Source Contributions to Ambient Fine Particulate Matter for Canada.

Understanding the sectoral contribution of emissions to fine particulate matter (PM) offers information for air quality management, and for investigation of association with health outcomes. This study evaluates the contribution of different emission sectors to PM in 2013 for Canada using the GEOS-Chem chemical transport model, downscaled with satellite-based PM. Despite the low population-weighted PM concentrations of 5.5 μg m across Canada, we find that over 70% of population-weighted PM originates from Canadian sources followed by 30% from the contiguous United States. The three leading sectoral contributors to population-weighted PM over Canada are wildfires with 1.0 μg m (17%), transportation with 0.96 μg m (16%), and residential combustion with 0.91 μg m (15%). The relative contribution to population-weighted PM of different sectors varies regionally with residential combustion as the leading contributor in Central Canada (19%), while wildfires dominate over Northern Canada (59%), Atlantic Canada (34%), and Western Canada (18%). The contribution from U.S. sources is larger over Central Canada (33%) than over Western Canada (17%), Atlantic Canada (17%), and Northern Canada (<2%). Sectoral trend analysis showed that the contribution from anthropogenic sources to population-weighted PM decreased from 7.1 μg m to 3.4 μg m over the past two decades.