ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-13-1081-2013 A single parameter representation of hygroscopic growth and cloud condensation nucleus activity – Part 3: Including surfactant partitioning Petters M. D. 1 Kreidenweis S. M. 2 Department of Marine Earth and Atmospheric Sciences, North Carolina State University, Raleigh, NC, USA Department of Atmospheric Science, Colorado State University, Fort Collins, CO, USA 28 01 2013 13 2 1081 1091 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.net/13/1081/2013/acp-13-1081-2013.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/13/1081/2013/acp-13-1081-2013.pdf

Atmospheric particles can serve as cloud condensation nuclei in the atmosphere. The presence of surface active compounds in the particle may affect the critical supersaturation that is required to activate a particle. Modelling surfactants in the context of Köhler theory, however, is difficult because surfactant enrichment at the surface implies that a stable radial concentration gradient must exist in the droplet. In this study, we introduce a hybrid model that accounts for partitioning between the bulk and surface phases in the context of single parameter representations of cloud condensation nucleus activity. The presented formulation incorporates analytical approximations of surfactant partitioning to yield a set of equations that maintain the conceptual and mathematical simplicity of the single parameter framework. The resulting set of equations allows users of the single parameter model to account for surfactant partitioning by applying minor modifications to already existing code.

 References Bianco, H. and Marmur, A.: The Dependence of the surface tension of surfactant solutions on drop size, J. Coll. Interf. Sci., 151, 517–522, 1992. Carrico, C. M., Petters, M. D., Kreidenweis, S. M., Collett, J. L., Engling, G., and Malm, W. C.: Aerosol hygroscopicity and cloud droplet activation of extracts of ?lters from biomass burning experiments, J. Geophys. Res., 113, 08206, http://dx.doi.org/10.1029/2007JD009274doi:10.1029/2007JD009274, 2008. Carrico, C. M., Petters, M. D., Kreidenweis, S. M., Sullivan, A. P., McMeeking, G. R., Levin, E. J. T., Engling, G., Malm, W. C., and Collett Jr., J. L.: Water uptake and chemical composition of fresh aerosols generated in open burning of biomass, Atmos. Chem. Phys., 10, 5165–5178, http://dx.doi.org/10.5194/acp-10-5165-2010doi:10.5194/acp-10-5165-2010, 2010. Cerully, K. M., Raatikainen, T., Lance, S., Tkacik, D., Tiitta, P., Petäjä, T., Ehn, M., Kulmala, M., Worsnop, D. R., Laaksonen, A., Smith, J. N., and Nenes, A.: Aerosol hygroscopicity and CCN activation kinetics in a boreal forest environment during the 2007 EUCAARI campaign, Atmos. Chem. Phys., 11, 12369–12386, http://dx.doi.org/10.5194/acp-11-12369-2011doi:10.5194/acp-11-12369-2011, 2011. Chan, M. N., Kreidenweis, S. M., and Chan, C. K.: Measurements of the Hygroscopic and Deliquescence Properties of Organic Compounds of Different Solubilities in Water and Their Relationship with Cloud Condensation Nuclei Activities, Environ. Sci. Technol., 42, 3602–3608, 2008. Chang, C.