Modeling the Composition of Organic Aerosol in the Atmosphere

A model of the formation of surrogate organic aerosol (OA) in the atmosphere upon the condensation of different volatility component is considered. The model takes into account the physical and chemical properties of individual components, determining their partial pressures over particles (Pi, atm) and hygroscopicity. The organic compounds (OCs) (components of surrogate particles) are taken to be organic peroxides and nitrates IALD, ISNP, and INPN, which are chemical transformation products of biogenic isoprene and α-pinene. The results of calculations (using the AIOMFAC model) reveal a complex character of the changes in activity coefficients (γi) of components for variations in the composition of OA. The surrogate particles were found to be significantly hygroscopic. The equilibrium composition of particles calculated from these data for the background atmosphere and taking into account their hygroscopicity and γi of components shows clearly expressed deviations from that found under the approximation that physical and chemical properties of particle ingredients are independent, which should be taken into account in the construction of models for the formation of real secondary OA in the atmosphere.