Significant formation of sulfate aerosols contributed by the heterogeneous drivers of dust surface

Abstract. The importance of dust heterogeneous chemistry in the removal of atmospheric SO₂ and formation of sulfate aerosols is not adequately understood. In this study, the Fe, Ti, Al-bearing components, Na⁺, Cl^-, K⁺, and Ca²⁺ of the dust surface were discovered to be closely associated with the heterogeneous formation of sulfate. Regression models were then developed to accurately predict the heterogeneous reactivity by the particle chemical compositions. Further, the recognized gas-phase, aqueous-phase and heterogeneous oxidation routes were quantitatively assessed and kinetically compared by combining the laboratory work with modeling study. In the presence of 55 μg m^-3 airborne dust, heterogeneous chemistry accounts for approximately 28.6 % of the secondary sulfate aerosols during nighttime, while the proportion decreases to 13.1 % in the presence of solar irradiation. On the dust surface, heterogeneous drivers (e.g. transition metal constituents, water-soluble ions) are more efficient than surface adsorbed oxidants (e.g. H₂O₂, NO₂, O₃) in the conversion of SO₂, particularly during nighttime. Dust heterogeneous chemistry offers an opportunity to explain the missing sulfate source during severe haze pollution events, and its contribution proportion in the complex atmospheric environments could be even higher than the current calculation results. Overall, the dust surface drivers are responsible for the significant formation of sulfate aerosols and have profound impacts on the atmospheric sulfur cycling.