Mine Closure Research Articles

ANÁLISE DO CASO BRASKEM EM MACEIÓ: UMA INVESTIGAÇÃO NO CONTEXTO DA CPI

This study analyzes the facts surrounding the rock salt extraction by Braskem in Maceió, Alagoas, within the context of investigations conducted by the Parliamentary Commission of Inquiry (PCI) on Braskem. The research employs an exploratory and descriptive qualitative approach, grounded in document analysis and literature review. The rock salt extraction, initiated in the 1970s, holds geological and economic relevance for the region, impacting neighborhoods in the city and presenting significant aspects for local development. The methodology follows the guidelines of Lakatos and Marconi (2010), structuring data collection through public documents, PCI reports, academic articles, and safety standards applicable to the mining sector. The analysis maps areas for improvement in operational and regulatory practices, categorizing them into three dimensions: documental, technical, and operational. The study draws comparisons with safety standards and practices exemplified by Codemin, a unit of Anglo American, which employs continuous monitoring systems and mine closure planning with environmental restoration. Based on these standards, the adoption of measures is suggested to contribute to operational safety and long-term sustainability, promoting practices aligned with responsible development.

Review of the Failure at the Flotation Tailings Storage Facility of the “Stolice” Mine (Serbia)

A detailed analysis of the accident that occurred at the flotation tailings storage facility (TSF) at the inactive mine “Stolice” in 2014 is provided in this paper. All factors that caused the accident have been analyzed, with a review of the consequences of the accident, their accident class according to the Global Industry Standard on Tailings (GISTM), and the implemented measures to rehabilitate the TSF and the surrounding area after the accident. It has been concluded that the TSF had not been properly maintained even before the accident occurred and that the unfavorable weather conditions in Serbia in the May of that year contributed to the filtration disturbance and multiple tailings spillages from the TSF. It has been stated that the consequences according to the GISTM span from “low” to “significant”, with the group of environmental consequences having the highest rank (3). Although the accident occurred without recorded human casualties, with the damage being of a local nature, it is considered one of the most significant accidents at a TSF in Serbia in the last 20 years. The reconstructed TSF is considered stable now, with a low-to-medium risk of failure.

Resource Recovery from Abandoned Mine Drainage Galleries via Ion Exchange: A Case Study from Freiberg Mining Area, Germany

The discharge of metal-loaded mining-influenced waters can significantly pollute downstream water bodies for many kilometers. Addressing this issue at the earliest discharge point is crucial to prevent further contamination of the natural environment. Additionally, recovering metals from these discharges and other sources of contamination can reduce the environmental impacts of mining and support the circular economy by providing secondary raw materials. This study focused on optimizing zinc recovery from mining-influenced water in the Freiberg mining region in Germany, where significant loads of zinc are released into the Elbe River. By employing pretreatment techniques, conducting 100 mL scale ion-exchange column experiments, and refining the regeneration process, we aimed to identify optimal conditions for efficient zinc removal and recovery. Initial tests showed that aminophosphonic functionalized TP 260 resin had a high affinity for aluminum, occupying 93% of the resin’s capacity, while zinc capacity was limited to 0.2 eq/L. To improve zinc recovery, selective precipitation of aluminum at pH 6.0 was introduced as a pretreatment step. This significantly increased the zinc loading capacity of the resin to 1 eq/L. Under optimal conditions, a concentrated zinc solution of 18.5 g/L was obtained with 100% recovery. Sulfuric acid proved more effective than hydrochloric acid in eluting zinc from the resin. Further analysis using SEM-EDX revealed residual acid on the resin, indicating a need for additional study on long-term resin performance and capacity variation. The research also highlighted the environmental impact of the Freiberg mining area, where three drainage galleries currently contribute nearly 85 tons of zinc annually to the Elbe River. This study underscores the feasibility of efficient zinc recovery from these point sources of pollution using advanced ion-exchange processes, contributing to circular economy efforts and environmental conservation.

