The huge reaction surface of mineral substances, the presence of soil solutions and dead organic substances in which significant amounts of metals are selectively concentrated, and the high saturation by microorganisms, mesofauna and roots of higher plants create a complex system of metal transformation in soils [29]. The mobility and accumulation of metals in soils and bottom sediment mainly depend on the absorption capacity, the grain size composition (sandy, clayey and silty particles), the humus content, the acidity and the amount of exchangeable cations and free surfaces for cation exchange. Due to the expressed cationic absorption capacity of the soil, due to the negative charge excess of humic substances, it retains positively charged heavy metal ions very well, and a constant supply, even in small quantities for a long time, can lead to significant accumulation of heavy metals in bottom sediment [28; 29; 30]. The ability of bottom sediment to accumulate toxicants, and their subsequent conversion into forms that are hardly soluble, but accessible to plants and aquatic organisms, is the main threat to ecological conditions from technogenic pollution of water bodies, creating a potential danger to public health [31; 32]. Due to the fact that several heavy metals (Mo; Pd; Au; Ga; In; Tl; Ge; Co) have calcophilic properties, that is, they have a high degree of mobility in the aquatic environment and bottom sediment (soils), they can be non-toxic, low, moderately or highly toxic in aquatic ecosystems [33]. Toxic to aquatic organisms, as a rule, are metals belonging to class B (chalcophilic, i.e., having a high affinity for non-metals of group 6 of the periodic table). These include metals present in natural sulfides in the form of cations Ag; Hg; Cu; Pb; Cd; Bi; Zn; Sb and non-metals present in the form of anions S; Se; Te; As. Chalcophilic properties are also possessed by several elements that are simultaneously assigned to several groups--Mo; Pd; Au; Ga; In; Tl; Ge; Co, etc.--on the scale of complex compounds. Among this class, the most toxic metals are those with the largest ionic radius and the highest degree of polarization and affinity for sulfide ions, and the lowest degree of oxidation and electronegativity, as has been reported by different authors [34; 35; 36; 37; 38]. An additional factor determining the degree of toxicological effects of heavy metals on aquatic organisms is the bioavailability of heavy metals [39; 40; 41]. Moreover, toxicological effects are expressed only when heavy metals are available for them, regardless of the concentration level of these metals in aquatic ecosystems [37; 38; 39; 40; 41; 42; 43]. It is also necessary to take into account the type of water body, i.e., whether it is of natural origin (like) or artificial (reservoir), and the impact of river waters on the ecological conditions of the water body for the assessment of the pollution origin [25; 44; 45]. Accurate assessments of heavy metal pollution of the bottom sediment of water bodies requires the consideration of both natural and anthropogenic factors, as well as the chemical properties of metals (activity, toxicity), their background concentrations in nature (in the lithosphere of the study area) [1; 15], their impact on aquatic organisms and plants (bioaccumulation), and the toxic hazards along the food chain [41]. This work did not consider the chemical activity of metals and their mobility by accumulation in the surface levels of the reservoir bottom sediment, because the lack of data for a long period did not allow the solution of these tasks. In the future, it would be interesting to consider the long-term dynamics of sedimentation-sorption processes occurring in reservoir aquatic ecosystems--not only those of an anthropogenic nature, but also those desorption processes occurring as a result of climate change.