Characterizing the sources of air pollution in Quebec

Health Canada estimates that each year 14,400 deaths in Canada are caused by exposure to air pollution from human sources. However, the quantification of the sources of air pollution to identify specific regions or activities responsible for poor air quality remains difficult. Fine particles (PM_2.5) are a particularly important example, since they are often responsible for poor air quality in major cities. These particles are composed of thousands of different organic and inorganic compounds and can be transported over long distances and across continents. This seminar will present two approaches for quantifying the sources of air pollution in Quebec. First, positive matrix factorization (PMF) analysis is applied to PM_2.5 composition data collected for 2014 – 2016 at several monitoring sites throughout the province in order to identify the major components of PM_2.5. The highest PM_2.5 levels tend to be observed in wintertime, which PMF analysis attributes to increases in PM_2.5 associated with residential wood burning and road salt, as well as ammonium nitrate aerosol. The other major components quantified include PM_2.5 associated with industrial and vehicular emissions, as well as organic, ammonium sulfate, and mineral dust aerosols. Second, we use chemical transport modeling, specifically GEOS-Chem, to evaluate the impact of pollution emissions outside of Quebec on air quality within the province. By running simulations with and without anthropogenic emissions from the US, we find that up to 50% of PM_2.5 in Quebec is due to airborne transport across the US-Canada border. These results highlight certain sources that could be targeted to improve air quality in Quebec, but they also suggest that the benefits of reducing emissions in the province will be limited by a substantial transboundary contribution from the US.