Tailings Material Research Articles

Research on Compressive Tests of Iron Tailing and Cement-Modified Earth Materials from Northwest China

The strength of earth-modified materials is an important mechanical indicator of raw soil building materials. Iron tailings are a rich mineral waste resource with basic properties similar to river sand and can be used as a modified material for raw soil construction. To increase the utilization rate of iron tailings and improve the mechanical properties of earth materials, modification of earth materials were analyzed using iron tailings and cement. Through a single lattice theory design method, 10 different blending ratios of modified earth specimens were designed, with each group comprising six 100 mm cubic specimens. Earth specimens were used as the control group and compression tests carried out under standard curing conditions, with analysis of the failure mode, compressive strength, deformation, and load–displacement curve for each specimen. Also, the reasons for specimen failures were examined, including the influence of strength, dispersion, and implications of load–displacement curves. The optimal mix ratio of modified materials was determined using frequency domain analysis method. The results showed that the load–displacement curves of materials with different material ratios were basically similar and the slope and discreteness of the curves quite different. Increased tailings and cement content improved the compressive strength of earth materials and increased the discreteness of the material. Through frequency analysis, it was obtained that when the content of tailings was 12.1%–19.5%, cement content 13.9%–19.1%, and earth 65.5%–69.9%, there was a 95% of the guaranteed rate of compressive strength of iron tailings and cement-modified earth materials between 6 and 9 MPa. Iron tailings can, thus, be used as the preferred material for modifying earth materials; single lattice theory can be used as the design method for mixing experiments, and frequency domain analysis can be an effective calculation method for optimizing mixing design. Adding cement and iron tailings to modify the raw soil formula can provide reference for the selection of basic materials for raw soil construction.

Comparison of a tailings material and a natural sand in seismic site response analyses

This article investigates the seismic response of a tailings sand material in the context of site response analysis. The computed response is contrasted with that obtained for an equivalent deposit consisting of a well-characterised natural sand. Initially, the fundamental properties of both materials are used to interpret and compare their behaviour in the framework of Critical State Soil Mechanics (CSSM). Subsequently, both materials' monotonic and cyclic responses are calibrated for an advanced bounding surface plasticity model. Finally, the impact of different calibration approaches is examined through site response analyses under a strong motion. This process identifies fundamental differences between the two geo-materials, impacting the single elements simulations, especially the accuracy of undrained cyclic triaxial tests. The site response analyses examined herein show the impact of the calibrations adopted for both materials in terms of acceleration response spectra, displacements, and excess of pore water pressures (PWP). Although a relatively deep phreatic surface is adopted, the cyclic resistance and permeability of both materials plays a dominant role in the site response characteristics, controlling the excess PWP generation and hence the non-linear behaviour in the soil deposit. Finally, parametric studies are also conducted to explore the impact of permeability of the sands in the site response.

Optimal Backfilling Materials with High Compressive Strength Based on Multiple Linear Regression

Backfilling material such as tailing (mine wastes) mixing with cement or gypsum has grown throughout the world’s underground mines. However, despite their growing popularity, the typical hydraulic and mechanical fill types utilized in many mines still exist. Deep underground mining has increased due to the lack of commercial minerals nearby. Mine wastes were considered the main part of backfilling to prevent environmental pollution, ground subsidence after mine abandonment, and mine collapse during deeper extraction phases. The cemented backfill technique is the principal technique used in underground mines, which include cement with fly ash and/or filter dust, cement with tailing material and fly ash, gypsum with fly ash, and synthetic anhydrite with fly ash and have been reviewed. It has concluded that a backfilling material must be selected based on further goals, available material near the mine site, and economic factors. This paper analyzes different backfill material mixtures to create a technique that will increase safety in underground mining conditions and foresees an appropriate formula that gives high uniaxial compressive strength. The multiple linear regression (MLR) on the collected data from the experimental works to construct the relationship between the uniaxial compressive strength (UCS) of the mixture and the components of the backfilling and the prediction formula for expected compressive strength was obtained. The results revealed that the predicted regression equation was robust and reliable to predict the (UCS) for the new components of the filling (cement (CE), filter dust (FD), water content (WC), and time (T)).

