanna River Basin (SRB). The study was conducted in two phases, whereby Phase I was a spatially distributed sampling within the SRB focusing on seven human pharmaceuticals while Phase II was a temporally intensive sampling regime at one site focusing on a broader range of EOCs including human and veterinary pharmaceuticals and a neonicotinoid insecticide. Concentration-discharge (C-Q) relationships were utilized to classify the transport dynamics exhibited by EOCs and understand the extent to which transport pathways such as surface runoff and wastewater effluent discharge may contribute to the presence of EOCs. Overall, EOCs were present at higher concentrations in colder seasons than warmer seasons. Concentrations of thiamethoxam, a neonicotinoid insecticide used in agricultural fields, and caffeine exhibited accretion dynamics in surface water during high flow periods consistent with higher transport during surface runoff events. Human pharmaceuticals known to persist in wastewater effluent were inversely correlated with discharge, indicating dilution characteristics consistent with diminished wastewater signals during surface runoff events. Acetaminophen exhibited episodic transport dynamics consistent with nonpoint source inputs during high flow periods.