'Toxic cocktail' concerns as snow begins to melt
Wednesday, April 5, 2017, 8:27 PM - It's not just dog waste and garbage that come to light during the spring thaw.
Researchers from McGill University and École de technologie supérieure in Montreal, Quebec say snow in urban areas absorbs a "toxic cocktail" from car emissions over the winter, which eventually is released as the weather warms up.
"We found that snow absorbs certain polycyclic aromatic hydrocarbons which are organic pollutants known to be toxic and carcinogenic," researcher Yevgen Nazarenko said in a McGill media release.
The scientists conducted an experiment by taking snow and exposing it to engine exhaust in a frozen glass sphere. They discovered that exhaust fumes are affected differently in the cold and snow depending on the type of fuel injection in the engine.
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"When one goes outdoors in winter, and there is fresh snow, one can sense the air has a different smell—it usually smells 'crisper,'" said Nazarenko. "Once the snow has been on the ground for some time, the effect goes away. When the weather warms up, the air acquires yet another smell. This is what led us to wonder about how exactly snow interacts with air pollutants."
The team also found that snow absorbs airborne particulate matter and actually alters the concentrations of different nanoparticles, which are the smallest particles found in air pollution. These nanoparticles have been linked to numerous health complications.
"Unexpectedly, colder temperatures and interaction with snow increased the relative presence of smaller nanoparticles in the polluted air above the snow," the release noted.
According to the scientists, at least 8 million people die globally due to air pollution.
"Understanding how these pollutants interact with the environment, including snow, is crucial if we are to reduce the hundreds of thousands of premature deaths caused by mild air pollution in North America," professor Parisa Ariya said in the release.
Air pollutants change in the snowpack and undergo chemical transformations, with some compounds either evaporating or accumulating in the snow before being released with meltwater.
"These releases could lead to a higher short-term concentration of certain pollutants in the air, soil and surface water bodies where the meltwater runs to," said Nazarenko.
The scientists hope to continue their research to help identify the most harmful pollutants, which will be useful in order to optimize future engine development and exhaust treatment technologies.
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