Search Results (556)

Elemental migration and enrichment are important processes influencing tea plant growth and the assembly of rhizosphere bacterial communities within the rock–soil–plant continuum. This study explores how soil parent materials (granite, quartz schist, and sericite schist) are potentially associated with these processes and their observed associations with the elemental composition of tea leaves. Exploratory statistical analyses revealed distinct, lithology-specific biogeochemical patterns that serve as a foundation for hypothesis generation. In granite soils, chlorite correlated with the mobility of Cr, Pb, Cu, Ni, Mg, and Na, coinciding with shifts in the relative abundances of Verrucomicrobia, Armatimonadetes, and Chloroflexi. In quartz schist, kaolinite exhibited notable correlations with the dynamics of Pb, Cr, Ni, Zn, and As, which were statistically linked to Planctomycetes, Proteobacteria, and Acidobacteria. Complex mineral–microbe interactions were observed in sericite schist soils, where clay minerals (e.g., chlorite, illite) were closely associated with the migration of multiple elements (Pb, K, Ca, Cd, As, Al, Fe, Zn), paralleling structural variations in communities of Actinobacteria, Planctomycetes, Chloroflexi, and Proteobacteria. Potassium (K), calcium (Ca), and manganese (Mn) showed bioaccumulation tendencies in tea leaves across all lithologies, with an enrichment capacity order of Ca > K > Mn > Mg > Na > Al. Exploratory Classification and Regression Tree (CART) analysis suggested that the migration of K, Ca, Cu, Zn, and Hg corresponded most closely with their soil concentrations. Manganese (Mn) exhibited a mineral-associated trend, with kaolinite content as a potential correlate, while cadmium (Cd) migration was statistically linked to the relative abundance of Armatimonadetes. These findings highlight potential candidate relationships between mineralogy, microbes, and elemental mobility rather than confirming causal mechanisms, emphasizing the need for further validation in larger or experimental datasets. Full article

Soils play a fundamental role in plant nutrition as primary sources of potassium (K) and magnesium (Mg), whose availability depends on soil properties and environmental conditions. The composition of major cations in the soil solution is governed by interacting factors, including soil texture, acidity, mineralogical composition, and seasonal variability during the growing cycle. This study examines the availability, mobility, and seasonal dynamics of K and Mg in the soil solution of seven naturally managed soils across four distinct periods of a complete growing season beginning in spring. An integrated field and laboratory approach was applied to assess the influence of clay mineralogy on K and Mg behavior and overall soil fertility. Seasonal soil samples were analyzed for mineral composition, total elemental chemistry, exchangeable cation pools, and soil solution chemistry. Total elemental concentrations were determined by inductively coupled plasma mass spectrometry (ICP-MS), and clay mineral assemblages were identified by X-ray diffraction (XRD), focusing on 2:1 clay minerals, mixed-layer phases, and hydroxy-interlayered minerals (HIMs). The soils were dominated by 2:1 and mixed-layer assemblages, including illite/smectite (Ill/Sm), mica/illite–vermiculite (M/Vm), and chlorite/smectite (Chl/Sm), as well as transitional HIMs such as hydroxy-interlayered smectite (HIS) and hydroxy-interlayered vermiculite (HIV). Exchangeable Mg (0.28–1.30 cmolc kg⁻¹) and K (0.12–0.97 cmolc kg⁻¹) occurred in relatively high amounts, with maximum base saturation values of 13.14% (Mg) and 4.55% (K). Soil solution concentrations ranged from 1.60 to 3.00 ppm for K⁺ and 0.90–1.70 ppm for Mg²⁺, indicating substantial mobility and enrichment from the solid phase. These findings demonstrate that 2:1 clay minerals and mixed-layer phases act as key reservoirs regulating K and Mg exchangeability and release under natural acidic conditions, thereby sustaining soil fertility and nutrient availability for plant uptake. Full article

