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PRINCIPAUX DÉFIS ET PISTES DE SOLUTION POUR LA RESTAURATION DES AIRES D'ENTREPOSAGE DE REJETS MINIERS ABANDONNÉES
Abstract
3 Chaire industrielle CRSNG Polytechnique – UQAT 4 CRC sur la restauration des sites miniers abandonnés http://web2.uqat.ca/crc-bussiere/ RÉSUMÉ Au cours des dernières années, beaucoup d'efforts de recherche ont été investis afin de développer des méthodes visant à contrôler la production d'eaux de drainage minier acide (DMA) ou de drainage neutre contaminé (DNC), provenant de sites d'entreposage de rejets miniers. La plupart de ces méthodes ont pour objectif d'éliminer, ou de réduire à des niveaux très faibles, la présence d'air (ou d'oxygène), d'eau ou de sulfures. Les techniques développées sont particulièrement efficaces pour les sites en opération. Cependant, lorsque les rejets miniers ont été exposés pendant plusieurs années (voire plusieurs dizaines d'années dans certains cas) aux conditions naturelles environnantes, ces techniques ne permettent pas toujours d'atteindre les objectifs environnementaux visés. Des ajustements doivent donc être prévus lors de la mise en place des méthodes de restauration sur des aires d'entreposage de rejets miniers abandonnées. Par exemple, il peut être nécessaire de mettre en place des systèmes de traitement à l'effluent final pour traiter l'eau contaminée par l'oxydation antérieure à la mise en place de la méthode de restauration, ou encore de procéder à la neutralisation de l'eau interstitielle, afin d'éviter l'oxydation indirecte par le fer et l'effet des minéraux secondaires présents. Des exemples de restauration de sites miniers abandonnés montrent qu'il est possible de limiter les impacts environnementaux par l'application de méthodes appropriées. Il reste cependant à optimiser ces approches, afin de réduire les coûts associés à la mise en place de méthodes efficaces de contrôle de la contamination provenant d'aires d'entreposage de rejets miniers génératrices de DMA ou de DNC.
... This could present significant health risks to the local populations and the environment. Iron, as one of the inorganic pollutants, is highly sensitive to redox reactions and easily oxidized in the environment in the presence of oxygen (Bussière et al., 2005). In its ionic form (Fe(II) or Fe(III)), iron can pose a threat to human health, with the World Health Organization (WHO) setting a limit of 0.3 mg/L for Fe(II) in drinking water (Belghiti et al., 2013;Mahamane & Guel, 2015). ...
... These iron sulfides, when naturally exposed to the action of open air and water, oxidize and generate sulfuric acid. This phenomenon, called acid mine drainage (AMD), can be the cause of pollution and ecological imbalance [1,2] Mining discharges and deposits containing large quantities of acid-eating minerals do not generate AMD, following the neutralization of acidic waters [3,4,5] In this article, we set ourselves the objective of characterizing the AMD of this site where the sulfurs of the black shale have already undergone partial environmental oxidation, to see how to propose a sustainable management solution in the event of confirmed pollution. ...
The black shale from the company “Frontier S.A” in Sakania is impregnated with sulphide minerals such as pyrite which is an iron sulphide (FeS2) and chalcopyrite which is a double sulphide of copper and iron (Cu FeS2). Due to its storage in the open air, these sulphides are particularly oxidized. In addition, this black shale presents a certain physical and chemical instability which can be the basis of the degradation of the nearby surrounding environments (watercourses, soils, groundwater, etc.). It results from our chemical characterization tests that this black shale contains 0.05% Cu, 0.007% Co, 1.3% Fe, 0.007% Ni, 0.001% As; 0.0012% Pb; 0.0021 Cd; 1.75% of S.The mineralogical analysis reveals that the sample contains the main minerals: sulphides, in the form of chalcopyrite and pyrite; oxidized, in the form of quartz; carbonates, in the form of dolomite and calcite, and graphitic material (C). For the determination of the character of acid mine drainage, the static tests for predicting the AMD on the one hand, gave values for the net neutralization potential (NNP) and the ratio between the neutralization and acidification potentials (RPN). respectively 37.5 and 41.39, that is to say values classifying the black shale of Frontier as not generating ADM. And on the other hand, during the kinetic tests using the principle of testing periodic leaching of the sample over a long period, the percolates obtained made it possible to monitor the pH (between 6.2 to 7.07), the redox potential (between -39.8 to 92mV), the electrical conductivity (between 640 to 672μS/Cm), as well as the concentration rate of metals (low mobilization). This made it possible to conclude that the AMD did not exist on the site.
