Special Issue "Pollutants in Acid Mine Drainage"

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Environmental Mineralogy and Biogeochemistry".

Deadline for manuscript submissions: closed (27 November 2020).

Special Issue Editor

Dr. Teresa Valente
E-Mail Website
Guest Editor
Earth Sciences Department, University of Minho, 4710-057 Braga, Portugal
Interests: mine waters and mine wastes; acid mine drainage and acid rock drainage; environmental mineralogy; biomonitoring; environmental monitoring and modeling of mine sites

Special Issue Information

Dear Colleagues,

Acid mine drainage (AMD) is one of the major environmental consequences of mining activity that often causes complete degradation of the ecosystems during and or after mine closure. AMD is a peculiar focus of research because it involves assessing the presence and reactivity of various pollutants, which may affect the subsequent analytical processes of characterization.

The systems affected by AMD have high heterogeneity and generate samples with complex matrices. Moreover, frequently, AMD generates high amounts of colloids, most in the nanoscale dimensions. Further, acid drainage represents peculiar ecosystems, dominated by acidophilic organisms involved in complex interactions with influence on the migration and fate of pollutants. In addition, evolution of AMD promotes the development of AMD-precipitates that control the equilibrium and evolution conditions. This Special Issue aims to cover the diversity of research items associated with the complexity of AMD, such as the source and nature of the pollutants, speciation, migration, fate, and toxicity, including that of nanoparticles, and the biogeochemistry and mineralogy of the AMD systems. Papers providing examples of the methodological challenges and with novel tools for monitoring and characterization of AMD are welcome.

Dr. Teresa Valente
Guest Editor

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Keywords

  • Acidity
  • Stress conditions
  • AMD-precipitates
  • Monitoring tools
  • Transport and fate
  • Nanopollutants

Published Papers (19 papers)

