HR: 08:37h
AN: A11C-03    [Abstracts]
TI: Measurements of Near Surface Concentration Profiles to Study Bromine Surface Enrichment and Nitric Acid Uptake of NaCl-NaBr Single Crystals
AU: * Hess, M
EM: Maurus.Hess@env.ethz.ch
AF: Swiss Federal Institute of Technology Zurich, Institute for Atmospheric and Climate Science (IACETH), Universit„tsstrasse 16, ETH Zentrum, CHN, Zurich, CH-8092 Switzerland
AU: Krieger, U K
EM: Ulirich.Krieger@env.ethz.ch
AF: Swiss Federal Institute of Technology Zurich, Institute for Atmospheric and Climate Science (IACETH), Universit„tsstrasse 16, ETH Zentrum, CHN, Zurich, CH-8092 Switzerland
AU: Marcolli, C
EM: Claudia.Marcolli@env.ethz.ch
AF: Swiss Federal Institute of Technology Zurich, Institute for Atmospheric and Climate Science (IACETH), Universit„tsstrasse 16, ETH Zentrum, CHN, Zurich, CH-8092 Switzerland
AU: Huthwelker, T
EM: thomas.huthwelker@psi.ch
AF: Paul Scherrer Institute (PSI), Laboratory for Radiochemistry and Enviromental Chemistry, Paul Scherrer Institute OFLB 106, Villigen, AG CH-5232 Switzerland
AU: Ammann, M
EM: markus.ammann@psi.ch
AF: Paul Scherrer Institute (PSI), Laboratory for Radiochemistry and Enviromental Chemistry, Paul Scherrer Institute OFLB 106, Villigen, AG CH-5232 Switzerland
AU: Peter, T
EM: Thomas.Peter@env.ethz.ch
AF: Swiss Federal Institute of Technology Zurich, Institute for Atmospheric and Climate Science (IACETH), Universit„tsstrasse 16, ETH Zentrum, CHN, Zurich, CH-8092 Switzerland
AU: Lanford, W A
EM: lanford@albany.edu
AF: University at Albany, State University of New York, Physics Department, 1400 Washington Avenue, Albany, NY 12222 United States
AB: Halogens released from sea salt aerosols and sea water ice are known to be important for atmospheric chemistry because of their high reactivity towards many other species in the atmosphere. Rutherford Backscattering Spectrometry (RBS) was used to measure oxygen, chlorine and bromine concentrations versus depth in bromine doped NaCl crystals in the near surface region. This allows to quantify bromine surface enrichment, chlorine surface depletion and the formation of nitrate due to chemical reaction with nitric acid. It furthermore enables to characterize these processes and their kinetics such as their dependence on the relative humidity. Bromine surface enrichment and nitric acid uptake was measured over a wide range of exposure times at relative humidities of 20 %, 50 % and 65 %. Significant enrichment of bromine occurs only at relative humidities of 50 % or 65 % and can be as high as a factor of 20 above bulk concentration in a surface layer thinner than 80 nm. The enrichment in this layer is generated within a few days and remains constant afterwards. We conclude that bromine enrichment observed in our experiments is mediated by the formation of a liquid layer and can be described by partitioning of bromine between crystalline solid and liquid surface layer. In contrast, nitrate migrates into a depth of several microns at high relative humidities. The concentration increases continuously over time periods of at least weeks. At a low relative humidity of 20 %, the uptake of nitric acid is limited to the surface.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0335 Ion chemistry of the atmosphere (2419, 2427)
DE: 0365 Troposphere: composition and chemistry
DE: 0399 General or miscellaneous
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005