In the present work,
desorption of copper
ions adsorbed by variab le charge
soils was studied. Four
variable charge soils, i.e., Ali Haplic Ac ris ol, Ferrali Haplic Acrisol, Rhodic Ferralsol and Hyper Rhodic Ferrasol collect ed from south China, were used. As contrast, two constant charge soils, i.e., Hap lic Luvisoil and Phaeozems collected from Nanjing and Harbin respectively, were also used. The results showed that the copper ions adsorbed by variable charge soils could be
desorbed by deionized water. When the adsorbed copper ions were d esorbed at different pH, a pH～desorption rate curve could be obtained. A peak w ith maximum desorption rate could occur on the curve at a certain pH value. Wh e n the pH of soil suspension was higher than this pH value, the desorption rate d ecreased with the increase in pH. When the pH was lower than this pH value, th e desorption rate decreased with the decrease in pH. For different variable cha r ge soils, this pH value was related to the content of iron oxides in soils. Th e higher the content of iron oxides, the higher this pH value. After removal of copper ions which could be desorbed by deionized water, the residual copper ions adsorbed could be desorbed by dilute solution of NaNO 3. For different varia ble charge soils, the higher the content of iron oxides and the higher the concentr ation of electrolyte, the more difficult the desorption of the residual copper i ons adsorbed. On the contrary, the copper ions adsorbed by constant charge soi l s could not be desorbed by deionized water, but could be desorbed by electrolyte solution. The higher the concentration of electrolyte, the greater the abilit y of desorption of electrolyte. It is suggested that the mechanism of adsorptio n of copper ions by variable charge soils was different from that by constant cha rge soils.