Cd and Hg present quite different case, as the values of their
Igeo indicate a moderately to highly polluted status of sediments in the Gdańsk Deep, and moderately severe enrichment is observed according to the EF’s values. In the Bornholm Deep, there is moderate enrichment as regard Cd and minor enrichment in the case of Hg. The SE Gotland Basin has to be considered as unpolluted to moderately polluted with Cd and Hg. Taking into account the CF factor, the status of all Navitoclax areas classified with respect to all analyzed metals was moderate, in the 5-class scale and as sub-GES in the MSFD classification system. To assess the aggregated impact of the analyzed metals an average of all indicators was calculated (Table 2), characterizing the assessed area. The obtained results pointed out the Gdańsk Deep to be moderately polluted, with moderate enrichment in heavy metals, while the Bornholm Deep and the SE Gotland Deep turned out to be unpolluted to moderately polluted with minor enrichment of heavy metals in sediments. The obtained classification results,
based on the applied indicators, fall in good agreement, particularly regarding the EF and Igeo. Wider ranges of EF and Igeo values make the classification scheme flexible, while the narrow range of CF values makes the classification more rigorous. The most restrictive is, however, the use of 2-class system recommended by MSFD, as the sub-GES result of classification imposes an obligation of counter measures to be check details undertaken on land, though simultaneously the magnitude of the problem cannot be assessed properly. The area of Gdańsk Deep remains under the most severe anthropogenic pressure among the studied sedimentation basins. Sediments from this region were characterized by the highest heavy metal concentrations, except for Pb – higher concentration of lead was found in SE Gotland Basin before 1880. The substantial, saltatory change in metal concentrations and the resulting EF values were observed in Adenosine triphosphate the Gdańsk Deep after 1979. The maximal metal concentrations here reached 232 mg kg−1 – Zn, 77 mg kg−1 – Pb,
2.04 mg kg−1 – Cd and 0.27 mg kg−1 – Hg; this resulted in enrichment factor values (related to the concentrations in the deepest layer) of 13 in the case of Cd, 10 – Pb and 5 – Hg. This pollution of Gdańsk Deep sediments with heavy metals is directly linked to their input via the fresh water discharge of the Vistula River. The SE Gotland Basin is the area showing the weakest anthropogenic pressure, this being proved by both the actual heavy metal concentrations and the dynamics of their changes. The substantial increase in Cd and Hg accumulation in sediments took place after 1980, and this was even more dynamic than in the Gdańsk Deep. The maximal EF values observed here reached 1.5 in the case of Zn and Pb and about 3 in the case of Cd and Hg.