PHOTODEGRADATION OF METOLACHLOR IN WATER IN THE PRESENCE OF SOIL MINERAL AND ORGANIC-CONSTITUENTS

Photodegradation of metolachlor hylphenyl)-N-(2-methoxy-1-methylethyl) --acetamide] at 253.7 nm was carried out in water containing soil mine rals (kaolinite, montmorillonite, and goethite) and fulvic acid under two different pH conditions. The rate of photolysis was dependent on t he nature of the soil constituents and the initial pH of the medium. B ased on the regression analysis, it was shown that the photodegradatio n followed the first-order kinetics with respect to the metolachlor co ncentration, and the half-life of the herbicide under UV irradiation w as longer in the absence of soil constituents. Hydroxylation, dehaloge nation, oxoquinoline formation, and demethylation were the main proces ses observed during the photolysis of metolachlor. More degradation pr oducts were formed in the presence of kaolinite, montmorillonite, and goethite than with fulvic acid and water alone. The major degradation product formed under UV irradiation in all the treatments was identifi ed as 4-(2-ethyl-6-methylphenyl)-5-methyl-3-morpholine.