非等温条件下潜水含水层坝后残留咸水淡化过程研究

Effects of Temperature on Residual Saltwater Desalinization Behind the Subsurface Dam in Unconfined Aquifer

本文采用场地尺度的二维地下水-盐-热耦合数值模型,研究了咸淡水温差对残留咸水淡化过程的影响,定量评价了建坝后残留咸水楔长度和总残留盐分的动态变化。研究结果表明,随着海水温度升高,淡化过程时间显著缩短。相对于等温条件下的淡化过程,非等温条件下淡化过程的最大特点是热效应引起密度和低浓度混合区(LCMZ)渗透系数发生变化。LCMZ中流速对地下水淡化过程耗时至关重要。

Widespread use of subsurface dams as an effective control mechanism may hinder the flow of fresh groundwater and the removal of residual saltwater in landward directions.Periodic temperature fluctuations in aquifers and oceans can have an effect on the desalination process used to remove remaining saltwater.However,temperature impacts on residual saltwater removal procedures are poorly known.Based on a field-scale numerical model with groundwater-salt-heat coupling,this work explored the thermal effects on the desalination process and evaluated the dynamics of the remaining saltwater wedge length and the overall residual salt mass.The findings indicated that the length of the desalination process lowers dramatically as seawater temperature rises.Compared to the isothermal desalination process,the most notable differences are the density shift owing to thermal impacts and the difference in hydraulic conductivity between seawater and fresh water.The increase in ocean temperature greatly shortens the time required for the groundwater discharge process to attain equilibrium.The flow velocity in LCMZ is the primary factor affecting the time necessary to reach dynamic equilibrium.