Preprints
https://doi.org/10.5194/egusphere-2023-1039
https://doi.org/10.5194/egusphere-2023-1039
07 Jun 2023
 | 07 Jun 2023

Source Apportionment of PM2.5 in Montréal, Canada and Health Risk Assessment for Potentially Toxic Elements

Nansi Fakhri, Robin Stevens, Arnold Downey, Konstantina Oikonomou, Jean Sciare, Charbel Afif, and Patrick L. Hayes

Abstract. Source apportionment of PM2.5 was performed using positive matrix factorization (PMF) based on detailed chemical composition data from 24-h filters collected over 3-months period (August–November 2020) at an urban site in Montréal, a Canadian city with a population of approximately 4 million people. This source apportionment study, which examined the main contributing sources to PM2.5 using a large suit of organic molecular markers, is the first of its sort in Canada. A focus of this study was on quantifying previously unresolved sources of PM2.5 through the inclusion in the PMF analysis of additional organic molecular markers beyond those measured typically by the Canadian government’s National Air Pollution Surveillance Program (NAPS). The organic species included in the PMF model were namely, n-alkanes, hopane, fatty acids, dicarboxylic acids, and biogenic secondary organic aerosols (SOA) tracers. Secondary inorganic aerosols (SIA) and SOA were the dominant components and constituted 39 % of the measured PM2.5 mass while the local primary anthropogenic sources, namely traffic exhaust, road dust, industrial, and cooking emissions contributed 23 %. The chemical transport model GEOS-Chem revealed that ammonium sulfate concentrations in Montréal are strongly influenced by both local sources in Québec and transboundary input from the United States, with the transboundary input exceeding the local emissions for SOA. Co and Cr(VI) presented an elevated cancer risk, highlighting that more attention should be given to these trace metals, which were associated with industrial emissions by the PMF analysis. Furthermore, the results showed that industrial emissions were minor contributors to the total PM2.5 mass, but the largest contributors to Co and Cr(VI) concentrations. Thus, the health hazards associated with this source cannot be entirely established by the PM2.5 mass concentration alone. This study highlights that, when evaluating air quality in Montréal and other urban regions, the prioritization of sources for mitigations strategies will diverge if one considers total PM2.5 mass concentration or the concentration of individual particulate-bound contaminants. Furthermore, the large transboundary contribution from the United States to total PM2.5 levels suggests that future municipal, provincial and federal monitoring and regulations would be more effective if they focus on specific high-risk contaminants (e.g., Co and Cr(VI) rather than total PM2.5.

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Journal article(s) based on this preprint

29 Jan 2024
Source apportionment of PM2.5 in Montréal, Canada, and health risk assessment for potentially toxic elements
Nansi Fakhri, Robin Stevens, Arnold Downey, Konstantina Oikonomou, Jean Sciare, Charbel Afif, and Patrick L. Hayes
Atmos. Chem. Phys., 24, 1193–1212, https://doi.org/10.5194/acp-24-1193-2024,https://doi.org/10.5194/acp-24-1193-2024, 2024
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.

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The chemical composition of PM2.5 and emission sources as well as potential human health risk...
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