Groundwater Chemical Characteristics and Salinization Mechanism in the Coastal Plain of the South Bank of Laizhou Bay

Based on 59 groundwater samples which were collected on the south bank of Laizhou Bay, the main ionic ratios analysis and the main ionic Piper three-line diagram was done. The results show that from offshore to nearshore, groundwater hydrochemical is mainly freshwater, brackish water, salt water, and brine. And the ion type transforms from HCO₃-Ca to HCO₃·Cl-Ca, then converted to HCO₃·Cl-Na and further transformed into Cl·HCO₃-Na, then changed to Cl-Na regularity. By calculating some conventional water ion ratios which include Na/CL, K/CL, Ca/CL, SO₄/CL, the hydrogeochemical effects of water-rock interactions, the source of groundwater salinity and the mechanism of groundwater salinization were investigated in this study. The anion-cation exchange reaction in the groundwater of the brackish water transition zone in the northern part of the monitoring section is more obvious than that in the southern underground freshwater. The main hydrogeochemical processes occurring in the brackish water transition zone are the dissolution of minerals (calcite, anhydrite and rock salt), precipitation of gypsum and dissipation of carbon dioxide. And the main cation exchange in this area is Ca-Na exchange.