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www.atmos-chem-phys-discuss.net/9/22993/2009/
doi:10.5194/acpd-9-22993-2009
© Author(s) 2009. This work is distributed
under the Creative Commons Attribution 3.0 License.
Characterization of non-photochemically formed oligomers from methylglyoxal: a pathway to produce secondary organic aerosol through cloud processing during night-time
1Laboratoire de Radiochimie Sciences Analytique et Environnement, Institut de Chimie de Nice (CNRS, FR 3037), University of Nice Sophia-Antipolis, Faculty des Sciences, Parc Valrose, 06108 Nice Cedex 2, France
2Department of Pharmaceutical Sciences, University of Antwerp (Campus Drie Eiken), Universiteitsplein 1, 2610 Antwerp, Belgium
3Plate-forme Technologique-Spectrométrie de Masse, Institut de Chimie de Nice, Université de Nice Sophia-Antipolis, Parc Valrose, 06108 Nice Cedex 2, France
4Department of Analytical Chemistry, Institute for Nuclear Sciences, Ghent University, Proeftuinstraat 86, 9000 Gent, Belgium
Abstract. Aqueous-phase oligomer formation from methylglyoxal, a major atmospheric photooxidation product, has been investigated in a simulated cloud matrix under dark conditions. The aim of this study was to explore an additional path producing secondary organic aerosol (SOA) through cloud processes without photochemistry during night-time. Indeed, atmospheric models still underestimate SOA formation, as field measurements have revealed more SOA than predicted. Soluble oligomers (n=1–8) formed in the course of acid-catalyzed aldol condensation and acid-catalyzed hydration followed by acetal formation have been detected and characterized by positive and negative ion electrospray ionization mass spectrometry. Aldol condensation proved to be a favorable mechanism under simulated cloud conditions, while hydration/acetal formation was found to strongly depend on the pH of the system. The aldol oligomer series starts with a β-hydroxy ketone via aldol condensation, where oligomers are formed by multiple additions of C3H4O2 units (72 Da) to the parent β-hydroxy ketone. Ion trap mass spectrometry experiments were performed to structurally characterize the major oligomer species. A mechanistic pathway for the growth of oligomers under cloud conditions and in the absence of UV-light and OH radicals, which could substantially enhance in-cloud SOA yields, is proposed here for the first time.
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Notice on Discussion StatusCitation: Yasmeen, F., Sauret, N., Gal, J. F., Maria, P.-C., Massi, L., Maenhaut, W., and Claeys, M.: Characterization of non-photochemically formed oligomers from methylglyoxal: a pathway to produce secondary organic aerosol through cloud processing during night-time, Atmos. Chem. Phys. Discuss., 9, 22993-23020, doi:10.5194/acpd-9-22993-2009, 2009. Bibtex EndNote Reference Manager XML
