土壤水分特征曲线滞后性与比水密度拟合研究

Fitting Research on Hysteresis Phenomenon of Soil Water Characteristic Curves and Soil Water Capacity

采用水银张力计称质量法，室内测定长江河口地区土壤（地表以下0～20、20～50、50～100cm）水分特征曲线，用van-Genuchten模型拟合，并求得土壤比水密度与水吸力的关系曲线。结果表明，随着土壤深度的加深，土壤持水性能增强；各层土壤均易吸水，难失水，存在滞后性；表层土壤滞后现象最明显，保水性最好，底层土壤次之；较低吸力下，上层土壤供水性较好。中下层较差，较高吸力下则相反；表层、中层、底层土壤吸力分别为209、235、222cm水柱时，脱湿一吸湿过程比水密度相同，土壤含水率绝对差最大，低于此吸力．土壤吸水强度较大，而高于此吸力，土壤排水强度较大。

The soil water characteristic curves in the estuary of the Yangtze river（under the surface of 0- 20 cm, 20-50 cm, 50-100 cm） were measured indoor by the method of tension meter weighting. The fit- ted parameters were obtained with the van-Genuchten model, and the relationships between the soil water capacity and water suction were obtained. The results showed that with the deepening of soil depth, the water binding capacity became better. It was easier absorption and harder desorption, existing hysteresis phenomenon under different depths and the phenomenon of surface soil was the most obvious and the wa- ter-retaining property was also the best, the deeper soil taking the second place. With lower suction range, the water supply capability of surface soil was better and poorer of the lower soil; during higher suction range, the water supplying capability of lower soil was better and it was poorer of the surface soil. When the soil suctions of surface, middle and deeper soil were 209 cmH2O, 235 emH20, 222 cmH20, respec- tively, lhe absolute differences of soil moisture contents were the largest and the soil water capacity were the same during the desorption and absorption processes. Below this suction, soil suction strength was greater, while soil drainage strength was greater exceeding the suction.