Effects of increased sodium concentration on the re-distribution of calcium and magnesium in different media in Taihu Lake, China

Taihu Lake, the third largest freshwater lake in China, has experienced rapid salinization in the past decades, however, little is known about its impact on the distribution of base cations (especially Ca and Mg) in the lake environment. In this work, the adsorption-exchange experiment was conducted using the sediment from Taihu Lake mixed with the Na solution with different concentrations. the experimental and the MINTEQ model data was used to quantitatively explain this exchange process and compared with the actual Taihu environment. The datea showed that Taihu exist obvious cation exchange process caused by salinization, and this process could alter on the distribution of Ca and Mg between the water and sediment in the lake, especially in water; i.e., elevated Na concentration can significantly increase Ca and Mg concentration in the solution, with Ca being preferably exchanged over Mg from the sediment, and the reason for this ionic preference could be attributed to the exchange affinity between base cations by MINTEQ.

太湖，中国第三大淡水湖，在过去几十年中经历了快速的盐化过程，然而，关于其对此湖环境中碱土金属离子（尤其是钙和镁）分布的影响知之甚少。在本研究中，通过将太湖沉积物与不同浓度的钠溶液混合，进行了吸附-交换实验。利用实验数据和 MINTEQ 模型数据，对这一交换过程进行了定量解释，并将其与实际的太湖环境进行了比较。数据显示，太湖存在因盐化引起的显著阳离子交换过程，这一过程可能改变湖水中钙和镁在水和沉积物之间的分布，尤其是在水中；即，提高钠浓度可以显著增加溶液中钙和镁的浓度，钙相对于镁优先从沉积物中交换出来，这种离子选择性的原因可归因于 MINTEQ 中碱土金属离子之间的交换亲和力。