简化连续提取法评价污染土壤中Zn、Cd的植物有效性

以0.01 mol·L^-1CaCl₂和0.005 mol·L^-1 DTPA作为提取剂,用简化的3步连续提取法对贵州省赫章县土法炼锌污染土壤中Zn、Cd的形态进行了分析.结果显示,污染土壤中Zn、Cd主要以残渣态的形式存在,CaCl₂提取态和DTPA提取态Zn、Cd平均仅占全量的0.63%、3.91%和10.94%、10.13%.土壤中不同形态Zn、Cd含量与玉米中Zn、Cd含量的相关分析结果显示,CaCl₂提取态金属与玉米中金属含量没有显著的相关关系,而DTPA提取态、残渣态以及总量Zn、Cd与玉米根、茎叶中Zn、Cd含量显著正相关.这些结果表明CaCl₂提取态Zn、Cd对土壤中该元素的植物有效态可能不具重要贡献,而DTPA提取态金属和金属总量在一定程度上能作为评价土壤中元素植物有效性的标准.

Evaluation of Phytoavailability of Zinc and Cadmium in Contaminated Soils by a Short Sequential Extraction Procedure

Cultivated soils and maize samples from heavy metal contaminated locations affected by zinc smelting activities were collected in Hezhang County,Guizhou Province.Chemical fractions of zinc and cadmium(extracted by 0.01 mol·L^-1 CaCl_2 and 0.005(mol·L^-1) DTPA) were evaluated by using a short three-step sequential extraction procedure.Results showed that Zn and Cd in soil were dominated by residual fraction,while the CaCl₂ extractable and DTPA extractable fraction are only accounted for 0.63%,3.91% for Zn,and 10.94%,10.13% for Cd,respectively.Correlation analyses demonstrated that soil CaCl₂ extractable metals were not correlated with maize metal concentrations,whereas the DTPA extractable fraction,residual fraction and total Zn and Cd concentrations were correlated significantly with the metal concentrations in maize roots,stems and leaves.These results indicated that CaCl₂ extractable fraction may not pay important role on metal phytoavailability in the studied soils.While DTPA extractable fraction and total metal concentrations can be employed to evaluate metals phytoavailability.