HR: 0800h
AN: A41C-01    [Abstracts]
TI: Efficient SOA Formation from Heterogeneous Oxidation of Organic Surfaces by OH Radicals
AU: * Wilson, K R
EM: krwilson@lbl.gov
AF: Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, United States
AU: Smith, J D
EM: jdsmith@lbl.gov
AF: Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, United States
AU: Ahmed, M
EM: mahmed@lbl.gov
AF: Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, United States
AU: Leone, S R
EM: srl@berkeley.edu
AF: Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, United States
AU: Leone, S R
EM: srl@berkeley.edu
AF: University of California, Berkeley, Departments of Chemistry and Physics 209 Gilman Hall Department of Chemistry, Berkeley, CA 94720, United States
AB: Currently, there is much interest in the formation rates and mechanisms of secondary organic aerosols (SOA) from ozone reactions with both biogenic and anthropogenic precursors. However, with the exception of isoprene (1), little work has been done to understand SOA formation from OH radical reactions with other volatile organic compounds. Using a coated flow tube reactor, rapid secondary organic aerosol (SOA) formation is observed when an organic film (such as stearic acid) is exposed to OH radicals. In addition to films, we have also observed that OH oxidation of submicron organic particles also leads to similar SOA formation. These results suggest an entirely new, and very efficient, formation mechanism of SOA via OH radical oxidation of organic surfaces. Analysis of these SOA particles, via VUV photoionization mass spectrometry, suggests that these particles are chemically complex and perhaps oligomeric in nature. We suggest a potential mechanism for this process in which gas phase products, such as semi-volatile aldehydes and carboxylic acids, evolve from the oxidation of the organic films. Subsequent reactions of these volatile products with OH in the gas phase results in efficient SOA formation. This mechanism is supported by the observation that OH radical reactions with gas phase hexanal and nonanal leads to strong SOA formation. These results provide a direct link between volatile organic compounds produced by particle oxidation and SOA formation. References 1. M. Claeys et al., Science 303, 1173 (2004).
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0317 Chemical kinetic and photochemical properties
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2007 Joint Assembly