Photo-induced degradation of diuron in aqueous solution by nitrites and nitrates:: Kinetics and pathways

The photo-induced degradation of diuron (3-(3,4-dichlorophenyl)-1,1-dimethylurea) in aqueous solution under simulated solar irradiation has been investigated in the presence of NO3-/NO2- ions. The degradation rates were compared by varying environmental parameters including substrate and inducer concentrations, oxygen content and pH. The photoproducts were identified by extensive LC-ESI-MS and LC-ESI-MS-MS studies after SPE preconcentration on prepacked cartridges. In both NO3- and NO2- conditions, oxidation of the N-(CH3)(2) terminus group is the main process leading to the N-monodemethylated (NHCH3) N-formyl (N(CH3)CHO) and the uncommon and unstable carbinolamine (N(CH3)CH2OH) by-products. Cl/OH substituted and nitrated phenylureas are formed minorily. Degradation pathways involving OH center dot and NO2 (or dimer) radicals as reactive species are proposed. (c) 2006 Elsevier Ltd. All rights reserved.