ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-11-11069-2011 Secondary organic aerosol formation in cloud droplets and aqueous particles (aqSOA): a review of laboratory, field and model studies Ervens B. 1 2 Turpin B. J. 3 Weber R. J. 4 CIRES, University of Colorado, Boulder, CO, USA NOAA, ESRL/CSD Boulder, CO, USA Department of Environmental Sciences, Rutgers University, New Brunswick, NJ, USA Georgia Institute of Technology, School of Earth and Atmospheric Sciences, Atlanta, GA, USA 09 11 2011 11 21 11069 11102 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/11/11069/2011/acp-11-11069-2011.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/11/11069/2011/acp-11-11069-2011.pdf

Progress has been made over the past decade in predicting secondary organic aerosol (SOA) mass in the atmosphere using vapor pressure-driven partitioning, which implies that SOA compounds are formed in the gas phase and then partition to an organic phase (gasSOA). However, discrepancies in predicting organic aerosol oxidation state, size and product (molecular mass) distribution, relative humidity (RH) dependence, color, and vertical profile suggest that additional SOA sources and aging processes may be important. The formation of SOA in cloud and aerosol water (aqSOA) is not considered in these models even though water is an abundant medium for atmospheric chemistry and such chemistry can form dicarboxylic acids and "humic-like substances" (oligomers, high-molecular-weight compounds), i.e. compounds that do not have any <i>gas phase</i> sources but comprise a significant fraction of the total SOA mass. There is direct evidence from field observations and laboratory studies that organic aerosol is formed in cloud and aerosol water, contributing substantial mass to the droplet mode. <br><br> This review summarizes the current knowledge on aqueous phase organic reactions and combines evidence that points to a significant role of aqSOA formation in the atmosphere. Model studies are discussed that explore the importance of aqSOA formation and suggestions for model improvements are made based on the comprehensive set of laboratory data presented here. A first comparison is made between aqSOA and gasSOA yields and mass predictions for selected conditions. These simulations suggest that aqSOA might contribute almost as much mass as gasSOA to the SOA budget, with highest contributions from biogenic emissions of volatile organic compounds (VOC) in the presence of anthropogenic pollutants (i.e. NO<sub>x</sub>) at high relative humidity and cloudiness. Gaps in the current understanding of aqSOA processes are discussed and further studies (laboratory, field, model) are outlined to complement current data sets.

 References % vor jede Referenz Aiken, A. C., Decarlo, P. F., Kroll, J. H., Worsnop, D. R., Huffman, J. A., Docherty, K. S., Ulbrich, I. M., Mohr, C., Kimmel, J. R., Sueper, D., Sun, Y., Zhang, Q., Trimborn, A., Northway, M., Ziemann, P. J., Canagaratna, M. R., Onasch, T. B., Alfarra, M. R., Prevot, A. S. H., Dommen, J., Duplissy, J., Metzger, A., Baltensperger, U., and Jimenez, J. L.: O/C and OM/OC ratios of primary, secondary and ambient organic aerosols with high-resolution time-of-flight aerosol mass spectrometry, Environ. Sci Technol., 42, 12, 4478–4485, 2008. Altieri, K., Carlton, A. G., Lim, H., Turpin, B. J., and Seitzinger, S. P.: Evidence for oligomer formation in clouds: Reaction of isoprene oxidation products, Environ. Sci. Technol., 40,4956–4960, 2006. Altieri, K. E., Seitzinger, S. P., Carlton, A. G., Turpin, B. J., Klein, G. C., and Marshall, A. G.: Oligomers formed through in-cloud methylglyoxal reactions: Chemical composition, properties, and mechanisms investigated by ultra-high resolution FT-ICR mass spectrometry, Atmos. Environ., 42,1476–1490, 2008. Altieri, K. E., Turpin, B. J., and Seitzinger, S. P.: Oligomers, organosulfates, and nitrooxy organosulfates in rainwater identified by ultra-high resolution electrospray ionization FT-ICR mass spectrometry, Atmos. Chem. Phys., 9, 2533–2542, http://dx.doi.org/10.5194/acp-9-2533-2009doi:10.5194/acp-9-2533-2009, 2009. Anastasio, C., Faust, B. C., and Rao, C. J.: Aromatic Carbonyl Compounds as Aqueous Phase Photochemical Sources of Hydrogen Peroxide in Acidic Sulfate Aerosols, Fogs, and Clouds. 1. Non-Phenolic Methoxybenzaldehydes and Methoxyacetophenones with Reductants (Phenols), Environ. Sci. Technol., 31, 218–232, 1997. Arakaki, T. and Faust, B. C.: Sources, sinks and mechanisms of hydroxyl radical (OH) photoproduction and consumption in authentic acidic continental cloud waters from Whiteface mountain, New York: The role of the Fe($r$) ($r$ = II, III) photochemical cycle, J. Geophys. Res., 103, 3487–3504, 1998. Arellanes, C., Paulson, S. E., Fine, P. M., and Sioutas, C.: Exceeding of Henry's Law by Hydrogen Peroxide Associated with Urban Aerosols, Environ. Sci. Technol., 40, 4859–4866, http://dx.doi.org/10.1021/es0513786doi:10.1021/es0513786, 2006. Baboukas, E. D., Kanakidou, M., and Mihalopoulos, N.: Carboxylic acids in gas and particulate phase above the Atlantic Ocean, J. Geophys. Res., 105,14459–14471, 2000. Bahreini, R., Ervens, B., Middlebrook, A. M., Warneke, C., DeGouw, J. A., DeCarlo, P., Jimenez, J. L., Brock, C. A., Neuman, J. A., Ryerson, T. B., Stark, H., Atlas, E., Brioude, J., Fried, A., Holloway, J. S., Peischl, J., Richter, D., Walega, J., Weibring, P., Wollny, A. G., and Fehsenfeld, F. C.: Organic aerosol formation in urban and industrial plumes in Houston, TX, J. Geophys. Res., 114, D00F16, http://dx.doi.org/10.1029/2008JD011493doi:10.1029/2008JD011493, 2009. Barsanti, K. C. and Pankow, J. F.: Thermodynamics of the formation of atmospheric organic particulate matter by accretion reactions - Part 1: aldehydes and ketones, Atmos. Environ, 38, 4371–4382, 2004. Barsanti, K. C. and Pankow, J. F.: Thermodynamics of the formation of atmospheric organic particulate matter by accretion reactions - Part 2: Dialdehydes, methylglyoxal, and diketones, Atmos. Environ., 39, 6597–6607, 2005. Bateman, A. P., Nizkorodov, S. A., Laskin, J., and Laskin, A.: Photolytic processing of secondary organic aerosols dissolved in cloud droplets, Phys. Chem. Chem. Phys., 13, 12199–12212, 2011. Bertram, A. K., Martin, S. T., Hanna, S. J., Smith, M. L., Bodsworth, A., Chen, Q., Kuwata, M., Liu, A., You, Y., and Zorn, S. R.: Predicting the relative humidities of liquid-liquid phase separation, efflorescence, and deliquescence of mixed particles of ammonium sulfate, organic material, and water using the organic-to-sulfate mass ratio of the particle and the oxygen-to-carbon elemental ratio of the organic component, Atmos. Chem. Phys., 11, 10995–11006, doi:10.5194/acp-11-10995-2011, 2011. Blando, J. D. and Turpin, B. J.: Secondary organic aerosol formation in cloud and fog droplets: a literature evaluation of plausibilty, Atmos. Environ., 34, 1623–1632, 2000. Blando, J. D., Porcja, R. J., Li, T., Bowman, D., Lioy, P. J., and Turpin, B. J.: Secondary Formation and the Smoky Mountain Organic Aerosol: An Examination of Aerosol Polarity and Functional Group Composition During SEAVS, Environ. Sci. Technol, 32, 604–613, 1998. Buxton, G. V., Malone, T. N., and Salmon, G. A.: Oxidation of glyoxal initiated by OH in oxygenated aqueous solutions, J. Chem. Soc. Faraday Trans., 93, 2889–2891, 1997. Cappa, C., Che, D., Kessler, S., Kroll, J., and Wilson, K.: Variations in organic aerosol optical and hygroscopic properties upon heterogeneous OH oxidation, J. Geophys. Res., 116, D15204, http://dx.doi.org/10.1029/2011jd015918doi:10.1029/2011jd015918, 2011. Carbone, C., Decesari, S., Mircea, M., Giulianelli, L., Finessi, E., Rinaldi, M., Fuzzi, S., Marinoni, A., Duchi, R., Perrino, C., Sargolini, T., Vardè, M., Sprovieri, F., Gobbi, G. P., Angelini, F., and Facchini, M. C.: Size-resolved aerosol chemical composition over the Italian Peninsula during typical summer and winter conditions, Atmos. Environ., 44, 5269–5278, http://dx.doi.org/10.1016/j.atmosenv.2010.08.008doi:10.1016/j.atmosenv.2010.08.008, 2010. Carlton, A. G., Turpin, B. J., Lim, H., Altieri, K. E., and Seitzinger, S.: Link between isoprene and secondary organic aerosol (SOA): Pyruvic acid oxidation yields low volatility organic acid in clouds, Geophys. Res. Lett., 33, 06822, http://dx.doi.org/10.1029/2005GL025374doi:10.1029/2005GL025374, 2006. Carlton, A. G., Turpin, B. J., Altieri, K. E., Reff, A., Seitzinger, S., Lim, H., and Ervens, B.: Atmospheric oxalic acid and SOA production from glyoxal: Results of aqueous photooxidation experiments, Atmos. Environ., 41, 7588–7602, 2007. Carlton, A. G., Turpin, B. J., Altieri, K. E., Seitzinger, S. P., Mathur, R., Roselle, S. J., and Weber, R. J.: CMAQ Model Performance Enhanced When In-Cloud Secondary Organic Aerosol is Included: Comparisons of Organic Carbon Predictions with Measurements, Environ. Sci. Technol., 42, 8789–8802, 2008. Carlton, A. G., Pinder, R. W., Bhave, P. V., and Pouliot, G. A.: To What Extent Can Biogenic SOA be Controlled?, Environ. Sci. Technol., 44, 3376–3380, http://dx.doi.org/10.1021/es903506bdoi:10.1021/es903506b, 2010. Casale, M. T., Richman, A. R., Elrod, M. J., Garland, R. M., Beaver, M. R., and Tolbert, M. A.: Kinetics of acid-catalyzed aldol condensation reactions of aliphatic aldehydes, Atmos. Environ., 41, 6212–6224, 2007. Chang, J. L. and Thompson, J. E.: Characterization of colored products