Water is a major constituent of the ambient atmosphere, and much attention has been given to both the hygroscopicity of particles and mechanisms by which secondary organic aerosol (SOA) can be formed in aqueous cloud droplets.  Relatively little attention, however, has been given to the influence of water on the chemical and physical properties of SOA, the effects of water on organic particulate matter (OPM) levels, and the partitioning of polar low molecular weight organic compounds to mostly organic PM phases.  In fact, water can have large effects on the mass amounts and spatiotemporal distribution of SOA formed, and on the radiative properties of SOA.  It exerts its effects by modifying: 1) the activity coefficients and/or reactivities of the partitioning organic compounds; and 2) the mean molecular weight, polarity, and/or viscosity of the absorbing organic phase(s).  This work considers the theoretical formalisms behind the effects of water, as well as computationally feasible approaches for their treatment in three-dimensional air quality models.  Model predictions of SOA considering the effects of water will be presented and the resultant atmospheric implications discussed.

Effects of water on secondary organic aerosol

248th National Meeting (2014)

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