Introduction 4116 2. Theoretical Background and Framework for Atmospheric Aerosols 4117 2.1. Saturation Vapor Pressures 4117 2.2. Vapor−Liquid or Vapor−Solid Equilibria over Mixed Solutions 4118 2.3. Equilibria over Curved Surfaces 4118 2.4. Dynamic Evaporation and Condensation from and to an Aerosol Particle 4119 2.5. Ambient Partitioning 4120 3. Experimental Methods 4120 3.1. Knudsen-Cell-Based Methods 4121 3.1.1. Knudsen Mass Loss Methods 4121 3.

Abstract. A selection of models for estimating vapour pressures have been tested against experimental data for a set of compounds selected for their particular relevance to the formation of atmospheric aerosol by gas-liquid partitioning. The experimental vapour pressure data (all <100 Pa) of 45 multifunctional compounds provide a stringent test of the estimation techniques, with a recent complex group contribution method providing the best overall results. The effect of errors in vapour pressures upon the formation of organic aerosol by gas-liquid partitioning in an atmospherically relevant example is also investigated. The mass of organic aerosol formed under typical atmospheric conditions was found to be very sensitive to the variation in vapour pressure values typically present when comparing estimation methods.

Abstract. Solid state vapour pressures of a selection of atmospherically important substituted dicarboxylic acids have been measured using Knudsen Effusion Mass Spectrometry (KEMS) over a range of 20 K (298-318 K). Enthalpies of fusion and melting points obtained using Differential Scanning Calorimetry (DSC) were used to obtain sub-cooled liquid vapour pressures. They have been compared to estimation methods used on the E-AIM website. These methods are shown to poorly represent -OH groups in combination with COOH groups. Partitioning calculations have been performed to illustrate the impact of the different estimation methods on organic aerosol mass compared to the use of experimental data.

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