Hydrochemical analysis of surface water quality dynamics in the Oskil river

Abstract

Purpose. Hydrochemical analysis of the dynamics of changes in the quality of surface waters of the Oskil River. Methods. Comparison of hydrochemical indicators with norms of maximum permissible concentrations (MPC). To determine the water quality criterion, the MPC for fisheries reservoirs was taken. The general assessment of water quality is determined by the following methods: water pollution index (WPI), modified WPI and specific combinatorial water pollution index (WPI). Results Based on the water pollution index, it was determined that the river corresponds to the category "very clean" to "moderately polluted". The water pollution index of the Oskil River indicates that the upper course corresponds to the II class "clean", but near the city of Kupyansk the water quality deteriorates to the III class "moderately polluted", and further downstream it again becomes the II class "clean".. According to the methodology specific combinatory water pollution index, the river water is rated from "very clean" to "moderately polluted". The pH in the water varied from 6.08 to 9.27. The total water hardness varied between 10.0 and 2.8 mmol/dm3. The oxygen level indicates an acceptable water condition in most areas. Compounds, the concentration of which most often exceeds the MPC for all observation posts, are: chromium 6+, manganese, copper, petroleum products. Other compounds may also exceed the MAC in some posts and observation years, including total iron, sulfates, zinc 2+ , nitrites, cobalt, phenols, and BSC5. Conclusions. Significant variations in the concentrations of chemical elements in different areas were found in the water quality of the Oskil River. Index of water pollution of the Oskil River according to the calculations of the IZV mod. shows that in most cases for all years of observation, the river corresponds to the III class "moderately polluted". The change in the KIZ indicator along the Oskil River shows that the level of pollution of the river is low along its entire length and it mostly remains under the influence of insignificant anthropogenic influence.