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Research

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Article
Lead Mobilization and Speciation in Mining Waste: Experiments and Modeling
Minerals 2021, 11(6), 606; https://doi.org/10.3390/min11060606 - 05 Jun 2021
Viewed by 346
Abstract
Mining produces significant amounts of solid mineral waste. Mine waste storage facilities are often challenging to manage and may cause environmental problems. Mining waste is often linked to contaminated mine drainage, including acidic waters with more or less elevated concentrations of trace metals [...] Read more.
Mining produces significant amounts of solid mineral waste. Mine waste storage facilities are often challenging to manage and may cause environmental problems. Mining waste is often linked to contaminated mine drainage, including acidic waters with more or less elevated concentrations of trace metals such as lead. This work presents a study on the mobilization of lead from waste from two typical mining sites: Zeida and Mibladen, two now-closed former Pb–Zn mines in the Moulouya region of Morocco. Our research investigates the mobilization potential of Pb from the waste of these mines. The study involved acid–base neutralization capacity tests (ANC–BNC) combined with geochemical modeling. Experimental data allowed for the quantification of the buffering capacity of the samples and the mobilization rates of lead as a function of pH. The geochemical model was fitted to experimental results with thermodynamic considerations. The geochemical model allowed for the identification of the mineral phases involved in providing the buffering capacity of carbonated mining waste (Mibladen) and the meager buffering capacity of the silicate mining waste (Zeida). These cases are representative of contaminated neutral drainage (CND) and acid mine drainage (AMD), respectively. The results highlight the consistency between the ANC–BNC experimental data and the associated modeling in terms of geochemical behavior, validating the approach and identifying the main mechanisms involved. The modeling approach identifies the dissolution of the main solid phases, which impact the pH and the speciation of lead as a function of the pH. This innovative approach, combining ANC–BNC experiments and geochemical modeling, allowed for the accurate identification of mineral phases and surface complexation phenomena, which control the release of lead and its speciation in drainage solutions, as well as within solid phases, as a function of pH. Full article
(This article belongs to the Special Issue Pollutants in Acid Mine Drainage)
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Article
ANC–BNC Titrations and Geochemical Modeling for Characterizing Calcareous and Siliceous Mining Waste
Minerals 2021, 11(3), 257; https://doi.org/10.3390/min11030257 - 28 Feb 2021
Cited by 1 | Viewed by 587
Abstract
Pyrite and calcite are mineral phases that play a major role in acid and neutral mine drainage processes. However, the prediction of acid mine drainage (AMD) or contaminated neutral drainage (CND) requires knowledge of the mineral composition of mining waste and the related [...] Read more.
Pyrite and calcite are mineral phases that play a major role in acid and neutral mine drainage processes. However, the prediction of acid mine drainage (AMD) or contaminated neutral drainage (CND) requires knowledge of the mineral composition of mining waste and the related potential for element release. This paper studies the combination of acid–base neutralizing capacity (ANC–BNC) with geochemical modeling for the characterization of mining waste and prediction of AMD and CND. The proposed approach is validated with three synthetic mineral assemblages: (1) siliceous sand with pyrite only, representing mining waste responsible for AMD, (2) siliceous sand with calcite and pyrite, representing calcareous waste responsible for CND, and (3) siliceous sand with calcite only, simulating calcareous matrices without any pyrite. The geochemical modeling approach using PHREEQC software was used to model pH evolution and main element release as a function of the added amount of acid or base over the entire pH range: 1 < pH < 13. For calcareous matrices (sand with calcite), the results are typical of a carbonated environment, the geochemistry of which is well known. For matrices containing pyrite, the results identify different pH values favoring the dissolution of pyrite: pH = 2 in a pyrite-only environment and pH = 6 where pyrite coexists with calcite. The neutral conditions can be explained by the buffering capacity of calcite, which allows iron oxyhydroxide precipitation. Major element release is then related to the dissolution and precipitation of the mineral assemblages. The geochemical modeling allows the prediction of element speciation in the solid and liquid phases. Our findings clearly prove the potential of combined ANC–BNC experiments along with geochemical modeling for the characterization of mining waste and the assessment of risk of AMD and CND. Full article
(This article belongs to the Special Issue Pollutants in Acid Mine Drainage)
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Article
UAS-Based Hyperspectral Environmental Monitoring of Acid Mine Drainage Affected Waters
Minerals 2021, 11(2), 182; https://doi.org/10.3390/min11020182 - 09 Feb 2021
Cited by 1 | Viewed by 1342
Abstract
The exposure of metal sulfides to air or water, either produced naturally or due to mining activities, can result in environmentally damaging acid mine drainage (AMD). This needs to be accurately monitored and remediated. In this study, we apply high-resolution unmanned aerial system [...] Read more.
