Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 4 6 2004 10.5194/acpd-4-7463-2004 http://www.atmos-chem-phys-discuss.net/4/7463/2004/ http://www.atmos-chem-phys-discuss.net/4/7463/2004/acpd-4-7463-2004.html http://www.atmos-chem-phys-discuss.net/4/7463/2004/acpd-4-7463-2004.pdf 7463 7485 2004-11-10 Cloud droplet activation and surface tension of mixtures of slightly soluble organics and inorganic salt S. Henning T. Rosenørn B. D’Anna A. A. Gola B. Svenningsson M. Bilde Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark Department of Chemistry, University of Oslo, N-0315 Oslo, Norway Department of Physical Chemistry, Medical University of Wroclaw, pl. Nankiera 1, 50-140 Wroclaw, Poland Critical supersaturations for internally mixed particles of adipic acid, succinic acid and sodium chloride were determined experimentally for dry particles sizes in the range 40–130 nm. Surface tensions of aqueous solutions of the dicarboxylic acids and sodium chloride corresponding to concentrations at activation were measured and parameterized as a function of carbon content. The activation of solid particles as well as solution droplets were studied and particle phase was found to be important for the critical supersaturation. Experimental data were modelled using Köhler theory modified to account for limited solubility and surface tension lowering.