Aqueous-phase photoreactions of substituted benzaldehydes and acetophenones as sinks for organic compounds as a source of HOOH in aqueous aerosols, fogs, and clouds: Effects of pH and of ring substituents
- Duke Univ., Durham, NC (United States)
Substituted benzaldehydes and acetophenones are present in the troposphere from combustion/oxidation of wood, biomass, gasoline, and municipal waste, and as structural moieties present in other atmospheric organic matter (e.g., terrestrial humic substances). Typical patterns of ring substitution include: 3,4-dimethoxy- and 3,4,5-trimethoxy-, I; 3-methoxy,4-hydroxy-, II; and 3-methyl- and 3,5-dimethyl-, III. Experiments in 1995 show that the photodegradation of the benzaldehydes/acetophenones, and the photoformation of HOOH is strongly dependent on pH: up to a 50-fold variation in quantum efficiencies/yields from pH 1.6-5.6. Ring substituents have a large effect on the mechanisms of the photoreactions. For example, I requires phenol as a reductant to form HOOH, while HOOH formation from II and III was relatively independent of phenol concentration. Proposed mechanisms (for I, II and III) for carbonyl photodestruction and HOOH photoformation will be discussed.
- OSTI ID:
- 369998
- Report Number(s):
- CONF-960376--
- Country of Publication:
- United States
- Language:
- English
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