Search Results (114)

The long-term accumulation of phosphogypsum (PG) stacks has caused combined pollution of total phosphorus (TP), fluoride (F⁻), metals and metalloids (MMs), posing a severe threat to regional ecological security. To clarify the migration characteristics of pollutants in PG stacks, water leaching experiments and environmental risk assessment were conducted in 21 typical PG stacks in Southwest China. The spatial differentiation and vertical migration characteristics of pollutants under various coverage measures (high-density polyethylene (HDPE) film covering, soil covering, a composite of film–soil covering, and open-air storage) at different pH conditions were systematically analyzed. Results indicated that under open-air stockpiling conditions, the surface accumulation of TP and F⁻ was the most significant among all covering measures, corresponding to the highest environmental risk. In contrast, the membrane–soil composite covering exhibited the optimal inhibitory effect on the surface diffusion of TP and F⁻, but was less effective for metal and metalloid enrichment. Under acidic conditions (pH < 6), the vertical migration capacity of TP, F⁻, and MMs (Cu, Cd, Cr, Pb, and Zn) increased, leading to enrichment in the deep layers of the stack. With the increase in pH, the calcium-mediated precipitation–adsorption effect created a “geochemical barrier”, facilitating the solid-phase fixation of pollutants. A significant positive correlation among pollutants indicates synergistic release and fixation behaviors. In addition, a pH-controlled P-F-MM source-to-sink conceptual model was established, outlining the dissolution, precipitation, adsorption, fixation and re-enrichment pathway from fresh stock to leachate. This work provides insights for optimizing cover designs and pollution control strategies. Full article

The present work aims to investigate the microstructure and mechanical properties of laser beam spot welds in the superalloy Nimonic 80 A. Considering the importance of this innovative process in the manufacturing of engineering components for high-security industries, it is necessary to study the influence of the welding thermal cycle on the microstructure and mechanical properties of welded joints. The rapid heating/cooling, melting, and re-solidification phenomena that occur during welding modify the metallurgical characteristics of the weld compared with the microstructure of the base metal. Because the energy density is high and the process duration is very short, the microstructure obtained after solidification is fine dendritic in the central area of the joint and columnar in the weld–base metal transition zone. For the same reasons, the heat-affected zone (HAZ) is slightly extended. The increase in the size of the crystalline grains in the HAZ is negligible due to the low diffusivity of the nickel-based γ solid solution matrix, which inhibits the rapid migration of grain boundaries during the welding process. Metallographic analyses were performed using optical microscopy and scanning electron microscopy. The microhardness values, 152–168 HV0.05 in the weld and 180–190 HV0.05 in the base metal, together with the tensile–shear strength values (760–780 N/mm²) obtained at room temperature, demonstrate that the proposed welding process is appropriate and feasible for engineering applications involving Nimonic 80A superalloys. Full article

Zinc oxide (ZnO) and zinc sulfide (ZnS) nanocomposites represent promising multifunctional photocatalysts due to their complementary band structures and synergistic charge separation. ZnO–ZnS nanocomposites with varied ZnS content were synthesized to elucidate the composition–structure–property relationships governing their multifunctional performance. Structural characterization using XRD, SEM/EDS, Raman spectroscopy, and XPS confirmed the coexistence of wurtzite crystalline phases of ZnO and ZnS. SEM analysis revealed ZnS fine deposition on the ZnO surface. XPS measurements showed a gradual increase in the amount of ZnS on the ZnO surface with increasing sulfide content and a shift in the valence band maximum from 2.32 eV (pure ZnO) to 0.77 eV (pure ZnS). Optical measurements (IR, UV–Vis diffuse reflectance, photoluminescence) demonstrated that, despite the evolution of vibrational and luminescence features characteristic of ZnS, the apparent band gap remained nearly constant at 3.16–3.18 eV across the series. Photocatalytic methylene blue (MB) degradation followed pseudo-first-order kinetics, peaking for ZN_2 (1% ZnS, k_app = 103 × 10⁻³ min⁻¹), which is 1.7 times higher than for pure ZnO. This enhanced performance is consistent with an S-scheme-like heterojunction that facilitates electron migration to the ZnS conduction band while retaining ZnO valence band holes for oxidation. Scavenging experiments confirmed that electrons dominate MB degradation (k_app up to 185.1 × 10⁻³ min⁻¹ with EDTA/t-BuOH/Ar), outperforming hole-mediated pathways. Antibacterial assays against Staphylococcus aureus revealed good antimicrobial activity for all nanoparticles. The nanocomposite’s antibacterial activity was similar across all samples and was only slightly lower than that of pure ZnS and ZnO. Full article

Background: Osteosarcoma is the most common primary malignant bone tumor in children and adolescents. At present, multi-agent chemotherapy and surgery provide only limited effects and the prognosis for patients with recurrent or metastatic disease remains poor, with 5-year survival rates below 30%. These challenges highlight the need for innovative therapeutic approaches targeting osteosarcoma more effectively. Fenretinide, a synthetic derivative of all-trans retinoic acid, has shown significant antitumor activity in various cancers. In a recent high-throughput drug screening study, fenretinide emerged as the most active molecule against diffuse midline glioma over more than 3500 compounds. Fenretinide also demonstrated cytotoxic activity against osteosarcoma cell lines in vitro and in preclinical models and is endowed with a favorable safety and toxicity profile. However, its poor water solubility and limited bioavailability have hindered its clinical translation. To improve fenretinide bioavailability and enhance tumor exposure, different nanotechnology-based drug delivery systems have been proposed. Here we propose a tertiary complex made of fenretinide, bovine serum albumin, and hydroxypropyl-betacyclodextrin, indicated as BSAF. Methods: BSAF was evaluated for the main physico-chemical parameters such as hydrodynamic size, zeta potential, stability to drug leakage, and the biological effect on the osteosarcoma cell line MG63. Results: BSAF showed hydrodynamic size at the nanoscale, enhanced drug solubilization, high drug loading and size stability to dilution, characteristics that make this complex useful for targeted therapy. When tested on the MG63 osteosarcoma cell line, BSAF demonstrated significantly enhanced cytotoxicity, with half-maximal inhibitory concentration (IC₅₀) values ~50% lower than free fenretinide. The complex was more efficient than free fenretinide in inhibiting cell migration as demonstrated by wound healing assay. Live-cell imaging analyses revealed a cytostatic effect at sub-cytotoxic concentrations. Specifically, treatment with concentrations below the IC₅₀ resulted in significantly prolonged cell doubling time, decreased cell divisions, increased cellular sphericity and thickness, and decreased cell area. These morphological changes are more consistent with cell cycle arrest rather than apoptosis. These findings were corroborated by stable dry mass measurements, an indication of a cytostatic state rather than progressive cell death. In addition, cell motility parameters (e.g., instantaneous velocity, track speed, and displacement) at the single-cell and population level were markedly reduced at sub-IC₅₀ concentrations, further supporting a cytostatic phenotype. Conclusions: Collectively, the new BSAF complex showed promise as a potential therapeutic agent for treating osteosarcoma cancer, due to the favorable physico-chemical characteristics and the cytotoxic/cytostatic effects on MG63 cells. BSAF effects may be therapeutically valuable, particularly in preventing tumor recurrence by suppressing the proliferative and migratory potential of residual drug-resistant clones. Unlike conventional anticancer agents that mainly rely on cell death, fenretinide, when complexed, demonstrates a dual capacity to induce both cytotoxic and cytostatic responses, depending on concentrations, potentially overcoming multiple resistance mechanisms that are generally associated with tumor exposure to drug sub-cytotoxic concentrations. Full article

