富铁土壤或沉积物等环境介质中铁氧化物形成与转化是影响介质中物质循环的重要土壤环境地球化学过程。近年来，铁同位素作为元素迁移转化指示剂在研究土壤物质循环过程中表现极大的优越性，但由于铁氧化过程的复杂性及铁稳定同位素分析限制，微生物亚铁氧化成矿急需以铁稳定同位素手段跟踪性研究其过程机制。本项目以不同类型铁氧化菌作用下亚铁氧化成矿过程为对象，研究微生物铁氧化过程中的铁同位素组成特征及分馏机制(与非生物过程对比)，重点研究铁稳定同位素分馏与铁氧化速率、矿物形态、胞外分泌物等关系，建立铁同位素在铁氧化过程中的示踪作用，明确生物与非生物作用贡献；同时，以57Fe标记示踪手段为基础，揭示铁微生物氧化过程中的电子转移机制。预期研究结果将丰富铁的同位素地球化学理论，为铁同位素示踪环境中生命活动痕迹提供依据，并为研究铁氧化耦合其他生源要素循环提供基础理论。

The formation and transformation of iron oxide in iron-rich soil or sediment are important environmental and geochemical processes affecting material cycling in soil. In recent years, iron isotope as an indicator for element migration and conversion has shown great superiority in the study of material cycling in soil. To data, however, the effort to establish a clear Fe isotopic signature in Fe minerals produced by Fe(II)-oxidizing bacteria has been thwarted due to complex mechanisms of iron oxidation and the limitation of iron isotope analysis. The present project is proposed to examine the mechanisms of iron isotope fractionation produced by different type Fe(II)-oxidizing bacteria (compared to abiotic process). Based on the relationship among Fe isotope, iron oxidation rate, mineralogical, and extracellular secretions, Fe isotope as a tracer for microbial Fe(II) oxidation will be established, which may distinguish between Fe(III) minerals that formed via biological or abiotic pathways. In addition, combined Fe isotope with 57Fe tracer approach can explore the mechanism of electron transfer processes during microbial Fe(II) oxidation. These results will enrich the theory of isotope geochemistry of Fe, use to trace the distribution of microorganisms in ancient and modern environments, and provide scientific basis for iron oxidation coupled with nutrient cycling.