Polycyclic Aromatic Hydrocarbons (PAHs) in Forest Floors of the Northern Czech Mountains

Abstract

AbstractForests of the Northern Czech mountains decline due to industrial emissions. To examine the state of soil contamination with PAHs we analyzed the concentrations of 20 PAHs in the O and A horizons of 4 lower and 4 upper slope sites under beech (Fagus sylvatica L.) in the Western (WE) and the Eastern Erzgebirge (EE, Krušné Hory), the Isergebirge (IS, Jizerské Hory), and the Riesengebirge (RI, Krkonoše) at microsites affected and not affected by stem flow. Average PAH sum concentrations in the organic layers ranged between 2000 and 30000 μg kg−1 increasing in the line WE <RI<EE<IS. PAH concentrations were significantly higher at upper than at lower slope sites indicating long‐distance transport. Microsites affected by stem flow had significantly higher PAH concentrations but lower percentages of lower molecular PAHs than microsites not affected by stem flow. This was due to the water collecting effect of the beech bark. Lower molecular PAHs preferentially were sorbed to the bark or leached from the organic layers. PAH concentrations increased from Oi to Oa horizons but decreased in the mineral soil. This was the more pronounced the higher the molecular weight was. The slope of the regression line between the enrichment factors (concentration of a single PAH in the Oa divided by that in the Oi horizon) and the octanol‐water partition coefficient decreased as the PAH concentration of the soils increased. This indicates that the microbial activity of organic layers may be reduced by soil contamination. Cluster analysis suggested that the sources of the PAH contamination in the WE were different from the other sites.