Metadata: 1. Title of the manuscript: “Geochemical surface-water modification of Khibiny mountain massive with the beginning of a new mining enterprise”

The article assesses the transformation of the chemical composition of surface waters in the southeastern part of the Khibiny mountain massif after the beginning of development of the Oleniy Ruchey apatite-nepheline ore deposit in 2012. The influence of the Oleniy Ruchey Mine was reflected in an increase in water mineralization (by an order of magnitude) and in a change in the ratio between the basic ions in water objects receiving runoff from mines, rock dumps and tailings, compared to watercourses not affected by the mining enterprise’s activities. Natural hydrocarbonate-sodium water composition with a mineralization of 10 mg/l was transformed into nitrate-sodium or sulfate-calcium. The content of nitrogen group compounds in the water of Lake Komarinoe, which receives wastewater from the tailings pond over the ten-year history of the mining and processing plant, has increased by two orders of magnitude, and the nitrate ion is part of the basic ions. The concentrations of other basic ions and mineralization in this lake increased by an order of magnitude, as well as the content of trace elements (Sr, F, Mo), which are part of the main rock-forming minerals of apatite-nepheline deposits. Increased mineralization (up to 260 mg/l), pH value (up to 10) and a modified chemical composition compared to background objects were noted in mine wastewater. They are characterized by a hydrocarbonate-sodium composition with a large proportion of nitrates and sulfates. Mine wastewater contains increased levels of compounds of nutrients, organic matter and a number of microelements (Al, Fe, Sr, Cu, Mn, Zn and Cr). It has been established that geochemical modifications in the quality of surface water have local characteristic and are typical for water objects receiving wastewater from a mining enterprise, in contrast to metallurgical plants, the atmospheric emissions of which have a polluting effect over tens and hundreds km.