Hydrochemistry, quality and potential health risk appraisal of nitrate enriched groundwater in the Nanchong area, southwestern China

Assessments for groundwater quality and potential health risk are significant for better utilization and exploitation. In the present study, seventy groundwater samples were collected from domestic tube wells and public water-supply wells in the Nanchong area, southwestern China. The integration of statistical analysis, ion correlation, geomodelling analysis, entropy water quality index and health risks assessment were compiled in this study. Statistical analysis indicated the cations followed the concentration order as Ca²⁺ > Na⁺ > Mg²⁺ > K⁺, while anions' concentrations were HCO₃⁻ > SO₄²⁻ > Cl⁻ > NO₃⁻ > F⁻ based on Box and Whisker plot. Piper triangle diagram proposed the hydrochemical type was characterized as Ca-HCO₃. Correlations of ions and geomodelling revealed the concentrations of major ions were mainly determined by calcite dissolution and ion exchange process and NO₃⁻ concentrations were controlled by agriculture activities. Entropy water quality index computation demonstrated that 96% of groundwater samples possessed the EWQI values of 29–95, and thus were suitable for drinking purpose. The HITₒₜₐₗ values for 66% groundwater samples exceeded the acceptable limit for non-carcinogenic risk (HI =1) for infants, followed by 41% for children, 37% for adult males, and 30% for adult females. The non-carcinogenic human health risk of different population groups followed the order of infants > children > adult males > adult females. In future, targeted measures for human health risks of NO₃⁻ will focus on the improvements for agricultural activities, including reducing the use of nitrogenous fertilizer, changing irrigation pattern, etc. Our study provides the vital knowledge for groundwater management in the Nanchong and development of the Cheng -Yu Economic Circle.