Abstract: The chemical types, origins and spatiotemporal variations of groundwater were discussed based on the hydrochemical composition and isotopic ratios of hydrogen and oxygen of the waters from 10 springs and wells in the southeastern Liaoning Province. The measurements demonstrated that the TDS of the water samples ranged from 105.38 mg/L to 809.05 mg/L, with main cations of Na⁺, Ca²⁺ and main anions of SO^2-₄, HCO^-₃, and the values of δ¹⁸O and δD were in the ranges of -9.25‰~-7.53‰ and -66.43‰~-54.33‰, respectively. The water samples can be chemically divided into nine types using the Piper classification method. The stable isotopic ratios of H and O indicated that the waters predominantly originated from atmospheric precipitation and small amount of deep fluids. In the area where granite distributed, the atmospheric precipitation became SO₄·HCO₃-Na、 HCO₃-Na or SO₄-Na type water with high F^- concentration through water-rock interaction, which was the typical feature of granite fissure water. The formation of Cl-Ca·Mg type water in Jinzhou due to the influence of carbonate rocks and seawater intrusion. Due to the hydrolysis of feldspar minerals and the ion exchange of clay minerals, Na⁺ and Ca²⁺ are relatively enriched to form HCO₃-Na·Ca type water. The abnormal variations of concentrations of K⁺, Ca²⁺, Mg²⁺ and Cl^- occurred before and after the earthquakes, which was most possibly caused by deep fluids mixing with shallow groundwater enriched in Ca²⁺, Mg²⁺, HCO^-₃. The anomalies of K⁺, Mg²⁺, Ca²⁺, Cl^- concentrations are obviously related to seismic activity. The results favor to geochemical monitoring and prediction for earthquake, as well hydro-environment research in this area.

Key words: Groundwater, Hydrogen and oxygen isotopes, Geochemical characteristics, The southeast Liaoning Province