Abstract:

With the development of industries, numerous wastes containing heavy metals from mining and smelting are discharged into soil, which has caused serious heavy metal pollution in soil and meanwhile poses a great threat to human health. Hence, this work takes the contaminated soil near a lead-zinc slag dumps as the research object. Tests on the stabilizing effect of heavy metal ions in contaminated soil by chitosan and its derivatives were carried out to screen the best stabilizing agent for the target heavy metals (Cd²⁺、Pb²⁺、Zn²⁺), and to probe the stabilizing mechanism. Furthermore, long-term stabilization effect of the screened stabilizing agent on heavy metal ions was studied under simulated acid rain leaching conditions. Both chitosan and its derivatives showed certain stabilizing effects on the heavy metal ions. Among them, carboxymethyl chitosan (CMCTS) had the best stabilizing effect by significantly reducing the migration and bioavailability of the heavy metal ions. The heavy metal morphology analysis, scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis showed that stabilizing agents reacted with the heavy metal ions in soil to form complexes. Moreover, through mechanism analysis, it was further verified that CMCTS had the best stabilizing effect on heavy metal ions. The simulated leaching test indicated that CMCTS had long-term stabilizing effect to the heavy metal ions in soil which were not easily leached out by simulated rain and tended to exist in soil with a more stable form. More important, CMCTS could also improve the soil environment and enhance the stabilization of heavy metal ions by soil itself. Hence, CMCTS is expected to be a promising stabilizing agent candidate for the remediation of the soil contaminated by heavy metals (Cd²⁺、Pb²⁺、Zn²⁺).

Key words: heavy metals in soil, chitosan derivatives, immobilization, leaching, pollution, remediation

摘要：

随着工业的发展，特别是采矿冶炼等行业的发展，使含重金属的废弃物进入土壤，造成土壤重金属污染，对环境和人体健康产生极大威胁。本文以湖南怀化某铅锌矿渣堆放地周围污染土壤为研究目标，通过壳聚糖及其衍生物对污染土壤中重金属离子的稳定化实验，筛选出对目标重金属（Cd²⁺、Pb²⁺、Zn²⁺）具有最佳稳定效果的稳定剂，探究了稳定剂对土壤中重金属离子的稳定机理，并在模拟酸雨淋溶条件下研究了最佳稳定剂对重金属离子的长期稳定化效果。稳定化实验结果表明，壳聚糖及其衍生物对土壤重金属离子均有稳定化作用，其中羧甲基壳聚糖的稳定效果最好，其使污染土壤中重金属离子的可迁移性及生物有效性明显降低。通过重金属形态分析、扫描电镜（SEM）及X射线衍射（XRD）分析得出稳定剂与土壤中重金属离子发生反应生成络合物，并通过机理分析进一步验证了羧甲基壳聚糖的稳定效果最好；淋溶实验表明，羧甲基壳聚糖对土壤中重金属离子具有长期稳定性，经其稳定后土壤中重金属离子以更稳定不易迁移的形态存在，且使土壤环境得到改善，增强了土壤本身对重金属离子的稳定。羧甲基壳聚糖有望成为修复重金属（Cd²⁺、Pb²⁺、Zn²⁺）污染土壤的优良稳定剂。

关键词: 土壤重金属, 壳聚糖及其衍生物, 固定化, 淋溶, 污染, 修复