Mass spectrometry of interfacial layers during fast aqueous aerosol/ozone gas reactions of atmospheric interest

The rapid oxidation of sulfite and/or iodide in the interfacial layers of aqueous microdroplets during brief (∼1 ms) exposure to O3(g) are investigated by mass spectrometry of the ejected anions. I− partially excludes HSO3- from the interfacial layers of equimolar (Na2SO3 + NaI) microdroplets, where it is oxidized without apparent depletion in a process mediated by a persistent ISO3- intermediate. Present results provide unambiguous evidence of distinct interfacial chemistry in gas-aerosol reactions of atmospheric relevance.