Effects of HumanActivities on the Distribution Patternsand Health Risks of Sb, As, Hg, and Se in a Typical Urban River Systemof Southern China

The anthropogenic input of heavy metals and metalloids (metal(loid)s) into aquatic environments is a global concern. Here, we investigated the spatial distributions and health risks of antimony (Sb), mercury (Hg), arsenic (As), and selenium (Se) and their associations with socioeconomic variables in the Qiantang River basin. In river water, Sb decreased from the southern tributaries to the northeastern mainstream, peaking at 25.3 μg L^–1 near industrial zones, whereas As and Hg displayed a gradual increase in urban areas. Industrial and domestic wastewater contributed 86.5% of the total Sb flow in the river. Correlation analysis revealed that Sb concentrations in river water positively correlated with industrial wastewater emissions, while Hg, As, and Se were associated with variables such as population density. Structural equation models further indicated that industrial wastewater emissions directly affected Sb levels, while population density and energy consumption influenced Se levels. Monte Carlo simulations revealed low health risks (HI < 1, CR < 1 × 10^–4), but compared to background areas, residents in urban areas experienced a 69.8% increase in noncarcinogenic risks, while those in industrial areas faced a 277% increase. These findings underscore the link between metal(loid) contamination and socioeconomic factors, providing data for managing metal(loid) contamination in urban river systems.