Sorption and Desorption of Cyhalofop-Butyl on Mesopotamic Agricultural Soils

Abstract

The ability of herbicides to be adsorbed by the soil and their tendency to be desorbed are some of the most important factors affecting soil and water contamination. Therefore, a sorption and desorption study were conducted to evaluate the adsorption-desorption of cyhalofop-butyl, in the sandy clay loam and at different depths using a batch equilibrium method. The adsorption of cyhalofop-butyl was found positively related with the clay and organic carbon content. The kinetic profiles occurred in three steps. With an initial rapid adsorption in the early hours followed by slow adsorption and then it was constant during the rest of the range studied. Adsorption data conformed well to the Freundlich isotherm, whit increasing of adsorption with increasing of organic matter of the soil of different depth. The desorption process showed an important hysteresis phenomenon. The adsorption isotherm suggested a relatively higher affinity of cyhalofop-butyl to the adsorption sites at low equilibrium concentrations. The low value of the soil organic carbon partition coefficient (Koc) of cyhalofop-butyl in the sandy loam soil suggested its weaker adsorption in soil and thus increased its risk of mobility into water sources.