Determining Mechanisms and Rates of Geologic Respiration at Watershed Scales

岩石中储存着大量分散的有机碳，是所有生物体中碳储存量的30，000倍。在岩石分解和土壤形成的过程中，储存在岩石中的有机碳以二氧化碳的形式释放到大气中。 了解碳释放的控制对于了解地球气候的历史非常重要，对于评估人类的影响如何影响这个巨大的碳库也至关重要。这个拟议的研究项目专门研究了山体建设和侵蚀如何控制岩石中有机碳的释放。 该项目将为研究生和本科生提供研究经验和培训，包括有机和微量金属地球化学方面的高度专业化技术。美国和国际科学界将建立一个新的伙伴关系，研究地球上岩石、土壤、水、空气和生物体相互作用的“关键地带”。PI将与两个当地项目合作，通过夏令营项目的课程开发，在初中和高中阶段吸引代表性不足的群体。这些教育和外联工作将支持和深化现有的关系，以促进代表性不足的群体更多地参与STEM领域。 最终，这项研究将有助于更准确地模拟全球碳和氧循环，提高对地球如何在地质时间尺度上保持可居住性的理解，并更好地约束对大气二氧化碳未来变化的预测。岩石中有机碳的矿化，这一过程被称为地质呼吸，是大气中二氧化碳的主要来源，因此在地质时间尺度上是地球气候的主要控制因素。这个研究项目的目标是解决目前围绕侵蚀和地质呼吸之间的关系的矛盾。地质呼吸和物理侵蚀速率之间的关系将通过研究具有对比构造隆起、侵蚀和产沙量的流域来表征。溶解的铼（Re）将作为地质呼吸的示踪剂进行测试。目前的理解是，CO2在基岩风化过程中释放，并以与CO2释放相当的速率保守地输送到地表水。溶解河流Re作为定量示踪剂的效用将进行评估，河流颗粒Re的地质呼吸率的准确估计的重要性也将得到验证。拟议的研究包括多尺度分析的地质呼吸从风化剖面规模通过流域规模在约束良好的小山区河流流域沿着美国西海岸。 实验室分析将包括风化剖面的土壤和岩石样本以及在各种水流条件下收集的河流样本的溶解和颗粒部分。 Re，14C，有机碳的生物标志物分析和其他地球化学示踪剂的测量将结合和分析，以表征来源，流动路径和过程，提供Re和岩石衍生的有机碳从高地景观到河流。 在对目标流域的地质呼吸速率进行量化和评估的同时，这项研究还将发展对全球范围内进行此类确定的理解。

A vast pool of diffuse organic carbon is stored in rocks, constituting 30,000 times the amount of carbon stored in all organisms. During the breakdown of rocks and formation of soil, organic carbon stored in rocks is released as carbon dioxide into the atmosphere. Understanding the controls on this release of carbon is important for understanding the history of Earth's climate, and is also essential for evaluating how human impacts may be affecting this large reservoir of carbon. This proposed research project specifically investigates how mountain building and erosion control the release of organic carbon from rocks. The project will provide research experience and training for graduate and undergraduate students, including highly specialized techniques in organic and trace metal geochemistry. A new partnership will be developed between the US and international scientific communities studying the Earth's "critical zone" where rock, soil, water, air, and living organisms interact. The PIs will partner with two local programs to engage underrepresented groups at the middle and high school level through curriculum development for summer camp programs. These educational and outreach efforts will support and deepen existing relationships to promote increased participation of underrepresented groups in STEM fields. Ultimately this research will contribute to more accurate modeling of the global carbon and oxygen cycles, improving understanding of how the Earth has maintained habitability over geologic timescales and better constrain predictions of future change in atmospheric carbon dioxide.Mineralization of organic carbon in rocks, a process known as geologic respiration, is a major CO2 source to the atmosphere and thus a major control on Earth's climate over geologic timescales. The goal of this research project is to resolve a current paradox surrounding the relationship between erosion and geologic respiration. The relationship between geologic respiration and physical erosion rates will be characterized by studying watersheds with contrasting tectonic uplift, erosion, and sediment yields. Dissolved rhenium (Re) will be tested as a tracer of geologic respiration. Current understanding is that rhenium is released during bedrock weathering and conservatively delivered to surface water at a rate comparable to that of CO2 release. The utility of dissolved riverine Re as a quantitative tracer will be evaluated, and the importance of riverine particulate Re for accurate estimation of geologic respiration rates will also be verified. The proposed research includes a multi-scale analysis of geologic respiration from the weathering profile scale up through the watershed scale in well-constrained small mountainous river basins along the West Coast of the US. Laboratory analyses will include both soil and rock samples from weathering profiles and dissolved and particulate fractions of river samples collected across a wide range of flow conditions. Measurements of Re, 14C, biomarker analyses of organic carbon, and other geochemical tracers will be combined and analyzed in order to characterize the sources, flowpaths, and processes that deliver Re and rock-derived organic carbon from upland landscapes to rivers. While quantifying the rates and evaluating the key controls on geologic respiration in the target river basins, this research will also develop the understanding to make such determinations worldwide.