SitS: Coupling High Frequency Soil Solute Signals and Scalable Simulations to Quantify Biogeochemical Mechanisms Governing Water Quality

该奖项是通过“土壤中的信号(SITS)”征集，这是美国国家科学基金会和美国农业部国家粮食和农业研究所(USDA NIFA)之间的合作伙伴关系。农业地区普遍面临着水质差的问题，这与作物对化肥提供的养分的使用效率低下有关。土壤在调节化肥中的养分是否真的增加了植物生长的价值，或者养分是否没有被吸收并最终污染地下水和溪流方面发挥了关键作用。由于无法直接观察土壤水中溶解的化学物质的活动，理解如何促进土壤中养分的保留、减少水资源污染的可能性以及增加向作物生产输送养分的能力受到了共同的阻碍。这项工作将使用嵌入土壤中的新型传感器，在一系列实验和田间条件下观察一套添加的营养物质，包括关键营养物质和主要的水污染物硝酸盐。这些埋入地下的传感器将以电子方式传输数据，并将使用土壤模型来解释信号。这项工作的结果将确定在大平原北部的模拟雨水灌溉系统中平衡水质和可持续植物生产的条件。该项目还将推动支持科学、技术、工程和数学(STEM)教育的活动，以及参与该地区服务不足的社区。如果成功，该项目将通过提供技术来提高农业化肥的使用效率并减少这些化肥对环境的负面影响，从而在保护水资源的同时加强国家的粮食安全。水在土壤中的移动调节风化反应和生物地球化学循环，以驱动输送到地下水和河流的溶质负荷。然而，目前的传感器技术和溶质运移模拟方法限制了解决有关土壤过程的关键问题的有效性，这些问题支配着土地利用对水质的影响。在土壤中，高度可溶和可移动的硝酸根离子提供了氮(N)有效性和转化的指示剂，在扰动和施肥系统中是一个经常被研究但未被观察到的信号分子。土壤中的硝酸盐浓度目前是通过破坏性土壤采样来量化的，这是一项使用了一个多世纪的技术。缺乏对土壤水中硝酸盐浓度的现场和实时测量。有两个限制阻碍了对硝酸盐信号的理解：1)缺乏对土壤溶液成分的高频观测，2)缺乏区分由土壤结构孔隙结构变化所驱动的硝酸盐浓度动态的观测。这项工作将开发、测试和产生一个耦合的多尺度传感器方法和溶质运移建模框架，能够将反应动力学从孔隙尺度扩展到剖面尺度。该小组将在测量一般水质(电导率、pH、温度)的同时进行硝酸盐的测量，以解决土壤水生物地球化学与孔隙结构变化相关的变化如何决定农业土壤中硝酸盐的去向和迁移。结果将包括建立新的技术，探索从孔隙到剖面的土壤物理结构、水文动力学和溶质反应机制之间的相互关系。这些关于土壤系统的基本见解将有助于平衡水质保护和可持续食品生产的努力。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。

This award was made through the "Signals in the Soil (SitS)" solicitation, a collaborative partnership between the National Science Foundation and the United States Department of Agriculture National Institute of Food and Agriculture (USDA NIFA). Agricultural areas face a pervasive problem of poor water quality that is tied to inefficient use of fertilizer-provided nutrients by crops. Soils play a key role in regulating whether nutrients from fertilizers actually add value to the plant growth or if the nutrients are not absorbed and end up contaminating groundwaters and streams. The ability to understand how to promote the retention of nutrients in soils, reduce the potential for water resource contamination, and increase delivery of nutrients to crop production are collectively hampered by the inability to make direct observations of the activities of dissolved chemicals in soil water. This work will use new sensors embedded in soils to observe a suite of added nutrients, including the key nutrient and major water contaminant nitrate, over a range of experimental and field conditions. These buried sensors will transmit data electronically, and a soil model will be used to interpret the signals. The results of this work will identify conditions that balance water quality and sustainable plant production in model rain-irrigated systems of the Northern Great Plains. This project will also motivate activities supporting science, technology, engineering, and math (STEM) education and participation in underserved communities of the region. If successful, this project will strengthen the nation’s food security while preserving water resources by providing technology that makes the use of agricultural fertilizers more efficient and decreases the negative environmental impacts of these fertilizers.The movement of water through soils mediates both weathering reactions and biogeochemical cycles to drive solute loads delivered to groundwater and rivers. However, current sensor technologies and solute transport modeling approaches limit the efficacy of efforts to address critical questions about soil processes governing the consequences of land use for water quality. In soils, the highly soluble and mobile nitrate ion provides an indicator of nitrogen (N) availability and transformation, serving as a frequently studied yet under-observed signal molecule in disturbed and fertilized systems. Nitrate concentrations in soils are currently quantified using destructive soil sampling, a technique used for over a century. In-situ and real-time measurements of nitrate concentrations in soil waters are lacking. Two limitations hamper understanding of the nitrate signal: 1) lack of high-frequency observations of soil solution composition, and 2) lack of observations that differentiate dynamics in nitrate concentrations driven by variation in the pore structure of the soil fabric. This work will develop, test, and produce a coupled multi-scale sensor approach and solute transport modeling framework capable of scaling reaction dynamics from pore to profile scales. The team will undertake measurements of nitrate in parallel with measurements of general water quality (conductivity, pH, temperature), to address how variation in soil water biogeochemistry associated with variation in pore structure dictates nitrate fate and transport in agricultural soils. Results will include the establishment of new technologies for exploring mechanisms interrelating physical soil structure, hydrologic dynamics, and solute reaction regimes from pores to profiles. These fundamental insights about soil systems will benefit efforts to balance water quality protection with sustainable food production.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.