John Wiley & Sons, Ltd.

Bioswales reduce contaminants associated with toxicity in urban stormwater

Contamination and toxicity associated with urban stormwater runoff are a growing concern because of the potential for receiving system impacts. California water regulators are mandating implementation of green infrastructure as part of new urban development projects to treat stormwater and increase infiltration. Parking lot bioswales are low impact development practices that promote filtering of runoff through plants and soil. Studies have demonstrated that bioswales reduce concentrations of suspended sediments, metals, and hydrocarbons. There have been no published studies evaluating how well these structures treat current‐use pesticides, and studies have largely ignored whether bioswales reduce surface water toxicity. Three storms were monitored at three commercial and residential sites and reductions of contaminants and associated toxicity were quantified. Toxicity testing showed that the majority of untreated stormwater samples were toxic to amphipods (H. azteca) and midges (C. dilutus), and toxicity was reduced by the bioswales. No samples were toxic to daphnids (C. dubia) or fish (P. promelas). Contaminants were significantly reduced by the bioswales, including suspended solids (81% reduction), metals (81% reduction), hydrocarbons (82% reduction), and pyrethroid pesticides (74% reduction). The one exception was the phenypyrazole pesticide fipronil, which showed inconsistent treatment. The results demonstrate these systems effectively treat contaminated stormwater associated with surface water toxicity, but suggest modifications of their construction may be required to treat some contaminant classes. This article is protected by copyright. All rights reserved

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