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Photolysis behavior of a new herbicide propisochlor in water media as well as the effects of light sources, initial concentration of propisochlor, pH value, dissolved oxygen (DO) level, and salinity on the photolysis process was investigated. It was found that the relationship between initial concentration of propisochlor and its photodegradation rate was negatively correlated. The changes in acidity and alkalinity of the reaction medium influenced the photoreaction rate evidently. In the alkaline solution the degradation was accelerated. In the reaction media with different pH values, the photolysis followed the first-order kinetics. The presence of dissolved oxygen may promote the photolysis and there existed an optimum of dissolved oxygen concentrations. Increasing the DO level can weaken the promotion and even have an adverse effect. It was demonstrated that with dissolved oxygen the photodegradation of propisochlor followed the first-order kinetics equation. The addition of salt ions Ca2+ and Mg2+ changed the ionic strength and solvent polarity, resulting in the effect on propisochlor photolysis. The photoproducts were detected by both HPLC and GC-MS methods. It was found that photolysis products varied under different light sources. Conclusions may be reached that in the photodegradation of propisochlor, the benzene ring remained intact under irradiation of both solar light and high-pressure mercury lamp, and the amido link was relatively stable, while dechlorination was liable to take place; moreover, alpha-hydrogen at the substituent of benzene ring was active.

Propisochlor in water was irradiated at room temperature by a 400 W high pressure mercury lamp and sunlight, respectively. Influence of light and initiative concentration of propisochlor on the photolysis were studied. The results showed that under the irradiation of sunlight the photolysis fitted first order kinetics with only 5.5% degradation after one hour's irradiation in the quartz tube, that was a slow rate; while under the irradiation of high pressure mercury lamp the photolysis can be described by a double-chamber model, in which the degradation rate can reach 80.9% after 1 h. The higher the initiative concentration of propisochlor was, the slower the photolysis rate became, and the photolysis of propisochlor was influenced by the increasing photo-products. The six main photodegradation products were identified using GC-MS method. The aromatic ring was proved to be intact during the process. And the photolysis mechanism was then assumed on the basis of the photo-products detected.