Search Results (292)

The mineral matter in coal has great significance for geological evolution, and clean and fractional utilization. The Laochang mining area is one of the largest anthracite coal production bases in Southern China, and the most important coal energy base in Yunnan province, China. This study investigates the composition and mode of occurrence of mineral matter in the Laochang coals to reveal the sediment provenance, sedimentary environment, and hydrothermal fluids. The predominant minerals in the Laochang coals include oxide (quartz, anatase), clay (kaolinite, illite/smectite mixed layer), sulfide (pyrite, sphalerite), phosphate (xenotime, monazite, goyazite–gorceixite), and carbonate (calcite, dolomite, sideroplesite, siderite). The minerals in the Laochang coals are dominated by quartz (2.4~54.8%) and kaolinite (3.4~39.2%), followed by illite, smectite, muscovite, calcite, pyrite, and anatase. Quartz and dolomite in SB-7+8 coal have the highest proportions, reaching 54.8% and 17.3%. The modes of occurrence of minerals reflect that the Laochang coals are affected by the epigenetic hydrothermal fluids and seawater. The chalcophile elements Hg, Pb, Se, and Cr, and lithophile elements Li, Nb, Ta, Zr, Hf, and REY are slightly enriched in XB-3 coal, which is attributed to the intrusion of seawater and the supply of terrestrial detrital materials, respectively. REY is dominated by LREY, followed by MREY, and a lower level of HREY in the Laochang coals, which have a high fractionation degree. The REY enrichment H-type is influenced by the hydrothermal fluids. Based on the relationship between Al₂O₃ and TiO₂, Al₂O₃/TiO₂ and Nb/Yb, and the negative anomaly Eu, the detrital material in the erosion source area of the Laochang coal is derived from the Emeishan Large Igneous Province basalt and felsic–intermediate rocks. Full article

Phosphate is a crucial non-renewable mineral resource, mainly utilized in producing fertilizers that support global agriculture. As phosphorus is an indispensable nutrient for plant growth, phosphate holds a key position in ensuring food security. While deposits are distributed worldwide, the largest reserves are concentrated in Morocco. The Benguerir phosphate mining in Morocco generates heterogeneous waste (i.e., including overburden, tailings, and phosphogypsum) that complicates management and valorization, which is the beneficial reuse or value recovery from waste materials (e.g., use in cover systems, buffering, or other engineered applications). Therefore, it is essential to characterize their mineralogical properties to evaluate their environmental impact and possibilities for reuse or site revegetation. To do so, we integrate VNIR–SWIR reflectance spectroscopy with HandHeld X-ray fluorescence (HHXRF) to characterize phosphate waste rock and assess its reuse potential. For this purpose, field samples (n = 104) were collected, and their spectral reflectance was measured using an ASD FieldSpec 4 spectroradiometer (350–2500 nm) under standardized laboratory conditions. Spectra were processed (Savitzky–Golay smoothing, convex-hull continuum removal) and matched to ECOSTRESS library references; across the dataset, library matching achieved mean RMSE = 0.15 ± 0.053 (median 0.145; 0.085–0.350), median SAM = 0.134 rad, median SID = 0.029, and mean R² = 0.748 ± 0.170, with 84% of spectra yielding R² > 0.70. In parallel, HHXRF major and trace elements were measured on all samples to corroborate spectral interpretations. Together, these analyses resolve carbonate–clay–phosphate assemblages (dolomite commonly dominant, with illite/smectite–kaolinite, quartz, and residual carbonate-fluorapatite varying across samples). Elemental ratios (e.g., Mg/Ca distinguishing dolomite from calcite; K/Al indicating illite) reinforce spectral trends, and phosphate indicators delineate localized enrichment (P₂O₅ up to 23.86 wt % in apatite-rich samples). Overall, the combined workflow is rapid, low-impact, and reproducible, yielding coherent mineralogical patterns that align across spectroscopic and geochemical lines of evidence and providing actionable inputs for selective screening, targeted material reuse, and more sustainable mine reclamation planning. Full article

