Ozone and secondary organic aerosol formation from organic precursors
A technique was developed to determine the amount of ozone and other secondary pollutants generated by individual organic components of atmospheric VOC/NO[subscript x] mixtures. This technique was used to investigate the chemical interactions associated with incremental reactivity calculations. It w...
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| Format: | Others |
| Language: | en |
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1997
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| Online Access: | https://thesis.library.caltech.edu/96/1/Bowman_fm_1997.pdf Bowman, Frank Morales (1997) Ozone and secondary organic aerosol formation from organic precursors. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/y634-fw03. https://resolver.caltech.edu/CaltechETD:etd-01092008-152853 <https://resolver.caltech.edu/CaltechETD:etd-01092008-152853> |
| Summary: | A technique was developed to determine the amount of ozone and other secondary pollutants generated by individual organic components of atmospheric VOC/NO[subscript x] mixtures. This technique was used to investigate the chemical interactions associated with incremental reactivity calculations. It was shown that the incremental reactivity of an individual organic species is a result of changes in the ozone generated by each of the organics present. Incremental reactivities, therefore, are dependent on the nature of the VOC/NO[subscript x] mixture. Aldehydes, alkenes and reactive aromatics were found to have the highest incremental reactivities due to their behavior as radical sources, thereby increasing the rate of reaction of all available organics. Ozone and secondary aerosol formation within the South Coast Air Basin of California during the Southern California Air Quality Study (SCAQS) air pollution episode of August 27-28, 1987 were also analyzed and again the same species were shown to be the most productive compounds in the organic mixture. Less productive compounds, such as CO and alkanes, were also found to be major contributors to ozone concentrations due to their relative abundance. Eight reformulated fuel components were investigated to determine their ozone-forming potential. Most of the fuel oxygenates were found to have relatively low incremental reactivities due to their slow reaction rates and to the formation of relatively unreactive formate and acetate products.
Secondary organic aerosol formation was studied in the Caltech outdoor smog chamber and a model was developed to describe the gas-particle absorptive partitioning of semi-volatile organics. Particle deposition, nucleation and vapor transport to aerosol particles, chamber walls and deposited particles are accounted for by the model. Simulations of a pair of m-xylene/NOX experiments were performed to investigate the nature of aerosol growth. Characteristic transport times indicate that gas-particle equilibrium will typically be established quite rapidly. Additional delays in aerosol formation were shown to result when the condensing semi-volatile products are second-generation, rather than first-generation, products of a parent hydrocarbon. Within a smog chamber, partitioning to chamber walls and deposited particles are shown to be negligible due to unfavorable equilibrium and transport conditions.
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