Urban fugitive dust is a significant contributor to atmospheric PM_2.5 and a potential risk to humans. In 2019, both road dust and construction dust were collected from four cities, including Xi’an, Xianyang, Baoji, and Tongchuan, in Guanzhong Plain, China. Elements, water-soluble ions, and carbonaceous fractions were determined to establish the chemical source profile. High enrichment degrees of Se, Sc, Cl, and Zn in both road dust and construction dust indicated that the industrial system and energy consumption influenced Guanzhong Plain strongly. According to the coefficient of divergence, the two datasets within Xianyang and Tongchuan were similar. Combined with the chemical profile, road dust was affected by more stationary emission sources than construction dust in Xi’an, while biomass burning and vehicle exhaust contributed more to road dust than construction dust in Baoji. Moreover, the health risk of heavy metal was assessed, and corresponding influencing factors were identified. Road dust in all cities showed a non-negligible non-carcinogenic risk for children. Ingestion and inhalation were the main exposure pathways to which As and Co contributed the most, respectively. The land-use regression model revealed that the first-class road in a 100 m radius impacted all high-risk level metals, and the commercial building material and enterprises weakly influenced Co and Pb, respectively.

Solid fuel combustion, while a crucial source of energy in many regions around the world, remains one of the primary contributors to air pollution, with significant implications for human health

Carbon dioxide (CO₂) and methane (CH₄) are important greenhouse gases emitted by vehicles, yet their spatial pattern within urban road networks remains poorly characterized. This study conducts mobile measurements of CO₂ and CH₄ along the 1st Ring Road (mean speed of the monitoring vehicle: 22 km h⁻¹), 2nd Ring Road (22 km h⁻¹), and Ring Expressway (90 km h⁻¹) in Xi’an, China, to investigate their spatial distribution and influencing factors. Average CO₂ and CH₄ concentrations on the three ring roads exhibited a clear decline with increasing distance from the city center. Both CO₂ and CH₄ showed higher concentrations at lower vehicle speeds and at higher traffic volumes, but CH₄ hotspots differed spatially from CO₂ and exhibited weaker dependence on vehicle speed, indicating additional off-road CH₄ sources (e.g., natural gas leaks, nearby livestock farms). In a tunnel case study, CO₂, CH₄, and CO concentrations increased concurrently from entrance to exit, resulting in strong correlations between CH₄ and CO₂ (R² = 0.86) and between CO and CO₂ (R² = 0.66). This produced emission ratios (ΔCH₄/ΔCO₂ = 0.160 ppb ppm⁻¹; ΔCO/ΔCO₂ = 3.151 ppb ppm⁻¹), representative of incomplete combustion under congestion. Our results provide direct observational evidence linking urban traffic dynamics to greenhouse gas emissions and emphasize the need for congestion mitigation to reduce on-road climate-relevant emissions.