The paper presents the results of studies of bottom sediments taken from the southern part of the Bratsk Reservoir. The following analyses have been conducted: trace element analysis, particle-size analysis as well as chemical analysis of water, hydrochloric acid and alkaline extracts for 18 samples of the bottom sediments. The granulometric analysis has identified the predominance of fine silt and silty-clayed sediments. The data on the content of trace elements in the bottom sediments of the Bratsk Reservoir is presented in comparison with their content in the natural environment of the Baikal region; the anomaly ratio was used to characterize the excess for trace elements. The chemical analysis of extracts has showed “saline contamination” of mud (silt), high concentration of carbonates in it, as well as the presence of mobile (free) forms of aluminum oxide. In this research, an attempt was made by using a correlation analysis to evaluate the impact of various physical and chemical characteristics of the bottom sediments, such as the content of clay fraction, organic carbon, carbonates, and water-soluble salts on the accumulation of trace elements.

The chemical composition of the bottom sediment, and more particularly the heavy metals content, reflects human developments and impacts on the catchment and reservoir's natural environment. The bottom sediments of the reservoir retained by the Irkutsk Dam have been analysed. The reservoir is mainly supplied by water from Lake Baikal. The following amounts of heavy metals have been found in the sediment samples analysed: cadmium - below detection threshold (<0.5 ppm), cobalt - from 16 ppm to 23 ppm, chromium - from 104 ppm to 243 ppm, copper - from 21 ppm to 35 ppm, mercury - below detection threshold (<1 ppm), molybdenum - below detection threshold (<2 ppm), nickel - from 44 ppm to 80 ppm, lead - from 13 ppm to 17 ppm and zinc - from 73 ppm to 98 ppm. Cobalt, chromium and nickel contents exceeded the natural geochemical background level. This may indicates anthropogenic impacts on the reservoir's geosystem.

An assessment was carried out of the anthropogenic enrichment of the chemical composition of the bottom sediments of water bodies situated in an area with an urban and industrial character (63.7% of the total area). The endorheic catchments of the water bodies studied are lithologically uniform with sandy formations accounting for more than 90% of the surface area. On the basis of geoaccumulation index values, it was found that the bottom sediments of the water bodies studied were contaminated with the following elements: Cd, Zn, S, As, Pb, Sr, Co, Cr, Cu, Ba, Ni, V, Be, in degrees ranging from moderate to extreme, with lower contamination (or absence of contamination) with the same elements being found in the formations present in the vicinity and in the substrate of the basins of water bodies. It was found that one consequence of the fact that these water bodies are located in urban and industrial areas is that there is anthropogenic enrichment of the chemical composition of bottom sediments with certain basic components (organic matter, Mn, Ca and P compounds) and trace elements: Cd, Zn, Pb, Sb, As, Cu and Co, Br, Ni, S, Be, Cs, Sr, V, Cr, Sc, Ba, U, Ce, Eu and Th, with virtually no enrichment of sediments with the other basic and trace components analysed (La, Rb, K₂O, Nd, Sm, Na₂O, Hf, SiO₂, Zr).

Jezioro Lake is the only natural lake in southern Poland outside mountainous areas to have existed continuously since the Pleistocene. The record of environmental change in the Late Vistulian (Weichselian) and Holocene is preserved in the deposits and landforms around the lake. This paper presents the results of paleogeographical and paleoecological research that emabled us to reconstruct the history of the Jezioro Lake. At the end of the Vistulian period, the outlet of the lake was blocked by a parabolic dune moving in from the west. Limnic sedimentation was evident in the sediment core at all levels from the Holocene, with remains of Cladocera, Chironomidae larvae, and aquatic plants. The lake did not disappear at that time, although its area decreased by a factor of 12 by the end of the period. Paleobotanical research permitted the reconstruction of sequences of plant communities and changes in nutrient status and water level. An initial oligotrophic lake, as indicated by the presence of Isoëtes lacustris L., changed to a eutrophic lake, as indicated by the presence of Potamogeton natans L. and Nuphar sp., then the lake progressed to the present-day dystrophic lake that is surrounded by a swamp. The profile of organic deposits contains a record of environmental change at least since the Younger Dryas in southern Poland.