Features of cathode-anion composition of water in the reservoir subject to anthropogenic contamination

Abstract

The assessment of the ionic composition and water quality in the Troitsky reservoir of Chelyabinsk region (Russia) was given. Water samples were taken from headstream (station 1), central (station 2) and dam (station 3) parts of the reservoir from the average level in spring (May), summer (July), autumn (September) in the period of 2019-2020. It was established that the mineral composition of water and its ecological safety depends on the season of the year and the movement of the water mass from the headstream to the dam. The highest level of ions is found in spring water samples due to flood water ingress, the smallest - in summer and autumn due to their inclusion in biota life processes. Maximum ion levels are present in water samples from the headwaters and decreases during the water movement towards the dam. In terms of metals' index for chromium (VI), manganese (excluding the year of 2019), iron and nickel, water corresponds to the “slightly polluted” category; cadmium and lead — “clean”; aluminum, copper, and zinc - “clean”. By the WPI magnitude regardless of the season of the year and the sampling point, the water belongs to the 3rd quality class “moderately polluted”. Being ampholytes, lead, aluminum, and zinc in water with a weakly alkaline medium reaction increase their reactivity and due to this directly affect not only the concentration of each other, but also the level of iron, nickel, and copper. The variability formation of cathode-anion composition of water in the reservoir based on PCA results is by 86.2% due to the influence of natural and anthropogenic factors. Priority water pollutants (chromium (VI), nickel, manganese) enter the reservoir from specific anthropogenic sources, as evidenced by the ranking of indicators by residual unexplained variance value.