Immobilization and soil washing technologies have been often-suggested technologies for the remediation of soils contaminated by heavy metals.Two contaminated soll samples taken from two sites were treated with 0.4%,1.2%.2.0%of humic acids(HA).The chemical form fractions of Pb,Cd,Cu,and Zn in these soll samples were investigated.The results indicate that HA is effective at immobilizing Pb and Cd in the form of residual fractions or organic matter fractions in the soll samples,which were not available for a soil-plant-human system ; and that the application of immobilization technology is restricted by a limited immobilization capability of HA,so it is not fit for the zone contaminated by high contents of heavy metals.Laboratory batch extraction studies were also conducted to determine the ability of extractants such as 0.05 mol EDTA,0.05 mol oxalate(OX),0.05 mol citric acid(CA)and the mixture of 0.05 mol citric acid and 0.05 mol rhamnolipid(CAR)to remove Pb,Cd,Cu and Zn from the contaminated soils.The results show that EDTA is effective at removing Pb and Cd while OX is effective at removing Cu and Zn ; and that HA in the soils promotes the washing of Cu and Zn but prevents that of Pb and Cd.The exciting result is that rhamnolipid as a bio-surfactant surfactin added to citric acid solution can enhance the removal of heavy metals.The application of soil washing technology is restricted by its high cost and secondary contamination.%固定化和化学冲洗是土壤中金属污染治理常用技术.研究分别用0.4%,1.2%和2.0%的胡敏酸固定化2种重金属污染土壤样品,并通过分析Pb,Cd,Cu和Zn的存在形态来检验其固定效果,结果表明,胡敏酸可以将大部分的Pb和Cd转化为残留态以及有机结合态,大大降低其生物有效性,从而降低了其环境风险.但是,由于该技术受制于胡敏酸在土壤中的流动性,他必须和其他技术如化学萃取技术联合才可以实际应用.分别以0.5 mol/L的EDTA,草酸(OX),柠檬酸(CA)以及柠檬酸和鼠李糖脂(CAR)为萃取剂,进行了进一步的萃取试验.结果表明:EDTA对Pb和Cd的去除效果最好;OX对Cu和Zn的去除效果最好;胡敏酸有利于Cu和Zn的去除,但是抑制Pb和Cd的去除;鼠李糖脂促进Pb,Cd,Cu和Zn的去除.但是,修复成本较高,该技术离实际应用还有一定的距离.
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