Mining Research Articles

Efficient remediation of cadmium and lead contaminated soil in coal mining areas by MICP application in hydrothermal carbon-based bacterial agents: Nucleation pathways and mineralization mechanisms

The development of industrial mining has resulted in a large amount of Cd and Pb polluting the soil in mining areas, and leads to adverse health effects on the life of both plants and animals. Here, a soft template method was conducted to prepare hydrothermal carbon (HC) with regular morphology, which assisted with Bacillus pasteurii to induce calcite precipitation for decontamination of mining soil. Soil remediation experiments over 30 days of remediation with an HC microbial agent (HCMA) resulted in 89.4% and 87.8% decrease in the amount of leached Cd and Pb, respectively. The content of exchangeable Cd and Pb decreased by 76.1% and 81.0%, respectively. At the same time, soil fertility significantly improved. The electrostatic potential and surface charge distribution of extracellular polymeric substances (EPS) and sodium citrate (NaCit) were analyzed using DFT simulations, their nucleophilic and electrophilic regions were determined, and the nucleation mechanism was determined. The DFT results indicated that the oxygen-containing groups of EPS and NaCit had strong negative electrostatic potential and electronegativity, which could cause Cd2+, Pb2+, and Ca2+ to aggregate on their surfaces. They also combined with CO32− produced by urease during the decomposition of urea, resulting in Cd2+ and Pb2+ being encapsulated by calcium carbonate to form a coprecipitate. X-ray diffraction analyses revealed that the precipitate was mainly calcite calcium carbonate, which is more stable and less prone to secondary leaching of HMs. The gathered data prove the significant role of HCMA in remediation of mining soil contaminated with Cd and Pb.

Coupling mechanism of trace elements and maceral in medium and high sulphur coal in the Jurassic terrestrial environment of Zhongyuan mine in the Hengshan mining area and adjacent areas

ABSTRACT Considering the urgency of resource utilization and environmental protection, the geochemistry of anomalous trace transition metal elements in coal formed in terrestrial environments has been studied using methods such as inductively coupled plasma atomic emission spectrometry analysis, electron probe micro-area analysis, sequential chemical extraction procedures, and correlation analysis. The results indicate that minerals in the coal samples included pyrite, kaolinite, quartz, dolomite, calcite, and celestite. Furthermore, compared with the average values of coals in China and the upper continental crust, the coal samples were rich in transition metal trace elements such as Ni, Cr, and Sr and were deficient in Be, Cd, Cu, Co, Ga, Mo, Sb, Tl, V, Zn, and Ti. We found that Ni preferentially occurred in the organic matter over minerals, while Cr primarily bonded with sulfide minerals and to a lesser extent with the iron-manganese oxide minerals. Sr had a low correlation with organic matter but adhered to clay minerals and celestite. Ni enrichment in coal samples was the result of terrigenous input, while the Cr enrichment was related to intrusion of magmatic hydrothermal fluids. Sr enrichment was caused by the presence of SO4 2- in the terrigenous debris and the influence of Sr-rich water underground.

Intimate microbe-water-mineral interactions mediate alkalization in the pyroxene-rich iron ore mines in Panxi area, Southwest China

In contrast to acid mine drainage, the microbial assembly and (bio)geochemical processes in alkaline mine conditions remain under-investigated. Here, microbe-water-mineral interactions were systematically investigated in two representative iron mines with alkaline conditions in the Panxi mining area, Southwest China. Compared to reference riverine samples less interfered by mining activities, the iron ore samples, composed of vanadium-titanium magnetite and pyroxene-rich bedrocks, exhibited elevated levels of Fe, HCl-extractable Fe(II), total sulfur, nitrate and sulfate, but lower total carbon (TC). Meanwhile, the mine drainage showed significantly higher sulfate, but lower TC concentrations than the riverine samples. Intriguingly, the Serpentinimonas spp., typically reported in serpentinites, prevailed in the microbial communities from the mine samples exhibiting higher pH. This suggests that the alkaline environments in Panxi mines result from serpentinization-like reactions. Enrichment of Thiobacillus spp. was observed in the mine-dwelling microbial communities, positively correlated with total sulfur, sulfate, nitrate, and Fe(II). Genome-resolved metagenomics suggested a chemoautotrophic lifestyle for the Thiobacillus species (e.g., carbon fixation, sulfur oxidation, and oxygen respiration), which may generate H+ and mitigate alkalization. This study provides valuable insights into progressive development of alkaline mine ecosystems and offers guidance for developing appropriate engineering strategies to restore the abandoned alkaline mines.

