三种螯合剂对芥菜修复铀镉复合污染土壤的影响

为探讨螯合剂对植物修复的影响,采用模拟土壤铀镉复合污染的盆栽试验,研究3种可降解螯合剂乙二胺二琥珀酸(EDDS)、草酸(OA)和柠檬酸(CA)在不同浓度(0、2.5、5.0、7.5 mmol·kg~(-1))下对芥菜吸收、转运、富集铀和镉的影响。结果表明:芥菜生长受螯合剂种类及浓度的影响,其中EDDS对芥菜有较强的毒害效用,且与浓度呈正效应,而低浓度的(2.5 mmol·kg~(-1))CA、OA均促进芥菜的生长,高浓度(7.5 mmol·kg~(-1))出现抑制;螯合剂促进芥菜对铀和镉的吸收、转运,其中,在7.5 mmol·kg~(-1)CA处理时,芥菜地上部、单株铀含量均达到峰值,分别为9.71、20.63 mg·kg~(-1)DW,是对照的6.03、2.84倍。在5.0 mmol·kg~(-1)EDDS处理时,芥菜地上部、单株镉含量达到峰值,分别为382.2、328.2 mg·kg~(-1)DW,是对照的4.67、2.35倍。在7.5 mmol·kg~(-1)CA处理下,芥菜的铀转运系数最高为0.118,是对照组的2.93倍,而EDDS处理下镉的转运效果较佳。从单株铀、镉富集量来看,CA促进芥菜富集铀的效果最佳,而EDDS促进芥菜富集镉的效果最佳,同时,对铀也有一定效用;此外,CA、EDDS的添加分别增强了土壤中铀镉的有效态含量。综合而言,施加适宜浓度的螯合剂能够提升芥菜对铀镉复合污染土壤的修复效率。

Effects of three kinds of chelating agents on U and Cd phytoremediation in Brassica juncea L.

To explore the effects of chelating agents on phytoremediation in U-Cd contaminated soil, a pot experiment was performed to study the effects of 3 chelating agents(EDDS, OA, and CA)and their additive concentrations(0, 2.5, 5.0, and 7.5 mmol·kg^-1)on U and Cd extraction, translocation, and accumulation in Brassica juncea L. The growth of B. juncea was affected by the type and concentration of chelating agents. EDDS was strongly toxic to B. juncea and its positive effects increased with concentration. The application of 2.5 mmol·kg^-1 OA and CA increased the net weight of B. juncea. The addition of 7.5 mmol·kg^-1 OA and CA inhibited the growth of B. juncea. The chelating agents had a positive effect on U and Cd uptake and translocation in B. juncea. Applying 7.5 mmol·kg^-1 CA maximally increased the U content by 6.03 times and 2.84 times of the original aboveground and total content, with levels of 9.71 mg·kg^-1 and 20.63 mg·kg^-1, respectively, attained. Applying 5.0 mmol·kg^-1 EDDS increased the Cd content by 4.67 times and 2.35 times the original aboveground and total content, with levels of 382.2 mg·kg^-1 and 328.2 mg·kg^-1, respectively, attained. The maximum value of the U translocation factor(0.118)was achieved when CA concentration was 7.5 mmol·kg^-1, 2.93 times that of CK. EDDS had the greatest effect on the transport of Cd. Based on the results of U and Cd bioaccumulation, it was concluded that CA had the greatest effect on the accumulation of U, while EDDS had the greatest effect on the accumulation of Cd and also affected that of U. The addition of CA and EDDS, respectively, enhanced the available content of U and Cd in soil. These results suggested that chelating agents could improve the efficiency of phytoremediation with B. juncea in soil contaminated with U and Cd.