贵州典型土壤中Cd形态分布及环境风险评价

Cd Speciation Distribution and Environmental Risk Assessment for Typical Cd Polluted Soil in Guizhou Province

重金属的生物毒性和生态效应与其结合形态密切相关。利用盆栽试验,模拟研究贵州省典型土壤遭受Cd污染后的形态分布特征及评估土壤中Cd的环境风险程度。结果表明：1自然条件下,黄壤和石灰土中残渣态Cd所占份额达80%以上,而非稳定态（包含酸溶态、可还原态和可氧化态）所占比例很低。2不同程度Cd污染土壤中,酸溶态和可还原态Cd所占比例明显高于自然土壤,特别是模拟污染为2.5 mg/kg和5 mg/kg土壤中,二者之和达65%以上。而且相比p H偏高的石灰土,黄壤中酸溶态Cd所占份额更高些。3由RAC法评价结果为自然土壤中Cd对环境危害处于低风险水平,但是污染土壤中Cd对环境构成中等以上的风险危害,而且随着污染程度加深,其风险性升高。总体上,黄壤中Cd对环境的危害高于石灰土。该研究结果为贵州省污染土壤风险管理提供科学依据。

The speciation distribution of heavy metals is closely linked to their biological toxicities and ec-ological effects.A pot experiment was conducted to study the characteristics of speciation distribution of Cd, which was added to typical soils in Guizhou Province with different concentrations,and the environmental risk of Cd was assessed.The results were as follows.①Under natural conditions,the proportions of residual Cd were more than 80%in yellow soil and calcareous soil,but the proportions of non-stable state Cd were very low,that is to say,the sum proportions of acid soluble Cd,reducible Cd and oxidizable Cd were less than 20%.②In the soils simulated with different degrees of Cd pollution,the proportions of acid soluble and reducible Cd were ap-parently higher than those in natural soils.Especially,when the external Cd concentrations were 2.5 mg/kg and 5 mg/kg,their ratios outnumbered 65%.Moreover,the acid soluble Cd share of yellow soil was greater than that of calcareous soil.③Based on the risk assessment code,the environmental risks of Cd were low in unpolluted soils.However,it was dangerous for environment that the risks of Cd exceeded moderate hazard in contaminated soils.As Cd contamination degrees mounted up,the risks became higher.Overall,the environmental risk of Cd in contaminated yellow soil was higher than that in polluted calcareous soil.The results of the study provides a scientific basis for the soil pollution risk management in Guizhou Province.