Effect of forest and agricultural land use on the accumulation of polycyclic aromatic hydrocarbons in relation to soil properties and possible pollution sources

Abstract

This study investigated the effects of forest and agricultural land use on the accumulation of polycyclic aromatic hydrocarbons (PAHs) in relation to the chemical and biochemical properties of soil. The heavy metal content in soil samples was also determined; PAH diagnostic ratios were used to identify pollution emission sources. Soils from the Rybnik Forest District of Poland, which has suffered some of the most intense impacts from industrial PAH emissions in Europe, were investigated. Six 200-m-long transects were designated for the experiment, with samples taken every 50 m. These transects were located across forest, agricultural land, and ecotone zones. The organic C and total N contents, pH, hydrolytic acidity and base cation content of the soil samples were determined, as well as the microbial biomass of C, N and P, the enzymatic activity, and the PAH and heavy metal content. A significant impact of land management on the PAH content of the soil due to the supply of organic matter was confirmed. The forest soils were more contaminated with PAHs than the agricultural soils, with an average PAH content in the forest soils of 565.18 µg·kg−1, almost six times higher than in agricultural soils (91.42 µg·kg−1). In addition, soil biological activity, expressed by enzymatic activity, depended on the amount and quality of the soil organic matter and, to a lesser extent, on the PAHs and heavy metals accumulated in the soils. This study confirmed that organic matter has a significant impact on PAH accumulation and is the main soil component involved in the sorption and ageing of PAHs.