Search Results (64)

On the outskirts of the Pinios dam reservoir (Ilia Regional Unit, Greece), a water treatment plant serves the water supply needs of the surrounding municipalities, in which high concentrations of Fe and Mn, before treatment, have been observed. The main purpose of this research was to investigate the mechanism of increased iron (Fe) and manganese (Mn) levels in the reservoir of the Pinios dam, which impacts its water treatment plant operation. A wide range of hydrochemical and sedimentological analyses were conducted over a hydrological year, focusing on the spatial and temporal distribution of Fe and Mn in both water and sediment samples across the established research monitoring stations. Sediment samples from the reservoir’s bottom revealed predominantly fine-grained material, rich in total organic carbon, with elevated Mn and Fe oxide levels. Significant seasonal variations in Fe and Mn levels were also discovered, with higher Mn levels observed in the anoxic bottom waters of the reservoir during the dry season, attributed to the reduced conditions favoring Mn oxide dissolution over Fe. Conversely, during the wet season, a homogenization of metal concentrations throughout the water column was observed due to increased oxygenation and freshwater inflow. These outcomes were confirmed by the hydrochemical analysis, indicating that the redox conditions, pH, and temperature, as well as the presence of organic matter, significantly influence the mobility and bioavailability of these metals in the reservoir. The findings of this study clarify that the high concentration of Fe and Mn can be linked to the mineral composition of the upstream Neogene and flysch formations in the study area. As these formations are affected by geological weathering, they tend to enrich the streams, through soil erosion and runoff processes, with metals like Fe and Mn, which are eventually transported into the dam reservoir. This study highlights the critical influence of lithological, sedimentological, and hydrological factors on the redox conditions and seasonal stratification that govern the behavior of Fe and Mn concentrations and mobility in dam reservoirs. These findings are critical for informing water resource management practices and dam infrastructure operators and developing effective environmental conservation strategies in similar cases. Full article

The 2015 Fundão tailings dam collapse in Mariana, Brazil, was a major environmental catastrophe. Assessing its long-term effects on water quality is critical for environmental restoration and policy development. In this study, we reconstructed a 15-year time series of five water quality parameters to assess whether the collapse caused permanent changes. Using public data from the Minas Gerais Water Institute (IGAM), we fitted generalized additive models for location, scale, and shape to model long-term trends in turbidity, total solids, conductivity, pH, and dissolved oxygen. Predictor variables included daily precipitation and smooth functions for time and longitudinal distance along the river. As expected, turbidity and total solids increased sharply after the collapse; however, the mean values returned to pre-collapse levels within four years. Conductivity, which was already elevated pre-collapse, remained high following the passage of the tailings plume. Although we observed a tendency toward pre-collapse values, the long-term conductivity mean did not fully stabilize to previous levels. No clear patterns were observed for pH or dissolved oxygen. This study highlights the acute impact of the dam collapse on five water quality parameters in the Doce River and illustrates the river’s subsequent stabilization process, although other important and chronic impacts are still persistent. Long-term studies such as this provide valuable insights into the dynamics of fluvial systems. Full article

The water retention capacity of porous materials is crucial in various geotechnical and environmental engineering applications such as slope stability analysis, landfill management, and mining operations. Filtered tailings stacks are considered an alternative to traditional tailings dams. Nevertheless, the mechanical behaviour and stability of the material under different water content conditions are of concern because these stacks can reach considerable heights. The water behaviour in these structures is poorly understood, particularly the effects of the water content on the stability and potential for liquefaction of the stacks. This study aims to investigate the water retention and flow characteristics of compacted iron ore tailings in high columns to better understand their hydromechanical behaviour. The research used 5 m high columns filled with iron ore tailings from the Quadrilátero Ferrífero region in Minas Gerais, Brazil. The columns were prepared in layers, compacted, and instrumented with moisture content sensors and suction sensors to monitor the water movement during various stages of saturation, drainage, infiltration, and evaporation. The sensors provided consistent data and revealed that the tailings exhibited high drainage capacity. The moisture content and suction profiles were effectively established over time and revealed the dynamic water retention behaviour. The comparison of the data with the theoretical soil water retention curve (SWRC) demonstrated a good correlation which indicates that there was no hysteresis in the material response. The study concludes that the column setup effectively captures the water retention and flow characteristics of compacted tailings and provides valuable insights for the hydromechanical analysis of filtered tailings stacks. These findings can significantly help improve numerical models, calibrate material parameters, and contribute to the safer and more efficient management of tailings storage facilities. Full article

