Collaborative Research: Recrystallization of Stable Iron Oxides in Reducing Environments

铁（Fe）氧化物在土壤、沉积物和岩石中含量丰富。像大多数矿物一样，氧化铁矿物随着环境的变化而发生转化反应。这些转化可能导致有毒微量元素、金属和生物营养素的掺入或释放，从而影响水质。这种转变也可能改变氧化物的同位素组成，这通常被用来重建地球上过去的环境条件。拟议的工作将调查最近确定的，不充分的特点铁氧化物转化反应：“稳定的铁氧化物重结晶”。该过程涉及固体Fe氧化物矿物，其在还原条件下与溶液中的溶解离子进行元素和同位素交换，这令人惊讶地显示在氧化物的结构、纹理或粒度没有任何明显变化的情况下发生。建议的工作的目标是确定如何以及在什么条件下发生稳定的氧化铁重结晶两种常见的氧化铁矿物：针铁矿和磁铁矿。该项目的成果可能从根本上改变我们对氧化铁矿物反应的理解，对现代和古代地球上的地球表面过程具有重要意义。为了研究这一过程，这个跨学科的团队将联合收割机放射性同位素示踪实验与光谱，高分辨率显微镜和孔隙尺度分析相结合。这种方法将使我们能够跟踪重结晶率，程度和空间分布的几个天然和合成的铁氧化物具有不同的颗粒大小，微量元素含量和重结晶的历史。实现我们的研究目标将导致：（一）更有效的地下水补救战略，通过提高铁氧化物如何与有毒微量金属和放射性核素在一系列地球化学条件下相互作用的知识;（二）通过研究铁氧化物同位素特征如何随时间变化，改善对地球上过去环境条件的评估;和（iii）对其他矿物观察到的类似的、知之甚少的再结晶过程的洞察。除了通过将这项研究纳入课程和同行评议的出版物来传播成果外，该项目还将支持为6-8年级学生实施为期一周的年度夏令营计划-“科学发掘：肮脏的细节”-这将为儿童，以STEM为重点的本科生和K-12教师提供教育机会。

Iron (Fe) oxides are abundant in soils, sediments, and rocks. Like most minerals, Fe oxide minerals undergo transformation reactions as their surroundings change. These transformations can result in the incorporation or release of toxic trace elements, metals, and biological nutrients, which affect water quality. The transformations may also alter an oxide's isotopic composition, which is often used to reconstruct past environmental conditions on Earth. The proposed work will investigate a recently identified, insufficiently characterized Fe oxide transformation reaction: "stable Fe oxide recrystallization". This process involves a solid Fe oxide mineral that undergoes elemental and isotopic exchange with dissolved ions in solution under reducing conditions, which surprisingly has been shown to occur without any obvious changes in the oxide's structure, texture, or particle size. The goal of the proposed work is to determine how and under what conditions stable Fe oxide recrystallization occurs for two common Fe oxide minerals: goethite and magnetite. The outcomes of this project could fundamentally change our understanding of Fe oxide mineral reactions with important implications for earth surficial processes on both modern and ancient Earth.To study this process, this interdisciplinary team will combine radioactive isotope tracer experiments with spectroscopic, high-resolution microscopic, and pore-scale analyses. This approach will allow us to track recrystallization rates, extents, and spatial distributions for several natural and synthetic Fe oxides with different particle sizes, trace element contents, and recrystallization histories. Achieving our research goal would lead to: (i) more effective groundwater remediation strategies by improving knowledge of how Fe oxides interact with toxic trace metals and radionuclides under a range of geochemical conditions; (ii) improved assessments of past environmental conditions on Earth by examining how Fe oxide isotopic signatures change over time; and (iii) insights into similar, poorly understood recrystallization processes observed for other minerals. In addition to disseminating results through the incorporation of this research into coursework and peer-reviewed publications, this project will support the implementation of an annual week-long summer camp program for grade 6-8 students - "Science Unearthed: The Dirty Details" - which will provide educational opportunities for children, STEM focused undergraduates, and K-12 teachers.