Experimental Study of Mechanical Behaviour of an RC Concrete Prepared Using M-Sand along with Chemical Admixtures

Abstract: Concrete plays a predominant role in the construction industry and a large quantum of sand is being utilized for various construction of structure. River sand has become expensive due to excessive cost of transportation from natural sources. Also, large- scale depletion of these sources creates environmental problems. So as to overcome, M- Sand can be an economic alternative to the river sand with respect to its availability, cost and environmental impact M-sand a by-product from the stone crushing unit which is released directly into environment can cause environmental pollution. And can be defined as residue, tailing or other non-voluble waste material after the extraction and processing of rocks to form fine particles. Recycling is the key component of modern waste management system and it reduce the consumption of fresh raw materials, reduce energy usage, reducing the need for conventional waste disposal and to lower greenhouse gas emission. To investigate the mechanical properties as compressive strength “Cubes” of size 150 mm x 150 mm x 150 mm are prepared, the Split tensile strength “cylinder” of size 750mm x 150 mm x 150 mm and also load deflection of beam and column are prepared and investigation should be carried out at a regular interval of 7,14 and 28 days. And also, the dynamic behavior is also studied. This present work is an attempt to use M-sand as a replacement (25%, 50%, 75% & 100%) for River Sand in M-30 Grade concrete mix.

Selective extraction of nickel and cobalt from disseminated sulfide flotation cleaner tailings using alkaline glycine-ammonia leaching solutions

Millions of tons of nickel-bearing tailings, derived from disseminated sulfide resources, has been or are being dumped as waste and the recovery of metals from these tailings is insignificant. There are no economic hydrometallurgical processes to recover valuable metals from such wastes due to their low metal recovery, their alkaline high-magnesium mineralisation, and high reagent requirement. This study presents a novel alkaline process of glycine leaching to extract nickel and cobalt from such tailings. The outcomes of the experimental tests of using an alkaline glycine-based lixiviant system to extract nickel and cobalt from a float tailing material containing 0.79 % Ni and 0.02 % Co respectively are presented in this study. A comparison between using ammonia and sodium hydroxide as pH modifiers was conducted and the leaching performance of glycine-ammonia has been found to be superior based on both metal extractions and leaching kinetics. The use of resin-in-leach (RIL) to recover Ni and Co from glycine-ammonia leaching solution enhanced Ni extraction by ∼ 10 %. Grinding of the float tailing sample to a P80 of 15 µm enhanced both Ni and Co extraction by 10–15 %. Increasing the temperature to 45 °C considerably enhanced the metal leaching at which the highest Ni and Co extractions were achieved at 88 % and 90 %, respectively. Controlling dissolved oxygen (DO) levels during the leaching significantly increased the leaching kinetics and decreased the leaching time from 48 to 24 h. QEMSCAN analysis confirmed the selectivity of the alkaline glycine-based system to leach Ni, Co and Cu over impurities such as Fe, Mn and Mg. Two conceptual block diagram flowsheets were proposed for Ni and Co extraction from the float tailings using an alkaline glycine-based leaching process, where the Ni in the original ore is mineralised in an ultramafic, highly disseminated form of pentlandite in a magnesium-rich alkaline gangue matrix.

Multi-devices field magnetic susceptibility: ‘3D’ spatialization of metallic contamination in soils and reverse correlation in carbonated context (Jebel Ressas, Tunisia)

Soil contamination linked to abandoned lead–zinc mining wastes represents a serious environmental hazard of worldwide concern, raising the need for cost-effective tools to spatialize the contaminated area and assess the risks. In worldwide industrial environments, positive correlation between magnetic susceptibility and heavy metal soil contamination is often reported and used for fast preliminary site assessments. In this study, we report monitoring of an olive grove, situated below one of the abandoned tailings dump of the former Jebel Ressas Pb–Zn mining site (Tunisia), with three different commercial susceptibilimeters (Terraplus KT10, Bartington MS2D and Geonics EM38 induction device). Integration depths of above-mentioned susceptibilimeters vary from 3 to 150 cm. Similar broad-scale magnetic susceptibility maps for the three devices emphasize the effect of topography and runoff transfer as the main mechanisms for tailings material dispersion. Very low susceptibilities (~ 10 × 10–5 SI) characterize the contaminants magnetic signal, while uncontaminated soils susceptibilities are one order of magnitude higher (100–150 × 10–5 SI). This unique case of reverse correlation between magnetic susceptibilities and contamination (Pb, Zn, Cd) trace efficiently the degree of contamination and is substantiated by further mineralogical and magnetic properties analyses showing the predominance of iron amorphous oxyhydroxides in the dump, while (titano)maghemite is the main natural magnetic carriers in the uncontaminated soils in this specific carbonated context. The Geonics EM 38, with a proper calibration procedure, reveals a performant tool increasing the depth of investigation and when combined with shallower susceptibilimeter, opens perspectives for qualitative 3D spatialization of metallic contamination.