Research on the Characteristics of Seepage Failure in the Surrounding Rock (Coal) of the Goafs

During mining, the brittle fracture structure of coal makes it highly susceptible to disturbance, leading to changes in the permeability of the coal seam from non-conductive to water-conductive, which poses a significant threat to the stability and safety of coal pillars in goafs. Therefore, understanding the damage mechanisms of coal during water–rock interactions is crucial for ensuring mine safety. In this paper, based on laboratory seepage tests, the impact of hydrodynamic forces on the microstructure of fissured coal and its subsequent effect on permeability is examined. The study found that increasing confining pressure causes the “closure” of coal fissures, leading to a reduction in permeability. Additionally, during the initial stage of seepage, fine particles within the coal samples are mobilized due to seepage damage, leading to channel blockages and further reductions in permeability. However, as seepage continues, the hydraulic channels eventually open fully, resulting in a sharp increase in permeability. Furthermore, using a two-dimensional fracture seepage model, the study investigated how the scale of fractures in the water-conducting channels influences seepage behavior. A critical fracture width method was proposed to predict permeability surges, offering a new approach for analyzing the stability of coal pillars in mining areas.

Arbuscular mycorrhizal fungal inoculum and N2-fixing plants in ecological reclamation of arid mining areas: nutrient limitation of the moss biocrust microbiome.

Ecoenzymatic stoichiometry can reflect the ability of soil microorganisms to acquire energy and nutrients and to determine their response to environmental stresses. However, the drivers of metabolic limitation of the moss biocrust microbiome during the ecological restoration of coal mining areas are poorly understood. Therefore, in this study, enzymatic stoichiometry modeling and high-throughput sequencing were used to simultaneously determine moss biocrust microbial metabolic limitation and its relationship with moss biocrust nutrients and arbuscular mycorrhizal fungal (AMF) diversity in five arid and semi-arid revegetation types (Hippophae rhamnoides, Amorpha fruticosa, Cerasus humilis, Cerasus szechuanica, and Xanthoceras sorbifolium) and two microbial treatments (AMF-inoculated and uninoculated). The activities of moss biocrust carbon (C)-, nitrogen (N)-, and phosphorus (P)-acquiring enzymes and organic carbon fractions in the AMF-inoculated treatment were significantly higher than those in the uninoculated control. Moss biocrust microbial community C and P limitations were observed in the five revegetation types, with lower limitation in general in the AMF-inoculated treatment. Dinitrogen-fixing plants (Amorpha fruticosa and Hippophae rhamnoides) significantly mitigated moss biocrust microbiome C and P limitation, especially in the AMF-inoculated treatment. Furthermore, partial least squares path modeling (PLS-PM) shows that moss biocrust organic carbon fractions (- 0.73 and - 0.81 of the total effects, respectively) and AMF diversity (- 0.73 and - 0.81 of the total effects) had negative effect on microbial C and P limitation, suggesting that more efficient active nutrients and AMF diversity are important factors alleviating limitation of moss biocrust microbial metabolism. This indicates that moss biocrust microbial communities under N2-fixing species with AMF inoculation were more stable under environmental stress; thus, AMF inoculation and/or N2-fixing plants may be recommended as preferred options for the ecological restoration of arid mining areas.

