ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-12-3857-2012 Modeling the gas-particle partitioning of secondary organic aerosol: the importance of liquid-liquid phase separation Zuend A. 1 Seinfeld J. H. 1 Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California, USA 03 05 2012 12 9 3857 3882 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/12/3857/2012/acp-12-3857-2012.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/12/3857/2012/acp-12-3857-2012.pdf

The partitioning of semivolatile organic compounds between the gas phase and aerosol particles is an important source of secondary organic aerosol (SOA). Gas-particle partitioning of organic and inorganic species is influenced by the physical state and water content of aerosols, and therefore ambient relative humidity (RH), as well as temperature and organic loading levels. We introduce a novel combination of the thermodynamic models AIOMFAC (for liquid mixture non-ideality) and EVAPORATION (for pure compound vapor pressures) with oxidation product information from the Master Chemical Mechanism (MCM) for the computation of gas-particle partitioning of organic compounds and water. The presence and impact of a liquid-liquid phase separation in the condensed phase is calculated as a function of variations in relative humidity, organic loading levels, and associated changes in aerosol composition. We show that a complex system of water, ammonium sulfate, and SOA from the ozonolysis of α-pinene exhibits liquid-liquid phase separation over a wide range of relative humidities (simulated from 30% to 99% RH). Since fully coupled phase separation and gas-particle partitioning calculations are computationally expensive, several simplified model approaches are tested with regard to computational costs and accuracy of predictions compared to the benchmark calculation. It is shown that forcing a liquid one-phase aerosol with or without consideration of non-ideal mixing bears the potential for vastly incorrect partitioning predictions. Assuming an ideal mixture leads to substantial overestimation of the particulate organic mass, by more than 100% at RH values of 80% and by more than 200% at RH values of 95%. Moreover, the simplified one-phase cases stress two key points for accurate gas-particle partitioning calculations: (1) non-ideality in the condensed phase needs to be considered and (2) liquid-liquid phase separation is a consequence of considerable deviations from ideal mixing in solutions containing inorganic ions and organics that cannot be ignored. Computationally much more efficient calculations relying on the assumption of a complete organic/electrolyte phase separation below a certain RH successfully reproduce gas-particle partitioning in systems in which the average oxygen-to-carbon (O:C) ratio is lower than ~0.6, as in the case of α-pinene SOA, and bear the potential for implementation in atmospheric chemical transport models and chemistry-climate models. A full equilibrium calculation is the method of choice for accurate offline (box model) computations, where high computational costs are acceptable. Such a calculation enables the most detailed predictions of phase compositions and provides necessary information on whether assuming a complete organic/electrolyte phase separation is a good approximation for a given aerosol system. Based on the group-contribution concept of AIOMFAC and O:C ratios as a proxy for polarity and hygroscopicity of organic mixtures, the results from the α-pinene system are also discussed from a more general point of view.

