Tailings Storage Research Articles

Applying Practical Hydrogeology to Tailings Storage Facility Design and Management

Hydrogeology plays an important role in tailings storage facility (TSF) design. In this paper, we present hydrogeologic considerations for TSF design and operations and some fundamentals for site characterisation during the design phase that can help reduce the severity of groundwater-tailings interactions. Finally, we present examples of tailings-groundwater interactions from TSF design projects and active mining operations around the globe to illustrate our key points. These examples include successful applications of hydrogeologic principles during design and operations, and unexpected interactions between tailings design elements and groundwater where hydrogeology was not properly considered.

Risk assessment for tailings management

ABSTRACT Due to the severity of several major failures, the mining industry has significantly increased efforts to improve the design, construction, operation, monitoring, and management of tailings storage facilities (TSF). Best practice guidance mandates strong governance by senior executives, multi-tiered management systems, external third-party review, and the application of risk assessment to all TSF design, operation, and management activities. Tailings may be produced in slurry, thickened, or filtered form, and every TSF has its own unique site characteristics, design, and operational conditions, presenting various forms and levels of risk. Companies with large TSF portfolios must compile complex information in a manner that allows differentiation, prioritization, and communication of the risks to various stakeholders. This article updates a novel and rational tool to assess the risks associated with TSF. The tool provides the means of communicating these risks, and of prioritizing corrective actions. It also facilitates the implementation of risk-based management practices while allowing consideration of the unique conditions of a company, its organizational structure and internal practices, as well as the varied nature and characteristics of its TSF portfolio.

Reducing the negative impact of potassium ore waste of the tyubegatan potassire deposit on the environment

In the article, solutions are presented for the placement of rock salt from the excavation of mine workings during the construction of a mine in a salt dump and salt waste of the processing plant of the Dekhkanabad potash fertilizer plant in the tailing dump. The technology of anti-seepage protection of the salt dump and the brine collector was recommended, which allows to reduce the negative impact on the environment and groundwater. The recommended anti-filtration protection of the base of the salt plate includes a device 1) of a Bentomat screen, a protective layer of loams, an attachment layer, and 2) above the screen drain of geocomposite material TenCatePolyfelt DC 602E. To ensure rational use of land and safe exploitation of salt wells, landslide formation issues were considered. Mathematical descriptions of the trajectory of movement of the center of mass of a landslide, its parameters and speed of movement are described. In order to prevent landslides, experiments were carried out on salt traps to secure their surface with sodium silicate solutions. Based on the results of laboratory experiments and experimental-industrial tests, it was established that density and calcium module of the fixing solution, as well as porosity and filtration coefficient of the fixed salt waste affect the gelling time, the penetration rate of the solution and the fastening strength of the salt waste. Based on the results of the theoretical, laboratory and pilot-industrial studies of the process of fixing salt waste, a method, recipe, project and plan of measures for checking the quality of work and safety measures for the implementation of the chemical method for fixing salt waste from the Tyubegatan potash deposit were developed. The fixing solution is proposed to be applied by spraying. The flow rate of the fixing solution for fixing 1 m3 of sand is justified and the speed is established, its injection scheme is: four point-pair, diagonal-sequential. Keywords: salt dump, tailings storage, anti-filtration protection technology, reduce the negative impact on the environment and groundwater, the process of fixing salt waste, formulation, chemical method.

Some Aspects of the Geochemistry and Natural Radioactivity of the Azov Deposit Ores

The analysis of the Azov deposit of zirconium-rare earth ores as the object capable on qualitative and quantitative parameters to become key for creation and modernization of rare earth subsectors of the industry of Ukraine is carried out. On the basis of the generalized characteristics of zirconium-rare earth mineralization, conclusions were drawn regarding the nature of the increased radioactivity at the Azov deposit, which is mainly due to the presence of certain minerals in the ores. The actual radioactive minerals were found only as inclusions in zircon and do not make a significant contribution to the natural radioactivity of ores. It has been established that the radioactivity is uranium-thorium due to the inclusion of these elements in the composition of the aforementioned minerals. The results of the radiation-hygienic assessment of core samples from the deposit are presented. According to the existing standards, the enclosing rocks of the supra-ore and under-ore strata can be used in all types of construction without restrictions. The ores of the deposit are assigned to the third class in terms of the level of effective specific activity. It was found that there is a significant direct relationship between gamma activity and the total REE content in the field. There is also a correlation between the content of U and Th, the dose rate of γ-radiation and the content of the total REE. It was shown that there is no relationship between these indicators and the ZrO2 content. Analysis of the gamma-ray logs showed the possibility of confidently drawing the boundaries of the ore intervals and fixing the inter-ore intervals. The main stages of the technological process of integrated development, enrichment, processing and storage of enrichment tailings, slags and sludge, which ensure the minimum impact of production on the environment and human health, have been determined.