-H. and Franses, E. I.: Adsorption dynamics of surfactants at the air/water interface: a critical review of mathematical models, data, and mechanisms, Colloid and Surfaces A: Physicochem. Eng. Aspects, 100, 1–45, 1995. Christensen, S. I. and Petters, M. D.: The role of temperature in cloud droplet activation, J. Phys. Chem. A, 116, 9706–9717, http://dx.doi.org/10.1021/jp3064454doi:10.1021/jp3064454, 2012. Clegg, S. L., Brimblecombe, P., and Wexler, A. S.:Thermodynamic model of the system H$^+$-NH$_4^+$-Na$^+$-SO$_4^2-$-NO$_3^-$-Cl$^-$-H<sub>2</sub>O at 298.15 K, J. Phys. Chem. A, 102, 2155–2171, http://dx.doi.org/10.1021/jp973043jdoi:10.1021/jp973043j, 1998. Duplissy, J., Gysel, M., Alfarra, M. R., Dommen, J., Metzger, A., Prevot, A. S. H., Weingartner, E., Laaksonen, A., Raatikainen, T., Good, N., Turner, S. F., McFiggans, G., and Baltensperger, U.: Cloud forming potential of secondary organic aerosol under near atmospheric conditions, Geophys. Res. Lett., 35, L03818, doi:03810.01029/02007GL031075, 2008. Dusek, U., Frank, G. P., Curtius, J., Drewnick, F., Schneider, J., Kürten, A., Rose, D., Andreae, M. O., Borrmann, S., and Pöschl, U.: Enhanced organic mass fraction and decreased hygroscopicity of cloud condensation nuclei (CCN) during new particle formation events, Geophys. Res. Lett., 37, L03804, http://dx.doi.org/10.1029/2009GL040930doi:10.1029/2009GL040930, 2010. Engelhart, G. J., Asa-Awuku, A., Nenes, A., and Pandis, S. N.: CCN activity and droplet growth kinetics of fresh and aged monoterpene secondary organic aerosol, Atmos. Chem. Phys., 8, 3937–3949, http://dx.doi.org/10.5194/acp-8-3937-2008doi:10.5194/acp-8-3937-2008, 2008. Facchini, M. C., Mircea, M., Fuzzi, S., and Charlson, R. J.: Cloud albedo enhancement by surface-active organic solutes in growing droplets, Nature, 401, 257–259, http://dx.doi.org/10.1038/45758doi:10.1038/45758, 1999. Facchini, M. C., Descesari, 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. George, I. J. and Abbatt, J. P. D.: Chemical evolution of secondary organic aerosol from OH-initiated heterogeneous oxidation, Atmos. Chem. Phys., 10, 5551–5563, http://dx.doi.org/10.5194/acp-10-5551-2010doi:10.5194/acp-10-5551-2010, 2010. Good, N., Topping, D. O., Allan, J. D., Flynn, M., Fuentes, E., Irwin, M., Williams, P. I., Coe, H., and McFiggans, G.: Consistency between parameterisations of aerosol hygroscopicity and CCN activity during the RHaMBLe discovery cruise, Atmos. Chem. Phys., 10, 3189–3203, http://dx.doi.org/10.5194/acp-10-3189-2010doi:10.5194/acp-10-3189-2010, 2010a. Good, N., Topping, D. O., Duplissy, J., Gysel, M., Meyer, N. K., Metzger, A., Turner, S. F., Baltensperger, U., Ristovski, Z., Weingartner, E., Coe, H., and McFiggans, G.: Widening the gap between measurement and modelling of secondary organic aerosol properties?, Atmos. Chem. Phys., 10, 2577–2593, http://dx.doi.org/10.5194/acp-10-2577-2010doi:10.5194/acp-10-2577-2010, 2010b. Gunthe, S. S., King, S. M., Rose, D., Chen, Q., Roldin, P., Farmer, D. K., Jimenez, J. L., Artaxo, P., Andreae, M. O., Martin, S. T., and Pöschl, U.: Cloud condensation nuclei in pristine tropical rainforest air of Amazonia: size-resolved measurements and modeling of atmospheric aerosol composition and CCN activity, Atmos. Chem. Phys., 9, 7551–7575, http://dx.doi.org/10.5194/acp-9-7551-2009doi:10.5194/acp-9-7551-2009, 2009. 