镉与柠檬酸、EDTA在几种典型土壤中交互作用的研究

采用批平衡实验方法研究了镉在青黑土 (IB)、黄棕壤 (YB)和红壤 (R)三种土壤上的吸附和解吸过程以及吸附介质酸度、共存有机酸等对此过程的影响。结果表明 :柠檬酸、EDTA的存在明显降低了镉在黄棕壤和青黑土上的吸附 ,同时镉解吸率较在硝酸钠体系要小 ,有机物的存在增加了土壤中镉的相对非饱和吸附点位。而在红壤上有机物的存在对镉的影响则随介质pH的改变而发生显著变化。酸性条件下 ,有机物的存在增加镉在红壤上的吸附 ,而随pH的增加 ,有机物减少镉的吸附。同时镉在硝酸钠体系中的解吸率随总吸附量的增加而呈现峰形的变化规律。土壤类型变化显著影响镉与有机物之间的交互作用过程

INTERACTION OF CADMIUM AND CITRIC ACID, EDTA IN SEVERAL KINDS OF SOIL

The process of cadmium adsorption and desorption on lndicotic Black (IB, Cambisols), Yellow Brown (YB, Luvisols) and Red (R, Ferrisols) soils as well as the influence of media's pH were investigated in detail. The presence of organic chemicals obviously influenced the processes of cadmium adsorption and desorption. Adsorption of Cd in YB and IB soils decreased in the presence of citric acid and EDTA, meanwhile, its desorption rate was lower than that obtained in the absence of organic chemicals, which suggests that the relatively unsaturated adsorption sites for Cd increased in the present of organic chemicals. For Red soil, Cd adsorption in the presence of citric acid and EDTA increased with pH in low pH media but decreased in high pH one, which was very different from YB and IB soils. Further studies indicated that adsorbed Cd in red soil existed significantly as unexchangeable one, and desorption rate by 0.1 mol?La?a(c)-1 NaNO 3 gave a peak shape curve.