formed during irradiation of aqueous solutions containing H<sub>2</sub>O<sub>2</sub> and phenolic compounds, Atmos. Environ., 44, 541–551, http://dx.doi.org/10.1016/j.atmosenv.2009.10.042doi:10.1016/j.atmosenv.2009.10.042, 2010. Chang, W. L., Griffin, R. J., and Dabdub, D.: Partitioning phase preference for secondary organic aerosol in an urban atmosphere, P. Natl. Acad. Sci., 107, 6705–6710, http://dx.doi.org/10.1073/pnas.0911244107doi:10.1073/pnas.0911244107, 2010. Chen, J., Griffin, R. J., Grini, A., and Tulet, P.: Modeling secondary organic aerosol formation through cloud processing of organic compounds, Atmos. Chem. Phys., 7, 5343–5355, http://dx.doi.org/10.5194/acp-7-5343-2007doi:10.5194/acp-7-5343-2007, 2007. Chen, Z. M., Wang, H. L., Zhu, L. H., Wang, C. X., Jie, C. Y., and Hua, W.: Aqueous-phase ozonolysis of methacrolein and methyl vinyl ketone: a potentially important source of atmospheric aqueous oxidants, Atmos. Chem. Phys., 8, 2255–2265, http://dx.doi.org/10.5194/acp-8-2255-2008doi:10.5194/acp-8-2255-2008, 2008. Cocker III, D. R., Clegg, S. L., Flagan, R. L., and Seinfeld, J. H.: The effect of water on gas-particle partitioning of secondary organic aerosol. Part I: a-pinene/ozone system, Atmos. Environ., 35, 6049–6072, 2001a. Cocker III, D. R., Mader, B. T., Kalberer, M., Flagan, R. L., and Seinfeld, J. H.: The effect of water on gas-particle partitioning of secondary organic aerosol. Part II: m-xylene and 1,3,5-trimethyl benzene photoxidation systems, Atmos. Environ., 35, 6073–6085, 2001b. Compernolle, S., Ceulemans, K., and Müller, J.-F.: EVAPORATION: a new vapour pressure estimation methodfor organic molecules including non-additivity and intramolecular interactions, Atmos. Chem. Phys., 11, 9431–9450, http://dx.doi.org/10.5194/acp-11-9431-2011doi:10.5194/acp-11-9431-2011, 2011. Couvidat, F. and Seigneur, C.: Modeling secondary organic aerosol formation from isoprene oxidation under dry and humid conditions, Atmos. Chem. Phys., 11, 893–909, http://dx.doi.org/10.5194/acp-11-893-2011doi:10.5194/acp-11-893-2011, 2011. Crahan, K. K., Hegg, D., Covert, D. S., and Jonsson, H.: An exploration of aqueous oxalic acid production in the coastal marine atmosphere, Atmos. Environ., 38, 3757–3764, 2004. Creighton, D. J., Migliorini, M., Pourmotabbed, T., and Guha, M. K.: Optimization of efficieny in the glyoxylase pathway, Biochem., 27, 7376–7384, 1988. Day, M. C. and Pandis, S. N.: Predicted changes in summertime organic aerosol concentrations due to increased temperatures, Atmos. Environ., 45, 6546–6556, http://dx.doi.org/10.1016/j.atmosenv.2011.08.028doi:10.1016/j.atmosenv.2011.08.028, 2011. De Haan, D. O., Corrigan, A. L., Smith, K. W., Stroik, D. R., Turley, J. J., Lee, F. E., Tolbert, M. A., Jimenez, J. L., Cordova, K. E., and Ferrell, G. R.: Secondary organic aerosol-forming reactions of glyoxal with amino acids, Environ. Sci. Technol., 43, 2818–2824, 2009a. De Haan, D. O., Corrigan, A. L., Tolbert, M. A., Jimenez, J. L., Wood, S. E., and Turley, J. J.: Secondary Organic Aerosol Formation by Self-Reactions of Methylglyoxal and Glyoxal in Evaporating Droplets, Environ. Sci Technol., 43, 8184–8190, http://dx.doi.org/10.1021/es902152tdoi:10.1021/es902152t, 2009b. De Haan, D. O., Tolbert, M. A., and Jimenez, J. L.: Atmospheric condensed phase reactions of glyoxal with methylamine, Geophys. Res. Lett., 36, L11819, http://dx.doi.org/10.1029/2009GL037441doi:10.1029/2009GL037441, 2009c. De Haan, D. O., Hawkins, L. N., Kononenko, J. A., Turley, J. J., Corrigan, A. L., Tolbert, M. A., and Jimenez, J. L.: Formation of Nitrogen-Containing Oligomers by Methylglyoxal and Amines in Simulated Evaporating Cloud Droplets, Environ. Sci. Tech., 45, 984–991, http://dx.doi.org/10.1021/es102933xdoi:10.1021/es102933x, 2010. Debus, H.: Ãœber die Einwirkung des Ammoniaks auf Glyoxal, Annalen der Chemie und Pharmacie, 107, 199–208, http://dx.doi.org/10.1002/jlac.18581070209doi:10.1002/jlac.18581070209, 1858. DeGouw, J. A., Middlebrook, A. M., Warneke, C., Goldan, P. D., Kuster, W. C., Roberts, J. M., Fehsenfeld, F. C., Worsnop, D. R., Canagaratna, M. R., Pszenny, A. A. P., Keene, W. C., Marchewka, M., Bertram, S. B., and Bates, T. S.: Budget of organic carbon in a polluted atmosphere: Results from the New England Air Quality Study in 2002, J. Geophys. Res., 110, D16305, http://dx.doi.org/10.1029/2004JD005623doi:10.1029/2004JD005623, 2005. Dixon, R. W. and Aasen, H.: Measurement of hydroxymethanesulfonate in atmospheric aerosols, Atmos. Environ., 33, 2023–2029, 1999. Donahue, N. M., Robinson, A. L., Stanier, C. O., and Pandis, S. N.: Coupled partitioning, dilution and chemical aging of semivolatile organics, Environ. Sci. Technol., 40, 2635–2643, 2006. Edney, E. O., Kleindienst, T. E., Jaoui, M., Lewandowski, M., Offenberg, J. H., Wang, W., and Claeys, M.: Formation of 2-methyl tetrols and 2-methylglyceric acid in secondary organic aerosol from laboratory irradiated isoprene/NO<sub>x</sub>/SO<sub>2</sub>/air mixtures and their detection in ambient PM$_2.5$ samples collected in the eastern United States, Atmos. Environ., 39, 5281–5289, 2005. El Haddad, I., Yao Liu, Nieto-Gligorovski, L., Michaud, V., Temime-Roussel, B., Quivet, E., Marchand, N., Sellegri, K., and Monod, A.: In-cloud processes of methacrolein under simulated conditions – Part 2: Formation of secondary organic aerosol, Atmos. Chem. Phys., 9, 5107–5117, http://dx.doi.org/10.5194/acp-9-5107-2009doi:10.5194/acp-9-5107-2009, 2009. Ervens, B. and Volkamer, R.: Glyoxal processing by aerosol multiphase chemistry: towards a kinetic modeling framework of secondary organic aerosol formation in aqueous particles, Atmos. Chem. Phys., 10, 8219–8244, http://dx.doi.org/10.5194/acp-10-8219-2010doi:10.5194/acp-10-8219-2010, 2010. Ervens, B., George, C., Williams, J. E., Buxton, G. V., Salmon, G. A., Bydder, M., Wilkinson, F., Dentener, F., Mirabel, P., Wolke, R., and Herrmann, H.: CAPRAM2.4 (MODAC mechanism): An extended and condensed tropospheric aqueous phase mechanism and its application, J. Geophys. Res., 108, 4426, http://dx.doi.org/10.1029/2002JD002202doi:10.1029/2002JD002202, 2003a. Ervens, B., Gligorovski, S., and Herrmann, H.: Temperature dependent rate constants for hydroxyl radical reactions with organic compounds in aqueous solution, Phys. Chem. Chem. Phys., 5, 1811–1824, 2003b. Ervens, B., Feingold, G., Frost, G. J., and Kreidenweis, S. M.: A modeling study of aqueous production of dicarboxylic acids, 1. Chemical pathways and speciated organic mass production, J. Geophys. Res., 109, D15205, http://dx.doi.org/10.1029/2003JD004387doi:10.1029/2003JD004387, 2004. Ervens, B., Feingold, G., and Kreidenweis, S. M.: The influence of water-soluble organic carbon on cloud drop number concentration, J. Geophys. Res., 110, D18211, http://dx.doi.org/10.1029/2004JD005634doi:10.1029/2004JD005634, 2005. Ervens, B. and Kreidenweis, S. M.: SOA formation by biogenic and carbonyl compounds: Data evaluation and application, Environ. Sci. Technol., 41, 3904–3910, 2007. Ervens, B., Carlton, A. G., Turpin, B. J., Altieri, K. E., Kreidenweis, S. M., and Feingold, G.: Secondary organic aerosol yields from cloud-processing of isoprene oxidation products, Geophys. Res. Lett., 35, L02816, http://dx.doi.org/10.1029/2007gl031828doi:10.1029/2007gl031828, 2008. Ervens, B., Cubison, M. J., Andrews, E., Feingold, G., Ogren, J. A., Jimenez, J. L., Quinn, P. K., Bates, T. S., Wang, J., Zhang, Q., Coe, H., Flynn, M., and Allan, J. D.: CCN predictions using simplified assumptions of organic aerosol composition and mixing state: a synthesis from six different locations, Atmos. Chem. Phys., 10, 4795–4807, http://dx.doi.org/10.5194/acp-10-4795-2010doi:10.5194/acp-10-4795-2010, 2010. Fast, J. D., de Foy, B., Acevedo Rosas, F., Caetano, E., Carmichael, G., Emmons, L., McKenna, D., Mena, M., Skamarock, W., Tie, X., Coulter, R. L., Barnard, J. C., Wiedinmyer, C., and Madronich, S.: A meteorological overview of the MILAGRO field campaigns, Atmos. Chem. Phys., 7, 2233–2257, http://dx.doi.org/10.5194/acp-7-2233-2007doi:10.5194/acp-7-2233-2007, 2007. Favez, O., Sciare, J., Cachier, H., Alfaro, S. C., and Abdelwahab, M. M.: Significant formation of water-insoluble secondary organic aerosols in semi-arid urban environment, Geophys. Res. Lett., 35, L15801, http://dx.doi.org/10.1029/2008gl034446doi:10.1029/2008gl034446, 2008. Feingold, G.: Modeling of the first indirect effect: Analysis of measurement requirements, Geophys. Res. Lett., 30, 1997, http://dx.doi.org/10.1029/2003GL017967doi:10.1029/2003GL017967, 2003. Feingold, G. and Kreidenweis, S.: Does cloud processing of aerosol enhance droplet concentrations?, J. Geophys. Res., 105, 24351–24361, 2000. Fillo, J. D., Koehler, C. A., Nguyen, T. P., DeHaan, D. O., Gilbert, B. A., and Flinn, K. P.: Simulating Secondary Organic Aerosol Activation by Condensation of Multiple Organics on Seed Particles, Environ. Sci. Technol., 37, 4672–4677, 2003. Froyd, K. D., Murphy, S. M., Murphy, D. M., deGouw, J. A., Eddingsaas, N. C., and Wennberg, P. O.: Contribution of isoprene-derived organosulfates to free tropospheric aerosol mass, P. Natl. Acad. Sci., 108, 21360–21365, http://dx.doi.org/10.1073/pnas.1012561107doi:10.1073/pnas.1012561107, 2010. Fu, T., Jacob, D. J., Wittrock, F., Burrows, J. P., Vrekoussis, M., and Henze, D. K.: Global budgets of atmospheric glyoxal, methylglyoxal, and implications for formation of secondary