Groundwater is one of the key natural resources, so maintaining its high quality is one of the main problems in mining. The aim of the article is to study the dynamics of the level and hydrochemical regime of groundwater in the influence zone of apatite-nepheline ore mining in the southeastern part of the Khibiny alkaline mountain massif. Over the 10-year history of the Oleniy Ruchey Mining and Processing Plant of North-West Phosphorous Company JSC, significant changes in the chemical composition of the studied groundwater of the aquifers of the Upper Quaternary Ostashkov fluvioglacial horizon f,lgQIIIos and Paleozoic intrusions yPz have occurred. The content of the main ions in groundwater increased from 2 to 20 times, nitrates up to 50 times (exceeding the maximum permissible concentrations of 45 mg/l), and NO–3 entered the category of the main ions of groundwater. The source of the main ions and the increase in mineralization in groundwater is the weathering and leaching of the main ore minerals – apatite and its varieties, nepheline, sulphide minerals, as well as the use of explosives containing nitrogen compounds. As a result of this hydrochemical evolution of groundwater, the ratio of the main ions has changed – natural water of hydrocarbonate-sodium composition with neutral pH values has now become hydrocarbonate-calcium, NO–3 are in the second place among anions, and Na+– among cations. In the hydrodynamic regime of groundwater at the Oleniy Ruchey deposit, spring and autumn maximums of groundwater levels are clearly expressed. During a decrease in the level, contaminated more mineralized mine waters are drawn to the wells, and during an increase in the level, low-mineralized waters of atmospheric precipitation infiltrate into the aquifers. A decrease in average annual groundwater levels has been established, which is associated with an increase in the quarry depth and the water intake of groundwater for water supply to the mine.