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, http://dx.doi.org/10.5194/acp-5-575-2005doi:10.5194/acp-5-575-2005, 2005. Hings, S. S., Wrobel, W. C., Cross, E. S., Worsnop, D. R., Davidovits, P., and Onasch, T. B.: CCN activation experiments with adipic acid: effect of particle phase and adipic acid coatings on soluble and insoluble particles, Atmos. Chem. Phys., 8, 3735–3748, http://dx.doi.org/10.5194/acp-8-3735-2008doi:10.5194/acp-8-3735-2008, 2008. Irwin, M., Good, N., Crosier, J., Choularton, T. W., and McFiggans, G.: Reconciliation of measurements of hygroscopic growth and critical supersaturation of aerosol particles in central Germany, Atmos. Chem. Phys., 10, 11737–11752, http://dx.doi.org/10.5194/acp-10-11737-2010doi:10.5194/acp-10-11737-2010, 2010. Jimenez, J. L., Canagaratna, M. R., Donahue, N. M., Prevot, A. S., Zhang, Q., Kroll, J. H., DeCarlo, P. F., Allan, J.D., Coe, H., Ng, N. L., Aiken, A. C., Docherty, K. S., Ulbrich, I. M., Grieshop, A. P., Robinson, A. L., Duplissy, J., Smith, J. D., Wilson, K. R., Lanz, V. A., Hueglin, C., Sun, Y. L., Tian, J., Laaksonen, A., Raatikainen, T., Rautiainen, J., Vaattovaara, P., Ehn, M., Kulmala, M., Tomlinson, J. M., Collins, D. R., Cubison, M. J., Dunlea, E. J., Huffman, J. A., Onasch, T. B., Alfarra, M. R., Williams, P. I., Bower, K., Kondo, Y., Schneider, J., Drewnick, F., Borrmann, S., Weimer, S., Demerjian, K., Salcedo, D., Cottrell, L., Griffin, R., Takami, A., Miyoshi, T., Hatakeyama, S., Shimono, A., Sun, J. Y., Zhang, Y. M., Dzepina. K., Kimmel, J. R., Sueper, D., Jayne, J. T., Herndon, S. C., Trimborn, A. M., Williams, L. R., Wood, E. C., Middlebrook, A. M., Kolb, C. E., Baltensperger, U., and Worsnop, D. R.: Evolution of organic aerosols in the atmosphere, Science, 326, 1525–1529, 2009. King, S. M., Rosenoern, T., Shilling, J. E., Chen, Q., and Martin, S. T.: Increased cloud activation potential of secondary organic aerosol for atmospheric mass loadings, Atmos. Chem. Phys., 9, 2959–2971, http://dx.doi.org/10.5194/acp-9-2959-2009doi:10.5194/acp-9-2959-2009, 2009. Kloubek, J.: Measurement of the dynamic surface tension by the maximum bubble pressure method. IV. Surface tension of aqueous solutions of sodium dodecyl sulfate, J. Colloid Interface. Sci., 41, 17–22, 1972. Kreidenweis, S. M., Koehler, K., DeMott, P. J., Prenni, A. J., Carrico, C., and Ervens, B.: Water activity and activation diameters from hygroscopicity data – Part I: Theory and application to inorganic salts, Atmos. Chem. Phys., 5, 1357–1370, http://dx.doi.org/10.5194/acp-5-1357-2005doi:10.5194/acp-5-1357-2005, 2005. Kreidenweis, S. M., Petters, M. D., and Chuang, P. Y.: Cloud particle precursors, Clouds in the Perturbed Climate System: Their Relationship to Energy Balance, Atmospheric Dynamics, and Precipitation, Strüngmann Forum Report, edited by: Heintzenberg, J. and Charlson, R. J., The MIT Press, 13, Cambridge, Massachusetts, ISBN 978-0-262-01287-4, 2009. Li, Z., Williams, A. L., and Rood, M. J.: In?uence of soluble surfactant properties on the activation of aerosol particles containing inorganic solute, J. Atmos. Sci., 55, 1859–1866, 1998 Lohmann, U. and Hoose, C.: Sensitivity studies of different aerosol indirect effects in mixed-phase clouds, Atmos. Chem. Phys., 9, 8917–8934, http://dx.doi.org/10.5194/acp-9-8917-2009doi:10.5194/acp-9-8917-2009, 2009. Mochida, M., Nishita-Hara, C., Kitamori, Y., Aggarwal, S. G., Kawamura, K., Miura, K., and Takami, A.: Size-segregated measurements of cloud condensation nucleus activity and hygroscopic growth for aerosols at Cape Hedo, Japan, in spring 2008, J. Geophys. Res., 115, 20 D21207, http://dx.doi.org/10.1029/2009JD013216doi:10.1029/2009JD013216, 