Arsenic (As) contamination of soils is a critical environmental and geochemical concern, with its mobility and bioavailability largely controlled by molecular-scale interactions with soil minerals. This study investigates the adsorption behavior of arsenate [As(V)] and arsenious acid [As(III)] on major clay minerals to elucidate fundamental controls on As retention in soil and sediment systems. Molecular modeling approaches were employed to investigate these interactions. Density functional theory (DFT) calculations were performed on cluster models of illite, chlorite, montmorillonite, and kaolinite to evaluate adsorption configurations and binding energies of arsenate and arsenious acid. In addition, semiempirical (PM6) and classical force-field (UFF) methods were used to examine the influence of vermicompost-derived organic matter on arsenate-mineral interactions. Multiple adsorption configurations, including atop atom, bridge, three-fold filled, and three-fold hollow sites, were evaluated, and binding energies were calculated with correction for basis set superposition error. The results indicate that three-fold hollow sites are the most favorable, with As(V) binding energies of 60–65 kcal mol⁻¹ on illite, chlorite, and montmorillonite, reaching 75 kcal mol⁻¹ on kaolinite at a surface distance of 2.7 Å. In contrast, As(III) shows weaker and energetically flatter adsorption, with binding energies of 28–54 kcal mol⁻¹ and larger equilibrium distances of 3.2–4.0 Å. Modeling of vermicompost addition suggests a substantial reduction in arsenate binding on most clay minerals, except illite, indicating competitive or disruptive interactions at mineral surfaces. These findings provide quantitative, atomistic insight into mineral- and amendment-specific controls on As stabilization and mobility in soil and sediment systems. Full article

This study evaluated the geotechnical, mineralogical, chemical, and physico-mechanical properties of natural clays from two Portuguese regions, Aveiro and Taveiro, for their potential use as compacted landfill liners. A comprehensive set of tests was conducted, including particle size distribution, Atterberg limits, specific surface area (SSA), cation exchange capacity (CEC), swelling potential, and hydraulic conductivity (K), complemented by X-ray diffraction (XRD) and chemical composition (XRF) analyses. Results showed that Aveiro clays were predominantly fine-grained, with clay fractions exceeding 65% and high Σphyllosilicates content, particularly illite and smectite. These samples exhibited low hydraulic conductivity (K < 1 × 10⁻⁹ m/s), moderate to high plasticity, and good sealing behavior. In contrast, Taveiro clays showed greater textural variability, with higher sand content and a wider range of mineral composition, from kaolinitic to smectitic units. Selected Taveiro samples also achieved acceptable permeability values, particularly those with higher smectite content, but may require strict compaction control or blending with finer materials. The CEC and SSA measurements further distinguished the sealing potential between clay types, correlating with mineralogy and swelling capacity. The use of local clays offers potential cost savings and environmental benefits, including reduced transportation emissions and support for circular economy principles. These findings highlighted the technical viability of Portuguese clays for landfill barrier systems and underscore the importance of localized characterization for optimized liner design. Full article

The TaiLing Mausoleum in Western Qing Tombs has great aesthetic value and a rich history. In this study, we conducted an analysis of the materials used in the architectural polychrome paintings of the TaiLing Mausoleum. Optical microscopy (OM), portable X-ray fluorescence (p-XRF), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM–EDX), micro-Raman spectroscopy (μ-RS), and X-ray diffraction (XRD) were used to analyze the paintings of Long’en Gate in TaiLing Mausoleum. The results indicate that the main minerals in the ground layer are quartz, augite, feldspars and illite. The gilding materials employed gold leaf. The red pigment is hematite, and the black pigment is carbon black. The green pigment is emerald green with barium sulfate as an extender. The blue pigments are smalt and synthetic ultramarine. In some areas, emerald green is observed overlaying smalt, suggesting that the paintings at Long’en Gate underwent overlay restoration or repainting from the late Qing Dynasty to modern times. These results can support future conservation of the polychrome paintings at the TaiLing Mausoleum. Full article

