Occurrence of perfluorinated organic acids in the North and Baltic Seas. Part 2: distribution in sediments.

Purpose: The distribution of polar perfluorinated compounds (PFCs) in sea water of the North and Baltic Seas has been described in part 1 of this study. In part 2, their occurrence in sediments is described in order to further investigate their distribution routes and possible sinks.

Methods: Sediments were extracted with methanol and PFCs with chain lengths of C(4) to C(10) analysed by liquid chromatography coupled with tandem mass spectrometry.

Results: Using the developed procedure, PFCs could be determined in sediments from all 15 stations which had been sampled. In most samples from the German Bight and western Baltic Sea, perfluorooctane sulphonate had the highest concentrations (0.02 to 2.4 μg/kg dry weight), followed by perfluorooctanoate at 0.06 to 1.6 μg/kg dry weight. Levels of the other PFCs were five to ten times lower. Concentrations of PFCs were similar to those of classical chlorinated hydrocarbons. The spatial distribution is strongly influenced by sediment parameters (e.g. total organic carbon (TOC)). By normalisation to TOC, regional differences were identified between the North and Baltic Sea samples. Sediment/water enrichment ratios estimated from field concentrations showed clear dependences on carbon chain length and chemical structure. Time trends of PFCs, investigated by analysing a sediment core (Skagerrak), differed clearly from those of "classical" pollutants.

Conclusion: Because of the strong influence of sediment parameters and the relatively low enrichment of PFCs in sediments, this matrix is less suited for investigating spatial distributions. Sediments should be used mainly for monitoring temporal trends, preferably using sediment cores.