Size-fractionation of airborne particulate matter: chemical properties, distribution and health risk assessment – a one year study in Slovenia, Central Europe

The behavior and toxicity of particulate matter (PM) is primarily influenced by particle size and chemical composition, with fine (PM_2.5) and ultrafine particles (PM_0.1) posing the greatest health risks due to their deep respiratory penetration ability and enhanced adsorption capacity. While most studies focus on a single pollutant type – either organic or inorganic − using high-volume air samplers positioned far from areas commonly used by local commuters (e.g. rooftops), data on the multi-pollutant chemical composition of nanoparticles (PM₁ or smaller) and their impacts on active commuters in urban environments remains scarce. A ground-level sampling device utilising a low-volume cascade system was employed to collect and fractionate PM-bound metal(oid)s and polycyclic aromatic hydrocarbons (PAHs), including in nanoparticles, over the course of one year in five urban areas across Slovenia, Europe. In the collected samples, metal(oid)s and PAHs were determined by inductively coupled plasma mass spectrometry following microwave-assisted acid digestion, and gas chromatography mass spectrometry after solvent extraction with mechanical shaking. The highest concentrations of metal(oid)s were predominantly found in PM₁₀ (As, Cr, Ni, Pb) and PM_<0.1 (Cd, Pd, Pt, Sb) fraction. High-molecular weight PAHs (BaA, BaP, BbF, BghiP, Ch, IP) were more abundant in PM₁₀, while low-molecular weight PAHs (Fl, Na, Pa, P) were more prevalent in finer fractions. The highest concentrations of pollutants across all fractions and locations were consistently observed during the winter months. The contaminants investigated primarily originated from anthropogenic activities, particularly those associated with traffic emissions and biomass burning. Given that pollutants bound to the smallest airborne particles are the most harmful, it is essential to enhance pollution control measures and risk assessment strategies by addressing various PM fractions, including nano-sized particles.