Source Analysis of Pollutant Elements in Winter Air Deposition in the Athabasca Oil Sands Region: A Temporal and Spatial Study

The extraction and upgrading of bitumen have been identified as sources of enhanced atmospheric deposition of pollutant elements to ecosystems in the Athabasca Oil Sands Region (AOSR) in northern Alberta, Canada. Bitumen extraction became increasingly efficient, and oil prices surged in the 1990s, resulting in rapid expansion and increased production over the last two decades. Here, we examine temporal and spatial trends in wintertime atmospheric deposition of pollutant elements in 1978, 1981, 2008, and 2011-2016 at broad spatial scales using snowpack measurements. A hybrid source analysis was conducted, including (i) simple and multiple linear regression (MLR) of identified source locations and elemental deposition, (ii) spatially resolved aluminum enrichment factors (Al EFs), and (iii) positive matrix factorization (PMF) to determine source profiles. Temporal trends revealed a general decrease in atmospheric loadings; however, near-field V, Ti, and Al loadings in 2016 were an order of magnitude greater than at reference sites in the Peace Athabasca Delta. MLRs demonstrated that the two largest bitumen producers were major contributors of key pollutant elements (e.g., V, Al, Ti, W, Ga, Fe, Be, Cs, Co, Mo, Rb, Pb, As, U, and Ba) including rare earth elements (Y, Ce, and La). Using Al EFs, fugitive (geogenic) dust was identified as the main contributor for most elements, except for V and W, which were directly introduced by industrial sources. Results strongly suggest that fugitive dusts from petcoke piles and roads are important wintertime pollution vectors in the AOSR.