Okorusu tailings – Part II: REE mineralisation, and oxygen and carbon isotope variations

Abstract The Okorusu carbonatite complex and the mine’s tailings dump constitute a potential resource of rare earth elements meaning lanthanides and yttrium (REY). Small (≤100 μm), hydrothermal REE fluorcarbonates (bastnäsite, parisite, röntgenite and synchysite) are the principal light REE carriers while the heavy REE and Y are primarily hosted in magmatic apatite, magmatic-hydrothermal carbonates (calcite, dolomite, ankerite) and hydrothermal fluorite. Bastnäsite and röntgenite occur as individual, liberated crystals in the tailings albeit syntaxial intergrowths of acicular parisite-synchysite-röntgenite are more common. There is a clear trend of decreasing REY contents in the magmatic carbonates over the early hydrothermal carbonates to the late hydrothermal carbonates. The lower total REY abundance in the hydrothermal carbonates is interpreted to be mainly a consequence of their limited redistribution during hydrothermal activity following the breakdown of the primary magmatic minerals and precipitation of REE fluorcarbonates. During this process hydrothermal fluids changed the isotopic composition of the Okorusu carbonatites by shifting δ13C-δ18O pairs of magmatic carbonatite (δ13C: -6.5‰ to -5.4‰; δ18O: +6.4‰ to +11.2‰) to higher values of hydrothermally modified carbonatite (δ13C: -4.2 to -2.2; δ18O: +12.0‰ to +17.5‰). The preferential presence of REY in the magmatic carbonates and to a minor degree in the hydrothermal carbonates in the Okorusu carbonatite and tailings is an important exploration tool for primary magmatic REY mineralisations. The recovery of REE fluorcarbonates can be considered in the development of the flowsheet for the planned recycling of the tailings material as a potential REY by-product.

Probabilistic Analysis of Floods from Tailings Dam Failures: A Method to Analyze the Impact of Rheological Parameters on the HEC-RAS Bingham and Herschel-Bulkley Models

The difficulty in determining the rheological characteristics of tailings inside reservoirs as well as their intrinsic variability adds uncertainty to tailings dam failures in flood studies. Uncertainty propagation in non-Newtonian hydrodynamic models stands as a great scientific challenge. This article explores the sensibility of tailings dam breach flood mapping to rheological parameters in Bingham and Herschel-Bulkley (H-B) models. The developed approach was based on the probabilistic Latin Hypercube Sampling of rheological parameters. It was automated to propagate uncertainty throughout multiple hydrodynamic simulations using the HEC-RAS v.6.1 software. Rheological parameter ranges and distributions were based on a broad bibliographic review. Bingham models were revealed to be more sensitive than H-B in terms of simulated min-max area values: for Bingham, flood areas, maximum depths, and arrival times varied by 17.9%, 9.3%, and 8.2%, respectively; for H-B, variations were 25.7%, 5.1%, and 3.9%. However, Bingham was less sensitive in terms of hydrodynamically associated probability: high probability ratios were related to a small range of simulated areas in Bingham, while H-B presented great variability. Finally, for each model, the parameters that affect uncertainty the most were identified, reinforcing the importance of determining them properly. Furthermore, the identified parameter ranges for both models should be valuable for defining variable value boundaries for flood sensitivity tests on specific tailings materials for other case studies. The automated algorithm can be used or adapted for specific tests with other hydrodynamic simulations.

Unlocking the potential of microbes: biocementation technology for mine tailings restoration - a comprehensive review.

