Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 3 3 2003 10.5194/acpd-3-3135-2003 http://www.atmos-chem-phys-discuss.net/3/3135/2003/ http://www.atmos-chem-phys-discuss.net/3/3135/2003/acpd-3-3135-2003.html http://www.atmos-chem-phys-discuss.net/3/3135/2003/acpd-3-3135-2003.pdf 3135 3169 2003-06-19 Role of NO₃ radical in oxidation processes in the eastern Mediterranean troposphere during the MINOS campaign M. Vrekoussis M. Kanakidou N. Mihalopoulos P. J. Crutzen J. Lelieveld D. Perner H. Berresheim E. Baboukas Environmental Chemical Processes Laboratory, Department of Chemistry, University of Crete, P.O. Box 1470, 71409 Heraklion, Greece Max-Planck-Institut für Chemie, Abt. Luftchemie, Mainz, Germany Deutscher Wetterdienst, Meteorologisches Observatorium, DWD, Germany During the MINOS campaign (28 July&ndash;18 August 2001) nitrate (NO₃) radical was measured at Finokalia, on the north coast of Crete in South-East Europe using a long path (10.4 km) Differential Optical Absorption Spectroscopy instrument (DOAS). Hydroxyl (OH) radical was also measured by a Chemical Ionization Mass-Spectrometer (Berresheim et al., this issue). These datasets represent the first simultaneous measurements of OH and NO₃ radicals in the area. NO₃ radical concentrations ranged from less than 3·10⁷ up to 9·10⁸ radical·cm^-3 with an average value of 1.1·10⁸ radical·cm^&minus;3.&nbsp;<br> <br> The observed NO₃ mixing ratios are analyzed on the basis of the corresponding meteorological data and the volatile organic compound (VOC) observations simultaneously obtained at Finokalia station. The importance of the NO₃ radical relatively to that of OH in the dimethylsulfide (DMS) and nitrate cycles is also investigated. The observed NO₃ levels clearly regulate the diurnal variation of DMS. NO₃ and N₂O₅ reactions account for about 21% of the total nitrate (HNO_3(g) + NO^&minus;_3(part)) production.