Hydrological classification of mine pit lakes using modelling experiments

With the growing global prevalence of open-pit mining activities, there is an increasing necessity for sustainable mine life cycle plans with an early outlook towards mine closure. A major consideration in mine closure planning is the potential formation of lakes in the mine void and how these “pit lakes” can be managed to minimise risks and, if possible, create benefits. Understanding the long-term interactions between pit lakes, groundwater, and surface water systems is essential for that purpose. While numerous site-specific studies have been undertaken, there have been no studies that aim to provide a general, broadly applicable understanding of how pit lake hydrology relates to geographical context, and no efforts to hydrologically classify pit lakes using geographical criteria. This research employs an integrated generic pit lake water balance model to examine mine pit lake interactions with the surrounding surface water and groundwater. Simulating 243 scenarios, the influence of five input factors (climate, hydraulic conductivity, regional groundwater level, catchment area and pit slope) on pit lake behaviour up to 6000 years beyond the closure of the mine was considered. The assessment focused on four pit lake hydrological attributes once the system reached equilibrium: water level, time to equilibrium, the fraction of days where the pit recharges groundwater, and the fraction of days where there is surface overflow from the lake. All scenarios were assigned to one of five hydrological classes based on the interactions between the pit lake and the surrounding surface water and groundwater. Our findings show that, in many contexts, general data on climate type and subsurface hydraulic conductivity can yield reliable predictions of a pit lake's long-term hydrological classification without having to develop a detailed, site-specific pit lake model. The classification needs improvements in non-arid climates where inter-annual variation in rainfall is pronounced. The pit lake classification is particularly valuable for first-pass risk assessments to determine whether site-specific modelling is required.

Engagement strategies in the context of the Itabira mine closure: impacts and stakeholder participation

Purpose: This article aims to propose and apply a set of analytical categories for evaluating engagement in mine closure processes. Design/methodology/approach: The qualitative research adopts a case study strategy considering the singularity of the phenomenon studied. The mine project analyzed is the country's first large-scale closure, scheduled for 2041, with the potential to influence future processes. Data collection involved observation, documentary analysis, and interviews. Sixteen interviews were conducted with representatives from the public power, community, organizations, and the company. The research strategy chosen was content analysis using the analytical categories raised in the literature review and triangulation of data collection sources. Findings: The results highlight the importance of the mining company's active role in constructing the city's post-mining future, collaborating to reconvert socio-economic dynamics, and fostering a trusting relationship with the community. However, the company remains distant from the debate. Interviews revealed a paternalistic relationship between the mining company that guides engagement in a predominantly unilateral flow, with communication directed to meet its interests. Originality/value: This research fills a gap in the existing literature by focusing on engagement in a vulnerable context. It contributes to the theoretical advancement of the main characteristics of engagement in mine closure processes and for dialogue practices with communities to favor sustainable territory development in the post-mining period.

Semi-continuous cultivation of microalgae to treat coal mine effluent in pilot scale: Nutrient removal, biodesalination and fatty acid composition analysis

Coal excavation is associated with discharge of an enormous amount of mine water rich in salt and trace metal ions, which require efficient treatment before use. Considering the potentiality of microalgae for high salt tolerance, salt removal and metallic pollutant removal from aqueous system, present study focuses semi-continuous cultivation of candidate microalgae Chlorella pyrenoidosa (NCIM 2738) in bubble column reactor (BCR) and open raceway pond (ORP) for nutrient supplemented coal mine effluent (NSCME) treatment. In between different hydraulic retention times (HRTs), HRT 6 d provide maximum average biomass productivity of 950 mg L−1 d−1 in BCR and 728.4 mg L−1 d−1 in ORP. HRT 9 d facilitates a maximum lipid content of 1.8 g L ̶ 1 in BCR and 1.4 g L ̶ 1 in ORP. Further, HRT 9 d had the maximum COD removal efficiency (96.5 % in BCR and 94.2 % in ORP) and maximum salinity removal efficiency (93 % in BCR and 92 % in ORP). Fatty acid methyl esters (FAME) characterization highlighted potential biodiesel applicability with cetane number (CN) of 53.94. Energy dispersive X-ray spectroscopy (EDS) revealed an excess amount of salt and metal ions deposition on the surface of harvested microalgae samples. Outdoor large-scale C. pyrenoidosa cultivation can be integrated with coal mine closure plans to meet sustainable development goals (SDGs) 6, 7 and 13.

