Phototransformation of propiconazole in aqueous media

The photolysis of propiconazole in pure water, in water containing humic su bstances, and in natural water was investigated. The reaction rates were de termined, and the main photoproducts were identified with the help of HPLC- mass spectrometry and by NMR. The quantum yield for direct photolysis was 0 .11 +/- 0.01 at the maximum of absorption (269 nm). Photocyclization after HCl elimination and photohydrolysis of the cyclized intermediate were the m ain reaction pathways at 254 nm. By contrast, oxidation prevailed over dech lorination in simulated or natural solar light. Humic substances (10 mg.L-1 ) and naturally occurring chromophores contained in natural water enhanced the rate of propiconazole photodegradation in solar light.,Half-life in Jun e in Clermont-Ferrand (latitude 46 degreesN) was found to be 85 +/- 10 h in pure water and 60 +/- 10 h in natural water; showing that photodegradation of propiconazole in natural waters involves both direct photolysis and pho toinduced reactions.