掺砂量对中度盐碱土壤水力特性及溶质运移过程的影响

Effect of Sand Incorporation on Hydraulic Properties and Solute Transport Processes in Moderately Saline Soils

[目的]为探究不同掺砂量对中度盐碱土壤水力特性和溶质运移过程的影响。[方法]采用室内土柱试验,设置4种掺砂比例CK(掺砂0)、B1(掺砂10%)、B2(掺砂15%)、B3(掺砂20%),研究中度盐碱土壤在不同掺砂量条件下的土壤水力特性和溶质运移过程变化规律并进行模型模拟。[结果](1)掺砂量在0~20%内,中度盐碱土掺砂明显影响土壤水分特征曲线变化,掺砂比例越大,曲线越靠近Y轴。在任一吸力条件下土壤含水率表现为CK>B1>B2>B3。且掺砂比例越大,土壤小孔隙数量越多,微小孔隙减少,土壤持水性能减弱。土壤的饱和导水率随掺砂量的增加而增大。(2)随掺砂量的增加,溶质穿透曲线明显左移,初始穿透时间、完全穿透时间及穿透总历时均减少,B1、B2、B3处理总穿透历时分别比CK减少34.48%,47.22%,69.71%。(3)CED方程和两区模型均能较好地模拟掺砂条件下土壤中溶质运移状况,但相较于CDE方程,两区模型的拟合精度更高。对两区模型拟合参数进行分析发现,随掺砂量的增加,土壤孔隙流速、可动区含水比率和质量交换系数逐渐增大,而水动力弥散系数和弥散度呈减小趋势。[结论]盐碱土掺砂能够有效改善土壤水力特性,促进溶质在土壤中运移,有助于缓解盐碱对作物生长的不利影响。研究结果可为盐碱土改良与治理工作提供参考,为未来的研究和实践提供理论支持和实践指导。

[Objective]To investigate the effects of different sand blending rates on the hydraulic properties and solute transport processes of moderately saline soils.[Methods]Four sand mixture ratios were established using an indoor soil column test:CK(0 sand mixing),B1(10%sand mixing),B2(15%sand mixing),and B3(20%sand mixing),to investigate the solute transport characteristics of moderately saline soils under different sand mixing conditions and to perform model simulations.[Results](1)In the range of 0~20%,sand mixing in moderately saline soil will obviously affect the change of soil moisture characteristic curve,and the larger the proportion of sand mixing,the closer the curve is to the Y-axis.Under any suction condition,the soil water content was ranked as CK>B1>B2>B3,and the larger the proportion of sand mixing,the more small pores in the soil,the reduction of small pores,and the weakening of soil water-holding properties.The saturated hydraulic conductivity of the soil increased with the increase of sand doping.(2)With the increase of sand doping,the solute penetration curve shifted significantly to the left,and the initial penetration time,complete penetration time,and total penetration time were reduced,and the total penetration time of B1,B2,and B3 treatments were reduced by 34.48%,47.22%,and 69.71%,respectively,compared with that of CK.(3)Both the CED equation and the two-zone model can simulate the solute transport in soil under sand doping conditions well,but the fitting accuracy of the two-zone model is higher compared with the CDE equation.Analyses of the fitted parameters of the two-zone model showed that the soil pore flow rate,the water content ratio of the movable zone and the mass exchange coefficient gradually increased with the increase of sand doping,while the hydrodynamic dispersion coefficient and the dispersion degree showed a decreasing trend.[Conclusion]Therefore,sand blending in saline soils can effectively improve soil hydraulic properties,promote solute transport in the soil,and help alleviate the adverse effects of salinity on crop growth.The results of this study can provide reference for saline soil improvement and management work,and provide theoretical support and practical guidance for future research and practice.