HR: 1340h
AN: A33D-1566    [Abstracts]
TI: Estimation of Ultraviolet/Visible Absorption by Secondary Organic Aerosols From the Spectra of Condensible Gas Phase Precursors
AU: * Lee-Taylor, J
EM: julial@ucar.edu
AF: National Center for Atmospheric Research, PO Box 3000, Boulder, CO 80307-3000, United States
AU: Madronich, S
EM: sasha@ucar.edu
AF: National Center for Atmospheric Research, PO Box 3000, Boulder, CO 80307-3000, United States
AU: Aumont, B
EM: aumont@lisa.univ-paris12.fr
AF: Laboratoire Interuniversitaire des Systemes Atmospheriques, Universites Paris 12 et Paris 7, Creteil, 94000, France
AU: Camredon, M
EM: camredon@lisa.univ-paris12.fr
AF: Laboratoire Interuniversitaire des Systemes Atmospheriques, Universites Paris 12 et Paris 7, Creteil, 94000, France
AB: The production of atmospheric secondary organic aerosols (SOA) is believed to proceed via the condensation of a large number of partly oxygenated intermediates of the gas-phase degradation of hydrocarbons. While the majority of these intermediates has not yet been detected in the atmosphere, their chemical identities and concentrations are predicted by highly detailed gas-phase chemical schemes, such as the Master Mechanisms. Here, we use the Self-Generating Master Mechanism (SGMM) to represent the gas-phase chemistry of hydrocarbons in the atmosphere of Mexico City, and to partition between gas and particle phases using Raoult's law. The SGMM is nearly explicit, with ca. 105-106 intermediate gas-phase species. Because the SGMM identifies the molecular structure of these intermediate species, it is possible to compute some of their fundamental properties including saturation vapor pressures, solubility coefficients, and spectral absorption. Specifically, we use a chromophore additivity approximation to estimate the absorption spectrum of each gaseous intermediate. When these gases are partitioned to the particles, the spectral information is retained and used to estimate the absorption spectrum of the particles - assuming of course that no additional chemical transformations take place in the particle phase, modifying the absorption. The predicted particle absorption spectrum is compared to measurements obtained in Mexico City.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0317 Chemical kinetic and photochemical properties
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting