A comparison of fenuron degradation by hydroxyl and carbonate radicals in aqueous solution.
A comparative study of the transformation of the herbicide fenuron (1,1-dimethyl-3-phenylurea) by hydroxyl radicals and carbonate radicals in aqueous solution (pH 7.2-phosphate buffer) has been undertaken. Hydroxyl radical was generated by the well-known photolysis of hydrogen peroxide at 254 nm and carbonate radical was formed by photolysis of Co(NH(3))(5)CO(3)(+) at 254 nm. Competitive kinetic experiments were performed with atrazine used as the main competitor for both processes. Accordingly, the second-order rate constant of reaction between fenuron and carbonate radical was found to be (7-12+/-3)x10(6)M(-1)s(-1) [(7+/-1)x10(9)M(-1)s(-1) for hydroxyl radical]. The formation of degradation products was studied by LC-MS in the two cases and a comparison has been performed. The reaction with carbonate radical leads to the formation of a quinone-imine derivative which appears as the major primary product together with ortho and para hydroxylated compounds. These two compounds represent the major products in the reaction with hydroxyl radicals. The reaction of both radicals also leads to the transformation of the dimethylurea moiety.
Laboratoire de Chimie de l'Eau et de l'Environnement, UMR CNRS 6008, Université de Poitiers ESIP, 40 Avenue du Recteur Pineau, Poitiers Cedex, France. patrick.mazellier@univ-poitiers.fr
Patrick
P
Mazellier
Cécile
C
Busset
Anne
A
Delmont
Joseph
J
De Laat
D002254:Carbonates / Q000737:chemistry*; D003035:Cobalt / Q000528:radiation effects; D005609:Free Radicals / Q000737:chemistry*; D006540:Herbicides / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000528:radiation effects; D017665:Hydroxyl Radical / Q000737:chemistry*; D007700:Kinetics; D009566:Nitrates / Q000528:radiation effects; D010671:Phenylurea Compounds / Q000737:chemistry*; D010782:Photolysis; D012996:Solutions; D014466:Ultraviolet Rays; D014874:Water Pollutants, Chemical / Q000737:chemistry
D002254:Carbonates; D005609:Free Radicals; D006540:Herbicides; D009566:Nitrates; D010671:Phenylurea Compounds; D012996:Solutions; D014874:Water Pollutants, Chemical; D017665:Hydroxyl Radical; D003035:Cobalt; D006861:Hydrogen Peroxide; C010727:fenuron