Adsorption and redox reactions between As (Ⅲ) and two variable charge soils collected from Guangdong province and Jiangxi province were studied with the batch method.As (Ⅲ) adsorption by the soils increased with the amount of As (Ⅲ) added.The latosol adsorbed more As (Ⅲ) than the red soil did,because the content of iron and aluminum oxides in the former was higher than that in the latter.As (Ⅲ) adsorption by both soils increased with pH.As (Ⅲ) could be oxidized to As (V) by manganese oxides in the latosol,while no appreciable redox reactions with As (Ⅲ) were observed in the red soil.As (Ⅲ) oxidization decreased with increasing pH.The results from desorption of As (Ⅲ) by 1.0 mol L^-1 KNO₃ indicated that the desorption rate of adsorbed As (Ⅲ) was less than 35%,suggesting that most As (Ⅲ) was adsorbed through the formation of inner sphere surface complexes on the soils.The desorpation rate of As (Ⅲ) increased with the pH of the adsorption system in the experiment,indicating that the proportion of outer sphere surface complexes to the total surface complexes increased at higher pH.