Das Projekt "Laboruntersuchungen der fuer die Troposphaerenchemie bedeutenden Peroxyradikalreaktionen" wird vom Umweltbundesamt gefördert und von Max-Planck-Institut für Chemie (Otto-Hahn-Institut) durchgeführt. Objective: The objective of this research is to provide a better description of the chemical processes involved in production and loss of ozone in the troposphere. This will be achieved through the provision of kinetics and mechanistic data for several reactions of organic peroxy radicals involved in tropospheric chemistry and assessment of the results using numerical simulation models of atmospheric chemistry. General information: attention will be directed to: - simple organic peroxy radicals derived from volatile organic compounds of both natural and man-made origin which are believed to influence ozone in the troposphere. - the chemical reactions involving these radicals at typical boundary layer NOx concentrations and in the 'low NOx' regime where peroxy radicals may remove ozone. - provision of rate data for a range of pressures and temperatures appropriate for the atmosphere from ground level to the tropopause and mechanistic data necessary for formulation of the atmospheric chemistry. - the work involves complementary studies in 4 laboratories in Europe with the necessary resources and expertise for studies of kinetics and mechanisms of atmospheric reactions. - the harwell laboratory (environmental pollution research centre) will conduct time resolved radical kinetics studies using u.v. and infrared diode laser spectroscopy as well as product studies. This will be complemented by similar studies at the Max-Planck Institut for chemistry at Mainz which also has a gas phase for FTIR spectroscopy capability as well as the unique matrix isolation FTIR set up. FTIR spectroscopy coupled with a large volume atmospheric simulation chamber comprises the unique capability at the university of Wuppertal which has demonstrated the feasibility of the studies of NOx reactions which form part of the present proposal. Finally the flash photolysis/UV absorption system at university of Bordeaux, laboratory of molecular photochemistry provides the capability for first time resolved kinetics studies of the radical reactions in a different time and concentration regime to the harwell and Mainz studies. Achievements: Spectroscopic, kinetic and mechanistic data have been obtained on simple organic peroxy radicals and HO2 through extensive laboratory experiments over a range of pressures and temperatures relevant to the troposphere (ie from ground level to the tropopause). Measurement of reaction rate constants and absorption cross sections were measured for atmospheric peroxy radicals derived from simple alkanes, aldehydes and alkenes, considered representative of major reactive organics in the tropospheres. Experimental methods for kinetic measurements were based on the analysis of the peroxy radicals by ultraviolet (UV) absorption spectroscopy. Particular attention has been drawn to the measurement of absorption cross sections of the most fundamental peroxy radicals...