Identification of ambient SO2 sources in industrial areas in the lower Athabasca oil sands region of Alberta, Canada

With ongoing interest in sulfur dioxide (SO2) levels approaching a new Canadian Ambient Air Quality Standards (CAAQS) in the Athabasca Oil Sands Region (AOSR), an exploratory study was undertaken to identify potential local emission sources that influence ambient SO2 concentrations. The approach used in this study was to apply the receptor model positive matrix factorization (PMF) using ambient measurement data of PM10 components (metals and ion species), gaseous pollutants and volatile organic compound (VOC) species from two industrial air monitoring stations (i.e., AMS13-Fort McKay South and AMS15-CNRL Horizon) over a 3-year period (2015-2017). Results were then used to examine receptor model-defined sources for which SO2 was a statistically strong predictor. Eleven sources were tentatively identified: a mixed oil sands, stack emissions & fugitive dust factor, a haul road dust factor, an aged air mass & biogenic factor, secondary inorganic aerosol, a W-Co-Bi-SO2-rich factor, oil sands mixed fugitives and a mixed industrial and off-road traffic factor. No significant variation was observed in inferred contributions of major SO2-related sources among the two air monitoring stations investigated. These preliminary findings offer insights about different source emissions that influence ambient SO2 concentrations in the AOSR. We suggest there may be potential application of this approach to other settings where similar datasets are available and there is interest in understanding sources affecting ambient SO2 levels.