The contamination of aquatic sediments by metals is a worldwide phenomenon and its assessment is a fairly complex issue, as numerous factors affect the distribution of particular contaminants in the environment, as well as their bioavailability. Wigry Lake, as the object of this study, is almost a perfect water body for such considerations. It has been well investigated and densely sampled (up to 459 sediment samples). The quantities of seven metals were determined using the atomic absorption spectrometry (AAS) or inductively coupled plasma (ICP)-MS methods, following previous extraction in a microwave oven. The levels of concentration of the examined elements were as follows (min–max (mg·kg⁻¹)): Cd—0.003–3.060; Cr—0.20–22.61; Cu—0.02–59.70; Fe—80–32,857; Mn—18–1698; Pb—7.0–107.5; Zn—3.1–632.1. Significant differences were also registered in terms of particular metal concentrations in different sediment types found at the lake bottom. Five different geochemical backgrounds and sediment quality guidelines implemented in the study enabled a very scrupulous contamination assessment of the lake sediments’ condition, as well as the evaluation of the natural and anthropogenic contribution to the enrichment of examined sediments in metals. Although Wigry Lake is situated in a pristine region, it is still subject to anthropopressure, which seems to be the lowest in respect to Cr and Mn, while the highest in the case of Pb. The chemoecological state of the lake was ultimately assessed as good. The study highlighted the necessity of an integrated approach to the assessment of contamination or pollution in the course of an environmental research.

Purpose The main objective of the study was the determination of the Cd, Cr, Cu, Pb, and Zn distribution in Wigry Lake sediments, as well as the contamination and ecotoxicological risk assessment on the basis of a large data set. Materials and methods Select metal concentrations were determined via AAS or ICP-MS. Contamination assessment was achieved via the implementation of different geochemical background values, selected pollution indices, and by way of comparison with the limit values of the sediment quality guidelines and supported by cartographic methods. Results and discussion Metal concentrations presented in the paper were associated with a specific type of sediment and sedimentation environment. The highest concentrations of metals were found in the fluvial-lacustrine sediment covering the bottom of the bay of eutrophic character. The lowest amounts were found in the lacustrine chalk and clastic sediment present in the littoral parts of the lake, while profundal sediments were more enriched with metals. Studies revealed that the examined metals have mostly natural, but also anthropogenic origin. The assessment of lake sediments, with the use of geochemical background values and different indices, yielded highly diversified results associated with the variability of background values applied in the study. However, ultimately, the Wigry Lake sediments were found to be only slightly contaminated with Cd, Cr, Cu, and Zn, while Pb concentrations were considered to be more disturbing. The potential ecotoxicological risk was assessed as low. Conclusions Particular attention in this study was paid to the significance of the geochemical background values adopted for calculations, which, in the case of Wigry Lake, gave very divergent results. A uniquely large data set facilitated the performance of a thorough analysis of metal distributions in recent lacustrine sediments and highlighted the necessity of using integrated approaches in aquatic ecosystem studies.