PM_2.5-bound heavy metals are of concern because of their persistence, toxicity, and inhalation-related carcinogenic and noncarcinogenic effects. Concentrations, emission sources, and inhalation health risks of these pollutants were investigated during a winter campaign lasting 42 days in 2025 in Laibin, China. The mean PM_2.5 concentration was 47.6 μg/m³, with nominally higher nighttime levels associated with lower wind speeds and a shallower nocturnal boundary layer. The total concentration of nine measured heavy metals (Zn, Cr, Ni, Pb, V, Cu, Sb, Cd, and Co) averaged 363.0 ng/m³, dominated by Zn, Cr, and Ni. Enrichment factors indicated severe Cd enrichment, significant Ni enrichment, and moderate enrichment of V, Cu, Cr, Pb, and Zn, suggesting anthropogenic influence, especially for Cd and Ni. PMF analysis preliminarily resolved three major sources in the daily run: mixed non-ferrous metal smelting and coal combustion source (43%), traffic (23%), and industrial combustion (34%). In the separate daytime and nighttime runs, industrial combustion was the largest source in both periods, whereas traffic increased at night. Non-carcinogenic hazard index (HI) values were below 1 for all populations (children > adult males > adult females), and carcinogenic risks (CR) slightly exceeded 1 × 10⁻⁴ under winter exposure scenarios, with Cr as the main contributor. These results provide a winter-only baseline; precautionary Cr controls are suggested for winter pollution episodes, and multi-season monitoring is needed for comprehensive air quality strategies.

Metal mining affects an estimated 479,200 km of river channels worldwide, and contaminated sediments threaten aquatic ecosystems and human health long after mining ceases. This study examined 53 surface sediment samples from the Xiaozi River and six tributaries in a historical coal-mining area of Chongqing, southwestern China. As, Cd, Pb, Hg and Cr were evaluated using the geoaccumulation index, potential ecological risk assessment and freshwater sediment quality guidelines; differences among rivers were tested with the Kruskal–Wallis test, and sources were explored using APCS–MLR and PMF. Hg and Cd showed the greatest enrichment (mean geoaccumulation indices 1.19 and 0.35). Hg exceeded the background value at all sites and dominated potential ecological risk, accounting for 93.4% of the maximum risk index (914) in the Xibu River. Cr exceeded the probable effect level at 19 sites, whereas As and Hg showed localized exceedances. Concentrations of As, Cd, Pb and Cr differed significantly among rivers (p < 0.01), whereas those of Hg did not. Both receptor models identified Cr–Pb and As–Cd components, whereas Hg was associated mainly with a separate component. These findings identify Hg as the main management priority, together with tributary-specific monitoring of As, Cd and Cr.