This study addresses the challenges posed by weakly cemented strata in mine tunnels, where surrounding rock softens and deforms upon water exposure, which promotes the development of seepage pathways, and exhibits insufficient stability in bolt (cable) support systems. This study conducts laboratory grouting tests using silica sol on typical weakly cemented sandstone from Xinjiang mining areas. The mineral composition and pore structure were characterized using XRD, SEM, and mercury porosimetry. The injectable mixing ratio parameters for silica sol and the catalyst were determined through viscosity-time evolution tests. Grouting was performed using a custom-built constant-pressure grouting apparatus. After curing, unconfined compressive strength (UCS) and porosity-permeability tests were conducted to evaluate the micro-mechanism of grouting effects on the mechanical and permeability properties of weakly cemented sandstone. The results indicate: (1) The sandstone exhibits a high clay mineral content of 39.8%, dominated by illite. Its pores are primarily small-scale (10–100 nm), accounting for 79.31% of the total pore volume. This scale matches that of silica sol nanoparticles (approximately 9–20 nm), facilitating slurry penetration into micro-pores; (2) microscopic analyses reveal that silica sol effectively reconstructs pore structures through permeation filling and surface coating. Compared to KCl-induced gelation (with approximately 8% gel coverage), NaCl-induced gelation forms a more continuous gel film with more complete pore filling, achieving coverage of around 22%. Furthermore, the larger surface area of the gel aggregates indicates a more thorough filling of micro- and nano-pores, effectively enhancing rock mass compactness. (3) Permeability decreased from 6.91 mD to 3.55 mD, a reduction of 48.6%, while porosity decreased from 16.94% to 13.55%, showing a phased reduction during the grouting process; (4) following pressure grouting stabilization, the uniaxial compressive strength of sandstone increased appropriately by approximately 7–14%, while the elastic modulus rose by about 18–28%. The failure mechanism shifted from shear brittleness to a shear-tension composite state, with enhanced post-peak bearing capacity. These findings provide support for optimizing silica sol grouting parameters in weakly cemented strata tunnels and for the synergistic reinforcement of rock mass permeability and strength. Full article

In this study, the occurrence and leachability of rare earth elements and yttrium (REY) in medium-rank coal—meta-bituminous B coal from the southwestern part of the Upper Silesian Coal Basin in Poland—were investigated. The coal samples contained variable amounts of siderite, dolomite, calcite, kaolinite, illite, quartz, apatite, and pyrite in their mineral composition. A five-step sequential chemical leaching procedure was used, including deionized water, 3% HCl, 5% HNO₃, 10% HNO₃ with microwave assistance, and concentrated HCl–HF also with microwave assistance. The highest concentrations of ∑REY were observed in seam 404/1. Light REY (LREY) dominated the REY composition (>75%), while heavy REY (HREY) accounted for less than 10%. The chondrite-normalised REY patterns and total REY content indicate a clastic origin of REY-bearing minerals. The most efficient leaching occurred in stages IV and V. The solutions from stages I–III preferentially mobilised critical REY, while those from stages IV–V reflected the REY distribution in the coal. Based on the C_outl index, both coal and leachates from the later stages are classified as prospective REY resources. However, absolute REY concentrations should be considered when interpreting C_outl values. The positive correlation between apatite and kaolinite contents and ∑REE concentrations suggests their role in REY enrichment. Full article

This study investigates four rock–soil profiles developed from Proterozoic intermediate–acid rocks in the Maoniushan area of Xichang, Sichuan Province. Through systematic geochemical analysis of major and trace elements and X-ray diffraction analysis of clay minerals, we aim to clarify the dominant controlling factors and environmental response mechanisms of chemical weathering under similar lithological and soil-forming age conditions. The results indicate the following: (1) Major element geochemistry shows that the Chemical Index of Alteration (CIA) of all profiles ranges from 61 to 74, while Na/K ratios and A-CN-K diagrams collectively reveal that the profiles are in a transitional stage from weak weathering (Ca and Na depletion) to moderate weathering (K depletion), with the weathering intensity ranking in the order TP1711 > TP1709 > TP1714 ≈ TP2801. (2) Trace elements exhibit significant differences among profiles: Cu, Zn, and Pb are significantly leached relative to Al₂O₃ in the TP1711 profile, whereas most trace elements are enriched in the TP1714, TP1709, and TP2801 profiles. Variations in ∑LREE/∑HREE ratios further support differences in the weathering stages of the profiles. (3) The clay mineral assemblages are dominated by illite, chlorite, and vermiculite. The TP1714 profile lacks vermiculite and has the highest illite content (54–60%), reflecting a relatively cold and dry local microclimate. In contrast, the other profiles show widespread vermiculite development, accompanied by minor kaolinite, indicating moderate weathering intensity under warm and humid climatic conditions. This study confirms that under similar lithological and soil-forming age conditions, the microclimatic differentiation induced by altitude variation is the key external controlling factor leading to spatial differences in the chemical weathering intensity of granite–soil profiles in the Maoniushan area. Full article

