Floods from tailings dam failures

Experimental Study on Tailings Deposition Distribution Pattern and Sedimentation Characteristics

Tailings pond accidents frequently occur during an extended period, resulting in loss of life and property, wastage of resources, and environmental pollution. Relying on tailings pond engineering, this paper carried out sample particle fragmentation experiments and settling column experiments to explore the deposition distribution pattern of tailings in both horizontal and vertical directions as well as the impact of particle size distribution on the sedimentation stratification effect. The results show that the median particle size on the dry beach surface in the horizontal direction slowly decreased with the increase in the distance from the subdam. The particle size of tailings showed great fluctuations in the vertical direction, which gradually became finer with the increase in the depth overall. At the same time, saturated sedimentation experiments suggested the inconsistent variation rule with the field test, namely, coarse on the bottom and fine at the top, and the change in particle size greatly affected the tailing sedimentation stratification effect. With the increase in fine particle content in tailings, the appearance time of the water-sand interface was shortened to within 30 min, but the sedimentation and consolidation completion times were delayed to about 1400 min. The settling column results indicate that the increase in fine particle content gradually weakened the sedimentation stratification effect, and the sedimentation pattern transformed from independent sedimentation to floc-type average sedimentation, which led to the enhanced water-retaining property of the settled layer. This may lead to an increase in the saturation line and a decrease in the length of the dry beach, seriously affecting the safe operation of the tailings pond. The research results provide some theoretical guidance and basic data for analyzing the consolidation efficiency of tailings and the stability of the tailings pond.

Analysis of Uncertainty and Sensitivity in Tailings Dam Breach-Runout Numerical Modelling

Tailings dam breaches (TDBs) and subsequent flows can pose significant risk to public safety, the environment, and the economy. Numerical runout models are used to simulate potential tailings flows and understand their downstream impacts. Due to the complex nature of the breach-runout processes, the mobility and downstream impacts of these types of failures are highly uncertain. We applied the first-order second-moment (FOSM) methodology to a database of 11 back-analyzed historical tailings flows to evaluate uncertainties in TDB runout modelling and conducted a sensitivity analysis to identify key factors contributing to the variability of the HEC-RAS model output, including at different locations along the runout path. The results indicate that prioritizing resources toward advancements in estimating the values of primary contributors to the sensitivity of the selected model outputs is necessary for more reliable model results. We found that the total released volume is among the top contributors to the sensitivity of modelled inundation area and maximum flow depth, while surface roughness is among the top contributors to the sensitivity of modelled maximum flow velocity and flow front arrival time. However, the primary contributors to the sensitivity of the model outputs varied depending on the case study; therefore, the selection of appropriate rheological models and consideration of site-specific conditions are crucial for accurate predictions. The study proposes and demonstrates the FOSM methodology as an approximate probabilistic approach to model-based tailings flow runout prediction, which can help improve the accuracy of risk assessments and emergency response plans.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10230-024-00970-w.

Spatial distribution characteristics, risk assessment and management strategies of tailings ponds in China

The tailings ponds (TPS) stemming from mineral resource exploitation are becoming a global challenge due to their high hazards and pollution to the surrounding area. However, previous studies on China's tailings ponds have either focused on a single or few areas, or the number of tailings ponds varies greatly. A systematic assessment of the number, distribution characteristics, potential risks and management strategies of the tailings pond in China is lacking. This study obtained the latest list of tailings ponds in China up to the end of 2022 based on official information and assessed their spatial distribution characteristics, environmental risk and management strategies simultaneously. The results demonstrated that the distribution of TPS in China is relatively clustered and multiple factors affected the spatial distribution of TPS in China, which were concentrated in areas with low economic and population density, convenient transportation, and a developed water system. The risk assessment suggested that 1803 TPS had large or significant environmental risks, which were mainly distributed in Yunnan, Hunan, Shaanxi and Jiangxi provinces. To solve the problem of tailings ponds from the source, the key point of tailings pond management in China should be adjusted from the prevention of pollution or dam break accidents to the full resource utilization of tailings. In summary, this study will provide a scientific basis for the risk control of TPS and an innovative idea for the management of other solid waste.

Assessment of environmental pollution and human health risks of mine tailings in soil: after dam failure of the Córrego do Feijão Mine (in Brumadinho, Brazil)

The dam failure of the Córrego do Feijão Mine (CFM) located in Minas Gerais State, Brazil, killed at least 278 people. In addition, large extensions of aquatic and terrestrial ecosystems were destroyed, directly compromising the environmental and socioeconomic quality of the region. This study assessed the pollution and human health risks of soils impacted by the tailing spill of the CFM dam, along a sample perimeter of approximately 200 km. Based on potential ecological risk and pollution load indices, the enrichments of Cd, As, Hg, Cu, Pb and Ni in soils indicated that the Brumadinho, Mário Campos, Betim and São Joaquim de Bicas municipalities were the most affected areas by the broken dam. Restorative and reparative actions must be urgently carried out in these areas. For all contaminated areas, the children's group indicated an exacerbated propensity to the development of carcinogenic and non-carcinogenic diseases, mainly through the ingestion pathway. Toxicological risk assessments, including acute, chronic and genotoxic effects, on people living and working in mining areas should be a priority for public management and mining companies to ensure effective environmental measures that do not harm human health and well-being over time.

