The size and chemical composition of organic aerosol (OA) varies with uptake of water and reactive chemical species, processes that may be inhibited in highly viscous aerosol. Accordingly, proper parameterization of OA viscosity is necessary for accurate treatment of OA radiative interactions in climate models. A model to describe the temperature- and humidity-dependent viscosity of aqueous sucrose aerosol, a common laboratory proxy for viscous OA, has been developed based upon a modified Vogel-Fulcher-Tammann equation, the Gordon-Taylor mixing rule, and a mass-based hygroscopicity parameterization and is presented. This model is further extended to multicomponent aqueous mixtures. The model was constrained with particles that contain either a second organic species (citric acid) or a hygroscopic inorganic salt (sodium nitrate) in addition to sucrose. Fitted parameters for these models were derived using new viscosity measurements of bulk aerosol collected via a coalescence timescale-based method and existing literature bulk glass transition data.

Phase diagrams of internally mixed aqueous nanoscale organic aerosols

254th National Meeting (2017)

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