Earth-based materials are increasingly considered as low-carbon alternatives for sustainable building construction. However, the high variability of natural soils and the complex behaviour of their clay fraction remain major barriers to the standardisation of characterisation and formulation methods. This study proposes a methodological and experimental framework based on the fine fraction (<400 µm) of soils to predict the fresh-state and hardened-state performance of earthen construction materials. Two natural soils from southwestern France with contrasted mineralogical compositions were investigated using rheological studies, compaction, linear shrinkage, and unconfined compressive strength (UCS) tests. The results show that the fine fraction plays a dominant role in governing material behaviour: smectite-rich soils reach higher dry densities (up to ≈2.10 g·cm⁻³) and compressive strengths (up to ≈6 MPa) but exhibit greater shrinkage sensitivity, whereas kaolinite–illite-rich soils display reduced shrinkage and improved dimensional stability. By demonstrating the predictive capacity of fine-fraction-based indicators for mechanical performance and dimensional stability, this work contributes to the development of simplified, reproducible, and environmentally relevant methodologies for the design of low-carbon earthen building materials using locally sourced soils. Full article

Accurate determination of the physico-mechanical parameters of rock and soil masses is fundamental to the quantitative stability analysis and engineering mitigation of open-pit mine slopes. However, existing studies often rely on generalized parameters and lack systematic empirical data based on full-hole in situ core sampling to quantitatively verify the link between microscopic mineralogy and macroscopic instability. To address this gap, this study investigates the mineral composition, microstructure, and hydro-mechanical behavior of geotechnical materials, using the XG Open-pit Coal Mine in Inner Mongolia as a case study. Field drilling and sampling with a cumulative depth of 1500.7 m were conducted, combined with systematic laboratory tests. The results reveal significant lithological heterogeneity within the mining area. Specifically, hard rocks (e.g., fine sandstone) constitute the stable framework of the slope, whereas mudstones rich in hydrophilic clay minerals, along with low-strength coal seams, form potential weak sliding interfaces. Quantitative X-ray Diffraction (XRD) analysis reveals that the weak mudstone layers contain up to 32.4% hydrophilic expansive minerals (montmorillonite and illite/smectite). Scanning Electron Microscopy (SEM) and slake durability tests demonstrate that the mudstone is characterized by well-developed micropores (1–2 μm) and loose cementation. Theoretical analysis indicates that upon saturation, the strength of these weak layers is reduced by over 40%, causing the factor of safety (FoS) to drop from a stable 1.48 to a critical 0.89. Based on these findings, the slope instability mechanism driven by “Stiffness Mismatch and Hydro-Weakening” is elucidated. Consequently, targeted reinforcement and drainage measures are proposed to provide a scientific basis for safe mining operations. Full article

Understanding the carbonation behavior of lime-based mortars is essential for ensuring material compatibility and long-term durability in architectural restoration. This study presents a comparative spectroscopic and mineralogical analysis of eleven mortar samples collected from both the original (11th–12th century) and modern extension walls of a historic structure. X-ray diffraction (XRD) and attenuated total reflectance–Fourier transform infrared spectroscopy (ATR-FTIR) were employed to assess the mineralogical composition and carbonation maturity. The results indicate that the historic mortars have undergone complete carbonation, as evidenced by sharp and well-defined calcite bands, whereas the modern repair mortars display broader carbonate peaks, suggesting ongoing carbonation processes. XRD analysis confirmed the dominance of calcite and gypsum, along with the presence of illite, albite, and microcline, indicating mineralogical signatures of both binder transformations (such as carbonation and sulfate formation) and aggregate contributions. The weak water absorption bands and limited sulfate signals observed in the spectra further suggest advanced aging and mineral stabilization in the historic mortars. These findings highlight the differing carbonation kinetics between historic and modern lime mortars and emphasize the importance of selecting repair materials with compatible chemical and physical aging characteristics. The combined use of XRD and ATR-FTIR proves to be an effective diagnostic approach to guide restoration material selection and support the long-term integrity of masonry structures. Full article

The McMurdo Dry Valleys (DVs) of South Victoria Land, Antarctica, constitute the largest ice-free region on the continent and one of Earth’s most Mars-analog environments. Their hyper-arid polar desert conditions offer a unique setting for investigating surface weathering and mineralogical processes under extreme climates. This study presents the first regional-scale mapping of alteration and crystalline weathering minerals across the McMurdo DVs. It uses Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) multispectral data; visible and near-infrared (VNIR) and shortwave infrared (SWIR) bands were analyzed through a Spectral Hourglass Workflow, endmember extraction, and spectral unmixing with Matched Filtering (MF) and Constrained Energy Minimization (CEM). Inter-algorithm consistency analysis between MF and CEM yielded 78.83% overall agreement with a Kappa coefficient of 0.75, indicating strong methodological consistency in mineral discrimination using ASTER VNIR+SWIR data. It should be noted that this agreement reflects internal algorithmic robustness rather than independent geological validation. Geological reliability is instead supported by documented field observations, lithological map comparisons, and spectral correspondence with the USGS spectral library. Validation employed documented field observations, lithological maps, and the USGS spectral library. Results reveal distinct spatial distributions of hematite-limonite/goethite, jarosite, kaolinite/smectite-illite-pyrophyllite-alunite, muscovite, hydrous silica/sericite/jarosite/hematite, epidote/chlorite, and calcite, closely associated with lithological units and unconsolidated deposits in Taylor, Wright, Victoria, and McKelvey Valleys. An inter-algorithm consistency check achieved 78.83% overall accuracy with a Kappa coefficient of 0.75, underscoring the robustness of ASTER VNIR+SWIR data for Antarctic mineral discrimination despite localized spectral mixing. Beyond refining the geological understanding of the McMurdo DVs, these results establish ASTER as an effective tool for regional mineralogical mapping in inaccessible polar terrains. The findings further strengthen the role of the Dry Valleys as a terrestrial analog for Mars, where similar mineralogical assemblages and spectral ambiguities have been observed, thereby contributing to both Antarctic geoscience and planetary exploration frameworks. Full article

Tight oil reservoirs are widely recognized as a critical successor in global unconventional energy development and are generally characterized by distinct geological features, including fine pore throats, pronounced heterogeneity, and a high concentration of clay minerals (e.g., montmorillonite and mixed-layer illite/smectite). Severe hydration, swelling, and fines migration are readily induced during water injection or conventional water-based fluid operations, thereby resulting in irreversible impairment of reservoir permeability. Despite the excellent injectivity and capacity for viscosity reduction associated with CO₂ flooding, sweep efficiency is severely compromised by viscous fingering and gas channeling, which are induced by the inherent low viscosity of the gas. While CO₂ foam technology is widely acknowledged as a pivotal solution for addressing mobility control challenges, its implementation is hindered by a primary technical bottleneck: the incompatibility between traditional water-based foam systems and strongly water-sensitive reservoirs. A dual challenge comprising water injectivity constraints and gas channeling is presented by strongly water-sensitive tight oil reservoirs. To address these impediments, three emerging low-damage CO₂ foam systems are critically evaluated in this review. First, the synergistic mechanisms of novel quaternary ammonium salts and polymers in inhibiting clay hydration and enhancing foam stability within modified water-based systems are elucidated. Next, the physical isolation strategy of substituting the water phase with a non-aqueous phase (oil/organic solvent) in organic emulsion systems is analyzed, highlighting advantages in wettability alteration and the mitigation of water blocking. Finally, the prospect of waterless operations using CO₂-soluble foam systems—wherein supercritical CO₂ is utilized as a surfactant carrier to generate foam or viscosify fluids via in situ formation water—is discussed. It is revealed by comparative analysis that: (1) Modified water-based systems are identified as the most economically viable option for reservoirs with moderate water sensitivity, wherein cationic stabilizers are utilized to inhibit hydration; (2) Superior wettability alteration and the elimination of aqueous phase damage are provided by organic emulsion systems, rendering them ideal for ultra-sensitive, high-value reservoirs, despite higher solvent costs; (3) CO₂-soluble systems are recognized as the future direction for “waterless” flooding, specifically tailored for ultra-tight formations (<0.1 mD) where injectivity is critical. Current challenges, such as surfactant solubility, high-temperature stability, and cost control, are identified through a comparative analysis of these three systems with respect to structure-activity relationships, rheological properties, damage control capabilities, and economic feasibility. What is more, an outlook is provided on the molecular design of future environmentally sustainable, cost-effective CO₂-philic materials and smart injection strategies. Consequently, theoretical foundations and technical support are established for the efficient exploitation of strongly water-sensitive tight oil reservoirs. By bridging the gap between reservoir damage control and mobility enhancement, this study identifies viable strategies for enhanced oil recovery. Crucially, it supports carbon neutrality and sustainable energy targets via CCUS integration. Full article

