Investigation of Dominant Controls on Electrical Properties of Granitic Regolith

地球的临界区是从基岩顶部延伸到树冠的薄层。尽管临界区的厚度相对较薄，但它通过提供水和食物等维持生命的资源，在我们的社会中发挥着至关重要的作用。了解临界区地下部分的内部结构是帮助我们了解和预测其在全球水、能量、碳和养分循环中的作用的重要一步。地球物理成像被用来“看到”地表下看不见的临界区。然而，获取的地球物理图像需要转换为其他科学家可以理解和使用的物理属性，如密度、水分含量和化学成分。该项目将结合实验室和地球物理实地调查，促进目前对关键区地质材料物理性质的了解。该项目的成果将帮助科学家更好地描绘地球这一薄薄但宝贵的临界层的亚表层。研究人员将通过野外采样、实验室实验和理论建模相结合的方法来调查花岗岩风化岩电学特性的主要控制因素。将从现场采集花岗岩风化岩样，并将使用新开发的土柱和配备新型水文地球物理探头的压力板萃取器测量其在受控水力状态下的电学性质。实验数据将被用来量化水力状态、化学风化引起的结构变化和化学风化引起的矿物学变化对充分发育的风化层和风化前缘样品的电性的相对影响。将开发一种新的电学模型来描述整个风化层。这种基于过程的理解和建模将增强我们洞察复杂地下环境和监控各种重要地下过程的能力。该项目由水文科学、已建立的激励竞争性研究计划(EPSCoR)以及地球生物学和低温地球化学计划联合资助。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The Earth's critical zone is the thin layer that extends from the top of the bedrock to the canopy of trees. Despite its relatively thin thickness, the critical zone plays a vital role in our society by providing life-sustaining resources such as water and food. Knowing the internal structure of the underground part of the critical zone is an important step that will help us understand and predict its role in global water, energy, carbon, and nutrient cycles. Geophysical imaging is used to "see" the unseen critical zone underneath the surface. However, the acquired geophysical images need to be translated into physical properties such as density, moisture content, and chemical composition that are understandable and usable to other scientists. This project will advance current understanding of the physical properties of geological materials in the critical zones by using a combination of laboratory and geophysical field investigations. The outcome of this project will help scientists better depict the subsurface of this thin but invaluable critical zone layer of the Earth. The researchers will investigate the dominant controls on the electrical properties of granitic regolith from a combination of field sampling, laboratory experiments, and theoretical modeling. Granitic regolith samples will be collected from the field, and their electrical properties, under controlled hydraulic states, will be measured using a newly developed soil column and a pressure plate extractor equipped with novel hydro-geophysical probes. Experimental data will be used to quantify the relative influences of hydraulic state, chemical weathering-induced textural change, and chemical weathering-induced mineralogy alternation on the electrical properties of the samples in both fully developed regolith and the weathering front. A new electrical model integrating chemical weathering will be developed to describe the entire regolith. This process-based understanding and modeling will enhance our ability to see into the complex underground environment and monitor various important subsurface processes. This project is jointly funded by the Hydrologic Sciences, the Established Program to Stimulate Competitive Research (EPSCoR), and Geobiology and Low Temperature geochemistry programs.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.