Search Results (155)

Acid mine drainage, a consequence of exposure of sulfide mining waste to weathering processes, results in significant water, sediment, and soil contamination. This contamination results in acidophilic ecosystems, with low pH values and elevated concentrations of sulfate and potentially toxic elements. The São Domingos mine, an abandoned site in the Iberian Pyrite Belt, lacks remediation measures and has numerous waste dumps, which are a major source of contamination to local water systems. Therefore, this study examines sediment accumulation in five mine dams along the São Domingos stream that traverses the entire mine complex. Decades of sediment and waste transport since mine closure have resulted in dam-clogging processes. The geochemical, mineralogical, and magnetic properties of the sediments were analyzed to evaluate the mineralogical controls on the mobilization of potentially toxic elements. The sediments are dominated by iron oxides, oxyhydroxides, and hydroxysulfates, with jarosite playing a key role in binding high concentrations of iron and toxic elements. However, no considerable correlation was found between potentially toxic elements and magnetic parameters, highlighting the complex behavior of these contaminants in acid mine drainage-affected systems. Full article

To investigate the remediation efficiency of different plant species on cadmium (Cd)-contaminated soil, this study conducted a pot experiment with two woody species (Populu adenopoda and Salix babylonica) and two herbaceous species (Artemisia argyi and Amaranthus hypochondriacus). Soils were collected from an abandoned coal mine and adjacent pristine natural areas within the dam-adjacent section of the Three Gorges Reservoir Area to establish three soil treatment groups: unpolluted soil (T1, 0.18 mg·kg⁻¹ Cd), a 1:1 mixture of contaminated and unpolluted soil (T2, 0.35 mg·kg⁻¹ Cd), and contaminated coal mine soil (T3, 0.54 mg·kg⁻¹ Cd). This study aimed to investigate the growth status of plants, Cd accumulation and translocation characteristics, and the relationship between them and soil environmental factors. Woody plants exhibited significant advantages in aboveground biomass accumulation. Under T3 treatment, the Cd extraction amount of S. babylonica (224.93 mg) increased by about 36 times compared to T1, and the extraction efficiency (6.42%) was significantly higher than other species. Among the herbaceous species, A. argyi showed the maximum Cd extraction amount (66.26 mg) and extraction efficiency (3.11%) during T2 treatment. While A. hypochondriacus exhibited a trend of increasing extraction amount but decreasing extraction efficiency with increasing concentration. With the exception of S. babylonica under T1 treatment (BCF = 0.78), the bioconcentration factor was greater than 1 in both woody (BCF = 1.39–6.42) and herbaceous species (BCF = 1.39–3.11). However, herbaceous plants demonstrated significantly higher translocation factors (TF = 1.58–3.43) compared to woody species (TF = 0.31–0.87). There was a significant negative correlation between aboveground phosphorus (P) content and root Cd (p < 0.05), while underground nitrogen (N) content was positively correlated to aboveground Cd content (p < 0.05). Soil total N and available P were significantly positively correlated with plant Cd absorption, whereas total potassium (K) showed a negative correlation. This study demonstrated that woody plants can achieve long-term remediation through biomass advantages, while herbaceous plants, with their high transfer efficiency, are suitable for short-term rotation. In the future, it is suggested to conduct a mixed planting model of woody and herbaceous plants to remediate Cd-contaminated soils in the tailing areas of reservoir areas. This would synergistically leverage the dual advantages of root retention and aboveground removal, enhancing remediation efficiency. Concurrent optimization of soil nutrient management would further improve the Cd remediation efficiency of plants. Full article

