Model study of multiphase DMS oxidation with a focus on halogens

von Glasow, R. and Crutzen, P. J. (2004) Model study of multiphase DMS oxidation with a focus on halogens. Atmospheric Chemistry and Physics, 4 (3). pp. 589-608. ISSN 1680-7324

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Abstract

We studied the oxidation of dimethylsulfide (DMS) in the marine boundary layer (MBL) with a one-dimensional numerical model and focused on the influence of halogens. Our model runs show that there is still significant uncertainty about the end products of the DMS addition pathway, which is especially caused by uncertainty in the product yield of the reaction of the intermediate product methyl sulfinic acid (MSIA) with OH. BrO strongly increases the importance of the addition branch in the oxidation of DMS even when present at mixing ratios smaller than 0.5pmol mol-1. The inclusion of halogen chemistry leads to higher DMS oxidation rates and smaller DMS to SO2 conversion efficiencies. The DMS to SO2 conversion efficiency is also drastically reduced under cloudy conditions. In cloud-free model runs between 5 and 15% of the oxidized DMS reacts further to particulate sulfur, in cloudy runs this fraction is almost 100%. Sulfate production by HOClaq and HOBraq is important in cloud droplets even for small Br- deficits and related small gas phase halogen concentrations. In general, more particulate sulfur is formed when halogen chemistry is included. A possible enrichment of HCO3- in fresh sea salt aerosol would increase pH values enough to make the reaction of S(IV)* (=SO2,aq+HSO3-+SO32-) with O3 dominant for sulfate production. It leads to a shift from methyl sulfonic acid (MSA) to non-sea salt sulfate (nss-SO42-) production but increases the total nss-SO42- only somewhat because almost all available sulfur is already oxidized to particulate sulfur in the base scenario. We discuss how realistic this is for the MBL. We found the reaction MSAaq+OH to contribute about 10% to the production of nss-SO42- in clouds. It is unimportant for cloud-free model runs. Overall we find that the presence of halogens leads to processes that decrease the albedo of stratiform clouds in the MBL.

Item Type:	Article
Faculty \ School:	Faculty of Science > School of Environmental Sciences
UEA Research Groups:	Faculty of Science > Research Groups > Volcanoes@UEA (former - to 2018) Faculty of Science > Research Groups > Marine and Atmospheric Sciences (former - to 2017) Faculty of Science > Research Groups > Meteorology, Oceanography and Climate Dynamics (former - to 2017) Faculty of Science > Research Groups > Atmospheric Chemistry (former - to 2018) Faculty of Science > Research Groups > Climate, Ocean and Atmospheric Sciences (former - to 2017) Faculty of Science > Research Groups > Centre for Ocean and Atmospheric Sciences
Depositing User:	Rachel Snow
Date Deposited:	06 Apr 2011 12:19
Last Modified:	14 Sep 2023 15:30
URI:	https://ueaeprints.uea.ac.uk/id/eprint/28216
DOI:	10.5194/acp-4-589-2004

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