Land use & land cover dynamics and its relationship with nitrate pollution in groundwater around inactive mine areas using geospatial techniques, SW part of Cuddapah basin, Southern India

Geospatial maps can show how the ineffective operations of inactive mines affect water and aquifer quality. As such, the purpose of this study is to assess the impact of mining and irrigation on the aquifer ecosystem through the evaluation of LULC and slope maps through the application of Landsat 8 OLI/TIRS and DEM data. A total of 50 groundwater samples were prepared from villages in the close proximity to inactive mines during pre and post monsoon periods in 2021. The results of the analysis revealed alarming statistics, that 14% of groundwater samples exceeded the WHO nitrate limit in pre & post monsoon season, indicating a high-risk in the study area. According to guidelines (USEPA, 2014), 34% in pre-monsoon and 26% post-monsoon of samples exceeded the THI levels for adults and children respectively, indicating non-carcinogenic health risks. In addition, 80% of the samples in both seasons exhibited high NPI values, indicating nitrate contamination associated with blue baby syndrome. From the Geospatial analysis the findings from the LULC classification indicate that there has been a significant increase in cropland area from 2016 to 2021 due to changes in forest land, fallow land, and water resources. These problems have been exacerbated by the expansion of cultivated land, which has increased from 71.1 square kilometers in 2016 to 118 square kilometers in 2021, accounting for 13.1% of the total area. This expansion, coupled with elevated water body resource availability, has compounded the nitrate pollution including in intensely irrigated regions. The slope map analysis revealed that the inactive mines occur at low slope, high rainfall areas and these are compounded by runoff from other sources such as domestic and agricultural wastes. For these matters, sealing and remediating these inactive mines is essential so as to prevent further nitrate leakage.

Climate changes at mine closure: a systematic review

This systematic review addresses the implications of climate change on mine closure processes, aiming to identify, analyze, and synthesize recent literature on how climate change influences the rehabilitation of mined areas, environmental risks, the safety of remaining structures, and the long-term sustainability of closure projects. Through a methodology of selecting scientific articles, articles published between 2020 and 2024 found in the Capes/CAfe database were analyzed. The analysis covered the climatic impacts on increasing temperatures and changes in precipitation patterns in relation to soil erosion, water management, and revegetation in mine closure processes. The results highlight challenges and opportunities arising from extreme weather events, which compromise the stability of mine structures, and the noted absence of Emergency Action Plans for dealing with extreme events, which hinders decision-making and the implementation of control measures. Recommendations include the development of adaptive practices and the incorporation of advanced environmental monitoring to mitigate risks and promote sustainability in mine closure, as well as being essential to increase environmental resilience.

Method of selecting the optimal variant of mine closure with the possibility of capturing methane from underground excavations

Method of selecting the optimal variant of mine closure with the possibility of capturing methane from underground excavations

Global Perspectives on Laterite Mining and Extraction and its Environmental Implications for Nigeria

This paper explores the economic, environmental and social aspects of laterite mining techniques in Nigeria and around the world. Tropical and subtropical climates are home to the rich iron and aluminium oxide-containing soil and rock known as laterite. The article examines the several kinds of laterite deposits found in Nigeria, such as siliceous, bauxitic and ferruginous laterites. The economic significance of laterite mining is derived from its contribution to the construction, steel, iron and aluminium sectors. But there are also serious environmental problems associated with laterite mining like soil erosion, water contamination and deforestation. The energy-intensive character of mineral processing may increase emissions of greenhouse gases. Uncontrolled mining operations have the potential to uproot communities, worsen social injustices and fuel violence. This paper highlights the weaknesses of the regulatory framework in Nigeria, including weak enforcement, inadequate community engagement and limited financial provisions for mine closure and rehabilitation, Laterite mining offers economic benefits through the provision of materials for building and road construction as well as the production of aluminium, iron and other valuable minerals. Finally, governments should implement stricter enforcement mechanisms for existing mining regulations.

