Investigations of isoprene oxidation multiphase chemistry - Part II

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Oxidation reactions of isoprene, which constitutes the biggest source for NMHC organic carbon in the troposphere, are relevant for atmospheric processes such as ozone production and formation of organic mass. Therefore, isoprene chemistry was intensively studied in the last years. Most of the existing studies are focused on the gas phase and heterogeneous reactions. In contrast to this multiphase chemical processes during the isoprene oxidation have been mostly neglected, except for smaller C2 and C3 products such as glyoxal, methylglyoxal, pyruvic acid and hydroxyacetone. The description of the tropospheric multiphase chemical conversion even of for these compounds is still based on many assumptions and contains large uncertainties. The project proposed here aims to improve and extend the current knowledge on the isoprene oxidation mechanism by considering multiphase chemical processes already from the first product generation on. In order to study these multiphase chemical processes, laboratory and modelling studies will be applied. The improved and extended isoprene oxidation mechanism will be used to evaluate the role and effects of multiphase chemistry during the isoprene degradation processes. To obtain the necessary experimental data for the mechanism development, laboratory studies on the kinetics and in particular on the product formation of early isoprene oxidation products will be carried out and a chemical mechanism module will be developed. Chamber experiments will be performed to verify the results from the laboratory and modelling studies. Within this project, the aqueous phase oxidation reactions of methacrolein, methyl vinyl ketone, methacrylic acid and acrylic acid with OH, NO3 and ozone will be systematically investigated with regard to both their kinetics and mechanisms.