Active and abandoned mining sites are significant sources of heavy metals and metalloid pollution, leading to serious environmental issues. This study assessed the environmental risks posed by potentially toxic elements (PTEs), specifically arsenic (As) and antimony (Sb), in the Technosols (mining residues) of the former Pejão coal mine complex in Northern Portugal, a site impacted by forest wildfires in October 2017 that triggered underground combustion within the waste heaps. Our methodology involved determining the “pseudo-total” concentrations of As and Sb in the collected heap samples using microwave digestion with aqua regia (ISO 12914), followed by analysis using hydride generation-atomic absorption spectroscopy (HG-AAS). The concentrations of As an Sb ranging from 31.0 to 68.6 mg kg⁻¹ and 4.8 to 8.3 mg kg⁻¹, respectively, were found to be above the European background values reported in project FOREGS (11.6 mg kg⁻¹ for As and 1.04 mg kg⁻¹ for Sb) and Portuguese Environment Agency (APA) reference values for agricultural soils (11 mg kg⁻¹ for As and 7.5 mg kg⁻¹ for Sb), indicating significant enrichment of these PTEs. Based on average I_geo values, As contamination overall was classified as “unpolluted to moderately polluted” while Sb contamination was classified as “moderately polluted” in the waste pile samples and “unpolluted to moderately polluted” in the downhill soil samples. However, total PTE content alone is insufficient for a comprehensive environmental risk assessment. Therefore, further studies on As and Sb fractionation and speciation were conducted using the Shiowatana sequential extraction procedure (SEP). The results showed that As and Sb levels in the more mobile fractions were not significant. This suggests that the enrichment in the burned (BCW) and unburned (UCW) coal waste areas of the mine is likely due to the stockpiling of lithic fragments, primarily coals hosting arsenian pyrites and stibnite which largely traps these elements within its crystalline structure. The observed enrichment in downhill soils (DS) is attributed to mechanical weathering, rock fragment erosion, and transport processes. Given the strong association of these elements with solid phases, the risk of leaching into surface waters and aquifers is considered low. This work underscores the importance of a holistic approach to environmental risk assessment at former mining sites, contributing to the development of sustainable remediation strategies for long-term environmental protection. Full article

Abandoned pits and quarries in Ontario, Canada, are on the rise due to industrialization, leading to ecosystem disruption and soil contamination with pollutants such as cadmium, cobalt, nickel, and barium, which may leach into nearby water systems. Current rehabilitation processes are slow to initiate, and therefore, the site remains in a contaminated condition for years. Phytoremediation, which involves using plants to remove contaminants from soils, is receiving increased attention for cleaning up decommissioned mines. This type of rehabilitation is normally practiced in situ by hand-planted and managed vegetation chosen for the specific purpose of contaminant removal. This study investigated the phytoremediation potential of indigenous plants as local seed sources to rehabilitate decommissioned quarries in Ontario. This study also investigated the potential of native plants to naturalize in the disturbed areas, thus providing a natural clean-up of the contaminants. Thus, if successful, this process will also initiate the re-establishment of native wildlife in the area. Through a literature review, 74 plant species were identified as capable of remediating 20 contaminants often found on the decommissioned quarry sites. The results may help ecosystem managers to adopt environmentally sustainable strategies to clean up contaminated sites such as decommissioned mines and quarry areas. Full article

The Iberian Pyrite Belt (IPB) contains the world’s largest massive sulfide deposit, and, due to extensive mining developed during the last 200 years, large amounts of mining waste have been abandoned in this area, with roasted pyrite ash being the focus of this study. Polymetallic mining is also classified as a NORM (naturally occurring radioactive material) activity, thus the main objective of this work was to develop a radiological and physicochemical characterization of this waste (mineral phases, elemental and radionuclide concentrations) in order to perform a valorization diagnosis of this material. The composition of this waste strongly depends on its origin (mine), and is mainly formed by iron oxides (hematite, Fe₂O₃) and heavy metals and metalloids such as As, Pb, Zn, and Cu, in levels 2–4 orders of magnitude higher than those of undisturbed soils, depending on each particular element. However, the average natural radionuclide levels are similar to those of unperturbed soils (around 30 Bqkg⁻¹ of ²³⁸U-series, 50 Bqkg⁻¹ of ²³²Th, and 70 Bqkg⁻¹ for ⁴⁰K), thus they are below the limits established by European Union regulations to require radiological control during their future valorization. As the main potential applications of roasted pyrite ash, the valorization diagnosis indicates that it can be used as a source of Fe (FeCl₃ or FeSO₄), or an additive in the manufacturing of cements, pigments, etc. Full article

Mining activities and associated waste materials pose significant environmental challenges, including soil, water, and air contamination, along with health risks to nearby populations. Despite the harsh conditions of metal-enriched soils and nutrient-poor substrates, certain plants known as metallophytes thrive in these environments. This study examined the vascular flora of Sardinia’s abandoned mining sites, with a focus on identifying metallophytes and their potential role in phytoremediation. A comprehensive floristic checklist was compiled using literature, field surveys, and herbarium samples. Of the 652 taxa identified, 49% were metallophytes, with the majority categorized as facultative species. Notably, 27% of metallophytes were identified as suitable for phytostabilization, while 20% showed potential for phytoextraction. This study also highlighted the presence of endemic and endangered species, emphasizing the need for conservation efforts. The findings suggest that native metallophytes could play a key role in the ecological restoration of mining sites, though careful consideration of invasive species is necessary to avoid ecological disruption. This research provides valuable insights into the biodiversity of Sardinian mining sites and the potential for sustainable remediation strategies using native plants. Full article

