CHARACTERIZATION OF THE CHEMICAL COMPOSITION OF WATER AND THE HYDROCHEMICAL REGIME OF LEFT-BANK TRIBUTARIES OF THE DNIESTER WITHIN TERNOPIL REGION

Abstract

The article is devoted to the study of the chemical composition of water, the hydrochemical regime and water quality of the left-bank tributaries of the Dniester within Ternopil region (Zolota Lypa, Koropets, Strypa, Seret, Nichlava and Zbruch rivers) based on water monitoring data of the State Water Agency of Ukraine (1993-2020). The chemical composition of water was studied according to: main ions and water mineralization; physical and chemical parameters (pH, O2); biogenic substances ((NН4+, NO2–, NO3–, РO43–); trace elements (Cu, Cr); specific pollutants (petroleum products, detergents). It was established that the hydrochemical type of water in most of the studied rivers is calcium bicarbonate. The water of the Nichlava River is calcium bicarbonate-sulfate. The average annual water mineralization of the studied rivers varies from 476 mg/dm3 to 699 mg/dm3. The water of most rivers is moderately fresh in terms of mineralization. The water of the Nichlava River is fresh with high mineralization. The hydrochemical regime of rivers is related to the hydrological regime. The minimum concentrations of the main ions and water mineralization are observed during the summer-autumn mezhenia, which is explained by the precipitation of a significant amount of atmospheric precipitation and the presence of floods during this period. The maximum of these indicators is observed in winter. The hydrochemical regime for biogenic substances, trace elements and specific pollutants is less pronounced. Among biogenic substances, the clearest manifestation of the hydrochemical regime was recorded for nitrates. The minimum concentrations of NO3– are observed in the summer-autumn boundary, when nitrates are consumed for the development of aquatic plants. Nitrates accumulate in the autumn period with the death of aquatic plants, and during the winter period, their maximum average content is observed. The assessment of the water quality of the studied rivers, carried out by analyzing long-term series of observations using the “Hygienic water quality standards of water bodies … (2022), showed that the content of the studied components mainly met the regulatory requirements, with the exception of iron. At the same time, the absence of copper, chromium, petroleum products and detergents in water was recorded in all studied rivers during the observation period in different years (zero values of these components were recorded in 70-90% of samples).