Search Results (71)

Understanding mineral–fluid interactions in shale under supercritical CO₂ (scCO₂) conditions is relevant for assessing long-term geochemical containment. This study characterizes mineralogical transformations and elemental redistribution in five Caney Shale samples serving as proxies for reservoir (R1, R2, R3) and caprock (D1, D2) facies, subjected to 30-day static exposure to pure scCO₂ at 60 °C and 17.23 MPa (2500 psi), with no brine or impurities introduced. SEM-EDS analyses were conducted before and after exposure, with mineral phases classified into silicates, carbonates, sulfides, and organic matter. Initial compositions were dominated by quartz (38–47 wt.%), illite (16–23 wt.%), carbonates (12–18 wt.%), and organic matter (8–11 wt.%). Post-exposure, carbonate loss ranged from 15 to 40% in reservoir samples and up to 20% in caprock samples. Illite and K-feldspar showed depletion of Fe²⁺, Mg²⁺, and K⁺ at grain edges and cleavages, while pyrite underwent oxidation with Fe redistribution. Organic matter exhibited scCO₂-induced surface alteration and apparent sorption effects, most pronounced in R2 and R3. Elemental mapping revealed Ca²⁺, Mg²⁺, Fe²⁺, and Si⁴⁺ mobilization near reactive interfaces, though no secondary mineral precipitates formed. Reservoir samples developed localized porosity, whereas caprock samples retained more structural clay integrity. The results advance understanding of mineral reactivity and elemental fluxes in shale-based CO₂ sequestration. Full article

The use of widespread and inexpensive clay minerals as adsorptive agents, as well as materials obtained by their chemical modification, can contribute to the solution of the problem of environmental pollution with antibiotics. This review considers the structural features of various natural clay minerals and the effect of these features on their sorption capacity. Based on the analysis of available papers (over the last 15 years, also including some fundamental basics over the last 20–30 years), it has been established that the main property of an antibiotic molecule affecting the ability to be adsorbed by a clay mineral is the hydrophilicity of the organic substance molecule. The leading properties that determine the ability of clays to adsorb antibiotics are the charge and area of their surfaces. The ability of antibiotic molecules to protonate and a partial change in the edge charge of mineral layers is determined by the acidity of the sorption solution. In addition, empirical evidence is provided that the most important factors affecting adsorption are the ionic strength of the sorption solution, the concentration of the adsorbent and adsorbate, and the interaction temperature. The diversity of the composition, structure, and properties of clay minerals allows them to be effective sorbents for a wide range of antibiotics. Full article

The possibility of collecting new archaeological elements useful in reconstructing the dynamics of population, production and commercial activities in the Bronze Age at the edge of the central-southern Venice Lagoon was provided between 2023 and 2024 thanks to an intervention of rescue archaeology planned during some water restoration works in the Giare–Mira area. Three small excavations revealed, approximately one meter below the current surface and covered by alluvial sediments, a rather complex palimpsest dated to the late Recent and the early Final Bronze Age. Three large circular pits containing exclusively purified grey/blue clay and very rare inclusions of vegetable fibres, and many large, fired clay vessels’ bases, walls and rims clustered in concentrated assemblages and random deposits point to potential on-site production. Two pyro-technological structures, one characterised by a sub-circular combustion chamber and a long inlet channel/praefurnium, and the second one with a sub-rectangular shape with arched niches along its southern side, complete the exceptional context here discovered. To analyse the relationship between the site and the natural sedimentary succession and to evaluate the possible extension of this site, three electrical resistivity tomography (ERT) and low-frequency electromagnetic (FDEM) measurements were collected. Several manual core drillings associated with remote sensing integrated the geophysical data in the analysis of the geomorphological evolution of this area, clearly related to different phases of fluvial activity, in a framework of continuous relative sea level rise. The typology and chronology of the archaeological structures and materials, currently undergoing further analyses, support the interpretation of the site as a late Recent/early Final Bronze Age productive site. Geophysical and geomorphological data provide information on the palaeoenvironmental setting, suggesting that the site was located on a fine-grained, stable alluvial plain at a distance of a few kilometres from the lagoon shore to the south-east and the course of the Brenta River to the north. The archaeological site was buried by fine-grained floodplain deposits attributed to the Brenta River. The good preservation of the archaeological structures buried by fluvial sediments suggests that the site was abandoned soon before sedimentation started. Full article

