Das Projekt "Die Bewertung von Quellen von Radikalen in der atmosphaerischen Chemie mittels Kammer- und Laboruntersuchungen" wird vom Umweltbundesamt gefördert und von Max-Planck-Institut für Chemie (Otto-Hahn-Institut) durchgeführt. Ozone is a toxic gas, high concentrations of which in the boundary layer can have adverse effects on human health, vegetation and materials. Ozone is produced as a result of the interaction of volatile organic compounds (VOCs) and nitrogen oxides (NOx) in the presence of sunlight. Elevated levels of ozone are frequent occurrences across much of Europe, particularly during the summer months. Concerted international action is needed to reduce precursor emission if episodic and mean ozone concentrations are to be reduced. As individual VOCs can make a different quantitative impact on ozone formation, it is important that controls should focus not only on those sectors having the largest emissions of VOCs but also on those activities, the emissions of which have large potentials to form ozone. The RADICAL project has been submitted to obtain new data on the photolysis of oxygenated compounds involved in the atmospheric oxidation of key VOCs. As these photodissociation processes can lead to the formation of additional radicals, they have tremendous importance for a) the atmospheric oxidation capacity, and, b) local and regional formation of ozone and other photo-oxidants and hence the ozone formation potential of the precursor-VOCs. The lack of data on these processes limits the reliability of the atmospheric chemistry models used to assess photochemical ozone production. The research programme proposed for the RADICAL project will contribute to the achievement of the objectives outlined for Area 1,2,1,2 of the Environment and Climate work programme on Tropospheric Physics and Chemistry. The research programme will involve: 1) The synthesis of the compounds identified for study; 2) The measurement and quantification of UV-visible absorption spectra 3) The measurement of rates and products of photochemical processes under laboratory and atmospheric conditions using small-scale and large scale smog chambers; 4) The derivation of average quantum yields for use in atmospheric models; 5) The measurement of rate coefficients of other important loss reactions in the atmosphere; 6) An assessment of the implications for ground-level ozone production using a photochemical trajectory model. The six groups involved in the RADICAL project have formed a successful partnership during the present EC BIOVOC project. All the groups have extensive experience of co-ordinating and participating in projects supported by the European Commission. The results obtained will provide new input data for numerical modelling tools which are used to understand and assess the factors that contribute to ground-level ozone production. This will ensure that the conclusions from future assessments can be made with greater confidence and lead to the implementation of cost-effective reduction strategies.