Testing Hypotheses of Near-Equilibrium Kinetics For Silicate Minerals with an Innovative Silicon Isotope Tracer Method

用创新的硅同位素示踪方法测试硅酸盐矿物的近平衡动力学假设

• 批准号: 1926734
• 负责人: Chen Zhu
• 金额: $ 41.06万
• 依托单位: Indiana University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-07-01 至 2023-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1926734&HistoricalAwards=false
• 关键词: Testing; Hypotheses; Near; Equilibrium; Kinetics

The assessment of the safety of storing nuclear wastes and carbon dioxide in geological repositories requires projections into a distant future. For example, would the interactions between these wastes and surrounding minerals and rocks cause the release of harmful materials into the environment in 10,000 years or 100,000 years? Reliable predictions over such a time span require a greater understanding of the fundamentals regarding the rates or speed of chemical reactions during these interactions. But these subjects have been a challenge to study. For example, 90% of Earth's crust is made of silicate minerals, for which silicon (Si) and oxygen are the main chemical elements, and their reactions are slow and difficult to detect. The proposed research uses an innovative experimental method, the isotope tracer method, to measure reaction rates in the laboratory under conditions not possible before. These new rates will be eventually incorporated into safety assessment models for society's general environmental projects. In addition to scientific innovations, this project also aims at human resources development. The underlying fundamental sciences are thermodynamics and kinetics, which are difficult learning subjects for students. Despite its significance, courses in thermodynamics and kinetics are disappearing from the geology curriculum and most experts on thermodynamics are either retired or near retirement age. To train the next generation of experts, this project will develop a webinar series on thermodynamics and kinetics and work with Indiana University's Center for Innovative Teaching and Learning for broadcasting and recording. Finally, the grant will leverage Indiana University's Minority-Serving Institution STEM initiative and the Center of Excellence for Women in Technology to recruit underrepresented faculty and potential doctoral students to summer research at Indiana University. The proposed research will focus on geochemical kinetics at near-equilibrium conditions and test various hypotheses using unidirectional dissolution rate data obtained from the isotope tracer experimental method. The key hypothesis is that the scatter and conflicts of near-equilibrium data are caused by unaccounted-for secondary phase precipitation. Eliminating or accounting for this possibility is a critical first step toward testing other hypotheses of near-equilibrium reaction mechanisms and interfacial processes. In the proposed experiments, a rare Si isotope (29Si or 30Si) is added to the experimental solutions, which reacts with natural silicates having mostly 28Si. The reaction rates are tracked by 29Si/28Si ratios of reacted solutions using High-Resolution Multi-Collector ICP-MS technology. In contrast, the conventional experimental method measures rates based on Si concentrations. Because isotope ratios are used instead of concentrations to calculate rates, the precipitation of Si-containing secondary phases, which consumes Si concentrations while having a negligible effect on Si isotope ratios, does not interfere with dissolution rate determination. The huge isotope disequilibrium introduced by overwhelming the system with 29Si makes Si isotope fractionation during dissolution and precipitation (2-4?) unimportant for rate determination. Currently, extrapolation from far-from-equilibrium to near-equilibrium conditions is necessary to translate laboratory experimental data to models of geological and environmental processes. But little confidence can be placed on these extrapolations because of the lack of near-equilibrium data and unsupported assumptions. The project will fill this significant knowledge gap. The isotope tracer method is general and novel and can be expanded to using Barium, Calcium, and Magnesium isotopes to study sulfate, carbonate, and other minerals, and applied to the fields of chemistry, chemical engineering, and materials science.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

