Geochemistry and formation conditions of the natural water composition in the nothern outskirts of Kazan

Kazan is located on the left bank of the Kuibyshev water reservoir in the east of the Russian Plain. The Blue Lakes, which are unique salt-water karst lakes in the Middle Volga region, appear to be a real natural treasure in the northern outskirts of the city. On the basis of field and analytical data obtained in 2023, the geochemical composition of the natural water is studied in the Blue Lakes, the Solonka and Kazanka rivers, uprising springs, and snow cover. Significant variations in the hydrochemical field are controlled by the effect of discharging relatively deep sulfate calcium groundwater from the lower Permian carbonate-sulfate deposits with a mineralization of about 2.5 g/l. The shares of these artesian waters in the river discharge have been determined. They are about 80% for the mouth of the Solonka River in the initial period of summer low water and about 50–60% for the lower reaches of the Kazanka River in the initial period of winter low water. Maximum values of deep water inflows are observed in river valleys along fracture zones of submeridional and northeastern orientation. The stability of hydrochemical parameters in the studied water bodies over time is shown, which is due to a high rate of water exchange and a low anthropogenic impact on the environment. Complexes of microcomponents concentrated in artesian and near-surface waters have been identified. In artesian waters such components are: Ca, Sr, Mg, Li, U, Re, Se; and in the near-surface – K, Fe, Mn, Ba, As, Co. It is noted that in order to determine the degree of surface water pollution, it is important to take into account the conditions of their composition formation and to distinguish between excess concentrations caused by natural and anthropogenic factors.