Microbial inoculants are vital for promoting plant growth and facilitating the ecological restoration of degraded forested regions near abandoned mine sites. However, the direct application of liquid microbial inoculants is often challenging due to low microbial activities and poor transport efficiencies, which limit their effectiveness in complex soil environments. To tackle these challenges, this study utilized immobilized microbial technology to evaluate the effectiveness of solid microbial inoculants sourced from peat (P), biochar (BC), and spent mushroom substrates (SMSs) in enhancing the soil’s multifunctionality and promoting plant growth. Specifically, this research sought to assess the effectiveness of solid microbial inoculants derived from peat (P), biochar (B), and spent mushroom substrates (SMSs) in enhancing soil multifunctionality and promoting plant growth in nutrient-deficient soils that were affected by abandoned mine sites. We aimed to evaluate the performance of different solid microbial inoculants in improving the soil’s nutrient content and enzyme activities. A 24-week pot experiment was conducted using Medicago sativa L. in nutrient-poor soil. The results demonstrated that, in contrast to peat and biochar, SMSs effectively interacted with microbial inoculants and significantly improved the nutrient content and enzyme activities of nutrient-deficient soil. It was noted that β-1,4-glucosidase (BG), invertase, β-1,4-N-acetylglucosaminidase (NAG), urease, and soil available phosphorus increased by 204%, 405%, 118%, 198%, and 297%, respectively. The soil’s multifunctionality improved by 320% compared with the CK, and the plant biomass also increased significantly. Further, our random forest analysis indicated that the soil available phosphorus, ammonium nitrogen, total nitrogen, total carbon content, arylsulfatase, pH, total phosphorus, NAG, and BG were key environmental factors that induced changes in plant biomass. These findings highlighted the potential of SMSs as an effective carrier for immobilized microbial inoculants, which provides a sustainable approach for the restoration of forest soils surrounding abandoned mine sites, as well as a promising avenue for the valorization of agricultural waste. Full article

Coal gangue dumps, a byproduct of coal mining, contribute significantly to heavy metal contamination, impacting soil and water quality. In order to assess the levels of heavy metal contamination in soils at different stages of abandonment, this study investigated the role of Miscanthus floridulus (M. floridulus) in the spatial distribution and remediation of six heavy metals (Cd, Cr, Mn, Ni, Cu, and Pb) in coal gangue dump soils abandoned for 0, 8, and 12 years in Pingxiang City, Jiangxi Province, China. Fieldwork was conducted at three sites operated by the Pingxiang Mining Group: Anyuan (active, barren), Gaokeng (8 years, natural vegetation), and Qingshan (12 years, partially remediated). Anyuan remains largely barren, while Gaokeng supports natural vegetation without formal remediation. In contrast, Qingshan supports diverse plant species, including M. floridulus, due to partial remediation. Using a randomized design, root exudates, heavy metal concentrations, and soil properties were analyzed. The results showed that Cd poses the highest ecological risk, with concentrations of 64.56 mg kg⁻¹ at the active site, 25.57 mg kg⁻¹ at the 8-year site, and 39.13 mg kg⁻¹ at the 12-year site. Cu and Pb showed accumulation, while Cr and Mn decreased over time. Root exudates from M. floridulus enhanced metal bioavailability, influencing Cd, Cr, and Ni concentrations. These findings highlight the importance of rhizosphere processes in metal mobility and inform sustainable remediation strategies for post-mining landscapes. Full article

Phytoremediation represents a potentially effective and environmentally friendly technology to remediate arsenic (As) in mine waste soils. However, soil amendments are often required to improve phytoremediation due to depleted nutrients in mine waste. This study aims to assess the effect of biosolids biochar, applied at different rates (0%, 5%, and 10%) on As phytoremediation using three plant species: Poa labillardieri, Rytidosperma caespitosum, and Juncus pauciflorus. This study was conducted in a replicated greenhouse pot study using soil from an abandoned mine site. Dry plant biomass, As concentration in plants and soil, and soil microbial abundance were investigated. Juncus pauciflorus produced eight times more root and shoot biomass than R. caespitosum in soils amended with 10% biochar. The highest As uptake was also observed in J. pauciflorus grown in soils amended with 10% biochar (7.10 mg/plant), while R. caespitosum had the lowest As uptake in soils without biochar (0.16 mg/plant). In soils amended with 10% biochar, the total bacterial community decreased to approximately 8.50 log₁₀ copies/g, compared to the initial soil (9.05 log₁₀ copies/g), while the number of gene copies of the nifH gene increased, suggesting the importance of nitrogen-fixing bacteria to promote plant growth. Taguchi analysis confirmed that plant species was the key factor for As phytoremediation, followed by biochar application dose. This study showed that J. pauciflorus and the addition of 10% biochar was the best treatment for remediating As-contaminated mine waste, offering the potential for use commercially. Moreover, the utilisation of biochar derived from biosolids as a soil amendment for enhancing phytoremediation represents good circular economy practice to manage excessive biosolids production. Full article

