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Evaporation from soils and control of the salt accumulation

土壤蒸发和盐积累的控制

基本信息

批准号：
08660284
负责人：
SHIOZAWA Sho
金额：
$ 1.66万
依托单位：
University of Tsukuba
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1998
项目状态：
已结题

项目摘要

Dissolved salt in soil move upward with soil water movement during evaporation and accumulates at the evaporating surface under the condition where potential evaporation exceeds the amount of precipitation. As the evaporation rate decreases with formation of dry layer at the soil surface, predicting the decreased evaporation rate with a thickness of the dry layer is necessary for prediction and control of the salt accumulation.It has confirmed that evaporation occurs at the bottom of dry layer (the boundary between wet layer) and the evaporation rate is determined by vapor diffusion through the dry layer, by measuring temperature profiles in soil, evaporation rate, water content and relative humidity profile in soil, at a investigation plot with the soil of Kanto Loam. I came up with a model of evaporation in which evaporation rate is proportional to the vapor density difference between at the atmosphere and at the bottom of the dry layer, and also the proportionality constant is determined by the series resistance of the boundary layer resistance in air and dry layer resistance for vapor diffusion in soil. The calculated evaporation rates agree well with the observed evaporation ratesGetting these knowledge, I explored fields in Faisalabad, Pakistan where salt accumulation and soil degradation was serious. I also examined and evaluate the actual means that farmers or researcher in Pakistan did. I proposed counter measures for the problems, depending on the knowledge on water movement in soil-plant-atmosphere system.

土壤中的溶解盐分在蒸发过程中随土壤水分运动而向上移动，在潜在蒸发量超过降雨量的情况下积聚在蒸发面。由于土壤蒸发速率随着土壤表面干层的形成而减小，因此预测蒸发速率随干层厚度的减小对于预测和控制盐分积累是必要的。通过对关东壤土调查样地的土壤温度剖面、蒸发速率、土壤含水率和相对湿度剖面的测量，证实了蒸发发生在干层底部(湿层之间的边界)，蒸发速率是由通过干层的水汽扩散决定的。我提出了一个蒸发模型，其中蒸发率与大气和干层底部的水蒸气密度差成正比，比例常数由空气中的边界层阻力和土壤中水蒸气扩散的干层阻力的串联阻力决定。计算的蒸发率与观测到的蒸发率很好地吻合。为了了解这些知识，我考察了巴基斯坦费萨拉巴德的油田，那里的盐分积累和土壤退化严重。我还检查和评估了巴基斯坦农民或研究人员所做的实际手段。根据对土壤-植物-大气系统水分运动的认识，提出了解决问题的对策。