| The primary objective of this work was to assess the importance of local production versus long-range transport on particulate matter (PM2.5) sulphate concentrations (P-SO4) in Toronto, Ontario. To achieve this goal, a comprehensive two month dataset (July and August 2001) was compiled and analysed by statistical techniques and theoretical modelling. Over this period, the average p-SO4 contribution to PM2.5 was 20% with its relative contribution increasing with increasing PM2.5. Using factor analysis, p-SO4 was attributed to a factor with secondary gaseous species, while other particulate components were linked to primary sources. An analysis of long-range back trajectories showed that elevated p-SO4 levels were associated with air masses from the southwest direction with probable sources in the Midwestern United States. From theoretical modelling, long-range transport accounted for the majority of the observed p-SO4. Under favourable atmospheric conditions, however, local production was significant. |
