HR: 0800h
AN: A51B-0038    [Abstracts]
TI: Studies of the Composition of Atmospheric Secondary Organic Aerosol Formed From the Photooxidation of Isoprene
AU: * Hildebrandt, L
EM: Lea@its.caltech.edu
AF: California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91125 United States
AU: Surratt, J D
EM: surratt@its.caltech.edu
AF: California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91125 United States
AU: Kroll, J H
EM: kroll@its.caltech.edu
AF: California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91125 United States
AU: Ng, N L
EM: ng@caltech.edu
AF: California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91125 United States
AU: Flagan, R C
EM: flagan@caltech.edu
AF: California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91125 United States
AU: Seinfeld, J H
EM: seinfeld@caltech.edu
AF: California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91125 United States
AB: Oxidation of isoprene (2-methyl-1,3-butadiene) may contribute substantially to the formation of secondary organic aerosol (SOA) on regional as well as global scales. Knowledge of the chemical composition of the aerosol formed from isoprene photooxidation may elucidate the chemistry of isoprene SOA formation, which at present is poorly understood. We analyze the composition of isoprene SOA formed from the irradiation of isoprene/H2O2/air mixtures in a smog chamber with and without the addition of NOx and/or precursor seed. For quantitative analysis of the SOA products, we use liquid chromatography/mass spectrometry in both electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) modes. We use a matrix assisted laser desorption ionization- time of flight mass spectrometer (MALDI-TOFMS), an electrospray ionization- ion trap mass spectrometer (ESI-ITMS), as well as an accurate mass spectrometer with an ESI ionization source to assist in the qualitative identification of the SOA product species. We find that the photooxidation of isoprene produces oligomeric species of molecular weight up to over 500 Daltons. High NOx experiments in general form higher molecular weight species than those experiments in which no NOx was added to the chamber. Furthermore, the product distribution of SOA formed in high NOx experiments is in general more oligomeric in nature, and it features an oligomer with oligomeric unit of 102 Daltons, likely methyl butene diol formed from isoprene photooxidation.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0365 Troposphere: composition and chemistry
DE: 0394 Instruments and techniques
DE: 0428 Carbon cycling (4806)
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005