Collaborative Research: The Effect of Atmospheric Humidity on the Susceptibility of Dry Soils to Wind Erosion

合作研究：大气湿度对干土风蚀敏感性的影响

• 批准号: 0409305
• 负责人: Paolo D'Odorico
• 金额: $ 14.07万
• 依托单位: University of Virginia Main Campus
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-09-01 至 2007-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0409305&HistoricalAwards=false
• 关键词: Collaborative; Research; Effect; Atmospheric; Humidity

ABSTRACTWind erosion is a widespread process in arid and semi-arid regions, and contributes to loss of soil fertility, alteration of atmospheric radiation, and air pollution, with important impacts on global and regional climates, agriculture, and human health. Erosion occurs when wind speed exceeds a certain threshold, the value of which depends on a number of factors, including surface soil moisture. It is argued that in arid regions, under air-dry conditions, variations in surface soil moisture can be significantly affected by changes in atmospheric humidity, with an important effect on wind erosion potential, and that this effect is not currently well understood or quantified.It is argued that in fact the effect of soil moisture on susceptibility to wind erosion is opposite in the air-dry range of soil moistures to its effect in the capillary range, i.e., that the drier an air-dry soil is, the less susceptible it is to wind erosion. The proposed research will test this hypothesis and quantify the effect by analysis of several important agricultural soils of the United States, which are strongly subject to wind erosion, as well as well-sorted, clean sands, which will function as "reference" soils. In particular, the project will (1) investigate the dependence of surface soil moisture (i.e., in a few grain layer) on air humidity and temperature; (2) determine the relationship between threshold wind velocity, and near surface air humidity and temperature by means of a number of wind tunnel tests, and (3) interpret the results in terms of a theoretical framework that will account for the dependence of interparticle forces on absorbed layer bonding on interparticle forces and soil matric potential. This approach will provide a theoretical equation expressing threshold wind velocity as a function of air humidity for air-dry soils. The parameters of this equation will be determined through the results of the wind tunnel experiments. The assessment of the type of dependence existing between soil erosion potential and surface moisture content is crucially important to the understanding and modeling of wind erosion and dust emission from dryland landscapes.Intellectual Merit.Most of the existing studies on the effect of surface moisture on the threshold wind velocity have concentrated on relatively wet soils, in which capillarity dominated interparticle bonding forces. This proposal recognizes the importance air-dry soils as sources of atmospheric dust and wind erosion in dryland landscapes. In these soils, water content contributes to interparticle bonding mostly as adsorbed-layer bonding. The proposal recognizes the different dependence of liquid-bridge bonding (capillarity) and adsorbed-layer bonding on soil water content, and investigates how it affects the relationship between soil erodibility and surface moisture. Moreover, because surface soil moisture measurements are seldom available, the dependence of surface soil moisture on air humidity will be investigated and used to predict the state of soil erodibility. To our knowledge, this is one of the very few studies concentrating on the erodibility of air-dry soils and the first one showing an increased erodibility associated with increasing moisture contents. The use air humidity as a surrogate for surface soil moisture conditions is also a unique and novel approach to the study of the hydrologic controls on soil erosion potential.Broader ImpactsThis project will involve the training of a Ph.D. student, and two high school science teachers in the methods of research and of presentation of research results. It will support education by integration into a course being developed by the PIs, and provide a basis for collaboration between different groups working on similar questions. Members of underrepresented groups will be sought for inclusion in the research team. The results of the proposed research will be disseminated through publications in scholarly journals and conference presentations. Society will benefit from the improved understanding of the causes of and the ability to predict wind erosion and dust generation.

风蚀是干旱和半干旱地区普遍存在的一种过程，造成土壤肥力损失、大气辐射变化和大气污染，对全球和区域气候、农业和人类健康产生重要影响。当风速超过某一阈值时，就会发生侵蚀，该阈值的大小取决于许多因素，包括地表土壤水分。在干旱地区，在风干条件下，表层土壤水分的变化可以显著地受到大气湿度变化的影响，这对风蚀潜力有重要的影响，但这种影响目前还没有被很好地了解或量化。事实上，土壤水分对风蚀敏感性的影响在土壤水分的风干范围内与其在毛管范围内的影响是相反的，即风干土壤越干燥，对风蚀的敏感性就越小。这项拟议的研究将检验这一假设，并通过分析美国几种重要的农业土壤来量化其影响，这些土壤非常容易受到风蚀的影响，以及分类良好、干净的沙子，这些沙子将起到参考土壤的作用。特别是，该项目将(1)调查表层土壤水分(即少数颗粒层中的水分)对空气湿度和温度的依赖关系；(2)通过一些风洞试验确定阈值风速与近地表空气湿度和温度之间的关系，以及(3)根据理论框架解释结果，该框架将解释颗粒间作用力对吸收层结合的依赖程度与颗粒间力和土壤基质势之间的关系。这种方法将提供一个理论方程，表达风干土壤的阈值风速作为空气湿度的函数。该方程的参数将通过风洞实验结果来确定。土壤侵蚀潜势与地表含水率之间存在的相关性的评估对于理解和模拟旱地风蚀和沙尘排放是至关重要的。该提案认识到风干土壤作为旱地地貌中大气粉尘和风蚀的来源的重要性。在这些土壤中，水分对粒间结合的贡献主要是以吸附层结合的形式进行的。该方案认识到液桥结合(毛细作用)和吸附层结合对土壤水分的不同依赖关系，并研究了它如何影响土壤可蚀性与地表湿度之间的关系。此外，由于表层土壤水分测量很少，因此将研究表层土壤水分与空气湿度的关系，并将其用于预测土壤可蚀性状态。据我们所知，这是少数几个集中于风干土壤可蚀性的研究之一，也是第一个表明可蚀性随着水分含量的增加而增加的研究。用空气湿度代替表层土壤水分状况，也是研究土壤侵蚀潜力的水文控制的一种独特而新颖的方法。广泛的影响这个项目将包括一名博士生和两名高中理科教师在研究方法和研究成果展示方面的培训。它将支持教育，将其纳入私人投资机构正在开发的课程，并为解决类似问题的不同小组之间的合作提供基础。将寻求代表人数不足的群体的成员加入研究小组。拟议研究的结果将通过学术期刊上的出版物和会议发言进行传播。社会将受益于对风蚀和粉尘产生原因的更好理解和预测能力的提高。