Source apportionment and health risks of nitrate pollution in shallow groundwater in the agricultural Northern Xiaoxing' an Mountains region of China

Abstract

Study region

Northern Xiaoxing'an Mountains, a key agricultural region in Northeast China.

Study focus

Groundwater nitrate (NO₃⁻) contamination has become a widespread concern due to agricultural intensification and anthropogenic activities. This study investigated the sources, spatial distribution, and health risks of nitrate pollution using hydrochemical analysis, multivariate statistical methods, and health risk assessment. APCS-MLR (Absolute Principal Component Scores-Multiple Linear Regression) was employed to quantify pollution sources, while Monte Carlo simulation was utilized to assess health risks among different population groups.

New hydrological insights for the region

Groundwater NO₃⁻ concentrations averaged 31.06 mg/L, with 60 % of samples exceeding Class III water quality standards. APCS-MLR identified agricultural activities as the dominant pollution source (64.04 %), followed by domestic sewage (24.14 %), with pollution hotspots concentrated in intensive farming areas. Hydrochemical analysis revealed two predominant groundwater types: Ca-HCO₃ and Ca-Cl(NO₃+SO₄), with the latter associated with anthropogenic contamination. Health risk assessment highlighted infants as the most vulnerable group, with a 95th percentile Hazard Quotient of 2.38, significantly exceeding the safety threshold. Key factors distinguishing agricultural and domestic pollution sources included distinctive correlations between NO₃⁻, Cl⁻, and SO₄²⁻, hydrochemical patterns in Gibbs diagrams, and spatial correspondence with land use. This comprehensive characterization provides a scientific foundation for implementing targeted nitrate management strategies in this agriculturally important region.