 References Anttila, T., Kiendler-Scharr, A., Mentel, T., and Tillmann, R.: Size dependent partitioning of organic material: evidence for the formation of organic coatings on aqueous aerosols, J. Atmos. Chem., 57, 215–237, http://dx.doi.org/10.1007/s10874-007-9067-9doi:10.1007/s10874-007-9067-9, 2007. Barley, M. H. and McFiggans, G.: The critical assessment of vapour pressure estimation methods for use in modelling the formation of atmospheric organic aerosol, Atmos. Chem. Phys., 10, 749–767, http://dx.doi.org/10.5194/acp-10-749-2010doi:10.5194/acp-10-749-2010, 2010. 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, http://dx.doi.org/10.5194/acp-11-10995-2011doi:10.5194/acp-11-10995-2011, 2011. Booth, A. M., Barley, M. H., Topping, D. O., McFiggans, G., Garforth, A., and Percival, C. J.: Solid state and sub-cooled liquid vapour pressures of substituted dicarboxylic acids using Knudsen Effusion Mass Spectrometry (KEMS) and Differential Scanning Calorimetry, Atmos. Chem. Phys., 10, 4879–4892, http://dx.doi.org/10.5194/acp-10-4879-2010doi:10.5194/acp-10-4879-2010, 2010. Camredon, M., Hamilton, J. F., Alam, M. S., Wyche, K. P., Carr, T., White, I. R., Monks, P. S., Rickard, A. R., and Bloss, W. J.: Distribution of gaseous and particulate organic composition during dark α-pinene ozonolysis, Atmos. Chem. Phys., 10, 2893–2917, http://dx.doi.org/10.5194/acp-10-2893-2010doi:10.5194/acp-10-2893-2010, 2010. Cappa, C. D. and Wilson, K. R.: Evolution of organic aerosol mass spectra upon heating: implications for OA phase and partitioning behavior, Atmos. Chem. Phys., 11, 1895–1911, http://dx.doi.org/10.5194/acp-11-1895-2011doi:10.5194/acp-11-1895-2011, 2011. Cappa, C D., Lovejoy, E R., and Ravishankara, A R.: Evidence for liquid-like and nonideal behavior of a mixture of organic aerosol components, P. Natl. Acad. Sci. USA, 105, 18687–18691, http://dx.doi.org/10.1073/pnas.0802144105doi:10.1073/pnas.0802144105, 2008. Carreira, L A., Hilal, S., and Karickhoff, S W.: Estimation of Chemical Reactivity Parameters and Physical Properties of Organic Molecules Using SPARC, chap 9, Theoretical and Computational Chemistry, Elsevier, 1994. Chang, E I. and Pankow, J F.: Prediction of activity coefficients in liquid aerosol particles containing organic compounds, dissolved inorganic salts, and water – Part 2: Consideration of phase separation effects by an X-UNIFAC model, Atmos. Environ., 40, 6422–6436, http://dx.doi.org/10.1016/j.atmosenv.2006.04.031doi:10.1016/j.atmosenv.2006.04.031, 2006. Chang, E. I. and Pankow, J. F.: Organic particulate matter formation at varying relative humidity using surrogate secondary and primary organic compounds with activity corrections in the condensed phase obtained using a method based on the Wilson equation, Atmos. Chem. Phys., 10, 5475–5490, http://dx.doi.org/10.5194/acp-10-5475-2010doi:10.5194/acp-10-5475-2010, 2010. Chattopadhyay, S. and Ziemann, P J.: Vapor pressures of substituted and unsubstituted monocarboxylic and dicarboxylic acids measured using an improved thermal desorption particle beam mass spectrometry method, Aerosol Sci. Technol., 