Distribution characteristics and health risks of heavy metals in roadside dust along typical roads in the Guanzhong region

Abstract Yangling District in Xianyang City, Shaanxi Province, China, was selected as a case-study area to investigate traffic-related heavy metals in roadside dust. Three representative road types were considered: the Lianhuo Expressway (expressway), Hedi Road (first-class highway; riverbank road), and the Xibao Line (second-class highway). Dust deposition samples were collected from the road surface and at lateral distances of 0–200 m on both sides. Concentrations of six heavy metals—arsenic (As), nickel (Ni), lead (Pb), chromium (Cr), zinc (Zn), and copper (Cu)—were determined, and their spatial patterns, enrichment characteristics and health risks were evaluated. The Xibao Line exhibited the highest total heavy metal concentration in roadside dust (1399.7 mg·kg −1 ), followed by the Lianhuo Expressway (942.2 mg·kg −1 ) and Hedi Road (364.9 mg·kg −1 ). Zn, Cu and Pb were the dominant pollutants. Enrichment factor analysis indicated strong anthropogenic enrichment of these elements, confirming traffic activities as the main source. Heavy metal concentrations generally decreased exponentially with distance from the road, and exponential decay models with high coefficients of determination (R 2 > 0.9) were established for all six metals, allowing quantitative description of lateral dispersion and the effective impact range. Health risk assessment showed that non-carcinogenic risks to children (hazard index, HI > 1) were unacceptable within 0–100 m of all roads, whereas risks to adults remained below the threshold. Carcinogenic risks (10 −6 –10 −4 ) fell within the commonly accepted range but were not negligible. Pb and Cr were the primary contributors to non-carcinogenic and carcinogenic risks, accounting for about 75% and 94% of total risk, respectively. These findings highlight the need for targeted control of Pb- and Cr-bearing particles, careful planning of sensitive land uses near busy roads, and the designation of roadside buffer zones in urban–rural transition areas.