Effect of hydrogeological conditions on groundwater nitrate pollution and human health risk assessment of nitrate in Jiaokou Irrigation District

Nitrate pollution in groundwater and related human health risk assessment are crucial to ensure groundwater quality safety. In this study, the grey water footprint (GWF), DRASTIC model, and human health risk assessment (HHRA) model were used to investigate the status of nitrate pollution, analyze the effect of hydrogeological conditions on groundwater nitrate pollution, and evaluate the human health risk of nitrate in the Jiaokou Irrigation District, China. The results show that the maximum and average NO₃⁻ concentrations in the Jiaokou Irrigation District were 895 and 170.73 mg/L and the over-standard rate (>20 mg/L) was over 80% (82.09%). High NO₃⁻ concentration was mainly distributed in the cultivated land. The GWF results indicate that the wastewater absorption was insufficient to bear actual pollution in this region, requiring freshwater between 0.1 × 10⁸ m³ and 105.8 × 10⁸ m³ to dilute the nitrate to a safe concentration. The aquifers with high vulnerability levels were observed in the central and eastern parts, which are mainly related to depth to water table (D), net recharge (R), soil media (S), impact of vadose zone (I), and hydraulic conductivity (C). High NO₃⁻ pollution in an area is generally caused by high aquifer vulnerability. Additionally, the human health risk assessment shows that the health risks for pregnant women and breastfeeding women were higher than the health risks for children in the 10–16 years age group and > 16 years of age. This research provides a basis for policy-makers to take appropriate measures for protecting groundwater from nitrate pollution.