Investigations of main factors affecting tropospheric nitrate aerosol using a coupling model

Factors affecting tropospheric nitrate aerosol formation were investigated through a number of sensitivity studies using the thermodynamic equilibrium model ISORROPIA and the condensed gas-phase chemistry model. Results indicate that the equilibrium concentration of nitrate aerosol varies with solar zenith angle, air temperature, relative humidity, initial SO2 concentration, initial NO2 concentration and initial NH3 concentration. NH3 concentration and solar zenith angle play the most important roles, followed by relative humidity and NO2 concentration. It seems that the relations between nitrate aerosol and these four factors, as well as air temperature, are strong and highly nonlinear due to the coupling effect. The influence of SO2 concentration on nitrate aerosol is near-linear and weak.