... Some of these sites contain AMD generating and metal leaching tailings, which must eventually be reclaimed to reduce their environmental impact. Reclamation of legacy sites can be difficult because of tailings properties, not being designed for closure, contaminated pore water, material supply, accessibility and costs (Bussière et al. 2005). Oxidation products from sulfide exposure to atmospheric conditions can be deposited on the particle surfaces in unsaturated conditions. ...
Mine closure can be approached by several points of view, from the technical, engineering, ecological, up to social and governance aspects. The definition of a good mine closure should cover most, if not all, of these aspects. This article provides a review of technical and engineering-oriented research work as a partial answer to the question ‘what is good mine closure’. The article presents a ten-year research program realized in the framework of a Canada Research Chair in integration of environment in the mine life cycle. Research projects aimed at better planning mine closure and mine site reclamation from the early stages of a mining project life cycle are exposed as possible steps to strive for optimal mine waste management. At the exploration stage, geo-environmental characterization and modeling are proposed as tools to improve mine waste management planification. During mine operations, environmental desulfurization is suggested as a method to reduce environmental risks associated with sulfidic tailings and waste rock. Indeed, research has shown that acid mine drainage and metal leaching can be significantly limited via desulfurization. At the closure stage, desulfurized tailings can be used to replace at least part of natural materials used for reclamation cover systems. Research work done on other types of mine waste, such as waste rock and water treatment sludge, also show good potential for their reuse as closure material. All these tools can be integrated into the mine life cycle to better plan for closure, which ultimately will make mine closure more sustainable.
... The adoption of more restrictive regulations by the majority of industrialized countries favored initiatives to protect the environment during and after mining operations. Atmospheric oxygen, sulphide minerals and water availability are the main factors in the process of AMD or CND generation (e.g., Bussière et al., 2005;Johnson and Hallberg 2005). An oxygen barrier is usually considered the most efficient approach to control AMD generation (e.g., SRK 1989;MEND 2001;EIPPCB 2003), particularly in wet temperate climates. ...
The Edendale lead mine was decommissioned before the environmental enforcement related to mining in South Africa. The mine has been left with un‐rehabilitated waste materials which are potential environmental hazards. The waste rock materials at the mine site were sampled and analysed for As, Ba, Cr, Cu, Ni, Pb, Se, U, V and Zn in order to determine the potential environmental pollution. The geochemical characterisation of the samples was done through X ray fluorescence (XRF) and X ray diffraction (XRD). The samples were also sent to the laboratory for paste pH, paste electrical conductivity and batch leach test analysis. The leachate were analysed for Al, As, Zn, Pb, Cr and Se using ICP –MS Elan 9000 and for anions using ion chromatography. The XRF results were compared to the Canadian soil quality guidelines for the protection of environmental and human health for industrial land, whereas the leachates from the waste rocks were compared with South African water quality guidelines for the aquatic ecosystem to determine the extent of toxic metal contamination. According to the XRF results, concentrations of Cr, Ni, Pb and Zn in waste rock dump 1 exceeded the guideline values of 87 ppm, 50 ppm, 600 ppm and 360 ppm respectively. Similarly waste rock dump 2 is also contaminated with Cr, Ni and Zn, whereas waste rock dump 3 and 4 are polluted with Cu, Cr, Ni, Pb and Zn. Therefore, XRF results indicate that the waste rock dumps at Edendale are contaminated with Cr, Ni, Pb, Zn and Cu. The high concentrations of Ni, Pb and Zn could be attributed to the presence of chlorite, Zinckenite and sphalerite, while high concentrations of Cr and Cu require further investigation. The leachate results indicated that aluminium, lead and zinc could be leached with water from the waste rock dumps. The average leachate aluminium concentration 1.005 mg/L was higher than the target water quality range (0.005 mg/L). The average leachate lead concentrations (88.595) was higher than the target water quality range 0.2 μg/L (soft water), 0.5 μg/L (medium water), 1.0 μg/L ( hard water) and 1.2 μg/L ( very hard water) while zinc (0.003 mg/L) was slightly higher than the target water quality range of 0.002 mg/L. Ion chromatography results showed that fluoride (1.1mg/L) in ED – WR 04 was above the target water quality range of 0.075 mg/L. The sulphate and inorganic nitrogen leachate concentrations were below the target values of 500 mg/L and 0.5 mg/L respectively. Such contamination of the waste rock dumps by Cr, Ni, Pb, Zn and Cu, and leaching of Al, Pb, Zn and Fluoride could negatively affect human health and aquatic life. Therefore, it is critical that measures are taken to rehabilitate the Edendale lead mine.
