Polycyclic aromatic hydrocarbons accumulation in soil horizons of different temperate forest stands

Abstract

AbstractPollution due to polycyclic aromatic hydrocarbons (PAHs) is a serious environmental issue. The aim of this study was to determine the effect of stand species composition on PAH content. The research covered the stand soils of the Rybnik Forest District, which experiences some of the highest deposition of industrial emissions in Europe. Pine, pine–oak and oak stands growing in the same soil conditions were selected for the study. Samples for further analyses were collected from the organic, humus mineral and mineral soil horizons. The organic C and N concentrations, pH, alkaline cation content, microbiological biomass of C and N, soil enzyme activity, soil organic matter (SOM) fractions and PAH content were determined. The oak stand soils were characterised by the lowest accumulation of PAHs (2936.0 μg kg−1) with high biochemical activity expressed by enzyme activity (dehydrogenases, N‐acetyl‐β‐d‐glucosaminidase, phosphatase) and high microbiological biomass. In contrast, pine stand soils are acidified; hence, SOM decomposition is slowed, resulting in a high accumulation of PAHs (3805.0 μg kg−1). A strong correlation (r = 0.825) between PAH accumulation and SOM free light fraction (fLF) C concentration was noted. The stand species composition plays an important role in shaping the quality and quantity of SOM and soil acidification, which is reflected in the microbial activity and PAH accumulation in forest soils. Such accumulation in forest soils is related to the fractional composition of SOM, which is due to the influence of species composition through the supplied biomass.