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Via combining aerosol vertical profiles from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) and assimilated multi-layer wind profiles from the Modern-Era Retrospective analysis for Research and Applications version 2 (MERRA-2), the horizontal aerosol cross-boundary transport for the Edmonton-Calgary Corridor (ECC) during 2011–2017 was characterized on the basis of aerosol extinction flux. The western and northern boundaries (WB and NB) were revealed as the two aerosol importing gateways for ECC, with the annual mean cross-boundary efficiencies of 0.286 ± 0.231 hr−1 for WB and 0.050 ± 0.025 hr−1 for NB. The annual mean efficiency of the cross eastern boundary (EB) aerosol transport was −0.267 ± 0.243 hr−1, indicating an overall aerosol exporting effect for ECC. More efficient cross southern boundary (SB) aerosol importing processes were found in July (0.049 ± 0.071 hr−1) and August (0.043 ± 0.058 hr−1), which favor the outbreak of Pacific Northwest wildfires. The aerosol emissions from Athabasca oil sands region (AOSR) in Alberta are unlikely to have significant impact on ECC via the cross-NB aerosol transport pathway. The annual mean aerosol extinction flow of 202 ± 2244 km2/h suggested the cross-boundary aerosol importing effect for ECC. The most significant aerosol importing effect for ECC was found in fall, indicated by seasonal mean aerosol extinction flow of 680 ± 1122 km2/h. The observed seasonal variation implied the noticeable influences of aerosol local emissions and cloud-aerosol interactions on ECC aerosol loadings in winter and summer. To obtain a complete picture of aerosol loading budget over ECC, further investigations on the dynamics of aerosol emissions and depositions happened in the ECC atmosphere remain. • The cross-boundary aerosol transport for ECC was characterized. • Smoke importing pathways for ECC during Pacific Northwest wildfires were revealed. • Aerosol emissions from AOSR are unlikely to have significant impact on ECC. [ABSTRACT FROM AUTHOR]

Traditionally, environmental authorities make regulatory policies for controlling volatile organic compound (VOC) pollution based on the mitigation of dominant VOC sources. However, the emission from each VOC source has a unique combination of VOC species of different toxicities. Without quantitatively assessing the health risk associated with each source, the effectiveness of the mitigation policy could be undermined. To address this shortcoming, we developed a new health risk-oriented source apportionment method that can provide quantitative health risk assessment and source-specific mitigation strategies for hazardous VOCs. We estimated that the integrated inhalation cancer risk (ICR) of hazardous VOCs was 7.7 × 10 -5 in Western Canada, indicating a 100% likelihood of exceeding Health Canada's acceptable risk level (1.0 × 10 -5 ). Anthropogenic sources were responsible for 56.3-73.8% of cancer risks across eight Canadian cities except for the regional background island, where natural sources contributed over 77% to the integrated ICR. Thus, substantial environmental and health cobenefits could be achieved via reducing the ambient levels of benzene and 1,3-butadiene by 39.3-75.7 and 14-69.3%, respectively, and mitigating emissions from fuel combustion (by 31.3-54.1%), traffic source (3.0-36.8%), and other anthropogenic sources (5.3-20.1%) in Western Canada. Our study has significant implications for prioritizing air pollution mitigation policies, especially for quantitative reduction of hazardous air pollutants.

Oil and natural gas (O&G) extraction operations emit hazardous volatile organic compounds (VOCs) in quantities that have adverse effects on human health. Our current understanding of the exposure risks associated with upstream O&G exploitations remains limited, and very few quantitative on-site remediation strategies have been proposed. To this end, we assessed the health risks associated with the emission of hazardous VOCs and presented a set of remediation goals for the city of Calgary, which is a major center of the Canadian oil industry. Results from probabilistic risk assessment (PRA) suggested that although VOCs had a negligible impact on chronic non-cancer-associated risk, inhalation-associated cancer risk remained a significant concern. Carbon tetrachloride, benzene, and 1,3-butadiene were the dominant VOCs, representing 88% of the integrated inhalation cancer risk (= 7.8 × 10 -5 ); background, solid fuel combustion, and O&G extraction were among the primary sources that posed the greatest threat to human health. Results of a Monte Carlo simulation revealed that the probability of developing cancer due to inhalation of hazardous VOCs was ∼13.1% on clean air days and 45.9% on days with significant levels of air pollution. Preliminary remediation goals (PRGs) included reductions of 24.2-65.1% and 11.4-50.9% targeting priority VOCs and their sources, respectively. Taken together, our findings suggest that stringent control of the sources of VOCs, particularly fossil fuel combustion, is an urgent priority. PRA coupled with PRGs provides informative risk assessments and suggests quantitative remediation strategies that can be applied toward improved management of hazardous pollutants., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Ambient volatile organic compounds (VOCs) in urban areas is of great interest due to their important roles in the atmospheric photochemistry as well as their potential adverse effects on public health. Limited information is available on the spatiotemporal variation, sources, and health risks of VOCs in the coastal cities of Canada, where the population density is much higher than inland areas. In this study, we investigated ambient VOCs levels, their potential sources and associated health risks in two coastal cities in Metro Vancouver during 2012-2016. Levels of the total measured VOCs were relatively higher in an industrial region in Port Moody (56.7 μg/m 3 ) than an urban area of Burnaby south (38.0 μg/m 3 ). A clear seasonality was observed for VOCs species with significantly higher levels in winter than in summer except for isoprene. Alkanes were the most dominant compounds at both sites accounting for up to 59.4% of the total measured VOCs, followed by halocarbons, aromatics, and alkenes. Industrial-related emissions (30.5%) and traffic-related emissions (35.8%) were the major sources contributing to ambient VOCs in Port Moody and Burnaby south, respectively, as calculated by the positive matrix factorization (PMF) model. A hybrid health risk assessment strategy using deterministic and stochastic approaches revealed that non-cancer risks of ambient VOCs exposure were all below the safe level of 1 at both cities, while the cumulative cancer risks of toxic VOCs exposure in Port Moody (9.2 × 10 -5 ) and Burnaby south (7.6 × 10 -5 ) were significantly higher than the provincial acceptable risk level (1.0 × 10 -5 ). Surprisingly, the probabilities for cumulative cancer risks of VOCs exceeding the US EPA tolerable risk level (1.0 × 10 -4 ) were 33.7% and 18.6% in Port Moody and Burnaby south, respectively. From a risk management perspective, greater emphasis on the reduction of emissions of carbon tetrachloride, benzene, and 1,3-butadiene is highly recommended in both cities of Metro Vancouver., (Copyright © 2019 Elsevier B.V. All rights reserved.)