Study on Roadway Layout and Supporting Method of High Intensity Mining Disturbance Bottom Coal Recovery Working Face (A Case Study in Xiagou Mine)

After more than ten years of mining, the subsequent replacement resources of 4 # coal in Xiagou Mine are insufficient. In order to ensure the normal production of the mine, Xiagou Coal Mine needs to recycle the lower layer resources of 4 # coal seam. The design issue of the roadway layout and support mode for the bottom coal recovery left by the strong disturbance in the Xiagou Mine has to be resolved. Through theoretical evaluation and computer simulation, this study investigates the appropriate staggered distance of the roadway layout following upper slicing mining as well as the distributed stress law of the roadway under various staggered distances. Finally, the reasonable external offset is determined. Based on the actual working condition of 404 mining area in Xiagou Mine, the matching roadway support design is put forward. Finally, the roadway layout and support design are validated through the use of computer modeling and field monitoring. The findings demonstrate that when there is a significant disruption in the upper layer, the roadway layout of bottom coal recovery should adopt the external staggered layout and the reasonable external staggered distance is 6 m. At this time, the fluctuation degree of nearby rock stress, the non-uniformity of stress distribution and the uniformity of the roadway's deformation under disturbance meet the production needs. It shows that 6m layout and roadway supporting method are more reasonable, which has reference significance for roadway arrangement and support under similar engineering conditions.

Resource Utilization of Rare-Earth-Rich Biomass and Ammonia Nitrogen Effluent from Mining

The post-treatment of heavy metal-enriched plants in mining areas and the purification of ammonia and nitrogen pollution in water bodies are significant for the ecological environment of ionic rare earth mining areas. Herein, we focused on the biochar production potential of Dicranopteris pedata, characterizing biochar prepared by an oxidative modification process and an iron modification process. We conducted adsorption experiments to comparatively investigate the adsorption performance of biochar on NH4+ and studied the fertilizer application and migration toxicity of the adsorbed biochar for rare earth elements (REEs). Results indicated that ~332.09 g of biochar could be produced per unit area of D. pedata under 100% clipping conditions. The Brunauer–Emmett–Teller (BET) specific surface area of oxidized biochar (H2O2BC) increased, and the pore size of iron-modified biochar increased. The adsorption behavior of biochar toward NH4+ was well represented by the pseudo-second-order and Langmuir models. H2O2BC demonstrated the strongest adsorption of NH4+ with maximum theoretical equilibrium adsorption of 43.40 mg·g−1, 37.14% higher than that of pristine biochar. The adsorption process of NH4+ on biochar is influenced by various physicochemical mechanisms, including pore absorption, electrostatic attraction, and functional group complexation. Furthermore, the metal ions in the biochar did not precipitate during the reaction process. The adsorbed NH4+ biochar promoted the growth of honey pomelo without risking REE pollution to the environment. Therefore, it can be applied as a nitrogen-carrying rare earth fertilizer in low rare earth areas. This study provides a theoretical basis and technical support for the phytoremediation post-treatment of rare earth mining areas and the improvement of ammonia nitrogen wastewater management pathways in mining areas.

Research on Enhancing Gas Extraction Efficiency through CO2 Gas Fracturing in Outburst-Prone Coal Seams.

Given the background of significant Coal Mine gas disasters worldwide, the research and development of efficient gas control technologies have become critical to ensuring mining safety. CO2 gas fracturing (CO2-Frac), an innovative technology for Coal Mine gas control, has demonstrated efficiency in various mining areas across China. However, its application in outburst-prone coal seams is not yet fully understood. This study presents a field-scale CO2-Frac project conducted in an outburst Coal Mine in China, specifically the Pingshu Coal Mine, where the previously employed dense-borehole gas extraction technology failed to efficiently achieve gas extraction and outburst prevention. The CO2-Frac plan was evaluated through fracture propagation experiments utilizing both single-hole and dual-hole configurations, highlighting the advantages of the dual-hole CO2-Frac method. Subsequently, on-site gas extraction tests were conducted to further assess the efficacy of the CO2-Frac plan. The results indicate that (1) In the dual-hole CO2-Frac scheme, the fractured and pressure relief area expanded to approximately 26.82 m2, which is 220% larger than that of the single-hole scheme. (2) The dual-hole CO2-Frac significantly enhanced gas extraction effectiveness, increasing the flow rate from 0.026 to 0.216 m3/min in a 100m borehole, a 7.3-fold improvement. Additionally, the gas extraction period to reach the standard was reduced from 20 to 6 days. These findings conclusively demonstrate that the dual-hole CO2-Frac technique is an effective method for safe excavation in outburst-prone coal seams, providing both theoretical and practical validation for its application in similar geological settings.

