Abstract:Adsorption-desorption of bensulfuron methyl, a kind of herbicide, in two types of soils treated with charcoal different in particle size, separately, was studied, using the batch equilibration technique, with focus on effect of charcoal amendment on adsorption-desorption of bensulfuron methyl in soils. Results show that the adsorption-desorption isotherms of bensulfuron methyl in charcoal and soils fitted the Freundlich equation (r>0.90). Charcoal showed a great adsorption capacity for bensulfuron methyl, and the smaller the particle size of charcoal, the higher the adsorption of bensulfuron methyl. The amendment of charcoal improved adsorption of bensulfuron methyl in the soils. The adsorption of bensulfuron methyl in the soils increased with the rate of charcoal amended. Desorption of bensulfuron methyl from charcoals and the soils displayed significant hysteresis, which was shown by the higher adsorption slope (1/nads) compared to the desorption slope (1/ndes). The hysteresis was closely related with the initial concentration of bensulfuron methyl and the content of charcoal in the soils, and the hysteresis index (H) increased with the rate of charcoal amended. This research suggests that charcoal can be used as artificially added adsorbent to efficiently control the pesticide in the soil from leaching.