Adsorption and desorption of imazosulfuron by soil

Understanding and quantifying the adsorption and desorption of herbicides b y soil is important for predicting their fate and transport in the environm ent. Here we report a study concerning the adsorption and desorption, by fo ur different soils, of imazosulfuron, 1-(2-chloroimidazo[1,2-a]pyridin-3-yl sulfonyl)-3-(4,6-dimethoxypyrimidin-2-yl) urea, a new sulfonylurea herbicid e. Both phenomena are well-described by the Freundlich equation, which show s this herbicide to be little adsorbed by each of the four soils investigat ed. The Freundlich adsorption constants, Kf-ads, ranged from 1.46 to 3.02. Distribution coefficients between soil and water, K-d, measured on soils of different organic matter contents and pH values showed an important effect of these two parameters on imazosulfuron retention. The Freundlich desorpt ion data indicated that a significant amount of the imazosulfuron sorbed is not easily desorbed. The desorption process showed an evident hysteresis p henomenon, which may contribute to the persistence of imazosulfuron in soil .