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研究报告

Manganese enhances the Cd immobilization by the biological soil crusts in paddy fields

基金项目：国家自然科学基金（No.41401260）；湖南农业大学大学生科技创新项目（No.2017ZK34）；湖南省自然科学基金（No.2017JJ2112）

摘要：为了解在不同浓度的锰盐作用下生物土壤结皮对稻田灌溉水中镉的固定作用及机制，将不同浓度的硫酸锰、镉溶液与稻田生物土壤结皮混合，并在实验室内培养15 d.通过分析生物土壤结皮中不同形态的锰、镉的量，探究不同浓度锰盐对土壤结皮中镉的固定及分布的影响.结果表明：锰盐能有效地促进生物土壤结皮固定镉，随着锰盐浓度的增加，生物土壤结皮对镉的去除效率增加.在20.00 mg·L^-1硫酸锰条件下，生物土壤结皮对水中镉离子去除率达到98.20%，镉主要以非乙二胺四乙酸可提取的矿物形态存在.通过扫描电子显微镜-电子散射能谱及X射线光电子能谱分析，锰被锰氧化菌氧化成类似水钠锰矿的多孔海绵状物质，镉富集固定在晶格中.本研究对利用生物土壤结皮净化镉污染灌溉水提供了新的思路.

Abstract：The effect of biological soil crust (BSC) on the immobilization and removal of heavy metal from irrigation water is an important issue. BSC was cultured in solutions with different concentrations of manganese (Mn) salt and cadmium (Cd) sulfate for 15 days. We analyzed the Mn, Cd, and Fe contents in the BSC and investigated the effects of Mn salt on the Cd distribution in different binding-forms in BSC as well. The results show that Mn salt was effective at enabling BSC to immobilize the Cd, and its removal efficiency from irrigation water improved with increased Mn concentration. The removal of 50.00 μg·L^-1 of Cd from irrigation water by BSC reached as high as 98.20% when 20.00 mg·L^-1 of Mn was applied. Based on the SEM-EDS and XPS analyses, it is reasonably inferred that the Mn ion was oxidized by Mn oxidizing bacteria, to yield the porous spongy-like birnessite, while Cd was scavenged and immobilized in the crystal lattice. This study provides evidence for a potentially novel method to decontaminate irrigation water polluted with Cd by using BSC.