University of Saskatchewan (USask) College of Engineering graduate student Hayley Popick and her research team are investigating how contaminants generated from the City of Saskatoon may be affecting the water supply and ecosystems of the South Saskatchewan River.
“Stormwater can be as polluted as untreated wastewater or sewage when it enters our natural water bodies,” said Popick.
Potential contaminants in stormwater runoff include heavy metals and solids from human activities such as road salting, yard and pet waste buildup, and the use of fertilizers. Materials can also leach from vehicles, including oil and gasoline.
“Highly polluted stormwater discharges can result in consequences as severe as the Great Lakes algal blooms of the 1970s, and in recent years rubber tire vulcanizing compounds have been linked to urban runoff mortality syndrome (also known as pre-spawn mortality) in coho salmon.”
She said contamination levels can be particularly high after rain or snowmelt and can have significant health effects for both animals and humans.
“Beyond tire vulcanizers, stormwaters typically contain high concentrations of dissolved metals and polycyclic aromatic hydrocarbons (the drippings and emissions from vehicles and roads), which are implicated in cancers, cell damage, organ failure, and many other health issues in plants, aquatic animals, and humans alike,” said Popick.
“This research explored the sources of some of these compounds and how they might reach local water bodies.”
To analyze the contaminant content of Saskatoon stormwaters and snowmelts, the research team took samples of water during summer storms from city storm sewers and collected snowmelt samples from city snow dump sites.
Popick’s research was supervised by associate professor of civil, geological and environmental engineering Dr. Kerry McPhedran (PhD), and assistant professor in the USask School of Environment and Sustainability Dr. Markus Brinkmann (PhD).
Following lab analysis of the stormwater samples, Popick’s team discovered that certain activities performed right before a storm—such as road tarring or paving—can cause increased hydrocarbon contamination levels, as stormwater flows through city systems.
Results also indicated that the road-salt-chloride amount present in city snowmelt samples caused the water to contain similar salt levels to that of seawater, rather than freshwater.
“Smaller, easily-dissolved particles like road salt will ‘drain’ out of the pack with melting snow first, while larger or non-dissolvable particles like sand or oil residues remain inside the snowpack,” said Popick on the behaviour of contaminants in snowmelt.
The research team also analyzed the toxicity of the Saskatoon water samples to living organisms such as Vibrio fischeri marine bacteria or Raphidocelis subcapitata green algae.
Interestingly, the summer stormwater samples were not found to be toxic to either organism, but the salt-filled snowmelt samples were found to cause almost complete bioluminescence inhibition in V. fischeri. This could mean “the majority of toxic impact of the stormwater may therefore lie in its sediments instead, while snowmelt effluents remain toxic after filtration.”
Results of the study examining tire vulcanizer levels in Saskatoon stormwater have been published in Environmental Science and Technology Letters along with co-author and USask post-doctoral fellow Dr. Jonathan Challis (PhD). Two further papers are under review.
The study’s variable findings will “allow the city to minimize the contaminants being generated by locating and removing point sources of contamination, using less harmful materials, implementing landscaping controls, and upgrading infrastructure, among other strategies.”
Popick said possible solutions to mitigate contamination levels could be new road grit or paving strategies that lessen the environmental impact, implementing more landscaping controls such as vegetative swales or stormwater ponds, or upgrading infrastructure such as management controls in snow facilities.
“Ultimately, the research itself can lead to the development of accurate stormwater/snowmelt models for the city, which can be used to predict and monitor contamination levels and further refine management.”
The research has been funded by the City of Saskatoon, the Natural Sciences and Engineering Council of Canada Engage grant program and the Canadian Foundation for Innovation.
This article first ran as part of the 2022 Young Innovators series, an initiative of the USask Research Profile and Impact office in partnership with the Saskatoon StarPhoenix.