Distribution, source apportionment, and non-carcinogenic health risk assessment of nitrate pollution in surface and groundwater of the Yi River Basin, China

Study region: The Yi River Basin, a key agricultural region that has profound historical importance in fostering early Chinese civilization. Study focus: In this study, 34 surface water and 28 groundwater samples were collected to investigate the spatial distribution, sources, and non-carcinogenic health risks of nitrate pollution. The Absolute Principal Component Scores-Multiple Linear Regression (APCS-MLR) model was integrated with the health risk assessment model to quantify source-specific risk contributions. New hydrological insights for the region: Groundwater showed higher nitrate concentrations than surface water, with an increasing trend from upstream to downstream. APCS-MLR analysis identified geological (32.60 %) and agricultural (39.08 %) as the dominant pollution sources in surface water and groundwater, respectively. Health risk assessment indicated that groundwater posed relatively high non-carcinogenic risks, particularly to infants and children. However, this deterministic assessment underestimated the actual risk compared to Monte Carlo simulation. For surface water, while the deterministic risk was acceptable (HI < 1), cumulative risk effects from multiple pollution sources remain a concern. Furthermore, source-specific health risk assessment further confirmed these findings, and identified agricultural activities as the primary risk source, with contributions of 81.15 % in groundwater and 50.25 % in surface water. The integrated assessment framework established in this study provides a valuable reference for balancing cultural heritage preservation with sustainable water management in agricultural areas worldwide.