ECOLOGICAL AND GEOCHEMICAL CHARACTERISTICS OF SHALLOW GROUNDWATER IN SOUTHERN BUG AND SYNIUKHA INTERFLUVE AREA

Abstract

Problem Statement and purpose. The study area encompassing the territory of about 150 km2, in August 2000, was declared as a zone of environmental emergency due to increasing pollution rates in shallow groundwater, in surface water and to health deterioration of the inhabitants of some settlements. Groundwater is widely used by the local population in numerous boreholes for domestic and agricultural purposes. In the zone of environmental emergency there are about 35 anthropogenic objects, such as: industrial and domestic landfills, pesticide and fertilizer storage, various livestock farm complexes, settling tanks, wastewater and solid waste discharges, etc. The insecurity of shallow groundwater, also its location close to the surface and in the lowest parts of the terrain leads to intensive pollution of groundwater. Besides, groundwater in relation to the fractured waters of the Precambrian crystalline rocks, which lie below and are used for drinking water supply, perform the functions of both a protective screen and a source of pollution. In this case, a multifaceted study of shallow groundwater chemical composition and their formation conditions is a priority task of this study for the environmental emergency zone and for the district as a whole. The purpose of this paper to study the chemical composition and to establish the processes and factors controlling the shallow groundwater chemistry in modern and Pleistocene sediments of the Southern Bug and Syniukha interfluve. Data and Methods. A total of 102 water samples were collected from groundwater wells and boreholes and were hydrochemically analyzed for their macrocomponent composition. Groundwater quality geochemical assessment was carried out using statistical methods in combination with conventional graphical methods by examining groundwater in the Boleslavchik village, where they are most polluted. Results. The dominant hydrochemical types of shallow groundwater are SO4- Na, HCO3-Na and mixed SO4-Mg-Na, SO4-Ca-Na types, sometimes NO3-HCO3 and NO3-Cl-Na types. These groundwater types are formed under the influence of natural and anthropogenic factors, such as water-rock interaction, evaporation-crystallization, precipitation and anthropogenic impact. In this case, water-rock interaction processes, such as silicate weathering, carbonate and sulfate dissolution, ion exchange, evaporation-crystallization and anthropogenic impact play major roles. The weathering of feldspars, chlorites and dissolution of calcites, dolomites are the primary sources for Na+, K+, Mg2+, Ca2+ ions, and dissolution of gypsum, sulfide mineralization for SO4 2– ions. High concentrations of Na+, Cl–, SO4 2–, NO3 – in shallow groundwater reflect agricultural activity as the main source of these ions.