Iron isotope fractionation in solution

溶液中铁同位素分馏

• 批准号: 0643286
• 负责人: Edwin Schauble
• 金额: $ 18.44万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-07-01 至 2010-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0643286&HistoricalAwards=false
• 关键词: Iron; isotope; fractionation; solution

EAR-0643286SCHAUBLEIron-isotope signatures are a common feature in natural materials that are created or react at low temperatures. These signatures are of great interest in low-temperature geochemistry and geobiology because iron is a vital nutrient, and its oxidation state is a potential indicator of modern and ancient redox conditions. One aspect of iron-isotope geochemistry that is not understood very well is the possibility that large fractionations occur between different species in solution. This proposal describes four sets of experiments and corresponding theoretical calculations to determine equilibrium iron isotope (56Fe/54Fe) fractionations in chloride-bearing solutions. This research will help create a framework for better understanding natural processes that give rise of iron isotope signatures in nature, particularly in distinguishing possible influences of biology and crystallization from solute composition effects. Experiments will exploit the unique solubility of the FeCl4- complex in hydrophobic organic solvents (e.g., diethyl ether), quantifying changes in 56Fe/54Fe partitioning in aqueous solution by measuring variation in the fractionation between aqueous iron and coexisting ether-dissolved FeCl4-. Aqueous speciation modeling and calculation of isotopic partition function ratios of dissolved species will be used to create a theoretical prediction of fractionations in each solution, providing context for understanding experimental result. Each experiment is reversible, so that isotopic exchange equilibrium can be demonstrated.Intellectual Merit:Establishment of iron-isotope geochemistry as a potent, robust tool for understanding modern and ancient environments on the Earth and other bodies requires accurate knowledge of equilibrium isotopic fractionations in iron-bearing solutions. Chloride, among the most ubiquitous dissolved species, is ideally suited for carefully controlled experiments. Use of immiscible liquids will enable rapid equilibration of experimental charges, and relatively easy experimental reversals.Broader Impacts: Proposed research will contribute to the training of a PhD student at UCLA, and support use of MC-ICP-MS analytical facilites in collaboration with Ed Young and spectroscopist Eric Tonui. Development of immiscible-liquid techniques for measuring isotope fractionations in solutions will open up new possibilities for future research in isotopic systems and solution chemistries beyond the scope of the research plan.

铁同位素特征是在低温下产生或反应的天然材料的常见特征。这些特征在低温地球化学和地球生物学中引起了极大的兴趣，因为铁是一种重要的营养物质，其氧化态是现代和古代氧化还原条件的潜在指标。铁同位素地球化学的一个方面，是不是很好地理解的可能性，大分馏发生在不同的物种在溶液中。该建议描述了四组实验和相应的理论计算，以确定平衡铁同位素（56 Fe/54 Fe）分馏含氯溶液。这项研究将有助于建立一个框架，以更好地了解自然界中产生铁同位素特征的自然过程，特别是在区分生物学和结晶的可能影响与溶质成分效应方面。实验将利用FeCl 4络合物在疏水有机溶剂（例如，乙醚），通过测量含水铁和共存的乙醚溶解的FeCl 4-之间的分馏的变化来量化水溶液中56 Fe/54 Fe分配的变化。水的形态建模和溶解的物种的同位素分配函数比的计算将被用来创建在每个解决方案的分馏的理论预测，为理解实验结果提供背景。每个实验都是可逆的，因此同位素交换平衡可以被证明。智力优势：建立铁同位素地球化学作为一个强有力的，强大的工具，了解现代和古代的地球环境和其他机构需要准确的知识平衡同位素分馏含铁的解决方案。氯化物是最普遍存在的溶解物质之一，非常适合仔细控制的实验。使用不混溶的液体将使实验电荷的快速平衡，和相对容易的实验reversals.Broader影响：拟议的研究将有助于在加州大学洛杉矶分校的博士生的培训，并支持使用MC-ICP-MS分析facilites与艾德杨和光谱学家埃里克Tonui合作。开发用于测量溶液中同位素分馏的不溶性液体技术将为研究计划范围以外的同位素系统和溶液化学的未来研究开辟新的可能性。