螯合剂强化棉花对镉污染土壤修复的初步研究

Preliminary Study on Chelate-enhanced Phytoremediation of Cadmium-contaminated Soil by Cotton Plants

采用土壤盆栽试验研究了4种有机螯合剂柠檬酸（CA）、乙二胺四乙酸（EDTA）、乙二醇双四乙酸（EGTA）和乙二胺二琥珀酸（EDDS）在不同添加量（0,2.5,5,7.5mmol/kg）时对棉花修复镉（Cd）污染土壤的影响。结果表明,添加螯合剂显著提高了土壤水溶态Cd的含量,添加EDTA、EGTA、EDDS 3种螯合剂,使水溶态Cd含量分别提高了46.5-92.2,52.0-101.1,16.7-84.1倍,其中EGTA增加的幅度最大。棉花生长受有机螯合剂种类和添加量的影响,EDDS和EDTA在高添加量（7.5mmol/kg）时对棉花产生较大的毒害作用,但在培养期内添加螯合剂对植株生物量无显著影响。使用螯合剂显著促进棉花植株Cd含量和地上部分的积累量,其中以EGTA处理效果最佳,地上部Cd含量为对照（CK）的4.01-5.20倍。从地上部Cd积累量和转运系数来看,4种螯合剂EGTA效果最好,CA效果最差。依据研究结果,棉花可作为土壤Cd污染修复植物使用,在植株收获前7d左右添加EGTA螯合剂可有效提高棉花对Cd污染土壤的修复效率。

A pot experiment was conducted to study the effects of 4chelating agents（CA,EDTA,EGTA and EDDS）and their additive concentrations（0mmol/kg,2.5mmol/kg,5mmol/kg and 7.5mmol/kg）on cotton seedling growth,and Cd concentration,accumulation and translocation in cotton plants.The results showed that the concentration of water-extractable Cd in soil was increased significantly by addition of chelating agents.Compared with the control treatment,EDTA,EGTA and EDDS increased the concentration of water-extractable Cd by 46.5to 92.2times,52.0to 101.1times and 16.7to 84.1times,respectively,and therefore the increases induced by EGTA were the most significant.Cotton seedling growth was influenced by the type and additive concentration of chelating agents.High additive concentration of EDDS and EDTA（7.5 mmol/kg）showed toxic effects on cotton plants.However,the addition of chelating agents did not significantly affect plant biomass during the period of cotton planting.The addition of chelating agents significantly increased Cd concentration in cotton plants and promoted accumulation of Cd in shoots,especially for EGTA treatment,in which shoot Cd concentration was 4.01 to 5.20 times as much as that in the control treatment.According to the results about shoot Cd accumulation and translocation factor,we can conclude that the promotion of EGTA was the best,while that of CA was the worst,for phytoremediation of Cd-contaminated soil by cotton plants.The results indicated that the phytoremediation of Cd-contaminated soil by cotton plants could be effectively enhanced when EGTA was added into soil about 7dbefore cotton harvest.