Characterization of redox reactions and phase transformation processes at iron mineral surfaces

地下水中高度生物可利用的铁相在表面结合的Fe（II）被非生物过程再氧化的条件下形成。这种铁相，虽然大多数只作为表面涂层存在，但被认为是通过介导非均相氧化和还原过程来支持电子循环的工具。通过它们对溶解的亚铁的高亲和力，铁（氢）氧化物的表面可以同时作为化学和微生物过程的电子供体和电子受体。直到最近，铁矿物在还原环境中的表面性质和表面拓扑结构的高动态才得到充分认识。在这里，我们专注于提高对铁矿物发生的非均相氧化还原反应和随后的相变的理解。然而，用现有的光谱方法原位表征矿物表面活性氧化还原物种的类型和动力学，如果可行的话，是非常困难的。因此，我们建议在这里开发，验证和应用一种间接的方法（反应示踪剂的方法）的基础上的变化的稳定同位素组成的模型氧化剂反应，具体与表面结合的Fe（II）物种。使用这种新的方法，我们打算表征的属性，形成的动力学，并最终在地球化学相关的设置与实验进行良好的控制条件下，在批处理和列系统的活性铁涂层的意义。

Highly bioavailable iron phases in groundwater form at conditions where surface bound Fe(II) is re-oxidized by abiotic processes. Such iron phases, though mostly present only as surface coatings, are thought to be instrumental in supporting an electron cycle by mediating heterogeneous oxidation and reduction processes. Through their high affinity for dissolved ferrous iron, surfaces of iron (hydr)oxides may act as electron donors and electron acceptors at the same time both for chemical and microbial processes. Only recently the high dynamics of surface properties and surface topologies of iron minerals in reducing environments has been fully recognized. Here, we focus on an improved understanding of heterogeneous redox reactions and subsequent phase transformations taking place at iron minerals. In situ characterization of the type and the dynamics of active redox species at mineral surfaces with existing spectroscopic methods, however, is very difficult if feasible at all. We therefore propose here to develop, validate and apply an indirect method (reactive tracer approach) based on changes of the stable isotopic composition of model oxidants reacting specifically with surface bound Fe(II) species. Using this novel approach we intend to characterize the properties, the dynamics of formation and eventually the significance of reactive iron coatings at geochemically relevant settings with experiments conducted under well controlled conditions in batch and column systems.