摘要
应用平衡水气压法和差热分析法，对２０℃及３０℃下土壤气态水吸附与解吸等温线的特点和吸附水的解吸热特征进行了探讨。结果表明：（１）供试土壤在相对水气压达７２—７５％时，开始明显呈现出毛管凝聚作用；（２）除粘粒含量、比表面积及有机质含量等因素外，温度对土壤吸附气态水的数量也具有影响，３０℃下解吸平衡样品的剩余水量比２０℃下的大，而在通常相对水气压范围内３０℃下吸附平衡样品的吸附量比２０℃下的小；（３）在土壤水气的吸附与解吸之间存在滞后作用，其强弱与土壤的粘粒含量及比表面积的大小顺序一致，温度升高还可使滞后作用加强；（４）土壤吸附水偏摩尔解吸热在含水量很低时的值远大于其在含水量较高时的值，这表明干土在最初吸附水气分子时主要依赖于化学吸附。
Upon the experimental study by using methods of equilibrium vapor pressure and differential thermal analysis, the distinguishing features of adsorption and desorption isotherms of the gaseous water in soil at 20℃ and 30℃ and the characteristics of desorption heat of the adsorbed water are discussed in the present paper. The results are shown as follows:1. When the relative vapor pressure reached to 72-75%, capillary moisture condensation began to appear in the tested soil.2. Besides the clay content, specific surface area and organic matter content of soil, temperature also affected the amount of gaseous water adsorbed in soil, and the amount of residual water in samples of desorption equilibrium at 30℃ was more than that at 20℃ while the moisture content of adsorption equilibrium samples at 30℃ was less than that at 20℃ in the general range of the relative vapor pressure.3. A hysteresis effect existed between the adsorption and the desorption of soil water vapor, and its extent showed a consistent order with the clay content and specific surface area of soil. The hysteresis effect also strengthened with increasing temperature.4. The partial molar desorption heat of the adsorbed water at very low soil moisture content was far higher than that at high soil moisture, suggesting that it mainly depends on chemical adsorption for dry soil to adsorb water vapor molecules at the initial stage.
出处
《土壤学报》
CAS
CSCD
北大核心
1996年第3期280-286,共7页
Acta Pedologica Sinica
关键词
土壤水气
吸附
解吸
毛管凝聚
滞后作用
Soil water vapor, Adsorption, Desorption, Capillary condensation,Hysteresis effect
