| In this study, a comprehensive analysis was conducted on 522 shallow groundwater samples collected during this work and 749 sample datasets obtained. Based on the topography, hydrogeology, and runoff characteristics of the Jidong Plain, the shallow hydrogeological regions were subdivided into eight statistical units. Using mathematical statistical methods, the characteristic values of the environmental background values of groundwater for 12 inorganic indicators were determined. The results obtained by means of the Piper trilinear diagram method, Gibbs diagram, and ion ratio coefficient method indicate that in the alluvial and diluvial plains, the dominant hydrochemical type is HCO?–Ca, primarily influenced by rock weathering and hydrolysis. In the alluvial and marine plains, the dominant hydrochemical type is Cl–Na, mainly affected by evaporation and concentration. The background values of SO?2?, Cl?, Na?, Ca2?, and Mg2? in the alluvial and marine plains are significantly higher than those in the alluvial and diluvial plains, suggesting that the groundwater in the alluvial and marine plains has slow runoff and weak circulation, which promotes the accumulation of alkali (earth) metal ions such as Na?, Ca2?, and Mg2?, as well as strong acid ions like SO?2? and Cl?. When evaluating the groundwater quality of the study area using the lower limit of the background value range, the results show that the environmental background values of groundwater in most areas of the study area are in good or excellent condition. |
