19 Oct 2022
19 Oct 2022
Status: this preprint is currently under review for the journal ACP.

High sulphur dioxide deposition velocities measured with the flux/gradient technique in a boreal forest in the Alberta oil sands region

Mark Gordon1, Dane Blanchard2, Timothy Jiang1,a, Paul A. Makar3, Ralf M. Staebler3, Julian Aherne2, Cris Mihele3, and Xuanyi Zhang1 Mark Gordon et al.
  • 1Earth and Space Science, York University, Toronto, M3J 1P3, Canada
  • 2Environmental and Life Science, Trent University, Peterborough, K9L 0G2, Canada
  • 3Air Quality Research Department, Environment and Climate Change Canada, Toronto, M3H 5T4, Canada
  • anow at: School of Environmental Studies, Guelph University, Guelph, N1G 2W1, Canada

Abstract. The emission of SO2 from the Athabasca oil sands region (AOSR) has been shown to impact the surrounding forest area and human exposure. Recent studies using aircraft-based measurements have demonstrated that deposition of SO2 to the forest is at a rate many times higher than model estimates. Here we use the flux/gradient method to estimate SO2 deposition rates at two tower sites in the boreal forest downwind of AOSR SO2 emissions. We use both continuous and passive sampler measurements and compare both techniques. The measurements predict SO2 deposition velocities ranging from 2.1–5.9 cm s-1. There are uncertainties associated with the passive sampler flux/gradient analysis, primarily due to an assumed Schmidt number, a required assumption of independent variables, and potential wind effects. We estimate the total uncertainty as ±2 cm s-1. Accounting for these uncertainties, the measurements are near (or slightly higher than) the previous aircraft-based measurements (1.2–3.2 cm s-1) and significantly higher than model estimates for the same measurement periods (0.1–0.6 cm s-1), suggesting that SO2 has a much shorter lifetime in the atmosphere than is currently predicted by models.

Mark Gordon et al.

Status: open (until 27 Dec 2022)

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Mark Gordon et al.

Mark Gordon et al.


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Short summary
Measurements of the gas sulphur dioxide (SO2) were made in a forest downwind of oil sands mining and production facilities in northern Alberta. These measurements tell us the rate that SO2 is absorbed by the forest. The measured rate is much higher than what is currently used by air-quality models, which is supported by a previous study in this region. This suggest SO2 may have a much shorter lifetime in the atmosphere than is currently predicted by models.