organic aerosol, J. Geophys. Res., 113, D15303, http://dx.doi.org/10.1029/2007JD009505doi:10.1029/2007JD009505, 2008. Fu, T., Jacob, D. J., and Heald, C. L.: Aqueous-phase reactive uptake of dicarbonyls as a source of organic aerosol over eastern North America, Atmos. Environ., 43, 1814–1822, 2009. Furukawa, T. and Takahashi, Y.: Oxalate metal complexes in aerosol particles: implications for the hygroscopicity of oxalate-containing particles, Atmos. Chem. Phys., 11, 4289–4301, http://dx.doi.org/10.5194/acp-11-4289-2011doi:10.5194/acp-11-4289-2011, 2011. Fuzzi, S., Decesari, S., Facchini, M. C., Matta, E., Mircea, M., and Tagliavini, E.: A simplified model of the water soluble organic component of atmospheric aerosol, Geophys. Res. Lett., 28, 4079–4082, 2001. Fuzzi, S., Facchini, M. C., Decesari, S., Matta, E., and Mircea, M.: Soluble organic compounds in fog and cloud droplets: What have we learned over the past few years?, Atmos. Res., 64, 89–98, 2002. Galloway, M. M., Chhabra, P. S., Chan, A. W. H., Surratt, J. D., Flagan, R. C., Seinfeld, J. H., and Keutsch, F. N.: Glyoxal uptake on ammonium sulphate seed aerosol: reaction products and reversibility of uptake under dark and irradiated conditions, Atmos. Chem. Phys., 9, 3331–3345, http://dx.doi.org/10.5194/acp-9-3331-2009doi:10.5194/acp-9-3331-2009, 2009. Galloway, M. M., Huisman, A. J., Yee, L. D., Chan, A. W. H., Loza, C. L., Seinfeld, J. H., and Keutsch, F. N.: Yields of oxidized volatile organic compounds during the OH radical initiated oxidation of isoprene, methyl vinyl ketone, and methacrolein under high–NO<sub>x</sub> conditions, Atmos. Chem. Phys. Discuss., 11, 10693–10720, http://dx.doi.org/10.5194/acpd-11-10693-2011doi:10.5194/acpd-11-10693-2011, 2011a. Galloway, M. M., Loza, C. L., Chhabra, P. S., Chan, A. W. H., Yee, L. D., Seinfeld, J. H., and Keutsch, F. N.: Analysis of photochemical and dark glyoxal uptake: Implications for SOA formation, Geophys. Res. Lett., 38, L17811, http://dx.doi.org/10.1029/2011gl048514doi:10.1029/2011gl048514, 2011b. Gelencser, A., Hoffer, A., Kiss, G., Tombasz, E., Kurdi, R., and Bencze, L.: In-situ formation of Light-Absorbing Organic Matter in Cloud Water, J. Atmos. Chem., 45, 25–33, 2003. Graber, E. R. and Rudich, Y.: Atmospheric HULIS: How humic-like are they? A comprehensive and critical review, Atmos. Chem. Phys., 6, 729–753, http://dx.doi.org/10.5194/acp-6-729-2006doi:10.5194/acp-6-729-2006, 2006. Graedel, T. E. and Weschler, C. J.: Chemistry Within Aqueous Atmospheric Aerosols and Raindrops, Rev. Geophys. Space Phys., 19, 505–539, 1981. Grgic, I., Nieto-Gligorovski, L. I., Net, S., Temime-Roussel, B., Gligorovski, S., and Wortham, H.: Light induced multiphase chemistry of gas-phase ozone on aqueous pyruvic and oxalic acids, Phys. Chem. Chem. Phys., 12, 698–707, 2010. Griffin, R. J., Nguyen, K., Dabdub, D., and Seinfeld, J. H.: A coupled Hydrophobic-Hydrophilic Model for Predicting Secondary Aerosol Formation, J. Atmos. Chem., 44, 171–190, 2003. Guzman, M. I., Colussi, A. J., and Hoffmann, M. R.: Photoinduced oligomerization of aqueous pyruvic acid, J. Phys. Chem. A, 110, 3619–3626, 2006. Hasson, A. S. and Paulson, S. E.: An investigation of the relationship between gas-phase and aerosol borne hydroperoxides in urban air, J. Aerosol Sci., 34, 459–468, 2003. Hatch, L. E., Creamean, J. M., Ault, A. P., Surratt, J. D., Chan, M. N., Seinfeld, J. H., Edgerton, E. S., Su, Y., and Prather, K. A.: Measurements of Isoprene-Derived Organosulfates in Ambient Aerosols by Aerosol Time-of-Flight Mass Spectrometry – Part 1: Single Particle Atmospheric Observations in Atlanta, Environ. Sci. Technol., 45, 5105–5111, http://dx.doi.org/10.1021/es103944adoi:10.1021/es103944a, 2011. Heald, C. L., Jacob, D. J., Park, R. J., Russell, L. M., Huebert, B. J., Seinfeld, J. H., Liao, H., and Weber, R. J.: A large organic aerosol source in the free troposphere missing from current models, Geophys. Res. Lett., 32, L18809, http://dx.doi.org/10.1029/2005GL023831doi:10.1029/2005GL023831, 2005. Heald, C. L., Jacob, D. J., Turquety, S., Hudman, R. C., Weber, R. J., Sullivan, A. P., Peltier, R. E., Atlas, E. L., deGouw, J. A., Warneke, C., Holloway, J. S., Newman, J. A., Flocke, F. M., and Seinfeld, J. H.: Concentrations and sources of organic carbon aerosols in the free troposphere over North America, J. Geophys. Res., 111, D23S47, http://dx.doi.org/10.1029/2006JD007705doi:10.1029/2006JD007705, 2006. Heald, C. L., Coe, H., Jimenez, J. L., Weber, R. J., Bahreini, R., Middlebrook, A. M., Russell, L. M., Jolleys, M., Fu, T.-M., Allan, J. D., Bower, K. N., Capes, G., Crosier, J., Morgan, W. T., Robinson, N. H., Williams, P. I., Cubison, M. J., DeCarlo, P. F., and Dunlea, E. J.: Exploring the vertical profile of atmospheric organic aerosol: comparing 17 aircraft field campaigns with a global model, Atmos. Chem. Phys. Discuss., 11, 25371–25425, http://dx.doi.org/10.5194/acpd-11-25371-2011doi:10.5194/acpd-11-25371-2011, 2011. Healy, R. M., Wenger, J. C., Metzger, A., Duplissy, J., Kalberer, M., and Dommen, J.: Gas/particle partitioning of carbonyls in the photooxidation of isoprene and 1,3,5-trimethylbenzene, Atmos. Chem. Phys., 8, 3215–3230, http://dx.doi.org/10.5194/acp-8-3215-2008doi:10.5194/acp-8-3215-2008, 2008. Healy, R. M., Temime, B., Kuprovskyte, K., and Wenger, J. C.: Effect of Relative Humidity on Gas/Particle Partitioning and Aerosol Mass Yield in the Photooxidation of p-Xylene, Environ. Sci. Tech., 43, 1884–1889, http://dx.doi.org/10.1021/es802404zdoi:10.1021/es802404z, 2009. Hecobian, A., Zhang, X., Zheng, M., Frank, N., Edgerton, E. S., and Weber, R. J.: Water-Soluble Organic Aerosol material and the light-absorption characteristics of aqueous extracts measured over the Southeastern United States, Atmos. Chem. Phys., 10, 5965–5977, http://dx.doi.org/10.5194/acp-10-5965-2010doi:10.5194/acp-10-5965-2010, 2010. Hennigan, C. J., Sullivan, A. P., Fountoukis, C. I., Nenes, A., Hecobian, A., Vargas, O., Peltier, R. E., Case Hanks, A. T., Huey, L. G., Lefer, B. L., Russell, A. G., and Weber, R. J.: On the volatility and production mechanisms of newly formed nitrate and water soluble organic aerosol in Mexico City, Atmos. Chem. Phys., 8, 3761–3768, http://dx.doi.org/10.5194/acp-8-3761-2008doi:10.5194/acp-8-3761-2008, 2008a. Hennigan, C. J., Bergin, M. H., Dibb, J. E., and Weber, R. J.: Enhanced secondary organic aerosol formation due to water uptake by fine particles, Geophys. Res. Lett, 35, L18801, http://dx.doi.org/10.1029/2008GL035046doi:10.1029/2008GL035046, 2008b. Hennigan, C. J., Bergin, M. H., and Weber, R. J.: Correlations between water-soluble organic aerosol and water vapor: a synergistic effect from biogenic emissions?, Environ. Sci Technol., 42, 9079–9085, 2008c. Hennigan, C. J., Bergin, M. H., Russell, A. G., Nenes, A., and Weber, R. J.: Gas/particle partitioning of water-soluble organic aerosol in Atlanta, Atmos. Chem. Phys., 9, 3613–3628, http://dx.doi.org/10.5194/acp-9-3613-2009doi:10.5194/acp-9-3613-2009, 2009. Henze, D. K. and Seinfeld, J. H.: Global secondary organic aerosol from isoprene oxidation, Geophys. Res. Lett., 33, L09812, http://dx.doi.org/10.1029/2006GL025976doi:10.1029/2006GL025976, 2006. Herckes, P., Lee, T., Trenary, L., Kang, G., Chang, H., and Collett, J. L.: Organic Matter in Central California Radiation Fogs, Environ. Sci. Technol., 36, 4777–4782, http://dx.doi.org/10.1021/es025889tdoi:10.1021/es025889t, 2002. Herckes, P., Chang, H., Lee, T., and Collett Jr., J. L.: Air pollution processing by radiation fogs, Water Air Soil Pollut., 181, 65–75, 2007. Hering, S. V. and Friedlander, S. K.: Origins of Sulfur Size Distributions in the Los Angeles Basin, Atmos. Environ., 16, 2647–2656, 1982. Herrmann, H.: Kinetics of aqueous phase reactions relevant for atmospheric chemistry, Chem. Rev., 103, 4691–4716, 2003. Herrmann, H., Ervens, B., Jacobi, H.-W., Wolke, R., Nowacki, P., and Zellner, R.: CAPRAM2.3: A Chemical Aqueous Phase Radical Mechanism for Tropospheric Chemistry, J. Atmos. Chem., 36, 231–284, 2000. Herrmann, H., Tilgner, A., Barzaghi, P., Majdik, Z., Gligorovski, S., Poulain, L., and Monod, A.: Towards a more detailed description of tropospheric aqueous phase organic chemistry: CAPRAM 3.0, Atmos. Environ, 39, 4351–4363, 2005. Herrmann, H., Hoffmann, D., Schaefer, T., Bräuer, P., and Tilgner, A.: Tropospheric Aqueous-Phase Free-Radical Chemistry: Radical Sources, Spectra, Reaction Kinetics and Prediction Tools, Chem. Phys. Chem., 11, 3796–3822, http://dx.doi.org/10.1002/cphc.201000533doi:10.1002/cphc.201000533, 2010. Hersey, S. P., Craven, J. S., Schilling, K. A., Metcalf, A. R., Sorooshian, A., Chan, M. N., Flagan, R. C., and Seinfeld, J. H.: The Pasadena Aerosol Characterization Observatory (PACO): chemical and physical analysis of the Western Los Angeles basin aerosol, Atmos. Chem. Phys., 11, 7417–7443, http://dx.doi.org/10.5194/acp-11-7417-2011doi:10.5194/acp-11-7417-2011, 2011. Hodzic, A., Jimenez, J. L., Madronich, S., Canagaratna, M. R., DeCarlo, P. F., Kleinman, L., and Fast, J.: Modeling organic aerosols in a megacity: potential contribution of semi-volatile and intermediate volatility primary organic compounds to secondary organic aerosol formation, Atmos. Chem. Phys., 10, 5491–5514, http://dx.doi.org/10.5194/acp-10-5491-2010doi:10.5194/acp-10-5491-2010, 2010. Hoffer, A., Kiss, G., Blazsó, M., and Gelencsér, A.: Chemical characterization of humic-like substances (HULIS) formed from a lignin-type precursor in model cloud water, Geophys. Res. Lett., 31, L06115, http://dx.doi.org/10.1029/2003gl018962doi:10.1029/2003gl018962, 2004. Hoppel, W. A., Frick, G. M., Fitzgerald, J. W., and Larson, R. E.: Marine Boundary layer measurements of new particle formation and the effects nonprecipitating clouds have on aerosol size distribution, J. Geophys. Res., 99, 14443–14459, 1994. Hoyle, C. R., Boy, M., Donahue, N. M., Fry, J. L., Glasius, M., Guenther, A., Hallar, A. G., Huff Hartz, K., Petters, M. D., Petäjä, T., Rosenoern, T., and Sullivan, A. P.: A review of the anthropogenic influence on biogenic secondary organic aerosol, Atmos. Chem. Phys., 11, 321–343, http://dx.doi.org/10.5194/acp-11-321-2011doi:10.5194/acp-11-321-2011, 2011. Huang, D., Zhang, X., Chen, Z. M., Zhao, Y., and Shen, X. L.: The kinetics and mechanism of an aqueous phase isoprene reaction with hydroxyl radical, Atmos. Chem. Phys., 11, 7399–7415, http://dx.doi.org/10.5194/acp-11-7399-2011doi:10.5194/acp-11-7399-2011, 2011. Huang, X.