通过温室盆栽试验比较2种螯合剂(EDTA和NTA)的不同施用方式(包括单施和混施,收获前1周一次性施用、收获前2周一次性和分2次施用)对紫茉莉和百日草修复铅污染土壤的强化效应。结果表明:与未加螯合剂的对照相比,螯合剂施用对花卉植物的株高、茎粗和干重均没有显著的影响,但植株地上部铅含量和铅富集系数显著增加;2种花卉植物相比,紫茉莉的地上部平均铅含量和铅富集系数均较百日草低,而铅转移系数则明显高于百日草;不同的螯合剂施用方式相比,收获前2周加入螯合剂处理的植株地上部平均铅含量和铅富集系数均高于收获前1周加入螯合剂的处理,而具体的处理效应则取决于花卉植物的种类以及螯合剂的施用次数和浓度配比;紫茉莉的铅转移系数与其地上部铅含量和铅富集系数的规律性基本一致,且以先施EDTA后施NTA(NTA∶EDTA浓度比1∶2)处理的铅转移系数最高,而百日草的铅转移系数则与其地上部铅含量和铅富集系数的规律性不同。综合植株地上部铅含量和铅富集系数及铅转移系数的结果来看,紫茉莉以收获前2周先施EDTA、1周后再施用NTA、且NTA∶EDTA浓度比为1∶2时,对于铅污染土壤能达到最佳的修复效果。
A greenhouse pot experiment with Mirabilisjalapaand Zinnia elegans was conducted to compare the enhanced effect of different application methods of chelating agents(EDTA and NTA)on phytoremediation of lead-contaminated soil.The application methods of chelating agents included single or combined application of chelating agents,application once one week before harvest,and application once or twice two weeks before harvest.The results showed that,compared with the treatments without chelating agents,the addition of the chelating agents had generally not significant influence on the plant height,stem diameter and dry weight of the ornamental plants,while the content and bioaccumulation coefficient of Pb in the shoot of the ornamental plants significantly increased.The average values of the content and bioaccumulation coefficient of Pb were lower in the shoot of Mirabilis jalapathan that in the shoot of Zinnia elegans,whereas the Pb translocation factor of the former was higher than the latter.For the different application methods of chelating agents,the average Pb content and Pb bioaccumulation coefficient were higher in the treatments with chelating agents application two weeks before harvest than those with chelating agents application one week before harvest.However,the treatment effects under chelating agents application two weeks beforeharvest simultaneously depended on the species of the ornamental plants,the frequencies of chelating agents application,and the application ratios between the two chelating agents.The regularity of Pb translocation factor was consistent with that of Pb content and Pb bioaccumulation for Mirabilis jalapa,while it was not consistent for Zinnia elegans.In conclusion,for Mirabilis jalapa,the optimal remediation effect could be obtained under the following application methods of chelating agents:EDTA was applied at first two weeks before harvest,then NTA was applied one week after EDTA,and the application ratio of NTA to EDTA was 1∶2.