Organochlorine contaminants in the Vistula Lagoon sedimentation zone as possible source of lagoon recontamination.

The presented results include decade of monitoring of the Vistula Lagoon waters and have been supplemented by the determination of chlorinated compounds, as well as on concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the sedimentation zone. Monitoring of river waters entering the Polish part of the lagoon and the lagoon waters confirmed the presence of plant protection chemical; the largest contributors has lindane (34%) and DDT (21%); the same as for sediments were dominate lindane (19%) and DDT (14%) within pp-DDT isomer dominate (13%). In the lagoon water, PCDD/Fs were determined within a range of 1.5-5.6 ng dm, leading to average toxicity of 0.18 ± 0.13 ng TEQ·dm. In sediments, their concentrations fell within a range of 22.7-405.7 ng kg dw and the average toxicity of the lagoon sediments was set at 5.00 ± 1.98 ng TEQ·kg dw. Both in water and sediments, the greatest share among PCDD/Fs has octa-chlorodibenzodioxin. Due to the hydromorphological conditions of the lagoon, the waters are mixed to the bottom causing the surface layer of sediment to become remobilized-this is suggested as the key factor when it comes to water recontamination and increased access of POPs to marine organisms.