Concentrations and distribution of some polychlorinated biphenyls žPCBs/ and polycyclic aromatic hydrocarbons žPAHs/ in an ombrotrophic peat bog profile of Switzerland

An efficient method was developed for the analysis of selected PCBs and PAHs in dry peat samples. The method includes a shaking extraction using acetone and hexane followed by the purification of the crude extract by gel permeation chromatography ŽGPC. which turned out to be the key clean-up step. The method was used to determine seven indicator PCBs and 16 EPA-PAHs in individual sections of an ombrotrophic peat core in south-west Switzerland. The maximum concentrations of PCBs Ž19 g Ý 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 Ž2853 g Ý PAHs kg dm. at a depth of 20 25 cm which represents circa 1951 1930. Compared to these maxima, the concentrations of PAHs in the top layer Ž1990 1986. are six times lower, but the decline in PCBs is only 38%. The concentration profiles are generally consistent with known changes in contaminant emissions, and 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.