Experimental calibration of stable isotope and REE partitioning in bioapatite

技术描述：生物磷灰石的地球化学研究广泛应用于古气候学、古生态学、古海洋学、人类学/考古学、化石法医学、地质年代学、龋齿学等领域。由于对结构碳酸盐（CO3）中氧和碳的稳定同位素的分馏以及生物磷灰石和水溶液之间稀土元素的分配缺乏了解，许多此类努力受到了损害。稳定同位素分馏和REE分配系数将通过在同位素和化学表征的溶液中合成生物磷灰石，在10至60℃的温度范围内测量。重点将放在确定CO3取代的晶体位置作为同位素分馏的控制，校准牙齿化学的光谱测量，以及表征粒度和表面积以区分REE的晶内分配系数和吸附分配系数。将进行时间序列实验，以确保接近平衡，并将复制过去的实验方法，以改进粒度表征并与新的化学和同位素数据进行比较。非技术/更广泛的影响：该赠款资助对生物磷灰石（构成骨骼和牙齿的矿物）的地球化学行为进行全面校准。这项工作对于验证过去的研究和改进许多领域的定量解释非常重要，这些领域包括古气候和古海洋学、人类学、化石的法医鉴定、地质年代学和可能的牙齿稳定性。具体而言，我们将校准测定生物磷灰石中碳酸盐（CO3）含量的方法，碳酸盐（CO3）含量对牙釉质的溶解度有很强的控制作用，并合成不同CO3含量的生物磷灰石。将对生物磷灰石积累镧系元素和重氧、重碳同位素的趋势进行校准，并与先前稀疏的测量结果进行比较。这些数据将为过去对现代牙齿和化石地球化学的解释提供信息，并改善涉及现代和化石牙齿的未来研究的目标。教育拓展包括对研究生的研究培训，以及对代表性不足群体的本科研究的发展。其他培训包括培养一名年轻女性研究科学家的指导技能。博伊西州立大学有很大比例的返校学生和兼职学生，本科平均年龄为27岁。因此，研究和教育活动影响的人口与大多数其他大学不同。

Technical description:The geochemistry of biogenic calcium phosphate (bioapatite) is widely used in studies of paleoclimatology, paleoecology, paleoceanography, anthropology/archeology, fossil forensics, geochronology, and tooth caries. Many such endeavors are compromised by poor understanding of the fractionation of stable isotopes of oxygen and carbon in structural carbonate (CO3), and partitioning of rare-earth elements (REE) between bioapatite and aqueous solutions. Stable isotope fractionations and REE partition coefficients will be measured by synthesizing bioapatite in isotopically- and chemically- characterized solutions at temperatures ranging from 10 to 60 °C. Particular emphasis will be placed on identifying the crystallographic site of CO3 substitution as a control on isotope fractionations, calibrating spectroscopic measurements of tooth chemistry, and characterizing particle sizes and surface areas to distinguish intracrystalline vs. adsorption partition coefficients for REE. Time-series experiments will be conducted to ensure close approach to equilibrium, and past experimental methods will be reproduced for improved particle size characterization and comparison to new chemical and isotopic data. Non-technical/Broader impacts:This grant funds a comprehensive calibration of the geochemical behavior of bioapatite - the mineral that constitutes bones and teeth. This work is important for validating past research and improving quantitative interpretations in numerous fields ranging from paleoclimate and paleoceanography to anthropology, forensic discrimination of fossils, geochronology and possibly dental stability. Specifically, we will calibrate methods to determine the carbonate (CO3) content of bioapatite, which strongly controls tooth enamel solubility, and synthesize bioapatites with different CO3 contents. The tendency for bioapatite to accumulate lanthanide-group elements and the heavy isotopes of oxygen and carbon will be calibrated and compared with sparse previous measurements. These data will inform past interpretations of modern tooth and fossil geochemistry and improve targeting of future studies involving modern and fossil teeth. Educational outreach includes research training for a graduate student, and development of undergraduate research for underrepresented groups. Additional training includes development of mentorship skills for a young female research scientist. Boise State serves a large proportion of returning and part-time students with an average undergraduate age of 27. Thus, research and education activities impact a different demographic than at most other universities.