Mutual Impact of Mineral and Organic Components in Atmospheric Aerosol

The effect of ammonium sulfate ((NH4)2SO4) on the condensation of low-volatile organic compounds in atmospheric aerosol is considered. Using the UNIFAC model, a physicochemical analysis has been conducted for the condensation of ISNP—a product of photochemical transformations of isoprene and α-pinene in the atmosphere. The variability of the mass content of ISNP, mass concentration of aerosol particles, and their phase state at different temperatures (T) and relative humidities (RH) have been calculated. Transition of the organic component into the aqueous phase of ammonium sulfate particles is observed only at certain combinations of T and RH. In comparison with condensation in the absence of ammonium sulfate, the ISNP content at given T and RH can be lower or higher. The results of calculations indicate that the newly forming particles of mixed composition are characterized by a higher hygroscopicity and a higher capacity to be converted into drops (miscible liquid phase) at an air humidity lower than for particles that contain only ammonium sulfate.