The thesis is devoted to the solution of important scientific and practical problem of improving the ecological safety of drinking water supply in settlements within the Dnipro-Donets artesian basin (DDAB) by establishing the factors of ecological and hydrogeological transformation of qualitative composition of buchak-kaniv aquifer (BKA) drinking groundwater during 60 years period of water intakes operation (1960-2020).
The author found that at the investigated water intakes, the deterioration of groundwater quality occurs due to both an increase in the content of chemical elements of deep (mainly) and surface (episodically) genesis. It was determined that the prevailing factor in the groundwater chemical composition formation of BKA at the present stage is natural phenomena activated by the man-made component (expansion of the water intakes network and intensification of water withdrawal on them) and deep hydrogeomigratory processes (upward migration of unconditioned waters through tectonic faults associated with salt diapirs; upward and downward diffusion of mineralized pore fluids of water proofs to the BKA waters).
Characteristic indicators in the BKA water composition (Cl-, F-, Fetotal, Br-, B3+, J-, total mineralization) were traced. A direct positive relationship (Pearson's correlation coefficients r = 0.7-0.9) was found between their content and the amount of total water withdrawal in the zone of tectonic faults influence associated with the Poltava salt diapir.
Dependencies were obtained that made it possible to justify the optimal total water withdrawal at Poltava water intakes: - to stabilize the content of characteristic indicators in the BKA waters composition within the eastern part of the city, where the most intense pollution of these waters is observed (up to 16 thousand m3/day);
- to stabilize the content of characteristic indicators in the BKA waters composition only within the limits of other parts of the city, where less intense pollution of these waters is observed (up to 40 thousand m3/day).
The study of natural mechanism of BKA drinking groundwater enrichment with F-, which belongs to elements of the II hazard class, received further development. The strategically important ecological problem of region was solved – the key role of technogenic component (intensification of water withdrawal, expansion of water intakes network) in the existing tendency to increase the element content in the process of water intakes operation in the region was proved. The geological background content of F- (about 2 mg/dm3) at the beginning of active technogenesis period was determined. Territories with a content of F- that is critical for the health of the population (from 4 to 8 mg/dm3) have been identified, and the possibility of stabilizing its content in the aquifer waters has been proven in order to reduce the morbidity of the population in the research area.
The existing methodological base for assessing the drinking groundwater protection has been improved on basis of rational integration of various indicators characterizing the modern natural and man-made conditions of research area, and the selection of the most representative of them. Due to this, the zones of increased ecological danger of reduction in the BKA groundwater quality by elements of surface and deep genesis have been determined.
Complex systems of territory zoning based on the danger of changing the qualitative composition of waters have been developed using point assessment of these waters protection against two groups of pollutants. A methodical approach to the selection of promising areas for the construction of BKA new water intakes within the central part of DDAB has been developed. Estimated underground water resources with relatively high indicators of drinking quality are 54.5 thousand m3/day, which increases the environmental safety of Poltava city agglomeration population.
Characteristic indicators of qualitative composition of BKA groundwater for systematic hydrogeochemical monitoring at water intakes are proposed. It is recommended to control their content on the basis of general (control of the entire complex of actual elements-pollutants in the zones of water intakes influence) and special (control of general mineralization, Cl-, F-, Fetotal, Br-, B3+, J- at the intersections of the zones of powerful water intakes influence with territories within a radius of 5 km around tectonic faults) monitoring works.
Criteria for assessing the contamination levels of BKA drinking groundwater at Eastern Ukraine water intakes have been developed for effective control of their content during monitoring in conditions of limited funding and increasing efficiency in making management decisions to improve the environmental safety of population drinking water supply.