Geospatial Analysis of the Socioeconomic and Demographic Effects of Historic Coal Mining in the Greater Pittsburgh Region, Pennsylvania, USA

A geospatial model was developed to statistically assess the socioeconomic effects of coal mining in the greater Pittsburgh, Pennsylvania area by integrating home sale data, abandoned mine lands (AML) inventory “problem area” sites, and census demographic information. Results indicated that homes located within problem areas sold for an average of 28% ($58,600) less than homes outside of these regions. Demographic data revealed a notable disparity in the population distribution within Allegheny County mining problem areas as having a statistically significant larger Black population. This same trend was even more pronounced in urban areas. The study also established that areas influenced by past mining activities had a higher proportion of individuals without formal postsecondary education. Logistic regression models were created to analytically evaluate the relationship between predictor variables, specifically home sale price and Community Needs Index, to the probability of being situated within mining problem areas. The home sale analysis indicated a negative correlation between sale prices and the likelihood of residing in a mining-affected zone, implying that properties with lower prices are more commonly situated in these impacted areas. The CNI logistic regression model revealed a correlation between the probability of living in a mining problem area and overall higher community needs.

Modeling and Mitigating Gas Hazards during Potash Mine Closure

The planned closure of potash mines achieved through the injection of highly mineralized brines into the worked-out area is a complex process. A critical concern arises when brines obstruct the aerodynamic connections between the flooded mine’s airspace and the atmosphere, potentially leading to the formation of closed cavities where explosive gases can accumulate. To address this hazard, it is imperative to develop systems capable of extracting the gas–air mixture from the unflooded part of the worked-out area. Two distinct scenarios are examined: the first involves controlled flooding with saturated brines, while the second contemplates flooding resulting from a hypothetical breakthrough of supra-salt strata, leading to the ingress of groundwater into the worked-out area. A novel mathematical model is introduced to predict the evolution of gas–air mixture parameters in the unflooded part of the worked-out area. Utilizing this model, we assess the effectiveness of proposed measures designed to eliminate explosive gases from the worked-out area. Specifically, a pipeline system is proposed for the removal of gases. The findings from this study contribute valuable insights into ensuring the safe and efficient closure of potash mines, shedding light on potential risks and effective mitigation strategies for gas-related hazards during planned flooding.

The role of pit lake thermal dynamics on the thermal performance of ground heat exchangers

The addition of ground heat exchangers (GHEs) to a pit lake’s basin has the potential for abundant, clean and renewable geothermal energy extraction using shallow geothermal systems. Basin-embedded GHEs avoid direct interaction with mine water, which has been shown to impact efficiency and longevity in mine open-loop geothermal systems negatively. The now accelerated closure of open-pit coal mines presents itself as an opportunity to use this technology. However, no guidelines currently exist for designing or operating GHEs embedded in the sediment of water bodies. Furthermore, the two-way coupling between the complex annual thermal fluid dynamics that lakes are naturally subjected to and heat fluxes on the sediments and the GHE system has not been explored. In this study, we develop and validate finite element models to assess the relevance of lake thermal stratification in the performance of a geothermal system embedded in water bodies basins, e.g., on open-pit mine closures, under temperate residential thermal loads. The results show that the pit lake’s role as a thermal sink improves significantly when the lake’s thermal dynamics are accounted for, with an increase of up to 292% in the lake’s available energy budget. A minor variation in energy budget (~8%) was found whether the lake is modelled explicitly or simplified as a transient Dirichlet temperature boundary condition. This small difference vanishes if horizontal circulation along the lake is considered, highlighting the lake’s thermal energy potential. Finally, the impact on the GHE Coefficient of Performance (COP) is evaluated, with a maximum of ~15% difference among all cases.

Coal mine closure substantially increases terrestrial water storage in China

The transition away from coal involves the widespread closure of coal mines. While the potential adverse consequences of these closures on industry and the local economy have received considerable attention, empirical evidence on the benefits of water resources remains limited. Here, we quantify the effect of coal mine closure on terrestrial water storage (TWS) in China using satellite data and a staggered difference-in-differences approach. Our findings indicate a rapid restoration in TWS following closure, with coal mine closures increasing TWS by an average of 18.8 ± 8.9 mm per year. This increase in TWS is primarily attributable to augmented groundwater storage and reduced industrial water usage. Furthermore, our analysis suggests that these TWS gains exceed the indirect impacts of climate change mitigation efforts on water resources, potentially complementing such strategies in water-stressed regions. Overall, our study underscores the positive environmental impact of coal mine closures on water availability in China, potentially facilitating the transition away from coal production and enhancing the sustainability of the energy transition.

