间作条件下螯合剂对龙葵和大叶井口边草吸收重金属的影响

用室内土培试验方法,在采自田间的Pb、Cd和As复合污染土壤中单作或间作龙葵和大叶井口边草条件下,筛选出修复Pb-Cd-As复合污染土壤较好的种植方式为间作。进一步在间作方式下,研究了外源添加不同浓度EDDS（乙二胺二琥珀酸）、NTA（氨三乙酸）和EDTA（乙二胺四乙酸）对植物吸收Pb、Cd和As的影响。结果表明,间作显著促进了龙葵地上部对Cd的吸收量和大叶井口边草地上部对As的吸收量,间作龙葵地上部吸收Cd和大叶井口边草地上部吸收As含量分别是单作龙葵和大叶井口边草的1.3倍和1.4倍,说明间作龙葵和大叶井口边草比单作更有利于修复Pb-Cd-As复合污染土壤。间作条件下,大叶井口边草对螯合剂的耐性比龙葵更强。3、6、12mmol.kg-1EDTA能极显著增加土壤中Pb、Cd有效态含量,从而促进龙葵地上部对Pb吸收和大叶井口边草地上部对Pb、Cd吸收。EDTA比NTA具有更强的提高土壤Pb、Cd有效态的能力,但对土壤As有效态促进作用与EDTA相比,NTA效果极显著,1.5、3mmol.kg-1NTA处理极显著提高土壤As有效态含量及促进龙葵和大叶井口边草地上部对As吸收。

Effects of Chelators on the Uptake of Heavy Metals by Solanum nigrum and Pteris cretica var.Nervosa Growing in an Intercropping System

Enhancing phytoextraction of heavy metals has been proposed as an effective approach to remove heavy metals from contaminated soils.Plants with different metal-hyperaccumulative characteristics,namely Solanum nigrum and Pteris cretica var.nervosa,were monocropped or intercropped in multiple-metal contaminated field soils in this study.This line of study aims to investigate,compared with monocropping method,whether intercropping method could improve metal uptake by these two tested plants.The effects of ethylene diamine disuccinate（EDDS）,ethylene diamine tetraacetate（EDTA） and nitrilotriacetic acid（NTA） on uptake of heavy metals（Pb,Cd and As） by plants growing in an intercropping system were also investigated using the same soil.Compared with monocropping method,intercropping method increased Cd concentration 1.3 times and As concentration 1.4 times in shoots of S.nigrum and P.cretica var.nervosa,respectively.This result indicated that intercropping method could significantly improve heavy metal uptake by hyperaccumulators.Much higher tolerance to chelators was observed in P.cretica var.nervosa than that in S.nigrum in the intercropping system.The application of 3,6,12 mmol·kg-1 EDTA to soil contaminated with heavy metals significantly increased soil Pb,Cd bioavailability and concentrations of Pb in two intercropped plants.The maximum Pb concentrations reached 27.58 mg·kg-1 and 26.17 mg·kg-1 in S.nigrum and P.cretica var.nervosa,respectively,which were 3.3 times and 3 times higher than that in the corresponding control plants to which no chelators were applied.Under the conditions of the intercropping system,the application of 3,6,12 mmol·kg-1 EDTA also significantly increased Cd concentration in the shoot of P.cretica var.nervosa.EDTA was more effective than NTA in increasing soil Pb,Cd bioavailability,but was less effective than NTA in increasing soil As bioavailability.The application of 1.5 mmol·kg-1 and 3 mmol·kg-1 NTA significantly increased soil As bioavailability as well as the concentrations of As in shoots of two tested plants.