39, 1085–1100, http://dx.doi.org/10.1080/02786820500421547doi:10.1080/02786820500421547, 2005. Chen, J., Mao, H., Talbot, R W., and Griffin, R J.: Application of the CACM and MPMPO modules using the CMAQ model for the eastern United States, J. Geophys. Res., 111, D23S25, http://dx.doi.org/10.1029/2006JD007603doi:10.1029/2006JD007603, 2006. Chen, Q., Liu, Y., Donahue, N M., Shilling, J E., and Martin, S T.: Particle-Phase Chemistry of Secondary Organic Material: Modeled Compared to Measured O:C and H:C Elemental Ratios Provide Constraints, Environ. Sci. Technol., 45, 4763–4770, http://dx.doi.org/10.1021/es104398sdoi:10.1021/es104398s, 2011. Chung, S H. and Seinfeld, J H.: Global distribution and climate forcing of carbonaceous aerosols, J. Geophys. Res., 107, 4407, http://dx.doi.org/10.1029/2001JD001397doi:10.1029/2001JD001397, 2002. Ciobanu, V G., Marcolli, C., Krieger, U K., Weers, U., and Peter, T.: Liquid-Liquid Phase Separation in Mixed Organic/Inorganic Aerosol Particles, J. Phys. Chem. A, 113, 10966–10978, http://dx.doi.org/10.1021/jp905054ddoi:10.1021/jp905054d, 2009. Ciobanu, V G., Marcolli, C., Krieger, U K., Zuend, A., and Peter, T.: Efflorescence of ammonium sulfate and coated ammonium sulfate particles: evidence for surface nucleation., J. Phys. Chem. A, 114, 9486–9495, http://dx.doi.org/10.1021/jp103541wdoi:10.1021/jp103541w, 2010. Clegg, S L., Seinfeld, J H., and Brimblecombe, P.: Thermodynamic modelling of aqueous aerosols containing electrolytes and dissolved organic compounds, J. Aerosol. Sci., 32, 713–738, 2001. Cocker, D R., Clegg, S L., Flagan, R C., and Seinfeld, J H.: The effect of water on gas-particle partitioning of secondary organic aerosol. Part I: α-pinene/ozone system, Atmos. Environ., 35, 6049–6072, 2001. Compernolle, S., Ceulemans, K., and Müller, J.-F.: Influence of non-ideality on condensation to aerosol, Atmos. Chem. Phys., 9, 1325–1337, http://dx.doi.org/10.5194/acp-9-1325-2009doi:10.5194/acp-9-1325-2009, 2009. 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. 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, http://dx.doi.org/10.1021/es052297cdoi:10.1021/es052297c, 2006. Donahue, N. M., Epstein, S. A., Pandis, S. N., and Robinson, A. L.: A two-dimensional volatility basis set: 1. organic-aerosol mixing thermodynamics, Atmos. Chem. Phys., 11, 3303–3318, http://dx.doi.org/10.5194/acp-11-3303-2011doi:10.5194/acp-11-3303-2011, 2011. Donahue, N. M., Kroll, J. H., Pandis, S. N., and Robinson, A. L.: A two-dimensional volatility basis set – Part 2: Diagnostics of organic-aerosol evolution, Atmos. Chem. Phys., 12, 615–634, http://dx.doi.org/10.5194/acp-12-615-2012doi:10.5194/acp-12-615-2012, 2012. Duplissy, J., DeCarlo, P. F., Dommen, J., Alfarra, M. R., Metzger, A., Barmpadimos, I., Prevot, A. S. H., Weingartner, E., Tritscher, T., Gysel, M., Aiken, A. C., Jimenez, J. L., Canagaratna, M. R., Worsnop, D. R., Collins, D. R., Tomlinson, J., and Baltensperger, U.: Relating hygroscopicity and composition of organic aerosol particulate matter, Atmos. Chem. Phys., 11, 1155–1165, http://dx.doi.org/10.5194/acp-11-1155-2011doi:10.5194/acp-11-1155-2011, 2011. Erdakos, G B. and Pankow, J F.: Gas/particle partitioning of neutral and ionizing compounds to single- and multi-phase aerosol particles. 