Thermogravimetric and spectroscopic analyses along with the kinetic modeling of the pyrolysis of phosphate tailings

The present study aimed to understand the pyrolysis characteristics of phosphorus tailings and promote the resource utilization of phosphorus tailings. Thermogravimetry was combined with Fourier transform infrared spectroscopy-Raman spectroscopy-mass spectrometry (TG-FTIR-RS-MS) and kinetic models to investigate the possible reaction mechanisms during the pyrolysis of phosphorus tailings and the changes in the release characteristics of pyrolysis volatiles. The results showed that the pyrolysis process occurred in three different stages. First, small amounts of adsorbed water were removed, and organic matter in the tailings was decomposed. Second, CaMg(CO₃)₂ underwent thermal decomposition to produce CaCO₃, MgO, and CO₂. Third, CaCO₃ further decomposed into CaO and CO₂. Similarly, the pyrolysis kinetics were divided into three intervals based on the differences in their activation energy values. The pyrolysis reaction mechanism functions were two-dimensional diffusion (Valensi model), nucleation and growth (Avrami-Erofeev, n = 1/2), and nucleation and growth (Avrami-Erofeev, n = 1/4). The gases released during the pyrolysis of phosphate tailings were mainly CO₂, F₂, and HF.

Acid rain-dependent detailed leaching characteristics and simultaneous immobilization of Pb, Zn, Cr, and Cd from hazardous lead-zinc tailing

In acidic medium, hazardous heavy metals of lead-zinc tailing (LZT) are easily leachable and mobilizable. Thus, the hazard, amount, form, and complexity of the leached heavy metals under acidic precipitation become a major environmental concern. This work investigates the gangue minerals, toxicity, speciation, leaching characteristics of heavy metals in LZT under simulated acid rain, as well as immobilization effects and mechanisms using a sustainable binder. In LZT, dolomite, quartz, calcite, and muscovite are the main gangue minerals, tiny hazardous metallic minerals were absorbed in the surface. The results revealed that Pb, Zn, Cr, and Cd were the predominant harmful elements, particularly Pb and Zn. Zn is leached completely and is the concerned hazardous element under simulated acid rain. In the acid rain neutralization ability test, the amount of leachable Pb, Cr, Ca, and Si maintained in equilibrium, leached Zn, Cd, Al, and Mg depended on the addition of acid. Pb and Ca were sedimented in residues. Immobilization of Pb, Zn, Cr, and Cd depended on the stability of Ca(OH)₂/C-S-H of hydrates, and 70% LZTHP after curing 7 days can be used for some practical engineering projects. This work opens up deeply understandings for the leached heavy metals under acidic precipitation and improves the sustainable and safe in the field of immobilization of heavy metals.

Mental Health Services Utilization by the Population That Suffered Water Supply Interruption Following Mariana Dam Failure (Brazil)

OBJECTIVE

Disasters may have major impacts to mental health and to the utilization of mental health services (MHS). Moreover, these effects may be worsened by the preclusion of access to basic services following the event. The aim of this study is to evaluate the utilization of public MHS by the population that suffered water supply interruption following the Mariana Dam Failure in Brazil, 2015.

METHODS

We conducted an Interrupted Time Series analyzing secondary health data from the municipalities that faced water supply interruption, comparing it to data from the other municipalities of Minas Gerais state.

RESULTS

We found a higher immediate (RR: 1.78; 95% CI: 1.25-2.53) and gradual (RR: 1.05; 95% CI: 1.03-1.06) change in the rate of mental health visits (MHV) in the affected population following the event, whereas there was an immediate fall (RR: 0.41; 95% CI: 0.29-0.59) followed by a higher gradual increase (RR: 1.04; 95% CI: 1.02-1.06) in the rate of hospital admissions (HA) in the affected population.

CONCLUSION

The results suggest that there was an increase in the utilization of public MHS by the population that suffered water supply interruption following the disaster.

An integrated study of the plankton community after four years of Fundão dam disaster

Mining activities can affect the environment either by the tailings releasing or dams failures. The impact of the tailings can last decades and cause chronic effects due to their toxicity. The Fundão dam collapse, a relevant environmental disaster, occurred in November 2015 in Southeastern Brazil. Tailing rich in metals reached the Doce River and arrived in the Atlantic Ocean. Previous studies revealed the acute impact of the tailings in the marine planktonic community near the Doce River mouth. The current study aims to characterize the structure of planktonic assemblages in the impacted area after four years of the disaster. Sampling occurred in November 2018, January, April, and July 2019 at 32 stations located at the marine coastal area near the Doce River mouth. Our study detected high metal concentrations in the surface waters during January 2019, when the lowest diversity and abundance of phytoplankton, lowest zooplankton diversity, and low ichthyoplankton abundance were recorded. The zooplanktonic community was structured by environmental parameters and ichthyoplankton assemblages in November 2018, January and April 2019. Nutrients and metals, mainly iron from the tailing carried by the Doce River waters to the marine environment changed the plankton community, confirming the impact of the Fundão Dam collapse in the coastal area near the Doce River mouth. The phytoplankton community, influenced by the nutrients and to a lesser extent metals concentrations, was not decisive in the zooplankton community structure. The environmental variability was driven by the meteoceanographic conditions and the Doce River flow. There was a high correlation between the zooplanktonic community and ichthyoplanktonic assemblage and the environmental factors and metals. These relations indicate the impact of the tailings from the collapse of the Fundão Dam on these communities, even after four years of the Mariana disaster.

