单种及多种盐分在土壤中的运移

Transports of single or multiple solutes in soil

建立了土壤热、湿、气及盐分耦合运移的数学模型,通过数值模拟研究了地下水深度分别为0.5 m,1.0m,1.5 m和2.0 m,地下水矿化度为5.0×10-3,以及土壤盐分初始质量分数为0时,5 a后土壤溶液中NaCl,KCl,CaCl2和MgSO4分别沿土壤剖面的质量分数分布.计算结果表明相同深度处4种盐分的质量分数大小顺序为:KCl>NaCl>CaCl2>MgSO4,可见扩散系数越大的盐分,其质量分数也越高;地下水位较高时这种差别更大.此外,还分别采用单组分和多组分模型对KCl和NaCl在土壤中的运移进行了比较,发现多组分效应对NaCl的影响更大,而对KCl的影响较小,因此采用多组分模型能够提高NaCl的预报精度.

A mathematical model to simulate the transports of heat, moisture, gas and solute in soil was established. First, numerical simulations were conducted to investigate the transports of four single solutes, NaCl, KCl, CaCl2 and MgSO4, under the following conditions, ground water levels of 0. 5 m, 1.0 m, 1.5 m and 2.0 m; ground water salinity of 5.0×10^5, and initial concentration of 0. The numerical results of 5 years show that at the same depth, the concentration sequence of the four solutes was： KCl〉NaCl〉CaCl2〉MgSO4, the larger the diffusivity of the solute, the higher of its concentration. Moreover, the concentration differences were more evident in the case of shallow groundwater level. The multiple species effect of simultaneous transport of NaCl and KCl was also studied, after the single species model （SSM） was compared with the multiple species model （MSM）, which demonstrated that the multiple species effect was more prominent for NaCl and less for KCl. Therefore, using the multiple species model can improve the prediction accuracy of NaCl.