Modeling the formation of secondary organic aerosol within a comprehensiveair quality model system

The Secondary Organic Aerosol Model (SORGAM) has-been developed for use in comprehensive air quality model systems. Coupled to a chemistry-transport m odel, SORGAM is capable of simulating secondary organic aerosol (SOA) forma tion including the production of low-volatility products and their subseque nt gas/particle partitioning. The current model formulation assumes that al l SOA compounds interact and form a quasi-ideal solution. This has signific ant impact on the gas/particle partitioning, since in this case the saturat ion concentrations of the SOA compounds depend on the composition of the SO A and the amount of absorbing material present. Box model simulations have been performed to investigate the sensitivity of the model against several parameters. Results clearly show the importance of the temperature dependen ce of saturation concentrations on the partitioning process. Furthermore, S ORGAM has been coupled to the comprehensive European Air Pollution and Disp ersion/Modal Aerosol Dynamics Model for Europe air quality model system, an d results of a three-dimensional model application are presented. The model results indicate that assuming interacting SOA compounds, biogenic and ant hropogenic contributions significantly influence each other and cannot be t reated independently.