Desastres em barragens de mineração como riscos sistêmicos

RESUMO: Entre 2015 e 2019, o Brasil registrou os dois mais graves desastres envolvendo barragens de mineração do século XXI. O objetivo deste artigo é oferecer a compreensão desses desastres como riscos sistêmicos, que envolvem desde processos globais e nacionais relacionados aos determinantes sociais que se concretizam em um complexo sistema de barragens distribuídas pelo País com seus riscos intrínsecos. Quando ocorrem, resultam em um conjunto de impactos com potencial de danos e efeitos imediatos combinados com impactos secundários e terciários que podem desencadear reações em cadeia, promovendo fatores de riscos de ocorrência heterogênea e complexa. Abordar esses eventos com base no conceito de risco sistêmico permite uma compreensão mais ampla tanto da singularidade de cada um desses desastres e seus múltiplos processos de exposição, riscos e doenças, como também das características estruturais com que os processos e dinâmicas sociais, políticas e econômicas reproduzem, em múltiplos territórios, um padrão comum de desastres e seus efeitos. Concluímos que a promoção da saúde da população e de territórios sustentáveis deve orientar a organização dos processos produtivos e não o contrário, com a externalização dos custos humanos, ambientais e sociais da mineração e seus desastres.

Mining dams disasters as systemic risks

ABSTRACT: Between 2015 and 2019, Brazil recorded the two most serious disasters involving mining dams of the 21st century. The purpose of this article is to offer an understanding of these disasters as systemic risks. They involve from global and national processes related to social determinants that materialize in a complex system of dams distributed throughout the country with their intrinsic risks. When they occur, result in a set of impacts with potential damage and immediate effects combined with secondary and tertiary impacts that can trigger chain reactions, which promote risk factors of heterogeneous and complex occurrence. Approaching these events from the point of view of systemic risk allows for a broader understanding of both the singularity of each of these disasters and their multiple exposure, risk and disease processes, as well as the structural characteristics in which social, political processes and dynamics and economic factors reproduce in multiple territories a common pattern of disasters and their effects. We conclude that the promotion of population health and sustainable territories should guide the organization of production processes and not the opposite, with the externalization of human, environmental and social costs of mining and its disasters.

Towards Zero Solid Waste in the Sedimentary Phosphate Industry: Challenges and Opportunities

The phosphate industry produces huge volumes of waste (hundred million tons per year). These wastes are generally surface landfilled, leading to significant environmental impacts and a large footprint. The current practices of phosphate waste management, the typology of the waste streams and their characteristics, and finally their potential applications are reviewed. All the waste streams generated during the life cycle of phosphoric acid production going from the extraction of phosphate rock to its enrichment and transformation are considered. Great circularity opportunities have been identified and they aim (i) to recover the residual phosphorus and other critical minerals and metals, and (ii) to consider phosphate wastes as alternative resources in the civil engineering and building sectors. The purpose is to shift from linear thinking to circular thinking where synergy between different mining and other industries is highly encouraged. By doing so, opportunities to safeguard natural resources and to minimize the environmental and societal impacts are limitless. However, many challenges are still limiting this shift: economic and technical constraints, societal and policy-makers’ awareness, regulation harmonization and finally knowledge gaps. More efforts and investment in research and development are still required to reach the zero-waste target.

Release of trace elements during bioreductive dissolution of magnetite from metal mine tailings: Potential impact on marine environments

Adverse impacts of mine tailings on water and sediments quality are major worldwide environmental problems. Due to the environmental issues associated with the deposition of mine tailings on land, a controversial discussed alternative is submarine tailings disposal (STD). However, Fe(III) bioreduction of iron oxides (e.g., magnetite) in the tailings disposed might cause toxic effects on coastal environments due to the release of different trace elements (TEs) contained in the oxides. To study the extent and kinetics of magnetite bioreduction under marine conditions and the potential release of TEs, a number of batch experiments with artificial seawater (pH 8.2) and a marine microbial strain (Shewanella loihica) were performed using several magnetite ore samples from different mines and a mine tailings sample. The elemental composition of the magnetite determined in the tailings showed relatively high amounts of TEs (e.g., Mn, Zn, Co) compared with those of the magnetite ore samples (LA-ICP-MS and EMPA analyses). The experiments were conducted at 10 °C in the dark for up to 113 days. Based on the consumption of lactate and production of acetate and aqueous Fe(II) over time, the magnitude of Fe(III) bioreduction was calculated using a geochemical model including Monod kinetics. Model simulations reproduced the release of iron and TEs observed throughout the experiments, e.g., Mn (up to 203 μg L^-1), V (up to 79 μg L^-1), As (up to 17 μg L^-1) and Cu (up to 328 μg L^-1), suggesting a potential contamination of pore water by STD. Therefore, the results of this study can help to better evaluate the potential impacts of STD.

