The Adsorption and Desorption of Pb2+ and Cd2+ in Freeze-Thaw Treated Soils

摘要

Adsorption and desorption are important processes that influence the potential toxicity and bioavail-ability of heavy metals in soils. However, information regarding adsorption and desorption behavior of heavy metals in soils subjected to freeze-thaw cycles is poorly understood. In the current study, the effect of freeze-thaw cycles with different freezing temperature (-15, -25, -35 degrees C) on soil properties was investigated. Then the adsorption and desorption behavior of Pb2+ and Cd2+ in freeze-thaw treated soils was studied. The adsorption amounts of Pb2+ and Cd2+ in freeze-thaw treated soils were smaller than those in unfrozen soils (p 0.05), due to the fact that pH, cation exchange capacity, organic matter content, free iron oxide content, and CaCO3 content in freeze-thaw treated soils were smaller than those in unfrozen soils. The adsorption amounts of Pb2+ and Cd2+ in soils treated with lower freezing temperatures were higher than those in soils treated with higher freezing temperatures. Desorption percentages of Pb2+ and Cd2+ in unfrozen soils were smaller than those in freeze-thaw treated soils (p 0.05). The desorption percentages of Pb2+ and Cd2+ were smaller in soils treated with lower freezing temperatures than those in soils treated with higher freezing temperatures. The results obtained highlight the change of the adsorption and desorption behavior of typical heavy metals in freeze-thaw treated soils located in seasonal frozen soils zone in northeast China.