Tracking the fate of ambient SO2 using sulfur isotopes, oxidant mixing ratios, and hydrocarbon mixtures.
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2019-01-15
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Abstract
Field measurements for SO2 and the formation of sulfate were investigated in the presence of high concentrations of hydrocarbons in the Athabasca oil sands region to help understand sulfate formation pathways and its environmental impacts (Chapter 2). Results indicated the potential importance of SO2 oxidation in TMI-catalyzed pathway in the region during summer which has not been shown before. Oxidation of SO2 with sCIs is shown to be important in the atmosphere and evidence of the importance of this pathway is observed in the Athabasca oil sands region. The sulphur isotope fractionation factor for oxidation of SO2 with sCIs is investigated for the first time in a series of laboratory studies. Measurements of the sulfur isotope fractionation factor for SO2 oxidation with sCIs formed from limonene at 25°C are presented in chapter 3 and α found to be (34)α_sCI=0.992±0.002. Preliminary data for ∆33S and ∆36S during SO2 oxidation with sCIs were 0.061±0.02 ‰ and -0.87±0.02 ‰, respectively. A 1D box model was performed based on the fractionation factor for SO2 oxidation by sCIs. The results suggest that the sCI pathway may contribute 25% of SO2 oxidation in the atmosphere. Since the Athabasca oil sands region is known to have high emissions of hydrocarbons as well as
SO2, investigating the relationship between hydrocarbons and sulfur compounds is of great interest in this region. Sulphate, SO2, and hydrocarbon concentration measurements in the Athabasca oil sands region as part of the JOSM program were used to determine possible sCIs precursors in the region and the role of particles acidity in SOA formation (chapter 4). In addition to monoterpenes, styrene also showed positive correlation with F(s) and can be a precursor to sCIs. Simultaneous data for sulfate and organic compounds in aerosols showed that acid catalyzed enhancement may be an important process for sulfate to ammonium ratio less than 3.
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Amiri, N. (2019). Tracking the fate of ambient SO2 using sulfur isotopes, oxidant mixing ratios, and hydrocarbon mixtures (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.