Acid mine drainage (AMD), which is primarily caused by the exposure of sulfidic minerals to oxygen and water during mining operations, remains a significant contributor to environmental pollution. Numerous technologies have been developed to prevent/control and treat AMD, including the isolation of waste from the atmosphere and treatment systems for AMD-impacted water. Many field studies on mine site reclamation have involved an individual AMD source and/or technology, with a limited number of studies looking at reclamation programs integrating multiple approaches to manage AMD stemming from both surface and underground sources. The former Franklin mine site in Nova Scotia, Canada, was impacted by the deposition of waste rock across the site and the discharge of mine water from underground workings, with the adjacent Sullivan’s Pond serving as the main environmental receptor. Site reclamation was completed in 2010 and involved the following: (1) excavation of the dispersed waste rock (117,000 m²) and backfilling with clean soil; (2) consolidation of the excavated waste rock into a covered, compact waste rock pile (WRP) (25,000 m²); and (3) construction of a passive treatment system for the discharging underground mine water. An extensive field sampling program was conducted between 2011 and 2018 to monitor a range of meteorological, cover material, waste rock, groundwater, and surface water quality parameters. The results confirm that the multi-layer, geomembrane-lined WRP cover system is an extremely effective barrier to air and water influx, thereby minimizing the rate of AMD generation and seepage into groundwater and eliminating all contaminated surface water runoff. A small AMD groundwater plume emanates from the base of the WRP, with 50% captured by the underground mine workings over the long term and 50% slowly migrating towards Sullivan’s Pond. Excavation of the former waste disposal area eliminated the AMD source from the previously dispersed waste, with only clean surface water runoff and a diminishing legacy groundwater plume remaining. Finally, the passive treatment system, which contains a series of treatment technologies such as a limestone leach bed and settling pond, successfully treats all mine water loading (~50 kg/day) discharging from the underground workings and surface runoff. Its additional treatment capacity (up to ~150 kg/day) ensures it will be able to manage any potential drop in treatment efficiency and/or increased AMD loading from long-term WRP seepage. This comprehensive study of mine site reclamation and AMD management at an abandoned mining site can be of great reference value for environmental management and policymakers in the mining sector. Full article

In Slovakia, there are a number of contaminated sites that have occurred due to intensive mining, mineral processing, metallurgical activities, chemical industry, fossil fuel combustion, and industrial agriculture in the past. This paper summarizes the occurrence, chemistry, toxicity, and mineralogy of arsenic species related to soil and water contamination in Slovakia. Four main localities with arsenic exposure were identified. Additionally, magnetically modified carbon biochar (MWchar-Mag) was tested for arsenic removal from a model solution alongside real mine water discharged from the abandoned Hauser adit. For the model aqueous solution, the maximum adsorption capacity was established at 6.2 mg of As per g of MWchar-Mag at natural pH. In the case of mine water with a concentration of arsenic at around 0.2 mg/L, adsorbent dosage, pH influence experiments, and kinetic tests were realized. The results confirmed 100% arsenic removal efficiency at pH~3–7 and extremely fast kinetics. Full article

Mining activities in arid regions of China have led to severe environmental degradation, including soil erosion, vegetation loss, and contamination of soil and water resources. These impacts are particularly pronounced in abandoned mining areas, where the cessation of mining operations has left vast landscapes unrehabilitated. In response, the Chinese government has implemented a series of legal and regulatory frameworks, such as the “Mine Environmental Protection and Restoration Program”, aimed at promoting ecological restoration in these areas. However, the unique environmental conditions of arid regions, including water scarcity, extreme temperatures, and poor soil quality, present significant challenges to restoration efforts. This review provides a comprehensive analysis of the ecological restoration of abandoned mining areas in China’s arid regions, focusing on the legal framework, restoration techniques, and evaluation systems. The restoration methods, their initiation timelines, monitoring systems, and the cost–benefit aspects of various strategies are critically reviewed alongside case studies from regions such as the Mu Us Desert and Qaidam Basin. Key strategies like phytoremediation, soil rehabilitation, and water resource management are assessed for their effectiveness, while challenges in enforcement, socioeconomic integration, and community engagement are discussed. This review concludes that while significant progress has been made, further improvements in restoration practices and evaluation systems are essential for long-term sustainability. Integration of socioeconomic indicators, community involvement, and advanced monitoring technologies are necessary for successful outcomes. Full article

