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Graduate student Houjie Li and Professor Parisa Ariya discovered that the concentrations of black carbon (BC), PM_2.5, CO, NO_x decreased up to 72% in downtown Montreal during COVID-19 lockdown period, revealing those human activities account for most air pollutants in the cities.

BC wis the by-product of combustion of fossil fuel and biomass burning that can strongly absorb solar radiation, playing an important role in climate change. The researchers in the Department of Chemistry found the concentration of BC would maintain high level during wintertime, in contrast to cites in warmer climate. Moreover, the researchers revealed that the concentration of BC in the ambient air at YUL Airport was 400% higher than that in downtown Montreal. Yet currently there is no regulatory policy on it, which poses great threat on health of local residents. The researchers call for more public attention on this problem.

Anthropogenic air pollutants have been of great interests in the past decades because of health concern and climate impact. In normal days, it鈥檚 not easy to clearly distinguish anthropogenic air pollutants from those from natural sources in urban aera. However, the COVID-19 pandemic provided researchers a chance to evaluate the large impacts of anthropogenic source of air pollutants around the world.

About the study:

鈥淏lack Carbon Particles Physicochemical Real-Time Data Set in a Cold City: Trends of Fall-Winter BC Accumulation and COVID-19鈥�, by Houjie Li & Parisa A. Ariya, in Journal of Geophysical Research-Atmospheres.