Review of Historical Dam-Break Events and Laboratory Tests on Real Topography for the Validation of Numerical Models

Dam break inundation mapping is essential for risk management and mitigation, emergency action planning, and potential consequences assessment. To quantify flood hazard associated with dam failures, flooding variables must be predicted by efficient and robust numerical models capable to effectively cope with the computational difficulties posed by complex flows on real topographies. Validation against real-field data of historical dam-breaks is extremely useful to verify models’ capabilities and accuracy. However, such catastrophic events are rather infrequent, and available data on the breaching mechanism and downstream flooding are usually inaccurate and incomplete. Nevertheless, in some cases, real-field data collected after the event (mainly breach size, maximum water depths and flood wave arrival times at selected locations, water marks, and extent of flooded areas) are adequate to set up valuable and significant test cases, provided that all other data required to perform numerical simulations are available (mainly topographic data of the floodable area and input parameters defining the dam-break scenario). This paper provides a review of the historical dam-break events for which real-field datasets useful for validation purposes can be retrieved in the literature. The resulting real-field test cases are divided into well-documented test cases, for which extensive and complete data are already available, and cases with partial or inaccurate datasets. Type and quality of the available data are specified for each case. Finally, validation data provided by dam-break studies on physical models reproducing real topographies are presented and discussed. This review aims at helping dam-break modelers: (a) to select the most suitable real-field test cases for validating their numerical models, (b) to facilitate data access by indicating relevant bibliographic references, and (c) to identify test cases of potential interest worthy of further research.

Seepage field characteristic and stability analysis of tailings dam under action of chemical solution

As one of the important influencing factors of tailings dam stability, seepage field distribution within the dam is often affected by the tailings mineral characteristics. While the alkalinity or acidity of reservoir water and long term immersion will partially change the physical and mechanical properties of tailings. This study carried out permeability tests of tailings under the action of chemical solution. On this basis, a three dimensional (3D) model was constructed to analyze the velocity field and effective saturation within the tailings dam. Moreover, the dam section along the valley bottom was selected as the basic section in calculation, so as to analyze the changes in infiltration point and buried depth of the phreatic line under different permeability coefficient ratios. The results suggest that, under the action of acid-alkaline solution, the permeability coefficients of tailings reduced, and the stronger solution acidity-alkalinity resulted in the longer action time and more obvious change; under the action of chemical solution, the fluid flow velocity in the dam gradually decreased, and the drat beach length in the reservoir gradually shortened. Besides, when the upper layer permeability coefficients of tailings was lower than that of the lower layer, the dam phreatic line had a shallow buried depth and a high infiltration point.

Experimental Study of Mesostructure Deformation Characteristics of Unsaturated Tailings with Different Moisture Content

A portion of the accumulated tailings in a tailings pond exhibits an unsaturated state. The mechanical properties of unsaturated tailings affect the safety and stability of tailings dams. To investigate the effect of moisture content on the deformation characteristics of unsaturated tailings in the mesoscale, a special testing apparatus is applied to experimentally study the settlement deformation and mesostructure evolution of unsaturated tailings under continuous load. The results show that the mesostructure deformation of unsaturated tailings with different moisture contents under load is the same and can be divided into four stages: pore compression, elastic deformation, structure change, and further compaction. However, the critical pressures of the four stages are significantly different; there is an optimal moisture content corresponding to the maximum deformation resistance. Moreover, the influence of the liquid bridge regime on the mesostructure deformation of unsaturated tailings is discussed in this paper.

Numerical Simulation of Seepage and Stability of Tailings Dams: A Case Study in Lixi, China

The purpose of establishing a tailings dam is to safely store tailings to protect the natural environment from damage. Accidents at tailings dams are frequent, however, with serious consequences of not only threats to life and property but also the pollution of the environment. Many tailings dam accidents are caused by seepage failure. In this paper, the object of the case study is the Lixi tailings dam. Three- and two-dimensional finite element models are established. The seepage field of the project under different working conditions is simulated and the position of the phreatic line is obtained. The safety factors under different working conditions are obtained by combining the seepage field with the stable surface. Finally, the influence of different dry and upstream slope ratio on seepage and stability of tailings dam is obtained. The results show that the longer the length of the dry beach, the lower the phreatic line and the greater the safety factor. The higher the upstream slope ratio, the lower the phreatic line and the greater the safety factor.

Social Vulnerability Assessment for Flood Risk Analysis

This paper proposes a methodology for the analysis of social vulnerability to floods based on the integration and weighting of a range of exposure and resistance (coping capacity) indicators. It focuses on the selection and characteristics of each proposed indicator and the integration procedure based on the analytic hierarchy process (AHP) on a large scale. The majority of data used for the calculation of the indicators comes from open public data sources, which allows the replicability of the method in any area where the same data are available. To demonstrate the feasibility of the method, a study case is presented. The flood social vulnerability assessment focuses on the municipality of Ponferrada (Spain), a medium-sized town that has high exposure to floods due to potential breakage of the dam located upstream. A detailed mapping of the social vulnerability index is generated at the urban parcel scale, which shows an affected population of 34,941 inhabitants. The capability of working with such detailed units of analysis for an entire medium-sized town provides a valuable tool to support flood risk planning and management.

