HR: 17:00h
AN: A24B-05    [Abstracts]
TI: Solar Polymerization of Atmospheric Aerosol
AU: Colussi, A J
EM: ajcoluss@caltech.edu
AF: Environmental Science and Technology, California Institute of Technology, 1200 E. California Blvd. 138-78, Pasadena, CA 91125 United States
AU: * Guzman, M I
EM: mig@caltech.edu
AF: Environmental Science and Technology, California Institute of Technology, 1200 E. California Blvd. 138-78, Pasadena, CA 91125 United States
AU: Hoffmann, M R
EM: mrh@caltech.edu
AF: Environmental Science and Technology, California Institute of Technology, 1200 E. California Blvd. 138-78, Pasadena, CA 91125 United States
AB: Alpha-oxoacids are ubiquitous constituents of the aqueous fraction of ambient aerosol as products common to the oxidation of most atmospheric organic species. The environmental fate of alpha-oxoacids is in turn determined by the photoreactions of their carbonyl groups under solar (lambda longer than 300 nm) irradiation. We report that, in addition to CO2 extrusion, the photodecomposition of alpha-oxoacids in water leads to hitherto unidentified, colored oligomers. These oligomers are separated by high performance liquid chromatography, and identified as thermolabile polyfunctional oxo-, hydroxy- and carboxylic acid derivatives of aliphatic polyethers by electrospray ionization-negative ion mass spectrometry (ESI-MS) and 13C-NMR. Polymerization is initiated by photoinduced electron transfer between carbonyl groups of adjacent alpha-oxoacid molecules, and most likely propagated by alkoxyl radicals. The degree of polymerization increases with irradiation time until oligomers heavier than about 1 kDa separate as yellow solids. It is found that these oligomers pyrolyze into simpler species under conventional gas chromatographic conditions. Present results require a fundamental revision of current mechanisms of aerosol growth and stabilization, and a critical reappraisal of the analytical techniques used to characterize aerosol.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005