Small abandoned mining areas of Fe and Mn oxides located in the Portuguese sector of the Iberian Pyrite Belt (SW of Europe) have been converted into agrosilvopastoral systems with very few environmental management measures after their closure. Although at the landscape scale, no visible differences were observed between the former mining intervention areas and adjacent areas, it is essential to assess the state and environmental risk of the soil–plant system, especially in the herbaceous pastures grazed by domestic animals. This was carried out in the Ferragudo mining area, where an agrosilvopastoral system, composed of holm oak and dryland pasture, had been established after the closure of the mine at ≈45 years. The soils presented neutral pH and variable fertility degree. The pseudo-total soil concentrations of Cu, Mo, and Zn exceeded the Portuguese limit values established for agriculture use (>180 mg Cu/kg; >8.2 mg Mo/kg; 349 mg Zn/kg), but their soil available fractions were small (<8.4% of the pseudo-total concentrations). Trees and herbaceous plants showed good development, and the concentrations of the elements (except Mn) were considered normal or sufficient. For Mn, most of the plant samples exceeded phytotoxic Mn values, but no visual signs of phytotoxicity were observed. Only the concentrations of Fe and K in the shoots of some herbaceous samples exceeded the maximum tolerable levels for cattle and sheep, so the risk to animals can be considered small since other sources are present in animal feed. In general, this agrosilvopastoral system did not pose a significant environmental risk. Full article

Ecological restoration of abandoned mining areas in arid regions presents significant challenges, especially in terms of soil salinization, vegetation loss, and limited water resources. In the Hami arid area of Xinjiang, vegetation restoration is crucial for stabilizing ecosystems and combating land degradation. This study investigated the effects of two irrigation methods—drip and border irrigation—on the growth and survival of four plant species: Tamarix chinensis, Calligonum mongolicum, Haloxylon ammodendron, and Phragmites australis, each exposed to salinity levels of 8 g/L, 12 g/L, and 16 g/L. Our results showed that drip irrigation significantly improved the growth and survival outcomes for most species, particularly T. chinensis and H. ammodendron, with average heights, crown sizes, and base diameters substantially higher under drip irrigation compared to border irrigation (p < 0.05). C. mongolicum, however, displayed optimal vertical growth under border irrigation, although drip irrigation promoted a denser, more compact crown structure. Salinity tolerance varied by species, with 8 g/L salinity being optimal for all, while higher salinity levels (12 g/L and 16 g/L) reduced growth across species, underscoring the importance of salinity management in restoration efforts. P. australis, assessed only under border irrigation due to its high water requirements, showed stable growth but reduced tolerance at higher salinities. These findings highlight that drip irrigation, particularly when combined with moderate salinity (8 g/L), is a more effective strategy for enhancing vegetation growth and survival in arid, saline environments. Our study provides practical recommendations for irrigation and salinity management in ecological restoration, offering insights for improving vegetation resilience in arid mining landscapes. Full article

Mining activities lead to significant environmental degradation, including soil erosion, water pollution, and biodiversity loss. In South Korea, abandoned coal mines cause considerable ecological disturbances in mountainous regions. Forest rehabilitation has been proposed as a strategy to mitigate these impacts, but its effectiveness depends on successfully integrating ecosystem services (ES). This study assesses the social value of ES in post-mining rehabilitation by incorporating perspectives from local communities and experts in forestry and mining sectors. A mixed-methods approach involving surveys and interviews was employed to gather stakeholder views on 18 ES, including provisioning, regulating, cultural, and habitat services. Results indicate that local communities prioritize cultural and regulating services, such as mental health, aesthetic value, and climate regulation, while experts emphasize regulating services like soil erosion control and carbon sequestration. This divergence highlights the need for a balanced approach that integrates both ecological and socio-cultural benefits, suggesting that community needs have not been adequately reflected in current practices. The study findings underscore the importance of incorporating community input into forest management to ensure both ecological outcomes and social value, offering a framework for adaptive management that aligns ecological goals with community needs, ultimately promoting sustainability and resilience in post-mining landscapes. Full article