套种和化学淋洗联合技术修复重金属污染土壤

联合不同的重金属污染土壤修复技术可以弥补单一措施的不足,其中植物提取联合化学淋洗技术就是有效的途径之一.本研究通过盆栽试验,在东南景天和玉米套种情况下,用不同浓度和种类的混合试剂对土壤进行化学淋洗,测定淋洗液中重金属含量、植物的吸收量以及土壤重金属的剩余量.结果表明,第1季10 mmol.L-1的混合试剂对套种系统淋洗,Zn、Cd的总去除量(植物提取量和淋洗量)最高,两季合计对Zn、Cd的总去除率分别达到6.0%、40.46%,大于单一植物提取.土壤测定结果表明,通过两季(约9个月)套种植物联合淋洗技术处理后,土壤重金属Cd、Zn和Pb的降低率分别达到27.8%～44.6%、12.6%～16.5%和3.6%～5.7%.50 mmol.L-1的混合试剂对套种系统淋洗,会影响后季东南景天的生长,而且淋洗结束后用清水淋洗产生的淋出液浓度高于其他低浓度处理,风险较大.EDDS(乙二胺二琥珀酸)混合试剂亦能促进东南景天吸收Zn和Cd,但不能有效淋洗出土壤中的Pb.在该套种+淋洗联合技术中,Zn、Cd的去除主要靠植物提取,Pb的去除主要靠淋洗,套种+淋洗加快土壤修复,而且可能解决Zn/Cd/Pb复合污染问题.

Metal Removal from Contaminated Soil by Co-planting Phytoextraction and Soil Washing

Combining the different soil remediation technologies can overcome the shortcoming of a single technique, for example, the combination of phyto-extraction with chemical washing can enhance the phytoextraction and build up an effective technology. In a pot experiment, the co-crop of Sedum alfredii and Zea mays was conducted, chemical washing was also applied with different mixtures of chelators (MC). Metals amounts washed by leaching, the uptake of metals by plants and the metals contents remained in soils were determined. Results showed that the co-crop combining with 10 mmol x L(-1) MC washing removed the highest amount of Zn and Cd,and after 2 crops, the removal rates reached 6.0% and 40.46% of the soil total metal respectively for Zn and Cd, which were higher than those for the only co-planting. Soil analysis showed that the two successive co-crops with MC washings decreased soil Cd,Zn and Pb by 27.8% - 44.6%,12.6% -16.5% and 3.6% - 5.7%, respectively. Chemical washing with 50 mmol x L(-1) MC affected the growth of S. alfredii and resulted in higher metal contents in thereafter leachate water than the other less concentrated washing agents. EDDS (S, S]-ethylenediaminedisuccinic acid) enhanced the phytoextraction of Cd and Zn but did not effectively wash Pb. Zn and Cd removal mainly depended on phytoextraction while Pb removal relied on MC-washing in this combined technology, by which the multi-metals contamination problem could be resolved.