Phototransformation of Propiconazole In Aqueous Media

Abstract

The photolysis of propiconazole in pure water, in water containing humic substances, and in natural water was investigated. The reaction rates were determined, 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 main reaction pathways at 254 nm. By contrast, oxidation prevailed over dechlorination in simulated or natural solar light. Humic substances (10 mg x L(-)(1)) and naturally occurring chromophores contained in natural water enhanced the rate of propiconazole photodegradation in solar light. Half-life in June in Clermont-Ferrand (latitude 46 degrees 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 photolysis and photoinduced reactions.

The role of indirect photolysis in limiting the persistence of crop protection products in surface waters

“…Both compounds were, however, degraded in all of the tested surface waters, illustrating the capacity of indirect photolysis to mediate the degradation of CPPs stable to direct photolysis, and which would otherwise be deemed to be persistent. For propiconazole, DT50 ranged from 5 d (Nebraska 04, April) (the numbers are a reference to the site of collection, not the month) to 104 d (Tennessee 01, April); these values were notably longer than those previously reported [24]. The half-life of prometryn ranged from 16 d (Illinois 04, April and Illinois 08, April) to 109 d (Indiana 01, August), which corresponded with 50 d reported for photodegradation in a river and lake water samples from Greece [18].…”

Aquatic Phototransformation of Organic Contaminants Induced by Coloured Dissolved Natural Organic Matter

“…Propiconazole (1-[2-(2,4-dichlorophenyl)-4-propyl-1,3-dioxolan-2-ylmethyl]-1H-1,2,4-triazole) (XII), which is used as a fungicide, was found to undergo different types of reaction in pure water depending on the wavelength of irradiation [73]. Photocyclization after HCl elimination to give XIIa (see Scheme 12) The photodegradation of XII was enhanced by humic substances (10 mg L -1 ) or in a natural water sampled in a dam (Villerest, France) (7.2 mg C L -1 ).…”

Phototransformation of nitrobenzene in the Songhua River: Kinetics and photoproduct analysis

“…Among the different transformation processes (abiotic and biotic), photodegradation is an important one influencing the fate of organic pollutants (Zafiriou et al, 1984). The phototransformation of a pollutant in the hydrosphere may result from light absorption by the pollutant itself (direct photolysis) or may be photoinduced by the dissolved organic matters (DOMs) or nitrate ions present in water, as these chromophores are known to photoproduce reactive species (indirect photoly-sis) (Vialaton et al, 2001). Because NB absorbs sunlight strongly in the ultraviolet and blue spectral region, it is considered that direct photolysis might play an important role for the degradation of NB in aqueous systems.…”