STUDY ON WATER AND SALT MOVEMENT DURING SOIL FREEZING AND THAWING

土壤冻融过程中水盐运动的研究

基本信息

批准号：
11460113
负责人：
AKAE Takeo
金额：
$ 8.58万
依托单位：
OKAYAMA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2001
项目状态：
已结题

项目摘要

1. As a background and a beginning point of this research, an example of water and salt movement during soil freezing and thawing was introduced from Hetao Irrigation District, Inner Mongolia, China. Regional and field level salt movement, relation between salt accumulation in spring and fall irrigation, soil water supply and leaching effect by the fall irrigation, improvement method of the salinized land were discussed.2. Dielectric constant of frozen cemented soil was measured and the water in it was classified into hydrated and structural bound state. The quantity of those water was estimated. Water potential of the structural bound water was also estimated.3. Thermal conductivity of frozen and unfrozen soil was calculated by analyzing the amplitude of temperature oscillation in relation to depth when sinusoidal temperature oscillation was given to the soil surface. The method was applied to determine the soil temperature change in the field, and thermal conductivity of frozen and u … More nfrozen state was estimated by this method.4. A new method to measure unsaturated hydraulic conductivity of a frozen soil was developed. A frozen soil sample was equilibrated under centrifuge force field and water loss was measured by change of the moisture profile in the sample. The hydraulic conductivity was calculated by the water loss divided by the gradient of centrifuge force and time. The measured hydraulic conductivity ranged from 10^<-9> cm/s to 10^<-8> cm/s.5. Soil was frozen and thawed from the bottom of the soil column, and the soil moisture and salt movement was measured. The result was examined against the initial soil moisture and salt concentration. The higher the initial soil moisture, the water and salt movement increased. Heat flux in the soil was estimated by the thermal conductivity and the measured temperature distribution.6. Soil column was frozen and thawed from the top surface, and water and salt movement was measured under conditions of open or closed surface and high or low initial soil moisture. The frozen depth was influenced little by the initial soil moisture, but greater movement of water and salt toward freezing front was observed at high initial soil moisture. At high soil moisture, salt accumulation was proceeded after thawing under opened surface condition. Less

1. 作为本研究的背景和起点，介绍了内蒙古河套灌区土壤冻融过程中水盐运动的实例，区域和田间盐分运动、春季盐积累的关系。并探讨了秋灌、土壤水分补给及秋灌淋溶效应、盐碱化土地的改良方法等。2．测定了冻土的介电常数，并将其分为水合态和结构束缚态。还估算了结构结合水的水势。通过分析对土壤施加正弦温度振荡时温度振荡幅度与深度的关系，计算了冻结和未冻结土壤的热导率。将该方法应用于现场测定土壤温度变化，并利用该方法估算了冻结态和非冻结态的导热系数。 4．提出了一种测量冻结土非饱和导水率的新方法。将冷冻土壤样品在离心力场下平衡，并通过样品中水分分布的变化来测量水力传导率，该水力传导率通过水力损失除以离心力和时间的梯度来计算。范围为10^<-9>cm/s至10^<-8>cm/s。5.从土柱底部开始冻结和解冻土壤，测量土壤水分和盐分运动的结果。检查针对初始土壤湿度和盐浓度。初始土壤湿度越高，通过热导率和测量的温度分布来估计土壤中的水和盐运动增加。6．在开放或封闭的表面以及高或低的初始土壤湿度条件下测量了水和盐的运动，冻结深度受初始土壤湿度的影响很小，但在高的情况下观察到水和盐向冻结前沿的运动更大。初始土壤湿度土壤湿度高时，盐分积累进行。解冻后在开放的表面条件下。