Risk evaluation of tailings dam-break based on the extension matter-element model

As one of the most concerned risk sources of mining enterprises, the safety and stability of the tailings storage facility (TSF) is closely connected to the operating activity, surrounding ecological environment, and residents' lives safety and properties safety. In order to evaluate the risk of the tailings dam break, the extension matter-element model has been applied in the work. First, the risk evaluation indicator system was established, included 3 levels, 4 criteria and 17 individual indicators. Next, the weight of each indicator was computed by using the analytic hierarchy process (AHP) method. Then, the classical field, controlled field and closeness function within the extension matter-element model were determined considering the TSF height and volume, and the principle of the maximum membership degree has been improved by the closeness. Finally, a case study was illustrated to demonstrate the effectiveness of the model. The result indicated that the target TSF operated at a relatively lower risk level, which accurately reflected the real operating situation. This work can provide a reasonable reference for dam break risk evaluation.

Effect of tailings storage facility on surface water at copper-pyrite deposit

Effect of tailings storage facility on surface water at copper-pyrite deposit

SPH modelling of dam breach run out flow for a site planning tailings storage facility

Tailings storage facilities (TSFs) are being built globally for containing the chief solid waste stream from mining industry. Catastrophic TSF breach accidents have occurred frequently since the beginning of the 21st century, causing severe impacts on the environment, economy and community safety. The recent example is the 2019 Brumadinho accident in Brazil that released 12 million m3 of tailings and killed more than 249 people. The foreknowledge of the TSF breach run out overland flow can be crucial to prevent or minimize possible losses. Using the Digital Surface Model (DSM) terrain data and the smoothed particle hydrodynamics (SPH) numerical method, this study proposed a procedure to predict the routings of hypothetical TSF breach run out flow over downstream complex terrain. A case study of a planning TSF site in Guizhou Province of China was carried out to evaluate its applicability. The results suggested that the maximum routing distance of the TSF breach run out flow was 1.45 km. At 240 s, the run out flow began to impact the downstream viaduct piers with the maximum submerged depth of 3.3 m and the maximum impact force of 21.8 kPa. Essential protective measures were recommended before the TSF site construction. The proposed procedure is then recommended for the safety management of the TSFs globally.

Dusting Suppression at Tailings Storage Facilities

Dusting Suppression at Tailings Storage Facilities

Arsenic Adsorption by Some Iron Oxide Minerals: Influence of Interfacial Chemistry

The dramatic increase in hydrometallurgical extraction of gold from arsenic bearing gold ores has inevitably resulted in the release of arsenic into the environment worldwide. Residual arsenic minerals in tailings storage facilities can be oxidised and mobilise arsenic into the environment. This can contaminate soils, ground and surface waters and eventually biota. In spite of well-established technologies and recent advances in arsenic remediation, there are limited knowledge and understanding of the iron oxide substrate (goethite, hematite and magnetite) mineralogy and the fate of arsenic on the surface charge of these iron oxide substrates in an aqueous media during adsorption. The aim of the present study was to investigate the influence of interfacial chemistry on arsenic adsorption onto selected iron oxide particles to assist in developing a better understanding and new knowledge in arsenic removal from contaminated waters. Bulk mineralogy and partial chemical composition of selected iron oxide minerals were obtained using quantitative x-ray diffractometry (QXRD) and acid digestion followed by metal determination using inductively coupled plasma optical emission spectrometry (ICP-OES) respectively. Zeta Potential measurements involving iron oxide particles as arsenic adsorbents were carried out to elucidate the influence of interfacial chemistry on the adsorption behavior of arsenic from solution. The study confirmed that the iron oxide minerals were predominantly hematite, magnetite and goethite with goethite containing significant amounts of quartz. Arsenic adsorption was pH dependent and strongly influenced the zeta potential and isoelectric point (IEP) of the iron oxide particles. The zeta potential of all substrates studied was strongly positive at pH 2 but indicated a reversal at pH ~ > 9. The interaction between substrates, arsenic and its hydrolysable products resulted in significant decrease in the magnitude of zeta potential and change in IEP indicating specific adsorption.
 