Mine tailings contain finer particles, crushed rocks, dugout-soil, water, and organic and inorganic metals or metalloids, including heavy metals and radionuclides, which are dumped as waste or non-economic by-products generated during mining and mineral processing. These abundant and untreated materials seriously threaten the environment, human health, and biodiversity because of the presence of heavy metals, radionuclides, and associated primary and secondary toxic components, including the risk of tailings dam failures. Biocementation technology, which involves the use of mining microbes to secrete cement-like materials that bind soil particles together, is a promising approach to restore mine tailing sites and reduce their mobility and toxicity. However, there is a lack of literature on the combined interactions among mining microbes, tailings residues, biocementation, and low-carbon cement (LCC) prospects. This comprehensive review article explores the prospects of mining microbes for mine tailings restoration using biocementation technology, the key influencing factors and their impact, mechanisms and metabolic pathways, and the effectiveness of biocementation technology in restoring mine tailings sites. In addition, it reviews the utilization of mine tailings materials as an alternative source of cement or construction materials for LCC technology. Furthermore, this review highlights the important issues, challenges, limitations, and applications of biocementation technology for mine tailings rehabilitation. Finally, it provides insights for future research and implementation of biocementation for mine tailings restoration and utilization of tailing materials in the industrial sector to reduce carbon emissions/footprints and achieve net-zero goals.

Study on the Liquefaction Mechanism of Mixed-Size Tailings Material Based on Grain Contact State Theory

Tailings ponds serve as high-potential energy structures designed to store waste tailings and other industrial materials. However, they can give rise to significant environmental pollution and pose a substantial threat to social and economic development, as well as the safety of people’s lives and property. Seismic disasters can cause liquefaction of tailings, leading to destabilization and dam failure of tailings ponds, and the evolution of dynamic pore pressure of tailings can indirectly reflect the destabilization process of tailings ponds. Fine grain content is one of the main factors affecting the dynamic strength and pore pressure development of tailings. This article studies the microscopic characteristics of tailings material through microscopic observation, triaxial testing, discrete element simulation, and grain contact state theory, aiming to analyze the influence mechanism of fine grain content on the micromechanics of tailings. Based on the grain contact state theory, the tailings with different fine grain contents are classified into three types: coarse grain tailings, intermediate-size grain tailings, and fine grain tailings, and the grain contact is classified into four different states. In contact state 1, the vibration pore pressure exhibits a “fast-stable” development mode with increasing vibrations. In contact state 2 or 3, the vibration pore pressure develops linearly with vibrations. For contact state 4, the development of vibration pore pressure presents a “fast-stable-sharp” development mode. The effect of fine grain content (FC) on the liquefication of the tailings studied in the present work is as follows. When the fine grain content is FC<30%, the liquefaction resistance of the tailings decreases with the increase of FC. When FC>30%, the liquefaction resistance increases with the increase of FC. When FC=30%, the liquefaction resistance is the lowest, indicating that the critical threshold of the fine grain content of the tailings studied in the present work is FCth=30%.

Effect of particle size and particle size distribution on the post-liquefaction strength of granular soils

In practice, post-liquefaction strength is largely determined from case histories, but the case history database is limited and there are gaps in the information available in each case. As a result, laboratory tests have continued to play a key role in determining how various factors influence post-liquefaction strength. This paper presents an investigation into how factors such as particle size, particle size distribution, fines content, and compressibility influence post-liquefaction strength in simple shear tests. Eleven particle size distributions of a natural soil and a tailings material, ranging from silt to fine gravel, were studied. The results were compared with case histories.Materials of different geologic origins have meaningfully different post-liquefaction strengths. Particle size and particle size distributions were both found to significantly affect post-liquefaction response as well. Post-liquefaction strengths obtained from simple shear tests agreed well with those back calculated from case histories. Laboratory testing can be utilized to determine how the post-liquefaction strength of a given material may compare to the case history database, and can be used to guide design decisions. This is an important practical finding, given the sparse case history database.

