HR: 16:37h
AN: A14A-03    [Abstracts]
TI: Direct Detection of Cl₂ in Coastal Urban Air
AU: * Finley, B D
EM: bfinley@uci.edu
AF: University of California, Irvine, 1212 Croul Hall, Irvine, CA 92697 United States
AU: Saltzman, E S
EM: esaltzma@uci.edu
AF: University of California, Irvine, 1212 Croul Hall, Irvine, CA 92697 United States
AB: Chlorine radicals react rapidly with a wide range of organic compounds and, if present in sufficient levels, can significantly affect ozone in urban air. Several mechanisms for the generation of Cl in air have been proposed, but there are few direct observations of reactive chlorine species. This study reports measurements of atmospheric chlorine (Cl₂) in coastal urban air utilizing negative ion atmospheric pressure chemical ionization with triple quadrupole mass spectrometry. Measurements were made in Irvine, CA over a 14 day period during July and August, 2005. Fifteen minute average Cl₂ mixing ratios ranged from 5-40 parts per trillion, with a two week geometric mean of 16+/-14 pptv. These levels imply significant (>15 ppb/day) ozone production from the Cl-mediated oxidation of VOC's. A consistent pattern of diurnal variability in Cl₂ was observed, with low nighttime and morning Cl₂ levels, and an increase shortly after local noon reaching a maximum in the early evening. Cl₂ levels gradually returned to lower nighttime values between 9 and 11 PM. This pattern suggests a photochemical production mechanism for Cl₂, and possibly a relationship to the local sea-breeze circulation and the levels of seasalt aerosols.
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 0365 Troposphere: composition and chemistry
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005