Abstract: 【OBJECTIVE】The adsorption-desorption behavior and mechanism of chlorimuron-ethyl in soils were investigated to provide the basic data on evaluating the safety in field and the risk to water resource. 【METHOD】The adsorption-desorption experiment was conducted by the batch equilibration and HPLC techniques, furthermore, data were analyzed with 5 mathematic models to describe the characteristics and mechanism of adsorption-desorption and translocation of the herbicide in soils.【RESULTS】The results showed that the adsorption-desorption isotherms of chlorimuron-ethyl fitted for Freundlich model well, and the physical reaction perform main contribution during adsorption-desorption process. The adsorption values (Kf-ads) of chlorimuron-ethyl in 8 type soils ranged from 0.798 to 6.891. The isotherms of 2# and 3# soils belong to S-type curve, while the isotherms of another 6 type soils belong to L-type isotherm. The results of desorption indicated that the hystersis phenomena appeared during the desorption process, and the hystersis coefficients（H）of the herbicides in 8 soils varied from 0.259~0.980. Furthermore, Kf-ads and desorption values (Kf-des ) increased with OM% and clay content increasing, while decreased with soils pH increasing. H values decreased with OM% and clay content increasing and increased with soils pH increasing.【CONCLUSION】It could be concluded that the low adsorption abilities of chlorimuron-ethyl in test soils and un-reversible adsorption existed in the process, which would induce the great translocation of the herbicide after applied in field. It could be transported to ground or ground water taking risk to environments. Physical and chemical properties of soils, including OM%, clay content and pH of soil, performed the dominating factors during the adsorption-desorption.

Key words: chlorimuron-ethyl, adsorption-desorption, Freundlich model, Hystersis, Physical and chemical properties of soils