An Experimental Study of the Atmospheric Oxidation of a Biogenic Organic Compound (Methyl Jasmonate) in a Thin Water Film as in Fog or Aerosols

Abstract

Experiments on the reactions of OH radicals in thin films of water were conducted in a photochemical reactor. The OH radical reactivity of a biogenic molecule (methyl jasmonate) was observed to be much larger in thin films of water than in the bulk aqueous phase. The pseudo-first order reaction rate was enhanced by an order of magnitude on a 38-micron film compared to the bulk liquid. However, the first order rate constant increased by 349%. This has implications in atmospheric systems like fog and mist which have large specific surface areas. The enhanced reactivity is attributable to both the partial solvation and faster diffusion at the air-water interface compared to the bulk liquid.

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“…Indeed, the first-order rate constant for the oxidation of methyl jasmonate is 3.5 times greater on a thin film than in bulk solution. 340 This dramatic increase likely occurs because methyl jasmonate is more exposed at the gas–liquid interface, where it is only partially solvated, and because diffusion is faster in the interfacial region than in the bulk.…”

“…6.3.2.1 OH + biogenic SOA components. OH readily reacts with methyl jasmonate, 340 which is a sparingly soluble plant VOC, and pinonic acid, 341,342 which is a derivative of a-pinene, at the gas-liquid interface. Indeed, the rst-order rate constant for the oxidation of methyl jasmonate is 3.5 times greater on a thin lm than in bulk solution.…”

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“…Heath et al [270] determined the pseudo-first-order rate constants for the reaction of MeJa with OH radicals in irradiated aqueous solution (bulk) and thin aqueous films. The OH radicals were generated by the photolysis of H 2 O 2 .…”