PNNL

Abstract

Mounting evidence demonstrates that under certain conditions the rate of component partitioning between the gas- and particle-phase in atmospheric organic aerosol is limited by particle-phase di?usion. To date, however, particle-phase di?usion has not been incorporated to regional atmospheric models. An analytical rather than numerical solution to di?usion through organic particulate matter is desirable because of its comparatively small computational expense in regional models. Current analytical models assume di?usion to be independent of composition, and therefore use a constant di?usion coe?cient. To realistically model di?usion, however, it should be composition-dependent (e.g. due to the partitioning of components that plasticise, vitrify or solidify). This study assesses the modelling capability of an analytical solution to di?usion corrected to account for composition dependence against a numerical solution. Results show reasonable agreement when the gas-phase saturation ratio of a partitioning component is constant and particle-phase di?usion limits partitioning rate (