Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 6 3 2006 10.5194/acpd-6-3657-2006 http://www.atmos-chem-phys-discuss.net/6/3657/2006/ http://www.atmos-chem-phys-discuss.net/6/3657/2006/acpd-6-3657-2006.html http://www.atmos-chem-phys-discuss.net/6/3657/2006/acpd-6-3657-2006.pdf 3657 3685 2006-05-10 Importance of the surface reaction OH+Cl^- on sea salt aerosol for the chemistry of the marine boundary layer – a model study R. von Glasow Institute of Environmental Physics, University of Heidelberg, Im Neuenheimer Feld 229, 69120 Heidelberg, Germany The reaction of the hydroxyl radical with chloride on the surface of sea salt aerosol producing gas phase Cl₂ and particulate OH^- and its implications for the chemistry of the marine boundary layer under coastal, remote, and very remote conditions have been investigated with a numerical model. This reaction had been suggested by Laskin et al. (2003) to play a major role in the sulfur cycle in the marine boundary layer by increasing the sulfate production in sea salt by O₃ oxidation due to the additional production of alkalinity in the particle. Based on literature data a new &quotbest estimate'' for the rate coefficient of the reaction was deduced and applied, showing that the additional initial sulfate production by this reaction is less than 1%, therefore having only a minor impact on sulfate production. Even though the gas phase concentration of Cl₂ increased strongly in the model the concentration of Cl radicals increased by less than 5% for the &quotbest guess'' case. Additional feedbacks between the cycles of chlorine and sulfur in the marine boundary layer are discussed as well as a two-stage acidification of large fresh sea salt aerosol.