Sources, seasonal trends and urban exposure to airborne particulate matter-bound pollutants

Size-fractionated airborne particulate matter was collected over 1 year (2023-2024) at five urban pedestrian and cycling locations in Slovenia. PM₁₀, PM_2.5, PM_0.1 were collected using a low-volume sampler with polytetrafluoroethylene filters, and PM_<0.1 fraction was retained in ultrapure-water. Metal(loid)s and polycyclic aromatic hydrocarbons (PAHs) were determined to assess the potential health and environmental risks. Metal(loid) concentrations were the highest in PM₁₀, with most elevated levels of Zn (7 ng m^-3), Ba (4.5 ng m^-3), Cu (2.8 ng m^-3) and Cr (1.5 ng m^-3). Significant enrichment in PM_<0.1 was observed for Ba, Cu, Ni, Pb and Zn, with Ce-normalised values indicating a strong anthropogenic contribution. Tailpipe tracers were dominant in (ultra)fine PM fractions, while non-exhaust emission markers (Ba, Cu, Zn) strongly correlated with Ce and La in PM₁₀. Among PAHs, BbF (0.05 ng m^-3), BghiP and IP (0.04 ng m^-3) exhibited the highest concentrations. BaP, BghiP and IP were enriched in ultra-fine particles, indicating fresh vehicular combustion emissions. Peak pollutant concentrations occurred during the heating period (HP) and in densely populated, high-traffic cities. Source apportionment revealed a dominance of pyrogenic sources, including: (i) vehicular exhaust emissions from diesel engines (5-6-ring PAHs, Ni, V and Pb), (ii) resuspended mineral dust and non-exhaust traffic particles (Ba, Cu, Zn), and (iii) coal and biomass combustion during HP (4-ring PAHs, Co, Mo, Tl). Incremental lifetime cancer risk for As (2 × 10^-7), Co (1 × 10^-6) and Cr (6 × 10^-6) was minimal. Hazard quotient values were below 1. Children cycling during HP experienced the highest exposure levels. The European PM₁₀ limit values for As (6 ng m^-3), Cd (5 ng m^-3), Pb (500 ng m^-3), Ni (20 ng m^-3) and BaP (1 ng m^-3) were not exceeded.