Geoecological Characteristics of Lake Seliger

Data of hydrological and hydrochemical observations conducted in August 2000 at Lake Seliger and its major tributaries are presented. The analyzed characteristics included: O₂, H₂S, CH₄, microelements; mineral and organic compounds of P and N, ionic composition components (HCO₃ ^–, Cl^–, Na⁺, K⁺, dry residue, pH; color index, electrical conductivity. Bottom sediment samples were analyzed for microelement concentrations, CH₄, oil hydrocarbons. The influence of the basin on the ecological state of the lake was assessed, and tendencies in the evolution of its ecosystem are analyzed. It is shown that the ecological conditions of the lake has not changed significantly since 1960–1991, however, nutrient concentrations in the lake water was found to increase.     

Spatial and Temporal Variability of Biogenic Elements Flow and Water Quality in a Small River

Regularities of the formation of biogenic elements flow and water quality in the Istra River (downstream of the Istrinskoye Reservoir) and its tributaries are revealed. Temporal variability in water quality parameters is shown to be closely related to fluctuations in the river water abundance, whereas spatial variability is determined by different intensity of anthropogenic load on river watersheds. It was found that the mean annual (for the period of 1991–1995) concentrations of nitrogen and phosphorus mineral compounds do not always meet the requirements of drinking water supply. A method of estimating the environmental state of the main river, taking into account biogenic elements input from its basin is suggested.