Atmos. Chem. Phys. Discuss., 12, 27693-27736, 2012
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Oxidation of SO2 by stabilized Criegee Intermediate (sCI) radicals as a crucial source for atmospheric sulphuric acid concentrations
M. Boy1, D. Mogensen1,2, S. Smolander1, L. Zhou1, T. Nieminen1, P. Paasonen1,7, C. Plass-Dülmer3, M. Sipilä1, T. Petäjä1, L. Mauldin1,4,5, H. Berresheim6, and M. Kulmala1
1Department of Physics, P.O. Box 48, University of Helsinki, 00014, Finland
2Helsinki University Centre for Environment, P.O. Box 27, University of Helsinki, 00014, Finland
3Hohenpeissenberg Meteorological Observatory, German Weather Service, Hohenpeissenberg, Germany
4Department of Atmospheric and Oceanic Sciences, University of Colorado at Boulder, P.O. Box 311, Boulder, Colorado 80309-0311, USA
5Institute for Arctic and Alpine Research, University of Colorado at Boulder, P.O. Box 450, Boulder, Colorado 80309-0450, USA
6Center for Climate and Air Pollution Studies, School of Physics, National University of Ireland Galway, Ireland
7International Institute for Applied Systems Analysis (IIASA), Schlossplatz 1, 2361 Laxenburg, Austria

Abstract. The effect of increased reaction rates of stabilised Criegee Intermediates (sCI) with SO2 to produce sulphuric acid is investigated using data from two different locations, SMEAR II, Hyytiälä, Finland and Hohenpeissenberg, Germany. Results from MALTE, a zero dimensional model, show that using previous values for the rate coefficients of sCI + SO2, the model underestimates gas phase H2SO4 by up to a factor of two when compared to measurements. Using the rate coefficients recently calculated by Mauldin et al. (2012) increases sulphuric acid by 30–40%. Increasing the rate coefficient for formaldehyde oxide (CH2OO) with SO2 by a factor of ten further increases the H2SO4 yield by 16%. Taken together, these increases lead to the conclusion that, depending on their concentrations, the reaction of stabilized Criegee intermediates with SO2 could contribute as much as 50% to atmospheric sulphuric acid gas phase concentrations at ground level. Using the SMEAR II data, results from SOSA, a one-dimensional model, show that contribution from sCI reactions to sulphuric acid production is most important in the canopy where the concentration of organic compounds are the highest, but can have significant effects on sulphuric acid concentrations up to 100 m. The recent findings that the reaction of sCI + SO2 is much faster than previously thought together with these results show that the inclusion of this new oxidation mechanism is crucial in regional, as well as, global models.

Citation: Boy, M., Mogensen, D., Smolander, S., Zhou, L., Nieminen, T., Paasonen, P., Plass-Dülmer, C., Sipilä, M., Petäjä, T., Mauldin, L., Berresheim, H., and Kulmala, M.: Oxidation of SO2 by stabilized Criegee Intermediate (sCI) radicals as a crucial source for atmospheric sulphuric acid concentrations, Atmos. Chem. Phys. Discuss., 12, 27693-27736, doi:10.5194/acpd-12-27693-2012, 2012.
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