碳酸钙对土壤镉吸附及解吸的影响

采用等温吸附法，并以1mol/L KNO3进行解吸试验，研究CaCO3对3种土壤镉吸附和解吸的影响。结果表明，3种土壤的原状土样对镉吸附总趋势为：栗钙土＞棕壤＞淋溶褐土，均符合Langmuir方程、Frenudlich方程和Temink方程，其中以Freumdlich方程最佳。镉的专性吸附量表现为栗钙土＞淋溶褐土＞棕壤。添加CaCO3使3种土壤中镉的吸附量增加，增加幅度棕壤为4％－11％，淋溶褐土2％－11％，栗钙土2％－8％。外界加入的镉浓度越高，增加幅度越大。Freundlich方程（lgX=lgK lgC/n）拟合的参数结果表明：加入CaCO3后，K和n值均下降；Langmuir方程中镉最大吸附值增加，吸附平均常数减小。可以推测，CaCO3的存在之所以能够使土壤体系吸附镉能力增加，除CaCO3本身的吸附作用增加，吸附平衡常数减小。可以推测，CaCO3的存在之所以能够使土壤体系吸附镉能力增加，除CaCO3本身的吸附作用外，还可能影响反应体系的平衡系数。加入CaCO3,土壤对镉的专性吸附明显增加，尤其以棕壤专性吸附的镉最多，淋溶褐土其次，而栗钙土增加较少，栗钙土去除CaCO3后，镉的吸附减少了2.0%-26.0%，土壤专性吸附的镉减少4.0%-38.2%。3种土壤镉的解吸能力表现为：棕壤＞淋溶褐土＞栗钙土。添加CaCO3，土壤镉的解吸量下降。去除CaCO3后，栗钙土匐解吸量明显增加。

Effect of calcium carbonate on adsorption and desorption of cadmium in soils

A batch experiment was conducted to study the effect of calcium carbonate on the adsorption and desorption of Cd in three kinds of soils.The solution of different Cd concentrations prepared with CdCl 2 was equilibrated with soil samples by shaking for 12 hours and 1mol/L KNO 3 was used to extract the exchangeable Cd.The effect of calcium carbonate was investigated by removal of calcium carbonate (by 0.5mol/L pH5.0 NaAc HAc) in castanozem soil and by adding of calcium carbonate (1.0%) to leached cinnamon soil,brown earth and castanozem soil,respectively.The results showed that (1) the total amounts of Cd adsorption and specific Cd adsorption were increased in the following order:leached cinnamon soil