-F., Yu, J. Z., He, L.-Y., and Yuan, Z.: Water-soluble organic carbon and oxalate in aerosols at a coastal urban site in China: Size distribution characteristics, sources, and formation mechanisms, J. Geophys. Res., 111, D22212, http://dx.doi.org/10.1029/2006jd007408doi:10.1029/2006jd007408, 2006. Huang, X. H. H., Ip, H. S. S., and Yu, J. Z.: Secondary organic aerosol formation from ethylene in the urban atmosphere of Hong Kong: A multiphase chemical modeling study, J. Geophys. Res., 116, D03206, http://dx.doi.org/10.1029/2010jd014121doi:10.1029/2010jd014121, 2011. Igawa, M., Munger, J. W., and Hoffmann, M. R.: Analysis of aldehydes in cloud- and fogwater samples by HPLC with a postcolumn reaction detector, Environ. Sci. Technol, 23, 556–561, 1989. Ip, H. S. S., Huang, X. H. H., and Yu, J. Z.: Effective Henry's law constants of glyoxal, glyoxylic acid and glycolic acid, Geophys. Res. Lett., 36, L01802, http://dx.doi.org/10.1029/2008GL036212doi:10.1029/2008GL036212, 2009. Iraci, L. T., Baker, B. M., Tyndall, G. S., and Orlando, J. J.: Measurements of the Henry's Law Coefficients of 2-Methyl-3-buten-2-ol, Methacrolein, and Methylvinyl Ketone, J. Atmos. Chem., 33, 321–330, 1999. Jacobson, M.: Isolating nitrated and aromatic aerosols and nitrated aromatic gases as sources of ultraviolet light absorption, J. Geophys. Res., 104, 3527–3542, 1999. Jaoui, M., Edney, E. O., Kleindienst, T. E., Lewandowski, M., Offenberg, J. H., Surratt, J. D., and Seinfeld, J. H.: Formation of secondary organic aerosol from irradiated $\alpha $-pinene/toluene/NOx mixtures and the effect of isoprene and sulfur dioxide, J. Geophys. Res., 113, D09303, http://dx.doi.org/10.1029/2007jd009426doi:10.1029/2007jd009426, 2008. Jathar, S. H., Farina, S. C., Robinson, A. L., and Adams, P. J.: The influence of semi-volatile and reactive primary emissions on the abundance and properties of global organic aerosol, Atmos. Chem. Phys., 11, 7727–7746, http://dx.doi.org/10.5194/acp-11-7727-2011doi:10.5194/acp-11-7727-2011, 2011. Jimenez, J. L., Canagaratna, M. R., Donahue, N. M., Prevot, A. S. H., 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, 5959, 1525–1529, http://dx.doi.org/10.1126/science.1180353doi:10.1126/science.1180353, 2009. John, W., Wall, S. M., Ondo, J. L., and Winklmayr, W.: Modes in the size distributions of atmospheric inorganic aerosol, Atmos. Environ. A, 24, 2349–2359, http://dx.doi.org/10.1016/0960-1686(90)90327-jdoi:10.1016/0960-1686(90)90327-j, 1990. Jung, J. and Kawamura, K.: Enhanced concentrations of citric acid in spring aerosols collected at the Gosan background site in East Asia, Atmos. Environ., 45, 5266-5272, http://dx.doi.org/10.1016/j.atmosenv.2011.06.065doi:10.1016/j.atmosenv.2011.06.065, 2011. Kanakidou, M., Seinfeld, J. H., Pandis, S. N., Barnes, I., Dentener, F. J., Facchini, M. C., Van Dingenen, R., Ervens, B., Nenes, A., Nielsen, C. J., Swietlicki, E., Putaud, J. P., Balkanski, Y., Fuzzi, S., Horth, J., Moortgat, G. K., Winterhalter, R., Myhre, C. E. L., Tsigaridis, K., Vignati, E., Stephanou, E. G., and Wilson, J.: Organic aerosol and global climate modelling: a review, Atmos. Chem. Phys., 5, 1053–1123, http://dx.doi.org/10.5194/acp-5-1053-2005doi:10.5194/acp-5-1053-2005, 2005. Karpel Vel Leitner, N., and Doré, M.: Mecanisme d'action des radicaux OH sur les acides glycolique, glyoxylique, acetique et oxalique en solution aqueuse: Incidence sur la consammation de peroxyde d'hydrogene dans les systemes H<sub>2</sub>O<sub>2</sub>/UV et O<sub>3</sub>/H<sub>2</sub>O<sub>2</sub> (Mechanism of the reaction between hydroxyl radicals and glycolic, glyoxylic, acetic and oxalic acids in aqueous solution: Consequence on hydrogen peroxide consumption in the H<sub>2</sub>O<sub>2</sub>/UV and O<sub>3</sub>/H<sub>2</sub>O<sub>2</sub> systems), Water Research, 31, 1383–1397, 1997. Kaul, D. S., Gupta, T., Tripathi, S. N., Tare, V., and Collett, J. L.: Secondary Organic Aerosol: A Comparison between Foggy and Nonfoggy Days, Environ. Sci. Technol., 45, 7307–7313, http://dx.doi.org/10.1021/es201081ddoi:10.1021/es201081d, 2011. Kawamura, K. and Kaplan, I. R.: Motor Exhaust Emissions as Primary Source for Dicarboxylic Acids in Los Angeles Ambient Air, Environ. Sci. Technol, 21, 105–110, 1987. Kawamura, K., Kasukabe, H., and Barrie, L. A.: Source and reaction pathways of dicarboxylic acids, ketoacids and dicarbonyls in Arctic aerosols: One year of observations, Atmos. Environ., 30, 1709–1722, 1996a. Kawamura, K., Steinberg, S., and Kaplan, I. R.: Concentrations of monocarboxylic and dicarboxylic acids and aldehydes in Southern California wet precipitations: comparison of urban and non-urban samples and compositional changes during scavenging, Atmos. Environ., 30, 1035–1052, 1996b. Kawamura, K. and Sakaguchi, F.: Molecular distributions of water soluble dicarboxylic acids in marine aerosols over the Pacific Ocean including tropics, J. Geophys. Res., 104, 3501–3509, 1999. Kawamura, K., Steinberg, S., and Kaplan, I. R.: Homologous series of C$_1$-C$_10$ monocarboxylic acids and C$_1$-C$_6$ carbonyls in Los Angeles air and motor vehicle exhausts, Atmos. Environ., 34, 4175–4191, 2000. Kawamura, K., Umemoto, N., Mochida, M., Bertram, T., Howell, S., and Huebert, B. J.: Water-soluble dicarboxylic acids in the tropospheric aerosols collected over east Asia and western North Pacific by ACE-Asia C-130 aircraft, J. Geophys. Res., 108, 8639, http://dx.doi.org/10.1029/2002JD003256doi:10.1029/2002JD003256, 2003. Kawamura, K., Kasukabe, H., and Barrie, L. A.: Secondary formation of water-soluble organic acids and $\alpha $-dicarbonyls and their contributions to total carbon and water-soluble organic carbon: Photochemical aging of organic aerosols in the Arctic spring, J. Geophys. Res., 115, D21306, http://dx.doi.org/10.1029/2010jd014299doi:10.1029/2010jd014299, 2010. Kerminen, V.-M. and Wexler, A. S.: Growth laws for atmospheric aerosol particles: An examination of the bimodality of the accumulation mode, Atmos. Environ., 29, 3263–3275, http://dx.doi.org/10.1016/1352-2310(95)00249-xdoi:10.1016/1352-2310(95)00249-x, 1995. Kirchstetter, T., Novakov, T., and Hobbs, P. V.: Evidence that the spectral dependence of light absorption by aerosols is affected by organic carbon, J. Geophys. Res., 109, D21208, http://dx.doi.org/10.1029/2004JD004999doi:10.1029/2004JD004999, 2004. Kristensen, K. and Glasius, M.: Organosulfates and oxidation products from biogenic hydrocarbons in fine aerosols from a forest in North West Europe during spring, Atmos. Environ., 45, 4546–4556, http://dx.doi.org/10.1016/j.atmosenv.2011.05.063doi:10.1016/j.atmosenv.2011.05.063, 2011. Krivacsy, Z., Kiss, G., Ceburnis, D., Jennings, G., Maenhaut, W., Salma, I., and Shooter, D.: Study of water-soluble atmospheric humic matter in urban and marine environments, Atmos. Res., 87, 1–12, 2008. Krizner, H. E., DeHaan, D. O., and Kua, K.: Thermodynamics and kinetics of methylglyoxal dimer formation: A computational study, J. Phys Chem. A, 113, 25, 6994–7001, 2009. Kroll, J. H., Ng, N. L., Murphy, S. M., Flagan, R. C., and Seinfeld, J. H.: Secondary organic aerosol formation from isoprene photooxidation under high NO<sub>x</sub> conditions, Geophys. Res. Lett., 32, L18808, http://dx.doi.org/10.1029/2005GL023637doi:10.1029/2005GL023637, 2005a. Kroll, J. H., Ng, N. L., Murphy, S. M., Varutbangkul, V., Flagan, R. C., and Seinfeld, J. H.: Chamber studies of secondary organic aerosol growth by reactive uptake of simple carbonyl compounds, J. Geophys. Res., 110, D23207, http://dx.doi.org/10.1029/2005JD006004doi:10.1029/2005JD006004, 2005b. Kroll, J. H., Donahue, N. M., Jimenez, J. L., Kessler, S. H., Canagaratna, M. R., Wilson, K. R., Altieri, K. E., Mazzoleni, L. R., Wozniak, A. S., Bluhm, H., Mysak, E. R., Smith, J. D., Kolb, C. E., and Worsnop, D. R.: Carbon oxidation state as a metric for describing the chemistry of atmospheric organic aerosol, Nat. Chem., 3, 133–139, 2011. Kua, J., Hanley, S. W., and DeHaan, D. O.: Thermodynamics and kinetics of glyoxal dimer formation: A computational study, J. Phys. Chem. A, 112, 66–72, 2008. Kua, J., Krizner, H. E., and De Haan, D. O.: Thermodynamics and Kinetics of Imidazole Formation from Glyoxal, Methylamine, and Formaldehyde: A Computational Study, J. Phys. Chem. A, 115, 1667–1675, http://dx.doi.org/10.1021/jp111527xdoi:10.1021/jp111527x, 