Surface horizons of forest soils for the diagnosis of soil environment contamination and toxicity caused by polycyclic aromatic hydrocarbons (PAHs)

Polycyclic aromatic hydrocarbons (PAHs) are persistent organic pollutants that are released into soils primarily from the air, with wet and dry deposition. To assess the contamination of the forest soil environment, soil samples were collected from organic and mineral horizons from three study areas representing a gradient of pollution across Poland (the ‘pollution transect’). The soils examined varied in PAH contents, generally from 124.3 μg·kg-1 dw in the areas deemed to be the background zone to 9165.5 μk·kg-1 dw in industrial areas in the O horizon and from 12.6 μk·kg-1 dw to 4454.6 μk·kg-1 dw in the A horizon. The PAH toxicities oscillated from 20.0–2670.8 μg TEQ·kg-1 dw in the O horizon and from 1.73–694.7 μg TEQ·kg-1 dw in the A horizon. The enrichment factor values point to a more intensive accumulation of PAHs with relatively high molecular weights along the pollution transect. The PAH diagnostic ratio values indicated that the main PAH emission sources were from coal and wood combustion.