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.

摘要风蚀是干旱和半干旱地区的一种普遍现象，它导致土壤肥力丧失、大气辐射改变和空气污染，对全球和区域气候、农业和人类健康产生重要影响。当风速超过一定阈值时，就会发生侵蚀，阈值取决于包括表层土壤湿度在内的若干因素。认为在干旱地区，在空气干燥的条件下，表层土壤水分的变化可以明显地受到大气湿度变化的影响，对风蚀潜力有重要影响，这种影响目前还没有得到很好的理解或量化。有人认为，实际上土壤水分对风蚀敏感性的影响在空气中是相反的-土壤湿度的干范围对其在毛细范围内的影响，即，空气干燥的土壤越干燥，就越不易受风蚀的影响。拟议的研究将测试这一假设，并通过分析美国几种重要的农业土壤来量化影响，这些土壤极易受到风蚀，以及分类良好的干净沙子，这些沙子将作为“参考”土壤。特别是，该项目将（1）调查表层土壤水分的依赖性（即，（2）通过大量风洞试验确定临界风速与近地面空气湿度和温度之间的关系;（3）根据理论框架解释结果，该框架将解释颗粒间力对吸收层结合力的依赖性，以及颗粒间力和土壤基质势。这种方法将提供一个理论方程，表示作为空气湿度的函数的空气干燥土壤的临界风速。该方程的参数将通过风洞实验的结果来确定。土壤侵蚀潜力和表面水分含量之间存在的依赖类型的评估是至关重要的理解和模拟的风蚀和粉尘排放从旱地landscapes.Intellectual Merit.Most的表面水分对阈值风速的影响的现有研究集中在相对潮湿的土壤，其中毛细作用占主导地位的颗粒间的结合力。这项建议认识到风干土壤作为旱地景观大气灰尘和风蚀来源的重要性。在这些土壤中，水分含量有助于颗粒间的键合主要是作为吸附层键合。该提案认识到液体桥键（毛细作用）和吸附层键对土壤含水量的不同依赖性，并研究它如何影响土壤可蚀性和表面水分之间的关系。此外，由于很少有表层土壤湿度测量，表层土壤湿度对空气湿度的依赖性将被调查，并用于预测土壤可蚀性的状态。据我们所知，这是为数不多的研究集中在空气干燥土壤的可蚀性和第一个显示增加的可蚀性与水分含量。利用空气湿度作为表层土壤水分条件的替代物，也是研究水文控制对土壤侵蚀潜力的独特而新颖的方法。学生，和两名高中科学教师的研究方法和研究结果的介绍。它将通过纳入方案执行机构正在制定的课程来支持教育，并为处理类似问题的不同团体之间的合作提供基础。将寻求代表性不足群体的成员加入研究小组。拟议研究的结果将通过在学术期刊上发表文章和在会议上发表演讲的方式传播。社会将受益于更好地了解风蚀和沙尘产生的原因和预测能力。