Collaborative Research: EAR-Climate: Physical Controls on CO2 Release from Shale Weathering

合作研究：EAR-气候：页岩风化中二氧化碳释放的物理控制

• 批准号: 2141520
• 负责人: Mark Torres
• 金额: $ 25.82万
• 依托单位: William Marsh Rice University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-07-01 至 2025-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2141520&HistoricalAwards=false
• 关键词: Collaborative; Research; EAR; Climate; Physical

Shales, commonly found sedimentary rocks, contain a large amount of organic carbon and have been mined for oil, natural gas, and other fossil fuels. Analogous to how the burning of fossil fuels releases carbon dioxide (CO2) to the atmosphere, the natural weathering of shale also releases CO2. While this CO2 release occurs slowly, it has potential to change Earth’s climate over million-year timescales. The scientific community currently lacks understanding about how shale weathering (and associated CO2 release) occurs, and this limits understanding of both past changes in Earth’s climate and predictions of future changes. This project examines how changes in climate and erosion influence the rate of shale weathering via performing a detailed field study in shale rock exposed throughout California. Field work results will be incorporated into a mathematical model that will allow estimates of the rate of CO2 release from shale weathering across the globe. This project will thus both advance understanding of an important natural control on Earth’s climate, and provide a framework to improve predictions of climate change in the future. In addition to these benefits, the project will also provide training for graduate and undergraduate students and project members will engage in K-8 and community outreach to provide geoscience education. Despite previous work on the chemical and biological processes that drive shale weathering, there does not exist a mechanistic understanding of how physical processes modulate CO2 release from shale weathering. This project addresses this knowledge gap by quantifying how variations in physical erosion rate, precipitation rate, and local topography influence shale weathering. The project tests the hypothesis that feedbacks between the supply of carbon during conversion of rock to regolith, chemical kinetics, and topographic controls on weathering zone thickness cause CO2 release from shale weathering to be maximized for areas with modest erosion rates, modest precipitation rates, and high topographic curvature (i.e., ridges). To accomplish this, the researchers will measure the loss of organic carbon in depth-profiles of shale up to 10 m deep, focusing on shales of the Monterey, Rincon, and Cozy Dell formations in the Santa Ynez Mountains, California, where a 6-fold erosion gradient allows assessment of how variation in erosion influences shale weathering. The Santa Ynez Mountain samples will be supplemented with depth profiles of Monterey Shale from Point Reyes National Seashore and Carrizo Plain, California, allowing exploration of shale weathering over a 5-fold gradient in precipitation within the same lithologic formation. The field data will be used to calibrate and modify a reactive-transport model based on physical forcing, thereby providing new opportunities to link geomorphic transport laws with biogeochemical models, and predict CO2 release from shale weathering across a wide range of spatial and temporal scales. Documenting links between physical processes and silicate weathering has led to major advances in the understanding of feedbacks between climate, tectonics, and topography, and documenting such tradeoffs for shale weathering in this project is a logical, yet critical next step to advance understanding of the geologic carbon cycle.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.

页岩是常见的沉积岩，含有大量有机碳，并已被开采用于油，天然气和其他化石燃料。类似于化石燃料的燃烧如何将二氧化碳（CO2）释放到大气中，页岩的自然风化也释放出CO2。尽管此二氧化碳的发布缓慢，但它有可能在数百万年的时间范围内改变地球气候。该科学界目前缺乏对页岩风化（以及相关的二氧化碳释放）的了解，这限制了对过去的地球气候变化的理解和对未来变化的预测。该项目研究了气候和侵蚀的变化如何通过在整个加利福尼亚州暴露的页岩岩石上进行详细的现场研究来影响页岩风化的速度。现场工作结果将纳入数学模型中，该模型将允许估计全球页岩面风雨的二氧化碳释放速率。因此，该项目将既可以提高对地球气候的重要自然控制的理解，又将提供一个框架，以改善未来气候变化的预测。除这些好处外，该项目还将为研究生和本科生和项目成员提供培训，并将从事K-8和社区外展活动，以提供地球科学教育。尽管以前在驱动页岩风化的化学和生物学过程上进行了研究，但对物理过程如何调节二氧化碳从页岩风化中释放的机械理解并不存在。该项目通过量化物理侵蚀率，降水率和局部地形的变化来解决该知识差距。该项目检验了以下假设：在岩石转化为岩石中的碳供应之间的反馈，化学动力学和对风化区域厚度的地形控件导致二氧化碳风化释放，从页岩风化中释放，对于适度的侵蚀率，适度的降水速率和高地形曲线（即，脊，脊，山脊）。为此，研究人员将在加利福尼亚州圣伊尼兹山脉的蒙特雷，林肯和舒适的戴尔地层的页岩中衡量页岩中有机碳的损失，重点是蒙特利，林肯和舒适的戴尔地层，其中6倍的侵蚀梯度可以评估含含力的变异影响含含力的变异。 Santa Ynez山样品将在雷耶斯特国家海岸和加利福尼亚州的Carrizo Plain的蒙特利页岩中补充深度，从而探索了在相同岩性形成中降水的5倍梯度的页岩风化。该现场数据将用于基于物理强迫校准和修改反应性传输模型，从而提供了新的机会，将地貌传输定律与生物地球化学模型联系起来，并预测从跨空间和临时尺度的页岩式风化中释放CO2。记录物理过程与硅胶风化之间的联系已导致在理解气候，构造和地形之间的反馈方面的重大进展，并且在该项目中为页岩风化而进行的这种权衡是逻辑上但至关重要的下一步，是提高对地质碳周期的理解，这反映了NSF的稳定范围。 标准。