Changes in the Ecological Status of the Surface Water Body Under Man-Made Conditions

Purpose. Determining the adequacy of a mathematical model for analyzing the prediction of changes in the total anion content in the Dnieper basin. Methods. Statistical analysis and mathematical modeling. Results. A retrospective analysis and mathematical modeling based on samples of control water intake of the Dnieper River within the Basin Water Resources Management at 12 posts for the period from 2010 to 2019 The approach to determining the balance of the pollutant contained in the surface water body, which takes into account its lateral inflow, due to man-made impact and the process of decomposition in the aquatic environment. Accidental change of lateral inflows causes fluctuations of coefficients of disintegration and receipt of polluting substance. The stochastic equation of the balance of matter is derived, on the basis of which the equation for the density distribution of its concentration can be constructed. The solution of the equation showed that the density of the distribution obeys the lognormal distribution law. This approach is used to analyze the time series of the sum of anions in the water of a surface water body. The suitability of the lognormal distribution law is confirmed, and the distribution parameters are found. It was found that for the total content of anions the distribution is split into two lognormal branches, one - for high, the other - for low values. The application of statistical distributions for probabilistic prediction of extreme values ​​of indicators is considered. Conclusions. The probability of exceeding (providing) normative limits is calculated, the possibility of its use for the purposes of hydrochemical rationing is demonstrated. In the future, the proposed approach may be the subject of research on the analysis of time series of other pollutants entering the surface water body, due to man-made load on it.