Pregnant women and children are vulnerable to vitamin A deficiency (VAD), which is often compounded by concurrent deficiencies in other micronutrients, particularly iron and zinc, in developing countries. The study investigated the effects of early-life VAD on motor and cognitive development and trace mineral status in a mouse model. C57BL/6J dams were fed either a vitamin A-adequate (VR) or -deficient (VD) diet across two consecutive gestations and lactations. Offspring from both gestations (G1 and G2) continued the same diets until 6 or 9 weeks of age. Behavioral assays were conducted to evaluate motor coordination, grip strength, spatial cognition, and anxiety. Hepatic trace minerals were analyzed. A VD diet depleted hepatic retinoids and reduced plasma retinol across all ages and gestations. Retracted rear legs and abnormal gait were the most common clinical manifestations observed in VD offspring from both gestations at 9 weeks. Poor performance on the Rotarod test further confirmed their motor dysfunction. VAD didn’t affect hemoglobin levels and had no consistent effect on hepatic trace mineral concentrations. These findings highlight the critical role of vitamin A in motor development. There was no clear evidence that VAD alters the risk of iron deficiency anemia or trace minerals. Full article

This work aims to evaluate the use of a superabsorbent polymer (SAP) to provide improvements in the handling properties of iron ore tailings (IOT). The material studied came from the magnetic separation reprocessing of the material discarded at the Gelado Dam, located in Serra dos Carajás in the state of Pará, Brazil. While the concentrate presents reasonable handling conditions, the tailings, with 61.5% iron, 15% moisture, and 39% of the mass, have high cohesiveness and adhesiveness due to their fine nature and the climatic conditions of the Amazon rainforest. However, the tailings can still be considered a product as long as the handling and transportation logistics are feasible. Thus, studies with an SAP and IOT were carried out in a bench rotating drum to promote mixing between them, and the main variables studied were the SAP dosage and the required contact time. The improvement in the physical properties of the IOT were evaluated considering the Hausner ratio, Carr index, Jenike’s flow function index, Atterberg limits, and chute angle. The superabsorbent polymer promoted a significant improvement in the state of consistency of the material, and the best performance was obtained with a dosage of 1000 g t⁻¹. As long as a suitable contact condition was promoted, a contact time of 1 min was enough to achieve the expected benefits. After dosing with the superabsorbent polymer, the material’s handling classification changed from ‘cohesive’ to ‘easy flow’, and the chute angle was reduced from 90° to levels below 60°. It was concluded that the application of the superabsorbent polymer has the potential to improve the fluidity of the material discarded in the magnetic concentration operation, allowing it to be handled throughout the production and transportation chain. The SAP appears to be an important additive for the full use of the material present in the dam (100% recovery), with both economic and socio-environmental benefits. Full article

