Home – Home – Jornals – Geography and Natural Resources 2020 number 2

A study is made of the chemical composition of pore water in bottom sediments and water in the upper part of the Bratsk reservoir (BR) at a different distance from anthropogenic sources. Concentrations of HCO , Cl^-, SO₄ , K⁺, Na⁺, Ca²⁺, Mg²⁺ 3 and their oxidation-reduction and acid-alkaline characteristics have been measured in different aquifers of surface and pore water. It was established that the oxidizing medium typical for the water of BR persists only in the upper layer of bottom sedi ments (0.5 cm) and is replaced by the reducing medium throughout the layer of bottom sediments. Basic ions are distributed evenly in the free waters of BR, except for the areas with direct inflow of wastewater. Concentrations of all studied components are considerably higher in pore water of bottom sediments, which is particularly clearly pronounced in zones of intense sedimen tation, i. e. in the zones with the most severe anthropogenic load and the reservoir bay. Differences in the chemical composition 2 of pore water and reservoir water are associated with an abrupt increase in Cl^-, SO₄ ^- and Na⁺ concentrations, which is par ticularly evident in the middle and lower layers of bottom sediments. With the mineralization in the waters of BR averaging 113,2 mg/L, its value in pore water reaches 5012 mg/L. Layer-by-layer analysis of pore water showed a considerable hetero geneity of its chemical composition. The distribution of basic ions in the pore water of bottom sediments is determined by water composition, the magnitude and time of anthropogenic impact, groundwater input, composition of water-bearing rocks, hydro logical regime as well as by processes of early diagenesis.