2010. Moore, R. H, Ingall, E. D., Sorooshian, A., and Nenes, A.: Molar mass, surface tension, and droplet growth kinetics of marine organics from measurements of CCN activity, Geophys. Res. Lett., 35, L07801, http://dx.doi.org/10.1029/2008GL033350doi:10.1029/2008GL033350, 2008. Padro, L. T., Tkacik, D., Lathem, T., Hennigan, C., Sullivan, A. P., Weber, R. J., Huey, L. G., and Nenes, A.: Investigation of cloud condensation nuclei properties and droplet growth kinetics of the water-soluble aerosol fraction in Mexico City, J. Geophys. Res., 115, D09204, http://dx.doi.org/10.1029/2009JD013195doi:10.1029/2009JD013195, 2010. Patist, A., Oh. S. G., Leung, R., and Shah, D. O.:Kinetics of micellization: its significance to technological processes, Colloid and Surfaces A: Phyiscochem. Eng. Aspects, 176, 3–16, 2001. Pethica, B. A.: The adsorption of surface active electrolytes at the air/water interface, Trans. Faraday Soc., 50, 413–421, http://dx.doi.org/10.1039/TF9545000413doi:10.1039/TF9545000413, 1954. Petters, M. D. and Kreidenweis, S. M.: A single parameter representation of hygroscopic growth and cloud condensation nucleus activity, Atmos. Chem. Phys., 7, 1961–1971, http://dx.doi.org/10.5194/acp-7-1961-2007doi:10.5194/acp-7-1961-2007, 2007. Petters, M. D. and Kreidenweis, S. M.: A single parameter representation of hygroscopic growth and cloud condensation nucleus activity – Part 2: Including solubility, Atmos. Chem. Phys., 8, 6273–6279, http://dx.doi.org/10.5194/acp-8-6273-2008doi:10.5194/acp-8-6273-2008, 2008. Petters, M. D., Kreidenweis, S. M., Prenni, A. J., Sullivan, R. C., Carrico, C. M., Koehler, K. A., and Ziemann, P. J.: Role of molecular size in cloud droplet activation, Geophys. Res Lett., 36, L22801, http://dx.doi.org/10.1029/2009GL040131doi:10.1029/2009GL040131, 2009a. Petters, M. D., Wex, H., Carrico, C. M., Hallbauer, E., Massling, A., McMeeking, G. R., Poulain, L., Wu, Z., Kreidenweis, S. M., and Stratmann, F.: Towards closing the gap between hygroscopic growth and activation for secondary organic aerosol – Part 2: Theoretical approaches, Atmos. Chem. Phys., 9, 3999–4009, http://dx.doi.org/10.5194/acp-9-3999-2009doi:10.5194/acp-9-3999-2009, 2009b. Petters, M. D., C. M. Carrico, S. M. Kreidenweis, A. J. Prenni, P. J. DeMott, J. R. Collett Jr., and H. Moosmüller, Cloud condensation nucleation ability of biomass burning aerosol, J Geophys. Res., 114, D22205, http://dx.doi.org/10.1029/2009JD012353doi:10.1029/2009JD012353, 2009c. Pöschl, U., Rose, D., and Andreae, M. O.: Strüngmann Forum Report, Clouds in the perturbed climate system: Their relationship to energy balance, atmospheric dynamics, and precipitation. Particle hygroscopicity and cloud condensation nuclei activity, MIT Press, Cambridge, Massachusetts, ISBN 978-0-262-01287-4, 2009. Prenni, A. J., Petters, M. D., DeMott, P. J., Kreidenweis, S. M., Ziemann, P. J., Matsunaga, A., and Lim, Y. B.: Cloud drop activation of secondary organic aerosol, J. Geophys. Res., 112, D10223, doi:10210.11029/12006JD007963, 2007. 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, http://dx.doi.org/10.1111/j.1600-0889.2008.00352.xdoi:10.1111/j.1600-0889.2008.00352.x, 2008. Prisle, N. L., Raatikainen, T., Laaksonen, A., and Bilde, M.: Surfactants in cloud droplet activation: mixed organic-inorganic particles, Atmos. Chem. Phys., 10, 5663–5683, http://dx.doi.org/10.5194/acp-10-5663-2010doi:10.5194/acp-10-5663-2010, 2010. Prisle, N. L., Dal Maso, M., and Kokkola, H.: A simple representation of surface active organic aerosol in cloud droplet formation, Atmos. Chem. Phys., 11, 4073–4083, http://dx.doi.org/10.5194/acp-11-4073-2011doi:10.5194/acp-11-4073-2011, 2011. Prisle, N. L., Asmi, A., Topping, D., Partanen, A.