辽宁省红透山铜矿区土壤中重金属迁移特征研究

Migration characteristic of heavy metals in soil around Hongtoushan copper mining area in Liaoning Province

采用柱淋溶实验模拟辽宁省红透山铜矿区土壤中重金属的淋溶迁移特征,研究了淋溶液pH、电导率(EC)和重金属含量的变化及其相关性,分析了重金属在淋溶前后的总量和形态变化,并初步探讨其生态与健康风险。结果表明,在1～3次淋溶中,淋溶液pH迅速下降,土样中的部分酸性物质被快速溶出,在第3次淋溶之后,淋溶液pH缓慢上升;淋溶初期淋溶液EC大幅度、迅速降低,此后随着淋溶次数的增加EC缓慢降低;Fe、Mn、Cu、As、Cd均能从土样中溶出进入淋溶液,其中Fe、Mn、Cu、As的溶出主要在淋溶初期,而Cd除了在初期有所溶出外,在淋溶后期还存在二次溶出释放阶段;淋溶后土样中绝大部分重金属总量均有所下降,各重金属的解吸率为Cd>As>Fe>Cu>Mn>Zn,其中以Cd、As含量下降最为明显,而Zn基本未溶出;淋溶前后土样中重金属的活性态(弱酸提取态(BCR-1)、可还原态(BCR-2)、可氧化态(BCR-3))含量发生了不同程度的变化,Fe的活性态含量在淋溶后变化很小,Mn、As的活性态含量在淋溶后有所上升,而Cu、Cd的活性态含量在淋溶后有所下降;随着淋溶的进行,土壤中各重金属的赋存形态发生了一定变化,从而可能引起其生态与健康风险的改变。

A column leaching experiment was conducted to investigate the dynamic migration of heavy metals in a mine-polluted soil collected from the Hongtoushan copper mine area. Variation of pH, EC and heavy metal in leacbate were detected and their correlation was studied by Pearson correlation analysis. The content of heavy metals forms before and after leaching process was studied so as to evaluate the ecological health risk of soil. The results showed that leachate pH dropped rapidly in the first 1-3 leaching cycle, illustrated that part of acidic material in soil was quickly dissolved out. However, the leachate pH increased gradually in the following leaching cycles. The leachate EC presented a sharp decrease in the early leaching stage, after then the decreasing tendency slowed down. Fe, Mn, Cu, As and Cd in soil were mainly leached out at the beginning of the experiment, but for Cd, a secondary release was also observed in the late of the leaching period. After leaching process, almost all heavy metals in soil de-creased greatly except Zn, the dissolution rate of different heavy metals followed the order of Cd〉As〉Fe〉Cu〉 Mn〉Zn. In addition, the fractionation analysis showed that the active forms （weak acid soluble form （BCR-2）, re ducible form （BCR-2） and oxidizable form （BCR-3）） of heavy metals changed in different degree, wherein the active forms of Fe was constant, active forms of Cu and Cd declined, and active forms of Mn and As increased. The existing form of heavy metals change a lot as the leaching processed, so the ecological health risk caused by soil must be re-evaluated.