Photo-induced OH reactions of naphthalene and its oxidation products on SiO2

The photo-induced degradation of naphthalene, I,4-naphthoquinone, l-naphtho l and 1-NO2 naphthalene, adsorbed on silica gel, and with the addition of n itrogenous air pollutants e.g. NO2- (as KNO2) was investigated. Results ind icate that compounds adsorbed onto a solid carrier are degraded when irradi ated with UV light (lambda > 290 nm) in the presence of nitrites. The key s pecies initiating the naphthalene degradation is the OH-radical which is ge nerated through the photolysis of NO2-. Reaction products identified were 2 -formyl-cinnamaldehyde, 1,4-naphthoquinone, nitronaphthol, o-phthaldialdehy de, phthalide and nitronaphthalene. A mass balance between 40 - 50% was ach ieved. Under the same irradiation conditions, 1-NO2 naphthalene is mainly degraded by direct photolysis while degradation of 1-naphthol and 1,4-naphthoquinon e proceeds via the reaction with OH-radicals. Identified products were hydr oxy- nitro- nitroso- and quinones compounds.