Abstract View
Intra-city Factors Obtained from Dispersion-normalized Multi-time Resolution Factor Analyses of PM2.5 in an Urban Environment
Uwayemi Sofowote, Robert Healy, Yushan Su, Jerzy Debosz, Michael Noble, Anthony Munoz, Cheol H. Jeong, Jonathan Wang, Nathan Hilker, Greg J. Evans, Jeff Brook, Gang Lu, PHILIP K. HOPKE, University of Rochester
Abstract Number: 3
Working Group: Urban Aerosols
Abstract
Ambient fine particulate matter data of continuously monitored species at two air monitoring sites within Toronto were used to gauge the intra-city variations in PM composition over a two-year period. One location was beside a major highway while the other was an urban background location. In this work, we specially pretreated the concentrations of the measured species (dispersion-normalization) to reduce the influence of local meteorology before applying multi-time resolution factor analysis to identify and quantify source contributions. Factors found were pSO4, pNO3, secondary organic aerosols (SOA), and crustal matter (CrM) that were common to both sites, a hydrocarbon-like organic matter (HOM) exclusive to the urban background site, three black carbon related factors (BC, BC-HOM at the highway site, and a brown carbon rich factor (BC-BrC) at the urban background site), biomass burning organic matter (BBOM) and brake dust (BD) at the highway site. This talk will discuss the dispersion-normalization and present the differences in PM2.5 composition for the regional and local factors between these two locations that were only 10 km apart. Site-specific factors are of greater interest for control policy design. Thus, regressions with potential explanatory, site-specific variables were performed for results from the highway site. Three regression model approaches were explored (MLR, GRG regression, and the generalized additive model GAM). GAM gave the largest R2 for the locally-sourced factors. Heavy duty vehicles were most important for explaining the black carbon (BC and BC-HOM) factors. Light-duty vehicles were dominant for BD. Auxiliary modelling for the local factors showed that the traffic-related factors likely originated along the main roadways at their sites while the more regional factors, - pSO4, pNO3, SOA, - had sources that were both regional and local. These results will be useful in understanding ambient particulate matter sources on a city scale.