在地质存储库中储存核废料和二氧化碳的安全性的评估需要预测到遥远的未来。例如，这些废物与周围矿物质和岩石之间的相互作用会在10，000年或100，000年内释放到环境中吗？在这种时间范围内的可靠预测需要对这些相互作用期间化学反应的速率或速度有更深入的了解。但是这些主题是研究的挑战。例如，地球的90％是由硅酸盐矿物制成的，硅（Si）和氧气是主要的化学元素，它们的反应缓慢且难以检测。拟议的研究使用创新的实验方法，即同位素示踪方法，以在不可能的条件下测量实验室的反应速率。这些新价格最终将纳入社会一般环境项目的安全评估模型中。除了科学创新外，该项目还旨在人力资源开发。基本的基本科学是热力学和动力学，这是学生的艰难学习学科。尽管具有重要意义，但热力学和动力学方面的课程仍从地质课程中消失，大多数热力学专家都退休或接近退休年龄。为了培训下一代专家，该项目将开发有关热力学和动力学的网络研讨会系列，并与印第安纳大学的创新教学中心合作，用于广播和录制。最后，该赠款将利用印第安纳大学的少数派服务机构STEM倡议和技术卓越的技术中心，以招募代表性不足的教职员工和潜在的博士生来到印第安纳大学的夏季研究。拟议的研究将在近平衡条件下关注地球化学动力学，并使用从同位素示踪实验方法获得的单向溶解速率数据测试各种假设。关键的假设是，近平衡数据的散射和冲突是由未计算的次级降水引起的。消除或考虑这种可能性是测试其他近平衡反应机制和界面过程的其他假设的关键第一步。在拟议的实验中，将稀有的Si同位素（29SI或30SI）添加到实验溶液中，该实验溶液与自然硅酸盐的反应大多为28Si。使用高分辨率的多核心ICP-MS技术，通过29SI/28SI的比率跟踪反应速率。相反，常规的实验方法根据SI浓度测量速率。由于使用同位素比而不是浓度来计算速率，因此含Si的次级阶段的降水（在对Si同位素比率上具有可忽略的影响）不会干扰溶解速率确定。引入的巨大同位素是通过将系统压倒29SI引入的，这使得在溶解和降水期间（2-4？）在速率确定时不重要。目前，必须将实验室实验数据转换为地质和环境过程模型，从远面平衡到近平衡条件是必要的。但是，由于缺乏近平衡的数据和不支持的假设，对这些外推的信心很少。该项目将填补这一重要的知识差距。同位素示踪剂方法是一般和新颖的，可以扩展到使用钡，钙和镁同位素研究硫酸盐，碳酸盐和其他矿物质，并应用于化学，化学工程和材料科学领域。该奖项反映了NSF的法定任务，并通过评估了范围的范围，以评估其知识范围和宽广的基础。

项目成果

A library of BASIC scripts of reaction rates for geochemical modeling using phreeqc

• DOI: 10.1016/j.cageo.2019.104316
• 发表时间: 2019-12
• 期刊: Comput. Geosci.
• 作者: Yilun Zhang;Bin Hu;Yanguo Teng;K. Tu;Chen Zhu

Decoupling feldspar dissolution and precipitation rates at near-equilibrium with Si isotope tracers: Implications for modeling silicate weathering

用硅同位素示踪剂解耦近平衡状态下的长石溶解和沉淀速率：对模拟硅酸盐风化的影响

• DOI: 10.1016/j.gca.2019.12.024
• 发表时间: 2020
• 期刊: Geochimica et Cosmochimica Acta
• 影响因子: 5
• 作者: Zhu, Chen;Donald Rimstidt, J.;Zhang, Yilun;Kang, Jinting;Schott, Jacques;Yuan, Honglin
• 通讯作者: Yuan, Honglin

Comparison of thermodynamic data files for PHREEQC

• DOI: 10.1016/j.earscirev.2021.103888
• 发表时间: 2021-12
• 期刊: Earth-Science Reviews
• 影响因子: 12.1
• 作者: Peng Lu;Guanru Zhang;J. Apps;Chengmo Zhu

A method for Si isotope tracer kinetics experiments: Using Q-ICP-MS to obtain 29Si/28Si ratios in aqueous solutions

Si同位素示踪动力学实验方法：使用Q-ICP-MS获得水溶液中的29Si/28Si比率

• DOI: 10.1016/j.chemgeo.2019.119337
• 发表时间: 2020
• 期刊: Chemical Geology
• 影响因子: 3.9
• 作者: Zhang, Yilun;Gong, Lei;Chen, Kaiyun;Burkhart, Joseph;Yuan, Honglin;Zhu, Chen
• 通讯作者: Zhu, Chen

Dawsonite as a Temporary but Effective Sink for Geological Carbon Storage

• DOI: 10.1016/j.ijggc.2022.103733
• 发表时间: 2022-09
• 期刊: International Journal of Greenhouse Gas Control
• 影响因子: 3.9
• 作者: Peng Lu;Guanru Zhang;Yi Huang;J. Apps;Chengmo Zhu