Seed endophytes and rhizosphere microbiome of Imperata cylindrica, a pioneer plant of abandoned mine lands.

Some plant-associated microorganisms could improve host plants biotic and abiotic stress tolerance. Imperata cylindrica is a dominant pioneer plant in some abandoned mine lands with higher concentrations of heavy metal (HM). To discover the specific microbiome of I. cylindrica in this extreme environment and evaluate its role, the microbiome of I. cylindrica's seeds and rhizosphere soils from HM heavily contaminated (H) and lightly contaminated (L) sites were studied. It was found that HM-contamination significantly reduced the richness of endophytic bacteria in seeds, but increased the abundance of resistant species, such as Massilia sp. and Duganella sp. Spearman's rank correlation coefficient analysis showed that both Massilia sp. and Duganella sp. showed a significant positive correlation with Zn concentration, indicating that it may have a strong tolerance to Zn. A comparison of the microbiome of rhizosphere soils (RS) and adjacent bare soils (BS) of site H showed that I. cylindrica colonization significantly increased the diversity of fungi in rhizosphere soil and the abundance of Ascomycota associated with soil nutrient cycling. Spearman's rank correlation coefficient analysis showed that Ascomycota was positively correlated with the total nitrogen. Combined with the fact that the total nitrogen content of RS was significantly higher than that of BS, we suppose that Ascomycota may enhance the nitrogen fixation of I. cylindrica, thereby promoting its growth in such an extreme environment. In conclusion, the concentration of HM and nutrient contents in the soil significantly affected the microbial community of rhizosphere soils and seeds of I. cylindrica, in turn, the different microbiomes further affected soil HM concentration and nutrient contents. The survival of I. cylindrica in HM severely contaminated environment may mainly be through recruiting more microorganisms that can enhance its nutrition supply.

Transitional and Post-Mining Land Uses: A Global Review of Regulatory Frameworks, Decision-Making Criteria, and Methods

Post-mining land management is an integral part of surface mining and quarrying operations. In this context, the questions raised concern what course of action is mandated by laws and regulations; what type of land reclamation should be implemented, taking into account the site-specific conditions prevailing in each mining area; what are the appropriate land uses; and by what criteria and methodology can these be determined? The literature review conducted as part of the present study revealed that in addition to the traditional 4R actions of land management, namely remediation, restoration, reclamation, and rehabilitation, two more actions, repurposing and co-purposing, have now been added, with the purpose to address the social and economic impacts of mine closures. Furthermore, numerous land uses were documented and categorized into 11 classes, 38 sub-classes, and 119 alternatives. Nine criteria for selecting land uses were identified, expressed through 72 attributes that served as input information for 22 multicriteria methods, which, in most cases, were applied in combination of two or more.

Multi-decadal geochemical evolution of drainage from underground coal mines in the Appalachian basin, USA

Coal mine drainage (CMD) in Appalachia is a widespread source of dissolved metals, SO4, and acidity that can degrade aquatic habitats and water supplies for decades following mine closure and flooding. In the bituminous coalfield of Pennsylvania, the Irwin Coal Basin (ICB) contains a series of partly to completely flooded, abandoned underground mines separated by leaky barriers within the Pittsburgh coal seam. CMD originated throughout the basin from minepool aquifers that formed after mine closures dating from 1910 to 1957. Historical and recent water quality data for eight CMD sites across the ICB, plus mineralogy and cation-exchange capacity of overburden lithologies, were analyzed to quantify important reactants and evaluate spatial and temporal water-quality trends. As overburden thickness and residence time increase along a ~ 50-km flowpath northeast to southwest in the basin, CMD becomes more alkaline, and Na concentrations increase. Since the 1970s, all eight ICB discharges have become less acidic, with exponential decreases in acidity, SO4, and Fe concentrations; only two CMD remain net-acidic (acidic pH at equilibrium). Exponential decay models that include a steady-state asymptote consistent with background groundwater chemistry and siderite equilibrium describe the early-stage, rapid contaminant concentration decay immediately after the “first flush” (initial flooding) and the progressive evolution toward late-stage background conditions. A geochemical evolution PHREEQC model indicates that spatial and temporal trends in pH, net-acidity, SO4, Fe, and major cations could be explained by the continuous dilution of first flush water by ambient groundwater combined with sustained water-mineral reactions involving pyrite and carbonates (calcite, dolomite, siderite) plus cation-exchange by clays (illite, chlorite, mixed-layer illite/smectite). These data and model results indicate that 1) cation-exchange reactions enhance calcite dissolution and alkalinity production, resulting in the evolution of CMD to Na-SO4-HCO3 type waters, and 2) siderite equilibrium could maintain dissolved Fe >16 mg/L over the next 40 years.

