| Leaching in soil is one of important environmental behaviors of pesticides, which is most important source of pollutants in underground water. Assessing the leaching of new pesticides has become an integrated part of studies concerning the environmental safety of pesticides.Ethametsulfuron-methyl is the sulfonylurea herbicide, which is relatively new class of compounds and effective for the control of both simple-leaf and double-leaf weeds and certain grasses in rape field. Although the investigation of leaching of ethametsulfuron-methyl in soils is required by registration authorities, knowledge of the relevant processes is limited.In this paper, adsorption, leaching and the effect of the simulated rainfall, SAA (surface active agent), humus (humic acid and its sodioum salt, peat) on the leaching of the herbicide ethametsulfuron-methyl in three kinds of soils (red soil, yellow cinnamon soil, and black soil) were studied with soil column. Hydrolysis of ethametsulfuron-methyl and its products were also provided in detail. The main results were summarized as follows:Adsorption of ethametsulfuron-methyl in soils was studied using batch equilibration technique , and the results showed that (1) the amount of ethametsulfuron-methyl adsorbed by soils varied with different soils, and followed the order: red soil > yellow Cinnamon soil > black soil; (2) adsorption of ethametsulfuron-methyl in soils fitted well the Freundlich equation, and the adsorption constant Kf, which stands for the absorbability, decreased with increasing of pH and increased with increasing of contents of OM (organic matter) and clay of soils; (3) the amount of adsorption of ethametsulfuron-methyl was negatively correlated with pH values of soils, especially in red soil; (4) free energy of sorption for ethametsulfuron-methyl on soils indicated that the adsorption belonged to physical reaction; (5) adsorption constant Koc for ethametsufruron-methyl in soils indicated that ethametsulfruon-methyl was of medium leachability in both red soil and yellow Cinnamon soil, and higher leachability in black soil.Rainfall had a great effect on the leaching of ethametsulfuron-methyl in soils:(1) The amount of ethametsufuron-methyl reclaimed in leachate increased with the rainfall increasing and followed the order: 1500mm > 1000mm > 500mm. (2)Underthe same rainfall, leaching of ethametsulfuron-methyl in different soils varied greatly, and the amount of ethametsulfuron leached in leachate followed the order: black soil >yellow cinnamon soil > red soil. (3) The relative equation of amount of ethametsulfuron-methyl in leachate with rainfall, physical and chemical parameters of soils indicated that the leaching of ethametsulfuron-methyl was consanguineously correlated with rainfall, soil characteristics such as organic matter content, clay content, and pH, i.e. the amount of ethametsufuron-methyl in leachate increased with rainfall and pH values increasing and decreased with increasing of contents of clay and OM. The distribution of ethametsulfuron-methyl varied greatly in different soils: the distribution depth of ethametsulfuron-methyl in black and yellow cinnamon soils increased instantly with rainfall increasing, while increased slowly with rainfall increasing in red soil.Three kinds of SAA were selected to observe the impact of SAA on the leaching of ethametsulfuron-methyl in soils, the results showed that the impact of SAA on the leaching of ethametsulfuron-methyl was well correlated with the kind of SAA and the concentration used. (1) cationic surfactant CTAB (cetyltrimethyl ammonium bromide) delayed the leaching of ethametsulfuron-methyl downward, whereas both nonionic surfactant T-60 (Tween-60) and anionic SLBS (sodium lauryl benzene sulfonate) accelerated the leaching of ethametsulfuron-methyl in soils. Moreover, the impact of SLBS was more remarkable than T-60, especially in red soil. (2) The amount of ethametsulfuron-methyl reclaimed in leachate increased remarkably with the concentration of SLBS increasing in elution in red soil. (3) A...
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