... It constitutes an inseparable part of the ore extract and treating process [1]. The management of mining wastes is becoming a world concern due to: (i) their high amount, which is estimated to be between 20 and 25 billion tons of solid waste each year [2]; (ii) their environmental impact [3]; (iii) their expensive restoration costs [4]; (iv) and potential human health risks [5][6][7]. The implementation of both efficient and sustainable solutions to better manage this waste is therefore becoming a more serious priority. ...
The purpose of this research was to evaluate the possibility of using gold mine waste rocks (GMWRs) as alternative raw material for the manufacturing of fired bricks. The feasibility study was assessed through (i) physical, chemical, mineralogical and environmental characteristics of GMWRs; (ii) determination of the natural clay (NC) substitution effect when using GMWRs; (iii) the effect of the firing temperature on the mechanical and physical properties of the fired bricks. Five mixtures of NC and GMWRs were studied. The percentages of substitution of NC with GMWRs varied from 0 to 100%. The brick specimens were fired at 900 °C, 1000 °C and 1050 °C. The results show that increasing the firing temperature improved the flexural strength and density of the bricks, while the substitution of NC with GMWRs caused a reduction in the mechanical resistance of the bricks and an increase in their porosity and, consequently, their water absorption rate. However, the properties of bricks that contained up to 80 wt% of GMWRs and fired at 1000 °C and 1050 °C satisfied the requirements set by the applicable civil engineering and environmental standards. This was found to be an efficient and sustainable solution to mitigate environmental hazards and better manage mining wastes, concurrently producing marketable products from them, which is in accordance with the circular economy concept.
... These kinetic tests demonstrated that the waste rocks do not generate AMD in the long term, the weak acidity produced being neutralized by abundant quantity of gangue minerals (mainly by calcic plagioclase). The pH of the drainage waters was close to neutral and the nickel present in these waters was generated by the oxidation of the sulphides (e.g pyrite) present in traces within the waste rock (Bussière et al., 2005;Pepin, 2009;Plante et al., 2011b). Previous studies showed that Ni concentrations in drainage waters are controlled mainly by sorption phenomena (Plante et al., , 2011aDemers et al., 2011Demers et al., , 2013. ...
In the mining industry, the extraction of waste rocks (WR), without economic value, is needed to access ore deposits. The amount of WR are very large in the case of open pit mines. They are usually stored at the surface in waste rock piles. The presence of reactive minerals such as sulphides in waste rock can lead to the contamination of drainage water that come-out from these waste rock piles. In order to limit the production of contaminants and the volume of drainage water, an innovative method of construction of waste rock piles has been developed. In this context, an experimental waste rock pile was constructed at the Lac Tio mine near Havre-Saint-Pierre (Quebec, Canada) to evaluate the performance of this approach in field conditions. To understand the geochemical mixing between the leachate from the hemo-ilmenite and anorthosite waste rock layers constituting this experimental pile, tests using lab columns that were filled with layers of these two types of materials were run. The anorthosite and hemo-ilmenite waste rock subjected to column tests generated near-neutral drainage (pH ~7) containing up to 4.5 mg/l of nickel, and 1500 mg/l of sulphate. The nickel and sulphate release rates varied from one to two orders of magnitude depending on the type of waste rocks and their configuration (pure or mixed with each other). The drainage water quality was affected by changes in the volume of rinsing water, by the precipitation/dissolution of secondary minerals, and by Ni sorption within anorthosite waste rock. This study demonstrates that the storage of hemo-ilmenite waste rock over anorthosite waste rock is an effective way to reduce Ni levels in drainage waters from the Lac Tio mine materials.
