Collaborative Research: Determining the role of uranium(V) in the global uranium cycle by characterizing burial mechanisms in marine sinks

这项研究将研究铀(U)在海底（铀最重要的储库）缺氧条件下的循环。提高我们对铀地球化学的理解对于地质应用至关重要，如确定岩石年龄、古环境重建、水质和确保新的关键矿物来源。重建古代海洋的含氧量有助于将环境的进化与地球上以及潜在的系外行星上的生命进化联系起来。随着时间的推移，探测海洋中氧含量的工具（如U和其他对氧含量敏感的元素）仍然具有挑战性，因为它们在低氧海洋环境中的表现尚不清楚。为了解决这一知识缺口，该项目将追踪一种新的U物种U（+V）的存在，并研究其在现代和古代海洋U循环中的作用。这些结果将为重建地球海洋和大气中的氧气以及更广泛的全球U循环提供重要的见解。海洋环境中铀的寄主相和形态在很大程度上仍然未知，这阻碍了我们重建沉积条件的能力。该项目将研究最重要的海洋汇中的铀埋藏，以表征铀的形态、去除途径和全岩铀地球化学（包括其同位素组成）之间的关系。这一目标将通过以下方式实现：(1)与海洋环境相关的U相实验；(2)富有机质页岩和沉积物中U形态与U地球化学的关系；(3)建立基于背景信息的铀地球化学预测解释模型。除了研究生培训外，该项目还将促进地球和环境科学专业学生的博物馆收藏和科学交流，并在宾夕法尼亚州和密歇根州农村地区推广K-12环境地球科学。该奖项反映了美国国家科学基金会的法定使命，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。

This study will investigate uranium (U) cycling in oxygen-depleted conditions on the ocean floor, the most important sink of U. Improving our understanding of U geochemistry is critical for geological applications as diverse as dating the age of rocks, paleoenvironmental reconstruction, water quality, and securing new critical mineral sources. Reconstructing the oxygen levels of ancient oceans helps to link the evolution of the environment with evolution of life on Earth and potentially on exoplanets. Interpreting tools to probe oxygen levels in the oceans through time, such as U and other elements sensitive to oxygen level, remain challenging because of the unknowns about how they behave in low-oxygen marine settings. To address this knowledge gap, this project will track the presence of a new U species, U(+V), and investigate its role in the U cycle in modern and ancient oceans. These results will provide important insights for reconstructions of oxygen of Earth’s oceans and atmosphere, as well as the global U cycle more broadly. The host phases and speciation of U in marine settings remain largely unknown, hampering our ability to reconstruct depositional conditions. This project will investigate U burial in the most significant marine sink to characterize the relationship between U speciation, removal pathways, and whole-rock U geochemistry, including its isotope composition. This goal will be accomplished with: (1) experiments of U phases relevant to marine settings; (2) characterizing the relationship between U speciation and U geochemistry in organic-rich shales and sediments; and (3) developing an interpretive model to predict U geochemistry from contextual information. In addition to graduate training, this project will promote museum collections and science communication for Earth and environmental science majors and K-12 outreach in environmental geosciences in rural Pennsylvania and Michigan.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.