HR: 0800h
AN: A21C-0871    [Abstracts]
TI: Evidence for Local Heterogeneous Destruction of Boundary Layer Ozone based on Antarctic Field Observations
AU: * Kalnajs, L E
EM: lars.kalnajs@colorado.edu
AF: Laboratory for Atmospheric and Space Physics, University of Colorado, 1234 Innovation Drive, Boulder, CO 80303 United States
AU: Avallone, L M
EM: linnea.avallone@lasp.colorado.edu
AF: Laboratory for Atmospheric and Space Physics, University of Colorado, 1234 Innovation Drive, Boulder, CO 80303 United States
AU: Davis, S M
EM: seand@colorado.edu
AF: Laboratory for Atmospheric and Space Physics, University of Colorado, 1234 Innovation Drive, Boulder, CO 80303 United States
AB: Boundary layer ozone depletion events have been observed in the Antarctic spring for several decades; however, the exact mechanism for the destruction is not fully understood. Previous studies have suggested that these depletion events are the product of large-scale transport of ozone-poor air from over the southern oceans. Research carried out in the 2004 and 2005 spring field seasons in Antarctica suggests that in situ destruction of ozone through heterogeneous chemistry on the snow pack may in fact be a significant contributor to these ozone depletion events. The catalysts for surface-level ozone destruction are reactive halogens - mainly bromine - that are theorized to derive from sea salt, whether by air interacting with frost flowers on sea ice and directly from the open ocean. Ozone flux experiments conducted during the 2004 Antarctic field season strongly suggest that the surface of the Antarctic snow pack and the adjacent surface boundary layer are sites for the bromine-catalyzed destruction. However the specific chemistry responsible for these ozone depletion events is unknown. Two different pathways for ozone destruction are proposed. Ozone may be depleted directly by the snow pack itself through surface uptake by the snow and aqueous or ice-phase bromine-catalyzed destruction. Alternatively, the snow surface may provide a site for heterogeneous recycling of reactive gas-phase bromine from reservoir species, which in turn catalyze ozone destruction in snow pack interstitial air and in the surface boundary layer. Results from Antarctic field experiments show strong surface depletion events occurring during periods of low surface winds and high boundary layer stability. Analysis of anions in snow sampled from the surface layer over a similar time period shows significant variability in bromide concentrations, suggesting a coupling between boundary layer atmospheric chemistry and aqueous snow chemistry. Data from the current Antarctic field season, as well as theoretical investigation of the chemical kinetics of these two reaction paths, may further clarify the role each plays in boundary layer ozone depletion events.
DE: 0322 Constituent sources and sinks
DE: 0365 Troposphere: composition and chemistry
DE: 0368 Troposphere: constituent transport and chemistry
DE: 9310 Antarctica (4207)
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005