Jarosite versus Soluble Iron-Sulfate Formation and Their Role in Acid Mine Drainage Formation at the Pan de Azúcar Mine Tailings (Zn-Pb-Ag), NW Argentina

Secondary jarosite and water-soluble iron-sulfate minerals control the composition of acid mine waters formed by the oxidation of sulfide in tailings impoundments at the (Zn-Pb-Ag) Pan de Azúcar mine located in the Pozuelos Lagoon Basin (semi-arid climate) in Northwest (NW) Argentina. In the primary zone of the tailings (9.5 wt % pyrite-marcasite) precipitation of anglesite (PbSO4), wupatkite ((Co,Mg,Ni)Al2(SO4)4) and gypsum retain Pb, Co and Ca, while mainly Fe2+, Zn2+, Al3+, Mg2+, As3+/5+ and Cd2+ migrate downwards, forming a sulfate and metal-rich plume. In the oxidation zone, jarosite (MFe3(TO4)2(OH)6) is the main secondary Fe3+ phase; its most suitable composition is M = K+, Na+, and Pb2+and TO4 = SO42−; AsO42−. During the dry season, iron-sulfate salts precipitate by capillary transport on the tailings and at the foot of DC2 (tailings impoundment DC2) tailings dam where an acid, Fe2+ rich plume outcrops. The most abundant compounds in the acid mine drainage (AMD) are SO42−, Fe2+, Fe3+, Zn2+, Al3+, Mg2+, Cu2+, As3+/5+, Cd2+. These show peak concentrations at the beginning of the wet season, when the soluble salts and jarosite dissolve. The formation of soluble sulfate salts during the dry season and dilution during the wet season conform an annual cycle of rapid metals and acidity transference from the tailings to the downstream environment.Fil: Murray, Jesica María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Kirschbaum, Alicia Matilde. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Dold, Bernhard. Sustainable Mining Research & Consult EIRL; ChileFil: Mendes Guimaraes, Edi. Universidade do Brasilia; BrasilFil: Pannunzio Miner, Elisa Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentin

Combinatorial Stokes formulas via minimal resolutions

We describe an explicit chain map from the standard resolution to the minimal resolution for the finite cyclic group Z_k of order k. We then demonstrate how such a chain map induces a "Z_k-combinatorial Stokes theorem", which in turn implies "Dold's theorem" that there is no equivariant map from an n-connected to an n-dimensional free Z_k-complex. Thus we build a combinatorial access road to problems in combinatorics and discrete geometry that have previously been treated with methods from equivariant topology. The special case k=2 for this is classical; it involves Tucker's (1949) combinatorial lemma which implies the Borsuk-Ulam theorem, its proof via chain complexes by Lefschetz (1949), the combinatorial Stokes formula of Fan (1967), and Meunier's work (2006).Comment: 18 page

Environmental and socioeconomic assessment of impacts by mining activities—a case study in the Certej River catchment, Western Carpathians, Romania

Background, aim and scope: In the region of the Apuseni Mountains, part of the Western Carpathians in Romania, metal mining activities have a long-standing tradition. These mining industries created a clearly beneficial economic development in the region. But their activities also caused impairments to the environment, such as acid mine drainage (AMD) resulting in long-lasting heavy metal pollution of waters and sediments. The study, established in the context of the ESTROM programme, investigated the impact of metal mining activities both from environmental and socioeconomic perspectives and tried to incorporate the results of the two approaches into an integrated proposition for mitigation of mining-related issues. Study site: The small Certej catchment, situated in the Southern Apuseni Mountains, covers an area of 78km2. About 4,500 inhabitants are living in the basin, in which metal mining was the main economic sector. An open pit and several abandoned underground mines are producing heavy metal-loaded acidic water that is discharged untreated into the main river. The solid wastes of mineral processing plants were deposited in several dumps and tailings impoundment embodying the acidic water-producing mineral pyrite. Methods: The natural science team collected samples from surface waters, drinking water from dug wells and from groundwater. Filtered and total heavy metals, both after enrichment, and major cations were analysed by inductively coupled plasma optical emission spectroscopy (ICP-OES). Major anions in waters, measured by ion chromatography, alkalinity and acidity were determined by titration. Solid samples were taken from river sediments and from the largest tailings dam. The latter were characterised by X-ray fluorescence and X-ray diffraction. Heavy metals in sediments were analysed after digestion. Simultaneously, the socioeconomic team performed a household survey to evaluate the perception of people related to the river and drinking water pollution by way of a logistic regression analysis. Results and discussion: The inputs of acid mine waters drastically increased filtered heavy metal concentrations in the Certej River, e.g. Zn up to 130mg L−1, Fe 100mg L−1, Cu 2.9mg L−1, Cd 1.4mgL−1 as well as those of SO4 up to 2.2g L−1. In addition, river water became acidic with pH values of pH 3. Concentrations of pollutant decreased slightly downstream due to dilution by waters from tributaries. Metal concentrations measured at headwater stations reflect background values. They fell in the range of the environmental quality standards proposed in the EU Water Framework Directive for dissolved heavy metals. The outflow of the large tailing impoundment and the groundwater downstream from two tailings dams exhibited the first sign of AMD, but they still had alkalinity. Most dug wells analysed delivered a drinking water that exhibited no sign of AMD pollution, although these wells were a distance of 7 to 25m from the contaminated river. It seems that the Certej River does not infiltrate significantly into the groundwater. Pyrite was identified as the main sulphide mineral in the tailings dam that produces acidity and with calcite representing the AMD-neutralising mineral. The acid-base accounting proved that the potential acid-neutralising capacity in the solid phases would not be sufficient to prevent the production of acidic water in the future. Therefore, the open pits and mine waste deposits have to be seen as the sources for AMD at the present time, with a high long-term potential to produce even more AMD in the future. The socioeconomic study showed that mining provided the major source of income. Over 45% of the households were partly or completely reliant on financial compensations as a result of mine closure. Unemployment was considered by the majority of the interviewed persons as the main cause of social problems in the area. The estimation of the explanatory factors by the logistic regression analysis revealed that education, household income, pollution conditions during the last years and familiarity with environmental problems were the main predictors influencing peoples' opinion concerning whether the main river is strongly polluted. This model enabled one to predict correctly 77% of the observations reported. For the drinking water quality model, three predictors were relevant and they explained 66% of the observations. Conclusions: Coupling the findings from the natural science and socioeconomic approaches, we may conclude that the impact of mining on the Certej River water is high, while drinking water in wells is not significantly affected. The perceptions of the respondents to pollution were to a large extent consistent with the measured results. Recommendations and perspectives: The results of the study can be used by various stakeholders, mainly the mining company and local municipalities, in order to integrate them in their post-mining measures, thereby making them aware of the potential long-term impact of mining on the environment and on human health as well as on the local econom

Evolución del volcanismo submarino en el estrecho Bransfield: Relación de las emanaciones hidrotermales con la biodiversidad y el cambio climático - [Boletín M 1]

Las expediciones científicas peruanas a la Antártida se realizan desde el año 1988, fecha en la que se realizó la Primera Expedición Científica Peruana a la Antártida – ANTAR I. Esta expedición se realizó a bordo del BIC Humboldt. El Ingemmet, como ente rector de las geociencias en nuestro país, participa desde la segunda expedición antártica, primero como apoyo técnico y geológico en Punta Crepín, isla Rey Jorge, para la construcción y ampliación de la Estación Científica Machu Picchu. A partir del período 2018-2019 y con arribo de la moderna plataforma BAP Carrasco, se empiezan a desarrollar proyectos de investigación multidisciplinarios en geología marina y antártica, con colaboración de instituciones nacionales e internacionales. Siendo así, el Ingemmet, para el desarrollo de la XXVII Expedición Científica Peruana a la Antártida – ANTAR XXVII, presenta un proyecto multidisciplinario que busca relacionar el impacto de la geología en la distribución y biodiversidad del fondo marino Este proyecto se titula “Evolución del Volcanismo Submarino en el estrecho de Bransfield: Relación de las Emanaciones Hidrotermales con la Biodiversidad y el Cambio Climático” y se desarrolla en coordinación y cooperación entre el Instituto Geológico Minero y Metalúrgico (Ingemmet), la universidad Científica del Sur (Científica – Perú), la Facultad de Ciencias, Universidad de la República (Uruguay) y el Instituto de Investigaciones Marinas y Costeras José Benito Vives de Andréis (Invemar - Colombia). Este proyecto busca caracterizar la morfología y composición de los volcanes y emanaciones hidrotermales submarinas, así como identificar las comunidades biológicas, microbiológicas y características medioambientales del estrecho de Bransfield, Antártida. Siendo así, las actividades para cumplir este objetivo se desarrollan a través de la realización de cruceros de investigación geológica-oceanográfica, que se denominan cruceros multinacionales ORCA. La ejecución de las actividades se realiza a bordo de la plataforma científica BAP Carrasco, y son coordinadas por la Dirección de Asuntos Antárticos del Ministerio de Relaciones Exteriores. El crucero tuvo una duración de 15 días efectivos de trabajo y abarco 4 áreas de recolección de información: bahía Collins, bahía Almirantazgo, bahía Esperanza y estrecho de Bransfield. Así también, comprendió el levantamiento de información geológica, oceanográfica, biológica, microbiológica, radiológica y de microplásticos entre la isla Rey Jorge y la península antártica. El presente boletín tiene por objetivo mostrar toda la información recopilada durante el desarrollo del Crucero ORCA I, para que sea de disponibilidad de la comunidad científica