Swelling pressure is a key geotechnical property that influences the behaviour and stability of engineering structures built on expansive clayey soils. This pressure can be measured directly through laboratory tests or estimated using indirect methods. This paper analyses a dataset of undisturbed clay samples from southeastern Spain using advanced symbolic regression techniques, namely: deep symbolic regression (PhySO), high-performance symbolic regression (PySR), multi-objective symbolic regression (MOSR), and physics-guided symbolic regression (PGSR). These methods provide interpretable results as equations, unlike standard machine learning models. All generated equations showed high performance (R² > 0.91 and MAE < 23 kPa) and simplicity, making them suitable for practical engineering applications. PySR yielded the best overall metrics (R² = 0.933, MAE = 20.49 kPa), particularly excelling in high-pressure ranges, while PhySO demonstrated the most balanced performance, especially for low to medium pressures. MOSR minimized edge-case bias, and PGSR, despite lower overall performance, remained competitive. The plasticity index (PI) was identified as the most influential factor in all models, followed by the percentage of fines. The use of undisturbed samples enhanced the reliability of the findings, and the resulting equations enable a flexible estimation of swelling pressure based on commonly available geotechnical parameters. Full article

Salinity and clay mineral types have been shown to influence the migration and settlement efficiency of microplastics (MPs) under restrictive experimental conditions. However, current research is limited to deep trenches or laboratory conditions, and studies in the semi-enclosed sea area of the continental shelf are still lacking. We investigated the effects of bottom seawater salinity and clay mineral types on MPs distribution in surface sediments using the western part of the North Yellow Sea as an example, where current conditions are complex and salinity changes rapidly over short distances. Under detection conditions with a minimum detection limit of 10 μm, the abundance range of MPs in the investigated sea area reached 24–1134 items/(g dry weight). The distribution of MPs was in good agreement with the isohaline of the bottom seawater, and MPs tended to converge in the high salinity area. However, there is an exceptional case in which the temperature and salinity difference caused by the cold water mass can create a frontal flow that blocks the transport of terrigenous materials to the middle of the cold water mass. This phenomenon causes MPs to settle at the edge of the cold water mass. A significant positive correlation exists between montmorillonite with expansive properties and fragment MPs and MPs with particle size > 100 μm, which have a larger surface area (p < 0.05). The negative charges on the surface of MPs and clay minerals are neutralized, promoting the heterogeneous aggregation between clay minerals and MPs and accelerating the sedimentation process of MPs in the ocean. This is another important reason for the accumulation of MPs in the high-salinity region. This study provides a basis for pollution prevention and control of MPs in the shallow sea, supplying new insights into the effects of bottom seawater salinity and clay mineral type on the distribution of MPs. Full article

The Carboniferous–Permian strata in the Daning–Jixian Block, located on the eastern edge of the Ordos Basin, host multiple sets of tight gas reservoirs. However, systematic research on the characteristics and gas production differences of multilayer tight sandstone gas-bearing systems remains limited. Based on geochemical signatures, reservoir pressure coefficients, and sequence stratigraphy, the tight sandstone gas systems are subdivided into upper and lower systems, separated by regionally extensive Taiyuan Formation limestone. The upper system is further partitioned into four subsystems. Depositional variability from the Benxi Formation to the He 8 Member has generated diverse litho-mineralogical characteristics. The Shan 1 and He 8 Members, deposited in low-energy delta-front subaqueous distributary channels with gentle topography, exhibit lower quartz content (predominantly feldspar lithic sandstone and lithic quartz sand-stone) and elevated lithic fragments, matrix, and clay minerals (particularly chlorite). These factors increase displacement and median pressures, resulting in inferior reservoir quality. By comparing and evaluating the gas production effects under different extraction methods, targeted optimization recommendations are provided to offer both theoretical support and practical guidance for the efficient development of this block. Full article

