Sulfate is one of the main components of the haze particles and the formation mechanism remains controversial. Lacking of detailed and comprehensive field data hindes the accurate evaluation of relative roles of prevailing sulphate formation pathways. Here, we analyzed the sulfate production rates using a state-of-art multiphase model constrained to the observed concentrations of transition metal ions (TMI), nitrogen dioxide, ozone, hydrogen peroxide, and other important parameters in winter and summer in the North China Plain. Our results showed that aqueous TMI-catalyzed oxidation was the most important pathway followed by the surface oxidation of Mn in both winter and summer, while the hydroxyl and criegee radicals oxidations contribute significantly in summer. In addition, we also modeled the published cases for the fog and cloud conditions. It is found that nitrogen dioxide oxidation is the dominant pathway for the fog in a higher pH range while hydroperoxide and ozone oxidations dominated for the cloud.
 

sulfate formation,transition metal ions,field observation,radicals