Numerical modelling of oil-sands tailings dam breach runout and overland flow

Tailings dams, used for containing the residue of mining processes, are very important elements of the Alberta oil-sands industry in Canada. Potential breach of any of these dams can have catastrophic impact on the environment, economy and human health and safety. Therefore, understanding the after-breach processes is a crucial step in hazard analysis and response planning. This paper studies the potential consequence of a hypothetical oil-sands tailings dam breach by performing numerical simulations of the runout and non-Newtonian overland flow of tailings, including the resulting flooding condition and subsequent spill to nearby water bodies. A non-Newtonian dam-breach model with a visco-plastic rheological relationship is used for this purpose. The model is first validated using the 2014 Mount Polley tailings dam breach in British Columbia, before its application to investigate the flooding volume, extent, and downstream hydrograph of a hypothetical breach from a selected oil-sands tailings dam. The validation results show that the model is able to reproduce the flooding extent and water level variation (due to breach wave) at a downstream lake. The oil-sands tailings spill simulation study demonstrated the importance of considering the non-Newtonian behaviour of tailings materials as the non-Newtonian approach resulted in twice as long flood travel time and slightly less spill volume to the downstream river (i.e. Lower Athabasca River) as that of a Newtonian fluid (i.e. water). The results are also found to be highly sensitive to the rheological parameters of the tailings materials such as their viscosity and yield stress that need to be determined through proper calibration.

Geochemical distribution of selected elements in flotation tailings and soils/sediments from the dam spill at the abandoned antimony mine Stolice, Serbia

Materials held within mine tailings pose a serious risk to the environment in cases of tailings dam failure. Collapse of the tailing dam at the Stolice antimony mine in West Serbia caused a spilling of tailing slurry into the nearby river watersheds. Medium-term effects of As, Pb, Sb, Zn, and Cd from the tailings material that remained in the flooded zone 3 years after the initial exposure were evaluated. Mobility of these elements was determined by analyzing their distribution between exchangeable, reducible, oxidizable, and residual phases. Results indicate that Fe-Mn oxides represent important sinks for As, Cd, Pb, and Sb. Multivariate statistical analysis revealed that concentrations of the analyzed elements were related to sand-sized fractions, as they tended to adsorb or co-precipitate as coatings on larger particles (particularly feldspar and quartz) upon the change of redox conditions. Assessment of the most relevant physico-chemical factors, metal(loid) concentration, and mobility can be used as tool to characterize the degree of contamination of impacted sites. Percentage of sand-sized particles, content of investigated metal(loid)s, and their amount in the reducible fractions are factors determining the best remediation techniques for the area impacted by tailing spill.

Evolution Pattern of Tailings Flow from Dam Failure and the Buffering Effect of Debris Blocking Dams

Tailings ponds are the indispensable facilities in the mine production and operation. Once the dam is destabilized and damaged, it will pose a serious threat on the life and property of the downstream population and could also potentially cause an environmental disaster. With an engineering background, this paper dynamically and numerically simulates the evolution process of tailings flow from dam failure and the influence scope of any resulting disaster in context. The evolution characteristics of leaked tailings flow are analyzed at various downstream riverbed slopes and debris blocking dam settings. In addition, parameters such as flow rate, impact force and deposition range of leaked tailings flow at downstream arrival are studied, as well as their correlations. The results indicate that the flat terrains upstream and downstream of passage zone show a relatively larger area of inundation by tailings flow. Both the maximum and final downstream inundated ranges increase with the elevating slope of downstream riverbed, and the leaked tailings are deposited mainly in the nearby villages in front of the dam and the flat terrains of the downstream passage zone. Additionally, rational establishment of debris blocking dams on the downstream side is effective in diminishing the damage of tailings flow to the downstream section. This study can also provide an important basis for the quantitative evaluation of post-disaster influence scope for tailings pond as well as for the design of dam body.

A value-added multistage utilization process for the gradient-recovery tin, iron and preparing composite phase change materials (C-PCMs) from tailings

Tin-, iron-bearing tailing is a typically hazardous solid waste in China, which contains plenty of valuable tin, iron elements and is not utilized effectively. In this study, a multistage utilization process was put forward to get the utmost out of the valuable elements (tin and iron) from the tailings, and a gradient-recovery method with three procedures was demonstrated: (1) An activated roasting followed by magnetic separation process was conducted under CO-CO2 atmosphere, tin and iron were efficiently separated during magnetic separation process, and 90.8 wt% iron was enriched in magnetic materials while tin entered into non-magnetic materials; (2) The tin-enriched non-magnetic materials were briquetted with CaCl2 and anthracite and roasted, then tin-rich dusts were collected during the chloridizing roasting process; (3) The roasted briquettes were infiltrated in melting NaNO3 to prepare NaNO3/C-PCMs by a infiltration method. Three kinds of products were obtained from the tailings by the novel process: magnetic concentrates containing 64.53 wt.% TFe, tin-rich dusts containg 52.4 wt.% TSn and NaNO3/C-PCMs for high temperature heat storage. Such a comprehensive and clean utilization method for tin-, iron-bearing tailings produced no secondary hazardous solid wastes, and had great potential for practical application.

