摘要
本文以广东省韶关市大宝山矿区周边重金属污染土壤为研究对象,采用EDTA、柠檬酸和草酸作为淋洗剂对土壤中的Pb、Zn、Cu、Cr进行去除,并对淋洗前后土壤中重金属形态变化进行研究,以分析土壤中重金属的存在形态对淋洗效果的影响以及淋洗法对土壤中重金属形态的影响.结果表明,三种淋洗剂对Pb、Zn、Cu、Cr的整体去除效果依次为草酸＞EDTA＞柠檬酸,Cu＞Cr＞Zn＞Pb.利用Tessier五步提取法对草酸淋洗前后的土壤进行重金属形态分析,发现淋洗效果与重金属的存在形态具有一定关系,淋洗能够有效的去除以可交换态和碳酸盐结合态形式存在的重金属离子.与淋洗前相比,淋洗后土壤中重金属的可交换态和碳酸盐结合态比例均减少,铁锰氧化物结合态和有机结合态比例整体增加,残渣态比例增加明显,能够有效降低土壤中重金属的环境风险.
Abstract
In this paper,the heavy metal polluted soil around the Dabaoshan mining area in Shaoguan City,Guang-dong Province was taken as the research object,and the EDTA,citric acid,and oxalic acid was used as leaching agents to remove the Pb,Zn,Cu,and Cr in the soil.In addition,the changes of heavy metals forms in the soil before and after leaching were studied to analyze the influence of the existing forms of heavy metals on the leaching effect and the effect of the leach-ing on the heavy metals forms.The results showed that the overall removal effects of the three leaching agents on Pb,Zn,Cu and Cr were in order of oxalic acid>EDTA>citric acid,Cu>Cr>Zn>Pb.Using the Tessier five-step extraction method to an-alyze the heavy metals forms of the soil before and after oxalic acid leaching,it was found that the leaching effect has a cer-tain relationship with the existence of heavy metals,and leaching can effectively remove heavy metal ions in the form of ex-changeable and carbonate-bound states.Compared with the heavy metal forms in the soil before leaching,the proportions of the exchangeable state and carbonate-bound state after leaching decreased,the proportions of the iron-manganese ox-ide-bound state and organic-bound state increased overall,and the proportions of the residue state increased obviously,it can effectively reduce the environmental risk of heavy metals in the soil.
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