Characterization of winter air pollutant gradients near a major highway

Cheol-Heon Jeong; Nathan Hilker; Jon M Wang; Jerzy Debosz; Robert M Healy; Uwayemi Sofowote; Tony Munoz; Dennis Herod; Greg J Evans

doi:10.1016/j.scitotenv.2022.157818

Characterization of winter air pollutant gradients near a major highway

Sci Total Environ. 2022 Nov 25:849:157818. doi: 10.1016/j.scitotenv.2022.157818. Epub 2022 Aug 5.

Authors

Cheol-Heon Jeong¹, Nathan Hilker², Jon M Wang³, Jerzy Debosz⁴, Robert M Healy⁴, Uwayemi Sofowote⁴, Tony Munoz⁴, Dennis Herod⁵, Greg J Evans²

Affiliations

¹ Southern Ontario Centre for Atmospheric Aerosol Research, University of Toronto, Toronto, Ontario, Canada. Electronic address: ch.jeong@utoronto.ca.
² Southern Ontario Centre for Atmospheric Aerosol Research, University of Toronto, Toronto, Ontario, Canada.
³ Southern Ontario Centre for Atmospheric Aerosol Research, University of Toronto, Toronto, Ontario, Canada; Air Monitoring and Transboundary Air Sciences Section, Ministry of the Environment, Conservation and Parks, Toronto, Ontario, Canada.
⁴ Air Monitoring and Transboundary Air Sciences Section, Ministry of the Environment, Conservation and Parks, Toronto, Ontario, Canada.
⁵ Analysis and Air Quality Section, Air Quality Research Division, Science and Technology Branch, Environment and Climate Change Canada, Ottawa, Ontario, Canada.

PMID: 35940272
DOI: 10.1016/j.scitotenv.2022.157818

Abstract

Traffic-related air pollutants (TRAP) including nitric oxide (NO), nitrogen oxide (NO_x), carbon monoxide (CO), ultrafine particles (UFP), black carbon (BC), and fine particulate matter (PM_2.5) were simultaneously measured at near-road sites located at 10 m (NR10) and 150 m (NR150) from the same side of a busy highway to provide insights into the influence of winter time meteorology on exposure to TRAP near major roads. The spatial variabilities of TRAP were examined for ambient temperatures ranging from -11 °C to +19 °C under downwind, upwind, and stagnant air conditions. The downwind TRAP concentrations at NR10 were higher than the upwind concentrations by a factor of 1.4 for CO to 13 for NO. Despite steep downwind reductions of 38 % to 75 % within 150 m, the downwind concentrations at NR150 were still well above upwind concentrations. Near-road concentrations of NO_x and UFP increased as ambient temperatures decreased due to elevated emissions of NO_x and UFP from vehicles under colder temperatures. Traffic-related PM_2.5 sources were identified using hourly PM_2.5 chemical components including organic/inorganic aerosol and trace metals at both sites. The downwind concentrations of primary PM_2.5 species related to tailpipe and non-tailpipe emissions at NR10 were substantially higher than the upwind concentrations by a factor of 4 and 32, respectively. Traffic-related PM_2.5 sources accounted for almost half of total PM_2.5 mass under downwind conditions, leading to a rapid change of PM_2.5 chemical composition. Under stagnant air conditions, the concentrations of most TRAP and related PM_2.5 including tailpipe emissions, secondary nitrate, and organic aerosol were comparable to, or even greater than, the downwind concentrations under windy conditions, especially at NR150. This study demonstrates that stagnant air conditions further widen the traffic-influenced area and people living near major roadways may experience increased risks from elevated exposure to traffic emissions during cold and stagnant winter conditions.

Keywords: Air stagnation; Near-road; Non-tailpipe emissions; Tailpipe emissions; Traffic-related air pollutant; Winter gradient.

MeSH terms

Aerosols
Air Pollutants* / analysis
Air Pollution* / analysis
Carbon Monoxide
Environmental Monitoring
Humans
Nitrates
Nitric Oxide
Nitrogen Oxides / analysis
Particulate Matter / analysis
Vehicle Emissions / analysis

Substances

Aerosols
Air Pollutants
Nitrates
Nitrogen Oxides
Particulate Matter
Vehicle Emissions
Nitric Oxide
Carbon Monoxide