The mobility of chemical elements during the transition from molybdenum ore processing waste to aqueous solutions and the hydrochemical anomalies of a number of elements in surface and underground waters in the vicinity of an abandoned tailings dump were investigated. It is shown that alkaline and alkaline earth metals have high mobility—the main rock-forming components (sodium, lithium, magnesium, strontium), which are released into solution due to leaching from the minerals of the host rocks, as well as metals with zinc, cadmium, manganese, and nickel, which are released into solution due to the dissolution of ore sulfides. Elements with high mobility include Sb, Co, Cu, Be, Se, and Tl. Medium mobility has As, an element of the first hazard class, as well as Mo, Fe, and Pb. Hydrochemical anomalies of cadmium, arsenic, molybdenum, and lead have been determined. The nature of the arsenic and molybdenum anomalies is most likely related to the regional background, while the source of cadmium and lead is most likely the waste studied. The main chemical forms of the presence of elements in the solution of ponds on the surface of tailings ponds are free-ion and sulfate complexes. For example, in the samples of the Shakhtama River and groundwater, we found carbonate, bicarbonate, and hydroxide complexes. The information obtained should be taken into account when planning measures for the purification of surface and groundwater from metals. Additional studies should consider using groundwater in the vicinity of the tailings for drinking water supply.

The ecological state of the Pyasina river basin was assessed by the microbiological and chemical composition of surface waters. The waters of the Bezymyanny (Nadezhdinsky) stream, the Daldykan, Ambarnaya, Pyasina, Dudypta and Tareya rivers, Pyasinsky lakes were studied. The content of oil products, sulfate ions, copper, nickel, iron and manganese in water was identfied. The microbiological composition of waters was analyzed and saprophytes, oligotrophic plants, bacteria oxidizing individual hydrocarbons and oil were isolated. It is shown that the aquatic ecosystems of the Norilsk industrial region are exposed to technogenic impact with subsequent local anomalies in pollutant concentrations. The ecological state of the studied reservoirs was determined by the number of saprophytic bacteria.

The relevance of the research consists in obtaining data on the processes occurring in the sulfide mine waste, their transformation under the influence of oxidative factors, migration of toxic components into the environment. The main aim of the research is to determine the vertical zoning by elemental composition and content of gases (carbon disulfide and dimethyl sulfide) in the tailings, as well as to establish the hydrochemical anomalies in the nearest river as a result of migration of potentially toxic elements with water flows from the tailings. Object of the research is the abandoned tailings dump of the Salair mining and processing plant - Talmovskie Peski (Salair, Kemerovo region), containing wastes of cyanidation and flotation of barite-polymetallic ores. Methods. In the field, thermometry, gas analysis, electric exploration by the resistance method in the electrotomography mode were carried out. Solid and liquid sampling was carried out in accordance with generally accepted techniques. The laboratory study of the chemical composition was carried out by the methods of conductometry, potentiometry, capillary electrophoresis, and mass spectrometry with inductively coupled plasma. Results. The vertical distribution of the total element concentrations is determined by the heterogeneity of the stored tailings material. Using the example of two cross sections to a depth of 1,2 m, it was determined that the humidity of the substance increases with depth, and the temperature, pH pastes and aqueous extracts decrease. With depth, the amount of water-soluble species of metals increases due to the transformation of sulfides in acidic conditions, as well as due to the inflow from the upper horizons. The gas generation of carbon disulfide and dimethyl sulfide increases towards the upper layers of the tailings, which is due to the both transformation of minerals, and active functioning of biota in the upper heated layers with a neutral reaction of the medium. As a result of active tailings-water-gas interactions, contrasting hydrochemical anomalies with high metal concentrations are formed in the Malaya Talmovaya River, in the channel of which the tailing dump is located.

Geochemical and geophysical investigations were performed in an area of the Darasun ore cyanidation tailings impoundment, which is located in a permafrost region. The tailings contain up to 40 wt% pyrite and 5.7 wt% arsenopyrite. The purpose of this work was to determine the composition and mechanisms of transformation of the tailings and species of As, Au, Ag, Be, and Tl in drainage waters and the Darasun River before and after mixing with technogenic flows from the mining area. When the waste is oxidized because of the repeated seasonal freezing and thawing of water, three groups of chemical elements are leached: typical ore metals and impurity elements (Pb–Co–Ni–Zn–Cd and Fe–Al–Tl–Be–In), noble metals, metalloids (Au–Ag–Cu–As–Sb–Se), and post-transition metals and metalloids (Bi–Sn–Te). Drainage waters with salinities up to 5 g/L form, with concentrations of sulfate ions up to 2 g/L and cyanide up to 4 g/L, high concentrations of Au (up to 130 µg/L), Ag (3.8 µg/L), As (up to 350 µg/L), and Sb (up to 1100 µg/L), and impurity elements (Tl, In, Be, and Bi). The drainage water flows into the Darasun River, resulting in hydrochemical anomalies tens of kilometers downstream.

The article shows the results of the analysis of surface water reservoirs and streams in the zone of influence of the Norilsk industrial region. Comparison of data on territories heavily exposed to technogenic impact and conditionally background areas. Comparisons of the obtained values with published scientific information on the studied region are made.

Mine tailings are a very active system in which the processes of oxidation, dissolution, and the re-deposition of substances occur in real-time. Time-lapse electrical resistivity tomography and soil-gas measurements have been used on abandoned mine tailings under a highly continental climate, Western Siberia, Russia. The electrical resistivity tomography method allows the structure of the tailings to be determined, namely, its electrophysical parameters, which are related to the chemical composition and geochemical characteristics of the subsurface substance. The aim of this work is to determine the variations in the geoelectrical zoning of sulfide-bearing mine tailings depending on fluctuations in environmental conditions, i.e., ground and air temperature, in conjunction with volatile compounds of environmental concern emanating from the tailings (SO 2 , CS 2 , C 2 H 6 S). The hourly observations revealed that the configuration of the geoelectrical section varies during the day. The concentration of gases in the surface air layer varied in accordance with the ambient temperature conditions. In general, the minimum gas concentrations were determined at night, and the increase in gas concentrations began when the temperature increased. The dependence of gas formation on temperature conditions differed during the daytime and nighttime. In warmer hours, gas concentrations are highest. At night, when there was a decrease in the temperature of air and then in the ground temperature, a local increase in the concentration of all measured gases occurred at the maximum temperature difference in the air (14.1 °C), and the ground remained relatively warm (20.8 °C). There is a close relationship between ground temperature, electrical resistivity, and the rate of gas production. Local anomalies with the greatest variation in electrical resistivity are associated with the zones that have the most active gas emanations.

In this study, the risk of environmental pollution by arsenic (As) and heavy metals from the tailings of Co-Ni arsenide ores at the Khovu-Aksy mine site (Russia) has been systematically evaluated over 20 years. The assessment results indicated that As poses the greatest concern, followed by Cu, Zn, Co, and Ni, among others. This article presents the results of a study on the mobile forms of metals (Cu, Ni, and Co, among others) and metalloids (e.g., As and Sb) in stored waste that was produced by the hydrometallurgical processing of Cu-Co-Ni arsenide ore from the Khovu-Aksy deposit. A comparative assessment of the changes in element forms during the 20-year of waste storage period was conducted. It was determined that in the pore solutions, the metal concentration decreased by an average of 7-10 times because they precipitated into secondary solid phases or were adsorbed on sulfides. Moreover, the As concentrations in the pore solutions remained practically unchanged, and in some cases, they slightly increased, i.e., this element remained immobile. In contrast, greater changes occurred in the fractional composition of the element forms, which were determined based on the compositions in water extracts. The concentrations of the water-soluble forms of the metals decreased by 100-700 times in 20 years. The concentrations of the soluble As compounds decreased by 1.6-4.6 times. A study of the mineralogy of the tailings showed that the secondary rims of the Fe hydroxides and Ca carbonates with admixtures of Cu, Zn, Co, Ni, and Ag formed on the grains of the sulfide and arsenide grains. The secondary As compounds on the rims are represented by aqueous Fe arsenate. The obtained data indicate active processes of metal deposition, while As remained mobile. The internal structure and geometries of the groundwater horizons were determined by using electrical resistivity tomography, which made it possible to calculate the quantities of dissolved metals and metalloids in the tailings. Condensates were collected to determine the concentrations of the volatile forms of the elements, and the amounts migrating with the vapor-gas flows were estimated. At present, the tailings contain similar to 2.1 tons of dissolved As (in pore water), similar to 85 tons of soluble As (in water-soluble forms), and similar to 23 kg of volatile As that enters the air with vapor-gas flows during summer.

: The article presents the results of a study of the vertical zoning of the old tailings of the Salair GOK Talmovskiy Sands, containing cyanidation and flotation waste of barite-polymetallic ores. The vertical distribution of the total element concentrations is determined by the heterogeneity of the stored tailings material. Using the example of two cross sections to a depth of 1.2 m, it was determined that the humidity of the substance increases with depth, and the temperature, pH pastes and aqueous extracts decrease. With depth, the amount of water-soluble species of metals increases due to the transformation of sulfides in acidic conditions, as well as due to the inflow from the upper horizons. The gas generation of carbon disulfide CS 2 and dimethyl sulfide (CH 3 ) 2 S,

АННОТАЦИЯ: В статье приведены результаты исследования состава поверхностных вод в районе складирования отходов разработки Дарасунского рудного узла.Высокие содержания пирита, арсенопирита, блёклых руд в отходах обуславливают присутствие в потоках рассеяния благородных металлов и мышьяка.В растворенной части поверхностных вод р.Дарасун ниже по течению после складированных отходов и фабрики обнаружен широкий спектр химических элементов, концентрации которых превышают фоновые и кларковые содержания: Cu, Zn, Cd, Pb, Au, Ag, Tl, Be.Элемент первого класса опасности Tl, присутствует в техногенных потоках рассеяния в наиболее токсичной, биодоступной свободноионной форме Tl + .Среди форм бериллия свободные катионы преобладают в техногенных кислых сульфатных водах, а после смешения с природными водоемами основной формой является менее токсичная гидроксидная Be(OH)2 (aq

A study of the environment (water, bottom sediments, soils) in the Arctic territory, previously subjected to anthropogenic impact. Exploration was carried out at the hydrocarbon field, then the wells were liquidated, but the area was not reclaimed. In this study, based on data obtained as a result of expeditionary work, a comparison is made with normative and background contents.

This abstract book contains abstracts of the various research ideas presented at The Second Eurasian RISK-2020 Conference and Symposium.The RISK-2020 Conference and Symposium served as a perfect venue for practitioners, engineers, researchers, scientists, managers and decision-makers from all over the world to exchange ideas and technology about the latest innovation developments dealing with risk minimization.

This abstract book contains abstracts of the various research ideas presented at The Second Eurasian RISK-2020 Conference and Symposium.The RISK-2020 Conference and Symposium served as a perfect venue for practitioners, engineers, researchers, scientists, managers and decision-makers from all over the world to exchange ideas and technology about the latest innovation developments dealing with risk minimization.

The critical environmental situation in the region of southwestern Siberia (Komsomolsk settlement, Kemerovo region) is the result of the intentional displacement of mine tailings with high sulfide concentrations. During storage, ponds of acidic water with incredibly high arsenic (up to 4 g/L) and metals formed on the tailings. The application of chemical methods to treat these extremely toxic waters is implemented: milk of lime Ca(OH)2, sodium sulfide Na2S, and sodium hydroxide NaOH. Field experiments were carried out by sequential adding pre-weighed reagents to the solutions with control of the physicochemical parameters and element concentrations for each solution/reagent ratio. In the experiment with Ca(OH)2, the pH increased to neutral values most slowly, which is contrary to the results from the experiment with NaOH. When neutralizing solutions with NaOH, arsenic-containing phases are formed most actively, arsenate chalcophyllite Cu18Al2(AsO4)4(SO4)3(OH)24·36H2O, a hydrated iron arsenate scorodite, kaatialaite FeAs3O9·8H2O and Mg(H2AsO4)2. A common specificity of the neutralization processes is the rapid precipitation of Fe hydroxides and gypsum, then the reverse release of pollutants under alkaline conditions. The chemistry of the processes is described using thermodynamic modeling. The main species of arsenic in the solutions are iron-arsenate complexes; at the end of the experiments with Ca(OH)2, Na2S, and NaOH, the main species of arsenic is CaAsO4−, the most toxic acid H3AsO3 and AsO43−, respectively. It is recommended that full-scale experiments should use NaOH in the first stages and then Ca(OH)2 for the subsequent neutralization.

This paper demonstrates the results of experiments for the determination of the composition of gases during the dehydration of sulfates (Na-jarosite, melanterite, and chalcanthite) collected at the surface of pyrometallurgical waste heaps. The volatilization of various elements, and vapor–gas phase transport from three sulfate groups were investigated by stepwise laboratory heating at 45, 55, and 65 °C. The sample of yellow efflorescence mainly consisted of Na-jarosite, the white efflorescence contained melanterite as the major mineral, and the blue efflorescence sample consisted of chalcanthite. These all contained a few impurities up to 5 %. The highest total dissolved solids (TDS) was found in the gas condensates from melanterite (59 mg/L), followed by chalcanthite (29 mg/L) and Na-jarosite (17 mg/L). It was determined that major and trace elements in the condensate can be trapped by water vapor and can migrate with the vapor phase during the desorption and dehydration of hydrous sulfates. X-ray diffractograms showed that Na-jarosite remained stable throughout the temperature range, whilst the separation of melanterite’s structural water occurred at 40 °C, and chalcanthite completely lost two water molecules at 50 °C. The gas condensates contained acetates and formates, which could be the fermentation products of bacterial communities. Some of the strains—Micrococcaceae sp., Bacillus sp., and Microbacteriaceae sp.—were cultivated.