Direct and indirect photolysis of cyhalofop in aqueous systems.
The photodegradation of the aryloxyphenoxy propionic herbicide cyhalofop-butyl (2R)-2-[4-(4-cyano-2-fluorophenoxy)phenoxy]butylpropanoate (CyB), and of its primary metabolite (2R)-2-[4-(4-cyano-2-fluorophenoxy)phenoxy]propanoic acid (CyA) was studied in water at different irradiation wavelengths. The sunlight irradiation was investigated also in the presence of humic acid (HA), Fe oxide, titanium dioxide (TiO2) and zinc oxide (ZnO) as photocatalysts. CyB and CyA were rapidly degraded by UV irradiation. CyB afforded the butyl ester of 2-[3-(4-cyano-2-fluorophenyl)-4-hydroxy-phenoxy]propanoic acid (CyI), a metabolite arising from a photo-Fries rearrangement. Instead, CyA yielded (R)-2-4-(4-carboxyl-2-fluorophenoxy)phenoxypropanoic acid (CyD), a dicarboxylic acid arising from the photo-hydrolysis of cyano group via amide. CyB was stable in simulated sunlight also in the presence of the catalysts tested. The irradiation of a CyA solution, in the presence of HA or Fe oxide, with simulated sunlight did not produce any significant degradation. In the same experimental conditions, CyA was totally mineralized in the presence of TiO2 and ZnO.
Dipartimento di Scienze Ambientali Agrarie e Biotecnologie Agro-Alimentari, Desertification Research Group (NRD), Università di Sassari, Viale Italia 39, 07100 Sassari, Italy.
Maria Vittoria
MV
Pinna
Alba
A
Pusino
D002073:Butanes / Q000032:analysis / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry; D006540:Herbicides / Q000032:analysis / Q000737:chemistry*; D009570:Nitriles / Q000032:analysis / Q000737:chemistry*; D010782:Photolysis; D017550:Spectroscopy, Fourier Transform Infrared; D014025:Titanium / Q000737:chemistry; D014466:Ultraviolet Rays; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry*; D015034:Zinc Oxide / Q000737:chemistry
D002073:Butanes; D005290:Ferric Compounds; D006540:Herbicides; D009570:Nitriles; D014874:Water Pollutants, Chemical; C009495:titanium dioxide; C501583:cyhalofop-butyl; C000499:ferric oxide; D014025:Titanium; D015034:Zinc Oxide