Geochemical characteristic of springs of the East of Moscow region

The study determined the geochemical characteristics of the spring waters of the Bogorodsky and Losino-Petrovsky districts in the east of Moscow region. The territory located on the Meshchera Lowland, within the development of Devonian, Upper Carboniferous, Upper Jurassic and Lower Cretaceous terrigenous-carbonate rocks, overlain by thin Quaternary sandy deposits.[1] Surface sediments are permeable to precipitation and unregulated technologically polluted surface runoff, which can lead to a decrease in the quality of groundwater, which is actively used by the population as drinking water. This research is the results of evaluated of water parameters (COD, pH, electrical conductivity), the content of major ions (Ca2+, Mg2+, Na+, K+, NH4+, HCO3-, Cl-, SO42-, NO3-) and microelements (Co, Ni, Cu, Zn, Cd, Pb, Sr, Ba, Mn) for 12 springs. The waters are slightly acidic-near-neutral (pH 5.5-7.5) with the mineralization from 0.07 to 0.5 g/l, the total hardness is 0.63-5.7 mg-eq/l, the composition of the water is variable. The spring waters are slightly mineralized (M=0.1-0.5 g/l), pH values vary from 5.5 to 7.5.  The obtained data on the content of main ions make it possible to divide the waters of the studied springs into several groups. Spring waters are divided into four groups: Cl-SO4-HCO3-(Mg)-Ca; (SO4)-HCO3-Cl-Na-Ca; (Cl)-HCO3-Ca; and mixed composition. Elevated concentrations of nitrate ions are consistently observed in water all of springs (averaging 7-9, up to 17% eq). The chemical oxygen demand (COD) averages 2.1 mgO/l, reaching a maximum of 12-18 mgO/l. Based on the thermodynamic calculation using the Visual-MINTEQ, it was found that the predominant migration forms of Ba, Sr, Mn, Zn, Cd, Ni, Co in the waters in the waters of the surveyed springs are free ions. For Cu, Zn and Pb, the factors for the formation of migration forms are the predominant anions of water, as well as the presence of organic matter in water. For Cd an additional factor of formation of migration forms is chloride-anion. COD values and nitrogen compound in the waters of individual springs are indicate that the formation of the composition of spring waters is associated with the infiltration of atmospheric precipitation through the modern sediments subject to anthropogenic press. The values of other sanitary-chemical indicators (mineralization, pH, total hardness, chlorides, sulfates, magnesium, sodium, manganese), the content of standardized microelements are lower than their maximum permissible concentrations in drinking water.   1. Makeev V.M., Sukhanova T.V., Makarova N.V., Korobova I.V. Geological and geomorphological structure and geoecological conditions of Noginsky-Klyazminsky district of Moscow region // Geoecology. Engineering geology. Hydrogeology. Geocryology. - 2019. - N. 4. - P. 68-78. doi: 31857/S0869-78092019468-78