Lithological mapping using satellite images, particularly hyperspectral data, helps in effectively defining the best initial targets for regional exploration. In this study, ZY1-02D hyperspectral image (HSI) data with moderate spectral and very high spatial resolution were employed for lithological mapping using spectral indices along with support vector machine (SVM) machine learning and spatial–spectral transformer (SSTF) deep learning methods in the Kohat–Pothohar Plateau at the eastern edge of the Main Boundary Thrust (MBT) in Pakistan. The research was accomplished using spectral profiles of minerals accompanied by false color composite (FCC), principal component analysis (PCA), SVM, and SSTF methods for classifying the main lithological units. The lithological discrimination map derived from the ZY1-02D data matched well with the known deposits and field inspections. The principal component analysis (PCA) obtained the highest eigenvalues and provided a significant discrimination of lithologies, particularly with hyperspectral data. The results revealed lithological units, three of which contained limestone and gypsum, while other lithological units were defined as sandstone, clay, and conglomerates. Field investigation and laboratory sample analysis through X-ray diffraction (XRD), photomicrographs, and spectral analysis confirmed the occurrence of limestone, gypsum, and sandstone, which are useful in identifying lithological units in the study area. This study will assist in more accurate geological discrimination and play a vital role in identifying oil and gas reservoirs, coal, gypsum, uranium, salt, and limestone deposits. Furthermore, the results of the SVM and SSTF techniques were quantitatively compared with the geological boundaries mapped in the field, showing an accuracy of nearly 89.7% and 92.1%, respectively. Overall, the methodology adopted showed great performance and strong potential for mapping alteration areas and lithological discriminations applied on the ZY1-02D hyperspectral data. Full article

The issue of geotechnical hazards induced by excavation in soft soil areas has become increasingly prominent. However, the retaining structure and surface settlement deformation induced by the creep of soft soil and spatial effect of the excavation sequence are not fully considered where only elastic–plastic deformation is used in design. To understand the spatiotemporal effects of excavation-induced deformation in soft soil pits, a case study was performed with the Huaxi Park Station of the Suzhou Metro Line S1, Jiangsu Province, China, as an example. Field monitoring was conducted, and a three-dimensional numerical model was developed, taking into account the creep characteristics of mucky clay and spatiotemporal response of retaining structures induced by excavations. The spatiotemporal effects in retaining structures and ground settlement during excavation processes were analyzed. The results show that as the excavation depth increased, the horizontal displacement of the diaphragm walls increased linearly and tended to exhibit abrupt changes when approaching the bottom of the pit. The maximum horizontal displacement of the wall at the west end well was close to 70 mm, and the maximum displacement of the wall at the standard section reached approximately 80 mm. The ground settlement on both pit sides showed a “trough” distribution pattern, peaking at about 12 m from the pit edge, with a settlement rate of −1.9 mm/m per meter of excavation depth. The excavation process directly led to the lateral deformation of the diaphragm walls, resulting in ground settlement, which prominently reflected the time-dependent deformation characteristics of mucky soft soil during the excavation process. These findings provide critical insights for similar deep excavation projects in mucky soft soil, particularly regarding excavation-induced deformations, by providing guidance on design standards and monitoring strategies for similar geological conditions. Full article

A comprehensive understanding of soil salinity characteristics and the vertical and spatial distribution of particle sizes in lakes and wetlands within arid zones, as well as elucidating their interrelationship, is crucial for effective wetland soil salinization management. In this study, the typical salinized wetland, the Ebinur Lake wetland, was selected as the research object. A total of 50 sampling points were established along the edge of Ebinur Lake, resulting in the collection of 200 soil samples from depths of 0–60 cm. The particle size distribution (PSD) of the soil samples was obtained by laser particle sizer, and the fractal dimension of the soil structure was deduced by applying fractal theory. The soluble salt content (TSS) and salt ions content were measured by laboratory physicochemical experiments. Finally, Pearson correlation and other methods were used to explore the relationship between soil salinity and soil particle size. The results showed the following: (1) Soil salinization in the study area was severe, and the accumulation of surface salts was obvious, with a mean value of 46,410 mg/kg. The spatial distribution of TSS was predominantly influenced by Cl⁻, SO₄²⁻, Na⁺ + K⁺, Mg²⁺, and Ca²⁺. (2) Across various soil depths, silt and sand were the primary constituents, with soil fractal dimensions (D_soil) ranging from 1.91 to 2.76, averaging 2.54, and a poor soil textural structure. The spatial distribution of D_soil closely mirrored that of TSS. (3) According to the correlation analysis results, as TSS increased, D_soil continued to rise, with an increasing content of clay, while the sand content decreased. Simultaneously, as the soil particles became finer, TSS and D_soil also increased, suggesting that sandy loam to silty soils in the study area were more prone to salt accumulation. Full article

