Atmospheric equilibrium model of sulfate and nitrate aerosols

Given local rates of production of gas-phase sulfate and nitrate, ammonia concentration, relative humidity and temperature, a model is presented that enables calculation of the quantity of sulfate/nitrate/ammonium/water aerosol, its precise chemical composition and physical state. The model is based on a complete thermodynamic chemical and phase equilibrium calculation for the sulfate/nitrate/ammonium system. Detailed simulations of sulfate/nitrate/ammonium aerosol evolution are presented, and recent ambient data from Tanner are interpreted. Some new results on temperature variation of activity coefficients are presented in the Appendix