Within-City Spatial Variations in Multiple Measures of PM2.5 Oxidative Potential in Toronto, Canada.

Abstract

Few studies have characterized within-city spatial variations in the oxidative potential of fine particulate air pollution (PM2.5). In this study, we evaluated multiple measures of PM2.5 oxidative potential across Toronto, Canada (2016-2017), including glutathione/ascorbate-related oxidative potential (OPGSH and OPAA) and dithiothreitol depletion (OPDTT). Integrated 2-week samples were collected from 67 sites in summer and 42 sites in winter. Multivariable linear models were developed to predict OP based on various land use/traffic factors, and PM2.5 metals and black carbon were also examined. All three measures of PM2.5 oxidative potential varied substantially across Toronto. OPAA and OPDTT were primarily associated with traffic-related components of PM2.5 (i.e., Fe, Cu, and black carbon) whereas OPGSH was not a strong marker for traffic during either season. During summer, multivariable models performed best for OPAA ( RCV2 = 0.48) followed by OPDTT ( RCV2 = 0.32) and OPGSH ( RCV2 = 0.22). During winter, model performance was best for OPDTT ( RCV2 = 0.55) followed by OPGSH ( RCV2 = 0.50) and OPAA ( RCV2 = 0.23). Model parameters varied between seasons, and between-season differences in PM2.5 mass concentrations were weakly/moderately correlated with seasonal differences in OP. Our findings highlight substantial within-city variations in PM2.5 oxidative potential. More detailed information is needed on local sources of air pollution to improve model performance.