Abstract:

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.

Key words: the Yellow River Delta, groundwater, hydrochemistry, hydrogen and oxygen stable isotope, salt source