Rock art in the Albarracín Cultural Park represents one of Spain’s most significant concentrations of post-Paleolithic paintings, yet comprehensive chemical characterization across multiple shelters remained lacking. This study analyzes 102 pigment samples (54 white, 31 black, 17 red) from 12 shelters using portable X-ray fluorescence spectroscopy. Centered log-ratio transformation addressed compositional data constraints, enabling multivariate analyses (PCA, LDA, MANOVA) that properly account for the constant-sum constraint inherent in geochemical data. Linear discriminant analysis achieved 92.6%–100% classification accuracy for site attribution, with barium emerging as the universal discriminating element across all pigment types (Cohen’s d = 4.91–9.19). Iron concentrations confirmed hematite/goethite use in red pigments, with inter-shelter variations suggesting different ochre sources. Black pigments revealed dual technologies: manganese oxides (pyrolusite) and carbon-based materials, with phosphorus enrichment in some samples consistent with possible bone-derived materials, though alternative phosphorus sources cannot be definitively excluded. This technological duality occurred within individual shelters, documenting greater complexity than previously recognized. White pigments combined substrate-derived materials with gypsum and aluminosilicate clay minerals (likely of the kaolinite group), occasionally incorporating phosphate-rich phases. The documented coexistence of compositionally distinct pigments within single shelters (whether from different raw material sources or varied preparation techniques) confirms the technical heterogeneity of Albarracín rock art and challenges assumptions about technological homogeneity in Levantine art production. This interplay between natural geological constraints and cultural technological choices underscores the need for complementary surface-sensitive techniques to fully resolve the technological repertoire of Levantine artists. Full article

Limited phosphorus (P) availability and declining soil biological health are major constraints in intensive rice (Oryza sativa L.)—wheat (Triticum aestivum L.) systems. Rock phosphate–enriched compost (REC), combined with microbial inoculants, offers a sustainable strategy for improving soil biological functioning. A field experiment was conducted under a randomized block design with seven treatments involving different combinations of REC, chemical fertilizers, phosphate-solubilizing bacteria (PSB), and arbuscular mycorrhizal fungi (AMF). Post-harvest soil samples from rice and wheat were analyzed for microbial biomass carbon (MBC), microbial biomass phosphorus (MBP), enzymatic activities, microbial populations, root colonization, yield, and P uptake. The combined application of REC with PSB and AMF significantly enhanced soil biological parameters compared with recommended fertilizer doses. Under the REC + PSB + AMF treatment, dehydrogenase, acid phosphatase, and alkaline phosphatase activities increased by 77.4%, 24.8%, and 18.1%, respectively, while MBC and MBP improved by 51.6% and 106.6%. Bacteria, fungi, and actinomycete population increased by 55.0%, 76.7%, and 82.8%, respectively, as well as mycorrhizal root colonization increased by 18.7%. Grain yield of rice and wheat increased by 16% and 6%, respectively, along with higher P uptake. The integrated use of REC with PSB and AMF improved soil enzymatic activity, microbial biomass, and nutrient acquisition, leading to higher crop productivity. These results indicate that REC combined with PSB and AMF is an effective nutrient management strategy for improving soil biological health, P utilization, and crop productivity in rice–wheat systems. Full article

The overuse of chemical fertilizers can result in elevated concentrations of nitrogen (N) and phosphorus (P) in soil, potentially impacting rock weathering processes and carbon flux in karst regions. This study analyzed the impacts of chicken dung fertilizer and compound fertilizer on the weathering of carbonate rocks within the water-soil-rock system, yielding the following results: (1) The peak concentrations of various ions in the compound fertilizer system (Ca²⁺: 36.8 mg/L, Mg²⁺: 4.3 mg/L, N: 284.2 mg/L, P: 920.6 mg/L, HCO₃⁻: 16,170.3 mg/L) were generally superior to those in the chicken manure fertilizer system (15.4 mg/L, 1.9 mg/L, 306.9 mg/L, 27.9 mg/L, and 4576.5 mg/L, respectively), with a difference of approximately fourfold between the two systems; (2) Nitric acid generated by nitrification in fertilizers and phosphoric acid in compound fertilizers modify the chemical equilibrium of rock weathering, enhance dissolution, and influence the dynamics of HCO₃⁻; (3) Nitrogen and phosphorus in compound fertilizers are predominantly eliminated through ion exchange and adsorption. Calcium-phosphate precipitates are generated on the limestone surface within the 20 cm soil column, exhibiting a greater degree of weathering compared to the chicken manure fertilizer treatment; (4) analyses utilizing XRD, FT-IR, XPS, SEM, and additional approaches verified that substantial weathering and surface precipitation transpired on limestone throughout the 20 cm compound fertilizer column. Full article

The growing demand for critical elements vital to the energy transition highlights the need for sustainable secondary sources. Sedimentary phosphate mining generates waste rock known as spoil piles (SPs). These SPs retain valuable phosphate and other critical elements such as rare earth elements (REEs). This study examines the potential of recovering these elements from SPs. A comprehensive sampling strategy was implemented, and a 3D topographic model was generated using drone imagery data. The model revealed that these SPs cover an area estimated at 48,633,000 m², with a total volume of approximately 419,612,367 m³. Chemical analyses using X-ray fluorescence and inductively coupled plasma mass spectrometry techniques indicated valuable phosphate content, with an overall concentration of 12.6% P₂O₅ and up to 20.7% P₂O₅ in the fine fraction (<1 mm). The concentrations of critical and strategic elements in the SPs were as follows: magnesium [1%–8%], REEs [67–267 ppm], uranium [48–173.5 ppm], strontium [312–1090 ppm], and vanadium [80–150 ppm]. Enrichment factors showed that these elements are highly concentrated in fine fractions, with values exceeding 60 for Y, 40 for Sr, and 780 for U in the +125/−160 µm fraction. A positive correlation was observed between these elements and phosphorus, except for magnesium. Automated mineralogy confirmed that the fine fraction (<1 mm) contains more than 50% carbonate-fluorapatite (CFA), alongside major gangue minerals such as carbonates and silicates. These findings demonstrate the potential for sustainable recovery of phosphate, magnesium, REEs, strontium, vanadium, and uranium from phosphate mining waste rock. Full article

To address the contradiction between the widespread prevalence of selenium deficiency and the growing demand for selenium-enriched fruits, this study utilized phosphate tailings (industrial solid waste), wood vinegar (a by-product of forestry processing), biochemical fulvic acid, and alginic acid (renewable biomass resources) to construct an organic–inorganic composite soil selenium activator. This formulation enhances the mobilization of inherent selenium in the soil without relying on exogenous selenium supplementation, thereby improving selenium bioavailability while mitigating the environmental pollution and resource depletion associated with external selenium inputs. Through field experiments, we systematically evaluated the influence of varying activator dosages on soil physicochemical properties, available selenium content, selenium distribution in different citrus organs, and fruit quality. The results demonstrated that the application of the compound activator at 600 g/plant significantly increased (p < 0.05) soil available selenium and fruit selenium content by 21.26% and 21.06%, respectively. During the fruit expansion stage of Sugar Orange, soil available selenium was elevated by 21.8%, which corresponded to a 21.09% increase in fruit selenium content. Regarding fruit quality parameters, Sugar Orange exhibited increases in soluble solids (35.8%), citric acid (20.3%), solid-to-acid ratio (77.8%), and selenium content (223.3%). In Rock Sugar Orange, significant enhancements were observed in soluble solids (46.1%), vitamin C (45.3%), total soluble sugars (73.4%), solid-to-acid ratio (156.6%), and selenium content (69.7%). Structural equation modeling revealed that soil available selenium, soil properties, and selenium content in citrus organs collectively exerted positive regulatory effects on fruit quality. Specifically, juice selenium content showed significant positive correlations with fruit shape index, individual fruit weight, soluble solids content, and solid-to-acid ratio. This strategy achieves the synergistic reuse of industrial solid waste and agricultural biomass resources, offering a green and sustainable pathway to enhance selenium content and quality in citrus fruits. Full article

