Drain water of Tyrnyauz deposit during and after operation

Abstract

High-mountain Tyrnyauz deposit of tungsten–molybdenum ore is unique in many respects, including its complicated hypsometry. The latter governs watering of the deposit and large-scale migration of manmade substances in gravity, air and water flows. Different geneses groundwater enters underground openings in Molibden mine. The first kind groundwater is water of infiltration from the upper lying hydrogeological zone; this water features low mineralization (to 0.4 g/l) and mostly hydrocarbonate–calcium composition. The second kind is groundwater from the lower lying hydrogeological zone; this water features high gas content (as a rule, more than 500 ml/l) and carbon dioxide or carbon dioxide–nitrogen composition. Such water contains hydrocabonate–chloride or seldom chloride–hydrocarbonate anions; cations are mostly sodium; mineralization varies in the range of 2–12 g/l. The major factors to govern chemical composition of drain water at the stage of mine operation are mixing of groundwater of the indicated genetic types, oxidation of fine ore, presence of oil products from operating self-propelling machines, as well as nitrogen compounds due to use of explosives in production processes. As a result, drain effluents have out-of-limit concentrations of ore parent metals, oil products and nitrogen compounds. Such effluents were discharged untreated to local hydrogeographic network. At the post-operation stage, drain water remains one of the key pollutant factors to the environment; it also contains out-of-limit concentrations of heavy metals though much lower concentrations of oil products and nitrogen compounds. The aim of this study is to reveal the governing factors of drain water composition during and after mineral mining, to demonstrate the high ecological risk due to such drain water discharge to hydrogeographic network and, thereby, to prove the critical need of drain water localization and treatment using advanced techniques.