Hydrogeochemical features of groundwaters of the Ukrainian shield fractured crystalline rocks on the example of Zhytomyr and Vinnytsia regions

The chemical composition of groundwaters of fractured Precambrian crystalline rocks corresponding to the Ukrainian Shield aquifer system was investigated. Using the ex- ample of surveyed aquifers of the Vinnytsia and Zhytomyr regions, the similarity of the quantitative and qualitative composition of groundwater confined to the same hydrogeological structure is proven, which is due to similar natural conditions of resource formation (geological structure, the chemical composition of water-bearing rocks, rates of water exchange, amount of atmospheric precipitation, etc.). The dominant role of sulfates in the anionic composition of water samples from the aquifer in the fractured zone of crystalline rocks and their weathering crust (Vysokyi Kamin village, Zhytomyr region) was established. For the Zhytomyr region groundwaters, the dynamics of changes over time in such indica- tors of the general chemical composition as total mineralization, Ca, Mg, SO4, and Cl ions were analyzed for 2017-2019. A significant correlation was found between the concentrations of Mg, SO4, and Cl and their normalized indicators by the amount of water intake, which indicates that the content of mineral substances increases in the studied aquifer with an increase in water withdrawal. This is the evidence of the essential role of the anthropogenic factor in the formation of the general chemical composition of these waters. Using the method of mass spectrometry with inductively coupled plasma (ICP-MS), the features of the trace element composition of groundwaters of the Ukrainian Shield fractured crystalline rocks were established. The obtained concentrations of elements were com- pared with normative values of the World Health Organization and biologically significant concentrations. The lack of several essential elements was revealed. The key potential risks for the health of the population, which constantly uses the investigated groundwaters for economic and potable needs, was outlined. Moreover, the high probability of occurrence of microelementoses with regular use of the investigated groundwaters is emphasized, which are associated with a significant deficiency of such vital elements as Cr (in the Vinnytsia region), Mn, Cu, and, especially, Zn, the content of which is critically low. Subsequently, the findings of this study can serve as a basis for carrying out biogeochemical zoning with the selection of relevant taxa (provinces).