HR: 0830h
AN: A51F-0744    [PDF]
TI: Secondary Organic Aerosol Formation from the Ozonolysis of Cycloalkenes
AU: * Keywood, M
EM: melita@cheme.caltech.edu
AF: California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91106 United States
AU: Varutbangkul, V
EM: tomtor@caltech.edu
AF: California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91106 United States
AU: Gao, S
EM: sgao@caltech.edu
AF: California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91106 United States
AU: Brechtel, F
EM: fredb@bnl.gov
AF: California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91106 United States
AU: Bahreini, R
EM: broya@caltech.edu
AF: California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91106 United States
AU: Flagan, R C
EM: flagan@cheme.caltech.edu
AF: California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91106 United States
AU: Seinfeld, J H
EM: seinfeld@caltech.edu
AF: California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91106 United States
AB: Secondary organic aerosol (SOA) is ubiquitous in the atmosphere being present in both urban and remote locations and exerting influence on human health, visibility and climate. Despite its importance, our understanding of SOA formation still lacks essential elements, limiting our understanding of the effect of SOA on climate forcing. While there do exist experimental data on SOA yields from both biogenic and anthropogenic precursor compounds, it is difficult to extend these results to predict the aerosol-forming potential of precursor compounds not yet studied. In response to this, a series of chamber experiments were carried out in the Caltech Indoor Chamber Facility, where compounds from the cycloalkene and methyl-substituted cycloalkene families were oxidized by ozone in the dark. The reactions were carried out in dual 28 m$^{3}$ teflon chambers at 20$^{o}$C and relative humidity below 5%, in the presence of ammonium sulfate seed aerosol. Cyclohexane was used as a scavenger to prevent side oxidation reactions with OH radicals, generated during ozonolysis of the cycloalkene. While cycloalkenes may not be important precursors for SOA formation in the ambient atmosphere, the system was chosen for its simplicity relative to atmospherically relevant SOA precursors such as the biogenic monoterpenes and sesquiterpenes. Cycloalkenes may be seen as the simplified structures on which these more complicated compounds are based. The compounds reacted included the cycloalkenes: cyclopentene, cyclohexene, cycloheptene and cyclooctene, the methyl-substituted cycloalkenes: 1-methyl-1-cyclohexene, 3-methyl-1-cyclohexene, 1-methy-1-cycloheptene and1-methyl-1-cylopentene, and other related classes of hydrocarbons: methylene cyclohexane and terpinolene. Data collected include aerosol yield, chemical composition and hygroscopic behaviour. The effect of the precursor hydrocarbon structure on these properties of the SOA will be discussed.
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0345 Pollution--urban and regional (0305)
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting