原状盐渍土不同盐分含量对土壤水分特征曲线的影响

Effects of Different Salt Contents of Undisturbed Saline Soil on Soil Moisture Characteristic Curves

为探究原状盐渍土不同盐分含量对土壤水分特征曲线的影响,选用无、轻度和重度盐渍化地块土样测定其土壤水分特征曲线,采用van Genuchten-Mualem模型对无、轻度和重度盐渍化土壤土-水曲线及参数进行拟合分析,并分析不同盐分含量对累积当量孔径分布和土壤水分常数的影响。结果表明:原状盐渍土土壤水分特征曲线主要受盐分含量的影响,轻度盐渍化下的含盐量增加土壤持水性,但重度盐渍化下土壤中的含盐量则减小了土壤持水性;van Genuchten-Mualem模型的参数n值随原状盐渍土盐分含量的增加先减小后增大,而进气值倒数α值则呈减小趋势;VG模型对于YZ1和YZ3地块60 cm土层土壤土水-曲线拟合精度高于YZ2地块;轻度盐渍化土壤较无盐渍化土壤40 cm、60 cm深度的极微孔隙和微孔隙占总孔隙的比例分别增加11.75%和19.25%,田间持水率分别增大32.6%、28.8%;随土壤深度增加,重度盐渍化土壤较无盐渍化土壤的极微孔隙和微孔隙占总孔隙的比例分别减小28.08%、40.61%和21.64%,田间持水率分别减小34.4%、34.1%和6.5%。研究可为盐渍土的预防和改良提供一定的理论依据。

In order to explore the influence of different salt content on SWCC of undisturbed saline soil,the SWCC of non-saline,light saline and heavy saline soil was measured.The van Genuchten-Mualem model was used to fit the soil-water curve and parameters of non-saline,light saline and heavy saline soil and the influence of different salt content on cumulative equivalent pore size distribution and soil moisture constant was analyzed.The results showed that the soil water characteristic curve of undisturbed saline soil was mainly affected by salt content;The salt content under slight salination increased the soil water holding capacity,but the salt content of severely saline soil decreased the soil water holding capacity;With the increase of salt content in undisturbed saline soil,the parameter n value of van Genuchten-Mualem model first decreased and then increased,while the reciprocalαvalue of intake value decreased;The fitting accuracy of VG model for soil water-curve of 60 cm soil layer in YZ1 and YZ3 plots were higher than that in YZ2 plot.Compared with saline soil,the proportion of microporosity in 40 cm and 60 cm soil layers increased by 11.75%and 19.25%respectively,and the field water holding rate increased by 32.6%and 28.8%respectively.With the increase of soil depth,the proportion of microporosity in the total porosity of severely saline soil decreased by 28.08%,40.61%and 21.64%respectively,and the field water holding rate decreased by 34.4%,34.1%and 6.5%respectively.The research can provide some theoretical basis for the prevention and improvement of saline soil.