Atmos. Chem. Phys., 7, 4375-4418, 2007
www.atmos-chem-phys.net/7/4375/2007/
doi:10.5194/acp-7-4375-2007
© Author(s) 2007. This work is licensed under the
Creative Commons Attribution-NonCommercial-ShareAlike 2.5 License.
Halogens and their role in polar boundary-layer ozone depletion
W. R. Simpson1, R. von Glasow2, K. Riedel3, P. Anderson4, P. Ariya5, J. Bottenheim6, J. Burrows7, L. J. Carpenter8, U. Frieß9, M. E. Goodsite10, D. Heard11, M. Hutterli4, H.-W. Jacobi17, L. Kaleschke12, B. Neff13, J. Plane11, U. Platt9, A. Richter7, H. Roscoe4, R. Sander14, P. Shepson15, J. Sodeau16, A. Steffen6, T. Wagner9,14, and E. Wolff4
1Geophysical Institute and Department of Chemistry, University of Alaska Fairbanks, Fairbanks, AK, 99775-6160, USA
2School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, UK
3National Institute of Water and Atmospheric Research, Private Bag 14–901, Wellington, New Zealand
4British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 0ET, UK
5McGill University, Canada
6Environment Canada, Toronto, Canada
7Institute of Environmental Physics, University of Bremen, Bremen, Germany
8Dept. of Chemistry, University of York , York YO10 5DD, UK
9Institute for Environmental Physics, University of Heidelberg, Germany
10University of Southern Denmark, Department of Chemistry and Physics, Campusvej 55 DK5230 Odense M, Denmark
11School of Chemistry, University of Leeds, Leeds, LS29JT, UK
12Center for Marine and Atmospheric Research , Institute of Oceanography, University of Hamburg, Bundesstrasse 53, 20146 Hamburg, Germany
13NOAA/Earth System Research Laboratory, Boulder CO, USA
14Air Chemistry Department, Max-Planck Institute of Chemistry, PO Box 3060, 55020 Mainz, Germany
15Purdue Climate Change Research Center, 503 Northwestern Ave. West Lafayette, IN 47907, USA
16Department of Chemistry, University College Cork, Ireland
17Alfred Wegner Institute (AWI) for Polar and Marine Research, Bremerhaven, Germany

Abstract. During springtime in the polar regions, unique photochemistry converts inert halide salt ions (e.g. Br) into reactive halogen species (e.g. Br atoms and BrO) that deplete ozone in the boundary layer to near zero levels. Since their discovery in the late 1980s, research on ozone depletion events (ODEs) has made great advances; however many key processes remain poorly understood. In this article we review the history, chemistry, dependence on environmental conditions, and impacts of ODEs. This research has shown the central role of bromine photochemistry, but how salts are transported from the ocean and are oxidized to become reactive halogen species in the air is still not fully understood. Halogens other than bromine (chlorine and iodine) are also activated through incompletely understood mechanisms that are probably coupled to bromine chemistry. The main consequence of halogen activation is chemical destruction of ozone, which removes the primary precursor of atmospheric oxidation, and generation of reactive halogen atoms/oxides that become the primary oxidizing species. The different reactivity of halogens as compared to OH and ozone has broad impacts on atmospheric chemistry, including near complete removal and deposition of mercury, alteration of oxidation fates for organic gases, and export of bromine into the free troposphere. Recent changes in the climate of the Arctic and state of the Arctic sea ice cover are likely to have strong effects on halogen activation and ODEs; however, more research is needed to make meaningful predictions of these changes.

Citation: Simpson, W. R., von Glasow, R., Riedel, K., Anderson, P., Ariya, P., Bottenheim, J., Burrows, J., Carpenter, L. J., Frieß, U., Goodsite, M. E., Heard, D., Hutterli, M., Jacobi, H.-W., Kaleschke, L., Neff, B., Plane, J., Platt, U., Richter, A., Roscoe, H., Sander, R., Shepson, P., Sodeau, J., Steffen, A., Wagner, T., and Wolff, E.: Halogens and their role in polar boundary-layer ozone depletion, Atmos. Chem. Phys., 7, 4375-4418, doi:10.5194/acp-7-4375-2007, 2007.
 
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