Solute Transport due to Moisture and Temperature Movement within Unsaturated Soil

实验室测试是在对砂柱顶部加热的情况下进行的。对比非加热塔和加热塔，氯离子的溶质浓度有明显的差异。从加热柱中获得了很大的浓度值，特别是在表面。不同柱子的饱和度没有差别。造成这种差异的主要原因是表面加热引起的水蒸气运动和热量传递。降水的影响也通过加热和非加热沙柱进行了验证。在非加热柱中，由于孔隙水垂直向下流动的对流，浓度降低，而在加热柱中，浓度一度超过初始值。具体原因尚未明确，但这一结果暗示了天气条件对地表附近溶质运移的重要性。建立了反映水蒸气和孔隙水运移和热量运移的溶质运移模型。数值算例表明了该模型的有效性。在实验室试验中的应用表明，该模型与试验结果吻合较好。从这些计算中也发现了一些改进。热和溶质输运中对流项的数值计算方法应结合拉格朗日格式加以改进。蒸发率的估算应从实验室试验中准确地作出。

Laboratory tests were carried out under applying heat to the top of the sand column. Comparisons between a nonheating and heating columns showed conspicuous difference in solute concentration of chloride ion. Large values of the concentration was obtained from the heating column, especially at the surface. Degree of saturation was not different among each column. The main reason for this difference is vapor movement and heat transfer due to the heating at the surface.The effect of precipitation was also checked using a heating and nonheating sand column. In the nonheating column, concentration decreased due to convection of vertically downward flow of pore water, on the other hand, concentration once exceeded the initial value in heating column. Exact reason was not cleared out, but this result implies the importance of weather conditions for solute transport near the ground surface.Solute transport model was developed reflecting vapor and pore water movement and heat transport. Numerical examples were demonstrated to show the efficiency of the model. The application to the laboratory tests showed a good agreement between the model and the test results. Some improvements were also indicated from these computations. Numerical method for the convection terms in heat and solute transport should be improved considering the Lagrangian scheme. Estimation of evaporation rate should be exactly made from the laboratory tests.