A New Source of Sulfates in the Atmosphere

Monitoring data on sulfates in atmospheric haze particles over Beijing in winter 2016 are considered. It is found that the source of sulfates in humidified haze particles is the catalytic oxidation of sulfur dioxide by molecular oxygen involving ions of transition metals \({\text{(S}}{{{\text{O}}}_{{{\text{2}}{\kern 1pt} {\text{(gas)}}}}}\xrightarrow{{{{{\text{Mn}}} \mathord{\left/ {\vphantom {{{\text{Mn}}} {{\text{Fe}}}}} \right. \kern-0em} {{\text{Fe}}}}{\text{,}}{{{\text{O}}}_{{\text{2}}}}}}{\text{SO}}_{{4({\text{aq}})}}^{{2 - }})\) proceeding in a branched mode. Concentration conditions of this process and the features of its dynamics in the atmosphere are discussed. The agreement between the calculated content of \({\text{SO}}_{{4({\text{aq}})}}^{{2 - }}\) in particles and monitoring data indicates that a branched mode of catalytic conversion of SO_{2 (gas)} in the atmosphere exists and represents a new source of sulfates. This fast nonphotochemical channel should be taken into account in inventory system of sulfate sources in the global atmosphere.