... Acidic drainage stemming from mining activities is by far a deleterious source of water contamination in hard rock mines. Environmental surveys of acid mine drainage (AMD) may include assessment, prevention and/or treatment to safeguard the surrounding ecosystems (Akcil and Koldas, 2006;Benzaazoua et al., 2004;Bouzahzah et al., 2014;Bussière et al., 2001;Bussière et al., 2005;Evangelou, 1995;Jouini et al., 2020;Neculita et al., 2010;Plante et al., 2012). ...
Three-dimensional geological modeling is an efficient tool to visualize ore body features during both the exploration and operation phases of mines. Repurposing the 3D geological modeling for mine waste management allows for the visualization of hazardous metals distribution throughout an ore body and its host rock. With this information, a mine manager could seamlessly carry out waste rock management based upon their classification. The major prerequisite to such an approach is to procure sufficiently large datasets in order to ensure high interpolation quality and suitable resolution. Apart from metals of economic interest, other elements, and more precisely the deleterious elements, usually do not undergo exhaustive geochemical analyses throughout the footwall and the hanging wall of ore bodies. Based on that premise, the Éléonore mine site provided restricted grades of arsenic, the most hazardous element within the mine setting, to create a 3D spatial model of arsenic content. A stochastic process coupled with the geological logging of drill cores was created to fulfill the 3D modeling prerequisite with known margins of error. The outcome of this work consists of multi-realization 3D spatial model of arsenic content across the ore deposit and the hosting rock. Each realization was assessed using available chemical analyses to underline the model’s reliability. The results revealed a spacious geochemical halo of arsenic that could reach up to 500 m away from the gold deposit, with up to 94% of arsenic grades exceeding 50 ppm. The process developed in this work will enable mine waste classification before stripping, thereby providing the opportunity for proactive upstream mine waste management options that could prevent future environmental liabilities.
... Abandoned mine sites often constitute a major eyesore to adjacent communities and pose further risk to surrounding ecosystems as vast amounts of soil, waste rock and tailings are exposed to aeolian and water erosion (Mendez and Maier, 2008). Soil microorganisms are in part responsible for the negative impacts of mine sites, mainly through the formation of acid mine drainage, generally at pH lower than five (Bussière et al., 2005). Revegetation could help initiate the restoration of these disturbed ecosystems. ...
Abandoned unrestored mines are an important environmental concern as they typically remain unvegetated for decades, exposing vast amounts of mine waste to erosion. Several factors limit the revegetation of these sites, including extreme abiotic and unfavorable biotic conditions. However, some pioneer tree species having high levels of genetic diversity, such as balsam poplar (Populus balsamifera), can naturally colonize these sites and initiate plant succession. This suggests that some tree genotypes are likely more suited for acclimation to the conditions of mine wastes. In this study, we selected two contrasting mine waste storage facilities (waste rock from a gold mine and tailings from a molybdenum mine) from the Abitibi region of Quebec (Canada), on which poplars were found to have grown naturally. First, we assessed in situ the impact of vegetation presence on each mine waste type. The presence of balsam poplars improved soil health locally by modifying the physicochemical properties (e.g., higher nutrient content and pH) of the mine wastes and causing an important shift in their bacterial and fungal community compositions, going from lithotrophic communities that dominate mine waste environments to heterotrophic communities involved in nutrient cycling. Next, in a greenhouse experiment we assessed the impact of plant genotype when grown in these mine wastes. Ten genotypes of P. balsamifera were collected locally, found growing either at the mine sites or in the surrounding natural forest. Tree growth was monitored over two growing seasons, after which the effects of genotype-by-environment interactions were assessed by measuring the physicochemical properties of the substrates and the changes in microbial community assembly. Although substrate type was identified as the main driver of rhizosphere microbiome diversity and community structure, a significant effect due to tree genotype was also detected, particularly for bacterial communities. Plant genotype also influenced aboveground tree growth and the physicochemical properties of the substrates. These results highlight the influence of balsam poplar genotype on the soil environment and the potential importance of tree genotype selection in the context of mine waste revegetation.
