ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-12-5879-2012 Aqueous phase processing of secondary organic aerosol from isoprene photooxidation Liu Y. 1 2 4 Monod A. 1 2 Tritscher T. 3 5 Praplan A. P. 3 DeCarlo P. F. 3 6 Temime-Roussel B. 1 2 Quivet E. 1 2 Marchand N. 1 2 Dommen J. 3 Baltensperger U. 3 Aix-Marseille Université, Laboratoire Chimie Environnement, 13331, Marseille cedex 03, France CNRS, Laboratoire Chimie Environnement (FRE 3416), 13331, Marseille cedex 03, France Paul Scherrer Institute (PSI), Laboratory of Atmospheric Chemistry, 5232, Villigen, Switzerland now at: LGEI, 6, avenue de Clavière, 30319, Alès, CEDEX, France now at: TSI GmbH, Particle Instruments, Neuköllner Str. 4, 52068 Aachen, Germany now at: Drexel University, Dept. of Civil, Architectural, and Environmental Engineering, Philadelphia, PA 19104, USA 10 07 2012 12 13 5879 5895 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/12/5879/2012/acp-12-5879-2012.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/12/5879/2012/acp-12-5879-2012.pdf

Transport of reactive air masses into humid and wet areas is highly frequent in the atmosphere, making the study of aqueous phase processing of secondary organic aerosol (SOA) very relevant. We have investigated the aqueous phase processing of SOA generated from gas-phase photooxidation of isoprene using a smog chamber. The SOA collected on filters was extracted by water and subsequently oxidized in the aqueous phase either by H<sub>2</sub>O<sub>2</sub> under dark conditions or by OH radicals in the presence of light, using a photochemical reactor. Online and offline analytical techniques including SMPS, HR-AMS, H-TDMA, TD-API-AMS, were employed for physical and chemical characterization of the chamber SOA and nebulized filter extracts. After aqueous phase processing, the particles were significantly more hygroscopic, and HR-AMS data showed higher signal intensity at <i>m/z</i> 44 and a lower signal intensity at <i>m/z</i> 43, thus showing the impact of aqueous phase processing on SOA aging, in good agreement with a few previous studies. Additional offline measurement techniques (IC-MS, APCI-MS<sup>2</sup> and HPLC-APCI-MS) permitted the identification and quantification of sixteen individual chemical compounds before and after aqueous phase processing. Among these compounds, small organic acids (including formic, glyoxylic, glycolic, butyric, oxalic and 2,3-dihydroxymethacrylic acid (i.e. 2-methylglyceric acid)) were detected, and their concentrations significantly increased after aqueous phase processing. In particular, the aqueous phase formation of 2-methylglyceric acid and trihydroxy-3-methylbutanal was correlated with the consumption of 2,3-dihydroxy-2-methyl-propanal, and 2-methylbutane-1,2,3,4-tetrol, respectively, and an aqueous phase mechanism was proposed accordingly. Overall, the aging effect observed here was rather small compared to previous studies, and this limited effect could possibly be explained by the lower liquid phase OH concentrations employed here, and/or the development of oligomers observed during aqueous phase processing.

