Search Results (645)

Accurate identification of acid-producing layers is key to controlling acid mine drainage (AMD) in abandoned coal mines. This study collected 337 core samples from 34 boreholes in the Modigou mining area, Shanxi, China, and established a combined static–mineralogical–kinetic approach to evaluate the acid-generating and neutralization potentials of sulfur-bearing rocks. Three-stage net acid generation (NAG) tests identified the pyrite-bearing layer of the Benxi Formation and the No. 10 coal seam of the Taiyuan Formation as the main acid producers, with NAG values of 360.41 and 97.87 kg H₂SO₄/t, respectively, while the Taiyuan limestone showed a high neutralization capacity (ANC = 490 kg H₂SO₄/t). NAG pH was strongly negatively correlated with sulfur content (Pearson r = −0.75, p < 0.01). Sulfide oxidation acid production showed staged attenuation, with average decreases of 64.81% and 47.65% in the second and third stages. Humidity cell experiments demonstrated continuous acid production over 63 days under dry–wet cycles, with increased acid generation rates at higher flow velocities (Darcy flux: 3.54 × 10⁻³ cm/s for accelerated vs. 8.84 × 10⁻⁴ cm/s for standard conditions). Multi-dimensional flow-through simulations confirmed the AMD formation mechanism of “acid supply, buffer, and fracture conduction”. The identified acid-producing layers matched well with field discharge points. This multi-method coupling system provides a theoretical basis for source control of AMD in abandoned high-sulfur coal mines in the Yellow River Basin. This study did not account for microbial catalysis, which is a key limitation of the static chemical oxidation method used. Full article

Acid mine drainage (AMD) pollution from closed coal mines in karst regions represents a major environmental challenge in the global mining industry. The complexity of hydrogeological conditions in such regions leads to significant challenges in both predictability and controllability of pollution. Taking the Yudong River Basin in Guizhou Province, Southwest China, as the study area, and based on six years (2017–2023) of systematic remediation practices and monitoring data, this study systematically evaluates the effectiveness and applicable conditions of three types of treatment technologies: centralized treatment stations, source control combined with end-of-pipe treatment, and water-sealing ecological plugging. On this basis, governance models applicable to karst regions are distilled. The results show that after six years of remediation, the number of pollution points in the Yudong River Basin decreased from 27 to 12. At the outflow section, the total Fe reduction rate reached 88.3%, the total Mn reduction rate reached 62.3%, and the proportion of contaminated river length was reduced by 78.5%. Each of the three technologies has its own applicable conditions. Centralized treatment stations, characterized by mature technology but high operational costs, are suitable for emergency transition periods. Source control combined with end-of-pipe treatment addresses both symptoms and root causes, making it applicable to complex pollution points. Water-sealing ecological plugging, although cost-controllable, carries a risk of secondary pollution in karst-developed areas. The failure of water-sealing ecological plugging technology is mainly attributed to two mechanisms: bypass flow through karst conduits and overflow induced by water level rise. Based on the six-year remediation practice, this study proposes a source control model for karst conduits centered on the core concepts of “filling, isolating, plugging, intercepting, draining, and controlling”. The implementation process consists of four stages: detailed investigation, graded optimization, stepwise implementation, and long-term monitoring. The core innovation lies in the cross-disciplinary application of coal mine water control techniques to environmental remediation, achieving a shift from passive end-of-pipe treatment to active source control. This model can provide theoretical reference and practical guidance for karst mining areas in Southwest China and other regions with similar geological conditions. Full article

Acid mine drainage (AMD) is enriched with arsenite (As(III)), arsenate (As(V)), and jarosite. While jarosite can immobilize arsenic (As) through adsorption and other mechanisms, it dissolves and transforms into other minerals under near-neutral and reducing conditions via microbial mediation, thereby altering As fate. Fulvic acid (FA), a ubiquitous natural organic matter in the environment, has been proven to exhibit complex interactions with various iron minerals, Fe/S-metabolizing microorganisms, and As. However, the role of FA in the bioreduction and transformation of jarosite, as well as its subsequent impact on As mobility and fate, remains unclear. This study aims to elucidate the regulatory effect of FA on the biodissolution and transformation of jarosite, and the corresponding changes in As speciation. The results showed that FA exerted contrasting effects depending on arsenic speciation. In the As(III) treatments, FA intensified the inhibition of microbial dissimilatory sulfate reduction, suppressed sulfide production, and consequently limited orpiment formation. In contrast, in the As(V) treatments, FA enhanced the association of As(V) with jarosite surfaces, reduced aqueous As stress, and supported the persistence of As-tolerant sulfate-reducing populations. This promoted jarosite transformation toward mackinawite and facilitated As immobilization through orpiment precipitation. This study reveals the critical role of FA in the migration and transformation of As in mining areas, providing novel insights for optimizing AMD remediation strategies such as soil capping. Full article