Water from Madín Dam in Mexico has been shown to contain a wide variety of pollutants such as drugs, pesticides, personal care products and compounds that are released into the environment as waste from production processes. In this work, the effect of the main process variables on the percentage of total organic carbon (TOC) removal in water samples from the Madín reservoir was studied by applying a photo-Fenton treatment catalyzed with iron-pillared clays. The catalyst was characterized by XRD, N₂ physisorption, DRS and XPS. The sampling and characterization of the water from the Madín reservoir was carried out according to Mexican standards. The system for treatment tests was 0.1 L of reaction volume and a controlled temperature of 23–25 °C, and the reaction system was kept under constant stirring. After 4 h of treatment time under UV light, the TOC removal was 90%, and it was 60% under Vis light. The main ROS involved in the photo-Fenton process driven by UVC light were hydroxyl radicals, while hydroperoxyl radicals predominate in the Vis-light-driven process. Evidence of superoxide anion participation was not found. The toxicity of untreated and treated water was assessed on Danio rerio specimens, and it was observed to be reduced after the photo-Fenton treatment. Full article

Mine-tailing dumps are one of the leading sources of environmental degradation, often with public health and ecological consequences. Due to the complex ecosystems generated, they are ideal sites for exploring the bacterial diversity of specially adapted microorganisms. We investigated the concentrations of trace metals in solid copper (Cu) mine tailings from the Ovejería Tailings Dam of the National Copper Corporation of Chile and used high-throughput sequencing techniques to determine the microbial community diversity of the tailings using 16S rRNA gene-based amplicon sequence analysis. The concentrations of the detected metals were highest in the following order: iron (Fe) > Cu > manganese (Mn) > molybdenum (Mo) > lead (Pb) > chromium (Cr) > cadmium (Cd). Furthermore, 16S rRNA gene-based sequence analysis identified 12 phyla, 18 classes, 43 orders, 82 families, and 154 genera at the three sampling points. The phylum Proteobacteria was the most dominant, followed by Chlamydiota, Bacteroidetes, Actinobacteria, and Firmicutes. Genera, such as Bradyrhizobium, Aquabacterium, Paracoccus, Caulobacter, Azospira, and Neochlamydia, showed high relative abundance. These genera are known to possess adaptation mechanisms in high concentrations of metals, such as Cd, Cu, and Pb, along with nitrogen-fixation capacity. In addition to their tolerance to various metals, some of these genera may represent pathogens of amoeba or humans, which contributes to the complexity and resilience of bacterial communities in the studied Cu mining tailings. This study highlights the unique microbial diversity in the Ovejería Tailings Dam, including the discovery of the genus Neochlamydia, reported for the first time for heavy metal resistance. This underscores the importance of characterizing mining sites, particularly in Chile, to uncover novel bacterial mechanisms for potential biotechnological applications. Full article

Depending on the ore quality, a washing process can be conducted with the bauxite, which basically consists of scrubbing the ore and screening in order to increase the available alumina grade, i.e., the alumina extractable using the Bayer Process, and reduce the impurity content. Tailings are usually disposed of in a tailings dam in the form of a slurry, which is a mixture of solid particles and liquid, consisting mainly of ultra-fine kaolinite, making the dewatering operation challenging. To reduce the environmental impact, mining companies are studying alternative methods to dewater the tailings, and different dewatering methods are available worldwide. The use of new technologies to dewater the tailings has contributed to facing the challenges of achieving sustainable development with their disposal. The decanter centrifuges are already an option for operations for the Canadian oil sands, gold ore in Peru, and nickel in New Caledonia; they are also being tested for iron ore in Brazil. In the present work, bauxite dewatering using the decanter centrifuge was evaluated to understand more about the behavior of these materials and to investigate the effects of various process parameters on the solid recovery and solid content of the flows, using three different kinds of equipment. The results indicated that decanter centrifuges can be used to achieve a high concentration of solids in the cake, with values ranging from 60% to 80% solids per weight and a great clarification in the liquid phase (centrate) from 0 to 6% solids per weight, values which mean the solid phase is suitable for reutilization in the processing circuit. Additionally, the present work provides a better understanding of how different solid contents feed can affect the behavior of the equipment. Full article

