Modeling the chemistry of organic compounds

Partitioning between gas and aerosol phase

In order to model partitioning between gas phase and condensed phase of oxidation products, the partitioning equilibrium constant is calculated, based on estimates of the saturated vapour pressure of condensable organic compounds, as for most species direct experimental data are not available. The method of Capouet and Müller (2006) was compared with several other vapour pressure methods (Compernolle et al. 2010). A new method named EVAPORATION, which contains more detail and considers important structural effects and fusion properties ( Compernolle et al. 2011a), was presented in Compernolle et al. (2011b), and was found to compare well with existing methods for atmospherically relevant species. A web-application was designed for use of the EVAPORATION method.

Previously most SOA modeling studies neglected the impact of non-ideality in the hydrocarbon mixtures of which SOA consists. Compernolle et al. (2009) extended existing activity coefficient estimation methods with atmospherically relevant groups such as nitrate and hydroperoxide, making these methods applicable for SOA modelling. It was shown that activity can have considerable impact on SOA mass, especially at higher relative humidity.

Fig.6b from Compernolle et al. 2011, EVAPORATION validation

Fig.6b from Compernolle et al. (2011), showing EVAPORATION mean average deviation against experimental results, compared with other vapour pressure estimation methods.