Oxidation of Organic Sulfur at the Air–Water Interface of Microdroplets: A New Way of Atmospheric Particle Precursor Formation

Dimethyl sulfide (CH₃SCH₃), methanethiol (CH₃SH), and dimethyl disulfide (CH₃SSCH₃) are the most predominant marine organic sulfur compounds that drive cloud formation by acting as a critical precursor of cloud condensation nuclei. However, discrepancies of natural aerosol radiative effects and climatic impacts between climate model simulations and satellite observations highlight an incomplete understanding of organic sulfur oxidation pathways. Here, we demonstrate a previously unrecognized rapid oxidation mechanism at the air-water interface of microdroplets, where volatile sulfides convert to particle precursors within milliseconds. Combining DFT calculation, QM/MM simulation, and sequential oxidation of possible intermediates, we proposed a new pathway of atmospheric particle precursor formation at the air-water interface of microdroplets, which is different from the traditional gas-phase oxidation pathway, offering a mechanistic solution to re-evaluate the model simulation gaps in natural aerosol radiative effects and climatic impacts.