污染土壤中重金属的优势流迁移

Preferential transfer of the heavy metals in the polluted soils

用亮蓝溶液染色鉴定了2个污染土壤的优势流途径,并分离和采集被染色剂染色和不染色的土样,分析了重金属(Cu,Pb,Cd)含量和形态.结果表明,心土层以下染色部分土壤的重金属含量明显高于不染色部分土壤.两者之间的差异随土壤污染程度的增加而增加.染色部分土壤中酸溶态和有机质结合态重金属的比例明显高于不染色部分的土壤.染色部分土壤的细粘粒与粘粒总量的比值也高于非染色部分土壤,但供试土壤的水溶性重金属含量很低,推测颗粒态重金属的迁移是重金属迁移的主要方式,优势流可能在土壤重金属垂直迁移中有重要的作用.

Brilliant Blue was used as the dye tracer to identify the path of preferential flow in two polluted soils from a former iron mine in western Shaoxing County, Zhejiang province. Both dyed and non-dyed soils were separated for analyzing concentrations and configurations of Cu, Pb and Cd. An optimized three-step sequential extraction procedure referred from European Community Bureau of Reference was applied to heavy metal fractionation of the soils. Four operationally defined fractions were identified: acid extractable, reducible, oxidizable and residual. In addition, the soils were tested for water-soluble heavy metals. The results showed that concentrations of the metals in subsurface soils in dyed component were significant higher than those in non-dyed component. Differences of soil heavy metal concentrations between dyed and non-dyed component increased with increasing pollution degree of the metals. Acid soluble and organic matter-combined heavy metals in dyed component were significant higher than those in non-dyed component. The ratios of fine clay (<0.2?μm) to total clay (<2?μm) in dyed component were also higher than in non-dyed component. However, the concentrations of the water-soluble heavy metals in the soils were very low because of high pH in the soils. The results suggested that preferential flow played an important role in downward movement of the metals in the soil, and the metals were moved downward with fine clay and organic matter. These results indicated that preferential transfer of the heavy metals in the polluted soils might cause contamination of the groundwater when its water level was high.