Shallow Groundwater Hydrochemical Facies, Nitrate Sources and Potential Health Risks in Southern Baoding of North China Using Hydrochemistry and Positive Matrix Factorization

Nitrate pollution in aquatic ecosystems has garnered growing attention globally, with particular severity in typical agricultural regions of North China. A typical agricultural area of southern Baoding, North China, is selected as the study area. To address key research questions, hydrochemical analysis is used to characterize the shallow groundwater’s hydrochemical properties, Positive Matrix Factorization (PMF) is utilized to delineate the genetic mechanism of high-nitrate groundwater, and Human Health Risk Assessment (HHRA) is conducted to evaluate potential health risks. Groundwater in the study area is predominantly characterized by the HCO3-Ca and HCO3-Mg. Four key factors regulating hydrochemical characteristics are identified via PMF modeling integrated with Pearson correlation analysis. Specifically, Factor 1 (NO3−-dominated) and Factor 4 (SO42−-dominated) are associated with agricultural and livestock activities. In contrast, Factor 2 (Na+- and Mg2+-dominated) stems from the dissolution of silicate or carbonate rocks, while Factor 3 (pH- and K+-governed) is affected by silicate rock weathering and dissolution. The NO3− concentrations in groundwater range from 0.2 mg/L to 68.0 mg/L, with 47.54% of samples exceeding 10 mg/L. NO3− in most groundwater samples originates from mixed sources, including agricultural fertilizers, soil organic nitrogen, and manure-sewage. HHRA results demonstrate that via oral ingestion of groundwater, NO3− poses non-carcinogenic health risks to 90%, 83%, and 82% of children, adult females, and adult males, respectively. This study provides a hydrogeochemical perspective on nitrogen pollution in groundwater and offers scientific support for sustainable groundwater management in typical agricultural regions worldwide.