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研究报告

王亚洁,朱永官,孙国新,陈正.铁还原菌shewanella oneidensis MR-1对根表铁膜中砷运移的影响[J].环境科学学报,2015,35(7):2240-2246

Effects of iron-reducing bacteria on arsenic releasing from iron plaque on rice root surface

摘要：水稻根表铁膜是控制砷在根际-植物体系转运的重要区域,但是其中铁还原微生物对砷运移的作用并不清楚.实验以吸附砷磷的水铁矿以及野外采集水稻根系为研究对象,分析铁还原菌Shewanella oneidensis MR-1还原铁膜内铁氧化物过程中,铁还原、砷释放和固定速率.研究表明铁还原菌Shewanella oneidensis MR-1可以将水稻根表铁膜中的Fe(Ⅲ)快速还原为Fe(Ⅱ)并释放到溶液中.溶液中的砷在48 h内达到最大值18 μmol·L^-1,之后逐渐下降,120 h之后,与最大值相比减少了约60%.利用吸附砷的水铁矿模拟铁膜砷释放过程发现,微生物的固定作用是造成溶液中砷含量下降的主要原因之一.本研究表明,促进根际微生物的大量生长,可能是降低土壤环境中砷风险的途径之一.

Abstract：Iron plaque on rice roots controls arsenic (As) movement from soils to roots in the paddy fields. Although it is well known that iron-reducing bacteira are able to dissolve iron oxides, their role in rice rhizosphere is unclear. In this study, rice roots collected from polluted paddy fields and ferrihydrite adsorbing As or phosphate (P) were used as iron sources to support biological iron reduction. Arsenic is released through the Fe oxides reduction processes catalyzed by Shewanella oneidensis MR-1. Experiments showed that the Fe plaque was quickly reduced and released into the solution in the presence of Shewanella oneidensis MR-1. Arsenic in Fe plaque was also simultaneously released and the concentration reached 18 μmol·L^-1 within 48 hours. As concentration then gradually decreased and was reduced by about 60% after 120 hours. The As-loaded ferrihydrite was used to simulate the process of As release from iron plaque. Results showed that microbial absorption was one of the main causes of the decline of arsenic in solution, and implied that promoting the rhizosphere microorganism growth could reduce the risk of As in the soil environment.