The exposure of metal sulfides to air or water, either produced naturally or due to mining activities, can result in environmentally damaging acid mine drainage (AMD). This needs to be accurately monitored and remediated. In this study, we apply high-resolution unmanned aerial system (UAS)-based hyperspectral mapping tools to provide a useful, fast, and non-invasive method for the monitoring aspect. Specifically, we propose a machine learning framework to integrate visible to near-infrared (VNIR) hyperspectral data with physicochemical field data from water and sediments, together with laboratory analyses to precisely map the extent of acid mine drainage in the Tintillo River (Spain). This river collects the drainage from the western part of the Rio Tinto massive sulfide deposit and discharges large quantities of acidic water with significant amounts of dissolved metals (Fe, Al, Cu, Zn, amongst others) into the Odiel River. At the confluence of these rivers, different geochemical and mineralogical processes occur due to the interaction of very acidic water (pH 2.5–3.0) with neutral water (pH 7.0–8.0). This complexity makes the area an ideal test site for the application of hyperspectral mapping to characterize both rivers and better evaluate contaminated water bodies with remote sensing imagery. Our approach makes use of a supervised random forest (RF) regression for the extended mapping of water properties, using the samples collected in the field as ground-truth and training data. The resulting maps successfully estimate the concentration of dissolved metals and related physicochemical properties in water, and trace associated iron species (e.g., jarosite, goethite) within sediments. These results highlight the capabilities of UAS-based hyperspectral data to monitor water bodies in mining environments, by mapping their hydrogeochemical properties, using few field samples. Hence, we have demonstrated that our workflow allows the rapid discrimination and mapping of AMD contamination in water, providing an essential basis for monitoring and subsequent remediation. Full article
(This article belongs to the Special Issue Pollutants in Acid Mine Drainage)
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Article
Algae in Acid Mine Drainage and Relationships with Pollutants in a Degraded Mining Ecosystem
Minerals 2021, 11(2), 110; https://doi.org/10.3390/min11020110 - 22 Jan 2021
Viewed by 491
Abstract
Acid mine drainage represents an extreme environment with high concentrations of potentially toxic elements and low pH values. These aquatic habitats are characterised by harsh conditions for biota, being dominated by acidophilic organisms. The study site, São Domingos mine, located in one of [...] Read more.
Acid mine drainage represents an extreme environment with high concentrations of potentially toxic elements and low pH values. These aquatic habitats are characterised by harsh conditions for biota, being dominated by acidophilic organisms. The study site, São Domingos mine, located in one of the largest metallogenetic provinces in the world, the Iberian Pyrite Belt, was closed without preventive measures. To identify the algae species and understand the relationships with abiotic parameters of the ecosystem, water and biological material were collected and analysed. Digital terrain models were obtained with an unmanned aerial vehicle for geomorphological and hydrologic characterisation of the mine degraded landscape. The results show two types of algal colours that seem to represent different degrees of photosynthetic activity. Optical and scanning electron microscopy revealed 14 taxa at the genus level, divided into eight classes. The genus Mougeotia is the most abundant multicellular algae. With respect to unicellular algae, diatoms are ubiquitous and abundant. Abiotic analyses expose typical features of acid mine drainage and support an inverse relationship between chemical contamination and biological diversity. Factorial correspondence analysis indicates three groups of attributes and samples by their relationship with specific toxic elements. This analysis also suggests a close association between Spirogyra and Pb, together composing a structurally simple ecosystem. The highest contamination in the river system is related to the hydrologic patterns obtained from photogrammetric products, such as the digital surface model and flow map accumulation, indicating the input of leachates from the section having the finest sulfide-rich wastes. Information about the algae community and their association with flow patterns of toxic elements is a relevant tool from a biomonitoring perspective. Full article
(This article belongs to the Special Issue Pollutants in Acid Mine Drainage)
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Article
Mineralogical and Geochemical Characterization of Gold Mining Tailings and Their Potential to Generate Acid Mine Drainage (Minas Gerais, Brazil)
Minerals 2021, 11(1), 39; https://doi.org/10.3390/min11010039 - 31 Dec 2020
Viewed by 784
Abstract
For more than 30 years, sulfide gold ores were treated in metallurgic plants located in Nova Lima, Minas Gerais, Brazil, and accumulated in the Cocoruto tailings dam. Both flotation and leaching tailings from a deactivated circuit, as well as roasted and leaching tailings [...] Read more.
For more than 30 years, sulfide gold ores were treated in metallurgic plants located in Nova Lima, Minas Gerais, Brazil, and accumulated in the Cocoruto tailings dam. Both flotation and leaching tailings from a deactivated circuit, as well as roasted and leaching tailings from an ongoing plant, were studied for their acid mine drainage potential and elements’ mobility. Detailed characterization of both tailings types indicates the presence of fine-grain size material hosting substantial amounts of sulfides that exhibit distinct geochemical and mineralogical characteristics. The samples from the ongoing plant show high grades of Fe in the form of oxides, cyanide, and sulfates. Differently, samples from the old circuit shave higher average concentrations of Al (0.88%), Ca (2.4%), Mg (0.96%), and Mn (0.17%), present as silicates and carbonates. These samples also show relics of preserved sulfides, such as pyrite and pyrrhotite. Concentrations of Zn, Cu, Au, and As are higher in the tailings of the ongoing circuit, while Cr and Hg stand out in the tailings of the deactivated circuit. Although the obtained results show that the sulfide wastes do not tend to generate acid mine drainage, leaching tests indicate the possibility of mobilization of toxic elements, namely As and Mn in the old circuit, and Sb, As, Fe, Ni, and Se in the tailings of the plant that still works. This work highlights the need for proper management and control of tailing dams even in alkaline drainage environments such as the one of the Cocoruto dam. Furthermore, strong knowledge of the tailings’ dynamics in terms of geochemistry and mineralogy would be pivotal to support long-term decisions on wastes management and disposal. Full article
