ACPD Atmospheric Chemistry and Physics Discussions ACPD 1680-7375 Copernicus GmbH Göttingen, Germany 10.5194/acpd-9-24669-2009 Surfactants in cloud droplet activation: mixed organic-inorganic particles Prisle N. L. 1 Raatikainen T. 2 Laaksonen A. 3 Bilde M. 1 University of Copenhagen, Department of Chemistry, Universitetsparken 5, 2100, Copenhagen, Denmark Finnish Meteorological Institute, Erik Palmenin Aukio 1, 00101, Helsinki, Finland University of Kuopio, Department of Physics, P.O. Box 1627, 70211, Kuopio, Finland 18 11 2009 9 6 24669 24715 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys-discuss.net/9/24669/2009/acpd-9-24669-2009.html The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/9/24669/2009/acpd-9-24669-2009.pdf

Organic compounds with surfactant properties are commonly found in atmospheric aerosol particles. Surface activity can significantly influence the cloud droplet forming ability of these particles. We have studied the cloud droplet formation by two-component particles comprising one of the organic surfactants sodium octanoate, sodium decanoate, sodium dodecanoate, and sodium dodecyl sulfate, mixed with sodium chloride. Critical supersaturations were measured with a static diffusion cloud condensation nucleus counter (Wyoming CCNC-100B). Results were modeled from Köhler theory applying three different representations of surfactant properties: (1) using concentration-dependent surface tension reduction during droplet growth and explicitly accounting for surfactant surface partitioning in both solute suppression (Raoult effect) and curvature enhancement (Kelvin effect) contributions to the droplet equilibrium water vapor supersaturation, (2) disregarding surfactant partitioning and using a concentration-dependent surface tension for the droplets corresponding to a macroscopic (bulk) aqueous solution of the same overall composition, and (3) disregarding surfactant properties and assuming the constant surface tension of pure water throughout droplet activation. We confirm previous results for single-component organic surfactant particles, that experimental critical supersaturations are greatly underpredicted, if reduced surface tension is applied in Köhler theory while ignoring the effects of surface partitioning in droplets. We further show that assuming the constant surface tension of pure water can also lead to significant underpredictions of experimental critical supersaturations. The full account for surfactant partitioning in activating droplets generally predicts experimental critical supersaturations well. In addition, for mixed particles comprising less than 50% by mass of surfactant, ignoring surfactant properties and simply using the constant surface tension of pure water also provides a good first-order approximation of the observed activation.

 References Asa-Awuku, A., Sullivan, A. P., Hennigan, C. J., Weber, R. J., and Nenes, A.: Investigation of molar volume and surfactant characteristics of water-soluble organic compounds in biomass burning aerosol, Atmos. Chem. Phys., 8, 799–812, 2008. Bianco, H. and Marmur, A.: The Dependence of the Surface Tension of Surfactant Solutions on Drop Size, Journal of Colloid and Interface Science, 151, 517–522, 1992. Bilde, M. and Svenningsson, B.: CCN Activation of Slightly Soluble Organics: The Importance of Small Amounts of Inorganic Salt and Particle Phase, Tellus, 56B, 128–134, 2004. Cheng, Y., Li, S.