Factors determining the accumulation of pentachlorophenol — a precursor of dioxins in bottom sediments of the Gulf of Gdańsk (Baltic Sea)

Pentachlorophenol (PCP) and its derivatives are considered to be the precursors of dioxins, thus their concentrations in environmental compartments remain relatively correlated. Unlimited production and usage of PCP in recent decades may have posed a potential ecological threat to marine ecosystems due to uncontrolled discharge of this contaminant into the Vistula River and finally into the Gulf of Gdańsk. Since there are no data on PCP concentration in sediments of the southern part of the Baltic Sea, the level of contamination has been examined and possible influence of sediment properties in the Gulf of Gdańsk on the accumulation intensification has been investigated. The study has resulted in the evaluation of an efficient analytical procedure characterized by a low detection limit (LOD<1 ng g−1 d.w.). Instrumental analyses have been supplemented with Microtox® bioassay in order to assess the sediment toxicity. The obtained concentrations in collected samples varied from below the LOD in sandy sediments to 179.31 ng g−1 d.w. in silty sediments, exceeding the PNEC value of 25 ng g−1 d.w. (Predicted No Effect Concentration) estimated for the Baltic Sea (Muir & Eduljee 1999). It has been proven that properties of sediments from the Gulf of Gdańsk, including pH, Eh of bottom water, the content of water and organic matter, affect the rate of PCP accumulation. High toxicity has been recorded in the bottom sediments of the Gdańsk Deep but no statistically significant correlation between PCP concentration and the sediment toxicity has been observed. Analysis of PCP concentration distribution in sediment cores revealed that the surface layer is the most polluted one, which indicates a continuous inflow of PCP from the Vistula River. Horizontal PCP distribution in the sediment from the Gdańsk Deep reveals variability similar to that observed for highly chlorinated dioxins (Niemirycz & Jankowska 2011).