Spatiotemporal variations of nitrogen-nitrate in groundwater and health risk in the parts of Mu Us sandy land, NW China

Abstract

Nitrate pollution is a major threat caused by intensive agricultural activities in semi-arid regions. This study focuses on the Da Niudi Gas Field in the Mu Us Sandy Land. Groundwater quality dynamics were assessed through analysis of 100 sampling points from 2012, 2015, and 2022. The maximum concentrations recorded were 476 mg/L for NO-3, 0.26 mg/L for NO-2, and 1.61 mg/L for NHþ4. Principal component analysis (PCA) and correlation analysis reveal that groundwater chemistry is influenced by mineral dissolution, agricultural activities, and wastewater discharge. The Entropy Water Quality Index (EWQI) was used to evaluate groundwater quality, indicating an overall decline with nitrate pollution showing spatial variability. A health risk assessment model was developed to evaluate health risks for local residents. Results show significant health risks from elevated concentrations of NO-3, NO-2, and NOþ4. In 2012, health risks were within acceptable limits, but by 2015, 50% of children and 12.5% of adults exceeded these limits. In 2022, these percentages decreased to 5.36% for children and 1.79% for adults. These findings emphasize the urgent need for measures to reduce nitrate pollution in the area.