2. Phase separation in liquid particulate matter containing both polar and low-polarity organic compounds, Atmos. Environ., 38, 1005–1013, http://dx.doi.org/10.1016/j.atmosenv.2003.10.038doi:10.1016/j.atmosenv.2003.10.038, 2004. 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.-Atmos., 109, D15205, http://dx.doi.org/10.1029/2003JD004387doi:10.1029/2003JD004387, 2004. Ervens, B., Turpin, B. J., and Weber, R. J.: Secondary organic aerosol formation in cloud droplets and aqueous particles (aqSOA): a review of laboratory, field and model studies, Atmos. Chem. Phys., 11, 11069–11102, http://dx.doi.org/10.5194/acp-11-11069-2011doi:10.5194/acp-11-11069-2011, 2011. Foley, K. M., Roselle, S. J., Appel, K. W., Bhave, P. V., Pleim, J. E., Otte, T. L., Mathur, R., Sarwar, G., Young, J. O., Gilliam, R. C., Nolte, C. G., Kelly, J. T., Gilliland, A. B., and Bash, J. O.: Incremental testing of the Community Multiscale Air Quality (CMAQ) modeling system version 4.7, Geosci. Model Dev., 3, 205–226, http://dx.doi.org/10.5194/gmd-3-205-2010doi:10.5194/gmd-3-205-2010, 2010. Fountoukis, C. and Nenes, A.: ISORROPIA II: a computationally efficient thermodynamic equilibrium model for K$^+$-Ca$^2+$-Mg$^2+$-NH$_4^+$-Na$^+$-SO$_4^2-$-NO$_3^-$-Cl$^-$-H<sub>2</sub>O aerosols, Atmos. Chem. Phys., 7, 4639–4659, http://dx.doi.org/10.5194/acp-7-4639-2007doi:10.5194/acp-7-4639-2007, 2007. Fredenslund, A., Jones, R L., and Prausnitz, J M.: Group-Contribution Estimation of Activity Coefficients in Nonideal Liquid Mixtures, AIChE J., 21, 1086–1099, 1975. Frosch, M., Zardini, A. A., Platt, S. M., Müller, L., Reinnig, M.-C., Hoffmann, T., and Bilde, M.: Thermodynamic properties and cloud droplet activation of a series of oxo-acids, Atmos. Chem. Phys., 10, 5873–5890, http://dx.doi.org/10.5194/acp-10-5873-2010doi:10.5194/acp-10-5873-2010, 2010. Griffin, R J., Nguyen, K., Dabdub, D., and Seinfeld, J H.: A Coupled Hydrophobic-Hydrophilic Model for Predicting Secondary Organic Aerosol Formation, J. Atmos. Chem., 44, 171–190, 2003. Hallquist, M., Wenger, J. C., Baltensperger, U., Rudich, Y., Simpson, D., Claeys, M., Dommen, J., Donahue, N. M., George, C., Goldstein, A. H., Hamilton, J. F., Herrmann, H., Hoffmann, T., Iinuma, Y., Jang, M., Jenkin, M. E., Jimenez, J. L., Kiendler-Scharr, A., Maenhaut, W., McFiggans, G., Mentel, Th. F., Monod, A., Prévôt, A. S. H., Seinfeld, J. H., Surratt, J. D., Szmigielski, R., and Wildt, J.: The formation, properties and impact of secondary organic aerosol: current and emerging issues, Atmos. Chem. Phys., 9, 5155–5236, http://dx.doi.org/10.5194/acp-9-5155-2009doi:10.5194/acp-9-5155-2009, 2009. Hansen, H K., Rasmussen, P., Fredenslund, A., Schiller, M., and Gmehling, J.: Vapor–liquid-equilibria by UNIFAC group contribution. 5. Revision and extension, Ind. Eng. Chem. Res., 30, 2352–2355, 1991. 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. 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, http://dx.doi.org/10.1016/j.atmosenv.2005.02.016doi:10.1016/j.atmosenv.2005.02.016, 2005. Hilal, S H., Karickhoff, S W., and Carreira, L A.: Prediction of the solubility, activity coefficient and liquid/liquid partition coefficient of organic compounds, QSAR Comb. Sci., 23, 709–720, http://dx.doi.org/10.1002/qsar.200430866doi:10.1002/qsar.200430866, 2004. Hoyle, C. R., Berntsen, T., Myhre, G., and Isaksen, I. S. A.: Secondary organic aerosol in the global aerosol – chemical transport model Oslo CTM2, Atmos. Chem. Phys., 7, 5675–5694, http://dx.doi.org/10.5194/acp-7-5675-2007doi:10.5194/acp-7-5675-2007, 2007. Hoyle, C. R., Myhre, G., Berntsen, T. K., and Isaksen, I. S. A.: Anthropogenic influence on SOA and the resulting radiative forcing, Atmos. Chem. Phys., 9, 2715–2728, http://dx.doi.org/10.5194/acp-9-2715-2009doi:10.5194/acp-9-2715-2009, 2009. Huisman, A J., Krieger, U K., Zuend, A., Marcolli, C., and Peter, T.: Vapor pressures of substituted polycarboxylic acids, in preparation, 2012. Jenkin, M. E.: Modelling the formation and composition of secondary organic aerosol from α- and β-pinene ozonolysis using MCM v3, Atmos. Chem. Phys., 4, 1741–1757, http://dx.doi.org/10.5194/acp-4-1741-2004doi:10.5194/acp-4-1741-2004, 2004. Jenkin, M E., Saunders, S M., and Pilling, M J.: The tropospheric degradation of volatile organic compounds: A protocol for mechanism development, Atmos. Environ., 31, 81–104, http://dx.doi.org/10.1016/S1352-2310(96)00105-7doi:10.1016/S1352-2310(96)00105-7, 1997. 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, 1525–1529, http://dx.doi.org/10.1126/science.1180353doi:10.1126/science.1180353, 2009. Kalberer, M., Paulsen, D., Sax, M., Steinbacher, M., Dommen, J., Prevot, A. S H., Fisseha, R., Weingartner, E., Frankevich, V., Zenobi, R., and Baltensperger, U.: Identification of Polymers asMajor Components of Atmospheric Organic Aerosols, Science, 303, 1659–1662, 2004. 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. Kelly, J. T., Bhave, P. V., Nolte, C. G., Shankar, U., and Foley, K. M.: Simulating emission and chemical evolution of coarse sea-salt particles in the Community Multiscale Air Quality (CMAQ) model, Geosci. Model Dev., 3, 257–273, http://dx.doi.org/10.5194/gmd-3-257-2010doi:10.5194/gmd-3-257-2010, 2010. Knopf, D A., Anthony, L M., and Bertram, A K.: Reactive Uptake of O$_\rm 3$ by Multicomponent and Multiphase Mixtures Containing Oleic Acid, J. Phys. Chem. A, 109, 5579–5589, 2005. Koop, T., Bookhold, J., Shiraiwa, M., and Poschl, U.: Glass transition and phase state of organic compounds: dependency on molecular properties and implications for secondary organic aerosols in the atmosphere, Phys. Chem. Chem. Phys., 13, 19238–19255, http://dx.doi.org/10.1039/c1cp22617gdoi:10.1039/c1cp22617g, 2011. Kroll, J H. and Seinfeld, J H.: Chemistry of secondary organic aerosol: Formation and evolution of low-volatility organics in the atmosphere, Atmos. Environ., 42, 3593–3624, http://dx.doi.org/10.1016/j.atmosenv.2008.01.003doi:10.1016/j.atmosenv.2008.01.003, 2008. Kwamena, N.-O A., Buajarern, J., and Reid, J P.: Equilibrium Morphology of Mixed Organic/Inorganic/Aqueous Aerosol Droplets: Investigating the Effect of Relative Humidity and Surfactants, J. Phys. Chem. A, 114, 5787–5795, http://dx.doi.org/10.1021/jp1003648doi:10.1021/jp1003648, 2010. Lienhard, D M., Zobrist, B., Zuend, A., Krieger, U K., and Peter, T.: Experimental evidence for excess entropy discontinuities in glass-forming solutions, J. Chem. Phys., 136, 074515, http://dx.doi.org/10.1063/1.3685902doi:10.1063/1.3685902, 2012. Lim, H.-J., Carlton, A G., and Turpin, B J.: Isoprene Forms Secondary Organic Aerosol through Cloud Processing: Model Simulations, Environ. Sci. Technol., 39, 4441–4446, http://dx.doi.org/10.1021/es048039hdoi:10.1021/es048039h, 2005. 