2018•Western CEDAR (Western Washington University)Requires access
Assessment of the impact of soil properties and biological amendments on bioretention performance for stormwater management
Alex Taylor, Jill Wetzel, Emma Mudrock, Kennith King, J. W. Davis, James Cameron, Jenifer K. McIntyre
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Abstract
New permits in Washington State for the National Pollutant Discharge and Elimination System (NPDES) are requiring the use of low impact development (LID) and green stormwater infrastructure (GSI) where feasible. Bioretention—infiltration into soil—is expected to be among the most commonly utilized techniques. Previous replicated mesocosm studies at Washington State University (WSU) and the Washington Stormwater Center (WSC) indicate that while bioretention soil can dramatically reduce the toxicity of urban stormwater, the role of plants may be limited to aesthetics and hydrologic performance. Recent studies have also indicated that wood-decomposing fungi can be incorporated into the wood mulch used in bioretention and can provide unique environmental services such as enhanced removal of microbial pathogens and degradation of PAHs. A multi-year WSU/WSC study is underway to evaluate the effects of bioretention soil parameters, the deciduous shrub Pacific Ninebark (Physocarpus capitatus), and the mycelium of the white rot saprobic Wine Cap mushroom (Stropharia rugoso-annulata) on the toxicity and water quality of bioretention-treated stormwater under field conditions. Four treatment mesocosms (no plants / no fungi; plants / no fungi; no plants / fungi; plants / fungi) have been installed in triplicate in Seattle, WA and receive runoff in real-time from a busy interstate highway as part of an urbanized watershed. Quarterly sampling of influent stormwater and treated effluent over two years is in process to determine the potential for toxicant break-through under field-relevant loading conditions. Known stormwater toxicants including PAHs, Cu, Zn, and Pb, among others, are being monitored and toxic effects in zebrafish (Danio rerio) embryos including survival, developmental abnormalities, and cardiac function after 48 h exposure are being assessed. Results from the first year of the study are reported.