HR: 12:05h
AN: A41G-07    [PDF]
TI: Acid-catalyzed Heterogeneous Reactions in SOA Formation
AU: * Ng, N
EM: ng@caltech.edu
AF: California Institute of Technology, 2100 E California Blvd, Pasadena, CA 91106 United States
AU: Keywood, M
EM: meltia@cheme.caltech.edu
AF: California Institute of Technology, 2100 E California Blvd, Pasadena, CA 91106 United States
AU: Varutbangkul, V
EM: tomotor@caltech.edu
AF: California Institute of Technology, 2100 E California Blvd, Pasadena, CA 91106 United States
AU: Gao, S
EM: sgao@caltech.edu
AF: California Institute of Technology, 2100 E California Blvd, Pasadena, CA 91106 United States
AU: Loewer, E
EM: ethelmae@caltech.edu
AF: California Institute of Technology, 2100 E California Blvd, Pasadena, CA 91106 United States
AU: Surratt, J
EM: surratt@caltech.edu
AF: California Institute of Technology, 2100 E California Blvd, Pasadena, CA 91106 United States
AU: Richard, F C
EM: flagan@cheme.caltech.edu
AF: California Institute of Technology, 2100 E California Blvd, Pasadena, CA 91106 United States
AU: John, S H
EM: seinfeld@caltech.edu
AF: California Institute of Technology, 2100 E California Blvd, Pasadena, CA 91106 United States
AB: The importance of heterogeneous reactions in secondary organic aerosol (SOA) formation has recently excited a great deal of interest in the aerosol community. Jang and Kamens (2001) showed enhanced aerosol yield from aldehydes, which can be produced by atmospheric photochemical reactions, in the presence of acidic seed. They suggest that the carbonyl functional groups of the aldehydes further react in the aerosol phase via hydration, polymerization, and hemiacetal/acetal formation with alcohols at an accelerated rate in the presence of acid. Jang et al. (2003) demonstrated similar results using a flow reactor and Czoschke et al. (in press) qualitatively showed increased yields for isoprene and alpha-pinene ozonolysis in the presence of acidic seed. While these findings are intriguing and important, the conditions under which the experiments were carried out were atmospherically unrealistic. A series of SOA formation experiments have been carried out in the Caltech Indoor Chamber Facility, which is comprised of dual 28 m$^{3}$ FEP Teflon chambers, with the flexibility to carry out both dark ozonolysis and photochemical OH oxidation reactions. Cycloheptene and alpha-pinene were oxidized in the presence of neutral seed under dry ($<$10% RH) and humid (50% RH) conditions and in the presence of acidic seed under humid (50% RH) conditions. The SOA yields for these experiments will be presented, and the extent of the influence of acid-catalyzed reactions on SOA yield will be discussed. Reference List 1. Cocker, D. R. III. and R. C. Flagan and J. H. Seinfeld, State-of-the-art chamber facility for studying atmospheric aerosol chemistry, Environmental Science and Technology, 35, 2594-2601, 2001. 2. Czoschke, N. M., M. Jang, and R. M. Kamens, Effect of acid seed on biogenic sceondary organic aerosol growth, Atmospheric Environment, In press. 3. Jang, M., S. Lee, and R. M. Kamens, Organic aerosol growth by acid-catalyzed heterogeneous reactions of octanal in a flow reactor, Atmospheric Environment, 37, 2125-2138, 2003. 4. Jang, M. S. and R. M Kamens, Atmospheric secondary aerosol formation by heterogeneous reactions of aldehydes in the presence of a sulfuric acid aerosol catalyst. Environmental Science and Technology, 35, 4758-4766,2001.
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0345 Pollution--urban and regional (0305)
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting