Chemical Treatment of Highly Toxic Acid Mine Drainage at A Gold Mining Site in Southwestern Siberia, Russia

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

Hydrochemical Anomalies in the Vicinity of the Abandoned Molybdenum Ores Processing Tailings in a Permafrost Region (Shahtama, Transbaikal Region)

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

Transfer of chemical elements in vapor-gas streams at the dehydration of secondary sulfates

The elemental composition of vapor-gas streams obtained during heating of secondary hydrous sulfates are presented. Samples of abundant sulfate intergrowth were collected at the Belovo waste heaps and heated at 60ºC in experiments to collect condensates of the releasing vapor-gas streams. A wide spectrum of major and trace elements was determined in the condensate. Chemical elements can be absorbed by the water vapor and migrate with this phase during the dehydration of hydrous sulfates. To determine the mechanisms of migration and the sources of elements in vapor-gas streams, a study of the features of certain hydrous sulphates (antlerite, goslarite, starkeyite, gunningite, siderotile, sideronatrite) by stepwise heating up to 60ºC was conducted. Alteration in the phase composition is controlled by powder X-ray diffractometry. It was determined, that antlerite and starkeite remain stable throughout the temperature range. The beginning of the separation of structural water in goslarite and siderotile occurs at 40°C. Goslarite and sideronatrite at 40°C lost water molecules and transformed to gunningite and Na-jarosite, correspondingly. Structure of siderotile was loosened. The modes of occurrence of the chemical elements in sulfates and pore solution determine the concentrations of elements in the condensates

Results of phytoremediation experiments with sowing oats (Avena sativa) on different types of mine tailings

Актуальность. Повышение концентрации металлов и металлоидов в наземных экосистемах в результате деятельности горнодобывающей и металлургической промышленности является серьезной проблемой для окружающей среды - приводит к накоплению элементов в почвах, дикорастущих и сельскохозяйственных растениях и сопровождает загрязнение компонентов пищевой цепи. Цель: определить и оценить способность овса посевного Avena sativa аккумулировать металлы и металлоиды из вещества хвостохранилищ с разными физико-химическими параметрами для фиторемедиации. Объекты: вещество хвостохранилищ (Дюков лог, Талмовские Пески, Хову-Аксинские) и отвалов (Урской, Белоключевской, Берикульский). Методы. Пробы корней и ростков были проанализированы на содержание широкого круга элементов методом ИСП-МС на масс-спектрометре NexION 300D (PerkinElmer, США) (ПНИЛ ГГХ ИШПР ТПУ). Отбор твердых проб выполнялся в соответствии с общепринятыми методиками. Пробы твёрдого вещества были проанализированы на содержание оксидов силикатной группы методом РФА на рентгенофлуоресцентном спектрометре ARL-9900-XP (Thermo Electron Corporation, Switzerland) в лаборатории рентгеноспектральных методов анализа ИГМ СО РАН, элементный анализ проводился методом ИСП-МС на приборе ELAN-9000 DRC-e, Perkin Elmer, USA (ХАЦ «Плазма»). Результаты. Проведены эксперименты с проращиванием семян однодольного растения - овса посевного (Avena sativa), на субстратах хвостохранилищ (Дюков лог, Талмовские Пески, Хову-Аксинские) и отвалов (Урской, Белоключевской, Берикульский), расположенных в Западной Сибири и республике Тыва. Данное растение относится к списку гостированных тестов фитотоксичности и сидератам, но его развитие на представленных техногенных объектах ранее не изучалось. Впервые показано, что в среднем концентрация металлов и металлоидов в проростках овса превышала концентрацию этих элементов во всех случаях по сравнению с контролем. Оценено влияние кислотности/щелочности техногенных субстратов на извлечение элементов растениями. Показано, что семена овса не взошли в пробах с добавлением вещества, дающего кислую среду (рНБ<2) либо высокую минерализацию жидкой фазы. В веществе отходов с диапазоном рН 2-5 (кислая и слабокислая среда) семена проросли, но масса проростков существенно меньше, чем в веществе с нейтральной-субщелочной средой (рН 6-8). На всхожесть не влияет соотношение алюмосиликаты/пирит, основное значение имеет наличие карбонатов и степень окисленности вещества отходов. В кислой среде, при относительно высоких концентрациях металлов (Fe, Mn, Cu, Zn) в жидкой фазе, их доля, поглощаемая растениями, была существенно ниже, чем в нейтральной-субщелочной среде. На аккумуляцию большинства элементов кислотность среды не оказывала влияния, их накопление в подземных и в надземных частях растений зависело от содержания их растворимых форм. Для мышьяка и висмута прослеживается повышение их содержания в проростках овса с повышением pH водной вытяжки. Влияние концентраций элементов в среде питания растений неоднозначно. Например, для вещества с высоким содержанием подвижных форм Cd, Pb, Zn биомасса и длина корня проростков овса была выше, чем для овса, выращенного на другом веществе. Транслокационный индекс указывает на то, что накопление большинства металлов и металлоидов выше в корнях, чем в надземных частях.The relevance. The increase in concentrations of metals and metalloids in terrestrial ecosystems as a result of the activities of the mining and metallurgical industries is a serious problem for the environment - it leads to the accumulation of elements in soils, wild and agricultural plants and accompanies the pollution of food chains. The main aim of this study is to determine and evaluate the phytoremediation ability of oats Avena sativa to accumulate metals and metalloids from tailings with different physicochemical parameters. Objects of the study are the material of tailings (Dyukov Log, Talmovskiy Sands, Khovu-Aksy) and waste heaps (Ursk, Beloklyuch, Berikul). Methods. Root and shoot samples were analyzed for the content of a wide range of elements by ICP-MS on a NexION 300D mass spectrometer (PerkinElmer, USA) (PNL «Voda» GGC ISHPR TPU). The selection of solid samples was carried out in accordance with generally accepted methods. The solid samples were analyzed for the content of oxides of the silicate group by XRF on an X-ray fluorescence spectrometer ARL-9900-XP (Thermo Electron Corporation) at the Laboratory of X-ray Spectral Analysis Methods of the Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences; analysis of trace elements concentration was carried out by ICP-MS on an ELAN-9000 DRC-e instrument, Perkin Elmer, USA (HAC Plasma). Results. Experiments were carried out with the germination of seeds of a monocotyledonous plant - oats (Avena sativa) on the substrates of tailings located in Western Siberia and the Republic of Tuva. This plant belongs to the list of hosted tests of phytotoxicity and green manure, but its development on the presented technogenic objects has not been studied before. It is shown for the first time that on average, the concentration of metals and metalloids in oat seedlings exceeded the concentration of these elements in all samples compared to the control. The effect of acidity/alkalinity of tailings on the extraction of elements by plants was evaluated. It was shown that oat seeds did not germinate in samples with the addition of a substance that gives an acidic environment (pH<2) or high mineralization of the liquid phase. In the tailings with a pH range of 2-5 (acidic and slightly acidic environments), the seeds germinated, but the mass of seedlings was significantly less than in the material with a neutral-subalkaline environment (pH 6-8). Germination is not affected by the ratio of aluminosilicates minerals/pyrite, the main is the presence of carbonates and the degree of oxidation. In an acidic medium, at relatively high concentrations of metals (Fe, Mn, Cu, Zn) in the liquid phase, their proportion absorbed by plants was significantly lower than in a neutral subalkaline medium. The acidity of the environment did not affect the accumulation of most elements, their accumulation in the underground and aboveground parts depended on the content of their soluble forms. For arsenic and Bi, there is an increase in their content in oat seedlings with an increase in the pH of the aqueous extract. The influence of high concentrations of elements in the plant nutrition environment is ambiguous. For example, for a substance with a high content of mobile forms of Cd, Pb, Zn, the biomass and root length of oat seedlings were higher than for oats grown on another substance. The translocation index indicates that the accumulation of most metals and metalloids is higher in the roots than in the aerial parts of oats

Летучесть химических элементов при дегидрации вторичных сульфатов

Актуальность. Загрязнение воздуха в результате деятельности горнодобывающей и металлургической промышленности является серьезной проблемой для окружающей среды. Это исследование проводилось с целью определения возможных механизмов миграции и источников элементов в атмосфере над поверхностью хвостохранилищ. Основная цель исследования - показать, что химические элементы могут захватываться водяным паром и могут мигрировать с паровой фазой во время десорбции и дегидратации водных сульфатов. Объект: образцы с поверхности отвалов, Белово (Беловский цинкозавод, Белово, Россия). Методы. Порошковая рентгеновская дифрактометрия (XRD) использовалась для определения фазового состава кристаллических веществ, их количественных фазовых соотношений и превращений. Для определения элементов в пробах воды (поровый раствор и конденсаты) использовали прибор Agilent 8800 ICP-MS (Токио, Япония), оборудованный распылителем MicroMist. Также использовались бинокулярный микроскоп и методы физико-химического моделирования. Результаты. Путем анализа конденсатов было определено, что широкий спектр химических элементов может мигрировать с парогазовыми потоками из вторичных гидросульфатов в относительно низкотемпературных условиях (60 °C). Конденсат влажного образца содержит высокие концентрации элементов из-за поступления элементов из порового раствора и водных сульфатов. На изменение минеральной структуры и выделение воды указывает потеря веса пробы. При дегидратации катионы и микроэлементы могут быть извлечены из кристаллической решетки, заменены протонами и затем могут перейти в парогазовую фазу при испарении раствора.The relevance. Air pollution due to the activities of the mining and metallurgical industries is a serious problem for the environment. This study was conducted to determine the possible mechanisms of migration and the sources of elements in the atmosphere above the surface of tailings. The main aim of the research is to show that chemical elements can be trapped by the water vapor and can migrate with the vapor phase during the desorption and dehydration of hydrous sulfates. Object: samples from the surface of the Belovo waste heaps (Belovo zinc processing plant, Belovo, Russia). Methods. Powder X-ray diffractometry (XRD) was used to determine the phase compositions of the crystalline substances, their quantitative phase relationships and transformations. An Agilent 8800 ICP-MS instrument (Tokyo, Japan), equipped with a MicroMist nebulizer, was used to determine the elements in the water samples (pore solution and condensates). Also, we used binocular microscope and physicochemical modeling methods. Results. By analyzing the condensates, it was determined that a wide range of chemical elements can migrate with vapor-gas streams from secondary hydrous sulfates under relatively low-temperature conditions (60 °C). Condensate from the wet sample contains high element concentrations due to the input of elements from the pore solution and hydrous sulfates. Alterations in mineral structure and water release are indicated by losses of sample weight. With dehydration, cations and trace elements can be extracted from the crystal lattice, replaced by protons, and can then enter the vapor-gas phase when the solution evaporates