title: Role of snow in the fate of gaseous and particulate exhaust pollutants from gasoline-powered vehicles.
abstract: Little is known about pollution in urban snow and how aerosol and gaseous air pollutants interact with the urban snowpack. Here we investigate interactions of exhaust pollution with snow at low ambient temperature using fresh snow in a temperature-controlled chamber. A gasoline-powered engine from a modern light duty vehicle generated the exhaust and was operated in homogeneous and stratified engine regimes. We determined that, within a timescale of 30 min, snow takes up from the exhaust a large mass of organic pollutants and aerosol particles, which were observed by electron microscopy, mass spectrometry and aerosol sizers. Specifically, the concentration of total organic carbon in the exposed snow increased from 0.948 ± 0.009 to 1.828 ± 0.001 mg/L (homogeneous engine regime) and from 0.275 ± 0.005 to 0.514 ± 0.008 mg/L (stratified engine regime). The concentrations of benzene, toluene and 13 out of 16 measured polycyclic aromatic hydrocarbons (PAHs), particularly naphthalene, benz[a]anthracene, chrysene and benzo[a]pyrene in snow increased upon exposure from near the detection limit to 0.529 ± 0.058, 1.840 ± 0.200, 0.176 ± 0.020, 0.020 ± 0.005, 0.025 ± 0.005 and 0.028 ± 0.005 ng/kg, respectively, for the homogeneous regime. After contact with snow, 50-400 nm particles were present with higher relative abundance compared to the smaller nanoparticles (<50 nm), for the homogeneous regime. The lowering of temperature from 25 ± 1 °C to (-8) - (-10) ± 1 °C decreased the median mode diameter of the exhaust aerosol particles from 69 nm to 57 nm (p < 0.1) and addition of snow to 51 nm (p < 0.1) for the stratified regime, but increased it from 20 nm to 27 nm (p < 0.1) for the homogeneous regime. Future studies should focus on cycling of exhaust-derived pollutants between the atmosphere and cryosphere. The role of the effects we discovered should be evaluated as part of assessment of pollutant loads and exposures in regions with a defined winter season.
authors.affiliation: Department of Atmospheric and Oceanic Sciences, McGill University, 805 Sherbrooke Street West, Montreal, QC H3A 0B9, Canada.
authors.forename: Yevgen
authors.initials: Y
authors.lastname: Nazarenko
authors.affiliation: Department of Mechanical Engineering, École de Technologie Supérieure, 1100 Notre-Dame Street West, Montreal, QC H3C 1K3, Canada.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Fournier
authors.affiliation: Department of Atmospheric and Oceanic Sciences, McGill University, 805 Sherbrooke Street West, Montreal, QC H3A 0B9, Canada.
authors.forename: Uday
authors.initials: U
authors.lastname: Kurien
authors.affiliation: Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, QC H3A 2K6, Canada.
authors.forename: Rodrigo Benjamin
authors.initials: RB
authors.lastname: Rangel-Alvarado
authors.affiliation: PO-Laboratories, Inc., 609 McCaffrey Street, Saint-Laurent, QC H4T 1N3, Canada.
authors.forename: Oleg
authors.initials: O
authors.lastname: Nepotchatykh
authors.affiliation: Department of Mechanical Engineering, École de Technologie Supérieure, 1100 Notre-Dame Street West, Montreal, QC H3C 1K3, Canada. Electronic address: patrice.seers@etsmtl.ca.
authors.forename: Patrice
authors.initials: P
authors.lastname: Seers
authors.affiliation: Department of Atmospheric and Oceanic Sciences, McGill University, 805 Sherbrooke Street West, Montreal, QC H3A 0B9, Canada; Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, QC H3A 2K6, Canada. Electronic address: parisa.ariya@mcgill.ca.
authors.forename: Parisa A
authors.initials: PA
authors.lastname: Ariya
mesh_terms: D000336:Aerosols / Q000032:analysis; D000393:Air Pollutants / Q000032:analysis / Q000737:chemistry*; D001272:Atmosphere / Q000737:chemistry; D002170:Canada; D003080:Cold Temperature; D004784:Environmental Monitoring; D005740:Gases / Q000737:chemistry*; D005742:Gasoline; D052638:Particulate Matter / Q000032:analysis / Q000737:chemistry*; D012621:Seasons; D012914:Snow / Q000737:chemistry*; D001335:Vehicle Emissions / Q000032:analysis*; D055549:Volatile Organic Compounds / Q000032:analysis / Q000737:chemistry
chemical_list: D000336:Aerosols; D000393:Air Pollutants; D005740:Gases; D005742:Gasoline; D052638:Particulate Matter; D001335:Vehicle Emissions; D055549:Volatile Organic Compounds
keywords: Assessment; BTEX; Exhaust; PAH; Particulate matter; Snow; Vehicles