Das Projekt "Kernbildungsprozesse durch Oxidation biogener fluechtiger organischer Verbindungen (NUCVOC)" wird vom Umweltbundesamt gefördert und von Gesellschaft zur Förderung der Spektrochemie und Angewandten Spektroskopie, Institut für Spektrochemie und Angewandte Spektroskopie durchgeführt. Atmospheric aerosol particles affect the Earth's radiative balance both directly through backscatter of solar radiation and indirectly as cloud condensation nuclei (CCN). At present, the effects of the tropospheric aerosols are one of the largest uncertainties in quantifying climate forcing due to man-made changes in the composition of the atmosphere. The main tasks covered by NUCVOC addresses two aspects with considerable tropospheric relevance: -to evaluate the formation of aerosol quantitatively from natural sources with special emphasis on new particle formation processes, -to gain information about the organic component of the tropospheric aerosol. The overall objectives of the NUCVOC projekt can be summarized as follows: Systematic investigation of the formation of particles of selected model compounds (alpha-pinene, beta-pinene, limonene, sabinene etc) in laboratory studies (considering oxidation by NOdeep3, OH, Odeep3 reactions). Chemical analysis of the organic particle phase focusing on the very non-volatile fraction of the biogenic oxidation products. Development of the chemical mechanism describing the routes to form condensable species. Experimental verification of the nucleating abilities of certain products by A) The synthesis of a few selesignificant oxidation products. B) The determination of relevant physical parameters of these compounds (surface tension, density etc). C) The use of the thermal diffusion cloud chamber. Modelling the formation of particles (homogeneous nucleation, condensation, coagulation etc) The contribution of our group will consist of following objectives: -Measuring rates of the formation of aerosol from terpenes (model compounds) reactions with NOdeep3 radicals, using time resolved techniques. NOdeep3 radicals will be generated by flash light photolysis using suitable precursor (ie HNOdeep3) and its decay in real time will be studied using laser longpath absorption. The relation of extinction of the laser light and the particle characteristics is expected to provide information on the homogeneous nucleation rates of the oxidation products. Identification of the oxidation products of biogenic VOC reactions using a photochemical smog chamber / FTIR technique. The experimental study will be accompanied by modelling studies of the homogeneous nucleation rate of oxidation products of biogenic VOC using classical nucleation theory.
Das Projekt "EUROTRAC II: Der Lebenszyklus troposphaerischer Aerosole" wird vom Umweltbundesamt gefördert und von Paul Scherrer Institut durchgeführt. Short description: The life cycle of the tropospheric aerosol is investigated by addressing three different topics: the chemical mass balance of the tropospheric aerosol needed to perform a source apportionment; - the impact of heterogeneous processes on the surface chemistry of the aerosol and the gas phase chemistry of the troposphere; - and the major removal processes of aerosol particles from the atmosphere. The project will help in improving the quantitative understanding of these processes and thus assist in alleviating the environmental problems related to aerosols. Project aims: By changing the surface properties of the aerosol particles, heterogeneous processes are assumed to increase the capabilities of these particles of act as cloud condensation nuclei (CCN) and ice forming nuclei (IN) during cloud formation. However, a great uncertainty still exists which aerosol particles actually serve as CCN and IN and, on the other hand, to which extent cloud processing further alters the chemical properties of the involved particles. Since clouds are important for the transport, transformation and deposition of acidifying species and have also been shown to affect the regional budget of photo-oxidants in the atmosphere, we therefore propose to investigate the chemical properties of CCN and IN in cold clouds during field experiments which will be conducted at the high-alpine research station Jungfraujoch (3450 m asl). Techniques will be improved to collect individual ice crystals and cloud droplets and to chemically analyze the scavenged trace species in both.