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. Marcolli, C. and Krieger, U K.: Phase changes during hygroscopic cycles of mixed organic/inorganic model systems of tropospheric aerosols, J. Phys. Chem. A, 110, 1881–1893, http://dx.doi.org/10.1021/jp0556759doi:10.1021/jp0556759, 2006. Maria, S F., Russell, L M., Gilles, M K., and Myneni, S. C B.: Organic aerosol growth mechanisms and their climate-forcing implications, Science, 306, 1921–1924, http://dx.doi.org/10.1126/science.1103491doi:10.1126/science.1103491, 2004. 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. McFiggans, G., Topping, D. O., and Barley, M. H.: The sensitivity of secondary organic aerosol component partitioning to the predictions of component properties – Part 1: A systematic evaluation of some available estimation techniques, Atmos. Chem. Phys., 10, 10255–10272, http://dx.doi.org/10.5194/acp-10-10255-2010doi:10.5194/acp-10-10255-2010, 2010. Moré, J J., Garbow, B S., and Hillstrom, K E.: User Guide for MINPACK-1, Argonne National Laboratory Report ANL-80-74, Argonne, Ill., USA, http://www.netlib.org/minpack/, 1980. Moré, J J., Sorensen, D C., Hillstrom, K E., and Garbow, B S.: The MINPACK Project, in Sources and Development of Mathematical Software, Prentice-Hall, Inc., Upper Saddle River, NJ, USA, 1984. Müller, L., Reinnig, M.-C., Hayen, H., and Hoffmann, T.: Characterization of oligomeric compounds in secondary organic aerosol using liquid chromatography coupled to electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry, Rapid Commun. Mass Spectrom., 23, 971–979, http://dx.doi.org/10.1002/rcm.3957doi:10.1002/rcm.3957, 2009. 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. Pankow, J F.: An absorption model of gas/particle partitioning of organic compounds in the atmosphere, Atmos. Environ., 28, 185–188, 1994. Pankow, J F.: Gas/particle partitioning of neutral and ionizing compounds to single and multi-phase aerosol particles. 1.Unified modeling framework, Atmos. Environ., 37, 3323–3333, http://dx.doi.org/10.1016/S1352-2310(03)00346-7doi:10.1016/S1352-2310(03)00346-7, 2003. Pankow, J. F. and Asher, W. E.: SIMPOL.1: a simple group contribution method for predicting vapor pressures and enthalpies of vaporization of multifunctional organic compounds, Atmos. Chem. Phys., 8, 2773–2796, http://dx.doi.org/10.5194/acp-8-2773-2008doi:10.5194/acp-8-2773-2008, 2008. Pathak, R K., Stanier, C O., Donahue, N M., and Pandis, S N.: Ozonolysis of α-pinene at atmospherically relevant concentrations: Temperature dependence of aerosol mass fractions (yields), J. Geophys. Res., 112, D03201, http://dx.doi.org/10.1029/2006JD007436doi:10.1029/2006JD007436, 2007. 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. 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. Press, W H., Teukolsky, S A., Vetterling, W T., and Flannery, B P.: Numerical Recipes 3rd Edition: The Art of Scientific Computing, Cambridge University Press, 3 edn., http://www.worldcat.org/isbn/0521880688, 2007. Pun, B. K L., Griffin, R J., Seigneur, C., and Seinfeld, J H.: Secondary organic aerosol - 2. Thermodynamic model for gas/particle partitioning of molecular constituents, J. Geophys. Res. Atmos., 107, 4333, http://dx.doi.org/10.1029/2001JD000542doi:10.1029/2001JD000542, 2002. Pye, H. O. T. and Seinfeld, J. H.: A global perspective on aerosol from low-volatility organic compounds, Atmos. Chem. Phys., 10, 4377–4401, http://dx.doi.org/10.5194/acp-10-4377-2010doi:10.5194/acp-10-4377-2010, 2010. Reid, J P., Dennis-Smither, B J., Kwamena, N.