山东半岛北部泥质海岸带地下水水化学演化

Hydrochemical evolution of groundwater in muddy coastal zone of the northern Shandong Peninsula

山东半岛北部是中国海(咸)水入侵典型区域之一,沉积环境复杂,地下水质类型多样。该区域多条河流频繁摆动发育河流三角洲,同时受多次海侵海退事件影响,沉积海陆交互相地层,形成了复杂的地下水含水层系统。近几十年来,人类活动过量开采地下水,导致形成了淡水降落漏斗与卤水降落漏斗,改变了局部地下水的水动力条件,对地下水形成演化产生影响。根据研究区沉积背景与含水层分布特征,划分为3个流域、2层地下水。综合运用海洋地质学、环境同位素与水化学方法,分析结果表明,浅层地下水演化过程存在明显的地域差异性,弥河流域与白浪河流域主要接受大气降水补给,漏斗区以Cl-Ca型水为主,处于地下水咸化过程;潍河流域主要接受河水补给,漏斗区以HCO_(3)·Cl-Na型水为主,处于地下水淡化过程。深层地下咸、卤水形成过程主要受混合作用控制,是一个淡水、海水、卤水三端元混合过程。

The northern Shandong Peninsula is one of the typical areas of seawater(saline water)intrusion in China,with complex sedimentary environment and various types of groundwater quality.Influenced by multiple transgressions and regressions,the aquifer system is complicated by the fact that the stratum in study area is composed of cyclic interbedding of unconfined river delta sand bodies and shelf muddy deposits in a high-amplitude sea level change setting.In recent decades,excessive exploitation of groundwater by human activities has resulted in fresh depression cone and brine depression cone,which have changed the hydrodynamic conditions of local groundwater and influenced the formation and evolution of groundwater.Based on the sedimentary background and distribution characteristics of aquifers in the study area,we divided the groundwater into three basins and two layers,on which analysis and discussion were conducted in marine geology,environmental isotopes,and hydrochemistry.Results show that there are obvious regional differences in the evolution of shallow groundwater,Mihe River and Bailang River are mainly recharged by precipitation,and the depression cone is dominated by Cl-Ca water,reflecting groundwater salinization.Weihe River is mainly recharged by runoff,and the depression cone is dominated by HCO3·Cl-Na water,indicating groundwater desalination.Therefore,the formation of saline and brine in deep groundwater of the study area is mainly controlled by mixing among fresh water,seawater,and brine.