This study investigated wetting body migration and blind area distribution variations under different height differences (Δh) using indoor experiments and numerical simulations. Results show that the Δh of the injection hole shifts the wetting body intersection backward. Due to the increase in Δh, the vertical migration of the wetting peak at the No. 1 liquid injection hole accelerates, and the horizontal migration tends to be stable, which indicates that the Δh promotes the vertical seepage by changing the hydraulic gradient, which is beneficial to accelerate the leaching process. The migration of the wetting peak presents the characteristics of ‘fast first and then slow’, and it is easy to form a blind area in the later stage of leaching. When Δh is 0 and 3 cm, the blind area is concentrated between the two holes in the upper part of the ore heap. When Δh increases to 5 and 7 cm, the blind area expands to the top of the No. 1 hole. The simulation results show that although the increase in Δh can accelerate the recovery of water pressure in the near-end injection hole, it will increase the difference in leaching efficiency between ‘near-end’: when Δh is small, the wetting body diffuses symmetrically and the blind area is easy to eliminate; the increase in Δh leads to the asymmetric migration of the wetting body, and the remote area faces a significant risk of a blind area due to a low water pressure and low concentration. Full article

As pore space serves as the primary migration pathway of radon in rock media, investigating the influences of pore structural characteristics on radon migration is essential. In this study, the rock pore structure was numerically reconstructed via the Quartet Structure Generation Set (QSGS) method, based on the characteristic parameters extracted from real rock pore models obtained from CT scanning. Quantitative comparison results indicate that the permeability and radon diffusion coefficient of the QSGS-reconstructed models are highly consistent with those of the CT-based model, which verifies the reliability and effectiveness of the QSGS method. A series of three-dimensional (3D) rock pore models with different porosities (η), distribution probabilities (Pd), and growth probabilities (G) were constructed using the QSGS method. The radon diffusion coefficient, tortuosity factor and permeability of these models under dry conditions were quantitatively determined. The relationship between the radon diffusion coefficient, water saturation and temperature was obtained using the tortuosity factor of the pore models and the unsaturated non-isothermal radon diffusion coefficient model. Furthermore, the relationship between the relative permeability of the air and water phases and water saturation was obtained by coupling the calculated permeability with the Brooks–Corey model. The results demonstrate that the η was positively correlated with both the radon diffusion coefficient and permeability, with a more pronounced positive correlation observed for permeability. Under low η conditions, Pd was positively correlated with both the radon diffusion coefficient and permeability; under medium-porosity conditions, Pd was positively correlated with the radon diffusion coefficient but negatively correlated with permeability; under high-porosity conditions, Pd exhibited no significant correlation with the radon diffusion coefficient, while it shows a negative correlation with permeability. G in the principal direction was positively correlated with the radon diffusion coefficient and permeability along the same direction, but negatively correlated with those along orthogonal directions. The radon diffusion coefficient was strongly negatively correlated with water saturation, and weakly positively correlated with temperature. With an increase in water saturation, the relative air permeability presented a nonlinear decrease characterized by a fast-then-slow trend, whereas the relative water permeability showed a nonlinear increase with a slow-then-fast pattern. Full article

Horizontal well air sparging (HAS) technology provides a promising approach for pollution remediation. In this study, a model experiment assessed the airflow distribution characteristics of HAS under varying air sparging (AS) pressure, tube burial depth, and groundwater flow conditions, while evaluating the retardation effects of HAS on dissolved groundwater contaminants. The results indicated that airflow velocity and diffusion range increased markedly with elevated AS pressure. Deeper AS tube burial depths resulted in more uniform airflow distribution and broader coverage. Groundwater flow significantly affected airflow distribution, as greater water head differences induced a downstream shift in the airflow pattern, resulting in an asymmetric diffusion range. Regarding pollutant retardation, airflow created a physical barrier by reducing permeability and interfacial resistance, effectively hindering pollutant diffusion. Airflow from the AS tube aligned parallel to the flow direction reduced Rhodamine B concentration by 53.1% over 300 min, preventing deeper pollutant migration into the sand layer. Conversely, airflow from the AS tube oriented perpendicular to the flow direction reduced Rhodamine B concentration by 84.38% over the same period, demonstrating superior effectiveness in limiting horizontal pollutant diffusion. These findings provide valuable theoretical insights and practical guidance for implementing HAS technology in groundwater pollution management. Full article

