Abstract
In 2010–2013, 528 samples of surface sediments were collected from the profundal zone of lakes to determine concentrations of phosphorus, Al, Ca, Fe, K, Mn, Na and S, as well as trace elements (As, Ba, Cd, Co, Cr, Cu, Mo, Ni, Pb, Sn, Sr, Ti, V and Zn) using the ICP-OES method. Additionally, Hg concentration (by the TMA method) and organic carbon concentration (using the coulometric titration method) were also determined. Phosphorus concentration was found to range from 0.005 to 1.925% (0.109% on average). High phosphorus concentrations in sediments were reported in lakes located within and around urban areas, in lakes on which recreation centres and leisure facilities are situated, and in lakes adjoining special protection areas of birds. The phosphorus concentration in sediments shows a clear correlation with the contents of Al, Fe, Mn, S and TOC, which indicates the presence of phosphorus in both organic and inorganic forms. It also correlates with the contents of most of the trace elements examined for this study, including Zn, Hg and Pb. A certain regional variability was found; water sediments of lakes in the Masurian and Pomeranian lakelands, located in the area covered by the Pomeranian phase ice sheet, are characterised by a slightly higher phosphorus concentration compared with those from the Greater Poland Lakeland situated in the area of the Poznań phase glaciation.