Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 7 2 2007 10.5194/acpd-7-4285-2007 http://www.atmos-chem-phys-discuss.net/7/4285/2007/ http://www.atmos-chem-phys-discuss.net/7/4285/2007/acpd-7-4285-2007.html http://www.atmos-chem-phys-discuss.net/7/4285/2007/acpd-7-4285-2007.pdf 4285 4403 2007-03-29 Halogens and their role in polar boundary-layer ozone depletion W. R. Simpson ffwrs@uaf.edu R. von Glasow K. Riedel P. Anderson P. Ariya J. Bottenheim J. Burrows L. Carpenter U. Frieß M. E. Goodsite D. Heard M. Hutterli H.-W. Jacobi L. Kaleschke B. Neff J. Plane U. Platt A. Richter H. Roscoe R. Sander P. Shepson J. Sodeau A. Steffen T. Wagner E. Wolff Geophysical Institute and Department of Chemistry, University of Alaska Fairbanks, Fairbanks, AK, 99775-6160, USA School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, UK National Institute of Water and Atmospheric Research, Private Bag 14–901, Wellington, New Zealand British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 0ET, UK McGill University, Canada Environment Canada, Toronto, Canada Institute of Environmental Physics, University of Bremen, Bremen, Germany Dept. of Chemistry, University of York , York YO10 5DD, UK Institute for Environmental Physics, University of Heidelberg, Germany University of Southern Denmark, Department of Chemistry and Physics, Campusvej 55 DK5230 Odense M, Denmark School of Chemistry, University of Leeds, Leeds, LS29JT, UK Center for Marine and Atmospheric Research , Institute of Oceanography, University of Hamburg, Bundesstrasse 53, 20146 Hamburg, Germany NOAA/Earth System Research Laboratory, Boulder CO, USA Air Chemistry Department, Max-Planck Institute of Chemistry, PO Box 3060, 55020 Mainz, Germany Purdue Climate Change Research Center, 503 Northwestern Ave. West Lafayette, IN 47907, USA Department of Chemistry, University College Cork, Ireland Alfred Wegner Institute (AWI) for Polar and Marine Research, Bremerhaven, Germany During springtime in the polar regions, unique photochemistry converts inert halide salts 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. 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