Search Results (1,088)

Anthropogenic climate change has disrupted the global hydrological cycle, increasing compound extreme events like Dry–Wet Abrupt Alternations (DWAAs). Regarding the Mediterranean Basin, Greece is highly susceptible to these abrupt hydroclimatic shifts, which frequently overwhelm reactive disaster management. This study quantifies the spatiotemporal dynamics of DWAA events across Greece from 1990 to 2024. Using the 1-month Standardized Precipitation Evapotranspiration Index (SPEI-1) from ERA5 reanalysis, transitions were classified into dry-to-wet (DW) and wet-to-dry (WD) across moderate (±1.0), severe (±1.5), and extreme (±2.0) thresholds. Core physical metrics (duration, severity, and intensity) were evaluated using Anselin Local Moran’s I (LISA) and Mann–Kendall tests to identify spatial hotspots and temporal trends. Results revealed a spatially decoupled hazard regime dictated by topography and atmospheric mechanics. Severe DW transitions primarily manifest as intense autumn flash floods (62.7%) concentrated in western and southern districts. Conversely, severe WD transitions emerge as high-magnitude summer agricultural flash droughts (52.5%) clustered in central and northern continental plains. Crucially, while the magnitudes of these events demonstrate historical temporal stationarity, their decadal frequency doubled in the 2020s. This increase validates the idea that global warming accelerates systemic climate extremes, necessitating an urgent shift toward proactive, highly localized adaptation strategies. Full article

Rice is a globally important staple crop and a major dietary source of inorganic arsenic (As). Compared with upland crops, flooded rice cultivation profoundly alters soil redox conditions, making paddy soils one of the most active agricultural interfaces for As mobilization, transformation, and food-chain transfer. While previous research has primarily focused on total As and inorganic As [As(III)/As(V)], methylated and thiolated As species also carry critical agronomic and health implications. Dimethylarsinic acid (DMA) can accumulate in grain and induce straighthead disease, whereas dimethylmonothioarsenate (DMMTA) shows substantially higher toxicity and uptake potential; DMMTA root uptake can be approximately 10 times higher than DMA, and its straighthead-inducing potency can exceed DMA by more than fivefold. This review synthesizes the sources, biogeochemical transformations, plant uptake, grain accumulation, safety assessment, and management implications of As along the paddy soil–rice–grain continuum. Particular emphasis is placed on how water regimes, redox potential, Fe/Mn/Al oxides, sulfur cycling, dissolved organic matter (DOM), microbial functional genes, and crop genotypes regulate diverse As species. Quantitative evidence indicates that alternate wetting and drying (AWD) can reduce grain total As and inorganic As by medians of 32% and 22%, respectively, but may increase grain cadmium (Cd) by a median of 58%; meanwhile, DMA and DMMTA can account for approximately 10–90% and 1–21% of total grain As, respectively, emphasizing that grain-As risk cannot be evaluated using inorganic As alone. Future research should establish speciation-based monitoring systems for inorganic, methylated, and thiolated As; develop process models linking water regime, Fe/S cycling, microbial transformations, and plant transport; and translate these mechanisms into field decision tools that balance As–Cd risk reduction, crop yield, and rice safety under changing environmental conditions. Full article

Red mud-based backfill containing circulating fluidized bed (CFB) ash and reactive MgO must maintain adequate mechanical integrity and environmental stability under moisture and alkaline exposure. This study investigated the durability of carbonation-solidified red mud-based backfill subjected to wetting–drying cycles and alkaline red mud liquor (RML) immersion. Specimens carbonated for 0, 2, 4, 6, 8, and 10 h were evaluated in terms of macroscopic morphology, mass loss, linear shrinkage, unconfined compressive strength (UCS), electrical resistivity, pH, hazardous-element leaching, scanning electron microscopy, and X-ray diffraction. Increasing carbonation duration generally reduced mass loss and linear shrinkage while improving UCS and electrical resistivity within the investigated exposure range. Wetting–drying cycling resulted in progressive surface erosion, shrinkage, and strength deterioration. By contrast, RML immersion produced an initial increase in UCS and resistivity, followed by stabilization or a slight decline at later ages. The observed changes were consistent with pore filling by carbonate-bearing products and low-crystallinity reaction products, followed by local pore development and disruption of the cemented structure during prolonged exposure. At a UCS threshold of 0.8 MPa, the response-surface models yielded estimated threshold exposures of 6.92–13.98 cycles under wetting–drying conditions and 45.69–75.05 d under RML immersion, with the RML estimates extrapolated from the 28 d dataset. Within the tested conditions, carbonation improved the resistance of the backfill material to cyclic moisture disturbance and alkaline immersion, with the 8–10 h groups retaining relatively higher mechanical and dimensional performance. Full article