Efficient and reliable corn (Zea mays L.) yield prediction is important for varietal selection by plant breeders and management decision-making by growers. Unlike prior studies that focus mainly on county-level or controlled laboratory-scale areas, this study targets a production-scale area, better representing real-world agricultural conditions and offering more practical relevance for farmers. Therefore, the objective of our study was to determine the best combination of vegetation indices and abiotic factors for predicting corn yield in a rain-fed, production-scale area, identify the most suitable corn growth stage for yield estimation using machine learning, and identify the most effective machine learning model for corn yield estimation. Our study used high-resolution (6 cm) aerial multispectral imagery. Sixty-two different predictors, including soil properties (sand, silt, and clay percentages), slope, spectral bands (red, green, blue, red-edge, NIR), vegetation indices (GNDRE, NDRE, TGI), color-space indices, and wavelengths were derived from the multispectral data collected at the seven (V4, V5, V6, V7, V9, V12, and V14/VT) growth stages of corn. Four regression and machine learning algorithms were evaluated for yield prediction: linear regression, random forest, extreme gradient boosting, and gradient boosting regressor. A total of 6865 yield values were used for model training and 1716 for validation. Results show that, using random forest method, the V14/VT stage had the best yield predictions (RMSE of 0.52 Mg/ha for a mean yield of 10.19 Mg/ha), and yield estimation at V6 stage was still feasible. We concluded that integrating abiotic factors, such as slope and soil properties, significantly improved model accuracy. Among vegetation indices, TGI, HUE, and GNDRE performed better. Results from this study can help farmers or crop consultants plan ahead for future logistics through enhanced early-season yield predictions and support farm profitability and sustainability. Full article

The Sierra Peña Blanca (SPB) region in Chihuahua, Mexico contains a significant uranium deposit representing about 40% of the country’s reserves. Common uranium minerals in this area include uranophane, schoepite, and weeksite/boltwoodite, with several superficial occurrences. Mining activities in the 1980s left unprocessed uranium ore exposed to weathering, with potential transport towards Laguna del Cuervo. This study presents an experimental simulation of uranium transport in SPB sediments using three approaches: (i) a batch experiment to evaluate the ideal adsorption of (UO₂)²⁺ by fine sediment; (ii) a column system fed with 569 mgU L⁻¹ UO₂(NO₃)₂ to simulate adsorption by different sediment particle sizes; (iii) a column system with an upper horizon of uranophane from the area, fed with deionized water, to simulate uranium weathering and transport in particulate material, determined by liquid scintillation counting, revealed that the clay fraction had the highest adsorption capacity for U. X-ray Absorption Fine Structure (XAFS) analysis at the U L₃ edge confirmed the U(IV) oxidation state and the fittings of the extended XAFS spectra confirmed the presence of the uranophane group of minerals. X-ray tomography further corroborated the distribution of particulate minerals along the column. The results suggest that the primary transport mechanism in SPB involves the fragmentation of uranium minerals, accompanied by eventual dissolution and subsequent adsorption of U onto sediments. Full article

Edge-oxidized graphene oxide (EOGO) is a nano-sized material that is chemically stable and easily mixed with water due to its hydrophilic properties; thus, it has been used in various engineering fields, particularly for the reinforcement of building and construction materials. In this study, the effect of EOGO in soil reinforcement was investigated. When mixed with soil, it affects the mechanical properties of the soil–GO mixture. Various amounts of the GO (0%, 0.02%, 0.06%, 0.1%) were added into the sand–clay mixture, and their geotechnical properties were evaluated via multiple laboratories testing methods, including a standard Proctor test, direct shear test, compressibility test, and contact angle measurement. The experimental results show that with the addition of EOGO in soil of up to 0.06% EOGO, the compressibility decreases, the shear strength increases, and the maximum dry density (after compaction) increases. Full article

Forest gaps alter the environmental conditions of forest microclimates and significantly affect the biogeochemical cycle of forest ecosystems. This study examined how forest gaps and non-gap areas affect soil’s physical properties and eco-stoichiometric characteristics. Relevant theories and methods were employed to analyze the impact of forest gaps on nutrient cycling in Pinus densiflora Sieb. (PDS) and Robinia pseudoacacia L. (RPL) forests located in the Taishan Mountains. The results revealed that (1) forest gaps significantly enhanced the soil physical properties of PDS and RPL forests compared to non-gap areas (NPs). Notably, the bulk density of the soil decreased by 53%–12%, particularly in the surface layer (0–20 cm). Additionally, its non-capillary porosity increased by 44%–65%, while the clay and silt content rose by 39%–152% and 24%–130%, respectively. Conversely, the sand content decreased significantly, by 24%–32% (p < 0.05). (2) The contents of C, N, and P in the gap soil of PDS forests showed a significant increase compared to those in non-gap soil, with increases of 56%–131% for carbon, 107%–1523% for nitrogen, and 100%–155% for phosphorus. There was a significant drop of 10%–33% and 39%–41% in their C:N and C:P ratios, respectively (p < 0.05). The contents of C and P in the gap soil of the Robinia pseudo acacia L. Forest increased significantly, by 14%–22% and 34.4%–71%, respectively. Its C:P and N:P ratios significantly increased, by 14% to 404% and 11% to 41%, respectively (p < 0.05). (3) Compared with NPs, the forest gap significantly reduced the soil electrical conductivity and increased the soil pH. Additionally, compared to the soil at the gap’s edge, the surface soil in the gap’s center had noticeably higher concentrations of C, N, and P. (4) Key variables affecting the soil pH, silt content, bulk density, and overall porosity in forest gaps include the concentrations of carbon (C), nitrogen (N), and phosphorus (P) present and their ecological stoichiometric ratios. The findings showed that forest gaps had a considerable impact on the soil’s physical characteristics and ecological stoichiometry. They also had a high potential for providing nutrients, which might aid in the establishment of plantation plants. Full article