Supercritical CO₂ modifies deep coal reservoirs through the coupled effects of adsorption-induced deformation and geochemical dissolution. CO₂ adsorption causes coal matrix swelling and facilitates micro-fracture propagation, while CO₂–water reactions generate weakly acidic fluids that dissolve minerals such as calcite and kaolinite. These synergistic processes remove pore fillings, enlarge flow channels, and generate new dissolution pores, thereby increasing the total pore volume while making the pore–fracture network more heterogeneous and structurally complex. Such reservoir restructuring provides the intrinsic basis for CO₂ injectivity and subsequent CH₄ displacement. Both adsorption capacity and volumetric strain exhibit Langmuir-type growth characteristics, and permeability evolution follows a three-stage pattern—rapid decline, slow attenuation, and gradual rebound. A negative exponential relationship between permeability and volumetric strain reveals the competing roles of adsorption swelling, mineral dissolution, and stress redistribution. Swelling dominates early permeability reduction at low pressures, whereas fracture reactivation and dissolution progressively alleviate flow blockage at higher pressures, enabling partial permeability recovery. Injection pressure is identified as the key parameter governing CO₂ migration, permeability evolution, sweep efficiency, and the CO₂-ECBM enhancement effect. Higher pressures accelerate CO₂ adsorption, diffusion, and sweep expansion, strengthening competitive adsorption and improving methane recovery and CO₂ storage. However, excessively high pressures enlarge the permeability-reduction zone and may induce formation instability, while insufficient pressures restrict the effective sweep volume. An optimal injection-pressure window is therefore essential to balance injectivity, sweep performance, and long-term storage integrity. Importantly, the enhanced methane production and permanent CO₂ storage achieved in this study contribute directly to greenhouse gas reduction and improved sustainability of subsurface energy systems. The multi-field coupling insights also support the development of low-carbon, environmentally responsible CO₂-ECBM strategies aligned with global sustainable energy and climate-mitigation goals. The integrated experimental–numerical framework provides quantitative insight into the coupled adsorption–deformation–flow–geochemistry processes in deep coal seams. These findings form a scientific basis for designing safe and efficient CO₂-ECBM injection strategies and support future demonstration projects in heterogeneous deep coal reservoirs. Full article

Based on the two-dimensional reaction–diffusion model, the spatiotemporal dynamical characteristics of the semi-discrete pine–Monochamus alternatus system with cross-diffusion and convection effect were studied in this work. Firstly, the stability conditions of the equilibrium point were obtained through linear stability analysis and Lyapunov coefficients, as well as the Andronov–Hopf bifurcation, which explained the reason for the periodic outbursts of the Lyapunov population from a dynamic perspective. Subsequently, through the characteristic equations of the Laplace operator ${\mathrm{\nabla }}^2$ and the gradient operator ∇, the critical discrimination conditions for the occurrence of Turing instability in the system were obtained and revealed that the phenomenon of frequent damage to pine caused by the pink Monochamus is in the form of patches. Finally, the reliability of the theoretical analysis was verified through numerical simulation, and the dual effect of convection was clearly found in the system. Moderate convection can change the pattern shape, while strong convection produces a “washout effect”, completely inhibiting the formation of the pattern. This indicates that factors such as wind or the directional migration of Monochamus alternatus significantly affect the spatial distribution pattern of pests. Therefore, the theoretical research on Turing instability of models with convection terms may provide inspiration for subsequent studies. Full article

