This study is based on 63 sets of groundwater samples from the Qian’an Basin to calculate the environmental background values of groundwater, focusing on total dissolved solids (TDS), total hardness, and NO3 ⁻. Mathematical statistical methods were employed to identify and remove outliers. Ion correlation analysis and ratio plots were also used to investigate the chemical composition, formation mechanisms, and background values of the groundwater while analyzing the spatial distribution characteristics of these background values.
The research results showed that the dominant cations in the groundwater were Ca²⁺, followed by Mg²⁺, while the main anions were HCO₃^-and SO₄²⁻. The hydrochemical types were classified as HCO₃-Ca·Mg and HCO₃SO₄-Ca·Mg, indicating that the dissolution of carbonate rocks played a dominant role in controlling the groundwater chemistry. The background value thresholds of total dissolved solids (TDS), total hardness, and NO₃^- were calculated to be 162-729.95 mg/L, 122.05-508.55 mg/L, and 0.002-32.62 mg/L. The background values of TDS and total hardness showed no significant spatial variation overall. In contrast, the background values for NO₃^- were higher and exhibited clear spatial variability, indicating that human activities influenced the groundwater. The study identified the hydrochemical and environmental background characteristics of shallow groundwater in the Qian’an Basin, deepening the understanding of the groundwater quality formation and evolution mechanisms in the region compared to previous studies and providing important support for the sustainable development of regional groundwater.