Unveiling the Role of Carbonate Radical Anions in Dust-Driven SO₂ Oxidation

Carbonate radical anion (CO3 center dot-) is generally overlooked in atmospheric chemistry. Our recent work emphasizes the important role of carbonate radicals produced on mineral dust surfaces in fast sulfate production under solar irradiation in the presence of CO2 at specifically low RH and light intensity. Yet so far how CO3 center dot- involves and affects secondary sulfate production under diverse RH, light intensity, and complex constituent matrix remains unknown, which essentially limits our comprehensive knowledge of CO(3)(center dot-)initiated SO2 oxidation scheme in the atmosphere. Herein, we explored the heterogeneous SO2 oxidation over both model and authentic dust and clays in the presence of CO2 at atmospheric relevant RHs and light intensities. Interestingly, we observe that CO2 promotes sulfate yield over authentic dust and clays at atmospheric-relevant RH and light intensity. This observation relates to the favorable kinetic between SO2 oxidation and CO3 center dot- while auto-quenching of these radical ions is largely minimized due to the sufficient sites of crustal constituents. Furthermore, employing a suite of authentic dust and machine learning strategies, we evaluated the relative importance of each constituent within airborne minerals or clays as well as environmental conditions including relative humidity, light intensity, and CO2 concentration in affecting SO2 uptake capability. On this basis, sulfate formation mediated by dust-driven pathway, accounting for nearly similar to 20.9% of overall contribution by the end of this century during some pollution episodes, even higher than gas-phase center dot OH (similar to 16.9%), will be increased by 163% if CO2-initiated SO2 oxidation scheme is incorporated. Plain Language Summary How carbonate radical ions involve and affect sulfate formation under different RHs, light intensities, and complex component matrices remains an open question. Secondary sulfate production is facilitated by CO3 center dot- over authentic dust particles in atmospheric relevant RH and light intensity. More importantly, this research emphasizes that CO2 is not an inert greenhouse gas that rarely participates in atmospheric chemistry but a strong oxidant precursor that will produce CO3 center dot- and subsequently trigger quick SO2 oxidation via chain reactions. This dust-driven reaction channel mediated by CO3 center dot- potentially contributes to nearly similar to 1/5 of secondary sulfate production during some pollution hours if the growing intensive anthropogenic activities continue.