This study investigates a karst bauxite deposit from NE Spain with a dual objective incorporating the novel aspect of directly linking genetic processes to industrial ceramic performance. First, the bauxite is mineralogically and texturally characterized using X-ray diffraction and field emission scanning electron microscopy. Second, the mineralogical and textural transformations of the bauxite during firing at 1000, 1200 and 1300 °C are analyzed, together with their effects on the physical properties of the fired products. The Lower Cretaceous bauxite is autochthonous, shows a pisolithic structure, and formed in situ under tropical monsoon conditions through intense chemical weathering involving dissolution–crystallization processes. For ceramic testing, the bauxite was mixed with illitic–kaolinitic clays in a 90/10 proportion. During firing, kaolinite and illite destabilize and transform into mullite, initially by solid-state reactions at 1000 °C and subsequently by crystallization from a vitreous phase at higher temperatures, producing larger crystals and composition closer to the empirical mullite formula. The formation of vitreous phase and mullite leads to reduced porosity and increased density and linear shrinkage, particularly between 1000 and 1200 °C. Specimens fired at 1300 °C show higher mechanical strength, related to higher mullite content and a larger size of its crystals. The results demonstrate the potential interest of these bauxites for ceramic manufacturing. Full article

The horst and graben system in Western Anatolia lies on the eastern boundary of the Aegean extensional system, one of the most active extensional zones in the world. The Şahinali coal basin is located south of the Büyük Menderes Graben, which is part of this system. This study examines the rare earth elements and yttrium (REY) geochemistry, accumulation conditions, and economic potential of the Şahinali coals. Compared to world coals, the REE concentration in Şahinali coals (208.3 ppm) is quite high, and all REY groups are slightly enriched. Light REY (LREY) is dominant compared to medium REY (MREY) and heavy REY (HREY). The most abundant element in this group is Ce, reaching a concentration of 123.3 ppm. REY distribution patterns indicate H-type enrichment in most samples and, to a lesser extent, M-H-type enrichment. Element ratios (Al₂O₃/TiO₂, TiO₂/Zr, La/Sc, Co/Th) and REY anomalies (Ce, Eu, Gd) indicate that the sedimentary input is predominantly derived from felsic rocks, with limited intermediate to mafic contributions. SEM-EDS findings and correlation analyses indicate that REY are predominantly associated with aluminosilicate minerals. LREY-Th and MREY/HREY-Y relationships are supported by monazite and Y-rich illitic K-aluminosilicates. Paleoenvironmental indicators (V/Cr, Ni/Co, U/Th, Sr/Cu, Rb/Sr, Sr/Ba) indicate that the coal accumulated under oxic–suboxic, warm and humid conditions. The average REY oxide (REO) content slightly exceeds the commonly cited 1000 ppm screening threshold for coal ash. The majority of samples contain elevated proportions of critical REY (30.7%–54.3%) and show promising outlook coefficients (C_outl: 0.8–1.7). Together, these results indicate a favourable compositional signature for preliminary REY resource screening in the Şahinali coals, particularly with respect to elements relevant for high-technology applications. Full article