AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Apportionment of Black Carbon to Fossil Fuel and Biomass Sources in Ontario
ROBERT HEALY, Uwayemi Sofowote, Yushan Su, Jerzy Debosz, Michael Noble, Cheol H. Jeong, Jon M. Wang, Nathan Hilker, Greg J. Evans, Geoff Doerksen, Keith Jones, Tony Munoz, Ontario Ministry of the Environment and Climate Change
Abstract Number: 37 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract Black carbon (BC) is of significant interest from an air quality perspective but also due to its impacts as a short-lived climate pollutant. In this study, sources of BC in Ontario, Canada were investigated using nine concurrent Aethalometer datasets collected between June 2015 and May 2016. The sampling sites represent a mix of background and near-road locations. An optical model, based on assumed absorption Ångström exponent values, was used to estimate the relative contributions of fossil fuel combustion and biomass burning to ambient concentrations of BC at every site. The highest annual mean BC concentration (1.7 µg m-3) was observed at a Toronto highway site, where vehicular traffic was found to be the dominant source. Fossil fuel combustion was the dominant contributor to ambient BC at all sites in every season, while the highest seasonal biomass burning mass contribution (35%) was observed in the winter at a background site on the Toronto Islands, where traffic contributions are minimal. The mass absorption cross-section of BC was also investigated at two sites, where concurrent thermal/optical elemental carbon data were available, and was found to be similar at both locations. A strong seasonal dependence was observed for fossil fuel BC at every Ontario site, with mean summer mass concentrations higher than their respective mean winter mass concentrations by up to a factor of two. Using quantitative transport bias analysis (QTBA), this seasonal effect was investigated, and an increased influence from transboundary fossil fuel BC emissions originating in Michigan, Ohio, Pennsylvania and New York was identified for the summer months. The findings reported here indicate that transboundary sources of BC can impact ambient concentrations throughout southern Ontario, including the densely populated Greater Toronto Area, and that BC should not be considered as an exclusively local pollutant in future air quality policy decisions.