Damage evolution and acoustic emission characteristics of sandstone under different true triaxial cyclic loading and unloading modes

In the process of deep coal mining, the cyclic mining disturbance behavior produces significant cyclic loading and unloading effects, to ensure safe production in the mining area, it is necessary to study the damage characteristics and acoustic emission characteristics of the rock body under different cyclic loading and unloading effects. This study developed a TAWZ-5000/3000 rock true triaxial (disturbance) test system and used it to carry out true triaxial cyclic loading and unloading tests in different modes, with acoustic emission (AE) monitoring of the deformation and damage processes. The test results proved that a large number of cycles weakens the rock’s ability to control deformation, and this weakening ability is also related to the types of cyclic loading and unloading modes. The hysteresis loop characteristics and mechanical parameters show obvious path dependence. Based on the damage equivalence method, it is found that the absolute damage parameter increases with the increase of the number of cycles in the same mode, and the accumulation rate of the cumulative damage parameter is faster; the cumulative damage parameter in the equal amplitude cyclic loading and unloading (EAC) mode is always higher than that in the other two modes. The normalized AE ring count rate in the rock samples under cyclic loading and unloading has a significant relationship with the damage percentage, and the crack extension scale function (b-value) shows the “steady increase – strong fluctuation − significant decline” trend. By analyzing the AE characteristic parameters, namely rise time/amplitude (RA) and ringing count/duration (AF), it is found that the sandstones in EAC, graded cyclic loading and unloading (GC), and stepped cyclic loading and unloading (SC) modes are mainly damaged by tension-shear and shear, respectively. By analyzing the values of the acoustic emission parameters RA-AF, it is found that the sandstone is mainly damaged by tensile shear, tensile tension, and shear under EAC, GC, and SC modes, respectively, corresponding to the rock samples’ damage patterns. The study results have important guiding significance for preventing and controlling disasters in deep mines.

New insights into uranium biomineralization mediated by Pseudomonas sp. WG2-6 in the presence of organic phosphorus: Promoting effect of extracellular polymeric substance and formation of U-P nanominerals

Microbial biomineralization significantly affects the uranium (U) behavior in the environment. However, the mechanism of microbial biomineralization of U is still not fully understood. In this study, a dominant bacterium (Pseudomonas sp. WG2–6) was isolated from U tail mining area. Abiotic precipitation tests demonstrated that U biomineralization was entirely attributed to the mediation of Pseudomonas sp. WG2–6 when the concentration ratio of exogenous β-glycerophosphate (SGP) to U was 10:1. Pseudomonas sp. WG2–6 exhibited strong immobilization ability towards U (97.59 %) according to batch experiments, and acylamide, carbonyls, and phosphate groups were the main functional groups that interacted with U. Besides, U mainly existed in the form of amorphous U-P complexes after biomineralization by Pseudomonas WG2–6, which could be converted into crystalline nano-minerals H2(UO2)2(PO4)2·8H2O in the presence of SGP. In particular, the formation and structural composition changes of extracellular polymeric substance (EPS) as well as the decrease in U4f binding energy were observed during the U biomineralization process of Pseudomonas sp. WG2–6 in the presence of SGP, indicating that EPS provided the nucleation site for the formation of stable biomineralized products. This work provides new insight into the mechanism of U microbial biomineralization and a theoretical basis for the remediation of U contaminated environments through microbial biomineralization.