... Medici. Ainsi subsistent seulement quelques usines isolées converties en méthode indirecte qui finiront, au XVIII e siècle, par succomber à la concurrence des structures Médicis (Cortese, 1997 ;Cortese, 2001 (Roussel et al., 1994 ;Aubertin et al., 2002 ;Bussière et al., 2005 ;Biochemielab & Bianchi, 2006 ;Kimball et al., 2007 ;Demers, 2008 ;Potvin, 2009 ;Gisotti et al., 2011 ;Melun, 2012 ;Maughan, 2015 ;Roy, 2019). Ces recherches se sont Il existe trois études qui ont traité la problématique de l'impact écologique de la mine de Campiano : ...
La dynamique morpho-sédimentaire de la rivière toscane de Merse a été appréhendée à travers le prisme de la dispersion longitudinale des scories sidérurgiques injectées dans la charge de fond au tournant du XXe siècle. L’unique point d’injection des scories a été identifié à la décharge minière dite « Le Roste » associée à la mine de Boccheggiano. Le tri granulométrique en aval de l’injection des a permis de distinguer la zone de palier révélatrice de la compétence effective égale à 3.27 cm et de calculer la vitesse de progression de 9.93 km/siècle. Afin de pouvoir qualifier ces résultats comme représentatifs de la dynamique sédimentaire, les propriétés physiques (forme, densité, taille) des scories et des particules naturelles ont été comparées en arrivant au constat que les scories sont davantage sphériques et denses que les particules naturelles de la charge de fond. Le diamètre médian global (D50) des particules naturelles au palier étant égal à 3.43 cm, on observe que la moyenne des 10 plus grosses scories (M10) sous-estime la compétence effective de 2 à 10%. Le contexte de mobilisation de deux groupes de sédiments au palier a été évalué par la puissance spécifique moyenne (111 W/m²), les forces tractrices critiques (respectivement 36.18 N/m2 et environ 19.2 N/m2 pour les scories et les sédiments naturels) et la force tractrice due à la résistance des particules calculée pour le débit à pleins bords (Qb) (32.5 N/m²). La capacité morphogène, responsable de l’incision de 1.3 m en amont du tronçon et d’une érodabilité considérable des berges un peu plus en aval, a été caractérisée d’une part par la diminution du gradient hydraulique et d’autre part par la force tractrice due à la résistance des formes du chenal calculée pour le Qb (52.6 N/m²). Enfin, l’interprétation globale de la dynamique morpho-sédimentaire a permis d’expliquer le passage d’un style fluvial plutôt torrentiel vers un style méandriforme et d’évaluer l’impact relativement limité de deux obstacles transversaux situés dans la zone concernée par la propagation des scories : du pont routier SP441 et du pont de Luriano.
