HR: 15:30h
AN: A33C-06    [Abstracts]
TI: Direct Observation of Extremely Rapid Oligomer Formation Via OH Radical Initiated Oxidation of Organic Aerosols
AU: * Smith, J D
EM: jdsmith@lbl.gov
AF: Chemical Sciences Division, Lawrence Berkeley National Lab, 1 Cyclotrom Rd. MS 6R2100, Berkeley, CA 94607, United States
AU: Goaguen, E
EM: EFGloaguen@lbl.gov
AF: Chemical Sciences Division, Lawrence Berkeley National Lab, 1 Cyclotrom Rd. MS 6R2100, Berkeley, CA 94607, United States
AU: Ahmed, M
EM: mahmed@lbl.gov
AF: Chemical Sciences Division, Lawrence Berkeley National Lab, 1 Cyclotrom Rd. MS 6R2100, Berkeley, CA 94607, United States
AU: Leone, S R
EM: srl@berkeley.edu
AF: Chemical Sciences Division, Lawrence Berkeley National Lab, 1 Cyclotrom Rd. MS 6R2100, Berkeley, CA 94607, United States
AU: Leone, S R
EM: srl@berkeley.edu
AF: Depatment of Chemistry, University of California, Berkeley, Berkeley, CA 94607, United States
AU: Wilson, K R
EM: krwilson@lbl.gov
AF: Chemical Sciences Division, Lawrence Berkeley National Lab, 1 Cyclotrom Rd. MS 6R2100, Berkeley, CA 94607, United States
AB: Ambient aerosols are known to play a significant role in a variety of atmospheric processes such as direct and indirect effects on radiative forcing. Chemical composition can be an important factor in determining the magnitude of these effects (optical density, hygroscopicity, etc.) (1). However, a major fraction(80 - 90%) of organic aerosols can not be resolved on a molecular level. Recent identification of high mass oligomeric species as a major component in laboratory and ambient organic aerosols has received much attention due to the possibility that these species may account for much of the unknown organic mass in ambient aerosols (2, 3). Although, a few mechanisms have been proposed, the origin and formation processes of these compounds remain largely unknown. Here we provide strong evidence for a previously unidentified mechanism of extremely rapid oligomer formation, via OH radical initiated oxidation of organic aerosols. This process appears capable of converting a sizable fraction of an organic particle to higher mass oligomers within only a few hours of exposure to OH radicals at typical atmospheric concentrations. Furthermore, we have found that rapid volatilization, followed by oligomerization, is also important for specific reaction systems, and can lead to the loss of a large fraction (> 60%) of a particle within 15 minutes of exposure to atmospheric OH. We propose that such a rapid processing (oligomerization and volatilization) is possible due to a radical chain reaction which quickly propagates throughout the entire particle and is only initiated by the surface OH reaction. References 1. J. H. Seinfeld, S. N. Pandis, Atmospheric Chemistry and Physics (Wiley, New York, 1998). 2. M. Kalberer et al., Science 303, 1659 (2004). 3. V. Samburova et al., J Geophys Res-Atmos 110, D23210 (2005).
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 3311 Clouds and aerosols
SC: Atmospheric Sciences [A]
MN: 2007 Joint Assembly