ICMGP - Conference Presentation

Abstract Information :

Oil sands upgrading facilities in the Athabasca Oil Sands Region (AOSR) in Alberta,
Canada, have been reporting mercury (Hg) emissions since 2000, yet the impact of these emissions on the environment remains unknown. A process-based Hg model, GEM-MACH-Hg, was applied to simulate the Hg burden in and around the AOSR from 2012 to 2015. The impact of oil sands developments on Hg levels in the AOSR, relative to contributions from other sources such as global anthropogenic and wildfires emission influencing Hg levels in the region, was assessed. The relative importance of year-to-year changes in emissions from the above sources and meteorological conditions to inter-annual variations in Hg deposition was examined. As a result of global-scale transport and long lifetime of gaseous elemental Hg (Hg(0)), surface air concentrations of Hg(0) in the AOSR reflected the background Hg(0) levels in Canada. By comparison, ambient concentrations of total oxidized Hg in the AOSR were elevated above background levels up to 60% within 50 km of the oil sands Hg emission sources. Hg emissions from wildfire events led to episodes of high ambient Hg(0) concentrations and deposition enrichments in northern Alberta. On a broad spatial scale, imported Hg from global sources dominated the annual background deposition in the AOSR, with present-day anthropogenic emissions contributing to 40%, and geogenic and legacy mercury emissions contributing to 60% of background Hg deposition. Oil sands emissions were responsible for significant enhancements in Hg deposition in the immediate vicinity of oil sands emission sources, which were about 10 times larger in winter than summer. The spatial extent of the oil sands emissions influence on Hg deposition was also greater in winter relative to summer (~100 km vs 30 km). Wintertime deposition also displayed higher inter-annual variations due to changes in meteorological conditions and oil sands Hg emissions.