Hydrogeochemistry of the Ivano-Arakhleisky lakes

The main purpose of the study is to determine the ranges of changes in the hydrochemical parameters of lakes in different climatic phases, as well as to identify the main sources of salts and processes that control the main geochemical parameters of lake water. The hydrogeochemical studies were carried out on the Ivano-Arachlea lakes, performed with a gap of more than 20 years. Chemical and analytical measurements of water samples were performed using generally accepted methods. It is shown that all lakes differ in mor-phometric characteristics, mineralization, chemical composition and pH value of water. According to Ivanov's classification, the studied lakes are divided into medium lakes with a surface area of 10,1-100,0 km² and very small lakes with a surface area of 0,1-1,0 km². Most reservoirs are shallow (about 1-5 m), with the exception of the lake. Arachlei, the average depth of which is 10,2-13,1 m according to Ovchinnikov's classification of water mineralization, three groups of reservoirs are identified: ultra-fresh, fresh and brackish. Ultra-fresh lakes with a mineralization of less than 200 mg/l and a pH of less than 8,2 are the most common in the region. They are mainly represented by the HCO₃-Ca-Mg-Na chemical composition. Freshwater lakes are less common. They are more saline and alkaline, anionic composition represented more often HCO₃^- and SO₄^2- and cation mixed Ca-Mg-Na, changing with the growth of salinity and pH of waters in HCO₃-Na-Mg-Ca, and at a higher salinity to SO₄-Cl-HCO₃-Na. Even rarer are more alkaline brackish lakes. They have an HCO₃-SO₄-Mg-Na-Ca composition that transforms into SO₄-Na as the salinity of the water increases. It is shown that small brackish lakes are more susceptible to change and larger ultra - fresh lakes are less susceptible to change. Variations of the main physical and chemical parameters can be traced both in the interannual context and in the off-season. Changes in the content of CO₂, HCO₃^-, pH and SO₄^2- were found in the depth of reservoirs. According to the number of biogenic elements, the lake is allocated. Arakhley Lake with the highest content of total phosphorus and lake. Large Hutel-Nur with a relatively high concentration of nitrogen. In this case, the dominant compound is the nitrate and ammonium forms. Increased concentrations of heavy metals such as manganese, iron, lead, Nickel, molybdenum, and cadmium are allocated to the lakes Maly Hutel-Nur, Bolshoy Undugun, Maly Undugun, Ivan, Irgen, and Shakshinskoe. In contrast to macro-coupling of micro-components with the main hydrochemical parameters of the medium, salinity and pH of water is absent. The main processes that control the hydrogeochemical diversity of lakes, including water interactions with aluminosilicate rock, sulfate reduction, sulfide oxidation, and evaporative concentration, have been established.

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