Hg concentration was studied in waters of 16 lakes in the Suwałki Landscape Park. The samples of lake water were collected from the surface zone and I m above the bottom, in the deepest site of the lakes. Apart from Hg concentration, the measurements included: the pH, soluble oxygen, water saturation with oxygen, electrolytic conductivity and total hardness of water. Hg concentration varied from lake to lake, but remained at the same levels in consecutive years. It has been found that Hg concentration in the bottom zone is higher than that in the surface zone. Significant differences were found between mean Hg concentrations in the bottom zone both during the summer and winter stagnation. No significant differences were found in mean Hg concentration in surface waters in different seasons of the year.

The study was conducted on the Biała Lądecka River which is a mountain river. It is similar to many European mountain rivers in terms of hydromorphology and catchment management. The aim of this study was to determine the bioconcentration factors of heavy metals (Pb, Cd, Hg, Ni, Cr, Cu and Zn) in Ranunculus aquatile (L.) Dumort., Fontinalis antipyretica (L. ex Hedw.), and Lemanea fluviatilis (L.) C.Ag. The content of metals in water, sediment, and submerged plants was determined. The metal concentrations in plants can be arranged as follows: Hg < Cd < Cr < Ni < Cu < Pb <Zn. The highest concentrations of Hg, Ni, Cr, and Cu were observed in F. antipyretica, but the highest concentrations of Pb, Cd, and Zn were in R. aquatile. L. fluviatilis always contained the least amounts of heavy metals. Bioconcentration factors (BCFs) were lowest in L. fluviatilis and highest in F. antipyretica. Among the analyzed metals, plants accumulated the highest amount of Zn, and the least of Hg. The BCFs for Zn were from 24111 (in L. fluviatilis) to 97574 (in R. aquatile), and BCFs for Hg were from 29 (in L. fluviatilis) to 226 (in F. antipyretica).