Fig. 2: Contribution (%) of secondary sulfate production in each pathway.

Twenty-four-hour model simulations of sulfate formation for homogeneous (gas-phase hydroxyl radical OH and stabilized Criegee intermediates, sCIs), multiphase (hydrogen peroxide \({{\rm{H}}}_{2}{{\rm{O}}}_{2}\), NO₂, O₃, transitional-metal ion catalytic TMI (Mn(II)+Fe(III)) + O₂, and the photosensitization T^* and nitrate photolysis pNO₃⁻), and heterogeneous oxidation pathway including black carbon (BC), brown carbon (BrC), sea salt (SS) as well as mineral dust (MD) during the nighttime and daytime hours in typical dust storm-relevant conditions (a). Specific contribution percentage of each way to overall sulfate production in the absence (b) and presence (c) of carbonate salt during the nighttime period as well as that in the absence (d) and presence (e) of carbonate salts during the daytime period. Parameters such as SO₂ concentrations, RHs, etc. were obtained from meteorological station measurements, which are available in Fig. S2. The comparison between heterogeneous dust pathways to the recently proposed reaction channel of high sulfate production rates using the latest SO₂ oxidation kinetics in dust storm scenario (f), with a high concentration of H₂O₂ adopted in these calculations. The lower and upper limits of sulfate production rates for the dust pathway refer to the nighttime and daytime conditions. The high ionic strength of 10 M was adopted for all calculations, with detailed input summarized in Supplementary Table S6. “hD” refers to “half-day”. We adopted the latest CO₃^∙−-relevant kinetics that was determined using a range of authentic dust and clay particles instead of using predicted kinetics in early publication (Liu et al.⁹). pH-dependent concentrations of [Fe (III)] and [Mn (II)] were applied using the parameters described elsewhere (Cheng et al.²²).