One of the critical challenges facing the mining sector is related to the prevention and mitigation of catastrophic incidents associated with its tailing dams. As mining tailings are very heterogeneous and field characterization is expensive and complex, geotechnical properties of these materials are largely unknown. The seismic cone penetration test (SCPTu) provides a field approach to estimate a large array of geotechnical information, including the liquefaction potential of tailing dams. Yet, the exploration of strain softening behaviors in geomaterials under undrained loading, utilizing the state parameter ($\psi$) inferred from SCPTu tests initially applied to soft soils, has been often used for mining tailings. This study is concerned with the implementation of a tailing classification system which uses the ratio between the small strain shear modulus and the cone tip resistance (${\mathrm{G}}_0/{\mathrm{q}}_{\mathrm{t}}$). A series of laboratory tests was executed, and three different methodologies were adopted to assess the effects of (partial) drainage conditions based on 531.26 m of SCPTu measurements conducted at three different upstream iron ore tailing dams in Brazil. Furthermore, the ${\mathrm{G}}_0/{\mathrm{q}}_{\mathrm{t}}$ ratio is integrated with $\psi$ to assess the liquefaction tendencies of the investigated materials. The findings reveal the heterogeneous nature of the tailings, wherein indications of partial drainage are discernible across numerous records. Liquefaction analyses demonstrate that the tailings exhibit a contractive behavior in over 94% of the SCPTu data, confirming their susceptibility to flow liquefaction. Our findings are relevant for site characterization within iron ore tailing dams and other mining sites with similar geotechnical attributes. Full article

The rupture of an iron mining tailing dam in Brumadinho, Brazil, released around 10 million cubic meters of tailings, of which 1.6 Mm³ reached the Paraopeba River. In this work, a total of 30 samples from three bottom sediment cores were collected in the lower course of the Paraopeba River basin and analyzed for major, trace and rare earth elements by ICP-OES and ICP-MS. The sediments presented a range of compositions with different weathering histories, overall marked by depleted Ca²⁺, Na⁺ and K⁺ compared with the average UCC, PAAS and NASC and some advanced weathering trends. The samples presented a fractionation pattern characterized by a continuous depletion of light REEs from La to Sm and a regular decreased distribution of heavy REEs from Gd to Yb, and the Co/Th vs. La/Sc diagram indicates a predominant intermediate source. The upper samples presented the highest contents of REEs, probably due to the higher presence of iron and aluminum oxides and hydroxides, which can be related to more advanced weathering. The Al, Cu, Ni, V, Zn, Co, Mn, Ti, Fe and Si concentrations and the CF, EF and Igeo index values varied across the sediment core samples, demonstrating that there were long periods of geogenic or anthropogenic contributions. Full article

Electron backscatter diffraction (EBSD) methods are used to investigate the presence of microstructures in pyrite from the giant breccia-hosted Olympic Dam iron–oxide copper gold (IOCG) deposit, South Australia. Results include the first evidence for ductile deformation in pyrite from a brecciated deposit. Two stages of ductile behavior are observed, although extensive replacement and recrystallization driven by coupled dissolution–reprecipitation reaction have prevented widespread preservation of the earlier event. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) element maps of pyrite confirm that many pyrite grains display compositional zoning with respect to As, Co, and Ni, but that the zoning is often irregular, patchy, or otherwise disrupted and are readily correlated with observed microstructures. The formation of ductile microstructures in pyrite requires temperatures above ~260 °C, which could potentially be related to heat from radioactive decay and fault displacements during tectonothermal events. Coupling EBSD methods with LA-ICP-MS element mapping allows a comprehensive characterization of pyrite textures and microstructures that are otherwise invisible to conventional reflected light or BSE imaging. Beyond providing new insights into ore genesis and superimposed events, the two techniques enable a detailed understanding of the grain-scale distribution of minor elements. Such information is pivotal for efforts intended to develop new ways to recover value components (precious and critical metals), as well as remove deleterious components of the ore using low-energy, low-waste ore processing methods. Full article

