南方稻田根际铁循环耦合砷形态转化机制及调控研究

Arsenic (As) contamination in paddy soils in the south of China has receiving increasing concern, as it caused serious rice contamination which affecting the health of millions of people that relies on rice as a staple food. Arsenic biogeochemical processes in soils have important implication on arsenic contamination control, as rice rhizosphere redox conditons, iron minerals and related bacteria communities have affected arsenic speciation transformation. The aim of the present project is to investigate the Fe(II)-oxidizing bacteria (FeOB) and Fe(III)-reducing bacteria (FeRB) abundance in rice rhizosphere and study their effects on iron cycle and related As chelating; to elucidate the effects of extracellular electron transfer（EET）among microbe-mineral on iron metabolisms and related arsenic speciation transformation mechanisms; to study the effects of different conditions on iron mineral formation and its relationship with As speciation transformation, and to finally formed microbe-iron mineral combined technology for the remediation of paddy soil arsenic contamination. The potential results of this project will bridge the research gap in arsenic biogeochemical processes and finally reduce the health risks posed by As contamination of paddy soils.

水稻是我国第一大粮食作物，水稻土砷污染已成为我国特别是南方地区突出且急需解决的重大环境问题。稻田根际氧还条件、含铁矿物和微生物会影响砷在土壤中的移动性和生物有效性，系统研究土壤中砷的生物地球化学行为是降低水稻砷污染环境风险的重要突破口。本项目拟研究南方典型砷污染农田嗜中性铁氧化细菌和异化铁还原菌对水稻根际铁循环与砷结合形态的影响；阐明含铁矿物-微生物耦合的胞外电子传递过程对铁的生物成矿耦合砷钝化的影响机制；研究不同条件下含铁矿物矿相转变对砷形态迁移转化的作用，并基于此形成污染农田的微生物-含铁矿物强化联合稳定修复技术。本项目的开展将丰富砷的生物地球化学理论，并为最终降低土壤砷的生物有效性和环境风险提供理论和应用依据。

水稻是我国第一大粮食作物，水稻土砷污染已成为我国特别是南方地区突出且急需解决的重大环境问题。稻田根际氧还条件、含铁矿物和微生物会影响砷在土壤中的移动性和生物有效性，系统研究土壤中砷的生物地球化学行为是降低水稻砷污染环境风险的重要突破口。本项目阐明了砷污染稻田土壤铁氧化细菌和异化铁还原菌对铁氧化物矿物生成耦合砷固定的影响及其机制；采用电化学分析方法阐明了含铁矿物-有机质-微生物耦合的电子传递过程对稻田砷转化的作用，丰富了砷的生物地球化学理论；研发了经济高效的铁基生物炭材料，铁基生物炭和铁氧化菌处理砷污染稻田后稻米砷含量均能达到国家食品安全标准限值，且两者协同处理效果最好，可望解决南方稻田砷稳定化难题，相关研究成果已在农田修复工程项目进行了示范应用。项目在南方稻田根际铁循环耦合砷形态转化机制及调控研究方面取得了一系列创新性成果，对南方稻田砷污染防控具有重要的理论意义和科学价值。