Phosphorus is one of the elements necessary for life and the proper growth of organisms, including humans, yet its natural resources are very limited. The bioavailability of phosphorus is especially critical during the initial phases of plant growth. A deficiency at this stage cannot be fully compensated for later, even despite increased phosphorous supplementation. Global reserves of phosphate rocks, the main source of phosphorus used in fertilizer production, are gradually being depleted. This situation prompts the need to search for alternative sources and to pay closer attention to the sustainable management of available resources. In this article, we focus on the Vistula–Bug interfluve in southeastern Poland, where relatively high phosphate concentrations have been documented. Our goal is to present geochemical and mineralogical data from bedrock in the areas richest in phosphorus and to discuss their significance in the context of domestic phosphorous management, with particular reference to southeastern Poland. We also discuss phosphate fertilizer production in Poland and its use in agriculture as well as phosphorus content in groundwater and surface water in the study area, with emphasis on the most readily assimilable forms, orthophosphates. Finally, we address the challenges of sustainable phosphorous management at both the local and global scale. Full article

Phosphate rock is a vital natural resource classified by the European Commission as a critical raw material (CRM), extensively mined for its agricultural, industrial, and technological applications. While primarily used in fertilizer production, phosphate deposits also contain significant concentrations of trace metals, notably rare earth elements (REE), which are essential for renewable energy, electronics, and defense technologies. In response to growing demand, the recovery of REE from phosphate ores and processing by-products, particularly phosphogypsum (PG), has gained international attention. This review provides a comprehensive analysis of the global phosphate industry, examining production trends, market dynamics, and the environmental implications of phosphate processing. Special focus is placed on the geochemical behavior and mineralogical associations of REE within phosphate ores and industrial residues, namely PG and purification sludge. Although often treated as waste, these by-products represent underexplored secondary resources for REE recovery. Technological advancements in hydrometallurgical, solvometallurgical, and bioleaching methods have demonstrated promising recovery efficiencies, with some pilot-scale studies exceeding 70%–80%. However, large-scale implementation remains limited due to economic, technical, and regulatory constraints. The circular economy framework offers a pathway to enhance resource efficiency and reduce environmental impact. By integrating innovative extraction technologies, strengthening regulatory oversight, and adopting sustainable waste management practices, phosphate-rich countries can transform environmental liabilities into strategic assets. This review concludes by identifying key knowledge gaps and suggesting future research directions to optimize REE recovery from phosphate deposits and associated by-products, contributing to global supply security, economic diversification, and environmental sustainability. Full article

Background: Neuromyelitis optica spectrum disorder (NMOSD) causes severe optic nerve (ON) inflammation and vision loss. Current treatments remain limited, prompting exploration of new therapeutic strategies. This study evaluated the efficacy of ITRI-E-(S)4046 (ITRI-ES), a dual ROCK1/2 and MYLK4 kinase inhibitor, in a rat model of NMOSD optic neuritis. Methods: NMOSD-like optic neuritis was induced in rats by applying NMOSD patient serum-soaked sponges around the ON. Rats received intravitreal injections of either 0.2% ITRI-ES, phosphate-buffered saline (PBS), or intraperitoneal methylprednisolone (MP). Visual function was assessed using flash visual-evoked potentials (fVEP). Retinal ganglion cell (RGC) survival and apoptosis were quantified using FluoroGold retrograde labeling and TUNEL assay. ON inflammation and demyelination were evaluated via immunohistochemistry and Western blot analysis of aquaporin-4 (AQP4), myelin basic protein (MBP), glial fibrillary acidic protein (GFAP), and inflammatory markers. Results: ITRI-ES significantly preserved visual function, restoring fVEP amplitudes (~36 μV vs. ~21 μV in PBS-treated, p < 0.05) and RGC density (~85% of normal vs. ~37% PBS). RGC apoptosis was reduced (~2.3-fold lower vs. PBS, p < 0.05). PBS-treated rats showed decreased AQP4 and MBP (2.5–2.8-fold vs. sham) and increased GFAP (2.8-fold). ITRI-ES maintained higher AQP4 (~3.5-fold) and MBP (~1.5-fold) levels, suppressed GFAP (~5.5-fold vs. PBS), reduced NF-κB, IL-1β, TNF-α, microglia activation, and macrophage infiltration, and increased anti-inflammatory Arg1 and CD206 markers (~3-fold vs. PBS). Conclusions: ITRI-ES alleviates optic nerve inflammation, preserves retinal integrity, and maintains visual function in NMOSD-associated optic neuritis, underscoring kinase inhibition as a promising therapeutic strategy. Full article

