CAREER: Robust Isotopic Constraints on Primary Productivity from First Principles

职业：第一原理对初级生产力的强大同位素约束

• 批准号: 1945316
• 负责人: Laurence Yeung
• 金额: $ 58.37万
• 依托单位: William Marsh Rice University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-06-01 至 2025-05-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1945316&HistoricalAwards=false
• 关键词: CAREER; Robust; Isotopic; Constraints; Primary

The response of the global biosphere to climate change is uncertain. In particular, biosphere productivity in the present and in the past is difficult to estimate because the available tools are technically challenging to apply in the varied and often poorly understood natural environments in which life can thrive. This study will improve estimates of biosphere productivity in the present and the past through an approach that unifies theory and experiments on the biochemical reactions that drive photosynthesis and respiration. The results will be applied to determine patterns of surface-ocean productivity over the past several decades using a new compilation of existing data that will be made available to the research community. Finally, the project will support a program of annual teacher-training activities aimed at global-change science at the middle- and early-high school level, where curricula and training are currently lacking. Working with the Rice Office of STEM Engagement and the Harris County Department of Education, the investigator will host teachers for summer laboratory experiences and an annual 1-day workshop to train Houston school teachers, develop lessons on global-change science, and cultivate early connections between the geosciences and core science/math disciplines.One of the key tools for assessing past changes in biosphere productivity is stable-isotope analysis. Of this family of approaches, the isotopic composition of molecular oxygen (O2) has been applied widely to constrain the biogeochemical carbon cycle because oxygen is linked to carbon cycling at the metabolic level. Covariations between 18O/16O and 17O/16O ratios, in particular―the “triple-isotope” composition of O2―have been of great utility for determining both modern and past biosphere productivity. Even remnant signals, transferred more than a billion years ago from O2 into rocks, have been used for this purpose. However, the interpretations of such isotopic data are only justified if the biological fractionation processes are well understood. The signals on O2 are quite subtle, and the technical difficulty of triple-isotope measurements has meant that few of the foundational experiments have been repeated and validated. This project will re-evaluate the fundamental O2 fractionation factors for respiration and photosynthesis using new experiments and the tools of computational chemistry. A central hypothesis is that biological oxygen-isotope fractionation can be predicted accurately from first principles to benchmark, improve, and unify oxygen triple-isotope tracers across geoscience fields. The project will also test the sensitivity of biological O2 isotopic fractionation to environmental boundary conditions to evaluate the impacts of environmentally forced isotopic variability on the interpretation of local and global O2 budgets. As a capstone, the oceanographic triple-oxygen field data collected over the past 20 years will be compiled and re-interpreted in light of this new information.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.

全球生物圈对气候变化的反应是不确定的。特别是，目前和过去的生物圈生产力难以估计，因为现有的工具在技术上具有挑战性，难以应用于各种各样的、往往知之甚少的自然环境，而生命可以在这些环境中繁衍生息。这项研究将通过一种方法来改进对现在和过去生物圈生产力的估计，该方法将理论与驱动光合作用和呼吸作用的生物化学反应的实验相结合。研究结果将用于确定过去几十年的表层海洋生产力模式，并使用将提供给研究界的现有数据的新汇编。最后，该项目将支持一项针对初中和高中早期全球变化科学的年度教师培训活动方案，这方面目前缺乏课程和培训。该研究员将与赖斯STEM参与办公室和哈里斯县教育部合作，主持教师暑期实验室体验和为期一天的年度研讨会，以培训休斯顿学校教师，开发全球变化科学课程，并培养地球科学与核心科学/数学学科之间的早期联系。评估生物圈生产力过去变化的关键工具之一是稳定同位素分析。在这一系列方法中，分子氧（O2）的同位素组成已被广泛应用于限制地球化学碳循环，因为氧在代谢水平上与碳循环有关。18 O/16 O和17 O/16 O比值之间的协变，特别是O2的“三重同位素”组成，对于确定现代和过去的生物圈生产力具有很大的实用性。即使是10亿多年前从O2转移到岩石中的残留信号也被用于此目的。然而，只有当生物分馏过程得到很好的理解，这样的同位素数据的解释是合理的。O2上的信号非常微妙，三同位素测量的技术难度意味着很少有基础实验被重复和验证。该项目将使用新的实验和计算化学工具重新评估呼吸和光合作用的基本O2分馏因素。一个中心假设是，生物氧同位素分馏可以准确地预测从第一原理基准，改进和统一的氧三同位素示踪剂在地球科学领域。该项目还将测试生物O2同位素分馏对环境边界条件的敏感性，以评估环境强迫的同位素变异对解释当地和全球O2预算的影响。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。