Trends in Passively-Measured Ozone, Nitrogen Dioxide and Sulfur Dioxide Concentrations in the Athabasca Oil Sands Region of Alberta, Canada

Received: August 23, 2012
Revised: May 2, 2013
Accepted: May 2, 2013
Download Citation: RIS|BibTeX|https://doi.org/10.4209/aaqr.2012.08.0224  

Cite this article:
Hsu, Y.M (2013). Trends in Passively-Measured Ozone, Nitrogen Dioxide and Sulfur Dioxide Concentrations in the Athabasca Oil Sands Region of Alberta, Canada. Aerosol Air Qual. Res. 13: 1448-1463. https://doi.org/10.4209/aaqr.2012.08.0224

ABSTRACT

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.

Keywords: Trend; Athabasca oil sands region; Passive sampler; Ozone; Sulfur dioxide; Nitrogen dioxide