Das Projekt "Investigation of the influences of halo chemistry on the oxidation capacitiy of the troposphere in mid-latitudes and the ozon budget including horizontal and vertical transport phenomena during long terms LOT" wird vom Umweltbundesamt gefördert und von Universität Heidelberg, Institut für Umweltphysik durchgeführt. Reactive Halogen Species (RHS) can severely impact tropospheric chemistry. The destruction of boundary layer ozone by catalytic reaction cycles involving bromine and chlorine has been observed in polar regions and at mid latitudes. Iodine compounds have been found in the marine troposphere, too, and are supposed to change the atmospheric chemistry significantly. In a joint project between the Hebrew University Jerusalem and the University of Heidelberg, who have previously cooperated successfully for a long time, we propose investigating the influence of Reactive Halogen Species on the tropospheric chemistry and its relation to transport processes. In previous projects performed by the present proposers, the highest levels of BrO and IO ever previously observed in the atmosphere were recorded. The formation of these reactive halogens was undoubtedly related to the chemical behaviour and especially ozone depletion processes observed in the troposphere. However, our investigations have also shown that transport phenomena must play an important role in RHS formation. Due to its unique geographical position, topography, meteorology and the chemical composition of the sea waters, the Dead Sea valley is an ideal natural laboratory for the proposed investigations. The questions that will be addressed in the proposed investigation will include the determination of the horizontal and vertical distribution of RHS at the Dead Sea by measuring transport phenoma as well as seasonal fluctuation (long term). The existence of reservoir gases like BrONO2 will be in focus (new interesting link between NO2& 8211; and halogen chemistry). This will enable a deeper understanding of the release mechanisms of RHS. These 3D-observations of RHS distribution over the Dead Sea, coupled with increased information regarding RHS formation and modelling studies will substantially expand our knowledge regarding tropospheric chemistry and especially ozone depletion chemistry and their dynamics on a regional and global scale.
Das Projekt "Der Beitrag reaktiver Halogenarten auf die Oxidationsfaehigkeit der reaktiven Halogenarten in der Troposphaere: Zyklen - Mechanismen - und Feldbeobachtungen - HALOTROP-CYMFO" wird vom Umweltbundesamt gefördert und von Universität Heidelberg, Institut für Umweltphysik durchgeführt. This study is a contribution to the part of the programme dealing with the Oxidation Capacity of the Troposphere. It will be achieved by coordinated field-, laboratory- and modelling investigations of reactive halogen species, their precursor and storage species, and the reaction mechanisms involved. Field measurements will include direct determination of halogen oxides by Differential Optical Absorption Spectroscopy (DOAS) at sub-ppt levels. The laboratory studies will close many gaps in our knowledge of RHS related homogeneous and surface-catalyzed reactions including iodine chemistry. The latest data from field and laboratory studies will be assembled in trajectory- and limited area 3D models, which will help to understand the results of the field campaigns as well as to assess the regional impact of RHS chemistry. A further important part of this study will be the assessment of a possibly anthropogenic influence on RHS sources and the transformation mechanisms within the RHS reservoir. Thus possible mechanisms changing the tropospheric oxidation capacity due to human activities can be investigated. While a central question concerns the importance of release of RHS from sea salt aerosol, for instance due to reaction of anthropogenic NOy species (like N205, NO2) with sea salt aerosol, the detailed investigation of those processes is the aim of a parallel study with the sub-title 'Sea Salt Aerosols: Laboratory Investigation of Heterogeneous Halogen Activation in the Troposphere (HALOTROP-SALT). Areas where enhanced levels of RHS are to be expected (like polluted coastlines or polar regions) will be identified. Regional processes involving RHS will be set into a global perspective.