Hydrochemical characteristics of underground fluid observation wells in Shandong

To explore the hydrochemical characteristics of underground fluid observation wells in the Shandong area, piper diagram and Na-K-Mg triangle diagram methods were used to analyze the hydrochemical types and water-rock chemistry of water samples from 18 underground fluid observation wells in the study area. The results show that the hydrochemical types of underground fluid observation wells in the Shandong area are mainly SO4·Cl-Ca·Mg type, HCO3-Na type, HCO3-Ca·Mg type, and SO4·Cl-Na type. The chemical composition of water is mainly affected by water-rock interaction, rock salt dissolution, ion exchange, and human activities. Hydrogen and oxygen isotope analysis results show that atmospheric precipitation is the main recharge source of fluid wells in this area, and deep water recharge also plays an important role in some observation wells. The research results determine the hydrogeochemical background and well water source of underground fluid wells in the Shandong area and provide the scientific basis for fluid observation environment analysis, seismic monitoring and prediction, and seismic anomaly verification in the area.