EAR-PF: Controls of and connections between silicate weathering and organic carbon cycling in watersheds: A test case in the Upper Deschutes Basin, Oregon, USA

EAR-PF：流域硅酸盐风化与有机碳循环之间的控制和联系：美国俄勒冈州上德舒特盆地的测试案例

• 批准号: 2053056
• 负责人: Evan Ramos
• 金额: $ 17.4万
• 依托单位: Ramos, Evan J
• 依托单位国家: 美国
• 项目类别: Fellowship Award
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-09-01 至 2023-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2053056&HistoricalAwards=false
• 关键词: EAR; PF; Controls; connections; between

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2). Dr. Evan J. Ramos has been awarded an NSF EAR Postdoctoral Fellowship to conduct research, professional development, and outreach activities at Rice University and Brown University under the mentorship of Professors Mark A. Torres and Daniel E. Ibarra, respectively. This project investigates the nature of silicate weathering, organic carbon (OC) cycling, and their potential couplings across a watershed in the Cascade Mountains of Oregon, USA. Silicate weathering and OC cycling in soils influence the transfer of CO2 between the solid Earth and Earth’s ocean and atmosphere, thereby forcing and responding to changes in climate over a range of timescales. These processes are known to influence one another, but without tools to quantitatively probe both simultaneously, our ability to understand how either silicate weathering or OC cycling have responded to past climate change or how they will respond in the future is critically limited. The goal of this project is to develop a multiproxy geochemical approach that allows for the dual analyses of silicate weathering and OC cycling over timescales spanning millennia to millions of years. Motivated by a significant inverse correlation found between published soil lithium (Li) isotope compositions (a measure of silicate weathering intensity) and soil OC concentrations in a soil age sequence in Hawaii, Dr. Ramos will test the applicability of these combined measurements by (1) measuring Li isotope compositions and OC concentrations in soil and river sediments across a watershed with environmental and geologic conditions that differ from Hawaii and (2) developing models that simulate silicate weathering and OC cycling in soils. Research and professional development will involve the training of one undergraduate at Rice and one at Brown in sample acquisition, geochemical analysis of soils, model development, and written and verbal scientific communication. Project findings will be incorporated into a virtual field experience on ecosystems and watersheds, and lesson plans related to this virtual field experience will be developed with Houston-area science educators for usage in middle and high school science classes.Silicate weathering and organic carbon (OC) cycling in soils respond to and affect climate on a range of timescales, from millennia to millions of years. While typically studied independently of one another, both silicate weathering and OC cycling are intimately tied via the budgets of nutrients, acids, and reactive surfaces in soils. The result is a complex set of positive and negative feedbacks that make it difficult to predict how either weathering or OC cycling will respond to environmental change. Moreover, the relationship(s) between weathering and OC cycling need not be the same across a landscape and may instead be modified by the physical processes operating on distinct landscape elements (e.g., mountain hillslopes, floodplains). Dr. Ramos will test the hypothesis that, over millennial timescales, silicate weathering and OC storage are positively coupled through a mutual dependence on the rate of phyllosilicate (clay) mineral formation and that, as a result, landscape elements where clay mineral formation is favored (e.g., floodplains) strongly impact the net amount of CO2 drawdown. This project will involve sampling of river sediments, soils, and bedrock and subsequent measurements of Li isotope ratios, OC contents, and radiocarbon (14C) contents across an upland to floodplain transition to further our understanding of the coupled inorganic and organic C cycles. The Upper Deschutes Basin in the Oregon Cascades offers a compelling setting to gather critical data that test our hypothesis because of its lithologic (volcanic) uniformity, geologically recent formation (6.8 kya), and its physiographic similarity to other headwater catchments in recently deglaciated terrains. Additionally, results will be used to develop a generic model to address outstanding inconsistencies in modern weathering budgets and the potential magnitude of secular C cycle variation due to changing landscape forms over geologic time.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.

该奖项全部或部分根据2021年美国救援计划法案（公法117-2）资助。Evan J.拉莫斯博士被授予NSF博士后研究金，在Mark A教授的指导下在莱斯大学和布朗大学进行研究，专业发展和推广活动。托雷斯和丹尼尔E.伊瓦拉，分别。该项目研究了美国俄勒冈州喀斯喀特山脉流域的硅酸盐风化、有机碳（OC）循环及其潜在耦合的性质。土壤中的硅酸盐风化和有机碳循环影响着二氧化碳在固体地球与地球海洋和大气之间的转移，从而在一系列时间尺度上推动和应对气候变化。众所周知，这些过程相互影响，但如果没有工具同时定量探测两者，我们了解硅酸盐风化或OC循环如何应对过去气候变化或未来如何应对的能力受到严重限制。该项目的目标是开发一种多指标地球化学方法，允许在数千年至数百万年的时间尺度上对硅酸盐风化和OC循环进行双重分析。受已发表的土壤锂同位素组成之间存在显著负相关性的启发，（硅酸盐风化强度的测量）和土壤有机碳浓度在土壤年龄序列在夏威夷，拉莫斯博士将通过（1）测试这些组合测量的适用性在不同的环境和地质条件下测量流域土壤和河流沉积物中的Li同位素组成和OC浓度，夏威夷和（2）开发模拟土壤中硅酸盐风化和有机碳循环的模型。研究和专业发展将涉及一个本科生在水稻和一个在布朗在样品采集，土壤地球化学分析，模型开发，以及书面和口头科学交流的培训。项目的研究结果将被纳入一个虚拟的生态系统和流域的实地经验，与此相关的虚拟实地经验的课程计划将开发与休斯顿地区的科学教育工作者在初中和高中的科学课使用。硅酸盐风化和有机碳（OC）在土壤中的循环响应和影响气候的时间范围，从几千年到数百万年。虽然通常研究彼此独立，硅酸盐风化和OC循环是密切联系在一起的营养物质，酸，和土壤中的反应表面的预算。结果是一组复杂的正反馈和负反馈，使得难以预测风化或OC循环将如何响应环境变化。此外，风化和有机碳循环之间的关系在整个景观中不需要是相同的，而是可以通过作用于不同景观元素的物理过程（例如，山坡、洪泛平原）。拉莫斯博士将测试这一假设，即在千年的时间尺度上，硅酸盐风化和OC储存通过对层状硅酸盐（粘土）矿物形成速率的相互依赖而正耦合，因此，有利于粘土矿物形成的景观元素（例如，洪泛区）强烈影响CO2下降的净量。该项目将涉及河流沉积物，土壤和基岩的采样和随后的测量锂同位素比，OC含量，放射性碳（14 C）含量在整个高地河漫滩过渡，以进一步了解耦合的无机和有机碳循环。上德舒特盆地在俄勒冈州瀑布提供了一个令人信服的设置，收集关键的数据，测试我们的假设，因为它的岩性（火山）的均匀性，地质最近形成（6.8千亚），其地形相似的其他源头流域在最近冰川消退的地形。此外，研究结果将用于开发一个通用模型，以解决现代风化预算中突出的不一致性和长期C周期变化的潜在幅度，由于地质时期景观形式的变化。该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。