College of Science, Huazhong Agricultural University, Wuhan, 430070, China; Agro-Environmental Protection Institute, Ministry of Agriculture of China, Tianjin, 300191, China.
College of Science, Huazhong Agricultural University, Wuhan, 430070, China.
Ecotoxicol Environ Saf. 2019 Oct 30;182:109399. doi: 10.1016/j.ecoenv.2019.109399. Epub 2019 Jul 3.
Soil washing with chelators, a viable method for treating soils contaminated with potentially toxic metals, has drawn increasing attentions. The objective of this study was to determine a new generation of mixed degradable chelating agents from N, N-bis (carboxymethyl) glutamic acid (GLDA), [S, S]-stereoisomer of ethyleneiaminedisucc--inic acid (EDDS), nitrilotriacetic acid (NTA), and citric acid (CA), and to evaluate its effectiveness and feasibility to reduce toxic metals contamination in two different agricultural soils. A comparative leaching test conducted on the four individual degradable chelating agents showed that the capacity of single chelator in mobilizing copper (Cu), zinc (Zn), cadmium (Cd), and lead (Pb) varied significantly. Using a combination of GLDA and NTA was more advantageous than using a single chelating agent in extracting potentially toxic metals. The removal efficiencies of Cu, Zn, Cd, and Pb reached 38.2, 9.8, 71.4, and 19.5% for soil 1, and 25.0, 5.2, 59.7, and 18.5% for soil 2, respectively, at mixed chelator (MC) concentrations of 3 mmol/L (GLDA) and 2 mmol/L (NTA), pH of 6.0, and a contact time of 4.0 h. The effects of washing conditions, chelator concentration, pH values, and contact time on the removal efficiencies of target toxic metals were investigated. The results showed that the combined chelating agent has a lower pH dependence, making it feasible for a wider range of applications. The effects of the chelating agents on the morphological distribution of potentially toxic metals and the soil enzyme activity before and after the treatments were also studied. After washing, the content of the water-soluble, acid-soluble, reducible, and oxidizable target metals showed a certain degree of decrease. Although the activities of catalase, urease, and invertase appeared to be inhibited during a short period of time, their activities were stimulated and later promoted with the degradation of the chelating agent. In general, the chelating agent combination has a great potential for toxic metals leaching.
采用螯合剂进行土壤淋洗是一种处理受潜在有毒金属污染土壤的可行方法，越来越受到关注。本研究的目的是从 N，N-双（羧甲基）谷氨酸（GLDA）、[S，S]-乙二胺二琥珀酸（EDDS）的立体异构体、氮三乙酸（NTA）和柠檬酸（CA）中确定新一代混合可降解螯合剂，并评估其在两种不同农业土壤中降低有毒金属污染的效果和可行性。对四种单一可降解螯合剂进行的比较淋洗试验表明，单一螯合剂在动员铜（Cu）、锌（Zn）、镉（Cd）和铅（Pb）方面的能力差异显著。使用 GLDA 和 NTA 的混合物比使用单一螯合剂更有利于提取潜在有毒金属。在混合螯合剂（MC）浓度为 3 mmol/L（GLDA）和 2 mmol/L（NTA）、pH 值为 6.0 和接触时间为 4.0 h 时，土壤 1 中 Cu、Zn、Cd 和 Pb 的去除效率分别达到 38.2%、9.8%、71.4%和 19.5%，土壤 2 中分别达到 25.0%、5.2%、59.7%和 18.5%。研究了洗涤条件、螯合剂浓度、pH 值和接触时间对目标有毒金属去除效率的影响。结果表明，该复合螯合剂具有较低的 pH 值依赖性，因此具有更广泛的应用范围。还研究了螯合剂对潜在有毒金属的形态分布和处理前后土壤酶活性的影响。洗涤后，目标金属的水溶性、酸溶性、可还原和可氧化含量均有一定程度的降低。虽然在短时间内，过氧化氢酶、脲酶和转化酶的活性似乎受到抑制，但随着螯合剂的降解，它们的活性受到刺激并随后得到促进。总的来说，该螯合剂组合在有毒金属浸出方面具有很大的潜力。