This study investigates the adsorption efficiency of thermally activated natural opoka, a siliceous–calcareous sedimentary rock, as a low-cost adsorbent for removing phosphorus from aqueous solutions. Comprehensive characterization using XRF, XRD, and STA revealed that raw opoka is primarily composed of quartz, tridymite, and calcite, with a CaO/SiO₂ molar ratio of approximately 0.45. After calcination at 850 °C, calcite decomposes and reacts with silica to form wollastonite, enhancing surface reactivity. Adsorption experiments conducted at phosphorus concentrations of 0.2, 2.6, and 5.0 g of P/L demonstrated that the material’s removal efficiency for phosphorus was highest at low concentrations (25.7% at 0.2 g/L) and decreased with an increase in concentration (20.8% at 2.6 g/L and 18.6% at 5.0 g/L). The adsorption process followed pseudo-second-order kinetics (R² > 0.999), indicating that chemisorption is the dominant mechanism. It is assumed that amorphous calcium phosphate forms at low phosphorus concentrations and an alkaline pH, whereas brushite is more prevalent at higher concentrations under acidic conditions. Potassium adsorption was negligible and reversible in all cases. The findings demonstrate that calcined opoka has promising applications as a reactive calcium silicate material for sustainable phosphorus management in decentralized water treatment systems. Full article

Plant growth-promoting bacteria (PGPB) have a wide range of applications in agriculture and environmental management. They act as biostimulants and biofertilizers to enhance crop quality and yields in a more sustainable way. The present research aimed at isolating three active strains from the arid rhizosphere soil to act as biofertilizer. The plant growth-promoting features were evaluated in vitro and their implementation on pepper growth and yield were assessed and measured. Regarding IAA and ammonia production, the three designated isolates (P21, P22-1 and P58) showed patterns of high IAA production, producing 154.47 µg/mL, 155.03 µg/mL, and 188.65 µg/mL, respectively. Furthermore, considerable amounts of ammonia were detected in the supernatant of peptone water medium after 72 h of growth. Isolate P21 produced the maximum amount and generated 17.38 μmol/mL, whereas both P22-1 and P58 displayed lower amounts (15.47 and 15.92, respectively), without significant differences. P-solubilization efficacy calculated 18.7% (isolate P21), 64% (isolate P22-2), and 54% (isolate P58) when compared with un-inoculated medium. The molecular identification by 16S rRNA displayed that the three isolates belonged to Pseudomonas alkylphenolica strain P21 (PX257452), Pantoea agglomerans strain P22-1 (PX257453), and Pantoea brenneri strain P58 (PX257454). Applying the selected strains with sweet pepper in the presence of rock phosphate (RP) was assessed under greenhouse conditions. Three treatments (adding bacterial suspension at 0, 10 and 20 days after transplanting) from P21, P22-1, and P58 strains revealed that P21(3), P21(2), P22-1(3), and P58(3) treatments are considered the most promising treatments related to plant height, root length, leaf area, number of leaves per plant, leaf P-uptake, and stem P-uptake in addition to total plant P-uptake. In addition, the PCA biplot showed that MSP (mono-super phosphate), P22-1(3), and P58(3) are closely associated with high phosphorus uptake, indicating their effectiveness in enhancing phosphorus absorption by solubilizing insoluble forms. Eventually, PGPB will help the environment by improving soil fertility and structure, decreasing the need for toxic chemical fertilizers, and improving ecosystem health overall. Full article