Li-Argyrodite-type Li₆PS₅Cl solid electrolyte is one of the most extensively investigated and promising materials in the field of all-solid-state batteries. However, its interfacial stability against lithium metal anodes remains challenging. Herein, first-principles calculations were employed to probe the effects of Zr and F co-doping on the interfacial structural characteristics of Li₆P_0.9Zr_0.1S_4.9F_0.1Cl solid electrolytes in contact with lithium metal at the atomic scale. Systematic investigations were conducted on interfacial structural stability, electronic structure, lithium-ion transport properties, and stress–strain properties. Theoretical results demonstrate that the formation energy of sulfur on the lithium metal side in the Zr and F co-doped interface is significantly increased, which stems from the strong bonding interactions of Zr–S and P-F bonds. This effectively suppresses sulfur diffusion toward the lithium metal anode, thereby enhancing the interfacial structural stability. Moreover, Zr and F co-doping simultaneously improves both the lithium-ion migration capability and mechanical stress–strain properties at the interface. The maximum strain at the Li/Li₆PS₅Cl interface increases substantially from 6% to 12% with the implementation of Zr/F co-doping. The Li⁺ migration barrier at the interface exhibits a reduction of 36%. The insights from this study can serve as a design guideline for engineering high-performance solid electrolytes for all-solid-state batteries. Full article

To ensure the safe operation of railway tunnels and prevent methane disasters in auxiliary tunnels, this paper focuses on the post-construction closure of an auxiliary tunnel (cross tunnel) in a railway tunnel with methane presence. Computational Fluid Dynamics (CFD) simulations were employed to investigate methane migration and accumulation patterns under different sealing conditions in railway auxiliary tunnels. The optimal auxiliary tunnel end-face closure method was identified. Subsequently, the influences of factors such as tunnel length and methane concentration on the explosion characteristics were analyzed under the optimal closed process conditions. The results show that after methane escapes from the coal seam, it initially accumulates at the tunnel’s roof and then diffuses downward due to the concentration gradient. When the lower end face of the auxiliary tunnel is opened and the upper end face is sealed, the degree of methane enrichment in the tunnel is the lowest and the enrichment speed is the slowest. Under partial methane conditions, the explosion pressure propagated and released more easily within the tunnel, leading to higher peak pressure. As the length of the tunnel increases, the peak pressure of the explosion increases, and the explosion power becomes greater. The overpressure of the explosion shock wave follows a nonlinear relationship with distance and is inversely proportional to the square root of the distance. The findings provide theoretical guidance for the prevention and control of methane-related accidents and disasters. Full article

Microplastic pollution in riverine ecosystems poses critical environmental challenges, yet current modeling approaches inadequately capture the spatial heterogeneity and topological complexity of fluvial systems. This study develops an innovative spatiotemporal graph convolutional network (ST-GCN) framework that integrates hydrological connectivity, flow parameters, and microplastic characteristics for simultaneous migration pathway identification and pollution source tracing. This model constructs multi-scale graph representations encoding system structure and transport dynamics, implements spatial-temporal convolution layers with adaptive attention mechanisms, and employs a backpropagation-based algorithm for inverse source identification. Validation using 18 months of field observations from 45 monitoring nodes across a 127 km river reach demonstrates 87.3% pathway prediction accuracy and 94.3% source localization accuracy (R² = 0.841, p < 0.001), representing substantial improvements over conventional advection–diffusion models. The framework successfully identified three pollution sources during a real contamination incident within 6 h of detection, enabling rapid regulatory intervention. This research advances environmental modeling by demonstrating that graph neural networks effectively capture transport processes in networked hydrological systems, providing practical tools for watershed management and evidence-based pollution control decision-making. Full article