Evolution of Acid Mine Drainage Formation in Sulphidic Mine Tailings

Sulphidic mine tailings are among the largest mining wastes on Earth and are prone to produce acid mine drainage (AMD). The formation of AMD is a sequence of complex biogeochemical and mineral dissolution processes. It can be classified in three main steps occurring from the operational phase of a tailings impoundment until the final appearance of AMD after operations ceased: (1) During the operational phase of a tailings impoundment the pH-Eh regime is normally alkaline to neutral and reducing (water-saturated). Associated environmental problems include the presence of high sulphate concentrations due to dissolution of gypsum-anhydrite, and/or effluents enriched in elements such as Mo and As, which desorbed from primary ferric hydroxides during the alkaline flotation process. (2) Once mining-related operations of the tailings impoundment has ceased, sulphide oxidation starts, resulting in the formation of an acidic oxidation zone and a ferrous iron-rich plume below the oxidation front, that re-oxidises once it surfaces, producing the first visible sign of AMD, i.e., the precipitation of ferrihydrite and concomitant acidification. (3) Consumption of the (reactive) neutralization potential of the gangue minerals and subsequent outflow of acidic, heavy metal-rich leachates from the tailings is the final step in the evolution of an AMD system. The formation of multi-colour efflorescent salts can be a visible sign of this stage

Submarine Tailings Disposal (STD)—A Review

The mining industry is a fundamental industry involved in the development of modern society, but is also the world’s largest waste producer. This role will be enhanced in the future, because ore grades are generally decreasing, thus leading to increases in the waste/metal production ratio. Mine wastes deposited on-land in so-called tailings dams, impoundments or waste-dumps have several associated environmental issues that need to be addressed (e.g., acid mine drainage formation due to sulphide oxidation, geotechnical stability, among others), and social concerns due to land use during mining. The mining industry recognizes these concerns and is searching for waste management alternatives for the future. One option used in the past was the marine shore or shallow submarine deposition of this waste material in some parts of the world. After the occurrence of some severe environmental pollution, today the deposition in the deep sea (under constant reducing conditions) is seen as a new, more secure option, due to the general thought that sulphide minerals are geochemically stable under the reduced conditions prevailing in the deep marine environment. This review highlights the mineralogical and geochemical issues (e.g., solubility of sulphides in seawater; reductive dissolution of oxide minerals under reducing conditions), which have to be considered when evaluating whether submarine tailings disposal is a suitable alternative for mine waste

Mineralogical and geochemical changes of copper flotation tailings in relation to their original composition and climatic setting : implications for acid mine drainage and element mobility

In the present work six flotation tailings impoundments at five flotation plants (Piuquenes, Cauquenes, El Salvador, Ojancos, P. Cerda) located in different climatic zones of Chile were selected to investigate the mineralogical and geochemical changes taking place in copper flotation tailings subsequent to sulfide oxidation, especially the formation of acid mine drainage and element mobility. Results show the importance of primary mineralogy (acid producing and acid neutralizing minerals) in controlling the mobility of the liberated elements due to pH control. Climatic conditions control the element mobilization directions (humid = downwards; arid = upwards) and so the geochemical conditions where these elements may precipitate as secondary minerals (humid = reducing conditions below the water table; arid = oxidizing conditions at the surface). The climate controls so the secondary mineralogy and thus the availability of hazardous heavy metals to the environment. Additionally the impoundment construction technique may influence the mobilization and enrichment processes

Evolution of Geochemical and Mineralogical Parameters during In Situ Remediation of a Marine Shore Tailings Deposit by the Implementation of a Wetland Cover

We present data of the time-evolution of a remediation approach on a marine shore tailings deposit by the implementation of an artificial wetland. Two remediation cells were constructed: one in the northern area at sea-level and one in the central delta area (above sea-level) of the tailings. At the beginning, the “sea-level” remediation cell had a low pH (3.1), with high concentrations of dissolved metals and sulfate and chloride ions and showed sandy grain size. After wetland implementation, the “sea-level” remediation cell was rapidly water-saturated, the acidity was consumed, and after four months the efficiency of metal removal from solution was up to 79.5%–99.4% for Fe, 94.6%–99.9% for Mn, and 96.1%–99.6% for Zn. Al and Cu concentrations decreased below detection limit. The “above sea-level” remediation cell was characterized by the same pH (3.1) and finer grain size (clayey–silty), and with some lower element concentrations than in the “sea-level” cell. Even after one year of flooding, the “above sea-level” cell was not completely flooded, showing on-going sulfide oxidation in between the wetland cover and the groundwater level; the pH increased only to 4.4 and metal concentrations decreased only by 96% for Fe, 88% for Al, 51% for Cu, 97% for Mn, and 95% for Zn. During a dry period, the water level dropped in the “sea-level” cell, resulting in a seawater ingression, which triggered the desorption of As into solution. These data show that the applied remediation approach for this tailings deposit is successful, if the system is maintained water-saturated. Metal removal from solution was possible in both systems: first, as a result of sorption on Fe(III) hydroxide/and/or clay minerals and/or co-precipitation processes after rise of pH; and then, with more reducing conditions, due to metal sulfides precipitation