Mineral extraction is of ultimate importance for the economies of different countries, and Brazil is one of the world’s leading producers of iron ores. Unfortunately, dams are still the main problem, mainly in Minas Gerais, especially after the Fundão Dam rupture in 2015. Additionally, there is still a massive presence of buildings built on earth throughout the Minas Gerais mining region, built from the 18th century to today. Investigating the potential of iron ore tailings (IOT) to be incorporated into traditional earthen construction techniques in regions affected by dam ruptures presents a relevant and innovative research approach. In addition, the local reuse of these sediments should be the priority. Thus, the main objective of this work was to collect, characterize, and analyze the possibilities of the application of these tailings to produce rammed earth (RE). A complete characterization analysis was performed on the samples collected at three points. To analyze the soil-IOT compatibility, representative mixtures of RE were produced, and the specific mass, compaction, and compressive strength were performed. It was observed that the IOT samples have a high silica content and that the mixtures of IOT–soil, even without cement, reached the compressive strength values of the international standards, or even above them. Full article

The modeling of metal concentrations in large rivers is complex because the contributing factors are numerous, namely, the variation in metal sources across spatiotemporal domains. By considering both domains, this study modeled metal concentrations derived from the interaction of river water and sediments of contrasting grain size and chemical composition, in regions of contrasting seasonal precipitation. Statistical methods assessed the processes of metal partitioning and transport, while artificial intelligence methods structured the dataset to predict the evolution of metal concentrations as a function of environmental changes. The methodology was applied to the Paraopeba River (Brazil), divided into sectors of coarse aluminum-rich natural sediments and sectors enriched in fine iron- and manganese-rich mine tailings, after the collapse of the B1 dam in Brumadinho, with 85–90% rainfall occurring from October to March. The prediction capacity of the random forest regressor was large for aluminum, iron and manganese concentrations, with average precision > 90% and accuracy < 0.2. Full article

The dry stacking of filtered tailings is an option to deal with safety-related issues involving traditional slurry disposition in impoundments. Filtered tailings can be compacted to pre-define design specifications, which minimizes structural instability problems, such as those related to liquefaction. Yet, comprehending the tailing’s response under various stress states is essential to designing any dry stacking facility properly. Thus, the present research evaluated the mechanical response of cemented and uncemented compacted filtered iron ore tailings, considering different molding characteristics related to compaction degree and molding moisture content. Therefore, a series of one-dimensional compression tests and consolidated isotropically drained triaxial tests (CID), using 300 kPa and 3000 kPa effective confining pressures, were carried out for different specimens compacted at various molding characteristics. In addition, changes in gradation owing to both compression and shearing were evaluated using sedimentation with scanning electron microscope tests. The overall results have indicated that the 3% Portland cement addition enhanced the strength and stiffness of the compacted iron ore tailings, considering the lower confining pressure. Nevertheless, the same was not evidenced for the higher confining stress. Moreover, the dry-side molded specimens were initially stiffer, and significant particle breakage did not occur owing to one-dimensional compression but only due to shearing (triaxial condition). Full article

Monitoring the concentration of potentially toxic elements (PTEs) in the aquatic ecosystems of the Amazon is critical to guarantee the maintenance of the ecological balance and the life quality of human populations that reside in or use these environments for survival. In this sense, many rivers in the region are dammed to form lakes for depositing mining tailings. Among these, the Gelado Project has the largest iron ore dam in the Amazon that occupies about 13.5 km² of surface area with 142 million m³ of water and tailings volume, which are currently being mined for exploration, and its upstream waters and downstream are historically used by traditional populations. Based on this, to monitor the impacts of this activity, an online system for sampling and automatic analysis of water quality, composed of three process analyzers monitoring more than 20 parameters, including the PTEs (Cd, Pb, Fe, Mn, Ni, and Cu), was installed downstream of this dam. Therefore, this short communication describes this system’s development, installation, operation, and main advantage over conventional methods. Full article