New research from McGill University suggests that urban runoff’s toxicity for aquatic organisms may be underestimated and unmonitored, as detergents, pesticides, heavy metals, and other contaminants continue to make their way into lakes and rivers.
While some major cities have stormwater best management practices in place, the McGill team says they don’t have the ability to address anthropogenic stressors such as climate change, nutrient pollution, and habitat modification, which could often be mitigated through the implementation of green infrastructure.
In New York City alone, the researchers note that some 110 billion gallons of untreated runoff is released into natural waters every year.
The researchers suggest that international actions and policies should be implemented to control pollutant release and prevent adverse ecological impacts from tire-wear debris, cigarette butts, textile microfibres, and other plastic-based litter in stormwater runoff.
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“Densely populated cities need sustainable solutions such as retention ponds and settling tanks to simultaneously treat and store runoff,” said Nathalie Tufenkji, Professor of Chemical Engineering at McGill University and Canada Research Chair in Biocolloids and Surfaces, in a statement. “Such retention processes could act as on-site surge tanks while also removing several contaminants from runoff before discharge into natural waters,” she added.
Following intense precipitation events, other common runoff contaminants may include winter salts and de-icing chemicals applied in winter.
“Importantly, the concentrations of these contaminants are not systematically measured, while their combined toxicity effects are ill-defined and potentially underestimated,” states the study “Sustainable strategies to treat urban runoff needed” by Tufenkji, Mathieu Lapointe, and Chelsea Rochman, recently published in Nature Sustainability. “A better understanding of the loadings of contaminants and any relevant toxicity is crucial to evaluate the risk to aquatic ecosystems and determine sites where mitigation strategies are needed.”
The McGill researchers added that adequate monitoring designed to provide information about both contamination and risk is crucial for governments and scientists to establish whether more active management is needed and whether urban runoff should be treated before being released into the environment.
The researchers said that municipalities need data-driven, adapted, low-cost and sustainable solutions to protect dense urban centres.
Other sustainable solutions for urban runoff include retention ponds, bioretention cells or raingardens, coarse sand filters, bio-assisted aggregation and filtration systems, aerated ponds, underground tanks in dense urban areas, adsorption via functionalized media in a granular filter, passive aggregation and settling tanks, and passive O2/ultraviolet oxidation.