超声波强化EDTA-Na_2对土壤中Pb、Cd去除效果及形态变化的影响

Effect of ultrasound-enhanced EDTA-Na_2 methods on removal rates and speciations of Pb and Cd in soil

通过3种洗脱方式(TE,EDTA-Na2传统洗脱方式;UE-1,超声波先作用于土壤后再加入EDTA-Na2洗脱;UE-2,超声波强化EDTA-Na2洗脱)对湖南典型矿区周边重金属复合污染农田土壤进行洗脱处理,研究了3种洗脱方式对土壤中Pb和Cd的洗脱效果及洗脱前后土壤中Pb和Cd的形态分布。结果表明:3种洗脱方式均对土壤中Pb和Cd有较好的洗脱效果,其中UE-2对土壤中Pb和Cd洗脱率均大于TE和UE-1;在作用时间为5~480 min时,UE-2对郴州土壤中Pb和Cd的洗脱率分别为43.9%~55.9%和63.6%~74.4%,对衡阳土壤中Pb和Cd的洗脱率分别为63.1%~80.9%和74.7%~86.7%,相对于传统萃取方式(TE),UE-2洗脱方式使土壤中Pb和Cd的洗脱率提高了将近25%;与未洗脱土壤相比,UE-2洗脱方式能显著降低土壤中Pb的Fe-Mn氧化物结合态和残渣态含量,显著降低Cd的残渣态、Fe-Mn氧化物结合态和酸可提取态含量;UE-2洗脱方式能显著降低土壤中Cd的TCLP提取态含量,而使Pb的TCLP提取态含量有所增加。

The purpose of this study was to study the removal rates of soil Pb and Cd and the changes in species of these two elements before and after extracting with three methods（TE,traditional extracting soil with EDTANa_2 solution;UE-1,ultrasonic waves applied to soils first and then extracting soils with EDTA-Na_2 solution;UE-2,ultrasonic waves and EDTA-Na_2 solution applied together for soil extraction）.The two tested soils were collected from two paddy soils polluted with heavy metals near the mining areas from Chenzhou and Hengyang,southern Hunan.BCR extraction procedures were employed to study changes in species of soil Pb and Cd.The experiment results indicated that all three extracting methods showed good removal rates for soil Pb and Cd,and the removal rates of UE-2 was better than those of TE and UE-1.Compared to TE（the traditional extracting soil with EDTA-Na_2 solution）,the removal rates of UE-2 increased about 25%.During 5 to 480 minutes of extracting time,the removal rates of UE-2 were from 43.9% to 55.9% and 63.6% to 74.4% for Pb and Cd in Chenzhou soil,and were from 63.1% to 80.9% and 74.7% to 86.7% for Pb and Cd in Hengyang soil,respectively.Compared to the soils before extracting,UE-2 extracting obviously decreased soil Pb contents in Fe-Mn oxide and residual fractions,and soil Cd contents in residual,Fe-Mn oxide,and acid-extractable fractions.UE-2 extracting evidently decreased TCLP extractable content of soil Cd,but increased that of soil Pb.