Potentially Toxic Metals Enrichment in Soils of Ishiagu Mining Community, Southeastern Nigeria

This Study was carried out to evaluate potentially toxic metals enrichment, pollution and potential ecological risk in the soils of Ishiagu. The concentrations of Cadmium (Cd), Chromium (Cr), Cobalt (Co), Copper (Cu), Lead (Pb), Manganese (Mn), Nickel (Ni), Zinc (Zn), Aluminum (Al) and Iron (Fe) in soil samples from the area were analyzed by Bureau Veritas Laboratory, Vancouver, Canada, using inductively-coupled plasma optic emission spectrometry (ICP-OES). Descriptive statistics, enrichment factor, pollution load and potential ecological risk indices were employed to analyze the data in order to understand the characteristics of potentially toxic metals in the study area. The potentially toxic metals statistic show the mean values (mg/kg-1 ) of Pb, Zn, Mn, Fe, Al, Cd, Cr, Ni, Co, and Cu to be 205.7, 162, 527, 35892, 11374, 1.3, 21.6, 15, 14.6 and 11.1 respectively. The soil enrichment varied considerably between mining and non-mining areas with mining area being extremely enriched with Pb, Zn and Cd, and significantly enriched with Co, Cu, Ni and Fe. Non- mining areas are minimally enriched with all investigated metals. The soils around the mines are polluted with Pb and Cd, where both metals also pose very high ecological risks.

Evaluation of Germination and Early Seedling Growth of Different Grasses Irrigated with Treated Mine Water

Coal mining is known to have negative impacts on the environment, necessitating land rehabilitation after mining activities. Amongst the problems associated with coal mining is the accumulation of acid mine drainage characterized by large amounts of heavy metals and high acidity. The impact of these environmental problems on the ecosystem around mining areas underscores a need to devise strategies that will ensure sustainable restoration of the ecosystem integrity to ensure environmental protection. Of these, treatment of acid mine drainage using calcium sulfate dihydrate, which is subsequently used for irrigation during phytoremediation, holds great promise for restoration of open-cast mines. However, although grasses are used for rehabilitation of coal mined areas, the impacts of treated mine water on the germination, seedling emergence, and plant growth of grasses are not well known. The aim of the study was to evaluate the germination and early seedling growth responses of different forage grasses to treated mine water. Seven forage grass species were selected, with four species represented by two varieties while others were represented by one variety, totaling 11 forage grasses. For each plant entry, 100 seeds were placed in J.R. Petri’s dishes lined with Whatman No. 2 filter paper and watered with distilled and mine water to assess germination. For the seedling establishment experiment, only five species were studied, in which twenty seeds per species were sown in pots containing mine soil and irrigated using distilled and treated mine water. The final germination percentage (FGP), germination rate index (GRI), corrected germination rate index (CGRI), and T50 were determined for the germination trail and total biomass was assessed for the seedling growth trail. The highest FGP for all grasses was attained under controlled conditions, using distilled water, ranging from 38–94%. All grasses germinated when watered using treated mine water and had a FGP ranging from 20–91%. Relative to distilled water, GRI and CGRI were highest only for L. multiflorum cv AgriBoost when seeds were watered using the treated mine water. All grasses watered with treated mine water produced high biomass for the first two weeks, after which biomass production started to decline. Two grasses, Eragrostis curvula cv Ermelo and Lolium multiflorum cv Archie, showed tolerance to treated mine water irrespective of its high electrical conductivity (557 mS∙m−1). Therefore, these grasses could be used in the rehabilitation of coal-mined areas irrigated with treated mine water.

Prediction and Analysis of Surface Residual Deformation Considering the Impact of Groundwater in Mines

With economic development and coal resource exploitation, the area of mined-out zones is expanding continuously. The traditional waste disposal methods no longer meet the current demands, making it urgent to evaluate and reuse the surface stability of these mined-out zones. Surface residual deformation is a process where voids and fissures within the mined-out zones are gradually filled and compacted, affecting the overlying rock structure. Additionally, groundwater significantly impacts the strength of the overlying rock, leading to increased subsidence. Therefore, predicting surface residual deformation while considering the effects of groundwater is crucial for forecasting surface deformation and assessing stability in mined-out zones. This study, taking into account the characteristics of subsidence zones and the impact of groundwater on the compaction of fractured rock masses, uses equivalent mining height and probability integral methods to develop a predictive model for surface residual deformation incorporating groundwater effects. Predictions for the study area show that groundwater exacerbates surface residual deformation, with various deformation values ranging from 33.8% to 51.9%. The surface stability categories are divided into stable and essentially stable regions based on the residual deformation’s impact on the working face. This model fully considers the influence of groundwater on residual deformation in mined-out zones, refining existing mining subsidence theories, addressing deformation issues caused by adverse groundwater factors, and providing a theoretical basis for predicting residual deformation and evaluating stability in mined-out zones, promoting the sustainable development of land and environmental resources in mining areas.

Low carbon scheduling method of mine integrated energy system based on two-stage P2G technology

Coal mines derive a large amount of various associated resources that can be used for production and living needs during the mining process. In order to realize the recycling of coal associated resources, a typical architecture of coal mine comprehensive energy system including the recycling of coal derived resources is proposed. Firstly, according to the coal mine resource endowment and its geological characteristics, the corresponding mine integrated energy system is constructed. Then, the refined two-stage P2G technology is combined with the mine integrated energy system to realize the complete consumption of wind and light and the efficient utilization of energy. Finally, the stepped carbon trading mechanism is used to further constrain the carbon emissions and realize the further reduction of carbon emissions in the mining area. The simulation model of the integrated mine energy system is established in MATLAB and the GUROBI solver is called to solve the results. The simulation results show that the method can effectively reduce carbon emissions, realize the complete consumption of wind and light and the efficient use of energy.

Dynamic frequent subgraph mining algorithms over evolving graphs: a survey

Frequent subgraph mining (FSM) is an essential and challenging graph mining task used in several applications of the modern data science. Some of the FSM algorithms have the objective of finding all frequent subgraphs whereas some of the algorithms focus on discovering frequent subgraphs approximately. On the other hand, modern applications employ evolving graphs where the increments are small graphs or stream of nodes and edges. In such cases, FSM task becomes more challenging due to growing data size and complexity of the base algorithms. Recently we see frequent subgraph mining algorithms designed for dynamic graph data. However, there is no comparative review of the dynamic subgraph mining algorithms focusing on the discovery of frequent subgraphs over evolving graph data. This article focuses on the characteristics of dynamic frequent subgraph mining algorithms over evolving graphs. We first introduce and compare dynamic frequent subgraph mining algorithms; trying to highlight their attributes as increment type, graph type, graph representation, internal data structure, algorithmic approach, programming approach, base algorithm and output type. Secondly, we introduce and compare the approximate frequent subgraph mining algorithms for dynamic graphs with additional attributes as their sampling strategy, data in the sample, statistical guarantees on the sample and their main objective. Finally, we highlight research opportunities in this specific domain from our perspective. Overall, we aim to introduce the research area of frequent subgraph mining over evolving graphs with the hope that this can serve as a reference and inspiration for the researchers of the field.

Geochemistry in Geological CO2 Sequestration: A Comprehensive Review

The increasing level of anthropogenic CO2 in the atmosphere has made it imperative to investigate an efficient method for carbon sequestration. Geological carbon sequestration presents a viable path to mitigate greenhouse gas emissions by sequestering the captured CO2 deep underground in rock formations to store it permanently. Geochemistry, as the cornerstone of geological CO2 sequestration (GCS), plays an indispensable role. Therefore, it is not just timely but also urgent to undertake a comprehensive review of studies conducted in this area, articulate gaps and findings, and give directions for future research areas. This paper reviews geochemistry in terms of the sequestration of CO2 in geological formations, addressing mechanisms of trapping, challenges, and ways of mitigating challenges in trapping mechanisms; mineralization and methods of accelerating mineralization; and the interaction between rock, brine, and CO2 for the long-term containment and storage of CO2. Mixing CO2 with brine before or during injection, using microbes, selecting sedimentary reservoirs with reactive minerals, co-injection of carbonate anhydrase, and enhancing the surface area of reactive minerals are some of the mechanisms used to enhance mineral trapping in GCS applications. This review also addresses the potential challenges and opportunities associated with geological CO2 storage. Challenges include caprock integrity, understanding the lasting effects of storing CO2 on geological formations, developing reliable models for monitoring CO2–brine–rock interactions, CO2 impurities, and addressing public concerns about safety and environmental impacts. Conversely, opportunities in the sequestration of CO2 lie in the vast potential for storing CO2 in geological formations like depleted oil and gas reservoirs, saline aquifers, coal seams, and enhanced oil recovery (EOR) sites. Opportunities include improved geochemical trapping of CO2, optimized storage capacity, improved sealing integrity, managed wellbore leakage risk, and use of sealant materials to reduce leakage risk. Furthermore, the potential impact of advancements in geochemical research, understanding geochemical reactions, addressing the challenges, and leveraging the opportunities in GCS are crucial for achieving sustainable carbon mitigation and combating global warming effectively.