-I., Romakkaniemi, S., Dal Maso, M., Kulmala, M., Laaksonen, A. , Lehtinen, K. E. J., McFiggans, G., and Kokkola, H.: Surfactant effects in global simulations of cloud droplet activation, Geophys. Res. Lett., 39, L05802, http://dx.doi.org/10.1029/2011GL050467doi:10.1029/2011GL050467, 2012. Raatikainen, T. and Laaksonen, A.: A simplified treatment of surfactant effects on cloud drop activation, Geosci. Model Dev., 4, 107–116, http://dx.doi.org/10.5194/gmd-4-107-2011doi:10.5194/gmd-4-107-2011, 2011. Rehfeld, S. J.: Adsorption of sodium dodecyl sulfate at various hydrocarbon-water interfaces, J. Phys. Chem., 71, 738–745, 1967. Rissler, J., Vestin, A., Swietlicki, E., Fisch, G., Zhou, J., Artaxo, P., and Andreae, M. O.: Size distribution and hygroscopic properties of aerosol particles from dry-season biomass burning in Amazonia, Atmos. Chem. Phys., 6, 471–491, http://dx.doi.org/10.5194/acp-6-471-2006doi:10.5194/acp-6-471-2006, 2006. Rissler, J., Svenningsson, B., Fors, E. O., Bilde, M., and Swietlicki, E.: An evaluation and comparison of cloud condensation nucleus activity models: Predicting particle critical saturation from growth at subsaturation, J. Geophys. Res., 115, D22208, http://dx.doi.org/10.1029/2010JD014391doi:10.1029/2010JD014391, 2010. 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., 10, 1329–1344, http://dx.doi.org/10.5194/acp-10-1329-2010doi:10.5194/acp-10-1329-2010, 2010. Seidl, W. and Hanel, G.: Surface-Active Substances on Rainwater and Atmospheric Particles, Pure Appl. Geophys., 121, 1077–1093, 1983. Seinfeld, J. H. and Pandis, S. N.: Atmospheric Chemistry and Physics: From Air Pollution to Climate Change, John Wiley & Sons, Hoboken, New Jersey, ISBN 978-0-471-72017-1, 2006. Sjogren, S., Gysel, M., Weingartner, E., Baltensperger, U., Cubison, M. J., Coe, H., Zardini, A., Marcolli, C., Krieger, U. K., and Peter, T.: Hygroscopic growth and water uptake kinetics of two-phase aerosol particles consisting of ammonium sulfate, adipic and humic acid mixtures, J. Aerosol Sci., 38, 157–171, http://dx.doi.org/10.1016/j.jaerosci.2006.11.005doi:10.1016/j.jaerosci.2006.11.005, 2007. Snider, J. R., Wex, H., Rose, D., Kristensson, A., Stratmann, F., Hennig, T., Henning, S., Kiselev, A., Bilde, M., Burkhardt, M., Dusek, U., Frank, G. P., Kiendler-Scharr, A., Mentel, Th. F., Petters, M. D., and Pöschl, U.: Intercomparison of CCN and hygroscopic fraction measurements from LExNo, J. Geophys. Res., 115, D11205, http://dx.doi.org/10.1029/2009JD012618doi:10.1029/2009JD012618, 2010. 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, http://dx.doi.org/10.5194/acp-4-2107-2004doi:10.5194/acp-4-2107-2004, 2004. Shinozuka, Y., Clarke, A. D., DeCarlo, P. F., Jimenez, J. L., Dunlea, E. J., Roberts, G. C., Tomlinson, J. M., Collins, D. R., Howell, S. G., Kapustin, V. N., McNaughton, C. S., and Zhou, J.: Aerosol optical properties relevant to regional remote sensing of CCN activity and links to their organic mass fraction: airborne observations over Central Mexico and the US West Coast during MILAGRO/INTEX-B, Atmos. Chem. Phys., 