黄河三角洲浅层地下水盐分来源及咸化过程研究

黄河三角洲地下水咸化已成为区域最突出的生态环境问题之一。识别地下水补给及盐分来源是有效控制和改善地下水咸化问题的关键。本研究采集了研究区浅层地下水、地表水和海水等不同类型水样,利用离子比、Piper三线图、吉布斯图等方法对八大离子浓度、δD和δ¹⁸O 组成、Br和Sr 浓度等进行地下水补给研究与盐分来源辨析。结果表明:(1)黄河三角洲浅层地下水以总溶解性固体(TDS)为338 g/L的咸水为主,地下水水化学类型较为单一,主要为Cl-Na型。(2)三角洲区域地下水以大气降水补给为主,并且在补给过程中经历了不同程度的蒸发作用的影响,黄河现行流路区域地下水主要来源于河水侧渗补给,但浅层地下水含水层水平渗透性较差限制了黄河侧渗补给范围。(3)海洋是黄河三角洲浅层地下水盐分的主要来源,黄河现行流路区域及近岸地下水盐分来源于海水混合,三角洲北部刁口河等古河道区域地下水盐分主要来源于海相蒸发盐淋滤溶解。

Source of salt and the salinization process of shallow groundwater in the Yellow River Delta

Groundwater salinization is one of the most prominent problems in the ecological environment of the estuary delta. Identifying the recharge sources of groundwater and salt is critical to understand the process of groundwater salinization. To assess groundwater replenishment and distinguish the source of salt in shallow groundwater in the Yellow River Delta, different types of water samples, such as underground water, surface water, and seawater, were collected for this study and the ions ratio, Piper diagram, and Gibbs diagram were employed to analyze the concentration of eight major ions, the composition of D and ¹⁸O, and the concentration of Br and Sr. According to the results, (1) shallow groundwater in the Yellow River Delta is mainly saline water comprising 3 g/L-38 g/L of total dissolved solids (TDS) while groundwater is mainly of the Cl-Na type. (2) Groundwater in the delta region is mainly recharged by atmospheric precipitation, and has experienced varying degrees of evaporation during the recharge. In contrast, groundwater near the banks of the Yellow River is mainly derived from the side seepage recharge, and the poor horizontal permeability of shallow groundwater aquifers limits the scope of lateral seepage replenishment of the Yellow River. (3) The ocean is the main source of shallow groundwater salinity in the Yellow River Delta. The salinity of groundwater near the Yellow River and close to the coast is caused by seawater mixing. The groundwater salinity in ancient river areas, such as the Diaokou River in the north of the delta, is mainly caused by the leaching and dissolution of marine evaporative salts.