Mots clés : Toscane, Merse, dynamique morpho-sédimentaire, continuité sédimentaire, scories sidérurgiques, tri granulométrique, compétence effective, vitesse de propagation de la charge de fond, aménagement hydraulique, exploitation minière, sidérurgie
Small-scale infiltration tests were performed on a flow control layer made of compacted sand, installed at the surface of an experimental waste rock pile. The hydraulic conductivity of the sand layer was evaluated from a field investigation using three different testing methods: single-ring infiltrometer, double-ring infiltrometer and Guelph permeameter. The objective was to evaluate and compare the use of these techniques to assess the in-situ hydraulic conductivity of the sand layer. Results from analytical solutions and inverse numerical modelling were also compared. The field approaches gave fairly similar results when the measurements were interpreted with existing approximate solutions, although tests with the Guelph permeameter and single-ring infiltrometer led to slightly higher values of the hydraulic conductivity. The numerical interpretation generally gave lower values for the saturated hydraulic conductivity compared with those obtained analytically, but the differences remain within a factor of 3 or less. The predictive models used in this study, and validated with laboratory measurements, also gave comparable values for the saturated hydraulic conductivity. Any of the three testing methods applied here could, therefore, be used to evaluate the field hydraulic conductivity of the sand layer. Numerical simulations have the advantage of not relying on empirical parameters but require more work with a good estimate of the water retention curve. The investigation also showed that the predictive models used here gave reliable values for hydraulic conductivity when the void ratio was properly determined; such models should however be validated with controlled tests, as was the case here.
l bacteium, Thiobacillus ferrooxidans, is of prime importance in the formation of acid d,rainage from pyritic material. Aboue pH 4.5, T. ferrooxidans incteases initial acid,ification; below pH 4.5, it allous acid,ification to corltinue by oxidizing Fe2 + .-Below a pH of approii*ot"ty 2.5, the ac-livity of Fet + is significant and results in steady-state cycling between oxidation of pyrite by Fel + and, bacteial oxidation of Fe2 I Laboratory andfield tests d,ernonstrate that inhibition of T. ferrooxidans by contrclled. release of anionic d,etergents can inexpensiuely reduce pyrite oxidation and acid. formation.
Research funded by the Centre for Resource Studies, Queen’s University, Kingston, Ontario, Canada.
When landfills reach capacity they are closed with a cover consisting of clay, sand, vegetated top soil and, sometimes, synthetic liners. Many covers have been shown to be leaking causing contamination. The results of the Alternative Land Cover Demonstration (ALCD) conducted by Sandia National Laboratories are described. Six landfill test covers were evaluated: conventional designs meeting the Resource Conservation and Recovery Act subtitle D and C designs; a geosynthetic clay liner, a capillery barrier, an anisotropic barrier and an evapotranspiration cover. The water balance performance of the different covers was monitored. After one year of monitoring, the anisotropic barrier and evapotranspiration cover were the most effective covers.
We measured the rates of reaction of Fe(III) with galena, sphalerite, chalcopyrite, and arsenopyrite at 25°C and pH values near two and found: Where rFe3+ is the rate of reduction of Fe(III) to Fe(II) (mol sec⁻¹), mFe3+ is the concentration of Fe(III) (mol kg⁻¹), and A is the surface area of the solid (m²) exposed to the solution. These results show that the reaction rates, the reaction orders and the activation energies vary substantially from mineral to mineral indicating that the details of the reaction mechanism differ among the various sulfide minerals. This means that pyrite cannot be used as a proxy for these other sulfide minerals when studying the details of sulfide mineral oxidation.
A five steps remediation program was commissioned in 1998 for the acid generating Lorraine mine site, located in the Témiscamingue region, Quebec, Canada. It included, as the main expenditure, a cover with capillary barrier effects (CCBE) used to limit oxygen migration. After construction of the cover, instruments were installed on site to monitor the CCBE performance. Modified oxygen consumption tests were also done to measure the oxygen flux through the cover. Results from water content and suction data, measured from 1999 to 2003, show that the capillary barriers effects are effective and that the water retention layer stays near saturation throughout the years. Oxygen fluxes estimated from monthly water content measures are generally below 10 g/m2/year. Results from modified oxygen consumption tests made on the site give almost similar oxygen fluxes. A two dimension numerical model of the Lorraine mine site was also constructed to verify that mathematical models could predict realistically the in situ conditions on such a large scale site. Numerical results obtained for three years show a good concordance between measured and calculated values. The results obtained form these different evaluation methods for the performance of a CCBE concur and confirm the efficiency of this cover in limiting acid mine generation.
