Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 7 16 2007 10.5194/acp-7-4329-2007 http://www.atmos-chem-phys.net/7/4329/2007/ http://www.atmos-chem-phys.net/7/4329/2007/acp-7-4329-2007.html http://www.atmos-chem-phys.net/7/4329/2007/acp-7-4329-2007.pdf 4329 4373 2007-08-22 An overview of snow photochemistry: evidence, mechanisms and impacts A. M. Grannas amanda.grannas@villanova.edu A. E. Jones J. Dibb M. Ammann C. Anastasio H. J. Beine M. Bergin J. Bottenheim C. S. Boxe G. Carver G. Chen J. H. Crawford F. Dominé M. M. Frey M. I. Guzmán D. E. Heard D. Helmig M. R. Hoffmann R. E. Honrath L. G. Huey M. Hutterli H. W. Jacobi P. Klán B. Lefer J. McConnell J. Plane R. Sander J. Savarino P. B. Shepson W. R. Simpson J. R. Sodeau R. von Glasow R. Weller E. W. Wolff T. Zhu Department of Chemistry, Villanova University, Villanova, PA 19085, USA British Antarctic Survey, Natural Environment Research Council, Cambridge, CB3 0ET, UK Institute for the Study of Earth, Oceans and Space, University of New Hampshire, Durham, NH 03824, USA Laboratory for Radio- and Environmental Chemistry, Paul Scherrer Institute, 5232 Villigen, Switzerland Department of Land, Air {&} Water Resources, University of California at Davis, Davis, CA 95616, USA Consiglio Nazionale delle Ricerche – Istituto Inquinamento Atmosferico (C.N.R. – I.I.A); Via Salaria Km 29,3; 00016 Monterotondo Scalo, Roma, Italy School of Civil and Environmental Engineering and School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA Air Quality Research Branch, Environment Canada, Downsview, Ontario, Canada W. M. Keck Laboratories, California Institute of Technology, Pasadena, CA 91125, USA Center for Atmospheric Sciences, Department of Chemistry, Cambridge University, Lensfield Road, Cambridge, UK NASA Langley Research Center, Hampton, VA 23681, USA Laboratoire de Glaciologie et Géophysique de l'Environnement,CNRS/Université Joseph Fourier-Grenoble, St Martin d'Hères Cedex, France School of Engineering, University of California-Merced, Merced, CA 95343, USA Currently at School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, USA School of Chemistry, University of Leeds, Leeds, LS2 9JT, UK Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO 80309, USA Department of Civil and Environmental Engineering, Michigan Technological University, Houghton, MI 49931, USA School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30033, USA Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany Masaryk University, Department of Chemistry, Brno, Czech Republic Department of Earth and Space Science and Engineering, York University, Toronto, Ontario, Canada Air Chemistry Department, Max-Planck Institute of Chemistry, P.O. Box 3060, 55020 Mainz, Germany Dept. of Chemistry and Department of Earth and Atmospheric Sciences, Purdue Univ., West Lafayette, IN 47907, USA Department of Chemistry and Geophysical Institute, University of Alaska Fairbanks, Fairbanks, AK 99775-6160, USA Department of Chemistry, University College Cork, Cork, Ireland Institute of Environmental Physics, University of Heidelberg, Heidelberg, Germany School of Environmental Sciences, University of East Anglia, Norwich, UK College of Environmental Sciences, Peking University, Beijing 100871, China Department of Geosciences, University of Houston, TX 77204, USA It has been shown that sunlit snow and ice plays an important role in processing atmospheric species. Photochemical production of a variety of chemicals has recently been reported to occur in snow/ice and the release of these photochemically generated species may significantly impact the chemistry of the overlying atmosphere. Nitrogen oxide and oxidant precursor fluxes have been measured in a number of snow covered environments, where in some cases the emissions significantly impact the overlying boundary layer. For example, photochemical ozone production (such as that occurring in polluted mid-latitudes) of 3–4 ppbv/day has been observed at South Pole, due to high OH and NO levels present in a relatively shallow boundary layer. Field and laboratory experiments have determined that the origin of the observed NOx flux is the photochemistry of nitrate within the snowpack, however some details of the mechanism have not yet been elucidated. A variety of low molecular weight organic compounds have been shown to be emitted from sunlit snowpacks, the source of which has been proposed to be either direct or indirect photo-oxidation of natural organic materials present in the snow. Although myriad studies have observed active processing of species within irradiated snowpacks, the fundamental chemistry occurring remains poorly understood. Here we consider the nature of snow at a fundamental, physical level; photochemical processes within snow and the caveats needed for comparison to atmospheric photochemistry; our current understanding of nitrogen, oxidant, halogen and organic photochemistry within snow; the current limitations faced by the field and implications for the future. Abbatt, J. P. D.: Interactions of atmospheric trace gases with ice surfaces: Adsorption and reaction, Chem. Rev., 103, 4783–4800, 2003. Adams, J .W., Holmes, N. S., and Crowley, J. N.: Uptake and reaction of HOBr on frozen and dry salt surfaces, Atmos. Chem. Phys., 2, 79–91, 2002. Albert, M. R., Grannas, A. M., Bottenheim, J. W., Shepson, P. B., and Perron, F. 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