Polycyclic aromatic hydrocarbon and heavy metal contents in the urban soils in southern Poland

Abstract

In this study, we examined how urban and industrial sprawl has affected the concentrations of polycyclic aromatic hydrocarbons (PAHs) and heavy metals (HMs) in the soils of two towns with different levels of urbanisation and industrial development. The concentrations, sources and spatial distributions of PAHs and Zn, Pb and Cd in the soils of the central, residential and green areas of the second largest town in Poland (Krakow) were compared to similar parameters in analogous areas of Zakopane, a small tourist town. The concentration ranges of the PAHs were much higher in the Krakow (337-59,694 μg kg^-1) than in the Zakopane (55-1180 μg kg^-1) soils. The Krakow soils were also characterised by higher levels of Cd (2.33-4.18 mg kg^-1) and Pb (24.2-82.1 mg kg^-1) than the Zakopane soils, in which the Cd and Pb concentrations amounted to 0.57-2.29 and 17.8-67.8 mg kg^-1, respectively. Positive matrix factorisation (PMF) analysis identified the emission sources of the soil PAHs in both studied towns. In the Krakow soils, the main sources of the PAHs were traffic emissions, petroleum combustion and the steel-industry, while in the Zakopane soils, they were coal and biomass combustion, used for heating houses, followed by vehicle and gasoline emissions. A human health risk assessment, based on the toxic equivalency factors of benzo(a)pyrene (BaP_eq), indicated a low level of PAHs contamination in most of the studied areas. Only in one area in central Krakow the BaP_eq concentration exceeded the permissible value by nine-fold.

Keywords: Heavy metals; PAHs distribution pattern; PAHs sources; PMF analysis; Risk assessment; Urban soils.