HR: 0800h
AN: A51C-0590    [Abstracts]
TI: Iodide Catalyzes Bromide Oxidation by Ozone
AU: Vecitis, C D
AF: California Institute of Technology, 1200 E. California Blvd. 138-78 Caltech, Pasadena, CA 91125, United States
AU: * Paulot, F
EM: paulot@caltech.edu
AF: California Institute of Technology, 1200 E. California Blvd. 138-78 Caltech, Pasadena, CA 91125, United States
AU: Colussi, A J
EM: ajcoluss@caltech.edu
AF: California Institute of Technology, 1200 E. California Blvd. 138-78 Caltech, Pasadena, CA 91125, United States
AU: Hoffmann, M R
EM: mrh@caltech.edu
AF: California Institute of Technology, 1200 E. California Blvd. 138-78 Caltech, Pasadena, CA 91125, United States
AB: Ozone depletion events (ODE) occurring in the lower troposphere during early spring involve unexpectedly high levels of gaseous bromine arising from the oxidation of sea salt bromide int he dark polar winter. It has been reported that sea salt is more reactive than pure bromide toward ozone. This fact implies that minor, still unidentified components of natural sea salt catalyze bromide oxidation. We investigate bromine production from aqueous solution microdroplets exposed to gaseous ozone by means of negative ion electrospray mass spectrometry (ESMS). Aqueous bromide and iodide solutions are nebulized in the presence of gaseous ozone, and gaseous products sampled and analyzed by online ESMS after being scavenged in situ by aqueous iodide microdroplets. Bromine formation is confirmed by the appearance and evolution of bromide, iododibromide ion, tribromide ion, and diiodobromide ion signals. We find that bromine gas production is significantly enhanced in mixed iodide and bromide aerosols over bromide solutions. We propose a mechanism for iodide catalysis of bromide by ozone and discuss its implications of ODE's in the Arctic.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0365 Troposphere: composition and chemistry
DE: 0368 Troposphere: constituent transport and chemistry
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting