Effect-Based Water Quality Assessment in an Urban Tributary under Base Flow and Storm Conditions

Abstract

Storm events can mobilize organic contaminants from hard surfaces in urban areas and can impact receiving water quality. Traditional water quality assessments predominantly rely on chemical analysis, which inadequately capture the collective effects of diverse chemical mixtures released during storm events. We applied effect-based methods (EBM) to detect arylhydrocarbon receptor (AhR) activity, estrogenic activity, neurotoxicity and oxidative stress response in water samples from an urban tributary during a storm event and compared it with base flow conditions. AhR activity and neurotoxicity peaked during the storm event, with neurotoxicity exceeding the interim effect-based trigger value and showing a high specificity of effect. This suggests unacceptable water quality during the storm event. Conversely, estrogenic activity was relatively low, and there was little difference between base flow conditions and the storm event. The absence of wastewater, industrial and agricultural inputs in the catchment suggests that the observed bioactivity was related to road runoff, specifically from two adjacent major motorways. The effects on AhR and neurotoxicity were linearly correlated with detected concentrations of 15 tire additive chemicals from an accompanying study. This study demonstrates that EBM provides complementary information to chemical analysis for water quality monitoring and that there is an increased chemical pressure on receiving water bodies during rain events in urban areas.