 Keywords: Arsenic, Adsorption, Iron Oxide Minerals, Zeta Potential

Mineral Concentrates As a Factor of the Khibiny Apatite-Nepheline Ores Efficiency Improvement

Apatite-nepheline ores of the Khibiny deposits contain the largest phosphorus-bearing resources in the world, and, at the same time, they contain associated valuable components in the rock-forming minerals — apatite, nepheline, sphene and titanium magnetite. Intensive development of the Khibiny deposits with production of only apatite concentrate and a small part of nepheline concentrate resulted in the accumulation of over 1.0 billion tons of wastes in tailing storage facilities and dumps during 90 years of JSC Apatit operation. The possibility of increasing the efficiency of the use of the main concentrates of apatite-nepheline ores of the Khibiny deposits and wastes for their processing is considered through the use of technological developments of the FRC KSC RAS, JSC RIFI and JSC Apatit to obtain traditional and new target products. A fundamentally new approach to the problem of sustainable use of natural resources is focused on establishment of the whole production chain in the region, from mining and processing operations to manufacturers of final high technology products (rare-earth products, welding and construction materials, coloring agents and other materials). They also determine the level of industrial technical progress.
 Keywords: Khibiny apatite-nepheline ores, mineral raw materials, extraction and processing, new materials

Suppression of arsenopyrite oxidation by microencapsulation using ferric-catecholate complexes and phosphate

Mineral processing, pyro- and hydrometallurgical processes of auriferous sulfide ores and porphyry copper deposits (PCDs) generate arsenopyrite-rich wastes. These wastes are disposed of into the tailings storage facilities (TSF) in which toxic arsenic (As) is leached out and acid mine drainage (AMD) is generated due to the oxidation of arsenopyrite (FeAsS). To suppress arsenopyrite oxidation, this study investigated the passivation of arsenopyrite by forming ferric phosphate (FePO4) coating on its surface using ferric-catecholate complexes and phosphate simultaneously. Ferric iron (Fe3+) and catechol form three types of complexes (mono-, bis-, and triscatecholate complexes) depending on the pH, but mono-catecholate complex (i.e.,[Fe(cat)]+) became unstable in the presence of phosphate because the chemical affinity of Fe3+—PO43– is most probably stronger than that of Fe3+—catechol in [Fe(cat)]+. When two or more catechol molecules were coordinated with Fe3+ (i.e., [Fe(cat)2]– and [Fe(cat)3]3–), however, these complexes were stable irrespective of the presence of phosphate. The treatment of arsenopyrite with [Fe(cat)2]– and phosphate could suppress its oxidation due to the formation of FePO4 coating, evidenced by SEM-EDX and XPS analyses. The mechanism of FePO4 coating formation by [Fe(cat)2]– and phosphate was confirmed by linear sweep voltammetry (LSV): (1) [Fe(cat)2]– was oxidatively decomposed and (2) the resultant product (i.e., [Fe(cat)]+) reacts with phosphate, resulting in the formation of FePO4.

The Influence of Aggregate Microstructure on Tailings Behaviour

Conventional constitutive soil models applied in geotechnical engineering have been developed using the phenomenological approach from macroscopic observations and application of continuum mechanics. Despite the adopted simplification and homogenisation of complex interactions of soil particles, water and air, the phenomenological models and the underlying principles have been proven to satisfactorily describe the stress-strain conditions in most common soils. However, the application of the conventional soil behaviour models has been proven to be difficult in the mining industry and tailings storage facilities in particular, where the structural integrity of the storage facilities often depends on the performance of extensively altered materials (tailings) that are produced as a waste product from ore processing. The difficulties stem from the altered nature of the tailings and the inconsistencies in the tailings deposition, which may result in the formation of porous and brittle matrices of heterogeneous aggregates. Such matrices are susceptible to static and dynamic liquefaction whereby little changes in the stress-strain conditions can result in a sudden collapse of the soil structure. Sampling and preservation of intact delicate tailings is often unachievable, and the analyses of the laboratory tests are obscured by the simplifications, assumed homogenisation of the sample and the inherent influence of the testing apparatus on the measured properties. Therefore, the characterisation of the in situ conditions of the tailings and the prediction of the tailings performance for altering stress-strain conditions using conventional soil behaviour models is very difficult. Yet, understanding the delicate state of the brittle tailings is crucial for upstream and centrally raised tailings storage facilities. This is exemplified by the facility failures which featured devastating consequences in Brazil in 2015 and 2019. These failures were caused by liquefaction of tailings, which acted as foundations for the upstream raised embankments. This paper discusses the influence of the tailings micro-structure on the macroscopically observed behaviour. This paper also shows that, using modern optical and other testing methods, the micro-structure can be measured and then allowed for in the soil behaviour model with the aim to improve the reliability of tailings liquefaction assessment.

