EDTA溶液修复重金属污染土壤的效果及金属的形态变化特征

采用0.05mol·L^-1的EDTA作为萃取剂,在一定的萃取条件下,对2种尾矿土壤中重金属进行土壤柱萃取实验,并采用优化的BCR(European Community Bureau of Reference)连续萃取方案对萃取前后的Pb、Zn、Cu和Cd进行形态分析.研究EDTA对4种金属的萃取效率及萃取前后的形态变化特征.结果表明,EDTA能有效的从土壤中萃取该4种金属,萃取效率依次为:Cd>Zn>Cu>Pb;金属的4种形态均能被EDTA萃取;在浅层土壤中,EDTA对酸可提态的金属的萃取效果尤为显著;在深层土壤中,酸可提取态、氧化物结合态、有机结合态和残余态4种形态的金属萃取效果,随着土壤柱深度的增加而降低.

Extraction of Heavy Metals from Contaminated Soils with EDTA and Their Redistribution of Fractions

EDTA was used as extractant to leach Pb,Zn,Cu and Cd from tailing soils in soil columns.The redistributions of Pb,Zn,Cu and Cd were determined using the sequential extraction procedure of the optimized European Community Bureau of Reference(BCR) before and after extraction.The results indicated that EDTA was an effective extracting agent because of its strong chelating ability for different heavy metals.Percentage extractabilities of metal followed the sequence of Cd > Zn > Cu > Pb.The four fractions of metal could be extracted by EDTA and the proportions of Pb,Zn,Cu and Cd in the four fractions varied largely after EDTA extraction.The extraction efficiency of EDTA on the acid-extractable fraction was significant in shallow soil column,while in deeper soil column,a descent of the extraction efficiency on reduced,oxidizable and residual fractions was obtained.And heavy metals chelated by EDTA were more easily desorption by soil particles with the depth of the soil columns increased.