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

Abstract

Abstract. The importance of dust heterogeneous oxidation in the removal of atmospheric SO2 and formation of sulfate aerosols is not adequately understood. In this study, the Fe-, Ti-, and 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 make a reliable prediction of the heterogeneous reactivity based on 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 a modelling study. In the presence of 55 µg m−3 airborne dust, heterogeneous oxidation 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 oxidation 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.

Modelling the European wind-blown dust emissions and their impact on PM concentrations

“…Also Kakavas and Pandis (2021) modelled increases of sulphates over Europe due to dust. Our findings, at least qualitatively, are also in line with the recent findings of Wang et al (2022) who argued that on the "dust surface, heterogeneous drivers are more efficient than surface-adsorbed oxidants in the conversion of SO 2 , particularly during nighttime".…”

“…Moreover, this study will also look at the secondary impact of WBD particles on secondary aerosol components focusing on the inorganic aerosol. Indeed, there is an indication that the composition of dust particles can have an indirect impact on nitrates, sulphates and ammonia (Fairlie et al, 2010;Karydis et al, 2011;Wang et al, 2012;Malaguti et al, 2015;Kakavas and Pandis, 2021;Wang et al, 2022) either by acting as a surface for heterogeneous reactions (e.g. Fu et al (2016); Wang et al (2022)) or by their ion composition and modulating aqueous reactions that form nitrates and sulphates (Kakavas and Pandis, 2021) representing an indirect pathway of impacting the overall PM levels.…”

“…Indeed, there is an indication that the composition of dust particles can have an indirect impact on nitrates, sulphates and ammonia (Fairlie et al, 2010;Karydis et al, 2011;Wang et al, 2012;Malaguti et al, 2015;Kakavas and Pandis, 2021;Wang et al, 2022) either by acting as a surface for heterogeneous reactions (e.g. Fu et al (2016); Wang et al (2022)) or by their ion composition and modulating aqueous reactions that form nitrates and sulphates (Kakavas and Pandis, 2021) representing an indirect pathway of impacting the overall PM levels. In this study, the main interest will be the quantification of WBD contribution to urban PM levels as urban areas already experience adverse air-pollution episodes and it is of interest to calculate how natural emissions like WBD can potentially contribute to urban PM concentrations.…”

Characteristics of PM2.5 and secondary inorganic pollution formation during the heating season of 2021 in Beijing

“…O 3 and RH were believed to be two factors in the formation of sulfate (Fang et al, 2019). Previous studies proposed that sulfate formation mechanisms in the atmosphere primarily include gas-phase oxidation of SO 2 by OH radicals and the Frontiers in Environmental Science frontiersin.org aqueous oxidation of S(IV) by H 2 O 2 , O 3 , organic peroxides, and NO 2 and catalytic oxidation by transition metal ions (TMIs), for example, Fe(III) and Mn(II), in cloud/fog water droplets (Li et al, 2020;Wang et al, 2021;Wang et al, 2022b;Wang et al, 2022c;Wang et al, 2022d;Gao et al, 2022;Ye et al, 2022). As sulfate itself exhibit strong hygroscopicity (Kong et al, 2020), with the increase in sulfate and RH, the PM 2.5 surface water content would increase, which would be more conducive to potential aqueous oxidation of S(IV), resulting in the increase in SOR.…”

Interaction of Acrylic Acid and SO2 on the Surface of Mineral Dust Aerosol

“…30−32 Rapid sulfate formation has been proven to play a major role in some of the smog events (e.g., London smog and Beijing smog). 29,33 Heterogeneous oxidation of SO 2 on water or solid particles is considered to be a potentially significant source of sulfate PM, 29 which can have profound effects on air quality and human health. 33 However, the concentration of sulfate in the existing model simulations is often lower than that in the field observations, and the sulfate formed by gas-phase and aqueous-phase oxidation is not enough to bridge the gap between model simulations and field observations.…”