Research on optimization of mining methods for broken ore bodies based on interval-valued pythagorean fuzzy sets and TOPSIS-GRA.

Identifying the optimal mining methods plays a pivotal role in ensuring both economic efficiency and environmental sustainability. This study aims to propose a model that combines interval-valued Pythagorean fuzzy sets (IVPFS) and TOPSIS-GRA to select the optimal mining method for broken ore bodies. First, a multi-factor comprehensive evaluation system, including economic, safety, and technical aspects, was established. IVPFS was introduced to express the fuzzy information of the decision-making process within the evaluation system. Additionally, an objective method combining the principle of fuzzy entropy measurement with EWM was proposed to determine the weights of fuzzy information. This method distinguished the importance of decision-makers and indicators. Then, an integration of distance and similarity (TOPSIS-GRA) was employed for ranking alternative solutions to select the optimal one. This model was applied to the decision-making problem of mining methods for the broken and difficult-to-mine ore bodies in the Tanyaokou mining area. Initial fuzzy evaluation information was obtained by having decision-makers score the mining methods. Results showed that the comprehensive scores of four alternatives are 0.5172, 0.4683, 0.5192, and 0.5465, respectively. The optimal method was the point-pillar upward horizontal layered filling mining method. Finally, the sensitivity analysis confirmed the stability of the model. The comparative results under different fuzzy environments (PFS and TFS) demonstrated the strong capability of IVPFS in handling fuzzy information for optimizing mining methods.

Spatial and Temporal Characteristics and Driving Force Analysis of Ecological Environmental Quality in Fengfeng Mining Area with Remote Sensing Ecological Index of PM2.5 Concentration

The Fengfeng mining area is an important coal-producing area in China and crucial environmental problems have been caused by large-scale exploitation of coal mines. The spatio-temporal evolution and driving factors of the ecological environment quality in this area must be explored for promoting the transformation of coal-based cities. Based on Landsat data of the Google earth engine （GEE） platform, this study constructed a new remote sensing-based ecological index （RSEInew） for the Fengfeng mining area from 2000 to 2020. The spatial and temporal evolution of RSEInew and its driving factors were evaluated by using trend analysis and geographic detector methods. The results showed that： ① From 2000 to 2020, the RSEInew of the Fengfeng mining area presented a fluctuating increasing trend （trend = 0.002 2）, and the proportion of good and excellent ecological environmental quality showed an increasing trend, rising from 24.80% in 2000 to 65.54% in 2020. ② The change in the RSEInew grade indicated that the proportion of significant improvement （3 and 4） of ecological environment quality grade in the Fengfeng Mining area from 2000 to 2020 was 10.21%, which was mainly distributed in Hexun town and Yijing town in the northwest of the Fengfeng mining area. The proportion of significant degradation （-3 and -4） was only 1.58%, mainly scattered in Linshui town and Dashe town. ③ RSEInew values increased significantly during 2000-2020 in the area accounting for 18.29%, mainly distributed in the central and northern areas and the western fringe of the Fengfeng mining area. The significantly reduced area accounted for 9.25%, mainly concentrated in the eastern area of the Fengfeng mining area. The coefficient of variation results showed that the areas with high fluctuation of RSEInew were mainly concentrated in Pengcheng town and Linshui town in the middle and eastern Fengfeng mining area. ④ From the perspective of influencing factors, the average q value of land use type （X6） during 2000-2020 was 0.290, which was much higher than other factors. The q value of social and economic factors showed an increasing trend, indicating that the spatial distribution of ecological environment quality in this region was increasingly strongly influenced by human activities. The interaction results showed that land use change was the key factor influencing ecological environment quality in the Fengfeng mining area.

