HR: 16:22h
AN: A14A-02    [Abstracts]
TI: CHAiOS: Chemistry of Halogens at the Isles of Shoals
AU: * Keene, W C
EM: wck@virginia.edu
AF: Department of Environmental Sciences, University of Virginia, Charlottesville, VA 22904 United States
AU: Stutz, J
EM: jochen@atmos.ucla.edu
AF: Department of Atmospheric and Oceanic Sciences, University of California, Los Angel, CA 900095 United States
AU: Pszenny, A A
EM: alex.pszenny@unh.edu
AF: Institute for the Study of Earth, Oceans and Space, University of New Hampshire, Durham, NH 03824 United States
AU: Russell, L
EM: lmrussell@ucsd.edu
AF: Scripps Institution of Oceanography, University of California, San Diego, CA 92093 United States
AU: von Glasow, R
EM: Roland.von.Glasow@iup.uni-heidelberg.de
AF: Institute for Environmental Physics, University of Heidelberg, Heidelberg, 69120 Germany
AU: Sive, B
EM: bcs@gust.sr.unh.edu
AF: Institute for the Study of Earth, Oceans and Space, University of New Hampshire, Durham, NH 03824 United States
AU: Sive, B
EM: bcs@gust.sr.unh.edu
AF: Institute for Environmental Physics, University of Heidelberg, Heidelberg, 69120 Germany
AU: Varner, R
EM: ruth.varner@unh.edu
AF: Institute for the Study of Earth, Oceans and Space, University of New Hampshire, Durham, NH 03824 United States
AB: During summer 2004, a comprehensive suite of reactive trace gases (including halogen radicals and precursors, O₃, reactive N, soluble acids, NH₃, HCHO, SO₂, hydrocarbons, and halocarbons), the chemical and physical characteristics of size-resolved aerosols, actinic flux, and related physical conditions was measured at Appledore Island, ME as part of the International Consortium for Atmospheric Research on Transport and Transformations (ICARTT). Acid displacement of sea-salt Cl^- primarily by HNO₃ sustained high HCl mixing ratios (often >2000 pptv or >5 * 10¹⁰ cm^-3) during daytime. HCl + OH produced 10⁵ to 10⁶ Cl atoms cm^-3 sec^-1. Cl* (including HOCl and Cl₂) typically ranged from <20 (<5 * 10⁸ cm^-3) to about 100 pptv (3 * 10⁹ cm^-3). Depending on its assumed composition, Cl* photolysis yielded an additional source for Cl ranging from <10⁴ to 10⁷ atoms cm^-3 sec^-1. Maximum steady-state Cl concentrations during daytime (10⁴ to 10⁶ atoms cm^-3) indicated significant contributions to oxidizing capacity. IO, OIO, and I₂ were quantified simultaneously by long-path and MAX DOAS. IO ranged from <1.8 to 7 pptv, was detected only during daytime at wind speeds >2 m sec^-1, and was uncorrelated with tidal height. For the first time, OIO was detected during daytime indicating that photolysis was an unimportant sink. The presence of OIO at high NO_x implies unknown chemical pathways. Calculations with the 1-D photochemical model MISTRA predict longer lifetimes for OIO relative to IO, consistent with observations. I chemistry influenced ozone significantly by direct reaction (e.g., I + O₃ → IO + O₂) and by changing OH/HO₂ and NO/NO₂ ratios. Aerosols in all size fractions were highly enriched in I relative to sea salt (factors of 10² to 10⁵) indicating active multiphase transformations. Numerous aerosol growth events were detected some of which were associated with elevated IO and OIO. However, the lack of consistent correlation with iodine species suggests that I chemistry may not be the dominant nucleation pathway in polluted coastal New England air. Br radical chemistry was relatively unimportant.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0322 Constituent sources and sinks
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 0365 Troposphere: composition and chemistry
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005