Das Projekt "Long Term Observations of Urban Atmospheric Radical Chemistry (Turban)" wird vom Umweltbundesamt gefördert und von Universität Heidelberg, Institut für Umweltphysik durchgeführt. The nitrate radical (NO3) is a key component of night time chemistry in the troposphere and is responsible for the non-photochemical production of peroxy radicals and the transformation of important species such as nitrogen oxides, VOCs, and ozone. It can be comparable to the OH radical as a sink for nitrogen oxides and VOCs. The only two studies to provide long term night time measurements of NO3 in the boundary layer were conducted in Germany at a rural coastal site and a rural suburban site. One short-term study has reported daytime measurements of NO3. More research is necessary to obtain a complete picture of seasonal variations in NO3 chemistry. Our objectives are to describe seasonal and spatial patterns in the chemistry of NO3 in an arid urban location, and to evaluate its contribution to the transformation and removal of atmospheric compounds. Two years of continuous Differential Optical Absorbance Spectrometry (DOAS) measurements in Jerusalem will provide concentrations of NO3, NO2, NO, O3, HONO, and HCHO, in addition to meteorology and other ancillary parameters. A month-long field project using high-end DOAS equipment will be conducted in parallel in order to assess spatial variations in NO3 chemistry in the region. The proposed research will be the first to conduct continuous long-term measurements of NO3 in an urban area, and the first in an arid region such as Israel. No long-term measurements of NO3 in the daytime have yet been reported. The resulting data will improve our understanding of NO3 chemistry in the urban boundary layer.