Particle shape analysis of tailings using digital image processing

The physical and mechanical properties of the dielectric materials mainly depend on shapes of particles in granular media. In order to reveal the differences of physical and mechanical properties between tailings and natural sands from the microscopic view, the usage of digital image processing techniques contributes to the quantification of shape descriptors (elongation, sphericity, convexity, and roughness) describing the shapes of particles. The comparison between four tailings (gold, tin, copper, and iron) and two natural sands (river sand and sea sand) is made in the current study. Results show that particle shape descriptors have great relationship with particle size. The decrement of particle size, on one hand, leads to the increase of the elongation of tailings and sea sand, and thus forming the needle-like or columnar shape of particles. The sphericity of tailings and river sand also increases and generates spherical shapes of particles. On the other hand, both of the convexity and roughness of tailings and sea sand grow with larger particle size. The remarkable difference can be observed on surface texture of particles between tailings and sea sand. Much higher angularity of tailings is also represented by comparing with that of sea sand and river sand.

Effect of overflow tailings properties on cemented paste backfill

This paper presents the results of an experimental study on the unconfined compressive strength (UCS), indirect tensile strength (ITS), microstructural properties and environmental impacts of overflow tailings (OFT) cemented paste backfill (CPB). The test results show that the poor graded OFT contain 47.15% particles with size below 20 μm, and high content of oxide and sulfide. The slump of fresh CPB mixture ranges from 19.50 cm to 21.60 cm, and its flowability meets the transport requirements. After being cured for 28 days, the UCS and ITS of CPB are less than 2 MPa and 0.5 MPa, respectively. Meanwhile, CPB exhibited low residual strength and high brittleness. The low strength is mainly due to the use of fine OFT. The results show that sulphate also has negative effect on strength and dissolve calcium silicate hydrate (C-S-H) while promoting the formation of secondary products (gypsum and ettringite), leading to generate cracks and decrease UCS at 28 curing time of some CPB mixtures. Increasing the cement content and solid mass concentration is the effective methods to improve the mechanical properties of CPB. The nuclear magnetic resonance (NMR) tests show that fine OFT with low osmotic coefficient (3.10e-06 cm/s) and high sulfur content cause high porosity from 25.0% to 33.1% of CPB, and the increase of the porosity is observed a negative influence on the UCS, but no obvious relationship between ITS and porosity is obtained. Scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) tests show that OFT particles were covered by C-S-H gel which can enhance the compactness and integrity of CPB. The SEM tests also found secondary products gypsum and ettringite. These finding suggest that OFT can be suitably used as backfill material to fill the underground stopes.

Experimental research on the rheological properties of tailings and its effect factors

The rheological properties of tailings from gold, copper, and iron ore have been studied in this paper, using a self-developed large-scale type coaxial cylinder rheometer. The effect factors of the rheological properties of tailings, namely mineral types, particle size, plasma concentration, and the shear rate, and the influence they have on the viscosity and yield stress have also been studied. The test results showed that the viscosity of the tailings initially decreased with time and then became stable, while the yield stress initially increased with time and then tended to become stable. Three types of tailings all had a similar change trend with only small differences in value. The differences resulted from the varying mineral constituents of the tailings. The viscosity and the yield stress of the tailings increased as the concentration increased. As the shear rate decreased, the viscosity increased, but the yield stress also decreased. The change in magnitude of the yield stress increased as the concentration increased. It was also found that a larger particle size resulted in a higher viscosity and yield stress, the rise of which became more obvious at higher concentrations. The results were fitted using the exponential function of the Bingham model, and it was found that the coefficients of A₁ and A₂ changed significantly with the concentration, which indicated that A₁ and A₂ were largely influenced by other factors, and not only by the plasma concentration and particle diameter decisions. However, these functions of the Bingham model and the other coefficients of B₁ and B₂ were nearly constant. The three types of tailings also had a similar change trend for the fitted coefficients. There were some differences between the values associated with the type of tailings. For the same kind of tailings, the values of B₁ and B₂ were only slightly affected by other factors, while they were mainly influenced by the plasma concentration. The results of this research have provided the basic material for a stability study of a tailings dam and the analysis of movement law.

Modelling the potential effects of Oil-Sands tailings pond breach on the water and sediment quality of the Lower Athabasca River

Within the Oil-Sands industry in Alberta, Canada, tailings ponds are used as water recycling and tailings storage facilities (TSF) for mining activities. However, there could be possible circumstances under which a sudden breach of an embankment confining one of the TSFs may occur. Such a tailings pond breach would result in a sudden release of a huge volume of Oil Sands process-affected water (OSPW) and sediment slurry containing substantial amount of chemical constituents that would follow the downstream drainage paths and subsequently enter into the Lower Athabasca River (LAR). This study investigates the implications of OS tailings release on the water and sediment quality of the LAR by simulating the fate of sediment and associated chemicals corresponding to a hypothetical breach and release scenarios from a select set of tailings ponds using a two-dimensional hydrodynamic and constituent transport model. After predicting the total volume, time evolution and concentration of sediment and associated chemicals (metals, polycyclic aromatic hydrocarbons (PAHs) and naphthenic acids (NAs)) reaching the LAR, the transport and deposition of these materials within the study reach is simulated. The results show that, depending on tailings release locations, between 40 and 70% of the sediment and associated chemicals get deposited onto the river bed of the 160 km study reach while the rest leaves the study domain during the first three days following the release event. These sediment/chemicals deposited during the initial spill may also have long-term effects on the water quality and aquatic ecosystem of the river and the downstream delta. However, care has to be taken in interpreting the results as further analysis has shown that the outcomes of such model simulations are very sensitive to the various underlying assumptions as well as the values assigned to some model parameters representing the physical properties of the tailings material.