Identifying Factors Influencing Surface Deformations from Underground Mining Using SAR Data, Machine Learning, and the SHAP Method

The article presents the results of significance analyses of selected mining and geological variables for an area of underground mining activity. The study area was a region of an underground copper ore mine located in southwest Poland. The input data consisted of satellite radar data from the Sentinel 1 mission as well as mining and geological data. The line-of-sight subsidence, calculated with the use of the small baseline subset method and arranged in time series, was decomposed to extract the vertical component. The significance analysis of individual variables for the observed surface subsidence was performed using the SHapley Additive exPlanations method for the XGBoost machine learning model. The results of the analysis showed that the observed ground surface subsidence velocities were most influenced by the thickness of the PZ3 layer, which is located approximately 200 m above the roof of the mined seam, the thickness of the seam, and the timing of mining. It was also found that the proposed model was able to detect a nonlinear relationship between the analyzed excavations. The most significant influence on ground subsidence over mine excavations are mining parameters such as the spatially averaged thickness of the deposit and the time since liquidation of the deposit. The proposed approach can be successfully employed in planning both mining operations and mine closure in such a manner that the environmental impact is minimized.

Changed life worlds and survival strategies in disintegration after the regime change in Hungary: a former industrial town in the shadow of the factory giant

ABSTRACT In the literature of post-1989 Eastern European history, the disintegration of traditional industries and the decline of the factory towns that had been based on them is a well-known topic. Less attention has been paid to the transformation of the countryside or the villages that often served as the supportive network for the factory towns, a phenomenon that was also very typical of Hungary, where migrant or commuter workers became the subject of academic interest long before the collapse of state socialism. This study offers an international perspective and case study of the catchment area of Ózd, a former industrial and factory city located in northeastern Hungary that was once an important centre of Hungarian metallurgy and mining. In my analysis I address the related topic of how the decline of traditional industries affected this former industrial city and its surrounding villages, whose inhabitants mostly worked in industry until the industrial landscape and its society disappeared. This study focuses on Ózd and its surroundings, where the survival and sustenance of the population was directly threatened by the closure of collective farms, factories, plants and mines in the area.

Implementation of pumped hydro/photovoltaic systems in mining-degraded areas: a case study in Quadrilátero Ferrífero, Minas Gerais, Brazil

This work presents a proposal for the transformation of mining-degraded areas into renewable energy installations, converting deactivated mine pits, in the Quadrilátero Ferrífero (QF) region in state of Minas Gerais (MG), Brazil, into reservoirs for Pumped Storage Hydropower (PSH). Additionally, it proposes the alteration of adjacent areas impacted by mining extraction process, through their conversion into Photovoltaic Power Plants (PV). This measure has the potential to turn mining liabilities into sources of energy with lower environmental impact and sustainability for society. This process allows energy to be stored in the form of hydraulic batteries, which can mitigate the effects of intermittency of photovoltaic generation in the electrical grid. The presented methodology involves mapping deactivated mines, calculating the energy potential of the coupled PSH and PV systems, and conducting an economic feasibility study for PSH implementation. The work includes a case study discussing potential local environmental impacts and the energy potentials of this solution. The case study resulted in identifying a suitable pair of mine pits for a PSH in the QF, capable of supplying the electrical grid with approximately 234.3 MW, with the generated energy cost ranging between U$112.26/MWh to U$167.22/MWh. It is concluded that utilizing inactive mines as PSH reservoirs and installing PV in adjacent mining-degraded areas are innovative and technologically feasible strategies. Economically, their implementation will depend on the market price of energy.