Plastics are essential in modern civilization due to their affordability, simple manufacturing, and properties. However, plastics impact the environment as they decompose over a long period and degrade into microplastics. The construction sector has been exploring substituting conventional bricks with plastic bricks, as concrete and clay bricks consume natural resources and pollute the environment. The introduction of recycling plastic, and using plastic waste and sand mixtures to create Lego-like bricks has become a new trend. The bricks have superior properties to conventional bricks, such as a smoother surface, finer edges, easy application, crack-free, higher compression strength, almost zero water absorption, and reduced energy consumption. The study: compares the results of PE with sand and PET with sand samples to previous studies, confirms alignment, works as a control sample for PET and PE novel research, and validates the concept. Three plastic mixtures using two types of plastic waste (PE and PET) and sand were used. The plastic waste with sand was heated up to 200 °C. Plastic acts as a binder, while sand acts as a filler material. Optimized durability and cohesiveness were achieved at 30–40% plastic weight ratios. A mixture of PE and sand showed a maximum compressive strength of 38.65 MPa, while the PET and sand mixture showed 76.85 MPa, and the mix of PE and PET in equal proportions with sand resulted in 26.64 MPa. The plastic samples showed ductile behavior, with elongation between 20 and 30%, water absorption between 0 and 0.35%, and thermal conductivity from 0.8 to 1.05 W/(m/K). Carbon dioxide emissions are significantly reduced as compared to standard bricks. The CO₂ per brick (kg) was 0.008 and 0.0085 in the PE; 0.0085 and 0.009 in the PET; and 0.0065 and 0.007 in the PE mixed with PET. Full article

The study of lithium (Li), gallium (Ga), and rare earth elements (REY) within coal-bearing strata represents a cutting-edge concern in coal geology, ore deposit studies, and metallurgy research. With the rapid advancement of technology and emerging industries, the global demand for Li-Ga-REY has significantly escalated. Several countries worldwide are facing immense pressure due to shortages in Li-Ga-REY resources. Coal-associated Li-Ga-REY depositions have emerged as a pivotal direction for augmenting Li-Ga-REY reserves. To ascertain the enrichment distribution patterns and genetic mechanisms of Li-Ga-REY within the coal-bearing strata of the late Permian Heshan Formation in Wanfu mine, Xian’an Coalfield, Guangxi Province, this study carried out comprehensive testing and analysis on Li-Ga-REY enriched in the mineralized layers within the strata. The Heshan Formation in Wanfu mine presents four layers of Li-Ga-REY-enriched mineralization, labeled from bottom to top as mineralized layers I, II, III, and IV, corresponding to coal seams K5, K4, K3, and K2. These critical metals are predominantly hosted within clay minerals (kaolinite, illite/smectite, and chlorite). The enrichment of critical metals within the Heshan Formation is closely related to terrigenous detrital materials from the Daxin paleocontinent, volcanic detrital materials induced by the Emeishan mantle plume and the Yuenan magmatic arc. The accumulation of Li-Ga-REY and other critical elements within the mineralized layers is the result of inputs from terrestrial and volcanic detrital sources, interactions between peatification and diagenesis stages, and occasionally the input of metal-enriched fluids. In the mineralized layers I, II, and III, the content of lithium oxide (Li₂O) surpasses the boundary grade, and the levels of REY, Ga, and (Nb,Ta)₂O₅ are close to boundary grades, indicating promising exploration prospects. The Wanfu mine in the Xian’an Coalfield can be considered a primary target zone for the exploration and development of coal-associated critical metal resources in Guangxi. Full article