土壤中Cd离子地球化学行为模拟实验--以山西的典型土壤为例

Simulation experiment of the geochemical behavior of Cd in soils—A case study of typical soils in Shanxi,China

土壤样品分别采于山西省大同、太原和临汾3个地区。实验分成吸附解吸、竞争吸附和运移实验3个部分。其中吸附实验又分成砂粒土壤和粘粒土壤2个粒级分别实验。结果表明:在常温常压下,3种土壤对Cd的吸附用Langmuir模式来拟合较合适,土壤粘粒的吸附能力大于土壤砂粒的吸附能力。Zn2+与Cd2+共存时,Cd的吸附受到抑制,在本实验浓度下,腐殖酸对土壤吸附Cd的抑制作用不明显。解吸过程显示土壤对Cd离子的解吸与有机碳、阳离子代换量成负相关。Cd在土壤中的穿透曲线是Cd在土壤中吸附、解吸、络合、迁移等作用的综合体现,Cd在各种土壤中的运移时间顺序为:大同土壤>临汾土壤>太原土壤,从而得出Cd在壤质砂土中运移得最快、在粉土中运移得最慢的结论。

Soft samples were taken from Datong, Taiyuan and Linfen. The experiment comprised three parts： adsorption-desorption, competitive adsorption and transport experiment. Softs for the adsorption experiment were sieved into the sand-sized fraction and sfttand clay-sized fraction. The main results indicate that： it is suitable to use the Langmuir model to fit the adsorption of Cd by the three types of soft at normal temperature and pressure. The adsorption capacity of the day-sized fraction is higher than that of the sandsized fraction. In the case of coexistence of Zn^2＋ and Cd^2＋, Cd adsorption is inhibited. At the concentration in this experiment, humic acid shows no pronounced effect on the inhibition of Cd adsorption. The desorption experiment shows that there was a negative correlation between Cd desorption capacity of softs and TOC and CEC. The penetration curve of Cd in softs was the integrated manifestation of adsorption, desorption, complexing and transport of Cd in softs. Cd was transported more rapidly in the Datong soft than in the other two kinds of soft. Consequendy the authors conclude that Cd is transported most rapidly in loamy sand and most slowly in sandy loam.