Study On The Photodegradation Of Phoxim In Lake Under Solar Radiation

Nowadays, there are a large number of artificial and natural lakes have been serious polluted by pesticides, herbicides and other wastewater. Therefore, treating and restoring lakes is one of the most important works to improve the environment of which. In general, lakes are wide and huge water bodies, so that they can not be treated by traditional wastewater treating methods which widely used to treat convergent wastewater. As a result, seeking after an economical and effective method to treat and restore the contaminated lakes has become a focus in this field.As limitless energy, solar radiation can not only provide energy to the photosynthesis of hydrophytes but also degrade the organic pollutants in lakes. In this paper, perfect solar photodegradation experiments project has been devised to validate its feasibility. In this project the influence factors such as waters depth, motion of water, climate and weather as well as the suspended substances, algae, DOM and other organic or inorganic ions have been taken into account in order to describe the influencing process of these factors on the photodegradation.In this paper, the photodegradation of phoxim, a kind of organophosphorus pesticide, has been studied under solar radiation as well as under artificial UV radiation. Phoxim in lake water, sterilized lake water and distilled water at concentration of 7mg/L were irradiated by solar radiation or UV radiation under the conditions of different water depths and water motions. With comparison, phoxim in lake water at concentration of 7mg/L also has been studied under dark condition.The changes of phoxim were detected by Gas chromatograph. As a result, after 14 days 3.14 to 3.71 percent of phoxim which under dark condition has been degraded, 30.14 to 77.71 percent of phoxim which under solar or UV radiation has been degraded as well. It was found that the photodegradation follows first-order kinetics behavior in all cases. Under solar and UV irradiation, the half-lives of phoxim varied between 9.1 and 26.4 days and between 5.9 and 6.6 days respectively.The photodegradation of phoxim influenced greatly by multifarious factors such as waters depth, motion of water, climate and weather as well as the suspended substances, algae, DOM and other organic or inorganic ions. Mathematical models have been developed to describe the influencing process of these factors.