Experimental Studies of the Kinetics of the OH-initiated Oxidation of Biogenic Compounds

The chemical mechanism of the oxidation of biogenic compounds such as methyl butenol and α- and β-pinene are a subject of considerable interest in atmospheric chemistry. These compounds are emitted into the atmosphere by various types of vegetation, and can contribute significantly to the production of ozone and secondary aerosol production in the troposphere because of their high reactivity. The accuracy of urban and regional air quality models thus depends on a complete understanding of their oxidation mechanisms under a variety of conditions. Results of laboratory investigations of the mechanisms of the OH-initiated oxidation of methyl butenol and α- and β-pinene in the presence of NO using discharge-flow techniques will be presented. The measured OH radical concentration profiles in the presence of NO were compared to simulations based on various proposed oxidation mechanisms in order to determine the mechanism that best describes the observed radical propagation. These experiments provide a measurement of the relative efficiency of radical propagation by each biogenic compound in the production of tropospheric ozone.