Abstract: The photodegradation dynamics of herbicide butachlor in different water was studied under xenon lamp and high pressure mercury lamp illuminating. The result shows that under xenon lamp illuminating, the photodegradation rate of butachlor was in order of pure water＞river water＞pond water＞paddy water. Butachlor photodegraded slower under xenon lamp than under high pressure mercury lamp, and the speed was negatively correlated to the dosage. Moreover, the photodegradation rate was slowed down by filling nitrogen and de-oxygen.

Key words: Butachlor, Photodegradation, Illumination, Xiangshan Bay, thermal discharge, size spectra, power plant, zooplankton