Searching for the relationship between the temperature and humidity of tailings material by processing digital photographs of laboratory experiments and color models

Relevance. Tailings beach surface dries and deflates, which intensifies the dusting process, results in ecosystems disruption on the adjacent territories, and adversely impacts health of population. The use of digital photographs, including those obtained with the help of unmanned aerial vehicles, seems to be promising in terms of reagents application simplification and dusting minimization. Research objective is to determine the quantitative relationship between the temperature and humidity of tailings materials by analyzing the digital photographs of laboratory experiments using RGB and Lab methods. Methods of research. Standard equipment was used to perform a laboratory experiment to determine the temperature and humidity of tailing dump surface layer samples. Digital photographs were taken in natural light and UV light. At the first stage, the images were processed to obtain the values of the components of two color models, RGB (redness and saturation indices were calculated) and Lab (the color difference index was calculated, two standards of black and white were used). At the second stage, as a “zero” approximation, the simplest (linear) analytical dependence between temperature and humidity was studied. Results and analysis. The coefficients of calculated linear dependences are compared with the corresponding coefficients of direct experimental data processing. It is shown that in natural light: the smallest deviations for the dependence of temperature on humidity correspond to the redness index in the RGB method and the black standard in the Lab method; the smallest deviations for the dependence of humidity on temperature correspond to the saturation index in the RGB method and the black standard in the Lab method. It is shown that in UV light: the smallest deviations for the dependence of temperature on humidity correspond to the saturation index in the RGB method and the black standard in the Lab method; the smallest deviations of the dependence of humidity on temperature correspond to the redness index in the RGB method and the white standard in the Lab method. Conclusions and scope. The mentioned indices and colors of standards can be recommended when processing similar laboratory experiments and natural studies directly on the dusting site.

Use of limekiln dust in the stabilization of heavy metals in Ghanaian gold oxide ore mine tailings.

Remedial action for heavy metal-contaminated soils is imperative for preventing heavy metal leachability and minimizing environmental risks. This study evaluated the use of limekiln dust (LKD) as a heavy metal stabilization agent for Ghanaian gold mine oxide ore tailing material. Heavy metal-laden tailing material (Fe, Ni, Cu, Cd, and Hg) was collected from a tailing dam site in Ghana. Stabilization was done using acid neutralization capacity (ANC) and citric acid test (CAT) while all chemical characterization was done using X-ray fluorescence (XRF) spectroscopy. Various physicochemical parameters including pH, EC, and temperature were also measured. The contaminated soils were amended with LKD in doses of 5, 10, 15, and 20 wt.%. The results revealed that the contaminated soils had concentrations of heavy metals above FAO/WHO stipulated limits of 350, 35, 36, 0.8, and 0.3mg/kg for Fe, Ni, Cu, Cd, and Hg, respectively. After 28days of curing, 20 wt.% of LKD was found to be appropriate for the remediation of the mine tailings of all the heavy metals studied except Cd. Ten percent of the LKD was noticed to be enough in remedying soil contaminated with Cd since the Cd's concentration reduced from 9.1 to 0.0mg/kg with a stabilizing efficiency of 100% and a leaching factor of 0.0. Therefore, remediation of contaminated soils of Fe, Cu, Ni, Cd, and Hg with LKD is safe and environmentally friendly.

Strength and suction development of nano-cemented paste tailings materials

This paper presents an experimental study of the strength and suction development of cemented paste backfill (CPB), which is an innovative cementitious construction material for mining (made by recycling mine waste into a construction material), and modified with nanoparticle (NP) additives. The effects of different amounts of four types of NP additives, including nano-silica (SiO2), nano-calcium carbonate (CaCO3), nano-iron oxide (Fe2O3), and nano-aluminum oxide (Al2O3), on the key engineering properties of CPB are investigated. An ether-based polycarboxylate superplasticizer (SP) is added to the backfill to help the NPs to better disperse in the mixture. Ordinary Portland cement is used as the binder in the CPB mixture. Uniaxial compressive tests (UCS) are conducted to determine the strength of the CPB, while suction monitoring experiments are performed to evaluate changes in suction with time. To understand the effects of the NP additives, different microstructural analyses and tests, including thermal analyses (thermogravimetry (TG), differential thermogravimetry (DTG)), mercury intrusion porosimetry (MIP), and X-ray diffraction (XRD) are conducted on the nano-CPB and the cement paste of nano-CPB. The results indicate that the addition of NP additives in the absence of SP results in lower strength due to high likelihood of agglomeration. In contrast, samples with SP and NP additives show a higher UCS and more suction than the control sample at the early ages of curing. It has been observed that the addition of NP additives results in the generation of more hydration products which enhance the interparticle friction and packing density of the CPB structure. Higher strength is obtained by increasing the SP content (0.25%) with the same NP content (1%). Enhancement of the strength of CPB and increase in suction, particularly at early ages, can have great importance in speeding up the mining cycle and thus increasing mining productivity, which is obviously associated with financial benefits to the mine.