Mining activities in the Iberian Pyrite Belt have generated large volumes of legacy wastes that may pose both environmental and radiological concerns, potentially limiting their reuse and valorization. However, integrated assessments combining chemical, mineralogical, and radiological characterization of these materials remain scarce. In this work, representative mining wastes from twelve sites across the Iberian Pyrite Belt were investigated through X-ray fluorescence, X-ray diffraction, scanning electron microscopy, standardized leaching tests, alpha and gamma spectrometry, and radon emanation measurements. The results revealed significant enrichment in potentially toxic elements, particularly Cu, Zn, Pb, and As, with concentrations exceeding local soil background values by up to several orders of magnitude. Leaching tests identified oxidized sulfide-rich residues as the materials with the highest pollutant mobility and greatest acid-generating potential. In contrast, radiological characterization showed that uranium-series, thorium-series radionuclides, and ⁴⁰K activities, together with radiological hazard indices and radon exhalation rates, were generally comparable to those of surrounding natural soils and remained below internationally recommended limits. These findings indicate that chemical contamination represents the main environmental constraint of these wastes, whereas radiological impact is generally low, supporting their case-by-case evaluation for remediation, valorization, and potential exclusion from radiological control. Full article

The environmental impacts of treated acid mine drainage on receiving river systems remain insufficiently understood. This study investigated four typical closed coal mines in northern Sichuan Province, China, by analyzing heavy metals, sulfate, pH, UV-Vis spectroscopy, and dissolved organic matter (DOM) characteristics at 24 sampling sites along the receiving reaches. Parallel factor analysis (PARAFAC) and two-dimensional correlation spectroscopy (2D-COS) were employed to examine the longitudinal response sequence of DOM components. Results showed that pollutant concentrations generally increased immediately after the inflow of treated acid mine drainage and then progressively attenuated downstream, although the dominant pollution factors varied significantly among the reaches. DOM composition exhibited spatial heterogeneity, with protein-like components dominating three reaches and humic-like components prevailing in one reach. Based on the co-variation characteristics of DOM and heavy metals along the river course, four response patterns were identified: rapid-recovery, slow-recovery, disturbance–oscillation recovery, and delayed-recovery patterns. The 2D-COS analysis validated the rationality of these four patterns and revealed differences in the sensitivity of various DOM components to longitudinal disturbances. This study provides a scientific basis for the environmental impact assessment of mine water from remediated closed coal mines. Full article

This study evaluates the characteristics and environmental behavior of river sediments impacted by coal mining in the southern coal region of Santa Catarina, Brazil. Sediments accumulated in mining-affected rivers represent an environmental liability due to the presence of potentially toxic elements and their limited management options. In this context, ceramization is investigated as an alternative strategy for reducing contaminant mobility through thermal treatment of sediments collected at four sampling points (PU1–PU4) along the Urussanga River. Initially, leaching and solubilization tests were performed to assess the mobility of chemical elements, and the raw sediments were further characterized by chemical, mineralogical, and thermal analyses. Subsequently, ceramic specimens were produced from the sediments and subjected to thermal treatment at 1100 °C. After firing, the specimens were re-evaluated through leaching and solubilization assays to verify changes in contaminant mobility after the ceramization process. The results showed that raw sediments exhibited aluminum, iron, and manganese concentrations in the solubilized extract that exceeded regulatory thresholds, particularly for iron, which reached up to 21.91 mg/L. After thermal treatment, a substantial reduction in the solubility of these elements was observed, with concentrations falling below the established limits at all sampling points. This reduction in mobility is likely associated with physicochemical transformations occurring during firing, including matrix densification and the incorporation of elements into less soluble phases, as reported in previous ceramic processing studies. Overall, the findings demonstrate that ceramization represents a promising strategy for reducing contaminant mobility in coal mining-impacted river sediments, offering a viable and environmentally friendly alternative for sediment management and valorization. Full article

