Identifying hidden heavy metal sources in atmospheric dust of mining cities by integrating Cd isotopes and...

Large-scale mining and smelting activities have led to widespread heavy metal contamination in mining cities, with atmospheric dust serving as a key carrier. However, identifying and quantifying metal sources remain challenging due to overlapping pollution sources. This study analyzed heavy metal concentrations, ecological risks, and Cd isotopes in atmospheric road dust from Panzhihua, a major mining city in Southwest China. The results indicate that mining-related metals (V, Cr, Mn, Ni, Co) showed low exceedance rates and ecological risks. In contrast, Cd, a dispersed element in V-Ti magnetite, significantly exceeded background levels and posed the highest risk. The PCA and PMF were first used to constrain potential source categories, followed by Cd isotope analysis for precise quantification. The results revealed vehicular emissions (45 %), coal combustion (29 %), and smelting (26 %) as major Cd sources. Smelting contributions were higher in downwind residential areas (1.5-5 km) due to prevailing southwest winds and thermal uplift. These findings highlight the unexpected dominance of traffic emissions over industrial sources and provide location-specific insights for pollution control. The study underscores the need to address both industrial and non-industrial sources when managing metal pollution in mining cities and offers a transferable approach for complex urban settings.