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

Abstract

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.