Abstract:

With the rapid development of industry, especially the rapid expansion of mining and smelting industries, serious soil heavy metal pollution has been caused. In order to realize the simultaneous remediation of soil contaminated by heavy metals, the farmland soil around a lead-zinc mine in southern Sichuan was taken as the research target. Through soil cultivation experiments, the effects of different ratios of chitosan (CS) and four modified chitosan materials on the basic physicochemical properties of polluted soil, the DTPA effective state and distribution form of heavy metals (Cu, Pb, Zn, Cd) in soil, and the migration characteristics of heavy metals were investigated to select the best material for the target heavy metal passivation. The study found that using different ratios of CS and modified chitosan materials resulted in an increase in soil pH, organic matter (OM) and cation exchange capacity (CEC) in farmland soil contaminated with Cu, Pb, Zn and Cd. The increase in these parameters showed an upward trend with increasing addition. The application of a certain proportion of CS increased the content of available Cu and Pb, while the four modified chitosan materials reduced the content of available Cu, Pb, Zn and Cd, reducing the bioavailability and mobility of heavy metal pollution. Meanwhile, the addition of all five materials could effectively promote the transformation of Cu, Pb, Zn and Cd from the weak acid extraction state to the stable residue state in the soil, and the best passivation effect was achieved when ECS-B was added to the soil with a mass ratio of 2.5%. This study indicated that ECS-B material was effective in passivating Cu, Pb, Zn and Cd contaminated soil, and had potential application for remediation in the field of heavy metal contaminated soil.

Key words: chitosan modification, composites, soil, heavy metal, pollution, remediation

摘要：

随着工业的迅猛发展，尤其是采矿冶炼等行业的快速扩张，造成了严重的土壤重金属污染问题。为实现重金属复合污染土壤同步修复，以川南某铅锌矿区周边农田土壤为研究目标，通过土培实验，考察施加不同比例壳聚糖（CS）和4种改性壳聚糖材料对污染土壤的基本理化特性、土壤中重金属（Cu、Pb、Zn、Cd）二乙烯三胺五乙酸（DTPA）有效态及赋存形态的影响，阐释重金属迁移特性，筛选出对目标重金属钝化效果最好的材料。结果显示，在Cu、Pb、Zn、Cd复合污染农田土壤中，施用不同比例CS及改性壳聚糖材料后，土壤pH、有机质含量（OM）和阳离子交换量（CEC）均得到提升，整体呈随添加量增加而上升的趋势；在一定比例CS处理下，Cu和Pb有效态含量均有所增加，而4种改性壳聚糖钝化剂均能降低Cu、Pb、Zn、Cd有效态含量，从而有效降低了复合重金属污染的生物有效性和可迁移性；同时，5种材料的加入均能有效促进土壤中弱酸提取态Cu、Pb、Zn、Cd转化为稳定的残渣态，向土壤中添加质量比为2.5%的环氧氯丙烷改性壳聚糖-生物炭复合材料（ECS-B）时钝化效果最佳。本研究表明，环氧氯丙烷改性壳聚糖-生物炭新型复合材料钝化Cu、Pb、Zn、Cd复合污染土壤效果显著，在重金属复合污染土壤修复领域具有一定的应用潜力。

关键词: 壳聚糖改性, 复合材料, 土壤, 重金属, 污染, 修复