A new study from SFEI assessing the ability of rain gardens to remove contaminants from urban stormwater has shown that nature-based filtration may also be a solution for microplastic pollution. This solution and others will be featured in a symposium on microplastics for scientists, policy makers, and change leaders in Berkeley on October 2nd.
The multiyear water quality performance study of a bioretention rain garden located along a major urban transit corridor evaluated the ability of these rain gardens to remove multiple pollutants. Based on data collected between 2012 and 2017, polychlorinated biphenyls (PCBs) and suspended sediment were reduced by over 90%, whereas total mercury, methylmercury, and copper were moderately captured.
Novel analyses of microplastics and other tiny, man-made particles also showed over 90% of these materials in urban stormwater were retained by the bioretention rain garden. Findings from a comprehensive scientific study of microplastics in the San Francisco Bay will be presented at the symposium on October 2nd.
Implementation of rain gardens and other green stormwater infrastructure is underway in the Bay Area, often designed and built to reduce contamination from regulated pollutants like PCBs and mercury. Further evaluation of the co-benefits provided by these nature-based stormwater treatments for removing microplastics is needed to inform potential solutions for this emerging contaminant.
Funding for the study was provided by the Association of Bay Area Governments, the California State Water Board, the US Environmental Protection Agency, and the California Department of Water Resources via Proposition 84. Additional support was provided by the San Francisco Estuary Partnership, Geosyntec Consultants, and Bay Area Stormwater Management Agencies Association.