Study on the Behavior and Fate of Pesticides in Aquatic Environment

Abstract

The behavior and fate by runoff of pesticides applied to paddy field were investigated. The necessary sample numbers for measurement of pesticide concentration in river water were allow to less when pesticides were applied at all over of river basin. But, many samples were necessary for the pesticides applied by aerial application to the limited area. In the rainy times, the runoff amount of pesticides per unit time was influenced by the variation of flow water volume rather then the variation of pesticide concentration. On the research of the change of pesticides concentration in main river of Chiba prefecture, pesticides in river water are not presumed to be influenced on human health. For six years from 1983 to 1988, runoff and leaching of 21 pesticides were measured with lysimeters. The runoff percentages and the water solubility were significantly related statistically (r=0.872, n=18). Furthermore, the runoff percentages of pesticides from lysimeters and those from actual paddy fields to river water also related significantly (r=0.870, n=8). With the analysis of the multiple regression equation, it was found that the factors as water solubilities of pesticides, application method, application time, formulation, rainfall were related with pesticide runoff from the paddy field and behavior and fate of pesticides in the aquatic environment was predictable.