Health risk assessment of heavy metals based on source analysis and Monte Carlo in the Lijiang River Basin, China

This study investigates the hydrochemical characteristics of surface water in the Lijiang River Basin with complex pollution sources, focusing on tracing the origins and health risks of heavy metals and hydrochemical components. Systematic analysis of 120 surface water samples revealed that the water chemistry predominantly follows the HCO₃-Ca·Mg type, demonstrating the dominant influence of carbonate rock weathering in the basin. Source analysis using the Positive Matrix Factorization (PMF) model indicated dual contamination drivers from natural geological processes and anthropogenic activities, with industrial and agricultural inputs being the most significant contributors. The Comprehensive Environmental Water Quality Index (CEWQI) ranged from 36.14 to 79.62, suggesting that the overall water quality in the study area is good. High-quality water is generally located in the upper and middle reaches of the basin, while the downstream water quality is comparatively poorer. Major pollutants identified include Cd, Fe, Mn, Cu, Al, Hg, and NO₃⁻, based on entropy weight coefficients and standard limits. Monte Carlo risk assessments indicate that Al poses non-carcinogenic risks to both adults and children, whereas Cd presents non-carcinogenic risks specifically to children and significant carcinogenic risks to all populations. Source analysis demonstrated that non-carcinogenic risks predominantly originate from agricultural non-point source pollution, whereas carcinogenic risks correlate closely with endogenous sediment release. These findings provide scientific foundations for targeted water pollution management in river basins, strengthening agricultural surface source control and sediment management is important for safeguarding the health of the population and promoting sustainable regional development.