(This article belongs to the Special Issue Pollutants in Acid Mine Drainage)
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Article
Geochemical Controls on Uranium Release from Neutral-pH Rock Drainage Produced by Weathering of Granite, Gneiss, and Schist
Minerals 2020, 10(12), 1104; https://doi.org/10.3390/min10121104 - 09 Dec 2020
Viewed by 667
Abstract
We investigated geochemical processes controlling uranium release in neutral-pH (pH ≥ 6) rock drainage (NRD) at a prospective gold deposit hosted in granite, schist, and gneiss. Although uranium is not an economic target at this deposit, it is present in the host rock [...] Read more.
We investigated geochemical processes controlling uranium release in neutral-pH (pH ≥ 6) rock drainage (NRD) at a prospective gold deposit hosted in granite, schist, and gneiss. Although uranium is not an economic target at this deposit, it is present in the host rock at a median abundance of 3.7 µg/g, i.e., above the average uranium content of the Earth’s crust. Field bin and column waste-rock weathering experiments using gneiss and schist mine waste rock produced circumneutral-pH (7.6 to 8.4) and high-alkalinity (41 to 499 mg/L as CaCO3) drainage, while granite produced drainage with lower pH (pH 4.7 to >8) and lower alkalinity (<10 to 210 mg/L as CaCO3). In all instances, U release was associated with calcium release and formation of weakly sorbing calcium-carbonato-uranyl aqueous complexes. This process accounted for the higher release of uranium from carbonate-bearing gneiss and schist than from granite despite the latter’s higher solid-phase uranium content. In addition, unweathered carbonate-bearing rocks having a higher sulfide-mineral content released more uranium than their oxidized counterparts because sulfuric acid produced during sulfide-mineral oxidation promoted dissolution of carbonate minerals, release of calcium, and formation of calcium-carbonato-uranyl aqueous complexes. Substantial uranium attenuation occurred during a sequencing experiment involving application of uranium-rich gneiss drainage into columns containing Fe-oxide rich schist. Geochemical modeling indicated that uranium attenuation in the sequencing experiment could be explained through surface complexation and that this process is highly sensitive to dissolved calcium concentrations and pCO2 under NRD conditions. Full article
(This article belongs to the Special Issue Pollutants in Acid Mine Drainage)
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Article
Selective Removal of As(V) Ions from Acid Mine Drainage Using Polymer Inclusion Membranes
Minerals 2020, 10(10), 909; https://doi.org/10.3390/min10100909 - 14 Oct 2020
Cited by 1 | Viewed by 638
Abstract
Acid mine drainage (AMD) is globally recognized as one of the environmental pollutants of the priority concern due to high concentrations of toxic metals and sulfates. More rigorous environmental legislation requires exploitation of effective technologies to remove toxic metals from contaminated streams. In [...] Read more.
Acid mine drainage (AMD) is globally recognized as one of the environmental pollutants of the priority concern due to high concentrations of toxic metals and sulfates. More rigorous environmental legislation requires exploitation of effective technologies to remove toxic metals from contaminated streams. In view of high selectivity, effectiveness, durability, and low energy demands, the separation of toxic metal ions using immobilized membranes with admixed extractants could ameliorate water quality. Cellulose triacetate based polymer inclusion membranes (PIMs), with extractant and plasticizer, were studied for their ability to transport of As(V) ions from synthetic aqueous leachates. The effects of the type and concentration of extractant, plasticizer content, and sulfuric acid concentration in source phase on the arsenic removal efficiency have been assessed. Under the best of applied conditions, PIM with Cyanex 921 as extractant and o-nitrophenyl octyl ether (o-NPOE) as plasticizer showed high repeatability and excellent transport activity for selective removal of As(V) from AMD. Full article
(This article belongs to the Special Issue Pollutants in Acid Mine Drainage)
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Article
Mineralogical Study and Genetic Model of Efflorescent Salts and Crusts from Two Abandoned Tailings in the Taxco Mining District, Guerrero (Mexico)
Minerals 2020, 10(10), 871; https://doi.org/10.3390/min10100871 - 01 Oct 2020
Cited by 1 | Viewed by 546
Abstract
The mineralogy of surface crusts and efflorescent salts of two old abandoned tailings (Xochula and Remedios) of the mining district of Taxco, Guerrero, was studied by short-wave infrared spectroscopy (SWIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The chemistry of the selected [...] Read more.
The mineralogy of surface crusts and efflorescent salts of two old abandoned tailings (Xochula and Remedios) of the mining district of Taxco, Guerrero, was studied by short-wave infrared spectroscopy (SWIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The chemistry of the selected samples was studied with induced coupled plasma mass spectrometry (ICP–MS). Principal mineralogy is composed of hydrated sulfates of iron (di-trivalent), other less-soluble sulfates such as gypsum and jarosite, and oxides–hydroxides of iron, all of which are the result of the weathering of sulfides (mainly pyrite) accumulated in mining waste. Using quantitative X-ray diffraction (Rietveld method) and the spatial distribution of secondary minerals, two main zones (lateral and central) have been established in both tailings. The genetic model for their formation shows that the secondary iron minerals (sulfates, oxides, and hydroxides) in these deposits have been formed at least in three different stages, mainly by oxidation, dissolution, and precipitation processes in combination with dehydration and primary sulfides neutralization reactions. The chemical analyses of some salts confirm the presence of potentially toxic elements (PTE) in their structure and therefore indicate that the dissolution of the efflorescences in these deposits is a potential source of contamination during the wet season. Full article
(This article belongs to the Special Issue Pollutants in Acid Mine Drainage)
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Article
Sulfur Species, Bonding Environment, and Metal Mobilization in Mining-Impacted Lake Sediments: Column Experiments Replicating Seasonal Anoxia and Deposition of Algal Detritus
Minerals 2020, 10(10), 849; https://doi.org/10.3390/min10100849 - 25 Sep 2020
Viewed by 913
Abstract
The oxidation state of sulfur [S] is a primary control on mobility of metals in sediments impacted by legacy mining practices. Coeur d’Alene Lake of northern Idaho, USA, has been impacted by upstream legacy mining practices that deposited an estimated 75 Mt of [...] Read more.
The oxidation state of sulfur [S] is a primary control on mobility of metals in sediments impacted by legacy mining practices. Coeur d’Alene Lake of northern Idaho, USA, has been impacted by upstream legacy mining practices that deposited an estimated 75 Mt of metal(loid)- and S-rich sediments into the lake. Future lake conditions are expected to include algal blooms, which may alter S and metal remobilization during the seasonal euxinic environment. Cores of the lake sediments were exposed to anoxic and anoxic + algal detritus conditions for eight weeks at 4.5 °C through introduction of a N2 atmosphere and addition of algal detritus. At a location 2.5 cm below the sediment-water interface, anoxic conditions promoted a shift in S species to continually larger concentrations of reduced species and an associated shift in the bonding environment reflective of increased S–metal bonds. Anoxic + algal detritus conditions suppressed the increasing trend of reduced S species and induced greater release of Mn compared to the anoxic-only conditions but did not appear to enhance the release of As, Cd, or Fe. The addition of algal detritus to the sediment-water interface of these Fe- and S-rich sediments enhanced mobilization of Mn likely because of dissimilatory metal reduction where the anaerobic oxidation of the algal detritus stimulated Mn reduction. Results of the study indicate that future metal release from the lake sediments will be altered with the likely deposition of algal detritus, but the effect may not enhance the release of acutely toxic metals, such as As or Cd, or substantially impact Fe cycling in the sediments. Full article
(This article belongs to the Special Issue Pollutants in Acid Mine Drainage)
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Article
Removal of Pollutants from an AMD from a Coal Mine by Neutralization/Precipitation Followed by “In Vivo” Biosorption Step with the Microalgae Scenedesmus sp.
Minerals 2020, 10(8), 711; https://doi.org/10.3390/min10080711 - 12 Aug 2020
Cited by 2 | Viewed by 864
Abstract
This work evaluates the benefits of a complementary treatment step of acid mine drainage (AMD) using the algae Scenedesmus sp. in terms of algae biomass production, residual metal removal, and the toxicity of the discharged water. Conventional treatment by neutralization/precipitation of an AMD [...] Read more.
This work evaluates the benefits of a complementary treatment step of acid mine drainage (AMD) using the algae Scenedesmus sp. in terms of algae biomass production, residual metal removal, and the toxicity of the discharged water. Conventional treatment by neutralization/precipitation of an AMD from a coal mine in Brazil was conducted with Ca(OH)2 at pH 8.7. Algal growth studies were performed in the treated AMD, with and without a nutrient supply. The raw effluent and treatments were compared in terms of residual concentration of metals and sulfate, conductivity, and toxicity with the Allium cepa and Daphnia magna test organisms. The results show that the conventional treatment allowed a major metal removal, reduction in the conductivity, and good indices in the toxicological parameters evaluated. The biosorption with in vivo microalgae improved the quality of the effluent for residual metals. No significant toxicity was observed to Allium cepa in all treatments performed, while the Daphnia magna test indicated a reduction in toxicity after the biosorption step. It was concluded that algae growth can be carried out in treated mine waters, providing algae biomass and helping to achieve the standards for water discharge. Full article
(This article belongs to the Special Issue Pollutants in Acid Mine Drainage)
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Article
Numerical Modeling of a Laboratory-Scale Waste Rock Pile Featuring an Engineered Cover System
Minerals 2020, 10(8), 652; https://doi.org/10.3390/min10080652 - 23 Jul 2020
Cited by 5 | Viewed by 1025
Abstract
Improved design to reduce contaminant mass loadings from waste rock piles is an increasingly important consideration. In certain cases, an engineered cover system containing a flow control layer (FCL) may be used to mitigate the release of metals out of a pile using [...] Read more.
Improved design to reduce contaminant mass loadings from waste rock piles is an increasingly important consideration. In certain cases, an engineered cover system containing a flow control layer (FCL) may be used to mitigate the release of metals out of a pile using capillary barrier effects (CBEs), diverting water away from reactive materials below. In this study, a reactive transport model was calibrated to observational data from a laboratory experiment designed to evaluate a cover system. The results show that the numerical model is capable of capturing flow rates out of multiple drainage ports and matching key effluent concentrations by including the spatial distribution of hydraulic parameters and mineral weathering rates. Simulations were also useful for characterizing the internal flow pathways within the laboratory experiment, showing the effectiveness of the cover in diverting the flow away from the reactive waste rock and identifying secondary CBEs between different rock types. The numerical model proved beneficial in building an improved understanding of the processes controlling the metal release and conceptualizing the system. The model was expanded to investigate the robustness of the cover system as a function of the applied infiltration rate, supporting that water diversion will occur with infiltration rates representative of field conditions. Full article
(This article belongs to the Special Issue Pollutants in Acid Mine Drainage)
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Article
The Evolution of Pollutant Concentrations in a River Severely Affected by Acid Mine Drainage: Río Tinto (SW Spain)
Minerals 2020, 10(7), 598; https://doi.org/10.3390/min10070598 - 30 Jun 2020
Cited by 5 | Viewed by 940
Abstract
The Río Tinto, located in the Iberian Pyrite Belt (SW Spain), constitutes an extreme case of pollution by acid mine drainage. Mining in the area dates back to the Copper Age, although large-scale mining of massive sulfide deposits did not start until the [...] Read more.
The Río Tinto, located in the Iberian Pyrite Belt (SW Spain), constitutes an extreme case of pollution by acid mine drainage. Mining in the area dates back to the Copper Age, although large-scale mining of massive sulfide deposits did not start until the second half of the 19th century. Due to acidic mining discharges, the Río Tinto usually maintains a pH close to 2.5 and high concentrations of pollutants along its course. From a detailed sampling during the hydrological year 2017/18, it was observed that most pollutants followed a similar seasonal pattern, with maximum concentrations during autumn due to the washout of secondary soluble sulfate salts and minimum values during large flood events. Nevertheless, As and Pb showed different behavior, with delayed concentration peaks. The dissolved pollutant load throughout the monitored year reached 5000 tons of Fe, 2600 tons of Al, 680 tons of Zn, and so on. While most elements were transported almost exclusively in the dissolved phase, Fe, Pb, Cr, and, above all, As showed high values associated with particulate matter. River water quality data from 1969 to 2019 showed a sharp worsening in 2000, immediately after the mine closure. From 2001 on, an improvement was observed. Full article
(This article belongs to the Special Issue Pollutants in Acid Mine Drainage)
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Article
Geochemical Modeling of Iron and Aluminum Precipitation during Mixing and Neutralization of Acid Mine Drainage
Minerals 2020, 10(6), 547; https://doi.org/10.3390/min10060547 - 17 Jun 2020
Cited by 3 | Viewed by 913
Abstract
Geochemical modeling of precipitation reactions in the complex matrix of acid mine drainage is fundamental to understanding natural attenuation, lime treatment, and treatment procedures that separate constituents for potential reuse or recycling. The three main dissolved constituents in acid mine drainage are iron, [...] Read more.
Geochemical modeling of precipitation reactions in the complex matrix of acid mine drainage is fundamental to understanding natural attenuation, lime treatment, and treatment procedures that separate constituents for potential reuse or recycling. The three main dissolved constituents in acid mine drainage are iron, aluminum, and sulfate. During the neutralization of acid mine drainage (AMD) by mixing with clean tributaries or by titration with a base such as sodium hydroxide or slaked lime, Ca(OH)2, iron precipitates at pH values of 2–3 if oxidized and aluminum precipitates at pH values of 4–5 and both processes buffer the pH during precipitation. Mixing processes were simulated using the ion-association model in the PHREEQC code. The results are sensitive to the solubility product constant (Ksp) used for the precipitating phases. A field example with data on discharge and water composition of AMD before and after mixing along with massive precipitation of an aluminum phase is simulated and shows that there is an optimal Ksp to give the best fit to the measured data. Best fit is defined when the predicted water composition after mixing and precipitation matches most closely the measured water chemistry. Slight adjustment to the proportion of stream discharges does not give a better fit. Full article
(This article belongs to the Special Issue Pollutants in Acid Mine Drainage)
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Article
Application of GETFLOWS Coupled with Chemical Reactions to Arsenic Removal through Ferrihydrite Coprecipitation in an Artificial Wetland of a Japanese Closed Mine
Minerals 2020, 10(5), 475; https://doi.org/10.3390/min10050475 - 23 May 2020
Cited by 3 | Viewed by 814
Abstract
Passive systems that utilize a natural power such as a pond, plant, or microorganisms, is expected to be a cost-effective method for acid mine drainage (AMD) treatment. The Ningyo-toge mine, a non-operational uranium mine located in Okayama Prefecture, Japan, generates AMD containing arsenic [...] Read more.
Passive systems that utilize a natural power such as a pond, plant, or microorganisms, is expected to be a cost-effective method for acid mine drainage (AMD) treatment. The Ningyo-toge mine, a non-operational uranium mine located in Okayama Prefecture, Japan, generates AMD containing arsenic and iron. To quantitatively study arsenic and iron ion removal in an artificial wetland and pond, chemical reactions were modeled and incorporated into the GETFLOWS (general-purpose terrestrial fluid-flow simulator) software. The chemical reaction models consisted of arsenite and ferrous oxidation equations and arsenic adsorption on ferrihydrite. The X-ray diffraction analysis of sediment samples showed ferrihydrite patterns. These results were consistent with the model for arsenite/ferrous oxidation and arsenic adsorption on ferrihydrite. Geofluid simulation was conducted to simulate mass transfer with the utilized topographic model, inlet flow rate, precipitation, and evaporation. The measured arsenic and iron ions concentrations in solution samples from the wetland and pond, fitted well with the model. This indicated that the main removal mechanism was the oxidation of arsenite/ferrous ions and that arsenic was removed by adsorption rather than dilution. Full article
(This article belongs to the Special Issue Pollutants in Acid Mine Drainage)
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Article
Geochemical Behavior of Potentially Toxic Elements in Riverbank-Deposited Weathered Tailings and Their Environmental Effects: Weathering of Pyrite and Manganese Pyroxene
Minerals 2020, 10(5), 413; https://doi.org/10.3390/min10050413 - 07 May 2020
Cited by 1 | Viewed by 691
Abstract
Uncontrolled management of mine tailings can cause serious environmental problems. Red and black deposits of weathered mine tailings are observed in the upstream of the Nakdong River in Korea, washed away from abandoned mines during floods. Herein, the geochemical and mineralogical changes that [...] Read more.
Uncontrolled management of mine tailings can cause serious environmental problems. Red and black deposits of weathered mine tailings are observed in the upstream of the Nakdong River in Korea, washed away from abandoned mines during floods. Herein, the geochemical and mineralogical changes that occur during weathering of these deposited mine tailings and the mobility of resulting potentially toxic elements were investigated. Primarily, johansennite (manganese pyroxene) was identified in the deposits. Goethite and jarosite were identified as secondary minerals in the red or brown layers. Manganese oxide (MnO) formed by the weathering of johansennite in the black layers and schwertmannite in the red and brown layers were also identified via energy-dispersive X-ray spectroscopy. The three most abundant potentially toxic elements in the residual and iron and manganese oxide fractions were Zn, Pb and As. The high percentage of potentially toxic elements in these oxide fractions indicated that the weathering products of pyrite and manganese pyroxene were crucial in fixing these elements, and MnO likely played an important role in controlling the behavior of heavy metals. In addition, metals were detected in significant concentrations in the exchangeable and carbonate-bound fractions, which can be toxic to the river’s ecological system. Full article
(This article belongs to the Special Issue Pollutants in Acid Mine Drainage)
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Article
Mineral Formation under the Influence of Mine Waters (The Kizel Coal Basin, Russia)
Minerals 2020, 10(4), 364; https://doi.org/10.3390/min10040364 - 17 Apr 2020
Cited by 2 | Viewed by 794
Abstract
The development of coal deposits is accompanied by negative environmental changes. In the territory of the Kizel coal basin (Perm Region, Russia), the problem of contamination of water sources by acid mine waters and runoff from rock dumps is particularly acute. Mine waters [...] Read more.
The development of coal deposits is accompanied by negative environmental changes. In the territory of the Kizel coal basin (Perm Region, Russia), the problem of contamination of water sources by acid mine waters and runoff from rock dumps is particularly acute. Mine waters are acidic (pH 2–3), with high mineralization (up to 25 g/L) and significant content of sulfate ions, iron, aluminum, manganese, toxic trace elements (As, Co, Ni, Pb and Zn). They are formed as a result of the interaction of underground waters from flooded mines of the Kizel basin with coal and rocks of dumps with high sulfur content (15%). Uncontrolled inflow of mine water into rivers (about 22 million m3 annually) leads to significant amounts of iron and aluminum hydroxide precipitation. These precipitations are in active interaction with river water, polluting the rivers tens of kilometers downstream and are entering the Kama reservoir. Studies of alluvial precipitation can be considered as a method of control and predictors of technogenic water pollution. The mineral composition of river sediments was studied with the application of different methods, including studies of sand-gravel and silty-clayey sediments. The sandy-gravel grains in the bottom load are mainly composed by natural minerals and are represented by a significant number of particles of coal dumps, slags and magnetic spherules. The silty-clayey material, mixed with natural minerals, contains a significant number of amorphous phases with a predominance of iron-rich substances, which may actively concentrate toxic elements. The presence of jarosite, goethite, basaluminite, lepidorocite and copiapite in silty-clayey sediments are indicators of the influence of mine waters. Full article
(This article belongs to the Special Issue Pollutants in Acid Mine Drainage)
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Article
Implications of Sulfur Speciation on the Assessment of Acid Rock Drainage Generating Potential: A Study of South African Coal Processing Wastes
Minerals 2019, 9(12), 776; https://doi.org/10.3390/min9120776 - 12 Dec 2019
Cited by 1 | Viewed by 875
Abstract
The presence of sulfur in coal processing wastes can lead to environmental impacts, such as acid rock drainage (ARD). However, not all sulfur species are acid-forming, and the implications of sulfur speciation when assessing acid rock drainage potential by means of static chemical [...] Read more.
The presence of sulfur in coal processing wastes can lead to environmental impacts, such as acid rock drainage (ARD). However, not all sulfur species are acid-forming, and the implications of sulfur speciation when assessing acid rock drainage potential by means of static chemical tests are not well understood. This study set out to evaluate the implications of different sulfur forms on the assessment of acid rock drainage potential using static laboratory-scale tests and to investigate the reliability of methods for the analysis of such forms for the case of three South African coal processing wastes. Both the International Organization for Standardization (ISO) 157:1996 and Australian Coal Association Research Program (ACARP) C15034 protocols were found to be suitable tools for analyzing the different forms of sulfur. Acid-generating sulfur forms constituted between 53% and 64% of the total sulfur in the wastes evaluated, with the maximum potential acidity (MPA) and net acid-producing potential (NAPP) values calculated on the basis of acid-forming sulfur being significantly lower than those calculated on the basis of total sulfur content. Results also showed that the partial conversion of sulfur species under the relatively aggressive conditions of the acid-neutralizing capacity (ANC) and net acid generation (NAG) tests may overestimate the potential acid generating potential in the case of coal. These findings highlight the uncertainties associated with standard ARD static tests and the importance of taking sulfur speciation into account when calculating the MPA for coal processing wastes. Full article
(This article belongs to the Special Issue Pollutants in Acid Mine Drainage)
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Review

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Review
Active Treatment of Contaminants of Emerging Concern in Cold Mine Water Using Advanced Oxidation and Membrane-Related Processes: A Review
Minerals 2021, 11(3), 259; https://doi.org/10.3390/min11030259 - 02 Mar 2021
Cited by 1 | Viewed by 729
Abstract
Responsible use and effective treatment of mine water are prerequisites of sustainable mining. The behavior of contaminants in mine water evolves in relation to the metastable characteristics of some species, changes related to the mine life cycle, and mixing processes at various scales. [...] Read more.
Responsible use and effective treatment of mine water are prerequisites of sustainable mining. The behavior of contaminants in mine water evolves in relation to the metastable characteristics of some species, changes related to the mine life cycle, and mixing processes at various scales. In cold climates, water treatment requires adaptation to site-specific conditions, including high flow rates, salinity, low temperatures, remoteness, and sensitivity of receiving waterbodies. Contaminants of emerging concern (CECs) represent a newer issue in mine water treatment. This paper reviews recent research on the challenges and opportunities related to CECs in mine water treatment, with a focus on advanced oxidation and membrane-based processes on mine sites operating in cold climates. Finally, the paper identifies research needs in mine water treatment. Full article
(This article belongs to the Special Issue Pollutants in Acid Mine Drainage)
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Review
Stable Isotope Imprints during Pyrite Leaching: Implications for Acid Rock Drainage Characterization
Minerals 2020, 10(11), 982; https://doi.org/10.3390/min10110982 - 04 Nov 2020
Cited by 1 | Viewed by 697
Abstract
The characterization of acid rock drainage (ARD) is traditionally based on mineralogical and geochemical techniques (e.g., Acid Base Accounting tests). The complexity of ARD processes warrants contribution of methods from various disciplines. In the past decade, the increasing role of environmental isotopes in [...] Read more.
The characterization of acid rock drainage (ARD) is traditionally based on mineralogical and geochemical techniques (e.g., Acid Base Accounting tests). The complexity of ARD processes warrants contribution of methods from various disciplines. In the past decade, the increasing role of environmental isotopes in pollution monitoring has enabled the successful application of isotope methods in ARD investigations. While isotopic compositions of different pollutants can refer to their parent mineral, the degree of isotope fractionations are indicative of the mechanisms taking place during the release and transportation of ARD-related contaminants. In natural environments, however, the measured isotope fractionations are predominantly the result of several coexisting or sequential processes. Therefore, the identification and quantification of the distinct contributions of these processes to isotope variations is difficult and requires well-defined laboratory conditions, where the influence of ARD generation on different isotope systems can be assessed with greater certainty. This review provides readers with a single source of information regarding isotopic variations generated by laboratory pyrite leaching. Full article
(This article belongs to the Special Issue Pollutants in Acid Mine Drainage)
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