螯合剂诱导下污染土壤溶液中TOC和重金属的动态变化及其相关性

TOC AND HEAVY METALS DYNAMIC IN CONTAMINATED SOIL SOLUTION AND THEIR CORRELATIONS WITH THE ADDITION OF CHELATING AGENTS

采用土培盆栽试验研究了EDTA,NTA(氨三乙酸)和EDDS(乙二胺二琥珀酸)三种螯合剂诱导下,土壤溶液中总有机碳(TOC)含量和重金属浓度的动态变化以及二者之间的关系.结果表明,施用5mmol.kg-1螯合剂能极显著地增加土壤溶液中TOC的含量和Cu,Zn,Cd,Pb的浓度.土壤溶液TOC含量从第2天达最大后就随时间呈一阶指数衰减函数y=y0+Ae(x-x0)/t变化,衰减因子大小顺序为tEDTA>tNTA>tEDDS.土壤溶液中Cu,Zn,Cd和Pb浓度的动态变化也有与TOC相似的规律,并且两者呈显著线性正相关.结果还表明,螯合剂对重金属的活化能力与其相应金属螯合物的稳定常数lgKMe基本一致,为EDTA>EDDS>NTA,因此,在螯合诱导强化植物提取中NTA和EDDS的潜在环境风险比EDTA要小.

Total organic carbon（TOC）and metals Cu, Zn, Cd and Pb concentration in contaminated soil solution and their correlations with the addition of three chelating agents EDTA, NTA and EDDS were studied in pot experiments. The results showed that the TOC and Cu, Zn, Cd and Pb concentration in soil solution were significantly increased with the application of chelating agents at the dosage of 5 mmol·kg^-1 soil. TOC content in soil solution reached the maximum value in the second day since the addition of chelating agents and subse- quently its dynamic fit the first order exponential decay and the attenuation coefficient with the order of tEDTA 〉 tNTA 〉 tEDDS for EDTA, NTA and EDDS. The similar trend as TOC was found for the concentration of Cu, Zn, Cd and Pb dynamic in soil solution and there were the significantly linear positive correlations between them. Furthermore, the solubilization abilities of three chelating agents EDTA, NTA and EDDS on Cu, Zn, Cd and Pb were almost consistent with their stability constants of the metal-complexes with the order of EDTA 〉 EDDS 〉 NTA. It indicated that environmental risk of NTA and EDDS were less than that of EDTA in chelate-induced phytoextraction.