Saline groundwater evolution in the Luanhe River delta (China) during the Holocene: hydrochemical, isotopic, and sedimentary evidence

Abstract. Since the Quaternary Period, paleo-seawater intrusions have been suggested to explain observed saline groundwater that extends far inland in coastal zones. The Luanhe River delta (northwest coast of Bohai Sea, China) is characterized by distribution saline, brine, brackish, and fresh from coastline inland. this region exhibits a wide range total dissolved solids (TDS): 0.38–125.9 g L−1. Meanwhile, previous studies revealed area was significantly affected Holocene marine transgression. This study used hydrochemical, isotopic, sedimentological methods investigate salinization processes its links paleo-environmental settings. Isotopic results (2H, 18O, 14C) allowed old recharge be distinguished new recharge. Hydrochemical analysis using PHREEQC code indicated salt brine originates source. 18O–Cl relationship diagram yields three-end-member mixing, two mixing scenarios are freshening area. When interpreted along with data sediments, we found may occurred since radiocarbon activities ∼ 50–85 pMC relatively depleted stable isotopes, which associated seawater evaporation ancient lagoon during progradation deeper groundwater, probably recharged cold Late Pleistocene. brackish groundwaters river-like isotope values, where high (74.3–105.9 pMC) were formed after washing out salinized aquifer surface water plain. presents an approach utilizes geochemical indicator paleo-geographic reconstruction better assess evolutionary patterns aquifers.