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.