Keywords: cadmium, adsorption, desorption, freeze–thaw cycles, brown soil, China, thawing conditions, freezing conditions, environmental pollution, soil contamination
Cadmium adsorption–desorption of brown soil with freeze–thaw cycles in northeast China
Adsorption–desorption characteristics of cadmium by brown soil, a typical soil in north–eastern China, were studied under different freeze–thaw cycles by using equilibrium adsorption isotherms. Freeze–thaw cycles were represented by temperatures of –30°C and 30°C, respectively. Both freezing and thawing conditions were implemented for three days each and the number of freeze–thaw cycles examined was zero, one, three and six. The results showed that the amount of adsorbed cadmium for one, three and six freeze–thaw cycles was 84, 74 and 70%, respectively, compared to soil experiencing no freeze–thaw cycles. About 33.1–50.0% of adsorbed Cd was desorbed from the soil without freeze–thaw cycles, while 32.1–73.0% of adsorbed Cd was desorbed from the freeze–thaw soil at the same initial concentration of Cd; the more the frequency of freeze–thaw, the higher the Cd desorbed.