Groundwater monitoring in the area of sulphide copper-nickel deposits of Novokhopersk ore district (Elan site)

Abstract

Introduction: Domestic and drinking water supply of the population of the Novokhopersk district of the Voronezh region is completely based on the use of groundwater. Water supply to the population in the area of location of sulphide copper-nickel deposits (settlements located along the perimeter of licensed areas) is carried out mainly by using wells for the extraction of underground water for household and drinking purposes. The main purpose of groundwater monitoring was to assess their condition and possible change in quality under the influence of geological exploration. Methods and discussion of results: To assess the possible impact of the consequences of exploration work in the areas of the deposit, hydrogeological monitoring was carried out of the Neogene-Quaternary aquifer, which is the main one in the system of domestic drinking water supply of the population. The results of monitoring in the modern period (2021‒2022) indicate that groundwater has increased values of dry residue and hardness, sometimes sulphates, chlorides, and sodium. These values exceed the MPC of regulatory documents. Increased and often high levels of nitrates (54‒350 mg/dm3) are indicative. Sources of various forms of nitrogen compounds (ammonium, nitrites and nitrates) are latrines, fertilizers, unsewered toilets, garbage. In the oxidizing environment of the aeration zone and the zone of water saturation of the soil stratum, the ammonium and nitrite form of nitrogen is quickly oxidized into a stable nitrate form. Elevated concentrations of nitrates lead to the metamorphization of chemical types of groundwater within the territory of settlements, up to the formation of nitrate-containing hydrogeochemical types. Conclusions and recommendations: The performed monitoring studies demonstrated the absence of the impact of exploration work on the quality of groundwater used for water supply to the population. The main factors of technogenic pressure on groundwater are agricultural and domestic factors, reflected as the increase in a number of indicators and these factors are of a local nature.