Aim of the study:
The aim of the study was to assess the degree of heavy metal pollution in bottom sediments of lakes on the basis of geochemical and ecotoxicological indicators.

Material and methods:
The analysis was conducted for 16 lakes located in the Pojezierze Gnieźnieńskie in central-western Poland. The studied lakes were included in the research program conducted by Inspector of Environmental Protection within the framework of the State Environmental Monitoring.The Contamination Factor (CF), Polution Load Index (PLI) and Metal Pollution Index (MPI) were calculated to assess the level of sediment contamination. Assessment of the potential toxic effects of heavy metals accumulated in bottom sediments were made on the basis of TEC, MEC and PEC values. Cluster analysis (CA) was used to show similarities between lakes in terms of heavy metal concentration in bottom sediments. To identify factors affecting metal content in bottom sediments and potential sources of pollution, the PCA analysis was applied.

Results and conclusions:
The analyses showed a large variation in concent of heavy metals in lakes bottom sediments. The lakes bottom sediments were polluted mostly with lead. High concentrations of lead in individual lakes may cause harmful effects on living organisms. The lowest concentrations of heavy metals were found in the bottom sediments of Kamienieckie Lake and the highest in Ostrówieckie Lake. Cluster analysis allowed to divide the lakes into two groups with similar concentration of heavy metal in bottom sediments. The studies did not allow to clearly expose the factors responsible for determining the heavy metal content in the lakes bottom sediments.