A Wintertime Investigation of Atmospheric Pollutants Deposition in the Alberta Oil Sands Region, Canada

Atmospheric deposition is a potentially important pathway of trace metals and polycyclic aromatic hydrocarbons (PAH) input to the landscape in the oil sands region of Alberta. With planned expansion of oil sands facilities, there is interest in being able to characterize the magnitude and extent of trace metal and PAH deposition in the oil sands region. A pilot study was undertaken to assess the feasibility of a bulk collection system to characterize atmospheric deposition of selected organic and inorganic contaminants in the Athabasca Oil Sands Region. The study was carried out in four sampling sites near and distant to oil sands facilities from late December 2011 to the end of March 2012 (3-month period). To check the precision of the bulk deposition method, triplicate bulk samplers were used, which were placed next to each other and as close as possible considering similar microenvironment. Monthly deposition samples were analyzed for 36 trace metals (including 13 U.S. EPA priority pollutants), ultra-low mercury, and 25 PAH (including alkylated-, parent-, and carcinogenic-PAH). At two sampling sites located within 20 km of major oil sands facilities, 3-month integrated deposition rates for some priority metals were up to 20-fold higher compared to two background sites located >45 km away from the oil sands facilities. Winter deposition rates of alkylated-PAH and parent-PAH were up to 70-fold lower at the background sampling sites than at sites near oil sands facilities. Deposition fluxes of total carcinogenic PAH were found to be 6- to 75-fold higher at the two sampling sites near oil sands development facilities compared to the north and south background sites. Another notable finding is the apparent precision of the sampling method. Median coefficient of variation for 13 priority metals were ±21% and within ±15% for both alkylated- and parent-PAH. The Athabasca oil sands region is considered a large area of current interest with respect to potential deposition of trace metals and PAH. However, access to power for any type of air pollution monitoring is, for the most part, lacking in locations at distances excess of 30 km from oil sands facilities. The bulk collection systems investigated here offer the ability to obtain direct measures of trace metal and PAH deposition in these remote areas.