Identification of the Major Sources Contributing to PM_2.5Observed in Toronto

Abstract

The chemical composition of Toronto PM2.5 was measured daily from Feb 2000 to Feb 2001, and source apportionment was undertaken using positive matrix factorization (PMF). In Toronto, PM2.5 levels were influenced both by local urban activities and also by regional-scale transport. Although several PMF solutions were possible, an eight-source model for explaining the observed Toronto PM2.5 was found to provide realistic results and interesting insights into sources. The four main sources were coal combustion related to regional transport and secondary sulfate (26%), secondary nitrate related to both local and upwind sources of NOx and NH3 (36%), secondary organic aerosols (SOA) formed from a variety of precursor organic emissions (15%), and motor vehicle traffic (10%). The other detectable sources were road salt (winter) and three types of primary PM2.5 hypothesized to be associated with smelters, coal and oil combustion, industry, and local construction. Overall, motor vehicle-related emissions (including road salt and nitrate) were estimated to be responsible for about 40% of the PM2.5. In the summer, the SOA mass was estimated to contribute approximately 20% to the PM2.5. Inclusion of water-soluble, low-molecular-weight organic acids led to identification of this component, thus providing a significant improvement in PMF's ability to resolve sources. Without organic acid measurements the SOA portion of the observed PM2.5 was assigned to the secondary coal component, increasing its contribution and resulting in a source profile with an unrealistic amount of organic mass. This suggests that in the northeastern part of North America, there are physical and/or chemical processes that lead to close interaction between secondary organic and inorganic aerosols.

Chemical speciation of fine particle bound trace metals

“…At the roof level, the average concentrations of those 12 elements were 2724 (Al), 1908 (Fe), 570.3 (Zn), 212.3 (Pb), 72.19 (Mn), 53.55 (Cu), 25.64 (As), 9.764 (Cr), 6.345 (Ni), 4.732 (Cd), 2.185 (Mo) and 0.816 ng/m 3 (Co). These data are comparable to those reported by Wang et al, (2006) and Duan et al (2006) for Guangzhou and Beijing, but are much higher than major cities around the world where more strict emission standards are applied (Ariola et al, 2006;Lee et al, 2003;Louie et al, 2005;Singh et al, 2002).…”

Sources of Personal Exposure to Fine Particles in Toronto, Ontario, Canada

“…These data have been used for outdoor PM 2.5 source apportionment studies and have been described elsewhere. 9 Pollutants measured included 24-hr. (ϳ8:00 a.m. to 8:00 a.m. EST) PM, carbon, inorganic ions, water-soluble organic substances, and hourly gaseous pollutants, such as CO, nitrogen oxides (NO x ), ozone (O 3 ), and coefficient of haze.…”

“…In a recent study, an eight-source receptor model was constructed to apportion PM 2.5 in Toronto, Ontario, Canada. 9 These included coal combustion related to regional transport and secondary sulfate, secondary nitrate, secondary organic aerosols, motor vehicle traffic, road salt, and three primary PM 2.5 sources associated with smelters: coal and oil combustion, industry, and local construction. In the residential indoor environment, major sources can be cooking, vacuuming, dusting, tobacco smoke, and wood-burning fires.…”

“…Receptor models are often constructed with fixed-site monitoring station data. 9,[21][22][23][24][25] Few receptor models have been constructed to apportion multisubject personal exposures to particulate matter. 26,27 Longitudinal studies present an interesting problem for receptor models of personal exposures.…”

Megacities and Atmospheric Pollution

“…Historically, the highest SO 2 concentrations in the COR have been recorded in the vicinity of large local industrial sources. Lee et al 197 found that long-range transport contributes to the SO 4 2Ϫ pollution within the COR.…”