-M., Leithead, A., Brickell, P C., and Leaitch, W R.: Characterizations of \it cis-pinonic acid and n-fatty acids on fine aerosols in the Lower Fraser Valley during Pacific 2001 Air Quality Study, Atmos. Environ., 38, 5789––5800, 2004. Corrin, M L. and Harkins, W D.: The Effect of Salts on the Critical Concentration for the Formation of Micelles in Colloidal Electrolytes, J. Amer. Chem. Soc., 69, 683–688, 1947. Dinar, E., Taraniuk, I., Graber, E. R., Katsman, S., Moise, T., Anttila, T., Mentel, T. F., and Rudich, Y.: Cloud Condensation Nuclei properties of model and atmospheric HULIS, Atmos. Chem. Phys., 6, 2465–2482, 2006. Facchini, M., Mircea, M., Fuzzi, S., and Charlson, R.: Cloud Albedo Enhancement by Surface-Active Organic Solutes in Growing Droplets, Nature, 401, 257–259, 1999. Facchini, M., Decesari, S., Mircea, M., Fuzzi, S., and Loglio, G.: Surface Tension of Atmospheric Wet Aerosol and Cloud/Fog Droplets in Relation to their Organic Carbon Content and Chemical Composition, Atmos. Environ., 34, 4853–4857, 2000. Gibbs, J., Bumstead, H., Longley, W., and Name, R V.: The Collected Works of J. Willard Gibbs, Longmans, Green and Co., 1928. Hartz, K. E H., Rosenørn, T., Ferchak, S R., Raymond, T M., Bilde, M., Donahue, N M., and Pandis, S N.: Cloud Condensation Nuclei Activation of Monoterpene and Sesquiterpene Secondary Organic Aerosol, J. Geophys. Res., 110, D14208, doi:10.1029/2004JD005754, 2005. Henning, S., Rosenørn, T., D'Anna, B., Gola, A. A., Svenningsson, B., and Bilde, M.: Cloud droplet activation and surface tension of mixtures of slightly soluble organics and inorganic salt, Atmos. Chem. Phys., 5, 575–582, 2005. IPCC: Climate Change 2007, The Physical Science Basis, Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, 2007. Kiss, G., Tombácz, E., and Hansson, H.-C.: Surface Tension Effects of Humic-Like Substances in the Aqueous Extract of Tropospheric Fine Aerosol, J. Atmos. Chem., 50, 279–294, 2005. Köhler, H.: The Nucleus in and the Growth of Hygroscopic Droplets, Transactions of the Faraday Society, 32, 1152–1161, 1936. Laaksonen, A.: The Composition Size Dependence of Aerosols Created by Dispersion of Surfactant Solutions, J. Colloid Interf. Science, 159, 517–519, 1993. Li, Z., Williams, A., and Rood, M.: Influence of Soluble Surfactant Properties on the Activation of Aerosol Particles Containing Inorganic Solute, J. Atmos. Sci., 55, 1859–1866, 1998. Lin, B., McCormick, A V., Davis, H T., and Strey, R.: Solubility of sodium soaps in aqueous salt solutions, J. Colloid Interf. Science, 291, 543–549, 2005. Low, R.: A Theoretical Study of Nineteen Condensation Nuclei, Journal de Recherches Atmosphériques, 65–78, 1969. Matijevic, E. and Pethica, B A.: The properties of ionized monolayers, Part 1. Sodium dodecyl sulphate at the air/water interface, Trans. Faraday Soc., 54, 1383–1389, 1958. Mochida, M., Kitamori, Y., Kawamura, K., Nojiri, Y., and Suzuki, K.: Fatty acids in the marine atmosphere: Factors governing their concentrations and evaluation of organic films on sea-salt particles, J. Geophys. Res., 107, D17S4325, \doi10.1029/2001JD001278, 2002. Mochida, M., Kawamura, K., Umemoto, N., Kobayashi, M., Matsunaga, S., Lim, H.