Role of the bryophytes in substrate revitalization on a post-technogenic salinized territory

This work aims to investigate the role of the bryophyte cover in substrate revitalization on a post-technogenic salinized territory. The influence of the moss cover on the organic carbon content, actual acidity, redox potential, and the content of the main ecological and trophic groups of microorganisms in the substrate of the tailings storage of the Stebnyk Mining and Chemical Enterprise "Polymineral" was investigated. Bryophytes significantly affect the tailings storage saline substrates. They colonize areas with a very strong and strong degree of salinity, which are unsuitable for other plants. It was indicated that pioneer moss species promote the accumulation of organic matter in saline substrates of the tailings storage. Under moss turfs, the amount of organic carbon increased 2.2–5.0 times, compared with its content in the uncovered substrate. The high variability of the organic matter content is determined by the species characteristics of mosses, primarily their life form. The dense-turf species Didymodon rigidulus and Pthychostomum pseudotriquetrum var. bimum accumulated the most organic matter. The thickness of the litter under the moss turf of these species was much greater than in Barbula unguiculata and Funaria hygrometrica, which form loose turf. We assessed the specificity of the accumulation of organic carbon in the turfs of the studied mosses. It founded that most organic matter accumulated in the dead parts of the moss turf. In the green parts of the shoots of these moss species the amount of organic carbon was 3–4 times less, which indicates a relationship between litter capacity and content of carbon in the substrate under moss turfs. We investigated the influence of mosses on the actual acidity of the tailings storage substrate. Moss turfs promote the increase of acidity of the aqueous solution of the tailings substrate by 0.2–0.5 units. The tailings storage substrates are characterized by a reduction regime. The redox potential of the substrate under moss cover significantly depended on the species characteristics of mosses. Under the moss cover, the redox potential increased by 1.2–1.4 times, compared with the index for the substrate without moss cover. We studied the influence of moss cover on microbial biomass and the quantity of some ecological-trophic groups of microorganisms in the substrates of the tailings storage. The amount of microbial biomass under moss turfs increased depending on the degree of the substrate salinization and the species characteristics of the mosses. In areas with a very high degree of salinization under the moss turfs of Didymodon rigidulus and Funaria hygrometrica, the microbial biomass index increased almost two times, compared with the uncovered substrate. We found a significant increase in the quantity of the main ecological and trophic groups of microorganisms (saprophytes, cellulose-destroying bacteria, oligonitrophils and nitrogen fixers) in the substrate under the moss cover. Thus, pioneer moss species have a complex effect on the saline substrate of tailings storage. They accumulate organic matter, increase the acidity of the upper layer, improve the redox regime of the substrate and promote the development of soil microbiota.

Analysis and technology to reduce the impact of tailings on the ecology of local water bodies

An integral part of the technological chain in the processing of uranium ores is a tailing dump designed for organizational disposal and long-term storage of tailings. There are up to 170 production and monitoring wells around the tailings for comprehensive monitoring of the impact of the tailings on groundwater. Wastewater is discharged from the industrial site into the Aksu riverbed after preliminary complex biological treatment at the sanitary treatment facilities. This article provides an analysis of pollutants from the processing of uranium ores. Studies have found that arsenic, molybdenum, uranium, and radium are the main pollutants that affect surface and groundwater. Under the influence of precipitation, the oxidation of ore minerals, many radioactive and chemical elements transform into more mobile forms and enter the environment. The main accumulator of radionuclides is bottom sediments. It is this component of the aquatic ecosystem that determines the mechanism and rate of redistribution of radionuclides. The analysis of water samples from the tailing dump itself and from surface water bodies in the area of the GMZ industrial site in the direction of thalwegs was carried out.

