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CAREER: Altering transient soil evaporation mechanisms through hydrophobicity

职业：通过疏水性改变瞬时土壤蒸发机制

基本信息

批准号：
1651451
负责人：
Melanie Derby
金额：
$ 50万
依托单位：
Kansas State University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2017
资助国家：
美国
起止时间：
2017-06-01 至 2023-05-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1651451&HistoricalAwards=false
关键词：
CAREER Altering transient soil evaporation

项目摘要

Growing food with less water by reducing soil evaporationThe production of food requires adequate fresh water, and the sustainable production of food is a critical focus of the Food, Energy, and Water nexus. Reductions in soil evaporation rates will lower irrigation demands and overall water consumption for crop production, thereby conserving water worldwide and in the Ogallala Aquifer in the Great Plains. This research project will understand the effects of hydrophobic soil (where water beads up) on evaporation compared to typically hydrophilic soil (where water spreads out) through laboratory studies. Glass beads will be coated to make them hydrophobic and these beads will be used to simulate soil. Evaporation will be studied from a few beads and a tray of beads under weather conditions similar to fields. Next, a type of soil called Ottawa sand will be coated to become hydrophobic and evaporation will be measured from the plain, hydrophilic sand and hydrophobic sand. These experiments will show how soil hydrophobicity affects evaporation from soil. Soil hydrophobicity can occur naturally due to minerals, organic materials, or waxes. Information from these laboratory evaporation studies will be used to determine best agricultural practices to reduce water losses since the Ogallala Aquifer provides water for over 20% of corn, wheat, sorghum, and cattle produced in the United States. Additionally, this research project will attract diverse students due to the importance of the research. The Principal Investigator (PI) and student researchers will use bread baking as an analogy for soil evaporation with groups of female High School students at the EXCITE workshop at Kansas State University (KSU) and the PI and researchers will showcase the research to first year, female undergraduate students at an annual Research Open House. The PI will also teach an interdisciplinary course on heat and mass transfer in the Food, Energy, and Water nexus to graduate students from multiple colleges at KSU.This research will investigate transient evaporative phase change in a three-phase (i.e., soil, water, and air) system. The objectives of this study are to understand the impacts of hydrophobicity on evaporation mechanisms including contact line dynamics, capillary transport, and enhanced water vapor diffusion. Glass and Teflon-coated beads will be used to simulate soil for pore-level experiments. Evaporation will be modeled and experimentally investigated using a high speed and IR camera for a range of surface temperatures and realistic environmental conditions (e.g., air temperature and relative humidity and simulated solar irradiation). Contact lines will be observed for water evaporating from hydrophilic or hydrophobic single pores. Using knowledge obtained from these single pore studies, evaporation fronts and mechanisms such as capillary transport and enhanced water vapor diffusion will be investigated for multiple pores; water will be dyed with fluorescent dye rhodamine B and excited using a Nd:YAG laser. Color shifts will be used to identify evaporation fronts and liquid capillary transport for a given cross section of the porous material. In the final phase of the research, evaporation will be studied from layers of naturally hydrophilic and artificially hydrophobized Ottawa sand to understand the impacts of hydrophobicity on capillary transport and enhanced water vapor diffusion. This study will numerically and experimentally assess the relative impacts of hydrophobicity on these three primary evaporation mechanisms (i.e., contact line dynamics, capillary transport, and enhanced water vapor diffusion) and create a mechanistic map to show the dominant evaporation mechanism for field environmental conditions. As a result, the improved understanding of hydrophobicity on soil evaporation can inform agricultural best practices.

通过减少土壤蒸发，以更少的水种植粮食粮食生产需要充足的淡水，粮食的可持续生产是粮食、能源和水关系的关键焦点。土壤蒸发率的降低将降低灌溉需求和作物生产的总用水量，从而保护世界各地和大平原Ogallala含水层的水资源。该研究项目将通过实验室研究了解疏水性土壤（水珠）对蒸发的影响，与典型的亲水性土壤（水扩散）相比。玻璃珠将被涂覆以使其疏水，这些珠将用于模拟土壤。蒸发将在类似于田地的天气条件下从几个珠子和一盘珠子进行研究。接下来，一种称为渥太华沙的土壤将被涂覆成疏水性的，并将从平原、亲水性沙和疏水性沙测量蒸发。这些实验将显示土壤疏水性如何影响土壤蒸发。土壤疏水性可以由于矿物质、有机材料或蜡而自然发生。这些实验室蒸发研究的信息将用于确定减少水损失的最佳农业实践，因为Ogallala含水层为美国生产的20%以上的玉米，小麦，高粱和牛提供水。此外，由于研究的重要性，这个研究项目将吸引不同的学生。主要研究者（PI）和学生研究人员将使用面包烘烤作为土壤蒸发的类比，与堪萨斯州立大学（KSU）的EXCITE研讨会上的女高中生群体，PI和研究人员将在年度研究开放日上向一年级的女本科生展示研究。PI还将向KSU多个学院的研究生讲授关于食品，能源和水关系中的传热和传质的跨学科课程。这项研究将研究三相（即，土壤、水和空气）系统。本研究的目的是了解疏水性对蒸发机制的影响，包括接触线动力学，毛细运输，增强水蒸气扩散。玻璃和特氟隆涂层珠将被用来模拟土壤孔隙水平的实验。蒸发将使用高速和IR相机针对一系列表面温度和现实环境条件（例如，空气温度和相对湿度以及模拟太阳辐射）。对于从亲水性或疏水性单孔中蒸发的水，将观察到接触线。利用从这些单孔研究中获得的知识，将研究多孔的蒸发前沿和机制，如毛细运输和增强的水蒸气扩散;水将用荧光染料罗丹明B染色，并使用Nd：YAG激光激发。色移将用于识别多孔材料给定横截面的蒸发前沿和液体毛细管传输。在研究的最后阶段，蒸发将从自然亲水和人工疏水渥太华砂层进行研究，以了解疏水性对毛细运输和增强水蒸气扩散的影响。本研究将通过数值和实验评估疏水性对这三种主要蒸发机制的相对影响（即，接触线动力学、毛细管输送和增强的水蒸气扩散），并创建机械图以显示现场环境条件下的主要蒸发机制。因此，提高对土壤蒸发疏水性的理解可以为农业最佳实践提供信息。