Assessment of vapor pressure estimation methods for secondary organic aerosol modeling

Vapor pressure (Pvap) is a fundamental property controlling the gas–particle partitioning of organic species. Therefore this pure substance property is a critical parameter for modeling the formation of secondary organic aerosols (SOA). Structure–property relationships are needed to estimate Pvap because (i) very few experimental data for Pvap are available for semi-volatile organics and (ii) the number of contributors to SOA is extremely large. The Lee and Kesler method, a modified form of the Mackay equation, the Myrdal and Yalkowsky method and the UNIFAC- method are commonly used to estimate Pvap in gas–particle partitioning models. The objectives of this study are (i) to assess the accuracy of these four methods on a large experimental database selected to be representative of SOA contributors and (ii) to compare the estimates provided by the various methods for compounds detected in the aerosol phase.