土壤-辣椒系统中重金属镉形态变化和有效性研究

The Cd form change and effectiveness in a soil-hot pepper system

采用盆栽试验,在外源重金属镉(Cd)梯度分别为0 mg·kg^(-1)0.5 mg·kg^(-1)、mg·kg^(-1)2 mg·kg^(-1)、4 mg.kg^(-1)、8 mg·kg^(-1)、16 mg·kg^(-1)的供试土壤中种植辣椒,研究其土壤中重金属Cd形态及有效态含量变化,以及辣椒植株内重金属吸收、转运的情况。结果表明:离子态重金属加入土壤后,镉的残渣态所占的比例最高,水溶态和弱酸提取态在种植辣椒后逐步降低,可还原态和可氧化态镉含量略有增加。土壤Cd的全量及有效态含量对辣椒生长从总趋势上均呈负相关的表现,有效态含量越高,植株生长情况越差,特别在低浓度阶段表现较为明显。当土壤中Cd的有效态为低浓度时,外源Cd浓度增加对作物中富集Cd的作用更强,后期趋向平缓。根系的Cd含量与土壤Cd的全量和有效态含量成正相关线性关系,相比茎叶和果实,根系Cd的含量与土壤中Cd有效态含量关系更密切。通过植株中Cd的富集系数研究,可知植株中重金属的迁移是通过根部吸收后由茎叶转运,分布浓度依次为根系>茎叶>果实。

The pot experiments with hot pepper were carried out under soil added with Cd at0 mg·kg^-10.5 mg·kg^-1、mg·kg^-12 mg·kg^-1、4 mg.kg^-1、8 mg·kg^-1、16 mg·kg^-1 respectively so as to study the Cd form change in the soil and the conditions for the plants to absorb and transport Cd. The results showed that after adding ionic state Cd to soil the residual form Cd accounted for the largest proportion, and after planting hot pepper the water-soluble and weak acid-extracted Cd contents gradually decreased while the reducible and oxidizable Cd contents somewhat raised. In general the total and available Cd contents correlated negatively to the plant growth, the higher the available Cd content, the poorer the plant grew especially at a low Cd concentration. At a low available Cd concentration of soil, increasing the added Cd concentration had a strong effect on the Cd accumulation of the plant and the effect tended to a smooth level at the later stage. The Cd content of the plant roots correlated positively to the total and available Cd contents of soil and had a closer correlation with the available Cd content of soil than those of the stems and leaves had. From the accumulation coefficients of different plant parts it was found that the descending order of Cd contents was the roots 〉 the stems and leaves 〉 the fruit.