 References Aiken, A. C., DeCarlo, P. F., Kroll, J. H., Worsnop, D. R., Huffman, J. A., Docherty, K., Ulbrich, I. M., Mohr, C., Kimmel, J. R., Sueper, D., Zhang, Q., Sun, Y., Trimborn, A., Northway, M., Ziemann, P. J., Canagaratna, M. R., Onasch, T. B., Alfarra, 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, 4478–4485, http://dx.doi.org/10.1021/es703009qdoi:10.1021/es703009q, 2008. Altieri, K. E., Carlton, A. G., Lim, H. J., Turpin, B. J., and Seitzinger, S. P.: Evidence for oligomer formation in clouds: reactions 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. Anastasio, C. and McGregor, K. G.: Chemistry of fog waters in California's Central Valley. 1. In situ photoformation of hydroxyl radical and singlet molecular oxygen, Atmos. Environ., 35, 1079–1089, 2001. Bateman, A. P., Nizkorodov, S. A., Laskinb, J., and Laskinc, A: Photolytic processing of secondary organic aerosols dissolved in cloud droplets, Phys. Chem. Chem. Phys., 13, 12199–12212, 2011. 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 acids in clouds, Geophys. Res. Lett., 33, L06822, http://dx.doi.org/10.1029/2005GL025374doi:10.1029/2005GL025374, 2006. Carlton, A. G., Turpin, B. J., Altieri, K. E., Seitzinger, S., Reff, A., Lim, H. J., 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., Wiedinmyer, C., and Kroll, J. H.: A review of Secondary Organic Aerosol (SOA) formation from isoprene, Atmos. Chem. Phys., 9, 4987–5005, http://dx.doi.org/10.5194/acp-9-4987-2009doi:10.5194/acp-9-4987-2009, 2009. Chang, R. Y.-W., Slowik, J. G., Shantz, N. C., Vlasenko, A., Liggio, J., Sjostedt, S. J., Leaitch, W. R., and Abbatt, J. P. D.: The hygroscopicity parameter (κ) of ambient organic aerosol at a field site subject to biogenic and anthropogenic influences: relationship to degree of aerosol oxidation, Atmos. Chem. Phys., 10, 5047–5064, http://dx.doi.org/10.5194/acp-10-5047-2010doi:10.5194/acp-10-5047-2010, 2010. Chhabra, P. S., Ng, N. L., Canagaratna, M. R., Corrigan, A. L., Russell, L. M., Worsnop, D. R., Flagan, R. C., and Seinfeld, J. H.: Elemental composition and oxidation of chamber organic aerosol, Atmos. Chem. Phys., 11, 8827–8845, http://dx.doi.org/10.5194/acp-11-8827-2011doi:10.5194/acp-11-8827-2011, 2011. Claeys, M., Graham, B., Vas, G., Wang, W., Vermeylen, R., Pashynska, V., Cafmeyer, J., Guyon, P., Andreae, M. O., Artaxo, P., and Maenhaut, W.: Formation of secondary organic aerosols through photooxidation of isoprene, Science, 303, 1173–1176, 2004a. Claeys, M., Wang, W., Ion, A. C., Kourtchev, I., Gelencser, A., and Maenhaut, W.: Formation of secondary organic aerosols from isoprene and its gas-phase oxidation products through reaction with hydrogen peroxide, Atmos. Environ., 38, 4093–4098, 2004b. DeCarlo, P. F., Kimmel, J. R., Trimborn, A., and Northway, M. J.: Field-deployable, high-resolution, time-of-flight aerosol mass spectrometer, Anal. Chem., 78, 8281–8289, 2006. Dommen, J., Metzger, A., Duplissy, J., Kalberer, M., Alfarra, M. R., Gascho, A., Weingartner, E., Prevot, A. S. H., Verheggen, B., and Baltensperger, U.: Laboratory observation of oligomers in the aerosol from isoprene/NO$_\mathrmx$ photooxidation, Geophys. Res. Lett., 33, L13805, http://dx.doi.org/10.1029/2006GL026523doi:10.1029/2006GL026523, 2006. 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. 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$_\mathrmx$/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., 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. Eyglunent, G., Le Person, A., Dron, J., Monod, A., Voisin, D., Mellouki, A., Marchand, N., and Wortham, H.: Simple and reversible transformation of an APCI/MS/MS into an aerosol mass spectrometer: development and characterization of a new inlet, Aerosol Sci. Technol., 42, 182–193, 2008. Guzmán, M. I., Colussi, A. I., and Hoffmann, M. R.: Photoinduced oligomerization of aqueous pyruvic acid, J. Phys. Chem. A, 110, 3619–3626, 2006. Gysel, M., McFiggans, G. B., and Coe, H.: Inversion of tandem differential mobility analyser (TDMA) measurements, J. Aerosol Sci., 40, 134–151, 2009. 