-O A., Miles, R. E H., Hanford, K L., and Homer, C J.: The morphology of aerosol particles consisting of hydrophobic and hydrophilic phases: hydrocarbons, alcohols and fatty acids as the hydrophobic component, Phys. Chem. Chem. Phys., 13, 15559–15572, http://dx.doi.org/10.1039/C1CP21510Hdoi:10.1039/C1CP21510H, 2011. 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, http://dx.doi.org/10.1126/science.1133061doi:10.1126/science.1133061, 2007. Rudich, Y., Donahue, N M., and Mentel, T F.: Aging of Organic Aerosol: Bridging the Gap Between Laboratory and Field Studies, Annu. Rev. Phys. Chem., 58, 321–352, http://dx.doi.org/10.1146/annurev.physchem.58.032806.104432doi:10.1146/annurev.physchem.58.032806.104432, 2007. Saunders, S. M., Jenkin, M. E., Derwent, R. G., and Pilling, M. J.: Protocol for the development of the Master Chemical Mechanism, MCM v3 (Part A): tropospheric degradation of non-aromatic volatile organic compounds, Atmos. Chem. Phys., 3, 161–180, http://dx.doi.org/10.5194/acp-3-161-2003doi:10.5194/acp-3-161-2003, 2003. Shilling, J. E., Chen, Q., King, S. M., Rosenoern, T., Kroll, J. H., Worsnop, D. R., McKinney, K. A., and Martin, S. T.: Particle mass yield in secondary organic aerosol formed by the dark ozonolysis of α-pinene, Atmos. Chem. Phys., 8, 2073–2088, http://dx.doi.org/10.5194/acp-8-2073-2008doi:10.5194/acp-8-2073-2008, 2008. Shilling, J. E., Chen, Q., King, S. M., Rosenoern, T., Kroll, J. H., Worsnop, D. R., DeCarlo, P. F., Aiken, A. C., Sueper, D., Jimenez, J. L., and Martin, S. T.: Loading-dependent elemental composition of α-pinene SOA particles, Atmos. Chem. Phys., 9, 771–782, http://dx.doi.org/10.5194/acp-9-771-2009doi:10.5194/acp-9-771-2009, 2009. Shiraiwa, M., Ammann, M., Koop, T., and Pöschl, U.: Gas uptake and chemical aging of semisolid organic aerosol particles, P. Natl. Acad. Sci. USA, 108, 11003–11008, http://dx.doi.org/10.1073/pnas.1103045108doi:10.1073/pnas.1103045108, 2011. Smith, M L., Kuwata, M., and Martin, S T.: Secondary Organic Material Produced by the Dark Ozonolysis of α-Pinene Minimally Affects the Deliquescence and Efflorescence of Ammonium Sulfate, Aerosol Sci. Technol., 45, 244–261, http://dx.doi.org/10.1080/02786826.2010.532178doi:10.1080/02786826.2010.532178, 2011. Song, C., Zaveri, R A., Alexander, M L., Thornton, J A., Madronich, S., Ortega, J V., Zelenyuk, A., Yu, X.-Y., Laskin, A., and Maughan, D A.: Effect of hydrophobic primary organic aerosols on secondary organic aerosol formation from ozonolysis of a-pinene, Geophys. Res. Lett., 34, L20803, http://dx.doi.org/10.1029/2007GL030720doi:10.1029/2007GL030720, 2007. Song, M., Marcolli, C., Krieger, U. K., Zuend, A., and Peter, T.: Liquid-liquid phase separation and morphology of internally mixed dicarboxylic acids/ammonium sulfate/water particles, Atmos. Chem. Phys., 12, 2691–2712, http://dx.doi.org/10.5194/acp-12-2691-2012doi:10.5194/acp-12-2691-2012, 2012. Soonsin, V., Zardini, A. A., Marcolli, C., Zuend, A., and Krieger, U. K.: The vapor pressures and activities of dicarboxylic acids reconsidered: the impact of the physical state of the aerosol, Atmos. Chem. Phys., 10, 11753–11767, http://dx.doi.org/10.5194/acp-10-11753-2010doi:10.5194/acp-10-11753-2010, 2010. 