The Stability of Tailings Dams under Dry-Wet Cycles: A Case Study in Luonan, China

Instability of tailings dams may result in loss of life and property and serious environmental pollution. The position of the tailings dam’s phreatic line varies due to continuously changing factors such as rainfall infiltration and discharge of tailings recycling water. Consequently, tailings dams undergo dry-wet (DW) cycles, accompanied by the appearance of a hydro-fluctuation belt. With dynamic development of the physical and chemical properties of tailings sand in the hydro-fluctuation belt, the stability of tailings dams is uncertain. In this study, direct shear tests were performed on the tailings sand collected from a tailings dam in Luonan, through which the shear strength parameters of tailings sand with DW cycles were obtained. Then, a method that efficiently calculates the phreatic line of the tailings dam under DW cycles was proposed. In addition, based on laboratory tests and the proposed phreatic line calculation method, we used a finite element program to evaluate the stability of the tailings dam that experienced different DW cycles. The calculated results showed that: (i) the damage effects of DW cycles gradually weakens as the number of DW cycles increases. (ii) With the increasing of DW cycles, the maximum displacement of the tailings dam increases from 0.5 mm to 22 mm, and the area of maximum displacement expanded mainly at the toe of the tailings dam and at the front edge of the hydro-fluctuation belt. (iii) The tailings dam safety factor decreases continuously with increasing DW cycles. This study may provide a novel method for analyzing the stability of tailings dams under different DW cycles as well as an important reference for improving tailings dam stability.

Accidental Water Pollution Risk Analysis of Mine Tailings Ponds in Guanting Reservoir Watershed, Zhangjiakou City, China

Over the past half century, a surprising number of major pollution incidents occurred due to tailings dam failures. Most previous studies of such incidents comprised forensic analyses of environmental impacts after a tailings dam failure, with few considering the combined pollution risk before incidents occur at a watershed-scale. We therefore propose Watershed-scale Tailings-pond Pollution Risk Analysis (WTPRA), designed for multiple mine tailings ponds, stemming from previous watershed-scale accidental pollution risk assessments. Transferred and combined risk is embedded using risk rankings of multiple routes of the "source-pathway-target" in the WTPRA. The previous approach is modified using multi-criteria analysis, dam failure models, and instantaneous water quality models, which are modified for application to multiple tailings ponds. The study area covers the basin of Gutanting Reservoir (the largest backup drinking water source for Beijing) in Zhangjiakou City, where many mine tailings ponds are located. The resultant map shows that risk is higher downstream of Gutanting Reservoir and in its two tributary basins (i.e., Qingshui River and Longyang River). Conversely, risk is lower in the midstream and upstream reaches. The analysis also indicates that the most hazardous mine tailings ponds are located in Chongli and Xuanhua, and that Guanting Reservoir is the most vulnerable receptor. Sensitivity and uncertainty analyses are performed to validate the robustness of the WTPRA method.

Absorption mechanisms of Cu(2+) on a biogenic bixbyite-like Mn2O3 produced by Bacillus CUA isolated from soil

BACKGROUND

Although most reported biogenic Mn oxides are hexagonal birnessites, other types of biogenic Mn oxides also commonly occur in the environment. However, sorption characteristics and underlying mechanisms of the adsorption of heavy-metal ions on these biogenic Mn oxides are still rarely addressed. In this study, the sorption mechanisms of Cu(II) on a low valence biogenic Mn oxide, poorly crystallized bixbyite-like Mn2O3 (α-Mn2O3), were investigated.

RESULTS

The maximum adsorption capacity of Cu(II) onto this biogenic Mn oxide at pH 6.00 was 796 mmol/kg (0.45 mol Cu mol(-1) Mn). The complex structure of adsorbed Cu(II) was constrained using Cu extended X-ray absorption fine structure (EXAFS) analysis, combined with structural parameters of the biogenic Mn oxide with alternately arranged regular and distorted MnO6 octahedra obtained through multiple-FEFF fitting of Mn EXAFS data. The sorbed Cu(II) was found to coordinate with the biogenic Mn oxide particle edges as inner-sphere complexes. At a relatively low Cu(2+) loading (233 mmol/kg, pH 6.00), Cu(II) adsorbed onto the biogenic Mn oxide with two types of coordinated complexes, i.e., (1) coordinated with one regular/distorted MnO6 octahedron as a monodentate-mononuclear complex and (2) with two adjacent MnO6 octahedra as a bidentate-binuclear complex. While, at a relatively high Cu(2+) loading (787 mmol/kg, pH 6.00), only one type of coordinated complex was constrained, the adsorbed Cu(II) coordinated with one regular/distorted MnO6 octahedron as a monodentate-mononuclear complex.

CONCLUSIONS

This research extends further insight into the bacterial Mn(II) oxidation in the environment and serves as a good reference for understanding the interactions between metal ions and biogenic low valence Mn oxides, which are still poorly explored either theoretically or practically.

