Formation of mine drainage in the Far Eastern region and its impact on the ecosphere and public health

The long-term development of the mining industry in the Komsomolsky, Kavalerovsky and Dalnegorsky districts of the Far East of Russia caused origination of large-scale mining technogenic systems. During the period of socalled “perestroika”, mining production in the region was suspended, while mine workings (pits, adits) and tailings dumps were not subjected to any kind of preservation or reclamation. Only the boron and lead-zinc mining sectors in the Dalnegorsk district are currently in operation. The purpose of this paper is to assess the composition of mine waters, reveal the conditions of their formation, the presence of various aqueous species (coordination compounds and ions) of different elements and establish the parameters of precipitation of a number of hypergenic natural and technogenic minerals from these waters. This paper provides the hydrochemical characteristics of mine waters in the mining technogenic systems of tin-sulfide, copper-tin, tin-polymetallic, and polymetallic deposits, indicates the conditions of their formation and describes the adverse impact on the hydrosphere, as well as on human health in these districts. The studies of sulfide oxidation and mine water formation processes were carried out by the method of physicochemical simulation involving the use of the Selektor software package. The Eh-pH parameters of solutions, their composition with respect to stable aqueous species (complex compounds and simple ions), paragenetic associations (paragenesis) of precipitating hypergenic minerals with respect to the primary composition of ores and host rocks were established in a wide temperature range (from -25 to +45 °C). It has been established that the simulated micropore solutions participating in the formation of mine waters exhibit a wide range of Eh-pH parameters: Eh from 0.55 to 1.24 V and pH from 0.3 to 13.8. The technogenic minerals Fe, Cu, Zn, Pb and Sb belonging to oxide and hydroxide, sulphate, and arsenate classes are precipitated from them. Mine waters of high concentration, prior to and after the precipitation of technogenic minerals (weight of which reaches the hundreds of grams), are released into the hydrosphere. The simulated solutions contain all the elements of sulfide ores: Cu, Zn, Pb, Fe, Ag, As, Sb and S, whereas their concentrations in the form of aqueous species reach the tens of grams, while under cryogenic conditions the concentrations are by one or two orders of magnitude higher as a result of ice formation. The forms of migration of the elements depend on the temperature conditions. The negative impact of mine waters on the region hydrosphere and human health was demonstrated. In the districts under consideration, obvious trend of increasing morbidity (for almost all types of diseases) by 2 times both in adults and in children as compared to other Far Eastern regions was revealed. In addition, the morbidity of the child population for almost all the diseases under consideration proved much higher than in adults.