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 \mboximpact 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. 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. 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, 2010. Hua, W., Chen, Z. M., Jie, C. Y., Kondo, Y., Hofzumahaus, A., Takegawa, N., Chang, C. C., Lu, K. D., Miyazaki, Y., Kita, K., Wang, H. L., Zhang, Y. H., and Hu, M.: Atmospheric hydrogen peroxide and organic hydroperoxides during PRIDE-PRD'06, China: their concentration, formation mechanism and contribution to secondary aerosols, Atmos. Chem. Phys., 8, 6755–6773, http://dx.doi.org/10.5194/acp-8-6755-2008doi:10.5194/acp-8-6755-2008, 2008. Jimenez, J. L., Canagaratna, M. R., Donahue, N. M., Prevot, A. S., Zhang, Q., Kroll, J. H., DeCarlo, P. F., Allan, J. D., Coe, H., Ng, N. L., Aiken, A. C., Docherty, K. S., Ulbrich, I. M., Grieshop, A. P., Robinson, A. L., Duplissy, J., Smith, J. D., Wilson, K. R., Lanz, V. A., Hueglin, C., Sun, Y. L., Tian, J., Laaksonen, A., Raatikainen, T., Rautiainen, J., Vaattovaara, P., Ehn, M., Kulmala, M., Tomlinson, J. M., Collins, D. R., Cubison, M. J., Dunlea, E. J., Huffman, J. A., Onasch, T. B., Alfarra, M. R., Williams, P. I., Bower, K., Kondo, Y., Schneider, J., Drewnick, F., Borrmann, S., Weimer, S., Demerjian, K., Salcedo, D., Cottrell, L., Griffin, R., Takami, A., Miyoshi, T., Hatakeyama, S., Shimono, A., Sun, J. Y., Zhang, Y. M., Dzepina, K., Kimmel, J. R., Sueper, D., Jayne, J. T., Herndon, S. C., Trimborn, A. M., Williams, L. R., Wood, E. C., Middlebrook, A. M., Kolb, C. E., Baltensperger, U., and Worsnop, D. R.: Evolution of organic aerosols in the atmosphere, Science, 326, 1525–1529, 2009. 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. 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, 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, L11805, http://dx.doi.org/10.1029/2011gl047439doi:10.1029/2011gl047439, 2011. Legrand, M. and Puxbaum, H.: Summary of the CARBOSOL project: Present and retrospective state of organic versus inorganic aerosol over Europe, J. Geophys. Res., 112, D23S01, http://dx.doi.org/10.1029/2006JD008271doi:10.1029/2006JD008271, 2007. Lin, Y.H ., Zhang, Z., Docherty, K. S., Zhang, H., Budisulistiorini, S. H., Rubitschun, C. L., Shaw, S. L., Knipping, E. M., Edgerton, E. S., Kleindienst, T. E., Gold, A., and Surratt, J. D.: Isoprene epoxydiols as precursors to secondary organic aerosol formation: Acid-catalyzed reactive uptake studies with authentic compounds. Environ. Sci. Technol., 46, 250–258, 2012. 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., El Zein, A., Siekmann, F., Salque, G., El Haddad, I., Temime-Roussel, B., Voisin, D., Thissen, R., and Monod, A.: Oligomer and SOA formation through atmospheric aqueous phase processing of methacrolein and methyl vinyl ketone, Atmos. Environ., 49, 123–129, 2012. Marinoni, A., Laj, P., Sellegri, K., and Mailhot, G.: Cloud chemistry at the Puy de Dôme: variability and relationships with environmental factors, Atmos. Chem. Phys., 4, 715–728, http://dx.doi.org/10.5194/acp-4-715-2004doi:10.5194/acp-4-715-2004, 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. 