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Sulfur Isotopic Fractionation in the Gas-Phase Oxidation of Sulfur Dioxide Initiated by Hydroxyl Radicals

Leung, Fok-Yan and Colussi, A. J. and Hoffmann, M. R. (2001) Sulfur Isotopic Fractionation in the Gas-Phase Oxidation of Sulfur Dioxide Initiated by Hydroxyl Radicals. Journal of Physical Chemistry A, 105 (34). pp. 8073-8076. ISSN 1089-5639. https://resolver.caltech.edu/CaltechAUTHORS:20150623-154757939

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Abstract

The sulfur isotopic signature of atmospheric sulfate aerosol reflects not only the chemical and isotopic composition of its precursors, but also their oxidation pathways. Thus, to trace back the sources of sulfate, a quantitative assessment of sulfur isotopes fractionation in major atmospheric processes is required. In this paper, we evaluate S-isotope fractionation ratios f = (k_(OH+^(34)SO_2))/(k_OH+^(32)SO_2)) for the gas-phase oxidation of SO_2 by OH-radicals, using RRKM transition-state theory. Calculations were constrained by reliable rates for the HO + ^(32)SO_2 + M = HO^(32)SO_2 + M reaction, an ab initio transition-state structure, and actual spectroscopic data for the sulfur isotopomers of the hydroxysulfonyl HOSO_2 radical. By assuming plausible Lennard-Jones parameters for HOSO_2 collisions with N_2 as bath gas, which are consistent with the experimental values of 〈ΔE_(down)〉 ∼ 200 cm^(-1) and a collisional efficiency of β_c ∼ 0.2 in air, we derive f > 1 values at the temperatures and pressures prevalent in the terrestrial atmosphere below 30 km. Present results rationalize the evolution of stratospheric aerosol sulfur isotopic composition after volcanic SO_2 injections above 15 km and the ^(34)S enrichment of tropospheric sulfate aerosol during the summer months.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1021/jp011014+DOIArticle
http://pubs.acs.org/doi/abs/10.1021/jp011014%2BPublisherArticle
ORCID:
AuthorORCID
Colussi, A. J.0000-0002-3400-4101
Hoffmann, M. R.0000-0002-0432-6564
Additional Information:© 2001 American Chemical Society. Received: March 19, 2001; In Final Form: June 11, 2001.
Issue or Number:34
Record Number:CaltechAUTHORS:20150623-154757939
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20150623-154757939
Official Citation:Sulfur Isotopic Fractionation in the Gas-Phase Oxidation of Sulfur Dioxide Initiated by Hydroxyl Radicals Fok-Yan Leung, A. J. Colussi, and M. R. Hoffmann The Journal of Physical Chemistry A 2001 105 (34), 8073-8076 DOI: 10.1021/jp011014+
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:58484
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:28 Jul 2015 20:17
Last Modified:03 Oct 2019 08:36

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