9, 6727–6742, http://dx.doi.org/10.5194/acp-9-6727-2009doi:10.5194/acp-9-6727-2009, 2009. Shulman, M. L., Jacobson, M. C., Charlson, R. J., Synovec, R. E., and Young, T. E.: Dissolution behavior and surface tension effects of organic compounds in nucleating cloud droplets, Geophys. Res. Lett., 23, 277–280, 1996. Sullivan, R. C., Moore, M. J. K., Petters, M. D., Kreidenweis, S. M., Roberts, G. C., and Prather, K. A.: Effect of chemical mixing state on the hygroscopicity and cloud nucleation properties of calcium mineral dust particles, Atmos. Chem. Phys., 9, 3303–3316, http://dx.doi.org/10.5194/acp-9-3303-2009doi:10.5194/acp-9-3303-2009, 2009a. Sullivan, R. C., Moore, M. J. K., Petters, M. D., Kreidenweis, S. M., Roberts, G. C., and Prather, K. A.: Timescale for hygroscopic conversion of calcite mineral particles through heterogeneous reaction with nitric acid, Phys. Chem. Chem. Phys., 11, 7826–7837, http://dx.doi.org/10.1039/b904217bdoi:10.1039/b904217b, 2009b. Svenningsson, B., Hansson, H. C., Wiedensohler, A., Noone, K., Ogren, J., Hallberg, A., and Colvile, R.: Hygroscopic Growth of Aerosol-Particles and Its Influence on Nucleation Scavenging in-Cloud – Experimental Results from Kleiner-Feldberg, J. Atmos. Chem., 19, 129–152, 1994. Tajima, K.: Radiotracer studies on adsorption of surface active substance at aqueous surface. III. The effects of salt on the adsorption of sodium dodecylsulfate, Bull. Chem. Soc. Jap., 44, 1767–1771, 1971. Topping, D.: An analytical solution to calculate bulk mole fractions for any number of components in aerosol droplets after considering partitioning to a surface layer, Geosci. Model Dev., 3, 635–642, http://dx.doi.org/10.5194/gmd-3-635-2010doi:10.5194/gmd-3-635-2010, 2010. Tuckermann, R.: Surface tension of aqueous solutions of water-soluble organic and inorganic compounds, Atmos. Environ., 41, 6265–6275, 2007. Tuckermann, R. and Cammenga, H. K.: The surface tension of aqueous solutions of some atmospheric water-soluble organic compounds, Atmos. Environ., 38, 6135–6138, 2004. Vestin, A., Rissler, J., Swietlicki, E., Frank, G. P., and Andreae, M. O.: Cloud-nucleating properties of the Amazonian biomass burning aerosol: Cloud condensation nuclei measurements and modeling, J. Geophys. Res., 112, D14201, http://dx.doi.org/10.1029/2006JD008104doi:10.1029/2006JD008104, 2007. Wex, H., Hennig, T., Salma, I., Ocskay, R., Kiselev, A., Henning, S., Massling, A., Wiedensohler, A., and Stratmann, F.: Hygroscopic growth and measured and modeled critical super-saturations of an atmospheric HULIS sample, Geophys. Res. Lett., 34, L02818, http://dx.doi.org/10.1029/2006GL028260doi:10.1029/2006GL028260, 2007. Wex, H., Petters, M. D., Carrico, C. M., Hallbauer, E., Massling, A., McMeeking, G. R., Poulain, L., Wu, Z., Kreidenweis, S. M., and Stratmann, F.: Towards closing the gap between hygroscopic growth and activation for secondary organic aerosol: Part 1 – Evidence from measurements, Atmos. Chem. Phys., 9, 3987–3997, http://dx.doi.org/10.5194/acp-9-3987-2009doi:10.5194/acp-9-3987-2009, 2009. Wex, H., Fuentes, E., Tsagkogeorgas, G., Voigtlnder, J., Clauss, T., Kiselev, A., Green, D., Coe, H., McFiggans, G., and Stratmann, F.: The in?uence of algal exudate on the hygroscopicity of sea spray particles, Advances in Meteorology, 2010, 365131, http://dx.doi.org/10.1155/2010/365131doi:10.1155/2010/365131, 2010.