Sixteen priority polycyclic aromatic hydrocarbons in roadside soils at traffic light intersections (Bratislava, Slovakia): concentrations, sources and influencing factors

Combustion of fossil fuels is the most important source of polycyclic aromatic hydrocarbons (PAHs) in the environment. Cities are typical of many human activities which are dependent on fossil fuels (road and railway transport, heat generation, waste incineration and industry) on a small area, leading to high concentrations of PAHs in urban air, dust and soil. The aim of this study was to determine the possible influence of urban traffic on the accumulation of sixteen priority PAHs in soils ( n = 132 at two soil depths of 0–10 cm and 10–20 cm) taken at intersections ( n = 37) with different traffic volumes and road ages. Variable concentrations of the sum of PAHs (∑ 16 PAH) ranging from 188 to 21,950 μg/kg with a mean and median of 3021 μg/kg and 1930 μg/kg were recorded, respectively. Concentrations of PAHs positively correlated with soil organic carbon content (TOC) ( r Spearman = 0.518; p < 0.001). Statistically significant positive correlations between ∑ 16 PAH concentrations and traffic volume/road age were found in this study ( r Spearman = 0.689/0.619; p < 0.001), while ∑ 16 PAH concentration decreased with increasing distance from the road edge and was statistically lower at a soil depth of 10–20 cm than at 0–10 cm ( p < 0.05). Multivariate statistical methods (principal component analysis and cluster analysis) applied to log-ratio transformed data ( clr ) to decrease the constant sum constraint coupled with positive matrix factorisation (PMF) modelling pointed to the dominance of pyrogenic emission sources, with 62.1% traffic-related (petrol and diesel emissions, liquid fuel and motor oil spills, and tyre wear) according to PMF results.