2011. Lambe, A. T., Onasch, T. B., Massoli, P., Croasdale, D. R., Wright, J. P., Ahern, A. T., Williams, L. R., Worsnop, D. R., Brune, W. H., and Davidovits, P.: Laboratory studies of the chemical composition and cloud condensation nuclei (CCN) activity of secondary organic aerosol (SOA) and oxidized primary organic aerosol (OPOA), Atmos. Chem. Phys., 11, 8913–8928, http://dx.doi.org/10.5194/acp-11-8913-2011doi:10.5194/acp-11-8913-2011, 2011. Lee-Taylor, J., Madronich, S., Aumont, B., Camredon, M., Hodzic, A., Tyndall, G. S., Apel, E., and Zaveri, R. A.: Explicit modeling of organic chemistry and secondary organic aerosol partitioning for Mexico City and its outflow plume, Atmos. Chem. Phys. Discuss., 11, 17013–17070, http://dx.doi.org/10.5194/acpd-11-17013-2011doi:10.5194/acpd-11-17013-2011, 2011. Lee, A. K. Y., Herckes, P., Leaitch, W. R., Macdonald, A. M., and Abbatt, J. P. D.: Aqueous OH oxidation of ambient organic aerosol and cloud water organics: Formation of highly oxidized products, Geophys. Res. Lett., 38, 11, L11805, http://dx.doi.org/10.1029/2011gl047439doi:10.1029/2011gl047439, 2011. Lee, S., Murphy, D. M., Thomson, D. S., and Middlebrook, A. M.: Nitrate and oxidized organic ions in single particle mass spectra during the 1999 Atlanta Supersite Project, J. Geophys. Res., 108, 8417, http://dx.doi.org/10.1029/2001JD001455doi:10.1029/2001JD001455, 2003. Li, Z., Schwier, A. N., Sareen, N., and McNeill, V. F.: Reactive processing of formaldehyde and acetaldehyde in aqueous aerosol mimics: surface tension depression and secondary organic products, Atmos. Chem. Phys. Discuss., 11, 19477–19506, http://dx.doi.org/10.5194/acpd-11-19477-2011doi:10.5194/acpd-11-19477-2011, 2011. Liggio, J., Li, S.-M., and McLaren, R.: Heterogeneous reactions of glyoxal on particulate matter: identification of acetals and sulfate esters, Environ. Sci. Technol., 39, 1532–1541, 2005a. Liggio, J., Li, S.-M., and McLaren, R.: Reactive uptake of glyoxal by particulate matter, J. Geophys. Res., 110, D10304,http://dx.doi.org/10.1029/2004JD005113doi:10.1029/2004JD005113, 2005b. Likens, G. E., Edgerton, E. S., and Galloway, J. N.: The composition and deposition of organic carbon in precipitation, Tellus B, 35B, 16–24, http://dx.doi.org/10.1111/j.1600-0889.1983.tb00003.xdoi:10.1111/j.1600-0889.1983.tb00003.x, 1983. Lim, Y. B., Tan, Y., Perri, M. J., Seitzinger, S. P., and Turpin, B. J.: Aqueous chemistry and its role in secondary organic aerosol (SOA) formation, Atmos. Chem. Phys., 10, 10521–10539, http://dx.doi.org/10.5194/acp-10-10521-2010doi:10.5194/acp-10-10521-2010, 2010. Lin, P., Engling, G., and Yu, J. Z.: Humic-like substances in fresh emissions of rice straw burning and in ambient aerosols in the Pearl River Delta Region, China, Atmos. Chem. Phys., 10, 6487–6500, http://dx.doi.org/10.5194/acp-10-6487-2010doi:10.5194/acp-10-6487-2010, 2010a. Lin, P., Huang, X.-F., He, L.-Y., and Zhen Yu, J.: Abundance and size distribution of HULIS in ambient aerosols at a rural site in South China, J. Aerosol Sci., 41, 74–87, 2010b. Liu, Y., El Haddad, I., Scarfogliero, M., Nieto-Gligorovski, L., Temime-Roussel, B., Quivet, E., Marchand, N., Picquet-Varrault, B., and Monod, A.: In-cloud processes of methacrolein under simulated conditions – Part 1: Aqueous phase photooxidation, Atmos. Chem. Phys., 9, 5093–5105, http://dx.doi.org/10.5194/acp-9-5093-2009doi:10.5194/acp-9-5093-2009, 2009. Liu, Y., Tritscher, T., Praplan, A. P., DeCarlo, P. F., Temime-Roussel, B., Quivet, E., Marchand, N., Dommen, J., Baltensperger, U., and Monod, A.: Aqueous phase processing of secondary organic aerosols, Atmos. Chem. Phys. Discuss., 11, 21489–21532, http://dx.doi.org/10.5194/acpd-11-21489-2011doi:10.5194/acpd-11-21489-2011, 2011. Marcolli, C. and Peter, Th.: Water activity in polyol/water systems: new UNIFAC parameterization, Atmos. Chem. Phys., 5, 1545–1555, http://dx.doi.org/10.5194/acp-5-1545-2005doi:10.5194/acp-5-1545-2005, 2005. Maria, S. F., L. M. Russell, M. K. Gilles, and Myeni, S. C. B.: Organic Aerosol Growth Mechanisms and Their Climate Forcing Implications, Science, 306, 1921–1924, 2004. Martin, S. T., Andreae, M. O., Althausen, D., Artaxo, P., Baars, H., Borrmann, S., Chen, Q., Farmer, D. K., Guenther, A., Gunthe, S. S., Jimenez, J. L., Karl, T., Longo, K., Manzi, A., Müller, T., Pauliquevis, T., Petters, M. D., Prenni, A. J., Pöschl, U., Rizzo, L. V., Schneider, J., Smith, J. N., Swietlicki, E., Tota, J., Wang, J., Wiedensohler, A., and Zorn, S. R.: An overview of the Amazonian Aerosol Characterization Experiment 2008 (AMAZE-08), Atmos. Chem. Phys., 10, 11415–11438, http://dx.doi.org/10.5194/acp-10-11415-2010doi:10.5194/acp-10-11415-2010, 2010. Martinelango, P. K., Dasgupta, P. K., and Al-Horr, R. S.: Atmospheric production of oxalic acid/oxalate and nitric acid/nitrate in the Tampa Bay airshed: Parallel pathways, Atmos. Environ., 41, 4258–4269, 2007. Massoli, P., Lambe, A. T., Ahern, A. T., Williams, L. R., Ehn, M., Mikkilä, J., Canagaratna, M. R., Brune, W. H., Onasch, T. B., Jayne, J. T., Petäjä, T., Kulmala, M., Laaksonen, A., Kolb, C. E., Davidovits, P., and Worsnop, D. R.: Relationship between aerosol oxidation level and hygroscopic properties of laboratory generated secondary organic aerosol (SOA) particles, Geophys. Res. Lett., 37, L24801, http://dx.doi.org/10.1029/2010gl045258doi:10.1029/2010gl045258, 2010. Mazzoleni, L. R., Ehrmann, B. M., Shen, X., Marshall, A. G., and Collett, J. L.: Water-Soluble Atmospheric Organic Matter in Fog: Exact Masses and Chemical Formula Identification by Ultrahigh-Resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry, Environ. Sci. Technol., 44, 3690–3697, http://dx.doi.org/10.1021/es903409kdoi:10.1021/es903409k, 2010. Meng, Z. and Seinfeld, J. H.: On the Source of the Submicrometer Droplet Mode of Urban and Regional Aerosols, Aerosol Sci. Technol., 20, 253–265, 1994. Meng, Z., Seinfeld, J. H., Saxena, P., and Kim, Y. P.: Contribution of Water to Particulate Mass in the South Coast Air Basin, Aerosol Sci. Technol., 22, 111–123, 1995. Michaud, V., El Haddad, I., Yao Liu, Sellegri, K., Laj, P., Villani, P., Picard, D., Marchand, N., and Monod, A.: In-cloud processes of methacrolein under simulated conditions – Part 3: Hygroscopic and volatility properties of the formed secondary organic aerosol, Atmos. Chem. Phys., 9, 5119–5130, http://dx.doi.org/10.5194/acp-9-5119-2009doi:10.5194/acp-9-5119-2009, 2009. Minakata, D., Li, K., Westerhoff, P., and Crittenden, J.: Development of a Group Contribution Method To Predict Aqueous Phase Hydroxyl Radical (HO) Reaction Rate Constants, Environ. Sci Technol., 43, 6220–6227, http://dx.doi.org/10.1021/es900956cdoi:10.1021/es900956c, 2009. Minerath, E. C. and Elrod, M. J.: Assessing the Potential for Diol and Hydroxy Sulfate Ester Formation from the Reaction of Epoxides in Tropospheric Aerosols, Environ. Sci Technol., 43, 1386–1392, http://dx.doi.org/10.1021/es8029076doi:10.1021/es8029076, 2009. Miyazaki, Y., Aggarwal, S. G., Singh, K., Gupta, P. K., and Kawamura, K.: Dicarboxylic acids and water-soluble organic carbon in aerosols in New Delhi, India, in winter: Characteristics and formation processes, J. Geophys. Res., 114, D19206, http://dx.doi.org/10.1029/2009jd011790doi:10.1029/2009jd011790, 2009a. Miyazaki, Y., Kondo, Y., Shiraiwa, M., Takegawa, N., Miyakawa, T., Han, S., Kita, K., Hu, M., Deng, Z. Q., Zhao, Y., Sugimoto, N., Blake, D. R., and Weber, R. J.: Chemical characterization of water-soluble organic carbon aerosols at a rural site in the Pearl River Delta, China, in the summer of 2006, J. Geophys. Res., 114, D14208, http://dx.doi.org/10.1029/2009jd011736doi:10.1029/2009jd011736, 2009b. Moffett, R. C., Qin, X., Rebotier, T., Furutani, H., and Prather, K. A.: Chemically segregated optical and microphysical properties of ambient aerosols measured in a single-particle mass spectrometer, J. Geophys. Res., 113, D12213, http://dx.doi.org/10.1029/2007JD009393doi:10.1029/2007JD009393, 2008. Molina, M. J., Ivanov, A. V., Trakhtenberg, S., and Molina, L. T.: Atmospheric evolution of organic aerosol, Geophys. Res. Lett., 31, L22104, http://dx.doi.org/10.1029/2004GL020910doi:10.1029/2004GL020910, 2004. Monod, A. and Doussin, J. F.: Structure-activity relationship for the estimation of OH-oxidation rate constants of aliphatic organic compounds in the aqueous phase: alkanes, alcohols, organic acids and bases, Atmos. Environ., 42, 7611–7622, http://dx.doi.org/10.1016/j.atmosenv.2008.06.005doi:10.1016/j.atmosenv.2008.06.005, 2008. Monod, A., Poulain, L., Grubert, S., Voisin, D., and Wortham, H.: Kinetics of OH-initiated oxidation of oxygenated organic compounds in the aqueous phase: new rate constants, structure-activity relationships and atmospheric implications, Atmos. Environ., 39, 7667–7688, 2005. Munger, J. W., Tiller, C., and Hoffmann, M. R.: Identification of Hydroxymethanesulfonate in Fog Water, Science, 231, 247–249, 1986. Munger, J. W., Jacob, D. J., Daube , B. C., Horowitz, L. W., Keene, W. C., and Heikes, B. C.: Formaldehyde, glyoxal and methylglyoxal at a rural mountain site in central Virginia, J. Geophys. Res., 100, 9325–9333, 1995. Murphy, B. N. and Pandis, S. N.: Simulating the Formation of Semivolatile Primary and Secondary Organic Aerosol in a Regional Chemical Transport Model, Environ. Sci Technol., 43, 4722–4728, http://dx.doi.org/10.1021/es803168adoi:10.1021/es803168a, 