Comparison of selected methods used in the assessment of contamination with heavy metals in littoral sediments of lakes

This study compared selected methods of assessing the pollution in the littoral sediments by heavy metals (Zn, Cu, Pb, Ni and Cd) in 13 lakes of the Borecka Forest. For this purpose, the ecotoxicological criteria (PEL TEL), the geoaccumulation index (I_geo), the contamination factor (CF) and the contamination degree (C_d) were applied. Characteristic values for both Poland (GBP) and the Earth’s crust (GBE) were assumed as the geochemical background. In addition, the organic (TOC) and inorganic (TIC) carbon were determined in the analyzed sediments. Regardless of the method or adopted background value, the highest pollution level was in the littoral sediments of Lake Szwałk Mały and Lake Kacze. This was primarily associated with increased concentrations of Cd (1.25 and 0.64 mg kg⁻¹, respectively), which was considered as “likely to have toxic effects on organisms” (exceeding PEL). Several potential sources of this metal (fertilizers, herbicides, leaky septic tanks, bait fishing, drainage ditches, allochthonous organic matter) were identified. The content of heavy metals in the littoral sediments of other lakes was sufficiently low and they could be considered as basically uncontaminated.