Seismic imaging of deep‐seated gold deposit and host rocks through a reappraisal of legacy seismic data in the Fochville mining area, South Africa

AbstractReappraisal of legacy reflection seismic data has shown to deliver value in mineral exploration, particularly in brownfield settings. In this work, we demonstrate how the reappraisal and processing of legacy reflection seismic data can be advantageous in the mineral exploration industry. We use today's standard seismic processing tools to improve the imaging of deep and complex geological structures that host mineral deposits. The recovered and processed 25.3 km long legacy seismic profile in this study was acquired in 1983 by the Gold Division of Anglo‐American as part of the Witwatersrand Gold Fields exploration program. This study aims to improve the imaging of the Ventersdorp Contact Reef gold‐bearing horizon (termed reef), a world‐class gold deposit (2 m thick) situated at depths between ∼2400 and ∼4100 m below the ground surface near South Deep Gold Mine in Fochville, South Africa. The final processing results from the pre‐stack time and phase‐shift migration approaches clearly reveal a dipping reflection associated with the gold‐bearing horizon and major steeply dipping faults that crosscut and displace the deposit. The final results are integrated with borehole information, 1D synthetic modelling and aeromagnetic data to constrain the structural interpretation. In particular, 1D synthetic simulation and borehole data constrain the depth position of the gold deposit. The magnetic data provides additional constraints on the complex faulted blocks of the host rocks such as the intrusions that may have a direct impact on ore resources and evaluation. The mining companies, such as South Deep Gold Mine, operating closer to the seismic profiles can use this new structural information to update the current geological models and improve future mine planning and designs, thus providing some insight into the prospectivity of unmined ground.

Hydrochemical characterization and health risk assessment of shallow groundwater in a northern coalfield of Anhui Province, China

In a global context, the hydrochemical characteristics of shallow groundwater in coalfields exhibit high degrees of diversity and complexity that are rooted in the intricate interplay of geological variations, diverse climatic conditions, and extensive human activities. The specific types and concentrations of ions, such as Ca2+, Cl−, and NO3−, show stark differences across geographical regions. Given the crucial roles of coalfields as energy suppliers, the potential environmental contamination risks posed by mining activities to groundwater cannot be overlooked as such pollution directly impacts human health and ecological safety. This study focuses on the Huainan coal mining area in northern Anhui Province (China), where shallow groundwater samples were systematically collected and analyzed to determine the hydrochemical characteristics and ascertain the water quality status. By integrating hydrogeochemical analysis techniques with inverse modeling methods, it was revealed that the groundwater in this region is predominantly HCO3-Ca type, exhibiting weak alkaline characteristics. The formation mechanisms are primarily governed by silicate rock weathering and mineral dissolution–precipitation processes, albeit with discernible influences from human activities. PHREEQC simulations were used to further confirm the precipitation tendencies of minerals like calcite, dolomite, and fluorite as well as the significant dissolution characteristics of halite. The inverse modeling pathway analysis reveals specific hydrochemical processes along different paths: paths I and IV are notably dominated by Ca2+ dissolution–precipitation and cation exchange–adsorption processes, whereas paths II and III are closely associated with the precipitation of calcium montmorillonite as well as dissolution of kaolinite, calcite, quartz, and mineral incongruents. Moreover, evaluations based on the entropy-weighted water quality index (EWQI) indicated overall positive trends of the groundwater quality indicators within the Huainan mining area, reflecting the effectiveness of regional water quality management efforts and providing a scientific basis for future water quality protection and improvement strategies. In summary, this study not only deepens our understanding of the groundwater chemistry in the Huainan coal mining area but also underscores the importance of scientifically assessing and managing groundwater resources to address the environmental challenges potentially arising from coal mining activities.