Spatiotemporal trends of PM2.5 and its major chemical components at urban sites in Canada

Ewa Dabek-Zlotorzynska , Huanbo Wang , Leiming Zhang , Irene Cheng , Xiaohong Yao


Received July 08, 2020,Revised , Accepted September 29, 2020, Available online October 24, 2020

Volume 33,2021,Pages 1-11

To evaluate the effectiveness of emission control regulations designed for reducing air pollution, chemically resolved PM2.5 data have been collected across Canada through the National Air Pollution Surveillance network in the past decade. 24-hr time integrated PM2.5 collected at seven urban and two rural sites during 2010-2016 were analyzed to characterize geographical and seasonal patterns and associated potential causes. Site-specific seven-year mean gravimetric PM2.5 mass concentrations ranged from 5.7 to 9.6 µg/m3. Seven-year mean concentrations of SO42−, NO3, NH4+, organic carbon (OC), and elemental carbon (EC) were in the range of 0.68 to 1.6, 0.21 to 1.5, 0.27 to 0.71, 1.1 to 1.9, and 0.37 to 0.71 µg /m3, accounting for 10.8%-18.1%, 3.7%-16.7%, 4.7%-7.4%, 18.4%-21.0%, and 6.4%-10.6%, respectively, of gravimetric PM2.5 mass. PM2.5 and its five major chemical components showed higher concentrations in southeastern Canada and lower values in Atlantic Canada, with the seven-year mean ratios between the two regions being on the order of 1.7 for PM2.5 and 1.8-7.1 for its chemical components. When comparing the concentrations between urban and rural sites within the same region, those of SO42− and NH4+ were comparable, while those of NO3, OC, and EC were around 20%, 40%-50%, and 70%-80%, respectively, higher at urban than rural sites, indicating the regional scale impacts of SO42− and NH4+ and effects of local sources on OC and EC. Monthly variations generally showed summertime peaks for SO42− and wintertime peaks for NO3, but those of NH4+, OC, and EC exhibited different seasonality at different locations.

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