Ecological impacts of large-scale disposal of mining waste in the deep sea

Deep-Sea Tailings Placement (DSTP) from terrestrial mines is one of several large-scale industrial activities now taking place in the deep sea. The scale and persistence of its impacts on seabed biota are unknown. We sampled around the Lihir and Misima island mines in Papua New Guinea to measure the impacts of ongoing DSTP and assess the state of benthic infaunal communities after its conclusion. At Lihir, where DSTP has operated continuously since 1996, abundance of sediment infauna was substantially reduced across the sampled depth range (800–2020 m), accompanied by changes in higher-taxon community structure, in comparison with unimpacted reference stations. At Misima, where DSTP took place for 15 years, ending in 2004, effects on community composition persisted 3.5 years after its conclusion. Active tailings deposition has severe impacts on deep-sea infaunal communities and these impacts are detectable at a coarse level of taxonomic resolution.

Design, construction and management of tailings storage facilities for surface disposal in China: case studies of failures

Rapid development of China's economy demands for more mineral resources. At the same time, a vast quantity of mine tailings, as the waste byproduct of mining and mineral processing, is being produced in huge proportions. Tailings impoundments play an important role in the practical surface disposal of these large quantities of mining waste. Historically, tailings were relatively small in quantity and had no commercial value, thus little attention was paid to their disposal. The tailings were preferably discharged near the mines and few tailings storage facilities were constructed in mainland China. This situation has significantly changed since 2000, because the Chinese economy is growing rapidly and Chinese regulations and legislation require that tailings disposal systems must be ready before the mining operation begins. Consequently, data up to 2008 shows that more than 12 000 tailings storage facilities have been built in China. This paper reviews the history of tailings disposal in China, discusses three cases of tailings dam failures and explores failure mechanisms, and the procedures commonly used in China for planning, design, construction and management of tailings impoundments. This paper also discusses the current situation, shortcomings and key weaknesses, as well as future development trends for tailings storage facilities in China.

Chemical composition and minerals in pyrite ash of an abandoned sulphuric acid production plant

The extraction of sulphur produces a hematite-rich waste, known as roasted pyrite ash, which contains significant amounts of environmentally sensitive elements in variable concentrations and modes of occurrence. Whilst the mineralogy of roasted pyrite ash associated with iron or copper mining has been studied, as this is the main source of sulphur worldwide, the mineralogy, and more importantly, the characterization of submicron, ultrafine and nanoparticles, in coal-derived roasted pyrite ash remain to be resolved. In this work we provide essential data on the chemical composition and nanomineralogical assemblage of roasted pyrite ash. XRD, HR-TEM and FE-SEM were used to identify a large variety of minerals of anthropogenic origin. These phases result from highly complex chemical reactions occurring during the processing of coal pyrite of southern Brazil for sulphur extraction and further manufacture of sulphuric acid. Iron-rich submicron, ultrafine and nanoparticles within the ash may contain high proportions of toxic elements such as As, Se, U, among others. A number of elements, such as As, Cr, Cu, Co, La, Mn, Ni, Pb, Sb, Se, Sr, Ti, Zn, and Zr, were found to be present in individual nanoparticles and submicron, ultrafine and nanominerals (e.g. oxides, sulphates, clays) in concentrations of up to 5%. The study of nanominerals in roasted pyrite ash from coal rejects is important to develop an understanding on the nature of this by-product, and to assess the interaction between emitted nanominerals, ultra-fine particles, and atmospheric gases, rain or body fluids, and thus to evaluate the environmental and health impacts of pyrite ash materials.

Combination of sequential chemical extraction and modelling of dam-break wave propagation to aid assessment of risk related to the possible collapse of a roasted sulphide tailings dam

The Sotiel-Coronada abandoned mining district (Iberian Pyrite Belt) produced complex massive sulphide ores which were processed by flotation to obtain Cu, Zn and Pb concentrates. The crude pyrite refuses were roasted for sulphuric acid production in a plant located close to the flotation site, and waste stored in a tailing dam. The present study was focused on the measurements of flow properties, chemical characterization and mineralogical determination of the roasted pyrite refuses with the aim of assessing the potential environmental impact in case of dam collapse. Chemical studies include the determination of the total contaminant content and information about their bio-availability or mobility using sequential extraction techniques. In the hypothetical case of the tailing dam breaking up and waste spilling (ca. 4.54Mt), a high density mud flow would flood the Odiel river valley and reach both Estuary of Huelva (Biosphere Reserve by UNESCO, 1983) and Atlantic Ocean in matter of a couple of days, as it was predicted by numerical simulations of dam-break waves propagation through the river valley based on quasi-2D Saint-Venant equations. The total amount of mobile pollutants that would be released into the surrounding environment is approximately of 7.1.10(4)t of S, 1.6.10(4)t of Fe, 1.4.10(4)t of As, 1.2.10(4)t of Zn, 1.0.10(4)t of Pb, 7.4.10(3)t of Mn, 2.2.10(3)t of Cu, 1.5.10(2)t of Co, 36t of Cd and 17t of Ni. Around 90-100% of S, Zn, Co and Ni, 60-70% of Mn and Cd, 30-40% of Fe and Cu, and 5% of As and Pb of the mobile fraction would be easily in the most labile fraction (water-soluble pollutants), and therefore, the most dangerous and bio-available for the environment. This gives an idea of the extreme potential risk of roasted pyrite ashes to the environment, until now little-described in the scientific literature.