-J., Turpin, B., Bates, T., and Simoneit, B.: Spatial distributions of oxygenated organic compounds (dicarboxylic acids, fatty acids, and levoglucosan) in marine aerosols over the western Pacific and off the coast of East Asia: Continental outflow of organic aerosols during the ACE-Asia campaign, J. Geophys. Res., 108, D23S8638, \doi10.1029/2002JD003249, 2003. Murphy, D M., Cziczo, D J., Froyd, K D., Hudson, P K., Matthew, B M., Middlebrook, M., Peltier, R E., Sullivan, A., Thomson, D S., and Weber, R J.: Single-particle mass spectrometry of tropospheric aerosol particles, J. Geophys. Res., 111, D23S32, \doi10.1029/2006JD007340, 2006. Oros, D. and Simoneit, B.: Identification and emission rates of molecular tracers in coal smoke particulate matter, Fuel, 79, 515–536, 2000. Prisle, N L.: Cloud Condensation Nuclei Properties of Organic Aerosol Particles: Effects of Acid Dissociation and Surfactant Partitioning, M.Sc. Thesis, Department of Chemistry, University of Copenhagen, 2006. Prisle, N L., Raatikainen, T., Sorjamaa, R., Svenningsson, B., Laaksonen, A., and Bilde, M.: Surfactant partitioning in cloud droplet activation: a study of C8, C10, C12 and C14 normal fatty acid sodium salts, Tellus, 60B, 416–431, \doi10.1111/j.1600-0889.2008.00352.x, 2008. Prisle, N L., Vanhanen, J., Bilde, M., Laaksonen, A., and Hyvärinen, A.-P.: Surface tensions of ternary aqueous fatty acid sodium salt and NaCl solutions measured with the Wilhelmy plate and capillary rise methods, in preparation, 2009. Rehfeld, S J.: Adsorption of Sodium Dodecyl Sulfate at Various Hydrocarbon-Water Interfaces, J. Phys. Chem., 71, 738–745, 1967. Rood, M J. and Williams, A L.: Reply, J. Atmos. Sci., 58, 1468–1473, 2001. Ruehl, C. R., Chuang, P. Y., and Nenes, A.: Aerosol hygroscopicity at high (99 to 100%) relative humidities, Atmos. Chem. Phys. Discuss., 9, 15595–15640, 2009. Shulman, M., Jacobson, M., Charlson, R., Synovec, R., and Young, T.: Dissolution Behavior and Surface Tension Effects of Organic Compounds in Nucleating Cloud Droplets, Geophys. Res. Lett., 23, 277–280, 1996. Snider, J R., Petters, M D., Wechsler, P., and Liu, P S K.: Supersaturation in the Wyoming CCN Instrument, J. Atmos. Oceanic Technol., 23, 1323–1339, 2006. Sorjamaa, R. and Laaksonen, A.: The influence of surfactant properties on critical supersaturations of cloud condensation nuclei, J. Aerosol Sci., 37, 1730–1736, 2006. Sorjamaa, R., Svenningsson, B., Raatikainen, T., Henning, S., Bilde, M., and Laaksonen, A.: The role of surfactants in Köhler theory reconsidered, Atmos. Chem. Phys., 4, 2107–2117, 2004. Svenningsson, B., Rissler, J., Swietlicki, E., Mircea, M., Bilde, M., Facchini, M. C., Decesari, S., Fuzzi, S., Zhou, J., Mønster, J., and Rosenørn, T.: Hygroscopic growth and critical supersaturations for mixed aerosol particles of inorganic and organic compounds of atmospheric relevance, Atmos. Chem. Phys., 6, 1937–1952, 2006. Szyskowski, B V.: Experimentelle studien über kapillare eigenschaften der wässerigen lösungen von fettsauren, Zeitschrift für Physikalische Chemie, 64, 385––414, 1908. Tabazadeh, A.: Organic aggregate formation in aerosols and its impact on the physicochemical properties of atmospheric particles, Atmos. Environ., 39, 5472–5480, 2005. Tuckermann, R.: Surface tension of aqueous solutions of water-soluble organic and inorganic compounds, Atmos. Environ., 41, 6265––6275, 2007. Vanhanen, J., Hyvärinen, A.-P., Anttila, T., Raatikainen, T., Viisanen, Y., and Lihavainen, H.: Ternary solution of sodium chloride, succinic acid and water; surface tension and its influence on cloud droplet activation, Atmos. Chem. Phys., 8, 4595–4604, 2008. Yassaa, N., Meklati, B Y., Cecinato, A., and Marino, F.: Particulate n-alkanes, n-alkanoic acids and polycyclic aromatic hydrocarbons in the atmosphere of Algiers City Area, Atmos. Environ., 35, 1843–1851, 2001.