2009. Myriokefalitakis, S., Vrekoussis, M., Tsigaridis, K., Wittrock, F., Richter, A., Brühl, C., Volkamer, R., Burrows, J. P., and Kanakidou, M.: The influence of natural and anthropogenic secondary sources on the glyoxal global distribution, Atmos. Chem. Phys., 8, 4965–4981, http://dx.doi.org/10.5194/acp-8-4965-2008doi:10.5194/acp-8-4965-2008, 2008. Myriokefalitakis, S., Tsigaridis, K., Mihalopoulos, N., Sciare, J., Nenes, A., Kawamura, K., Segers, A., and Kanakidou, M.: In-cloud oxalate formation in the global troposphere: a 3-D modeling study, Atmos. Chem. Phys., 11, 5761–5782, http://dx.doi.org/10.5194/acp-11-5761-2011doi:10.5194/acp-11-5761-2011, 2011. Nakayama, T., Matsumi, Y., Sato, K., Imamura, T., Yamazaki, A., and Uchiyama, A.: Laboratory studies on optical properties of secondary organic aerosols generated during the photooxidation of toluene and the ozonolysis of $\alpha $-pinene, J. Geophys. Res., 115, D24204, http://dx.doi.org/10.1029/2010jd014387doi:10.1029/2010jd014387, 2010. Narukawa, M., Kawamura, K., Anlauf, K. G., and Barrie, L. A.: Fine and coarse modes of dicarboxylic acids in the Arctic aerosols collected during the Polar Sunrise Experiment 1997, J. Geophys. Res., 108, 4575, http://dx.doi.org/10.1029/2003JD003646doi:10.1029/2003JD003646, 2003. Neusüss, C., Pelzing, M., Plewka, A., and Herrmann, H.: A new analytical approach for size-resolved speciation of organic compounds in atmospheric aerosol particles: Methods and first results, J. Geophys. Res., 105, 4513–4527, http://dx.doi.org/10.1029/1999jd901038doi:10.1029/1999jd901038, 2000. Ng, N. L., Kroll, J. H., Chan, A. W. H., Chhabra, P. S., Flagan, R. C., and Seinfeld, J. H.: Secondary organic aerosol formation from m-xylene, toluene, and benzene, Atmos. Chem. Phys., 7, 3909–3922, http://dx.doi.org/10.5194/acp-7-3909-2007doi:10.5194/acp-7-3909-2007, 2007. Ng, N. L., Canagaratna, M. R., Zhang, Q., Jimenez, J. L., Tian, J., Ulbrich, I. M., Kroll, J. H., Docherty, K. S., Chhabra, P. S., Bahreini, R., Murphy, S. M., Seinfeld, J. H., Hildebrandt, L., Donahue, N. M., DeCarlo, P. F., Lanz, V. A., Prévôt, A. S. H., Dinar, E., Rudich, Y., and Worsnop, D. R.: Organic aerosol components observed in Northern Hemispheric datasets from Aerosol Mass Spectrometry, Atmos. Chem. Phys., 10, 4625–4641, http://dx.doi.org/10.5194/acp-10-4625-2010doi:10.5194/acp-10-4625-2010, 2010. Nguyen, T. B., Roach, P. J., Laskin, J., Laskin, A., and Nizkorodov, S. A.: Effect of humidity on the composition of isoprene photooxidation secondary organic aerosol, Atmos. Chem. Phys., 11, 6931–6944, http://dx.doi.org/10.5194/acp-11-6931-2011doi:10.5194/acp-11-6931-2011, 2011. Nishino, N., Arey, J., and Atkinson, R.: Formation Yields of Glyoxal and Methylglyoxal from the Gas-Phase OH Radical-Initiated Reactions of Toluene, Xylenes, and Trimethylbenzenes as a Function of NO<sub>2</sub> Concentration, J. Phys Chem. A, 114, 10140–10147, http://dx.doi.org/10.1021/jp105112hdoi:10.1021/jp105112h, 2010. Noziere, B., Voisin, D., Longfellow, C. A., Friedli, H., Henry, B. E., and Hanson, D. R.: The uptake of methyl vinyl ketone, methacrolein, and 2-methyl-3-butene-2-ol onto sulfuric acid solutions, J. Phys. Chem. A, 110 2387–2395, 2006. Noziere, B., Dziedzic, P., and Cordova, A.: Products and kinetics of the liquid-phase reaction of glyoxal catalysed by ammonium ions (NH$_4^+)$, J. Phys. Chem. A, 113, 231–237, 2009. Noziere, B., Dziedzic, P., and Cordova, A.: Inorganic ammonium salts and carbonate salts are efficient catalysts for aldol condensation in atmospheric aerosols, Phys. Chem. Chem. Phys., 12, 3864–3872, 2010a. Noziere, B., Ekström, S., Alsberg, T., and Holmström, S.: Radical-initiated formation of organosulfates and surfactants in atmospheric aerosols, Geophys. Res. Lett., 37, L05806, http://dx.doi.org/10.1029/2009gl041683doi:10.1029/2009gl041683, 2010b. Odum, J. R., Hoffmann, T., Bowman, F., Collins, D., Flagan, R. C., and Seinfeld, J. H.: Gas/particle partitioning and secondary organic aerosol yields, Environ. Sci. Technol., 30, 2580–2585, 1996. Olson, C. N., Galloway, M. M., Yu, G., Hedman, C. J., Lockett, M. R., Yoon, T. P., Stone, E. A., Smith, L. M., and Keutsch, F. N.: Hydroxycarboxylic Acid-Derived Organosulfates: Synthesis, Stability and Quantification in Ambient Aerosol, Environ. Sci. Tech., 45, 6468–6474, 2011. Olson, T. M. and Hoffmann, M. R.: Hydroxyalkylsulfonate formation: its role as a S(IV) reservoir in atmospheric water droplets, Atmos. Environ., 23, 985–997, 1989. Orsini, D. A., Ma, Y., Sullivan, A., Sierau, B., Baumann, K., and Weber, R. J.: Refinements to the particle-into-liquid sampler (PILS) for ground and airborne measurements of water soluble aerosol composition, Atmos. Environ., 37, 1243–1259, http://dx.doi.org/10.1016/s1352-2310(02)01015-4doi:10.1016/s1352-2310(02)01015-4, 2003. Padro, L. T., Tkacik, D., Lathem, T., Hennigan, C. J., Sullivan, A. P., Weber, R. J., Huey, L. G., and Nenes, A.: Investigation of CCN relevant properties and droplet growth kinetics of water-soluble aerosol fraction in Mecixo City, J. Geophys. Res., 115, D09204, doi:09210.01029/02009JD013195, 2010. Pandis, S. N., Wexler, A. S., and Seinfeld, J. H.: Secondary organic aerosol formation and transport – II. Predicting the ambient secondary organic aerosol size distribution, Atmos. Environ. A, 27, 2403–2416, 1993. Pang, Y., Turpin, B. J., and Gundel, L. A.: On the Importance of Organic Oxygen for Understanding Organic Aerosol Particles, Aeros. Sci. Technol., 40, 128–133, 2006. Pankow, J. F.: An Absorption model of the gas/aerosol partitioning involved in the formation of secondary organic aerosol, Atmos. Environ., 28, 189–193, 1994a. Pankow, J. F.: An absorption model of the gas/aerosol partitioning of organic compounds in the atmosphere, Atmos. Environ., 28, 185–188, 1994b. Parikh, H. M., Carlton, A. G., Vizuete, W., and Kamens, R. M.: Modeling secondary organic aerosol using a dynamic partitioning approach incorporating particle aqueous-phase chemistry, Atmos. Environ., 45, 1126–1137, http://dx.doi.org/10.1016/j.atmosenv.2010.11.027doi:10.1016/j.atmosenv.2010.11.027, 2011. Peltier, R. E., Hecobian, A. H., Weber, R. J., Stohl, A., Atlas, E. L., Riemer, D. D., Blake, D. R., Apel, E., Campos, T., and Karl, T.: Investigating the sources and atmospheric processing of fine particles from Asia and the Northwestern United States measured during INTEX B, Atmos. Chem. Phys., 8, 1835–1853, http://dx.doi.org/10.5194/acp-8-1835-2008doi:10.5194/acp-8-1835-2008, 2008. Perri, M. J., Seitzinger, S., and Turpin, B. J.: Secondary organic aerosol production from aqueous photooxidation of glycolaldehyde: Laboratory experiments, Atmos. Environ., 43, 1487–1497, 2009. Perri, M. J., Lim, Y. B., Seitzinger, S. P., and Turpin, B. J.: Organosulfates from glycolaldehyde in aqueous aerosols and clouds: Laboratory studies, Atmos. Environ., 44, 2658–2664, 2010. 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., Prenni, A. J., Kreidenweis, S. M., DeMott, P. J., Matsunaga, A., Lim, Y. B., and Ziemann, P. J.: Chemical aging and the hydrophobic-hydrophilic conversion of carbonaceous aerosol, Geophys. Res. Lett., 33, L24806, http://dx.doi.org/10.1029/2006GL027249doi:10.1029/2006GL027249, 2006. Pfrang, C., Shiraiwa, M., and Pöschl, U.: Chemical ageing and transformation of diffusivity in semi-solid multi-component organic aerosol particles, Atmos. Chem. Phys., 11, 7343–7354, http://dx.doi.org/10.5194/acp-11-7343-2011doi:10.5194/acp-11-7343-2011, 2011. Pickle, T., Allen, D. T., and Pratsinis, S. E.: The sources and size distributions of aliphatic and carbonyl carbon in Los Angeles aerosol, Atmos. Environ. A, 24, 2221–2228, http://dx.doi.org/10.1016/0960-1686(90)90253-jdoi:10.1016/0960-1686(90)90253-j, 1990. Pöschl, U.: Gas-particle interactions of tropospheric aerosols: Kinetic and thermodynamic perspectives of multiphase chemical reactions, amorphous organic substances, and the activation of cloud condensation nuclei, Atmos. Res., 101, 562–573, http://dx.doi.org/10.1016/j.atmosres.2010.12.018doi:10.1016/j.atmosres.2010.12.018, 2011. Reutter, P., Su, H., Trentmann, J., Simmel, M., Rose, D., Gunthe, S. S., Wernli, H., Andreae, M. O., and Pöschl, U.: Aerosol- and updraft-limited regimes of cloud droplet formation: influence of particle number, size and hygroscopicity on the activation of cloud condensation nuclei (CCN), Atmos. Chem. Phys., 9, 7067–7080, http://dx.doi.org/10.5194/acp-9-7067-2009doi:10.5194/acp-9-7067-2009, 2009. Riemer, N., West, M., Zaveri, R., and Easter, R.: Estimating black carbon aging time-scales with a particle resolved aerosol model, J. Aerosol Sci., 1, 143–158, 2010. Rinaldi, M., Decesari, S., Carbone, C., Finessi, E., Fuzzi, S., Ceburnis, D., O'Dowd, C., Sciare, J., Burrows, J., Vrekoussis, M., Ervens, B., Tsigaridis, K., and Facchini, M. C.: Evidence of a natural marine source of oxalic acid and a possible link to glyoxal, J. Geophys. Res., http://dx.doi.org/10.1029/2011JD015659doi:10.1029/2011JD015659, in press, 2011. Rissman, T., Nenes, A., and Seinfeld, J. H.: Chemical Amplification (or Dampening) of the Twomey effect: Conditions derived from Droplet Activation Theory, J. Atmos. Sci., 61, 919–930, 2004. Robinson, A. L., Donahue, N. M., Shrivastava, M. K., Weitkamp, E. A., Sage, A. M., Grieshop, A. P., Lane, T. E., Pierce, J. R., and Pandis, S. N.: Rethinking organic aerosols: Semivolatile emissions and photochemical aging, Science, 315, 1259–1262, 