The successful realization of a circular economy in the cement industry, coupled with a substantial reduction in carbon emissions, relies on the development of sustainable alternative binder systems. This study investigated the physicomechanical performance and sulfate resistance of composites produced by alkali activation of natural perlite and blast furnace slag. The aim of the research was to improve mechanical properties under low- and medium-alkalinity conditions (5–10 M NaOH). The samples were cured at an ambient temperature of 20 °C and then treated with heat at 60 °C. These samples were then mechanically processed and subjected to five soak–dry cycles in 5% and 10% Na₂SO₄ solutions. The results showed that heat treatment resulted in the formation of a dense C-A-S-H gel, increasing compressive strength approximately eightfold, from 11.64 MPa to 92 MPa. However, perlite’s porous and brittle structure limits its flexural strength to 0.27 MPa; this value is insufficient for structural applications. Under severe sulfate attack (10% Na₂SO₄), samples cured at ambient temperature showed a 12% mass increase in the first cycle due to solution infiltration into capillary voids. As a consequence of extensive ettringite and gypsum formation, the specimens experienced severe deterioration, resulting in a complete loss of mechanical integrity and a residual compressive strength of 0 MPa. In contrast, heat-treated samples showed limited ion diffusion due to a denser matrix and an improved aggregate interface transition zone, resulting in a 2.6% mass increase and a residual compressive strength of 5.17 MPa. Consequently, the obtained findings indicate that thermally treated alkali-activated slag–perlite composites exhibit high resistance against sodium sulfate attack and may have potential for use in specific industrial environments with high sulfate concentrations. However, the performance of these materials under more complex aggressive conditions, such as mining environments involving magnesium sulfate exposure and acidic drainage waters, should be further validated through future studies. Full article

Oil sands tailings from tailings solvent recovery units (TSRU) contain elevated sulfide minerals and can generate acid mine drainage (AMD) upon atmospheric exposure. This study investigated how prior weathering influences acidity and solute release under controlled laboratory conditions. A six-month column leaching experiment was conducted using TSRU tailings with distinct exposure histories: weathered and semi-weathered tailings from a previous greenhouse-scale reclamation capping experiment, along with weakly weathered tailings stored in sealed barrels. Columns were subjected to repeated wet–dry cycles, analyzing the geochemistry of the leachate and solid-phase changes using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). All treatments produced highly acidic leachates (pH < 2), indicating that TSRU tailings retain the capacity to generate acidity regardless of prior exposure. However, the dominant geochemical mechanisms differed by weathering history. Weakly weathered tailings generated progressive increases in acidity and solute release, consistent with active sulfide oxidation. Semi-weathered tailings had more stable responses, suggesting partial sulfide depletion and secondary phase formation. Weathered tailings produced leachates showing evidence of rapid flushing with limited new solute generation. After leaching, residual pyrite remained in all materials, with shifts in surface sulfur speciation providing evidence of progressive surface sulfur oxidation, transformation, and the redistribution of sulfate phases. These results demonstrate the mechanisms involved in AMD generation in TSRU tailings, highlighting the importance of the weathering history and the need for field-scale validation. Full article

Phenolics in Sphagnum can inhibit its microbial decomposition. Climate warming and drainage have driven vascular plants, such as Ericaceae, to expand into Sphagnum-dominated peatland. However, the impact of fine root invasion by Rhododendron auriculatum Hemsl. on Sphagnum decomposition and changes in phenolic compounds remains unclear. This study compared Sphagnum decomposition in a Sphagnum palustre L.-dominated peatland and an R. auriculatum (Sapling)–S. palustre peatland by examining the microscopic structure of S. palustre and microbial community composition. Decomposition was higher in the R. auriculatum–S. palustre peatland. On this site, bacterial metabolic types such as aerobic chemoheterotrophy and chemoheterotrophy had higher relative abundances, as did fungal trophic modes, including those with combined ectomycorrhizal, ericoid mycorrhizal, and saprotrophic functions. Acid phosphatase, laccase, total nitrogen (TN), C/N ratio (C:N), and pH differed significantly across decomposition stages. Microbial communities are affected by physicochemical factors and enzyme activities. Untargeted metabolomics revealed more downregulated than upregulated phenolics, cinnamic acids, and tannins, indicating loss of phenolic compounds. In summary, R. auriculatum fine root invasion altered enzyme activities and physicochemical properties, driving the restructuring of bacterial and fungal trophic modes and accelerating S. palustre cell wall and hyaline cell decomposition. Full article