The use of bioinoculants aligns with ecological intensification in agriculture, but their effects on crop performance and soil microbiota under different fertilization regimes remain unclear. This study evaluated the impact of a bioinoculant containing two phosphate-solubilizing bacterial strains (Priestia megaterium and Bacillus subtilis) on maize yield, root architecture, and rhizosphere microbial communities via seed inoculation in a clayey soil. Maize was cultivated for two consecutive seasons under treatments combining inoculation, phosphorus sources (triple superphosphate or reactive rock phosphate), and P doses (0 or 120 kg ha⁻¹ of P₂O₅). Root traits, phosphatase activities, and microbial diversity were assessed at flowering, while agronomic parameters and nutrient content were measured at harvest. In the first season, microbial alpha diversity was higher, accompanied by a 31.5% increase in root surface area and a 46.2% increase in P-resin availability. In contrast, the second season showed greater phosphatase activity and higher grain P and K concentrations, by 42.3% and 38.2%, respectively. Grain yield did not differ significantly between inoculated and non-inoculated treatments; however, root, plant, and microbial traits varied markedly across seasons. Principal component analysis revealed that productivity was primarily driven by seasonal variation rather than by fertilization or inoculation. These findings emphasize that the effectiveness of bioinoculants and P fertilization, as well as their influence on the microbiota, are highly context-dependent, being shaped by environmental conditions, soil nutrient availability, and crop genotype. Full article

When excavating roadways in underground mines, stress redistribution within the surrounding rock mass leads to stress concentration and release. Should the concentrated stresses exceed the rock mass’s tensile or shear strength, rock deformation and failure occur. Thus, a knowledge of stress distribution around the roadway is of great significance for revealing the roadway instability mechanism and design support methods. In this work, the powerful complex variable function theory was used to solve the surrounding rock stress around the triple-arched roadway and the analytical results were verified with the on-site stress state. The results show that the tensile stress occurs on the roadway roof and floor under low lateral stress coefficients, while concentrated compressive stress emerges on the two sidewalls. However, the surrounding stress distribution exhibits an opposite characteristic under high stress levels. Beyond five times the roadway radius, the stress in the surrounding rock is unaffected by the roadway and approaches the in-situ stress. For the +1890 m level trackless transport roadway in Kunyang No. 2 phosphate mine, it is further calculated that the minimum stress concentration factor in the rib area of the roadway within the stress relief zone is 0.34, while the maximum stress concentration factor in the concentrated stress zone of the roof, floor, and sidewalls of the roadway is 5.87. The measured stress values of two monitoring points in the surrounding rock of this roadway are fairly consistent with the analytical values, suggesting the complex variable method for solving excavation-induced stresses are effective and reliable. Full article

Critical metals associated with aluminum-bearing strata have garnered increasing attention due to their considerable economic potential. Recent investigations have identified notable enrichment of Li, Ga, Zr, Nb, REEs (rare earth elements), etc., within the Upper Carboniferous Benxi Formation in the Yangquan mining area, the Northeastern Qinshui Basin, Northern China. However, their mineralogical characteristics and micro-scale modes of occurrence remain insufficiently constrained. In this study, we employed the TESCAN Integrated Mineral Analyzer (TIMA) in combination with X-ray diffraction (XRD) and clay-separation experiments to provide direct mineralogical evidence for the occurrence of Ti, Li, Ga, Zr, and REEs in claystone and aluminous claystone from the Benxi Formation, Yangquan mining area, Northeastern Qinshui Basin. Our results indicate that both lithologies are primarily composed of kaolinite and diaspore, with minor amounts of anatase and cookeite; illite is additionally present in the claystone. Titanium predominantly occurs as anatase in both lithologies, though a portion in aluminous claystone may be incorporated into kaolinite and other Ti-bearing minerals such as rutile and leucoxene. Lithium is primarily hosted by cookeite in both rock types. Mineral assemblage variations further suggest that kaolinite may have partially transformed into Li-rich chlorite (i.e., cookeite) during the transformation from aluminous claystone to claystone. Gallium is chiefly associated with diaspore and kaolinite, with a stronger correlation with diaspore in the aluminous claystone. Zircon is the sole carrier of Zr in both lithologies. Importantly, La and Ce show a consistent spatial association with O–Al–Si–Ti–P mixed aggregates in TIMA maps, particularly in aluminous claystone. Based on these spatial patterns, textural relationships, and comparisons with previous studies, phosphate minerals are inferred to be the dominant REE hosts, although minor contributions from other phases cannot be completely excluded. These findings highlight a previously underexplored mode of critical-metal enrichment in Northern Chinese bauxite-bearing strata and provide a mineralogical basis for future extraction and utilization. Full article