Accumulation-type water vapor transport (hereafter referred to as AT-WVT) and permeation-type water vapor transport (hereafter referred to as PT-WVT) represent two fundamental modes of water vapor diffusion in asphalt mixtures, exerting distinct impacts on asphalt pavement durability. In this study, the diffusion characteristics of AT-WVT and PT-WVT within three core components of asphalt pavement systems—pure asphalt binder, aggregate matrix, and asphalt mixture void structures—were investigated. The corresponding diffusion coefficients for these three materials were determined through a synergistic approach combining laboratory experiments and theoretical modeling. Three typical asphalt materials (50# asphalt, 70# asphalt, SBS-modified asphalt) and two commonly used aggregates (limestone, diabase) were used. The results show that, for all three materials, the water vapor diffusion coefficient for the AT-WVT mechanism is relatively low, whereas the coefficient for the PT-WVT mechanism is approximately four orders of magnitude greater. The tortuosity factor of moisture diffusion paths in asphalt mixtures is substantially elevated during AT-WVT (tortuosity factor > 2000), as water vapor encounters frequent obstacles caused by the complex microstructural architecture (e.g., asphalt–aggregate interfaces and closed pores). In contrast, PT-WVT exhibits a much lower tortuosity factor (12–18), enabling rapid and direct migration through interconnected channels, such as capillary voids and microcracks. Due to its higher transport efficiency, PT-WVT poses a more critical threat to pavement durability by facilitating rapid moisture intrusion and subsequent damage (e.g., stripping, fatigue cracking). This study elucidates the mechanistic differences between AT-WVT and PT-WVT in asphalt binder, aggregate matrix, and asphalt mixtures, providing a foundation for optimizing asphalt mixture design to enhance long-term durability and performance under hygrothermal loading conditions. Full article

High-space industrial facilities often store substantial quantities of flammable volatile organic compounds (VOCs), posing significant fire and explosion hazards. This study employed computational fluid dynamics (CFD) to investigate the migration and diffusion characteristics of VOCs in a semi-enclosed, high-space wood chip fuel storage shed. A three-dimensional transient numerical model was developed based on a real-scale industrial prototype, incorporating the Realizable $k-\epsilon$ turbulence model with species transport equations. Validation using experimental data demonstrated good agreement between the model and experimental results, with a maximum relative error of 5.0%. A systematic assessment of key parameters was conducted, including time, ambient temperature, relative humidity, wood chip stack height, and VOCs type. Evaluation metrics comprised the surface-average mass fraction and the proportion of areas exceeding 5% of the lower explosive limit (LEL). The results show that peak concentrations occurred at 25~27 min. The system reaches quasi-steady state after 60 min. At 300~304 K, the lowest peak mass fractions are observed (0.31% and 0.43% at 19 m), yet the area exceeding 5% LEL was the largest. Moderate humidity (40~60%) reduces peaks by 0.06~0.11%. A stacking height of 7.5 m reduces peak values to 0.21% (left) and 0.28% (right), while a 10 m height increases the hazardous area to 48.87%. Low-polarity VOCs (C₁₀H₁₆) spread widely (34.10% exceeding 5% LEL area), whereas polar VOCs (C₁₅H₂₆O) accumulated locally (4.48%). These findings provide theoretical guidance for VOC hazard control and ventilation optimization in high-space biomass fuel storage facilities. Full article

This study examined the effects of hot-air drying (HAD), infrared drying (IRD), and microwave-infrared combined drying (MICD) on the drying characteristics and quality of citrus peels. Increasing temperature and microwave power significantly shortened drying time, with MICD showing the highest efficiency due to its volumetric heating mechanism. MICD also exhibited the highest effective moisture diffusivity and lowest activation energy, indicating enhanced moisture migration, but caused structural collapse and color deterioration. In contrast, HAD and IRD better preserved color and oil gland integrity. Under optimal conditions, MICD and IRD retained higher total phenolic and flavonoid contents, accompanied by superior antioxidant activity. Electronic nose and PCA analyses revealed better volatile flavor retention in HAD and IRD, while microstructural observations showed that IRD produced more uniform and intact tissues. Correlation analysis indicated strong associations among color, flavor retention, and antioxidant activity. The entropy-weight comprehensive evaluation identified IRD at 70 °C as the optimal drying method, balancing efficiency, bioactive compound preservation, and flavor quality. These findings provide practical guidance for selecting energy-efficient drying technologies to enhance the quality of dried citrus peels. Full article