Biliary atresia (BA) is a progressive fibroinflammatory cholangiopathy of infancy that rapidly advances to cholestasis, fibrosis, cirrhosis, and liver failure if bile drainage is not restored early. Although Kasai hepatoportoenterostomy (KPE) remains the standard first–line operation, many children still develop recurrent cholangitis, persistent cholestasis, and progressive native liver injury. Increasing evidence indicates that the gut microbiota participates in this clinical course through the gut–liver axis. In BA, dysbiosis may weaken the intestinal barrier, increase translocation of microbe–associated molecular patterns (MAMPs), amplify innate and adaptive immune activation, disturb bile acid signaling, and promote fibrogenic and ferroptosis–related injury. In contrast, beneficial taxa and their metabolites may preserve epithelial integrity, support immune tolerance, maintain bile acid homeostasis, and constrain oxidative stress. This review summarizes current evidence on these contrasting harmful and protective effects, stage–specific microbiome signatures reported before and after KPE, and critically evaluates the present status of microbiota–based biomarkers and interventions. We emphasize that although several microbial signatures and therapeutic approaches are promising, they are not yet ready for routine clinical implementation and require prospective validation with standardized endpoints. Full article

Acid mine drainage is an important source of heavy metal contamination in mining watersheds, posing persistent risks to aquatic environments and sediment quality. This study evaluated heavy metal pollution in water and sediments of the acid mine drainage-impacted Xiaomi Creek watershed, China. A total of 20 water samples and 13 sediment samples were collected and analyzed for manganese (Mn), lead (Pb), copper (Cu), cadmium (Cd), aluminum (Al), nickel (Ni), iron (Fe), and zinc (Zn). Water pollution was assessed using the single-factor exceedance index and the Nemerow composite pollution index, whereas sediment contamination was evaluated using the geoaccumulation index and potential ecological risk index. The results showed that water in the Xiaomi Creek watershed spanned a broad pH range (3.16–8.05), and heavy metal pollution was generally more severe in the main channel than in the tributaries, indicating a clear influence of upstream pollution inputs. Nickel showed the strongest enrichment in sediments and posed the highest ecological risk among the investigated metals, while Mn, Pb, Zn, and Ni exhibited severe sediment contamination. Overall, upstream stone coal mining activities and associated waste piles were likely major contributors to heavy metal pollution in the watershed, highlighting the need for source control, sediment-associated risk management, and risk-prioritized monitoring to support sustainable watershed management. Full article

Background/Objectives: Managing postoperative drainage and reducing the length of hospital stays continue to represent significant challenges in thoracic surgery. While systemic antifibrinolytics are effective, concerns persist regarding neurotoxicity and thromboembolic risks. In this study, we evaluated the efficacy and safety of a unique, high-volume topical tranexamic acid (t-TXA) lavage protocol designed to optimize pleuroparenchymal contact and stabilize local hyperfibrinolysis. Methods: A retrospective comparative study was conducted involving 52 patients undergoing major lung resection, divided into a t-TXA group (n = 26) and a control group (n = 26). The t-TXA group received an intrathoracic lavage consisting of 5 g of tranexamic acid (TXA) diluted in 500 mL of saline, while the control group received 500 mL of saline alone. The primary outcomes included postoperative day (POD) 1 drainage volumes and length of stay (LOS). The secondary outcomes were focused on hematological parameters and safety profiles, including a structured one-year follow-up for all patients. Due to the study’s exploratory nature, primary outcomes were assessed using 95% confidence intervals for hypothesis generation rather than a priori sample size calculations. Results: No significant differences were observed between groups regarding sex, surgical approach, or resection type. The t-TXA group demonstrated a significantly shorter LOS (4.20 ± 1.23 days) compared to the control group (5.88 ± 2.23 days; p = 0.001). While POD 1 drainage was numerically lower in the t-TXA group (189.23 ± 235.06 mL) versus the control (284.23 ± 169.40 mL), this difference did not reach statistical significance (p = 0.101). However, exploratory correlation analysis revealed a moderate negative association between t-TXA application and POD 1 drainage (r = −0.412; p = 0.002). Postoperative platelet counts were significantly lower in the t-TXA group (p = 0.009). No thromboembolic events, late complications, or deaths occurred in either group during the one-year follow-up period. Conclusions: High-volume t-TXA lavage is a promising adjuvant associated with significantly shorter hospital stays and a trend toward reduced postoperative drainage. While our 12-month follow-up confirmed a favorable safety profile with no adverse events, these findings should be interpreted as preliminary and hypothesis-generating. The retrospective nature of this study precludes definitive recommendations, underscoring the need for well-powered prospective randomized trials to establish the long-term safety and clinical utility of t-TXA in thoracic surgery. Full article

