Microscopic and Molecular Characterization of Fe and Mn Hydrous Oxides

Fe 和 Mn 水合氧化物的微观和分子表征

• 批准号: 9815090
• 负责人: Jean-Francois Gaillard
• 金额: $ 21万
• 依托单位: Northwestern University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-01-01 至 2002-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9815090&HistoricalAwards=false
• 关键词: Microscopic; Molecular; Characterization; Fe; Mn

9815090GaillardThe overall objective of this proposal is to determine the elemental composition,redox speciation, and the molecular nature of iron and manganese oxides that are formed at oxic/anoxic transitions in aquatic systems. In particular, we are primarily interested in obtaining nanoscale information on the morphology, structure, and reactivity of environmental particles as well as molecular information on the mineral phases/assemblages that comprise these particles. Our central hypothesis is that the existence of mixed valence states of Fe and Mn governs the reactivity of these authigenic iron and managanese phases. This investigation will focus on particles formed at the semi-permanent oxic/anoxic transition present in a small lake characterized by a biogenic meromixis: Paul Lake (MI).To reach these objectives we shall use a combination of microscopic and spectroscopic methods. Paul Lake particles will be collected and prepared for microscopic observations using SEM and TEM. The elemental composition of individual particles will be determined, at the nano-scale, using either EDS or EELS. Concurrently, the changes of the local molecular environment of selected metals in the particles will be probed using in situ X-Ray Absorption Fine Structure XAFS techniques.The expected result of this research is a better characterization of the particlesthat are formed at oxic/anoxic transitions in aquatic systems. The chemical composition, redox speciation, and molecular structure of these particles will provide valuable information for predicting the fate of metals and exotic chemicals that bind selectively to these particulate phases.

9815090 Gaillard本提案的总体目标是确定元素组成，氧化还原形态，以及在水生系统中的好氧/缺氧过渡形成的铁和锰氧化物的分子性质。 特别是，我们主要感兴趣的是获得纳米级的形态，结构和环境颗粒的反应性，以及矿物相/组合，包括这些颗粒的分子信息。 我们的中心假设是，铁和锰的混合价态的存在下，这些自生铁和锰相的反应性。 本次调查将集中在颗粒形成的半永久性的好氧/缺氧的过渡目前在一个小湖泊的特点是一个生物的meromixis：保罗湖（MI）。为了达到这些目标，我们将使用显微镜和光谱方法相结合。 将收集Paul Lake颗粒，并准备使用SEM和TEM进行显微镜观察。 将使用EDS或EELS在纳米尺度上确定单个颗粒的元素组成。 同时，还将利用原位X射线吸收精细结构XAFS技术研究颗粒物中某些金属的局部分子环境的变化，以期更好地表征水体中在好氧/缺氧转换过程中形成的颗粒物。 这些颗粒的化学组成、氧化还原形态和分子结构将为预测选择性地与这些颗粒相结合的金属和外来化学物质的命运提供有价值的信息。