During the operation of large reservoirs, slope rock masses at different elevations are subjected to confining pressure variation and alternating wet–dry cycles induced by water-level fluctuations, resulting in the evolution of their mechanical properties. To investigate this issue, conventional triaxial compression tests were conducted on limestone from Badong County in the Three Gorges Reservoir area under confining pressures of 5–20 MPa and 0–50 wet–dry cycles. The results show that confining pressure significantly enhances limestone strength, whereas wet–dry cycles induce a progressive deterioration in mechanical properties. Under the same confining pressure, the deterioration exhibits a staged characteristic, with a rapid decrease at the early stage followed by a slower decline. Higher confining pressure effectively suppresses crack propagation and mitigates the degradation caused by wet–dry cycling. Meanwhile, wet–dry cycles promote the transition of the failure mode from single-fracture failure to multi-fracture fragmentation. The elastic modulus, cohesion, and internal friction angle all decrease exponentially with increasing wet–dry cycles. Based on damage mechanics theory, a constitutive relationship considering wet–dry cycle effects was established to characterize rock stiffness degradation and its influence on the overall mechanical response. The proposed model effectively describes the evolution of mechanical parameters and deformation characteristics under wet–dry cycling conditions. This study provides an experimental and theoretical basis for evaluating the long-term stability of reservoir slopes. Full article

Geomembranes are widely used in water storage ponds and irrigation systems in arid and semi-arid regions. The residual damage of geomembranes will lead to soil pore blockage, water infiltration obstruction, and soil degradation. This study investigated the effects of geomembrane residues at different depths on soil under drought and rainfall conditions. Using a ZHS multifunctional climate chamber to simulate dry–wet cycles, the effects of residual geomembranes on soil evaporation and cracking processes were investigated, along with their impacts on soil aggregates and aggregate-associated organic carbon. Results showed that with increasing residual geomembrane content, the Mean Weight Diameter (MWD) of aggregates decreased by 3.95%, 28.25%, and 51.41%, and the Geometric Mean Diameter (GMD) decreased by 10.59%, 42.35%, and 61.18%, respectively, compared to the residual geomembrane-free treatment. Organic carbon content in all aggregate size fractions consistently declined. Under the same dry–wet cycling conditions and soil thickness, residual moisture content decreased with higher residual geomembrane addition. Meanwhile, residual geomembrane enrichment promoted soil cracking, as evidenced by increased crack ratio and fractal dimension, and the initial evaporation rate increased with increasing residual geomembrane content. Compared to the control group, residual geomembrane significantly reduced residual moisture content, reducing it by 4.48–29.37%, 7.14–21.92%, and 4.19–35.95%, respectively. The final crack ratio increased by 5.33–58.89%, 0.97–63.39%, and 0.87–72.46%, respectively. Meanwhile, the final fractal dimensions increased by 0.50–15.26%, 2.92–15.96%, and 3.22–13.33%, respectively. Mechanistically, residual geomembrane fragments occupy soil pores and reduce interparticle cohesion, thereby promoting the expansion of crack ratios and disrupting aggregate stability, which accelerates organic carbon decomposition. This study provides scientific insights into how residual geomembranes affect soil ecosystems and supports agricultural soil conservation and management. Full article