The role of institutional mining investors in driving responsible tailings management

Recent devastating tailings dam failures have led many investors to view mining projects as increasingly risky investments compared with other industrial projects. In 2019, institutional investors worth US$14 trillion in assets called for the development of an independent classification system for quantifying the safety risks associated with tailings storage facilities (TSF), and played a central role in the Global Tailings Dam Portal Project disclosure request which called for a significant increase in transparency of TSF data. This paper draws upon an extensive literature review to explore the role and motivations of institutional mining investors in mitigating TSF failure risks. Results from qualitative interviews with institutional mining investors are presented to triangulate findings. It is concluded that the financial materiality of TSF failures cannot be argued to be the sole motivating factor for increased investor interest in this topic. Increasingly, the risk of TSF failure is being recognized as a critical environmental, social and governance (ESG) issue. Despite growing interest by investors to directly influence TSF management at mining sites, challenges arise due to the lack of a global tailings standard, technical training and differing regulations across jurisdictions. However, it is found that investors can also play an important role through pressuring company boards, and in improving the overall transparency of data associated with TSF risks. An outstanding research challenge lies in developing tools and frameworks to support investors to meaningfully incorporate TSF risks into investment decisions.

Sediment arsenic hotspots in an abandoned tailings storage facility, Gold Ridge Mine, Solomon Islands

Gold mining of arsenopyrite ore bodies result in waste tailings that contain elevated levels of arsenic. Disposal of these wastes in a Tailings Storage Facility (TSF) represents a substantial environmental risk if not properly managed. The Gold Ridge mine on Guadalcanal, in the Solomon Islands was abandoned from 2014 to 2018, leaving the TSF with little ongoing environmental management. Surface water quality monitoring observed a threefold increase in surface water arsenic concentrations over a 6-month period when no mining operations were occurring. This study aimed to investigate bottom sediments as the source of elevated concentrations of arsenic in the surface waters of the TSF during mine closure. This was achieved by analysing arsenic concentrations in the surface water, sediment porewaters and by quantifying sediment arsenic flux as dissolved oxygen availability declined. It was evident that bottom sediments of the TSF were the potential source of arsenic, having an average arsenic concentration of 437.9 mg kg−1. In addition, average sediment porewater arsenic concentrations across the TSF were 1.07 mg L−1, with a large central zone of highly elevated concentrations peaking at over 17 mg L−1. Long term sediment core incubations demonstrated arsenic effluxes from all sites monitored under both oxic and hypoxic conditions, ranging from 0.72 mg m−2 day−1 to 7.01 mg m−2 day−1 respectively. These results suggest that arsenic hotspots within the TSF have the capability to contribute to increased arsenic concentrations in surface waters. Management of mine TSF’s should consider these geochemical interactions that can occur in abandoned sites.

A Two-Fluid Simulation of Tailings Dam Breaching

This paper presents the development and application of a dam breach model, EMBREA-MUD, which is suitable for tailings dams. One of the common failure modes for these structures is breaching due to overtopping, which together with the flow of liquefied tailings, is simulated by the proposed model. The model simultaneously computes the outflow of water and tailings from a tailings storage facility and the corresponding growth of the breach opening. Tailings outflows are represented by a separate non-Newtonian viscous layer, which together with a water layer, represent the two fluid components of the model. The third component represents dam material that can be eroded by the shear forces exerted by either water or mud. The water layer also exerts dynamic and erosional forces and can transport solids eroded from either the mud or dam layer. The model was verified against laboratory cases as well as two field cases reported in the literature, the failures of the Mount Polley tailings dam in Canada in 2015 and the Merriespruit dam in South Africa in 1994. The model results agreed well with the recorded narrative of the events, although in the latter case, careful calibration of one of the model parameters was necessary to obtain a good match.

Assessment of environmental hazard of accumulated mineral processing waste of closed mining enterprises in the Amur river region and Primorye

