POLYCYCLIC AROMATIC-HYDROCARBONS (PAHS) IN FOREST FLOORS OF THE NORTHERN CZECH MOUNTAINS

Forests of the Northern Czech mountains decline due to industrial emis sions. To examine the state of soil contamination with PAHs we analyze d 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, Krusne Hory), the Isergebirge (IS, Jizerske Hory), and the Riesengebirge (RI, Krkonose) at microsites af fected and not affected by stem flow. Average PAH sum concentrations i n the organic layers ranged between 2000 and 30000 mu g kg(-1) increas ing in the line WE <RI<EE<IS. PAH concentrations were significantly hi gher at upper than at lower slope sites indicating long-distance trans port. Microsites affected by stem flow had significantly higher PAH co ncentrations but lower percentages of lower molecular PAHs than micros ites not affected by stem flow. This was due to the water collecting e ffect of the beech bark. Lower molecular PAHs preferentially were sorb ed to the bark or leached from the organic layers. PAH concentrations increased from Oi to Oa horizons but decreased in the mineral soil. Th is was the more pronounced the higher the molecular weight was. The sl ope of the regression line between the enrichment Factors (concentrati on of a single PAH in the Oa divided by that in the Oi horizon) and th e octanol-water partition coefficient decreased as the PAH concentrati on of the soils increased. This indicates that the microbial activity of organic layers may be reduced by soil contamination. Cluster analys is suggested that the sources of the PAH contamination in the WE were different from the other sites.