Oxidation of Organic Compoundsin the Atmospheric Aqueous Phase: Development of a New Explicit Oxidation Mechanism

Friday, 19 December 2014: 3:08 PM
Camille Mouchel-Vallon1,2, Lola Bregonzio-Rozier3, Anne Monod4, Maud Leriche2,5, Jean-Francois Doussin6, Nadine M Chaumerliac1,2 and Laurent Deguillaume1, (1)Laboratoire de Météorologie Physique Observatoire de Physique du Globe de Clermont-Ferrand, Aubiere Cedex, France, (2)CNRS, Paris Cedex 16, France, (3)Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA), CNRS UMR7583, Universités Paris-Est Créteil et Paris Diderot, Institut Pierre Simon Laplace (IPSL), Créteil, France, (4)Aix Marseille University, Marseille Cedex 03, France, (5)Laboratoire d'Aérologie - Observatoire Midi Pyrénées, Toulouse, France, (6)University Paris-Est Créteil Val de Marne, Créteil Cedex, France
Current 3D models tend to underestimate the production of secondary organic aerosol (SOA) in the atmosphere (Volkamer et al., 2006). Recent studies argue that aqueous chemistry in clouds could be responsible for a significant production of SOA (Ervens et al., 2011; Carlton and Turpin, 2013) through oxidative and non-oxidative processes. Aqueous phase reactivity of organic compounds needs to be thoroughly described in models to identify organic molecules available to contribute to SOA mass.

Recently, new empirical methods have been developed to allow the estimate of HO·reaction rates in the aqueous phase (Doussin and Monod, 2013, Minakata et al., 2009). These methods provide global rate constants together with branching ratios for HO·abstraction and addition on organic compounds of atmospheric interests. Current cloud chemistry mechanisms do not take the different possible pathways into account. Based on these structure-activity relationships, a new detailed aqueous phase mechanism describing the oxidation of hydrosoluble organic compounds resulting from isoprene oxidation is proposed.

This new aqueous phase mechanism is coupled with the detailed gas phase mechanism MCM v3.2 (Jenkin et al., 1997; Saunders et al., 2003) through a kinetic of mass transfer parameterization for the exchange between gas phase and aqueous phase. The GROMHE SAR (Raventos-Duran et al., 2010) allows the evaluation of Henry's law constants for organic compounds. Variable photolysis in both phases using the TUV 4.5 radiative transfer model (Madronich and Flocke, 1997) is also calculated.

The resulting multiphase mechanism has been implemented in a cloud chemistry model. Focusing on oxygenated compounds produced from the isoprene oxidation, sensitivity tests and comparisons with multiphase experiments performed in the framework of the CUMULUS project in the CESAM atmospheric simulation chamber (Wang et al., 2011) will be presented.

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