Development of automated chemical sensors for dry deposition measurement by the gradient method

The central aim of the project is the development of new and/or the improvement of already existing chemical sensors for dry deposition measurements of nitrogen compounds in the field by a micrometeorological (gradient) method. For this specific application chemical sensors must fulfill the following requirements: - relative precision of concentration measurements smaller than 5%, - sensitivity smaller than 1 ppbv, - sampling intervals smaller than 2 h, - avoidance of artifact formation during sampling and interferences against other nitrogen containing constituents. Some of these requirements can be best realized by automatization of the corresponding techniques as far as possible. Within this project, the development/improvement of chemical sensors is limited to the - automated rotating annular denuder technique, - non-automated classicval (differentiaail) denuder techniques, and - automated "thermodenuder" technique. Priority is given to the measurement of HNO2, NH3, and HNO3. The d etermination of NO and NO2 is envisaged, while the measurement of H202, HCI, CH20 and SO2 is a "by-product" of the techniques. The developed techniques are verified during several field campaigns which include the intercomparison of the techniques, the test of their monitoring capacity, and finally the application to a micrometeorological method to determine dry deposiotion fluxes.