咸淡水过渡带的多组分离子交换行为研究

Multi-component ion exchange and transport in the seawater—fresh water transitional zone

以大沽河下游海水入侵砂质含水层为研究对象,采集地下淡水、海水和含水介质样品,并测定其组成和性质。通过渗流装置模拟咸淡水驱替过程,测定驱替过程中含水介质的渗透性参数和主要离子的变化规律,并尝试用数值模拟方法定量研究水敏感性影响下的多组分离子交换过程。研究结果表明,海水驱替淡水情况下,Na+能将砂土吸附的Ca2+、Mg2+、K+交换出来,Na+-Ca2+、Na+-K+交换速度很快,而Na+-Mg2+交换反应持续时间较长;在淡水驱替海水的过程中,溶液中的Ca2+、Mg2+将介质吸附的Na+、K+交换出来,但Ca2+-Na+交换起主导作用。含水介质的动力学参数和突破曲线的拐点变化均进一步验证了咸淡过渡带的水敏感性现象,多组分离子的交换行为导致了水敏感现象的发生。

With the sandy aquifer lying in the seawater intrusion area of the Dagu River in Qingdao as the study object, the authors collected groundwater, seawater and the media to evaluate their composition and properties. Through seepage simulation of the process of seawater and fresh-water, the authors determined the regularity of the permeability and the main ions in the course of seawater and fresh-water displacement. Numerical simulation was also employed to study water sensitivity under the influence of ion exchange. The results indicate that, in the process of seawater displacing freshwater, ion exchanges of Na~＋-Ca^（2＋）, Na~＋-Mg^（2＋） and Na~＋-K~＋ take place, with the ion exchange speed of Na~＋-Ca^（2＋） and Na~＋-K~＋ fairly quick but that of Na~＋-Mg^（2＋） relatively slow. During the course of freshwater displacing seawater, Ca^（2＋） and Mg^（2＋） in solution can replace Na~＋ and K~＋ in the media, with Ca^（2＋）- Na~＋ playing the dominant role. The kinetic parameters and the turning point of the breakthrough curve verify the water sensitivity phenomenon in the seawater and fresh-water transitional zone, Multi-component ion exchange leads to the phenomenon of water sensitivity.