2007. Romakkaniemi, S., Kokkola, H., Smith, J. N., Prisle, N. L., Schwier, A. N., McNeill, V. F., and Laaksonen, A.: Partitioning of semivolatile surface-active compounds between bulk, surface and gas phase, Geophys. Res. Lett., 38, L03807, http://dx.doi.org/10.1029/2010gl046147doi:10.1029/2010gl046147, 2011. Romero, F. and Oehme, M.: Organosulfates – A new Component of Humic-Like Substances in Atmospheric Aerosols?, J. Atmos. Chem., 52, 283–294, 2005. Sagebiel, J. C. and Seiber, J. N.: Studies in the occurrence and distribution of wood smoke makrker compounds in foggy atmospheres, Environ. Toxicol. Chem., 12, 813–822, 1993. Salma, I. and Láng, G. G.: How many carboxyl groups does an average molecule of humic-like substances contain?, Atmos. Chem. Phys., 8, 5997–6002, http://dx.doi.org/10.5194/acp-8-5997-2008doi:10.5194/acp-8-5997-2008, 2008. Salma, I., Ocskay, R., and Láng, G. G.: Properties of atmospheric humic-like substances – water system, Atmos. Chem. Phys., 8, 2243–2254, http://dx.doi.org/10.5194/acp-8-2243-2008doi:10.5194/acp-8-2243-2008, 2008. Sareen, N., Schwier, A. N., Shapiro, E. L., Mitroo, D., and McNeill, V. F.: Secondary organic material formed by methylglyoxal in aqueous aerosol mimics, Atmos. Chem. Phys., 10, 997–1016, http://dx.doi.org/10.5194/acp-10-997-2010doi:10.5194/acp-10-997-2010, 2010. Schmitt-Kopplin, P., Gelencseìr, A., Dabek-Zlotorzynska, E., Kiss, G., Hertkorn, N., Harir, M., Hong, Y., and Gebefugi, I.: Analysis of the Unresolved Organic Fraction in Atmospheric Aerosols with Ultrahigh-Resolution Mass Spectrometry and Nuclear Magnetic Resonance Spectroscopy: Organosulfates As Photochemical Smog Constituents, Anal. Chem., 82, 8017–8026, http://dx.doi.org/10.1021/ac101444rdoi:10.1021/ac101444r, 2010. Schwier, A. N., Sareen, N., Mitroo, D., Shapiro, E. L., and McNeill, V. F.: Glyoxal-Methylglyoxal Cross-Reactions in Secondary Organic Aerosol Formation, Environ. Sci Technol., 44, 6174–6182, http://dx.doi.org/10.1021/es101225qdoi:10.1021/es101225q, 2010. Sciare, J., d'Argouges, O., Sarda-Estève, R., Gaimoz, C., Dolgorouky, C., Bonnaire, N., Favez, O., Bonsang, B., and Gros, V.: Large contribution of water-insoluble secondary organic aerosols in the region of Paris (France) during wintertime, J. Geophys. Res., in press, 2011. Seinfeld, J. H. and Pandis, S. N.: Atmospheric chemistry and physics, John Wiley & Sons, New York, 1326~pp., 1998. Shapiro, E. L., Szprengiel, J., Sareen, N., Jen, C. N., Giordano, M. R., and McNeill, V. F.: Light-absorbing secondary organic material formed by glyoxal in aqueous aerosol mimics, Atmos. Chem. Phys., 9, 2289–2300, http://dx.doi.org/10.5194/acp-9-2289-2009doi:10.5194/acp-9-2289-2009, 2009. Shen, H. and Anastasio, C.: Formation of hydroxyl radical from San Joaquin Valley particles extracted in a cell-free surrogate lung fluid, Atmos. Chem. Phys., 11, 9671–9682, http://dx.doi.org/10.5194/acp-11-9671-2011doi:10.5194/acp-11-9671-2011, 2011. Shiraiwa, M., Pfrang, C., and Pöschl, U.: Kinetic multi-layer model of aerosol surface and bulk chemistry (KM-SUB): the influence of interfacial transport and bulk diffusion on the oxidation of oleic acid by ozone, Atmos. Chem. Phys., 10, 3673–3691, http://dx.doi.org/10.5194/acp-10-3673-2010doi:10.5194/acp-10-3673-2010, 2010. Shrivastava, M. K., Lipsky, E. M., Stanier, C. O., and Robinson, A. L.: Modeling Semivolatile Organic Aerosol Mass Emissions from Combustion Systems, Environ. Sci. Technol., 40, 2671–2677, http://dx.doi.org/10.1021/es0522231doi:10.1021/es0522231, 2006. Sievering, H., Boatman, J., Gorman, E., Kim, Y., Anderson, L., Ennis, G., Luria, M., and Pandis, S.: Removal of sulphur from the marine boundary layer by ozone oxidation in sea-salt aerosols, Nature, 360, 571–573, 1992. Simon, H., Bhave, P. V., Swall, J. L., Frank, N. H., and Malm, W. C.: Determining the spatial and seasonal variability in OM/OC ratios across the US using multiple regression, Atmos. Chem. Phys., 11, 2933–2949, http://dx.doi.org/10.5194/acp-11-2933-2011doi:10.5194/acp-11-2933-2011, 2011. Slowik, J. G., Stroud, C., Bottenheim, J. W., Brickell, P. C., Chang, R. Y.-W., Liggio, J., Makar, P. A., Martin, R. V., Moran, M. D., Shantz, N. C., Sjostedt, S. J., van Donkelaar, A., Vlasenko, A., Wiebe, H. A., Xia, A. G., Zhang, J., Leaitch, W. R., and Abbatt, J. P. D.: Characterization of a large biogenic secondary organic aerosol event from eastern Canadian forests, Atmos. Chem. Phys., 10, 2825–2845, http://dx.doi.org/10.5194/acp-10-2825-2010doi:10.5194/acp-10-2825-2010, 2010. Smith, M. L., Kuwata, M., and Martin, S. T.: Secondary Organic Material Produced by the Dark Ozonolysis of $\alpha $-Pinene Minimally Affects the Deliquescence and Efflorescence of Ammonium Sulfate, Aerosol Sci. Technol., 45, 244–261, 2011. Sorooshian, A., Brechtel, F. J., Ervens, B., Feingold, G., Varutbangkul, V., Bahreini, R., Murphy, S., Holloway, J. S., Atlas, E. L., Anlauf, K., Buzorius, G., Jonsson, H., Flagan, R. C., and Seinfeld, J. H.: Oxalic acid in clear and cloudy atmospheres: Analysis of data from International Consortium for Atmospheric Research on Transport and Transformation 2004, J. Geophys. Res., 111, D23S45, http://dx.doi.org/10.1029/2005JD006880doi:10.1029/2005JD006880, 2006. Sorooshian, A., Lu, M.-L., Brechtel, F. J., Jonsson, H., Feingold, G., Flagan, R. C., and Seinfeld, J. H.: On the source of organic acid aerosol layers above clouds, Environ. Sci. Technol., 41, 4647–4654, 2007. Sorooshian, A., Murphy, S. M., Hersey, S., Bahreini, R., Jonsson, H., Flagan, R. C., and Seinfeld, J. H.: Constraining the contribution of organic acids and AMS \textitm/z 44 to the organic aerosol budget: On the importance of meteorology, aerosol hygroscopicity, and region, Geophys. Res. Lett., 37, L21807, http://dx.doi.org/10.1029/2010gl044951doi:10.1029/2010gl044951, 2010. Spaulding, R. S., Schade, G. W., Goldstein, A. H., and Charles, M. J.: Characterization of secondary atmospheric photooxidation products: Evidence of biogenic and anthropogenic sources, J. Geophys. Res., 108, 4247, http://dx.doi.org/10.1029/2002JD002478doi:10.1029/2002JD002478, 2003. Spracklen, D. V., Jimenez, J. L., Carslaw, K. S., Worsnop, D. R., Evans, M. J., Mann, G. W., Zhang, Q., Canagaratna, M. R., Allan, J., Coe, H., McFiggans, G., Rap, A., and Forster, P.: Aerosol mass spectrometer constraint on the global secondary organic aerosol budget, Atmos. Chem. Phys. Discuss., 11, 5699–5755, http://dx.doi.org/10.5194/acpd-11-5699-2011doi:10.5194/acpd-11-5699-2011, 2011. Stavrakou, T., Müller, J.-F., De Smedt, I., Van Roozendael, M., Kanakidou, M., Vrekoussis, M., Wittrock, F., Richter, A., and Burrows, J. P.: The continental source of glyoxal estimated by the synergistic use of spaceborne measurements and inverse modelling, Atmos. Chem. Phys., 9, 8431–8446, http://dx.doi.org/10.5194/acp-9-8431-2009doi:10.5194/acp-9-8431-2009, 2009. Stefan, M. I. and Bolton, J. R.: Reinvestigation of the acetone degradation mechanism in dilute aqueous solution by the UV/H<sub>2</sub>O<sub>2</sub> process, Environ. Sci. Technol., 33, 870–873, 1999. Steinbacher, M., Dommen, J., Ordonez, C., Reimann, S., Grübler, F. C., Staehelin, J., and Prevot, A. S. H.: Volatile Organic Compounds in the Po Basin. Part A: Anthropogenic VOCs, J. Atmos. Chem., 51, 271–291, http://dx.doi.org/10.1007/s10874-005-3576-1doi:10.1007/s10874-005-3576-1, 2005. Stone, E. A., Hedman, C. J., Sheesley, R. J., Shafer, M. M., and Schauer, J. J.: Investigating the chemical nature of humic-like substances (HULIS) in North American atmospheric aerosols by liquid chromatography tandem mass spectrometry, Atmos. Environ., 43, 4205–4213, http://dx.doi.org/10.1016/j.atmosenv.2009.05.030doi:10.1016/j.atmosenv.2009.05.030, 2009. Sullivan, A. P. and Weber, R. J.: Chemical characterization of the ambient organic aerosol soluble in water: 1. Isolation of hydrophobic and hydrophilic fractions with a XAD-8 resin, J. Geophys. Res., 111, D05314, http://dx.doi.org/10.1029/2005jd006485doi:10.1029/2005jd006485, 2006a. Sullivan, A. P. and Weber, R. J.: Chemical characterization of the ambient organic aerosol soluble in water: 2. Isolation of acid, neutral, and basic fractions by modified size-exclusion chromatography, J. Geophys. Res., 111, D05315, http://dx.doi.org/10.1029/2005jd006486doi:10.1029/2005jd006486, 2006b. Sullivan, R. C. and Prather, K. A.: Investigations of the diurnal cycle and mixing state of oxalic acid in individual particles in Asian aerosol outflow, Environ. Sci Technol., 41, 8062–8069, 2007. Sun, Y. L., Zhang, Q., Anastasio, C., and Sun, J.: Insights into secondary organic aerosol formed via aqueous-phase reactions of phenolic compounds based on high resolution mass spectrometry, Atmos. Chem. Phys., 10, 4809–4822, http://dx.doi.org/10.5194/acp-10-4809-2010doi:10.5194/acp-10-4809-2010, 2010. Surratt, J. D., Kroll, J. H., Kleindienst, T. E., Edney, E. O., Claeys, M., Sorooshian, A., Ng, N. L., Offenberg, J. H., Lewandowski, M., Jaoui, M., Flagan, R. C., and Seinfeld, J. H.: Evidence for organosulfates in secondary organic aerosol, Environ. Sci. Technol., 41, 517–527, 2007a. Surratt, J. D., Lewandowski, M., Offenberg, J. H., Jaoui, M., Kleindienst, T. E., Edney, E. O., and Seinfeld, J. H.: Effect of acidity on secondary organic aerosol formation from isoprene, Environ. Sci Technol., 41, 5363–5369, 2007b. Tan, Y., Perri, M. J., Seitzinger, S. P., and Turpin, B. J.: Effects of Precursor Concentration and