HR: 1340h
AN: A53B-1144    [Abstracts]
TI: Coupled HOx, NOx and Halogen chemistry in the Antarctic Boundary Layer
AU: * Bloss, W J
EM: w.j.bloss@bham.ac.uk
AF: University of Birmingham, School of Geography, Earth and Environmental Sciences, Birmingham, B15 2TT, United Kingdom
AU: Lee, J D
EM: jdl3@york.ac.uk
AF: University of York, Department of Chemistry, York, YO10 5DD, United Kingdom
AU: Heard, D E
EM: d.e.heard@leeds.ac.uk
AF: University of Leeds, School of Chemistry, Leeds, LS2 9JT, United Kingdom
AU: Saiz-Lopez, A
EM: a.e.saiz-lopez@jpl.nasa.gov
AF: Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, United States
AU: Plane, J M
EM: j.plane@leeds.ac.uk
AF: University of Leeds, School of Chemistry, Leeds, LS2 9JT, United Kingdom
AU: Bauguitte, S J
EM: sbau@bas.ac.uk
AF: British Antarctic Survey, Madingley Road, Cambridge, CB3 0ET, United Kingdom
AU: Salmon, R A
EM: rasa@bas.ac.uk
AF: British Antarctic Survey, Madingley Road, Cambridge, CB3 0ET, United Kingdom
AU: Jones, A E
EM: aejo@bas.ac.uk
AF: British Antarctic Survey, Madingley Road, Cambridge, CB3 0ET, United Kingdom
AB: The Chemistry of the Antarctic Boundary Layer and the Interface with Snow (CHABLIS) campaign took place at Halley Base in coastal Antarctica from January 2004 until February 2005. The campaign included a summer intensive focussing upon oxidant chemistry, featuring measurements of OH/HO₂ radicals, total peroxy radicals and the halogen oxides IO and BrO in addition to long-term observations of NOx, VOCs, peroxides, HONO, HCHO and CO, together with radiation and meteorological parameters. Measurements of reactive species, especially HOx (OH and HO₂) obtained during the summer period of the CHABLIS campaign have been analysed using box model simulations. The model, based upon the Master Chemical Mechanism, was constrained to observed meteorological parameters, photolysis rates, and concentrations of long-lived species such as VOCs and O₃. The basic simulations overestimate the observed OH and HO₂ levels and fail to replicate the diurnal NOx cycle. Addition of a strong halogen source, and attendant XONO₂ hydrolysis sink for NOx, improves the model performance, however either additional radical sinks, or changes to the (highly uncertain) iodine oxide – HOx chemistry, are required to achieve good agreement. Overall the model simulations show the coastal Antarctic boundary layer to be an environment in which rapid radical cycling occurs, but driven by the halogen oxides IO and BrO rather than by NOx, and with attendant ozone destruction rather than production. A mechanism for the efficient recycling of halogen species, through the condensed phase, is required to explain the observed concentrations.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0317 Chemical kinetic and photochemical properties
DE: 0365 Troposphere: composition and chemistry
DE: 0799 General or miscellaneous
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting