Abstract: The production and living water of residents in Naozhou Island is mainly groundwater. In recent years, due to large-scale exploitation, groundwater in the region has been polluted to varying degrees. In order to explore the current situation of drinking groundwater source in Naozhou Island, this study comprehensively used mathematical statistics, piper three-line diagram, Gibbs diagram, ion ratio analysis and isotope analysis to study the water quality status, hydrochemical characteristics and genetic mechanism of 46 shallow groundwater points in Naozhou Island. The results show that the groundwater in the study area is generally neutral and weakly acidic. The cations of groundwater are mainly Na+ and Ca2+, and the anions are mainly HCO3- and Cl-. About a quarter of the points are saline water. The hydrochemical types are mainly mixed Cl-Ca·Mg type, Cl-Ca type and HCO3-Na·Ca type. The hydrochemical composition of shallow groundwater in the island is mainly affected by the combined effects of rock weathering and evaporation concentration, and some sites are affected by seawater intrusion.

Key words: Naozhou island; groundwater, hydrochemical characteristics, influencing factor； hydrochemical indicators； environmental isotope； groundwater quality