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, 2006. Surratt, J D., Chan, A. W H., Eddingsaas, N C., Chan, M N., Loza, C L., Kwan, A J., Hersey, S P., Flagan, R C., Wennberg, P O., and Seinfeld, J H.: Reactive intermediates revealed in secondary organic aerosol formation from isoprene, P. Natl. Acad. Sci., 107, 6640–6645, http://dx.doi.org/10.1073/pnas.0911114107doi:10.1073/pnas.0911114107, 2010. Tong, H.-J., Reid, J. P., Bones, D. L., Luo, B. P., and Krieger, U. K.: Measurements of the timescales for the mass transfer of water in glassy aerosol at low relative humidity and ambient temperature, Atmos. Chem. Phys., 11, 4739–4754, http://dx.doi.org/10.5194/acp-11-4739-2011doi:10.5194/acp-11-4739-2011, 2011. Topping, D., Lowe, D., and McFiggans, G.: Partial Derivative Fitted Taylor Expansion: an efficient method for calculating gas/liquid equilibria in atmospheric aerosol particles – Part 2: Organic compounds, Geosci. Model Dev., 5, 1–13, http://dx.doi.org/10.5194/gmd-5-1-2012doi:10.5194/gmd-5-1-2012, 2012. Topping, D O., Lowe, D., and McFiggans, G.: Partial Derivative Fitted Taylor Expansion: An efficient method for calculating gas-liquid equilibria in atmospheric aerosol particles: 1. Inorganic compounds, J. Geophys. Res. Atmos., 114, D04304, http://dx.doi.org/10.1029/2008JD010099doi:10.1029/2008JD010099, 2009. Vaden, T D., Imre, D., Beranek, J., Shrivastava, M., and Zelenyuk, A.: Evaporation kinetics and phase of laboratory and ambient secondary organic aerosol, P. Natl. Acad. Sci. USA, 108, 2190–2195, http://dx.doi.org/10.1073/pnas.1013391108doi:10.1073/pnas.1013391108, 2011. Valorso, R., Aumont, B., Camredon, M., Raventos-Duran, T., Mouchel-Vallon, C., Ng, N. L., Seinfeld, J. H., Lee-Taylor, J., and Madronich, S.: Explicit modelling of SOA formation from α-pinene photooxidation: sensitivity to vapour pressure estimation, Atmos. Chem. Phys., 11, 6895–6910, http://dx.doi.org/10.5194/acp-11-6895-2011doi:10.5194/acp-11-6895-2011, 2011. Virtanen, A., Joutsensaari, J., Koop, T., Kannosto, J., Yli-Pirilä, P., Leskinen, J., Mäkelä, 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, http://dx.doi.org/10.1038/nature09455doi:10.1038/nature09455, 2010. Zaveri, R A., Easter, R C., and Peters, L K.: A computationally efficient Multicomponent Equilibrium Solver for Aerosols (MESA), J. Geophys. Res., 110, D24203, http://dx.doi.org/10.1029/2004JD005618doi:10.1029/2004JD005618, 2005. Zobrist, B., Marcolli, C., Pedernera, D. A., and Koop, T.: Do atmospheric aerosols form glasses?, Atmos. Chem. Phys., 8, 5221–5244, http://dx.doi.org/10.5194/acp-8-5221-2008doi:10.5194/acp-8-5221-2008, 2008. Zobrist, B., Soonsin, V., Luo, B.-P., Krieger, U K., Marcolli, C., Peter, T., and Koop, T.: Ultra-slow water diffusion in aqueous sucrose glasses, Phys. Chem. Chem. Phys., 13, 3514–3526, http://dx.doi.org/10.1039/C0CP01273Ddoi:10.1039/C0CP01273D, 2011. 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., Peter, T., and Seinfeld, J. H.: Computation of liquid-liquid equilibria and phase stabilities: implications for RH-dependent gas/particle partitioning of organic-inorganic aerosols, Atmos. Chem. Phys., 10, 7795–7820, http://dx.doi.org/10.5194/acp-10-7795-2010doi:10.5194/acp-10-7795-2010, 2010. 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.