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. Monod, A., Chevallier, E., Durand-Jolibois, R., Doussin, J. F., Picquet-Varrault, B., and Carlier, P.: Photooxidation of methylhydroperoxide and ethylhydroperoxide in the aqueous phase under simulated cloud droplet conditions, Atmos. Environ., 41, 2412–2426, 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. Nguyen, T. B., Laskin, A., Laskin, J., and Nizkorodov, S. A.: Direct aqueous photochemistry of isoprene high-NO$_\mathrmx$ secondary organic aerosol, Chem. Phys. Phys. Chem., 14, 9702–9714, http://dx.doi.org/10.1039/c2cp40944edoi:10.1039/c2cp40944e, 2012. Orlovic-Leko, P., Plavsic, M., Bura-Nakic, E., Kozarac, Z., and Cosovic, B.: Organic matter in the bulk precipitations in Zagreb and Sibenik, Croatia, Atmos. Environ., 43, 805–811, 2009. Ortiz-Montalvo, D. L., Lim, Y. B., Perri, M. J., Seitzinger, S. P., and Turpin, B. J.: Volatility and Yield of Glycolaldehyde SOA Formed through Aqueous Photochemistry and Droplet Evaporation, Aerosol Sci. Technol., 46, 1002–1014, 2012. Paulsen, D., Dommen, J., Kalberer, M., Prévôt, A. S. H., Richter, R., Sax, M., Steinbacher, M., Weingartner, E., and Baltensperger, U.: Secondary organic aerosol formation by irradiation of 1,3,5-trimethylbenzene-NO$_\mathrmx$-H<sub>2</sub>O in a new reaction chamber for atmospheric chemistry and physics, Environ. Sci. Technol., 39, 2668–2678, 2005. Paulsen, D., Weingartner, E., Alfarra, M. R., and Baltensperger, U.: Volatility measurements of photochemically and nebulizer generated organic aerosol particles, J. Aerosol Sci., 37, 1025–1051, 2006. 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. Perri, M. J., Seitzinger, S. P., and Turpin, B. J.: Secondary organic aerosol production from aqueous photooxidation of glycolaldehyde: laboratory experiments, Atmos. Environ., 43, 1487–1497, 2009. Rudich, Y., Donahue, M. N., and Mentel, F. T.: Aging of organic aerosol: bridging the gap between laboratory and field studies, Annu. Rev. Chem., 58, 321–352, 2007. Sato, K.: Detection of nitrooxypolyols in secondary organic aerosol formed from the photooxidation of conjugated dienes under high-NO$_\mathrmx$ conditions, Atmos. Environ., 42, 6851–6861, 2008. Silva Santos, L., Dalmazio, I., Eberlin, M. N., Claeys, M., and Augusti, R.: Mimicking the atmospheric OH-radical-mediated photooxidation of isoprene: formation of cloud-condensation nuclei polyols monitored by electrospray ionization mass spectrometry, Rapid Commun. Mass Sp., 20, 2104–2108, 2006. Sorooshian, A., Varutbangkul, V., Brechtel, F. J., Ervens, B., Feingold, G., Bahreini, R., Murphy, S. M., Holloway, J. S., Atlas, E. L., Buzorius, G., Jonsson, H., Flagan, R. C., and Seinfeld, J. H.: Oxalic acid in clear and cloudy atmospheres: Analysis of data from the 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. 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., Murphy, S. M., Kroll, J. H., Ng, N. L., Hildebrandt, L., Sorooshian, A., Szmigielski, R., Vermeylen, R., Maenhaut, W., Claeys, M., Flagan, R. C., and Seinfeld, J. H.: Chemical composition of secondary organic aerosol formed from the photooxidation of isoprene, J. Phys. Chem. A, 110, 9665–9690, 2006. \hack Surratt, J. D., Chan, A. W. H., Eddingsaas, N. C., Chan, M., 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, 2010. Szmigielski, R., Surratt, J. D., Vermeylen, R., Szmigielska, K., Kroll, J. H., Ng, N. L., Murphy, S. M., Sorooshian, A., Seinfeld, J. H., and Claeys, M.: Characterization of 2-methylglyceric acid oligomers in secondary organic aerosol from the photooxidation of isoprene using trimethylsilylation and gas chromatography/ion trap mass spectrometry, J. Mass Spectrom., 42, 101–116, 2007. 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, 2009. Tan, Y., Carlton, G. A., 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 and methylglyoxal, Atmos. Chem. Phys., 12, 801–813, http://dx.doi.org/10.5194/acp-12-801-2012doi:10.5194/acp-12-801-2012, 2012. Tritscher, T., Dommen, J., DeCarlo, P. F., Gysel, M., Barmet, P. B., Praplan, A. P., Weingartner, E., Prévôt, A. S. H., Riipinen, I., Donahue, N. M., and Baltensperger, U.: Volatility and hygroscopicity of aging secondary organic aerosol in a smog chamber, Atmos. Chem. Phys., 11, 11477–11496, http://dx.doi.org/10.5194/acp-11-11477-2011doi:10.5194/acp-11-11477-2011, 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. 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.