CAREER: Field-scale quantification of dynamic physical properties in shrink-swell soils for improved hydrological prediction

收缩膨胀土是湿润时膨胀而干燥时收缩的粘性土。虽然这些土壤仅占全球土壤的2%，但由于其收缩膨胀特性，它们对水量和水质产生了不成比例的巨大影响，导致裂缝的形成，进而强烈影响关键的水文过程，包括水和污染物的运输，渗透，径流和植物用水。目前，还没有办法预测这些土壤的开裂行为，或在模型模拟中包括这些裂缝的影响。本研究的目的是提高我们的能力，以测量和预测裂缝形成的收缩膨胀土，最终目标是改善模型的水在土壤中的流动。这将使我们能够更好地管理和预测水和污染物在环境中的运动。此外，该项目还将为K-12教师提供培训机会，以了解土壤科学活动和课程，目的是吸引学生在年轻时进入该领域。迄今为止，除了个别地点外，收缩膨胀土壤的动态物理特性还没有得到充分的量化。此外，描述土壤含水量-容重关系的理论模型依赖于缺乏物理意义的经验参数。为了解决这一差距，该项目将在几个地点整合多种经过验证的非侵入性地球物理测量类型，以实现土壤含水量-体积密度关系的精确实地量化。拟议研究的目标是通过提供土壤含水量-容重关系的基于物理的、非特定地点的表示，提高对田间规模缩胀土壤动态特性的理解和量化能力。这一目标将通过以下目标来实现：1）在多个地点的收缩-膨胀土壤中，量化田间尺度下土壤水分和容重之间的关系，2）基于地表和地下图像量化土壤裂缝的数量和大小，以及3）产生有效土壤水力参数的田间尺度估计值，以表征土壤收缩、膨胀和裂缝的发展。拟议工作的教育目标是：1）通过为K-12教育工作者举办多个培训员土壤科学教育研讨会，促进Brochure参与土壤和地球科学，2）将项目成果纳入现有的开源土壤物理学入门教科书。本研究将为田间尺度土壤水分-容重关系提供一个基于物理的理论模型，并为该模型与现有数值模型的集成奠定基础。这将允许在收缩膨胀土壤区域动态表示裂缝的存在和大小，改善对渗透、地表径流、和土壤蓄水。该项目是共同的-该奖项由NSF地球科学部的水文科学和教育与人力资源项目资助。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准。

Shrink-swell soils are clayey soils that expand when wetting and shrink when drying. Though these soils account for only 2% of soil globally, they have a disproportionately large impact on water quantity and quality due to their shrink-swell properties, which lead to the formation of cracks that in turn strongly influence key hydrologic processes including water and contaminant transport, infiltration, runoff, and plant water use. Currently, there are no ways of predicting the cracking behavior of these soils or including the effects of these cracks in model simulations. The goal of this research is to improve our ability to measure and predict crack formation in shrink-swell soils, with the ultimate goal of improving models of water flow in soils. This will allow us to better manage and predict the movement of water and pollutants within the environment. In addition, the project will include training opportunities for K-12 teachers to learn about soil science activities and lessons, with the goal of attracting students to the field at a young age.To date, the dynamic physical properties of shrink-swell soils have not been adequately quantified beyond individual sites. Further, theoretical models describing the soil water content-bulk density relationship depend on empirical parameters that lack physical meaning. To address this gap, this project will integrate multiple proven, non-invasive geophysical measurement types at several locations to allow for the accurate field-scale quantification of the soil water content-bulk density relationship. The goal of the proposed research is to improve understanding of and ability to quantify dynamic properties of shrink-swell soils at the field scale by providing a physically-based, non-site-specific representation of the soil water content-bulk density relationship. This objective will be reached using the following objectives: 1) Quantify the relationship between soil moisture and bulk density at the field scale in shrink-swell soils at multiple sites, 2) Quantify the number and size of soil cracks based on surface and subsurface imagery, and 3) Produce field-scale estimates of effective soil hydraulic parameters for characterizing soil shrinkage, swelling, and crack development. The educational objectives of the proposed work are to 1) Broaden participation in soil and Earth sciences by hosting multiple train-the-trainer soil science education workshops for K-12 educators, and 2) incorporate project findings into an existing open-source introductory soil physics textbook. This research will provide a physically-based theoretical model of the soil water content-bulk density relationship at the field scale and lay a foundation for the integration of that model into existing numerical models. This will allow for the dynamic representation of the presence and size of cracks in areas with shrink-swell soils, improving estimates of infiltration, surface runoff, and soil water storage.This project is co-funded by the Hydrologic Sciences and Education and Human Resources programs in NSF's Division of Earth Sciences.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.