Acidic Sulfate in Aqueous Glyoxal-OH Radical Oxidation and Implications for Secondary Organic Aerosol, Environ. Sci. Technol., 43, 8105–8112, http://dx.doi.org/10.1021/es901742fdoi:10.1021/es901742f, 2009. Tan, Y., Carlton, A. G., Seitzinger, S. P., and Turpin, B. J.: SOA from methylglyoxal in clouds and wet aerosols: Measurement and prediction of key products, Atmos. Environ., 44, 5218–5226, 2010. Tan, Y., Lim, Y. B., Altieri, K. E., Seitzinger, S. P., and Turpin, B. J.: Mechanisms leading to oligomers and SOA through aqueous photooxidation: insights from OH radical oxidation of acetic acid, Atmos. Chem. Phys. Discuss., 11, 18319–18347, http://dx.doi.org/10.5194/acpd-11-18319-2011doi:10.5194/acpd-11-18319-2011, 2011. Tang, Y., Thron, R. P., Mauldin, R. L., and Wine, P. H.: Kinetics and spectroscopy of the SO$_4^-$ radical in aqueous solution, J. Photochem. and Photobiol. A, 44, 243–258, 1988. Tilgner, A. and Herrmann, H.: Radical-driven carbonyl-to-acid conversion and acid degradation in tropospheric aqueous systems studied by CAPRAM, Atmos. Environ., 44, 5415–5422, 2010. Trainic, M., Abo Riziq, A., Lavi, A., Flores, J. M., and Rudich, Y.: The optical, physical and chemical properties of the products of glyoxal uptake on ammonium sulfate seed aerosols, Atmos. Chem. Phys., 11, 9697–9707, http://dx.doi.org/10.5194/acp-11-9697-2011doi:10.5194/acp-11-9697-2011, 2011. Tsimpidi, A. P., Karydis, V. A., Zavala, M., Lei, W., Molina, L., Ulbrich, I. M., Jimenez, J. L., and Pandis, S. N.: Evaluation of the volatility basis-set approach for the simulation of organic aerosol formation in the Mexico City metropolitan area, Atmos. Chem. Phys., 10, 525–546, http://dx.doi.org/10.5194/acp-10-525-2010doi:10.5194/acp-10-525-2010, 2010. Turpin, B. J. and Lim, H.: Species contributions to PM$_2.5$ mass concentrations: Revisiting common assumptions for estimating organic mass, Aerosol Sci. Technol., 35, 602–610, 2001. Turpin, B. J., Saxena, P., and Andrews, E.: Measuring and simulating particulate organics in the atmosphere: problems and prospects, Atmos. Environ., 34, 2983–3013, http://dx.doi.org/10.1016/s1352-2310(99)00501-4doi:10.1016/s1352-2310(99)00501-4, 2000. Ulbrich, I. M., Canagaratna, M. R., Zhang, Q., Worsnop, D. R., and Jimenez, J. L.: Interpretation of organic components from Positive Matrix Factorization of aerosol mass spectrometric data, Atmos. Chem. Phys., 9, 2891–2918, http://dx.doi.org/10.5194/acp-9-2891-2009doi:10.5194/acp-9-2891-2009, 2009. Virtanen, A., Joutsensaari, J., Koop, T., Kannosto, J., Yli-Pirila, P., Leskinen, J., Makela, J. M., Holopainen, J. K., Pöschl, U., Kulmala, M., Worsnop, D. R., and Laaksonen, A.: An amorphous solid state of biogenic secondary organic aerosol particles, Nature, 467, 824–827, 2010. Volkamer, R., Jimenez, J. L., SanMartini, F., Dzepina, K., Zhang, Q., Salcedo, D., Molina, L. T., Worsnop, D. R., and Molina, M. J.: Secondary organic aerosol formation from anthropogenic air pollution: Rapid and higher than expected, Geophys. Res. Lett., 33, L17811, http://dx.doi.org/10.1029/2006GL026899doi:10.1029/2006GL026899, 2006. Volkamer, R., SanMartini, F., Molina, L. T., Salcedo, D., Jimenez, J., and Molina, M. J.: A missing sink for gas-phase glyoxal in Mexiko City: Formation of secondary organic aerosol, Geophys. Res. Lett., 34, L19807, http://dx.doi.org/10.1029/2007GL030752doi:10.1029/2007GL030752, 2007. Volkamer, R., Ziemann, P. J., and Molina, M. J.: Secondary Organic Aerosol Formation from Acetylene (C<sub>2</sub>H<sub>2</sub>): seed effect on SOA yields due to organic photochemistry in the aerosol aqueous phase, Atmos. Chem. Phys., 9, 1907–1928, http://dx.doi.org/10.5194/acp-9-1907-2009doi:10.5194/acp-9-1907-2009, 2009. von Hessberg, C., von Hessberg, P., Pöschl, U., Bilde, M., Nielsen, O. J., and Moortgat, G. K.: Temperature and humidity dependence of secondary organic aerosol yield from the ozonolysis of β-pinene, Atmos. Chem. Phys., 9, 3583–3599, http://dx.doi.org/10.5194/acp-9-3583-2009doi:10.5194/acp-9-3583-2009, 2009. Wang, J., Jacob, D. J., and Martin, S. T.: Sensitivity of sulfate direct climate forcing to the hysteresis of particle phase transitions, J. Geophys. Res., 113, D11207, http://dx.doi.org/10.1029/2007jd009368doi:10.1029/2007jd009368, 2008. Wang, J., Doussin, J.-F., Perrier, S., Perraudin, E., Katrib, Y., Pangui, E., and Picquet-Varrault, B.: Design of a new multi-phase experimental simulation chamber for atmospheric photosmog, aerosol and cloud chemistry research, Atmos. Meas. Tech. Discuss., 4, 315–384, http://dx.doi.org/10.5194/amtd-4-315-2011doi:10.5194/amtd-4-315-2011, 2011. Wang, L., Khalizov, A. F., Zheng, J., Xu, W., Ma, Y., Lal, V., and Zhang, R.: Atmospheric nanoparticles formed from heterogeneous reactions of organics, Nature Geosci., 3, 238–242, 2010. Wang, L., Xu, W., Khalizov, A., Zheng, J., Qiu, C., and Zhang, R.: Laboratory Investigation on the Role of Organics in Atmospheric Nanoparticle Growth, J. Phys. Chem. A, 115, 8940–8947, http://dx.doi.org/10.1021/jp1121855doi:10.1021/jp1121855, 2011. Wang, Y., Arellanes, C., Curtis, D. B., and Paulson, S. E.: Probing the Source of Hydrogen Peroxide Associated with Coarse Mode Aerosol Particles in Southern California, Environ. Sci. Technol., 44, 4070–4075, http://dx.doi.org/10.1021/es100593kdoi:10.1021/es100593k, 2010. Warneck, P.: In-cloud chemistry opens pathway to the formation of oxalic acid in the marine atmosphere, Atmos. Environ., 37, 2423–2427, 2003. Weber, R. J., Sullivan, A. P., Peltier, R. E., Russell, A., Yan, B., Zheng, M., DeGouw, J., Warneke, C., Brock, C., Holloway, J. S., Atlas, E. L., and Edgerton, E.: A study of secondary organic aerosol formation in the anthropogenic-influenced southeastern United States, J. Geophys. Res., 112, D13302, http://dx.doi.org/10.1029/2007JD008408doi:10.1029/2007JD008408, 2007. Whiteaker, J. and Prather, K. A.: Hydroxymethanesulfonate as a tracer for fog processing of individual aerosol particles, Atmos. Environ., 37, 1033–1043, 2003. Yao, X., Fang, M., and Chan, C. K.: Size distributions and formation of dicarboxylic acids in atmospheric particles, Atmos. Environ., 36, 2099–2107, 2002. Yao, X., Lau, A. P. S., Fang, M., Chan, C. K., and Hu, M.: Size distribution and formation of ionic species in atmospheric particulate pollutants in Beijing, China: 2. dicarboxylic acids, Atmos. Environ., 37, 3001–3007, 2003. Yasmeen, F., Sauret, N., Gal, J.-F., Maria, P.-C., Massi, L., Maenhaut, W., and Claeys, M.: Characterization of oligomers from methylglyoxal under dark conditions: a pathway to produce secondary organic aerosol through cloud processing during nighttime, Atmos. Chem. Phys., 10, 3803–3812, http://dx.doi.org/10.5194/acp-10-3803-2010doi:10.5194/acp-10-3803-2010, 2010. Yu, G., Bayer, A. R., Galloway, M. M., Korshavn, K. J., Fry, C. G., and Keutsch, F. N.: Glyoxal in Aqueous Ammonium Sulfate Solutions: Products, Kinetics and Hydration Effects, Environ. Sci. Tech., 45, 6336–6342, http://dx.doi.org/10.1021/es200989ndoi:10.1021/es200989n, 2011. Yu, J. Z., Huang, X.-F., Xu, J., and Hu, M.: When Aerosol sulfate goes up, so does Oxalate: Implication for the Formation Mechanisms of Oxalate, Environ. Sci. Technol., 39, 128–133, 2005. Zellner, R., Exner, M., and Herrmann, H.: Absolute OH Quantum Yields in the Laser Photolysis of Nitrate, Nitrite and Dissolved H<sub>2</sub>O<sub>2</sub> at 308 and 351 nm in the Temperature Range of 278-353 K, J. Atmos. Chem., 10, 411–425, 1990. Zhang, H. and Ying, Q.: Secondary organic aerosol formation and source apportionment in Southeast Texas, Atmos. Environ., 45, 3217–3227, http://dx.doi.org/10.1016/j.atmosenv.2011.03.046doi:10.1016/j.atmosenv.2011.03.046, 2011. Zhang, H., Surratt, J. D., Lin, Y. H., Bapat, J., and Kamens, R. M.: Effect of relative humidity on SOA formation from isoprene/NO photooxidation: enhancement of 2-methylglyceric acid and its corresponding oligoesters under dry conditions, Atmos. Chem. Phys., 11, 6411–6424, http://dx.doi.org/10.5194/acp-11-6411-2011doi:10.5194/acp-11-6411-2011, 2011. Zhang, X., Chen, Z. M., and Zhao, Y.: Laboratory simulation for the aqueous OH-oxidation of methyl vinyl ketone and methacrolein: significance to the in-cloud SOA production, Atmos. Chem. Phys., 10, 9551–9561, http://dx.doi.org/10.5194/acp-10-9551-2010doi:10.5194/acp-10-9551-2010, 2010. Zhang, X., Liu, J., Lin, Y., Surratt, J. D., Hayes, P. L., Jimenez, J. L., Parker, E. T., and Weber, R. J.: Evidence for different formation pathways of soluble organic aerosols in two urban atmospheres with contrasting emissions, in preparation, 2011. Ziemann, P. J.: Atmospheric Chemistry: Phase matters for aerosols, Nature, 467, 797–798, 2010. Zuend, A., Marcolli, C., Luo, B. P., and Peter, T.: A thermodynamic model of mixed organic-inorganic aerosols to predict activity coefficients, Atmos. Chem. Phys., 8, 4559–4593, http://dx.doi.org/10.5194/acp-8-4559-2008doi:10.5194/acp-8-4559-2008, 2008. Zuend, A., Marcolli, C., Booth, A. M., Lienhard, D. M., Soonsin, V., Krieger, U. K., Topping, D. O., McFiggans, G., Peter, T., and Seinfeld, J. H.: New and extended parameterization of the thermodynamic model AIOMFAC: calculation of activity coefficients for organic-inorganic mixtures containing carboxyl, hydroxyl, carbonyl, ether, ester, alkenyl, alkyl, and aromatic functional groups, Atmos. Chem. Phys., 11, 9155–9206, http://dx.doi.org/10.5194/acp-11-9155-2011doi:10.5194/acp-11-9155-2011, 2011.