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Evaluation of Attenuation of Stormwater Toxicity by Iron Enhanced Sand Filters: Bioeffects-Based Approach

Authors: Dalma Martinovic-Weigelt, Chantel Wang, University of St. Thomas; David Fairbairn, MN PCA

Abstract: Present study characterized the toxicity of urban stormwater and determined whether iron enhanced sand filters can attenuate stormwater toxicity. Stormwater samples were collected on four occasions (during major snowmelt and rain events) from three stormwater outfalls, and from the three sand filter inlets and their respective outlets. Effects of stormwaters on 25 human nuclear receptors and 46 transcription factors were evaluated. Stormwater samples had very low non-specific, acute toxicity, which was eliminated by sand filters. High-throughput assays indicated that stormwater typically upregulated approximately a dozen of molecular targets including: the peroxisome proliferator-activated receptors, the estrogen receptor alpha, the pregnane X receptor, the arylhydrocarbon receptor. The magnitude of upregulation in the majority of the stormwater samples (untreated and sand filter treated) was similar to or greater than that of treated municipal wastewater effluent samples from a major metropolitan area. In most cases, passage of stormwater through sand filters reduced toxicity (e.g., arylhydrocarbon receptor, PPAR gamma and alpha), but in several cases the toxicity was unchanged (e.g., pregnane X receptor, estrogen receptor alpha). We are currently integrating in vitro and analytical chemistry data to identify chemical drivers of the observed stormwater toxicity.