We report the effects of actinic illumination on theheterogeneous ozonation kinetics of solid pyrene films and pyrene adsorbedat air-octanol and air-aqueous interfaces. Upon illumination, theozonation of solid pyrene films and pyrene at the air-aqueous interfaceproceeds more quickly than in darkness; no such enhancement is observed forpyrene at the air-octanol interface. Under dark conditions, the reaction ofpyrene at all three interfaces proceeds via a Langmuir-Hinshelwood-typesurface mechanism. In the presence of light, Langmuir-Hinshelwood kineticsare observed for solid pyrene films but a linear dependence upon gas-phaseozone concentration is observed at the air-aqueous interface. We interpretthese results as evidence of the importance of charge-transfer pathways forthe ozonation of excited-state pyrene. The dramatically different behaviourof pyrene at the surface of these three simple reaction environmentshighlights the difficulties inherent in representing complex reactivesurfaces in the laboratory, and suggests caution in extrapolating laboratoryresults to environmental surfaces.
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