Concentrations and distribution of some polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) in an ombrotrophic peat bog profile of Switzerland

An efficient method was developed for the analysis of selected PCBs and PAH s in dry peat samples. The method includes a shaking extraction using aceto ne and hexane followed by the purification of the crude extract by gel perm eation chromatography (GPC) which turned out to be the key clean-up step. T he method was used to determine seven indicator PCBs and 16 EPA-PAHs in ind ividual sections of an ombrotrophic peat core in south-west Switzerland. Th e maximum concentrations of PCBs (19 mug Sigma PCBs/kg dm) were found at a peat depth of 10-15 cm which is estimated to correspond to a time period of 1976-1960 whereas the PAH profile showed a maximum (2853 mug Sigma PAHs/kg dm) at a depth of 20-25 cm which represents circa 1951-1930. Compared to t hese maxima, the concentrations of PAHs in the top layer (1990-1986) are si x times lower, but the decline in PCBs is only 38%. The concentration profi les are generally consistent with known changes in contaminant emissions, a nd suggest that more detailed studies of ombrogenic peat bog profiles could be used for detailed reconstructions of the changing atmospheric fluxes of these and other organic contaminants. (C) 2001 Elsevier Science B.V. All r ights reserved.