Das Projekt "Laboruntersuchungen zum Mechanismus des Abbaus biogener fluechtiger organischer Verbindungen in der Troposhaere: Isopren und DMS" wird vom Umweltbundesamt gefördert und von Max-Planck-Institut für Chemie (Otto-Hahn-Institut) durchgeführt. The project deals with the study of the (photo) degradation products of isoprene and DMS in their reactions with OH- and NO3-radicals, and with O3 (only isoprene). These studies will be performed in the absence of NOX (NO and NO2) or with various concentrations of NOX, in order to identify the major intermediate species which are generated in the different reaction systems. Especially the role played by the various peroxy radicals (RO2) will be examined, in order to establish their chemical fate under tropospheric conditions. In the case of isoprene, the yields of the products will be determined: carbonyl compounds, nitrates, peroxynitrates, organic hydroperoxides, organic acids, etc. In the case of DMS, the yields of the important products, SO2, methylsulphonic acid, dimethylsulphoxide, sulfate, aerosol (CCN) will be investigated. In addition, separate kinetic studies will be carried out on specific radicals involved in the (photo) degradation mechanism of isoprene and DMS, or on radicals possessing similar functional and/or structural groups: eg the kinetics and product distribution of the reactions RO2 + RO2, RO2 + HO2, RO2 + NO3; study of the reactivity of CH3, S, CH3SO and CH3SO2 radicals with O2, O3 and NO2. Finally, the development of a chemical box-model to describe the atmospheric transformation of isoprene and DMS will be part of this project with use of data obtained in both laboratory and field measurements. Since isoprene is used as representative VOC is modelling studies of the photochemistry occurring in the continental boundary layer, a prediction of the resulting ozone and other photo-oxidants is needed. The model involving DMS oxidation is required to assess the sulphur budget and its role in aerosol formation. The work will be performed by nine European research groups, which will deploy a variety of complementary kinetic, spectroscopic and chromatographic techniques.