The subject of research was technogenic waste systems formed in the last century due to the activities of presently closed mining enterprises in the Amur River Region and Primorye of the Far Eastern Federal District of the Russian Federation. Experimental studies allowed to establish that toxic sulphidized mineral processing waste accumulated for the 20th century in tailings storage facilities (TSF) in large quantities produce negative impact on the environment. It was revealed that their conservation and reclamation were not carried out. However, they pose huge threat not only to the environment, but also to public health. In this regard, the research goal was to assess environmental hazard of the accumulated toxic waste and substantiate the possibility of mitigating their negative impact on biosphere components and human health. Based on the research goal, the following tasks were set: 1) analysis and generalization of the existing experience of studying the problem in Russia and abroad; 2) identification of the main sources of crisis situations at closed mining enterprises, indicators and criteria for as sessing the environmental hazard of the accumulated mineral processing waste; 3) assessment of the environmental hazard of the accumulated mineral processing waste; 4) development of principles and measures aimed at ensuring environmental safety of TSF comprising toxic waste. The following methods were used: physical-chemical, bio logical, as well as mathematical modeling, GIS technologies, etc.Based on the study of the TSF current state, assessment of the level of technogenic environment pollution, and patent search, the authors substantiate the need for effective solution to this problem. It was found that the waste belongs to the second hazard class (highly hazardous). The excess of 4 to 46 times above the regional background indicators (metal concentrations), and more than 200 times above MPC was revealed. It has been proven that the TSF surface does not naturally run wild for 30 years. Patent search and our own experimental research allowed developing measures to ensure environmental safety of sulfidized tin ore processing waste, novelty of which was confirmed by patents of the Russian Federation.

The toxicity of respirable South African mine tailings dust in relation to their physicochemical properties

Introduction Decades of mining in South Africa has given rise to hundreds of tailings storage facilities (TSFs) and several tonnes of waste. These TSFs have contributed to air pollution due to the lack of proper rehabilitation measures. Currently, it is not known whether tailings emissions could be the cause of respiratory-related ill effects. In addition, the physicochemical properties that may govern their toxicity have not yet been identified. Aim The aim of this research was to determine the toxicity of tailings dust and identify the physicochemical properties likely to govern toxicity. Methods Dust samples were collected from five TSFs in the Gauteng and North West Provinces of South Africa and sieved to enrich the airborne particle fraction more likely to be inhaled. Thereafter, their physicochemical characteristics were assessed i.e. size distribution, specific surface area, shape, surface elemental composition, mineral composition, total elemental composition and surface activity. In addition, the toxicity and cellular internalization of the particles were assessed using the BEAS-2B epithelial and U937 monocytic-macrophage cell lines. Results: The results showed that all tailings dusts showed toxicity, particularly in the BEAS-2B cell line. This toxicity could have been governed by either their elemental composition, e.g. high transition elements e.g. Fe, Cu, Cr and V in the dusts from TSF 4, or a combination of other physicochemical properties, e.g. higher quartz content, lower size and higher surface area in the dusts from TSF 1. Conclusion These results provide mechanistic evidence to support future epidemiological studies attempting to link tailings dust exposure to adverse health effects.

Mechanisms at Different pH for Stabilization of Arsenic in Mine Tailings Using Steelmaking Slag

The mechanisms at different pH for the stabilization of arsenic (As) in mine tailings (MTs) using steelmaking slag were investigated using laboratory experiments. Two types of steelmaking slag were used in the experiments. Ca-slag has high pH and high calcium oxide content due to its short period of aging. In contrast, Fe-slag is oxidized for a long time and is richer in Fe than in Ca. The As-contaminated MTs were taken from a tailing-storage dam around an abandoned gold mine in Korea. The tailings had an average As concentration of 2225.3 mg/kg. The As-removal batch experiment was performed to investigate the As-removal characteristics of the steelmaking slag. From SEM/EDS analyses after each batch experiment, Ca-As bearing precipitates were broadly found on the surface of Ca-slag particles and the final pH of the solution increased to 12.3. However, for Fe-slag, the As was locally found as forms adsorbed to the surface of Fe and Mn oxides contained in the Fe-slag particles. The final pH of this solution was 8.4. The efficiency of removal of As from water using the Ca-slag was >97% and that with Fe-slag was 79%. This suggests that As ions in solution were removed by Ca-(co-)precipitation (which occurs comprehensively on the Ca-slag surface), or by restrictive adsorption of Fe- and Mn-oxides (on limited parts of the Fe-slag). To determine the efficiency of As-extraction reduction from MTs using steel slags, arsenic-extraction batch experiments with two slags were performed under acidic conditions, simulating the leaching environment formed around a mine tailing storage dam. The As concentration in the extracted solution was decreased by 69.9% (even at pH 2) after the addition of 5% Fe-slag. However, when 5% Ca-slag was added, the As concentration decreased by 42.3% at pH 2. These results suggest that Fe-rich steel slag can be more effective than Ca-rich steel slag as a stabilizer for As in contaminated mine tailings at low pH.