Mass Spectrometric Detection of Oxidation Products and Intermediates of Aqueous Aerosol Iodide and/or Thiosulfate Reaction with Gaseous Ozone
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چکیده
The intermediates ISO3 (m/z = 207) and IS2O3 (m/z = 239) generated in aqueous (NaI/Na2S2O3) microdroplets traversing dilute O3 gas plumes are detected via online electrospray mass spectrometry within ~ 1 ms, and their stabilities gauged by collisionally induced dissociation. The simultaneous detection of anionic reactants and the S2O6, HSO4, IO3, and I3 products, as a function of experimental conditions, provides evidence for air-water interfacial reactions, as compared to strictly bulk aqueous reactions. For example, O3(aq) reacts ~ 3 times faster with I than with S2O3 in bulk solution; only S2O3 is significantly depleted in the interfacial layers of [I]/[S2O3] = 10 microdroplets below [O3(g)] ~ 50 ppm. This suggests that either interfacial kinetics are at variance with bulk aqueous kinetics and/or I mediates that ozone oxidation of S2O3.
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