Photolysis of fluometuron in the presence of natural water constituents

Phototransformation of the herbicide fluometuron (1 μM) in natural sunlight was investigated in neutral Milli-Q water and in synthetic waters containing either fulvic acids, nitrate ions or both in order to mimic reactions taking place in aquatic environments. Fluometuron degradation followed a pseudo-first order kinetics. The reaction was faster in synthetic than in Milli-Q water. Fulvic acids (10 mg l−1) increased the rate of fluometuron photolysis by a factor 2.5 and nitrates (25 mg l−1) by a factor 15. Identification of major photoproducts was conducted under laboratory conditions using LC–ESI–MS. Numerous photoproducts were detected and tentatively characterized. In the presence of nitrates, hydroxylation of the aromatic ring with or without hydrolysis of CF3 into CO2H and oxidation of the urea chain leading to demethylation were observed. In the presence of fulvic acids, hydroxylation of the aromatic ring was the major reaction route.