| Abstract
| - The photolysis of propiconazole in pure water, in water containing humic substances, and in naturalwater was investigated. The reaction rates were determined, and the main photoproducts wereidentified with the help of HPLC−mass spectrometry and by NMR. The quantum yield for directphotolysis was 0.11 ± 0.01 at the maximum of absorption (269 nm). Photocyclization after HClelimination and photohydrolysis of the cyclized intermediate were the main reaction pathways at254 nm. By contrast, oxidation prevailed over dechlorination in simulated or natural solar light.Humic substances (10 mg·L-1) and naturally occurring chromophores contained in natural waterenhanced the rate of propiconazole photodegradation in solar light. Half-life in June in Clermont-Ferrand (latitude 46°N) 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 photolysisand photoinduced reactions. Keywords: Propiconazole; direct photolysis; photoinduced transformation; humic substances;natural water; solar light
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