Constitutive modelling of unsaturated gold tailings subjected to drying and wetting cycles

AbstractThe strength and deformation properties of tailing materials are strongly affected by their hydromechanical history including the cycles of desiccation and re‐saturation they undergo due to the often layered deposition process. The current study reviews the fundamental characteristics of some of the commonly used constitutive models for partially saturated soils, namely Barcelona Basic Model (BBM), Glasgow Coupled Model (GCM), and a dilatancy‐based model by Buscarnera and Nova Model (BNM) in predicting the hydromechanical response of tailing materials. In particular, we investigate the strength and shortcomings of each model and compare their capability of capturing the salient trends during drying/wetting cycles, as well as during shearing. Based on comparison with experimental data, modifications are suggested for the models, specifically related to a realistic formulation of the water retention curve and its hysteresis. The results point to a potential trade‐off in the accuracy of the constitutive models in capturing the volumetric responses during the drying/wetting cycles on one hand, and the stiffness and strength characteristics during the shearing phase on the other.

Analysis of the Dynamic Stability of Tailing Dams: An Experimental Study on the Dynamic Characteristics of Tailing Silt

With the improvement in tailing mining-grade requirements and in mineral processing technology, tailing materials tend to be fine-grained. Under the action of earthquakes, a tailing dam is prone to liquefaction, which endangers the safety and stability of the dam. To further explore the dynamic properties of tailing silt under cyclic stress, through a series of dynamic triaxial experiments, we investigated the growth of the hysteresis curve, the development of pore pressure, and the energy dissipation law of tailing silt. The experimental findings indicated that increasing the density of the sample significantly improves its liquefaction resistance and the pore pressure development curve can be fitted using the BiDoseResp function. At the same cyclic stress ratio, the sample’s anti-liquefaction strength did not rise monotonically with increasing confining pressure but changed variably at values near a specified low confining pressure; when the sample density rose under the same settings, the specific confining pressure reduced. We also further discussed the evolution law of the stress–strain curves of tailing silt. The results further explored the dynamic characteristics of tailing silt, which can provide some reference for the seismic design and reinforcement measures of many fine-grained tailing dams.

Coupling microbial and abiotic amendments accelerates in situ remediation of bauxite residue at field scale

Bauxite residue is a highly saline-sodic tailings material formed as a by-product of the Bayer process for alumina production. In situ remediation of bauxite residue has the potential to provide an effective means for accelerated rehabilitation of residue storage areas. However, previous work has predominantly only used chemical and physical amendments to date, limiting rates of pH neutralisation and extent of remediation. Combining these abiotic amendments with recently developed microbial biotechnology for pH neutralisation may transform bauxite residue into a productive soil material in a shorter timeframe. Here we investigated the effects of microbial and abiotic amendments (compost plus tillage), both in isolation and combined, on remediation of key bauxite residue properties in field scale trials (10 × 15 m × 2 m deep field plots). Triplicate residue samples were collected to 30 cm depth from each plot in quarterly field sampling campaigns. Changes in chemical and physical properties were monitored to assess remediation performance under different amendments. After one year, field plots amended with a microbial treatment had significantly (p < 0.05) lower average pH (8.99–9.46) in the upper 20 cm than the control (10.3). The combined microbial-abiotic treatment also had improved physical structure, higher organic C and lower electrical conductivity than the microbial treatment alone. The strong performance of the microbial-abiotic treatment is attributed to the combined benefits of bioneutralisation from microbial fermentation products, enhanced leaching of alkaline pore water and salts due to tillage and compost, and addition of highly stable C and N in compost. Combining novel microbial biotechnology with common abiotic amendments is therefore suggested for accelerating in situ remediation progress towards a material amenable for plant growth.

