Aerosol formation from atmospheric hydrocarbon photooxidation
Outdoor smog chamber experiments have been performed to determine the secondary organic aerosol (SOA) formation potential of various C7, C8, and C9 aromatics in sunlight-irradiated hydrocarbon- NO[subscript x] mixtures. Measured aerosol yields from toluene,m-xylene, p -xylene, ethylbenzene, m -ethyl...
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| Format: | Others |
| Language: | en |
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1996
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| Online Access: | https://thesis.library.caltech.edu/5054/1/Forstner_hjl_1996.pdf Forstner, Hali J. L. (1996) Aerosol formation from atmospheric hydrocarbon photooxidation. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/khpq-7188. https://resolver.caltech.edu/CaltechETD:etd-12182007-114559 <https://resolver.caltech.edu/CaltechETD:etd-12182007-114559> |
| Summary: | Outdoor smog chamber experiments have been performed to determine the secondary organic aerosol (SOA) formation potential of various C7, C8, and C9 aromatics in sunlight-irradiated hydrocarbon- NO[subscript x] mixtures. Measured aerosol yields from toluene,m-xylene, p -xylene, ethylbenzene, m -ethyltoluene, p-ethyltoluene, and 1 ,2,4-trimethylbenzene were found to correlate with organic mass concentration according to semi-volatile gas/particle partitioning theory. Aerosol yields of the C9 aromatics were greater than those of the C8 aromatics, with m-ethyltoluene resulting in the greatest yields. Toluene and ethylbenzene demonstrated some aerosol-forming potential, but the other aromatics produced significantly more SOA.
Filter samples were also collected during the experiments to determine the molecular composition of the SOA from these aromatics Gas-phase mechanisms leading to these products have been proposed. Unsaturated anhydrides (2,5-furandione, 3-methyl-2,5-furandione, 3-ethyl-2,5-furandione) are predominant components of aerosol from all the aromatics, an observation that is consistent with gas-phase aromatic mechanisms involving ring-fragmentation. Saturated anhydrides were also detected in significant quantities, which could result from the hydrogenation of furandiones in sunlight in the particle phase. A new organic aerosol extraction procedure utilizing supercritical CO2 extraction is outlined.
Outdoor smog chamber experiments were also performed to characterize aerosol from 1-octene and 1-decene photooxidation. The dominant aerosol species were heptanal, heptanoic acid, and dihydro-5-propyl-2(3H)-furanone from 1-octene, and nonanal, nonanoic acid, and dihydro-5-pentyl-2(3H)-furanone from 1-decene. Gas-phase oxidation mechanisms of 1-octene and 1-decene with OH and O3 account for the aerosol products.
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