Collaborative Research: Experimental determination of trace element diffusion rates in tooth enamel

该项目将研究牙釉质对微量元素如钡、锶、铅和稀土元素(从镧到钚的精选元素)的吸收速度。由于测量的空间尺度很小，本项目需要一项关键的分析技术--二次离子质谱仪(SIMS)。这项研究对于了解人体如何摄取微量元素以及它们在从几年到数百万年的时间尺度上区分个体的保真度非常重要。这项工作将对古生物学、考古学、毒理学和法医学产生影响，包括化石盗窃诉讼。这笔资金将支持一名博士生的研究和培训。这项研究将被用来利用博伊西地区非科学家的教育机会，并将不知道所有微化学研究领域如何从SIMS中受益的研究人员联系起来，SIMS是一种最常应用于半导体的工具。该项目的中心焦点是批判性地评估多种微量元素在天然牙釉质中的扩散速度。这项研究旨在回答三个主要问题：牙釉质中微量元素的扩散系数(D‘s)如何取决于1)电荷与离子半径和分配的关系；2)牙釉质取向和牙釉质类型；3)石化状态？为了解决这些问题，将在一系列离子和离子半径的温度范围(4°C、20°C和37°C)内进行吸收实验。将在不同的方向上测量哺乳动物的两种主要牙釉质类型--放射状和交叉状牙釉质的D‘s。在化石釉质中的测量将与我们在现代釉质中进行的类似测量进行比较。数据将使用标准扩散方程进行反演，自然数据集将被评估其与扩散限制吸收的一致性(或不一致性)。结果将广泛地限制稀土、铀和碱性元素的分配系数，这将改进这些地球化学和毒理上重要元素的扩散速度和吸收模型。所有数据都将在可查阅的国际期刊上迅速发表，并/或在网上地球化学数据库中存档。一名博士生将参加SIMS研讨会，帮助发展SIMS用户社区，并通过既定的外联计划向小学生和公众展示她在化石和化石方面的工作。

This project will investigate the rate of uptake of trace elements like barium, strontium, lead and the rare-earth elements (selected elements from lanthanum to lutetium) into tooth enamel. This project requires a key analytical technique "Secondary Ion Mass Spectrometry (SIMS)" because the spatial scale of measurement is so small. This research is important for understanding how trace elements are taken up in the human body and their fidelity in distinguishing individuals on timescales ranging from years to millions of years. The work will have implications for paleontology, archeology, toxicology and forensics, including the litigation of fossil theft. This funding will support the research and training of a PhD student. This research will be used to leverage educational opportunities for non-scientists in the Boise region and connect researchers unaware of how all areas of microchemical research can benefit from SIMS, a tool that is most commonly applied to semiconductors.The central focus of this project is to critically evaluate rates of diffusion of numerous trace elements in natural dental enamel. The research has been formulated to answer three main questions: How do diffusivities (D's) of trace elements in enamel depend on 1) charge vs. ionic radius and partitioning? 2) enamel orientation and enamel type? 3) fossilization state? To address these questions, uptake experiments will be conducted over a range of temperatures (4°, 20° and 37 °C) for a range of ions and ionic radii. D's will be measured in different directions for the two main enamel types in mammals - radial and decussate. Measurements in fossil enamel will be compared with similar measurements we make in modern enamel. The data will be inverted using standard diffusion equations, and natural datasets will be evaluated for their consistency (or not) with diffusion-limited uptake. The results will broadly constrain REE, uranium and alkaline element partition coefficients, which will improve models of diffusion rate and uptake of these geochemically- and toxicologically important elements. All data will be published rapidly in accessible international journals and/or archived in on-line geochemical databases. A PhD student will participate in a SIMS workshop, helping develop a community of SIMS users and present her work on fossils and fossilization to elementary school children and the public through established outreach programs.