Geochemical and mineralogical investigation of cemented crusts in the tailings cover at Long Lake Gold Mine, Sudbury, Canada

In mine tailings, precipitation of secondary minerals may cement the tailings material and form cemented crusts or hardpans. Hardpans typically form beneath the surface of reactive tailings. However, at the former Long Lake Gold Mine near Sudbury, Ontario, cemented crusts formed in a clean sand cover above the tailings. We applied mineralogical and geochemical techniques to investigate the formation of these cemented crusts. Representative samples were collected from the sand cover and vertical cores from the underlying tailings. Elevated concentrations of arsenic (As), iron (Fe), and sulfur (S) in the sand cover indicate the upward transport of sulfide-mineral oxidation products. The shallow porewater of the tailings is acidic (pH 4 – 6) and contains elevated concentrations of As (up to 346 mg/L), Fe (up to 1844 mg/L), and SO4 (up to 12,000 mg/L). Mineralogical observations indicate that primary sulfide minerals in the near-surface tailings display moderate to strong oxidation, and secondary Fe-arsenate and jarosite minerals are formed both in the near-surface tailings and the sand cover. Upward migration of sulfide-mineral oxidation products leads to the formation of cemented crusts, which with continuing erosion, represent a long-term source of pollution to the surrounding environment.

Environmental and Health Risk Assessment Due to Potentially Toxic Elements in Soil near Former Antimony Mine in Western Serbia

Background: Anthropogenic activities have clearly affected the environment, with irreversible and destructive consequences. Mining activities have a significant negative impact, primarily on soil, and then on human health. The negative impact of the first mining activities is represented even today in the soils of those localities. Research shows that, for different types of mines, the concentrations of potentially toxic elements (PTEs) are high, especially in antimony, multi-metal and lead–zinc mines, which have adverse effects on the environment and then on human health and the economy. A large flood in 2014 in Western Serbia resulted in the breaking of the dam of the processed antimony ore dump of the former antimony mine, causing toxic tailings to spill and pollute the downstream area. Due to this accident, tailings material flooded the area downstream of the dump, and severely affected the local agriculture and population. Methods: Potentially toxic elements content, pollution indices and health indices were determined in soil samples from the flooded area, using referenced methodologies. The sources and routes of pollutants and risks were determined and quantified using statistical principal component analysis, positive matrix factorisation, and a Monte Carlo simulation. Results: The main source of As, Cd, Hg, Pb, Sb and Zn in the upper part of the study area was the tailing material. Based on the pollution indices, about 72% of the studied samples show a high risk of contamination and are mainly distributed immediately downstream of the tailings dump that was spilled due to heavy rainfall. Conclusions: Although the content of the PTEs is high, there is no non-carcinogenic risk for any PTEs except As, for which a threshold risk was determined. There is no carcinogenic risk in the study area.

Environmental Impact Assessment of the Subsurface in a Former W-Sn Mine: Integration of Geophysical Methodologies

Associated with the exploitation of metallic minerals in Europe during the 20th century, several mining areas were abandoned without adequate environmental intervention. Furthermore, these areas lack studies to characterize the impact of pollution on the hydrogeological system. The area surrounding the tungsten mine of Regoufe, in northern Portugal, is one such area exploited during the Second World War. The accumulation of sulfide-rich tailings may have caused an acid mine drainage (AMD), where the leaching processes caused by seepage water led to soil contamination, evidenced by its acid character and anomalous concentrations of some Potentially Toxic Elements (PTE) reported in previous studies. The present research proposes an innovative approach that seeks the integration of different geophysical techniques to characterize the impact of mining activity on the subsurface. Electrical resistivity (ER) and electromagnetic (EM) were used to measure subsurface electrical properties. In addition, seismic refraction and Multichannel Analysis of Surface Waves (MASW) were performed to characterize the geometry, depth, and geomechanical behavior of the soil and rock bodies. The integration of these techniques allowed the interpretation of hydrogeological sections and a 3D resistivity volume to gain insight into the distribution of potentially contaminating fluids and tailings material present in the mining valley.