CAREER: Nanoscale Mineral Transformations During Biogeochemical Cycling and the Fate of Trace Elements and Nutrients

沉积物、土壤和水生系统中磷和微量元素的有效性和形态受到涉及铁和锰氧化物矿物的生物地球化学循环的强烈影响。通常认为，这些相通过吸附和共沉淀等被动手段影响这些元素的命运。虽然铁的氧化物在生物地球化学循环过程中的矿物结构变化及其对微量元素和营养盐命运的影响已经得到了很好的研究，但对于锰系来说，类似的研究普遍缺乏。与铁类似，发生活跃的生物地球化学锰循环的环境通常含有共存的水相锰(II)和固体锰(III/IV)氧化物。然而，这些锰矿物的片层结构和络合组成以及锰发生络合反应的能力表明，锰氧化物比铁氧化物更多地参与界面原子交换和电子转移反应，并可能导致体相结构转变。锰氧化物的这种化学和结构修饰可能会对生物地球化学系统中痕量元素和磷的去向产生重大影响。这一提议的主要研究目标是扩大我们对原子交换和电子转移反应如何驱动纳米级矿物转变以及影响微量元素和养分命运的理解。皮？S的目标将通过一系列系统研究来实现，这些研究将以实验室为基础的湿化学与固体整体和表面结构以及相关微量元素和磷酸盐的形态的高级化学和结构表征相结合。拟议的研究活动将展示一类新的矿物转化以及在生物地球化学循环中的微量元素和营养反应的运作。这项工作将提高我们对沉积物、土壤和水生系统中铁和锰循环如何影响磷酸盐和微量营养素的有效性以及污染物的去向的理解。拟议的研究将在识别影响污染物去向和迁移的新过程、建议新的修复方法以及启发电池材料的新合成路线方面提供潜在的社会效益。更重要的是，这份职业建议书中描述的研究将被用来加强一些教育活动。这些活动是在本科和高中阶段围绕研究性学习这一主题组织的。拟议的研究活动将积极用作本科生和高中生的学习活动。这些研究性教育活动将在皮？S研究组、部门以及通过制定和实施评估计划为高中生提供研究机会的当地项目中得到改进和优化。将开发一门新的地质学与人类健康本科课程，其中包括探究式学习和水相地球化学课程的探究式学习模块。课程材料、教学方法和研究成果将通过网站、博客和在科学和教育期刊上发表广泛传播。

The availability and speciation of phosphate and trace elements in sediments, soils, and aquatic systems are strongly affected by biogeochemical cycling involving iron and manganese oxide minerals. These phases are commonly thought to affect the fate of such elements through passive means such as adsorption and coprecipitation. While mineral structural transformations during biogeochemical cycling and their impact on trace element and nutrient fate are well studied for the iron oxides, analogous studies are generally lacking for the Mn system. Similar to iron, environments where active biogeochemical Mn cycling is occurring often contain coexisting aqueous Mn(II) and solid Mn(III/IV) oxides. However, the lamellar structure and complex composition of these manganese minerals and the ability of Mn to undergo complex reactions, suggest that interfacial atom exchange and electron transfer reactions will be more involved for Mn oxides than for Fe oxides and likely lead to bulk structural transformations. Such chemical and structural modification of Mn oxides may have a substantial impact on the fate of trace elements and phosphate in biogeochemical systems. The primary research objective of this proposal is to expand our understanding of how atom exchange and electron transfer reactions drive nanoscale mineral transformations and affect trace element and nutrient fate. The PI?s objectives will be accomplished through a series of systematic studies that combine laboratory-based wet chemistry with advanced chemical and structural characterization of the solid bulk and surface structures and the speciation of associated trace elements and phosphate. The proposed research activities will demonstrate the operation of a new class of mineral transformations and trace element and nutrient reactions during biogeochemical cycling. This work will improve our understanding of how Fe and Mn cycling in sediments, soils, and aquatic systems affect phosphate and micronutrient availability and the fate of contaminants.The proposed research will provide potential societal benefits in the form of identifying new processes affecting contaminant fate and transport, suggesting new remediation approaches, and serving as inspiration for novel synthesis routes for battery materials. More importantly, the research described in this CAREER proposal will be leveraged to enhance a number of educational activities. These activities are organized around a theme of inquiry-based learning at the undergraduate and high school level. The proposed research activities will be actively used as learning activities for both undergraduate and high school students. These research-based educational activities will be improved and optimized in the PI?s research group, department, and for a local program providing research opportunities to high school students through the development and implementation of assessment plans. A new undergraduate course on Geology and Human Health that incorporates inquiry-based learning and inquiry-based learning modules for an aqueous geochemistry course will be developed. Course materials, pedagogical approaches, and research results will be widely disseminated through websites, blogs, and publication in scientific and education journals.