Source Apportionment of Wintertime Organic Pollutants in a Canadian Megacity: Insights from Particle and Gas Phase Measurements
Spiro Jorga, LAURA-HELENA RIVELLINI, Yutong Wang, Jonathan Abbatt,
University of Toronto Abstract Number: 61
Working Group: Source Apportionment
AbstractDespite extensive studies on air pollution during summertime, limited research has been conducted on wintertime air pollution, where sources may differ, and the lower boundary layer and reduced oxidation levels can lead to unique atmospheric interactions. To address this knowledge gap, we conducted a study during the winter of 2023 in Toronto, a Canadian megacity, to investigate the sources and processes of particle and gaseous pollutants and their connections to each other. The temperature during that period ranged from -20
oC to 15
oC. A high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and a Proton Transfer-Reaction Mass Spectrometer (PTR-MS) were deployed, along with measurements of particle size distribution from 14 nm to 10 μm, and black carbon concentration using a PAX. The average PM
1 concentration was found to be 9 μg m
-3 and was dominated by organics, which accounted for 70% of the mass, followed by nitrate (15%), ammonium (7%), sulfate (5%), black carbon (2%), and chloride (1%).
Positive Matrix Factorization (PMF) of the AMS and PTR-MS measurements revealed the main sources of particulate and volatile organic pollutants. We observed identifiable signals and similar time trends from mobile, cooking, and oxidation within both the gas and particles factors. The oxygenated organic aerosol (OOA) was identified as the dominant source of organic matter, accounting for 56% of the total organic aerosol, followed by cooking OA (COA) at 20%, traffic hydrocarbon-like OA (HOA) at 13%, and a combustion-like OA (combOA) at 11%. Based on correlations with particle and other gas phase measurements, the identified PMF factors from the PTR-MS measurements were: organic background (48%), mobile sources factor (20%), cooking factor (18%), a factor related to diesel vehicles (8%), and one human-connected factor (7%).