Global Impacts of Phase State on Secondary Organic Aerosol Partitioning

This project is focused on studying the effects of the phase state (e.g., gas-particle partitioning) of secondary organic aerosol (SOA) on atmospheric processes at regional or global scales. The parameterizations that will be developed can help to predict multiphase chemistry processes and aerosol composition and concentration. The ultimate goal of this research is to evaluate the global impacts of phase state on atmospheric aerosol processes to better predict the aerosol effects on climate, air quality and public health. Current large-scale SOA models represent aerosol physicochemical processes using highly simplified schemes with equilibrium gas-particle partitioning. This project will evaluate under which conditions and to what extent these assumptions may or may not hold in the global atmosphere. The tasks to accomplish this goal are as follows: (1) Implement a method in the GEOS-Chem model to predict glass transition temperatures and the viscosity of SOA; (2) Derive the equilibration timescales of SOA partitioning and water uptake in global atmosphere using kinetic multilayer modeling; (3) Apply a scheme of kinetic partitioning of SOA with effective mass accommodation coefficients to consider the effects of phase state; and (4) Evaluate model predictions of the SOA budget and phase state against observations. The new aerosol phase state developments will contribute to improvements of the public version of the GEOS-Chem model and will be openly available for all users. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.