The Athabasca Oil Sands Region (AOSR) in northeastern Alberta, Canada has attracted much international attention in recent years due to the increased level of oil sands operations. A passive sampling program was initiated in 1999 to monitor ozone (O3), nitrogen dioxide (NO2) and sulfur dioxide (SO2) in the AOSR for the estimation of the exposure of the forest monitoring sites and the characterization of temporal trends. Since 1999, highest concentrations of O3 and NO2 occurred in April and winter, respectively. The observed spring O3 maximum is common in the northern hemisphere. The higher winter-time NO2 concentrations were due to low atmospheric mixing height, stable atmosphere, and higher emissions during winter.
Sen-Theil trend analysis, a non-parametric analysis for temporal trending, determined that O3 concentrations from 2000 to 2009 did not change. NO2 concentrations increased slightly at three sites, and significantly increased at two sites closer to stationary and mobile sources. SO2 concentration was increasing at JP107 and was decreasing at JP101. SO2 concentrations did not increase at 4 other sites close to the major emissions. This suggests that SO2 emissions were likely stable.
Spatial analysis was conducted to characterize the concentration distribution in the region. The O3 concentrations were low near the emission sources (9.4 km) likely due to local O3 titration. Highest NO2 and SO2 concentrations were measured near the main source area. Generally, passively measured monthly average concentrations of O3, NO2 and SO2 stabilized at 20, 48 and 48 km from the main source area suggesting NO2 and SO2 emission influences were limited to < 50 km away from the major sources. However, one site (JP107) located near the Athabasca River Valley, 94 km north of the main source area, had higher SO2 and NO2 concentrations. This could be attributed to influence of valley flow, and/or to additional sources added in the region since 2007.