铅锌厂重金属污染土壤的螯合剂淋洗修复及其应用

Washing of heavy metal contaminated soil around a lead-zinc smelter by several chelating agents and the leached soil utilization

为探讨螯合剂淋洗法在修复铅锌厂周边重金属污染土壤的修复效果及淋洗后土壤利用价值,研究采用振荡淋洗的方法比较了乙二胺四乙酸(EDTA)、次氮基三乙酸三钠盐(NTA)、[S,S]-乙二胺-N,N-二琥珀酸三钠盐(EDDS)乙二醇-双-(2-氨基乙醚)四乙酸(EGTA)4种螯合剂对不同污染程度土壤中Cd、Cu、Zn、Pb的去除效果,并用BCR连续提取法分析了淋洗前后土壤重金属形态的变化,最后通过黑麦草盆栽实验及土壤酶分析,探讨了土壤经淋洗后的利用价值。结果表明,4种螯合剂中EDTA对Cd、Cu、Zn和Pb的去除率比其他螯合剂的去除率高,其中对高污染土壤4种重金属离子的去除率最大,分别为Cd 90.98%、Cu 42.10%、Zn 56.98%和Pb 52.03%,4种重金属中Cd的去除效果分别为EDTA>NTA>EDDS>EGTA;EDTA能有效去除酸溶态、可还原态土壤重金属,而对可氧化态和残余态土壤重金属作用效果不明显;EDTA淋洗土种植黑麦草后土壤脱氢酶、碱性磷酸酶和β-葡糖苷酶活性均高于NTA淋洗后土壤中酶活性。综合考虑淋洗效率、淋洗剂的成本和利用价值等因素,可以认为,采用EDTA和NTA淋洗修复重金属污染土壤具有一定的实用性,并以EDTA效果较佳。

Batch leaching experiments were conducted to examine the effects of different chelates（ EDTA,EDDS,EGTA and NTA） on extraction Cd,Cu,Zn and Pb from different contaminated soils and the utilizable value of soil after leaching. The redistributions of heavy metals were determined using the BCR sequential extraction procedure before and after treatment. The utilizable value assessment of leached soil was also studied by the ryegrass pot experiment. The results showed that for the four kinds of heavy metal,Cd was the easiest to leaching and the leaching efficiency of different chelates on contaminated soil followed the sequence of EDTA NTA EDDS EGTA. Among the four chelates,i. e. EDTA,EDDS,EGTA and NTA,EDTA was the best effective in removing Cd,Cu,Zn and Pb,with removal rate being 90. 98%,42. 10%,56. 98% and 52. 03%. Enzyme activity assays showed that leaching with EDTA had a distinctly positive impact on soil microbial and enzyme activity,while leaching with NTA had less impact. Taking into account comprehensively extraction effectiveness,utilizable value and cost of the agents,EDTA was suitable for heavy metals extraction from contaminated soil.