Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 9 2 2009 10.5194/acpd-9-9291-2009 http://www.atmos-chem-phys-discuss.net/9/9291/2009/ http://www.atmos-chem-phys-discuss.net/9/9291/2009/acpd-9-9291-2009.html http://www.atmos-chem-phys-discuss.net/9/9291/2009/acpd-9-9291-2009.pdf 9291 9312 2009-04-08 BrO measurements over the Eastern North-Atlantic M. Martin maria.martin@env.ethz.ch D. Pöhler K. Seitz R. Sinreich U. Platt Institute for Environmental Physics, University of Heidelberg, Im Neuenheimer Feld 229, 69120 Heidelberg, Germany present address: ETH Institute for Atmospheric and Climate Science, Universitaetsstrasse 16, 8092 Zurich, Switzerland present address: Department of Chemistry and Biochemistry, University of Colorado at Boulder, UCB 215, Boulder, CO 80309-0215, USA The aim of the work presented here was to detect BrO in the marine boundary layer over the Eastern North-Atlantic by Multi AXis-Differential Optical Absorption Spectroscopy (MAX-DOAS) of scattered sunlight. With this technique, information about the concentration and the vertical profile of trace gases in the atmosphere can be gained. BrO can be formed in the marine atmosphere by degradation of biogenic organohalogens or by oxidation of bromide in sea salt aerosol. BrO influences the chemistry in marine air in many was, e.g. since it catalytically destroys ozone, changes the NO₂/NO-ratio as well as the OH/HO₂-ratio and oxidises DMS. However, the abundance and the significance of BrO in the marine atmosphere are not yet fully understood. <br><br> We report on data collected during a ship cruise, which took place along the West African Coast in February 2007, within the framework of the Surface Ocean PRocesses in the ANthropocene project (SOPRAN). Tropospheric BrO could be detected during this cruise at peak mixing ratios of (10.2&plusmn;3.7) ppt at an assumed layer height of 1 km on 18 February 2007. Furthermore, it was found that the mean BrO concentrations increased when cruising close to the African Coast suggesting that at least part of the BrO might have originated from the African coast. 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