Schwertmannite (Sch) is a widespread iron oxyhydroxysulfate mineral in acid mine drainage (AMD) systems, and its transformation strongly influences the environmental fate of chromium (Cr). However, the role of Ca(II), which is commonly introduced during alkaline neutralization of AMD, in regulating the transformation of Cr(VI)-adsorbed schwertmannite (Cr-Sch) and subsequent Cr redistribution remains insufficiently understood. In this study, transformation experiments were conducted under various pH conditions (3.0, 7.0, and 10.0) to investigate the effects of Ca(II) speciation on mineral transformation and Cr behavior. The results demonstrated that the transformation of Cr-Sch was predominantly pH-dependent. Under acidic conditions, Cr-Sch transformed into goethite via dissolution–recrystallization, resulting in transient Cr release followed by partial refixation. The presence of Ca(II) exerted only a minor influence due to weak interactions between Ca²⁺ and positively charged mineral surfaces. Under alkaline conditions, Cr-Sch preferentially transformed into hematite through dehydroxylation and cation rearrangement, leading to the sustained release of adsorbed Cr(VI). In contrast, Ca(II) predominantly precipitated as CaCO₃ precipitate (calcite, aragonite, and vaterite) under alkaline conditions, which coated mineral surfaces and inhibited phase transformation and Cr release. These findings reveal that Ca(II) regulates Cr redistribution primarily through pH-dependent speciation and mineral–surface interactions, highlighting coupled geochemical processes governing iron mineral transformation and contaminant mobility in AMD environments. This study provides mechanistic insights for predicting Cr behavior and optimizing alkaline remediation strategies in mining-impacted systems. Full article

Background: Cervicofacial actinomycosis is an uncommon chronic bacterial infection that can mimic neoplasia or granulomatous disease because of its infiltrative presentation. Diagnosis is often delayed, particularly in pregnant patients in whom imaging and invasive procedures may be limited. Case report: A 25-year-old woman at 14 weeks of gestation presented with a multiple-fistulized cervical mass. The lesion was initially diagnosed as a cutaneous furuncle in a private dermatology practice and treated with topical therapy, resulting in only transient improvement. Two weeks later, multiple fistulizations developed, prompting consultation in the emergency department. ENT assessment and ultrasound raised suspicion of cervical actinomycosis versus fistulized tuberculous lymphadenitis. Considering the pregnancy, drainage of the collection was performed under local anesthesia and empiric antibiotic therapy with amoxicilin-clavulanic acid was started. Microbiological confirmation of Actinomyces (Schaalia) georgiae led to infectious disease evaluation that established a long-term antibiotic therapy while monitoring fetal safety. Progressive clinical improvement was observed, with complete resolution after three months. The pregnancy progressed without complications and fetal morphology remained normal under therapy. Conclusions: This case illustrates the diagnostic complexity of cervicofacial actinomycosis caused by A. georgiae during pregnancy, representing the first such report in the current literature, and emphasizes the need for a multidisciplinary approach. Full article

Soil contamination in South African agriculture poses escalating threats to food security and ecosystem integrity, yet the geospatial and machine learning evidence base addressing this problem has never been systematically synthesised. This scoping review, conducted within the PRISMA-ScR framework, applied SVM-assisted screening to 2000 retrieved records, yielding a final corpus of 228 eligible studies published from 2003 to 2025. To characterise temporal, thematic, and geographic patterns in the corpus, we applied machine learning-assisted topic modelling (LDA, k = 7), logistic growth modelling, keyword co-occurrence network analysis, and technology–contaminant evidence gap matrices. Remote sensing was the dominant methodology throughout the review period (n = 142; 62.3% of studies), with machine learning rising to the highest adoption rank from approximately 2020 onwards. Logistic modelling estimated a carrying capacity of K = 292.3 (95% CI: 269–324) studies and an inflexion year of 2020.2 (95% CI: 2019.4–2021.1), projecting 90% saturation by 2028. Research effort was highly concentrated in KwaZulu-Natal and the Eastern Cape, while Pesticides/Herbicides and acid mine drainage each comprised only three corpus studies. Deep learning registered zero entries across all cells of both the technology–contaminant and technology–province evidence matrices. Targeted investment in field validation, hyperspectral and deep learning deployment for underrepresented contaminants, and interpretable modelling for regulatory defensibility are identified as priority actions for the next research cycle. Full article