Evaluation of shallow groundwater for drinking purpose based on water quality index and synthetic pollution index in Changchun New District, China

Due to the impact of human agricultural production and climate and environmental changes, the applicability of groundwater for drinking purposes has attracted widespread attention. In order to quantify the hydrochemical characteristics of groundwater in Changchun New District and evaluate its quality for drinking purposes, 53 shallow groundwater samples were collected and analyzed. The results show that groundwater in aquifers in the study area is weakly alkaline. The abundance is in the order Ca²⁺ > Na⁺ > Mg²⁺ for cations, and HCO₃⁻ > Cl⁻ > SO₄²⁻ for anions. Ca-HCO₃•Cl water type dominated the area, constituting about 26.41% of the total samples; Ca-HCO₃ water type constituted about 22.64%; Ca•Na-HCO₃ and Ca•Na-HCO₃•Cl water types constituted 15.09% each, whereas Ca•Na-HCO₃•Cl•SO₄, Ca-HCO₃•Cl•SO₄, and Ca-SO₄•Cl types made up 22.64% each. Correlation analysis (CA) and principal component analyses (PCA) show that rock weathering and dissolution, and human activities are the main reasons affecting the chemical composition of water in Changchun. The high concentrations of Pb, NO₂⁻, Fe, and Mn must be widely concerned and may become the main environmental geological problems in the area. The analysis of water samples based on the water quality index model revealed that about 5.66%, 56.60%, 15.09%, 18.86%, and 3.77% of the shallow groundwater samples were excellent, good, poor, very poor, and unsuitable for drinking purposes, respectively. The analysis of groundwater samples based on the synthetic pollution index model showed that more than 37.74% of the groundwater samples were moderately polluted. The spatial distribution maps of the water quality index and the synthetic pollution index show that most of the shallow groundwater resources in the study area are clean and suitable for drinking, despite the risks of the shallow groundwater in the southeast of the study area.