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Processes of Natural Self-Cleaning of Small Watercourses with Increasing Anthropogenic Load in the Dniester River Basin

Hnativ Roman, Cherniuk Volodymyr, Khirivskyi Petro, Kachmar Natalia, Lopotych Natalia, Hnativ Ihor

Journal of Ecological Engineering

2023

Vol. 24, nr 2

12--18

Small river basins are complex self-regulatory systems, as well as indicators of the state of the environment due to the level of anthropogenic pressure. Since any changes in the regime of small rivers are reflected in the entire hydrographic chain, the problem of estimating the anthropogenic load on small rivers of Ukraine is relevant for modern hydrochemistry and hydroecology. The main sources of water pollution are industrial and domestic effluents, which increase the inflow of pesticides, heavy metal ions, etc. Aquatic ecosystems of small rivers are subject to intense mechanical and biochemical effects, and about 80% of pollutants are washed into water bodies. Water bodies located on the territory or near large cities and urban areas are particularly exposed to man-made pollution. In the territory of the Dniester river basin, natural landscapes are maximally preserved in comparison with other regions of Western Ukraine, but in modern conditions we observe an increase in the negative anthropogenic impact on the quality of natural waters. Hydrodynamic barriers or hydrodynamically active areas (HAA) of mountain rivers, which are significantly saturated with oxygen in the water flow, which activates the processes of biochemical and biological self-cleaning of natural waters, are important to increase the efficiency of self-purification processes. Natural biological cleaning of pollutants in small rivers is highly effective due to the overgrowth of aquatic vegetation. The aim of the work was to establish the ability of the aquatic ecosystem of a small river to self-purify on the basis of hydrochemical indicators of water quality. The compliance with sanitary and hygienic requirements of hydrochemical indicators of Kolodnytsia river water of the right tributary of the Dniester was analyzed and possible regularities of their changes were established, as well as the main factors of anthropogenic impact on a small river and the possibility of laboratory modeling of such rivers. It was found that in the Kolodnytsia River the processes of self-cleaning are quite active, which are caused by the hydrological characteristics of the river and the presence of hydrodynamically active areas in the foothills of the basin. Therefore, at present there is no steady excess of pollutants relative to the MPC.

Visualization of River Water Flow in Hydrodynamically Active Areas under Different Flow Regimes

Snitynskyi Volodymyr, Khirivskyi Petro, Hnativ Ihor, Yakhno Oleg, Machuga Oleg, Hnativ Roman

Journal of Ecological Engineering

2021

Vol. 22, nr 9

129--135

It was established that in the territory of the Stryi river basin, the natural landscapes are maximally preserved in comparison with other regions of Western Ukraine, but under modern conditions an increase of negative anthropogenic impact on the quality of natural waters is observed. The hydrodynamic barriers or hydrodynamically active areas (HAA) of mountain rivers, characterized by a significant oxygen saturation of the water flow, which activates the processes of biochemical and biological self-purification of surface waters, are important for the efficiency of self-purification processes. In order to verify the results of theoretical and field research, an existing experimental setup was designed and improved. It provided the conditions for modeling the flow of mountain rivers in accordance with the laws of similarity theory and the principles of hydrodynamic modeling. On the basis of the results of field observations in the foothills of rivers, as well as regulatory and design documentation, the limits of the main operating factors were determined, namely the Freud number, flow depth and flow rate, which are decisive in studying the impact of HAA on flow self-cleaning processes. By changing the length of the tray section, the gullies and the waterfall niche of the real hydrodynamically active section were simulated, on which field experiments on the Tyshivnytsia River were conducted. In the studies, measurements were performed at different flow regimes, which simulated different hydrological parameters. In order to analyze the impact of HAA on self-cleaning processes, the flow was visualized using photography. The change in the structure of a stream of natural waters at passage of HAA was established. The high oxygen saturation of the river waters of the Stryi river basin is caused by the influence of HAA, which contribute to the purification of polluted waters from biological pollutants and other man-made pollutants and form the high quality of water resources in the region. A method of modeling and visualization of mountain rivers in the laboratory was developed.