Linking magnetic susceptibility with polycyclic aromatic hydrocarbon concentrations in urban road dust: a proxy-based...

This study evaluated 57 road dust samples collected in Warsaw, Poland, focusing solely on the < 0.2 mm grain size fraction for the analysis of polycyclic aromatic hydrocarbons (PAHs). The total PAH concentration (∑16PAH) ranged from < LOQ to 12.0 mg/kg (mean = 3.56 mg/kg), with the highest levels observed in areas with dense traffic and limited dispersion of contamination. Acenaphthene (Ace), fluorene (Flu), and phenanthrene (Phe) were the most abundant compounds, while high-molecular-weight PAHs constituted approximately 55.2% of the total PAHs. Diagnostic isomer ratios (e.g., IP/(IP + BghiP)) consistently indicated mainly pyrogenic origins. Magnetic susceptibility (χ), normalized for the proportion of fine particles (χ_WN), was strongly correlated with both total PAHs (r = 0.792, R² = 0.628) and high-molecular-weight PAHs (r = 0.797, R² = 0.635), confirming that χ_WN can serve as a robust proxy as a robust proxy for PAH contamination in road dust. Multivariate analyses revealed distinct contamination patterns and grouped PAHs based on their shared sources and physicochemical properties. An ecological risk assessment (MERM-Q) revealed that most samples fell into the low-risk category. The highest risk values were recorded in the city center, where the traffic intensity exceeded 35,000 vehicles/day. These findings demonstrate the potential of χ_WN as a low-cost, non-destructive screening tool to support more efficient environmental monitoring and optimize the selection of sampling sites for detailed PAH analysis.