Research Program Area: Atmospheric Processes
Topic Areas: Chemistry & Reactivity
Alkenes and aromatic hydrocarbons are important constituents of ambient air in polluted urban areas, and their atmospheric reactions in the presence of oxides of nitrogen lead to the formation of ozone and other manifestations of photochemical air pollution. During this Contract, the products and mechanisms of the gas-phase OH radical-initiated and O3 reductions of a series of alkenes and of the gas-phase OH radical- and NO3 radical-initiated reactions of four two-ring aromatic hydrocarbons have been investigated. The two-ring aromatic hydrocarbons were studied because it was anticipated that their reaction products would be more amenable to analysis using conventional gas chromatographic techniques than would the corresponding products formed from the monocyclic aromatic hydrocarbons such as benzene. toluene and the xylenes; this was found to be the case. Experiments were carried out in 5,800-7,900 liter volume Teflon or Teflon-Coated chambers and products were analyzed using gas chromatography with flame ionization detection, mass spectrometry, and Fourier transform infrared spectroscopy, by in situ Fourier transform infrared absorption spectroscopy and by direct air sampling, atmospheric pressure ionization tandem mass spectrometry. The results of these experiments have better characterized the reactions in the atmosphere of simple alkenes and of aromatic hydrocarbons, and the reaction mechanisms determined in this study will be used in state-of-the-science detailed chemical mechanisms for the formation of ozone in urban and regional airshed models currently under development.
For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753
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