No Evidence for S Isotope Fractionation During SO2 Oxidation at a Continental Location

Authors

  • Jacob Kolodziej University of Calgary

Keywords:

Isotopes, Fractionation, Sulfur, Atmosphere

Abstract

Abstract

Introduction

Sulfur isotope fractionation during SO2 oxidation has been shown to occur in laboratory experiments [1] but this has not been observed in whole air samples [2]. Here we replicate the laboratory experiments in a systematic manner using ambient air.

Methods

Particulate matter and SO2 in ambient air were collected at Calgary in the fall of 2012 using high volume samplers and impingers. Atmospheric SO2 and SO­4 concentrations and isotope characteristics were determined.

Results

Variations in concentrations did not reflect changes in δ34S values, suggesting the independence of δ34S from SO2 and SO4 concentrations in the atmosphere. d34SSO2 values for high volume samples was, on average, +13.2‰ ± 0.2‰. SO2 from the impinger method over the same sampling period yielded a δ34SSO2 value of +14.0‰ ± 0.2‰. δ34SSO4 values ranged from +9.9‰ ± 0.5‰ to +15.3‰ ± 0.2‰.

Discussion and Conclusions

δ34SSO2 values from the high volume and impinger samples were similar (+13.2‰ versus +14.0‰, respectively) and shows d34S values from these collection methods are equivalent. Differences between the impinger and high volume sampler d34S values for SO2 and submicron aerosol sulfate were used to gauge sulfur isotope fractionation. Standard deviations for differences were greater than averages (Δd34SSO2 avg.= -0.80‰, s=1.76‰; fine Δd34SSO4 avg.=+0.28‰, s=5.15‰), indicating little to no fractionation. Additionally, δ34SSO2 and δ34SSO4 values were compared to the maximum percent SO2 that may have reacted to form SO4. No pattern was evident so the conclusion is that sulfur isotope fractionation in ambient air is negligible under the conditions sampled.

Literature

1. E. Harris, B. Sinha, P. Hoppe, S. Foley, S. Borrmann, Atmos. Chem. Phys. 12, 2012.

2. A.L. Norman, H.R. Krouse, J. MacLeod, Air Pollution Modeling and Its Application

XVI, 2004.

References

1. H.R. Krouse, in Handbook of Environmental Isotope Geochemistry Vol 2: The Terrestrial Environment, Elsevier Pub. Co., New York, NY, 1980, p.p. 435-471.

2. H.R. Krouse, V.A. Grinenko, in Scope 43: Stable Isotopes, John Wiley & Sons, Ontario, Toronto, 1991, p.p.1-21.

3. W.S. Macdonald, B.F. Bietz, paper presented at the Acidifying Emissions Symposium, Red Deer, AB, April 15-17, 1996.

4. B.J. Finlayson-Pitts, J.N. Pitts Jr., in Atmospheric Chemistry: Fundamentals and Experimental Techniques, Wiley, New York, NY, 1986, p.p. 1098.

5. J.G. Calvert, W.R. Stockwell, in SO2, NO, and NOx Oxidation Mechanisms: Atmospheric Considerations, Butterworth Publishers, Ontario, Toronto, 1984, p.p. 1-62.

6. E. Harris, B. Sinha, P. Hoppe, S. Foley, S. Borrmann, Atmos. Chem. Phys. 12, 2012.

7. A.L. Norman, W. Belzer, L. Barrie, J. Geophys. Res. 109, 2004.

8. A.L. Norman, Atmos. Chem. Phys. Discuss. 9, 2009.

9. A.L. Norman, H.R. Krouse, J. MacLeod, Air Pollution Modeling and Its Application XVI, 2004.

10. A.M. Seguin, A.L. Norman, S.J. Eaton, M.A. Wadleigh, S. Sharma, Atmospheric Environment 44(9), 2010.

11. H.H. Ku, J. Res. Nat. Bur. Stand – C. Engineering and Instrumentation 70(C), 1966.

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Published

2014-07-31

Issue

Vol. 4 (2014)

Section

Articles

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