Collaborative Research: Concentration - Ratio - Discharge (C-R-Q) relationships of transient water-age distributions

合作研究：瞬时水龄分布的浓度-比率-流量（C-R-Q）关系

• 批准号: 2134453
• 负责人: Jon Chorover
• 金额: $ 46.65万
• 依托单位: University of Arizona
• 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: 2022-01-15 至 2024-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2134453&HistoricalAwards=false
• 关键词: Collaborative; Research; Concentration; Ratio; Discharge

The weathering of silicate rock in the hillslopes that feed headwater streams sets the chemical characteristics of water draining catchments, the transport of mass from continents to oceans and critical feedbacks between atmospheric CO2 and the land surface. Yet quantitative models for the basic relationship between the rate of water discharge from a landscape (Q) and the concentration of solutes (C) within that water remains a significant challenge. This is in part due to close coupling between the solubilization of bedrock and the formation of new secondary minerals, which we term silicate weathering. At the core of this uncertainty is a practical issue: the rates of silicate weathering are slow. This means that typical flow-through columns built in laboratories cannot capture even a simplified representation of silicate weathering in upland watersheds. In contrast, natural hillslopes are complicated and difficult to constrain. In this work, investigators will overcome this disparity using the unique mesoscale Landscape Evolution Observatory (LEO), which affords three replicate convergent hillslopes constructed on the world's largest weighing lysimeters. The LEO facility is housed within the Biosphere 2 center, which translates Earth system science research into tractable examples and demonstrations for over 100,000 public visitors per year. This includes 10,000 students who use the Biosphere 2 as part of their STEM curriculum. The project will train two PhD students, thus forming a collaborative research group across three institutions, and produce 'on-display' projects as part of the Biosphere 2 educational tour including information about the purpose and status of the work. Finally, the reactive transport simulations developed and calibrated by this project will be leveraged as an example for a current NSF Research Coordination Network: Community-based educational infrastructure for numerical simulation in the Earth Sciences. Even in a perfectly homogeneous system, an infinite combination of these tandem dissolution and precipitation rates could lead to the same solute concentration. Further, these reactions occur through non-uniform flow paths subject to unsteady infiltration. Thus, a critical need to advance process-based understanding of the C-Q relationship is the provision of additional constraints which embed within the same model framework and reduce the number of free parameters. Here, the researchers will use the characteristic shifts in stable isotope and trace element ratios to diagnose the relationship between primary silicate weathering and secondary mineral precipitation. Specifically, they will pair silicon isotopes (delta 30Si) and germanium-silicon ratios (Ge/Si), which are each uniquely sensitive to the rate and nature of secondary mineral formation in weathering systems, to unmask the balance of secondary precipitation reactions contributing to C-Q observations through expansion to a C-R-Q (concentration – isotope/element ratio – discharge) framework. At present, laboratory characterization studies of the parameters which describe partitioning of delta 30Si and Ge/Si during secondary mineral growth are expanding, as well as datasets of these ratios versus discharge at the field scale. Yet a critical gap existing in pairing this information across a flow-through system with constrained fluid transit time distributions to verify appropriate model representation of observed behavior. This gap is contingent upon operational limitations. The slow weathering rates of silicate water-rock interactions impede the use of standard flow-through column designs at reasonable scales, while the complexity of natural systems limits the capacity to develop constrained relationships between reactivity and fluid travel time. Here, they will use LEO and employ a novel flux-weighted time approach to constrain transient fluid travel time distributions across the system. Through this combination of unique experimental facility, novel transient travel time constraint, reactive transport modeling, and (pseudo)isotopic tracers, they believe that a transformative advancement in process-level representation and prediction of C-R-Q relationships is achievable.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.

为水源提供水源的山坡硅酸盐岩石的风化决定了排水集水区的化学特征、从大陆到海洋的质量传输以及大气二氧化碳和陆地表面之间的关键反馈速率之间的基本关系的定量模型。景观排放量（Q）和水中溶质浓度（C）仍然是一个重大挑战，部分原因是基岩溶解与新次生矿物形成之间的紧密耦合。我们称之为硅酸盐风化。这种不确定性的核心是一个实际问题：硅酸盐风化的速率很慢，这意味着实验室中建造的典型流通柱甚至无法捕获高地流域硅酸盐风化的简化表示。自然山坡复杂且难以约束，在这项工作中，研究人员将利用独特的中尺度景观演化观测站（LEO）克服这种差异，该观测站提供了三个复制的收敛山坡。 LEO 设施位于生物圈 2 号中心内，每年为超过 100,000 名公众参观者提供易于理解的实例和演示，其中包括 10,000 名使用生物圈 2 号的学生。他们的 STEM 课程将培训两名博士生，从而形成一个跨三个机构的合作研究小组，并制作“展示”项目作为生物圈的一部分。 2 教育之旅，包括有关工作目的和状态的信息 最后，该项目开发和校准的反应式交通模拟将用作当前 NSF 研究协调网络的示例：基于社区的数值模拟教育基础设施。地球科学。即使在完全均匀的系统中，这些串联溶解和沉淀速率的无限组合也可能导致相同的溶质浓度。此外，这些反应通过不稳定渗透的不均匀流动路径发生。推进对 C-Q 关系的基于过程的理解的需要是提供嵌入同一模型框架中并减少自由参数数量的附加约束。在这里，研究人员将利用稳定同位素和微量元素比率的特征变化来诊断。具体来说，它们将硅同位素 (δ 30Si) 和锗硅比率 (Ge/Si) 配对，它们各自对速率和变化特别敏感。风化系统中次生矿物形成的性质，通过扩展至 C-R-Q（浓度 - 同位素/元素比 - 排放）框架来揭示有助于 C-Q 观测的次生降水反应的平衡。 目前，描述分配的参数的实验室表征研究。次生矿物生长过程中 Delta 30Si 和 Ge/Si 的数据正在不断扩大，这些比率与现场规模排放的数据集也在不断扩大，但在将流过系统中的这些信息与这些信息配对时存在着关键差距。受约束的流体传输时间分布来验证观察到的行为的适当模型表示，这种差距取决于操作限制，硅酸盐水-岩石相互作用的缓慢风化速率阻碍了标准流通柱设计在合理尺度上的使用。自然系统限制了在反应性和流体传播时间之间建立约束关系的能力，在这里，他们将使用 LEO 并采用一种新颖的通量加权时间方法来约束整个系统的瞬态流体传播时间分布。新颖的短暂旅行时间约束、反应输运模型和（伪）同位素示踪剂，他们相信过程级表示和 C-R-Q 关系预测方面的变革性进步是可以实现的。该奖项反映了 NSF 的法定使命，并通过使用基金会的评估进行评估，被认为值得支持。智力价值和更广泛的影响审查标准。