title: Degradation and by-product formation of diazinon in water during UV and UV/H(2)O(2) treatment.
abstract: Kinetics and degradation products resulting from the application of UV and UV/H(2)O(2) to the US EPA Contaminant Candidate List pesticide diazinon were studied. Batch experiments were conducted with both monochromatic (low pressure [LP] UV 253.7 nm) and polychromatic (medium pressure [MP] UV 200-300 nm) UV sources alone or in the presence of up to 50 mg l(-1) H(2)O(2), in a quasi-collimated beam apparatus. Degradation of diazinon by both UV and UV/H(2)O(2) exhibited pseudo first order reaction kinetics, and quantum yield of 8.6 x 10(-2) and 5.8 x 10(-2) mol E(-1) for LP and MP lamps respectively. Photolysis studies under MP UV lamp showed 2-isopropyl-6-methyl-pyrimidin-4-ol (IMP) to be the main degradation product of diazinon at aqueous solution pH values of 4, 7 and 10. Trace levels up to 1.8 x 10(-3) microM of diazinon oxygen analogue diethyl 2-isopropyl-6-methylpyrimidin-4-yl phosphate (diazoxon) were detected only during the UV/H(2)O(2) reaction. Decay of both products was observed, as the UV/H(2)O(2) reaction prolonged, yet no mineralization was achieved over the UV fluence levels examined. Photolysis kinetics, quantum yield and UV/H(2)O(2) degradation of the reaction product IMP was determined using MP UV lamp at pH values of 4, 7 and 10.
authors.affiliation: Department of Civil and Environmental Engineering, Duke University, 121 Hudson Hall Engineering Building, Box 90287, Durham, NC 27708-0287, USA.
authors.forename: Hilla
authors.initials: H
authors.lastname: Shemer
authors.forename: Karl G
authors.initials: KG
authors.lastname: Linden
mesh_terms: D003460:Crystallization; D003976:Diazinon / Q000737:chemistry* / Q000528:radiation effects; D006861:Hydrogen Peroxide / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007306:Insecticides / Q000737:chemistry* / Q000528:radiation effects; D007700:Kinetics; D010084:Oxidation-Reduction; D010573:Pesticide Residues / Q000737:chemistry* / Q000528:radiation effects; D010782:Photolysis; D014466:Ultraviolet Rays; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000528:radiation effects
chemical_list: D007306:Insecticides; D010573:Pesticide Residues; D014874:Water Pollutants, Chemical; D006861:Hydrogen Peroxide; D003976:Diazinon