Cement-based grouting materials may suffer strength loss and impermeability degradation when exposed to oil- and gas-bearing corrosive environments. In this study, 7.0% waterborne epoxy resin was used as a polymer admixture to improve the durability of cement-based grout under coupled corrosive exposure. Actual corrosive fluid from an engineering site and accelerated dry–wet cycling were used to simulate the service environment. The evolution of mechanical properties, impermeability, and dominant microstructural damage was then examined. The results show that the unmodified grout deteriorated markedly during cyclic exposure. After 120 cycles, its compressive strength decreased from 37.4 MPa to 26.2 MPa, the elastic modulus decreased by 44.1%, and the impermeability pressure dropped from 0.9 MPa to 0.3 MPa. By contrast, the grout containing 7.0% waterborne epoxy resin showed better durability. The strength and modulus losses were limited to 17.4% and 21.0%, respectively, and the impermeability pressure remained at 0.6 MPa, about twice that of the unmodified grout. Microscopic results indicate that dry–wet alternation promoted aggressive ingress and crack growth. The epoxy phase formed a relatively continuous film in the matrix, reduced penetration pathways, and slowed internal damage development. Based on the observed damage evolution, a mechanical prediction model and a new impermeability grading method were established. These findings show the potential of polymer admixture modification for improving the long-term performance of cement-based grouting materials in aggressive environments. Full article

External corrosion of buried ferrous water mains remains the dominant driver of structural failure in aging water distribution networks, yet the mechanisms linking soil physical and chemical heterogeneity to corrosion kinetics and product phase evolution have not previously been synthesized into a unified critical framework. This review evaluates three partially competing accounts of electrochemical degradation—anodic dissolution coupled to oxygen reduction within porous rust layers, redox cycling of iron oxide phases driven by seasonal soil moisture fluctuations, and microbially influenced corrosion (MIC) mediated by direct extracellular electron transfer (EMIC) and chemical metabolite pathways (M-MIC)—and assesses the weight of evidence for each. We demonstrate that corrosion products retain electrochemical activity long after formation, functioning as dynamic redox mediators that continue the reactions responsible for their own growth: the reduction of lepidocrocite under anoxic conditions regenerates Fe²⁺ ions that sustain anodic dissolution and catalyze oxygen reduction, while repeated soil moisture cycles drive the irreversible transformation of γ-FeOOH to Fe₃O₄, which fundamentally alters the conductivity and cathodic capacity of the rust layer. The widely cited universal critical-moisture threshold of 65% water-holding capacity (WHC) is evaluated and found to be a single-point approximation contradicted by texture-resolved experimental data that show the critical degree of saturation ranges from S_r ≈ 0.5 in sand to S_r ≈ 0.8 in clay. Modern machine learning analyses of field corrosion databases confirm that chloride content, pH, pipe-to-soil potential, and water content are the four highest-ranked predictors of maximum pit depth, consistent with the mechanistic framework developed here. The classical cathodic depolarization model of SRB-driven corrosion is evaluated against EMIC evidence and found insufficient: measured pure-culture SRB corrosion current densities range from 14 to 135 µA cm⁻², not the milliampere-level values reported in some earlier reviews. An explicit research agenda is proposed to address the five most consequential unresolved mechanistic questions. Full article

As tangible witnesses and cultural carriers of the evolution of Chinese civilization, earthen heritage sites embody outstanding historical, cultural, and scientific value. However, due to the heterogeneity among sites and their long-term exposure to complex environmental and anthropogenic pressures, their conservation faces numerous challenges. This paper provides a comprehensive review of the deterioration mechanisms of earthen heritage sites in China induced by environmental and anthropogenic factors, with particular emphasis on the effects of individual factors, such as salt-induced erosion, wetting–drying cycles, wind erosion, microbial activity, freeze–thaw cycles, and human activities, as well as the coupled actions of multiple factors. It further summarizes recent progress in protective technologies developed in response to these mechanisms, as well as integrated conservation strategies for coping with coupled deterioration effects. In recent years, the intrinsic linkage mechanisms between external environmental conditions and the engineering performance of earthen heritage sites have become a research focus. This review aims to deepen the understanding of environmental degradation processes in earthen heritage sites and to provide theoretical and technical support for the scientific formulation of targeted preventive conservation, repair, and strengthening measures. Full article

External sulfate attack constitutes a major durability challenge for structural concrete, yet the influence of mechanical loads on sulfate transport remains incompletely understood. This study develops a coupled sulfate–water transport model that embeds the effects of axial static loads and fatigue loads into the effective sulfate diffusion coefficient through physically motivated correction factors, without explicitly resolving chemical reactions or physical crystallization. Numerical simulations were performed for coupled scenarios of static loading, fatigue loading, and drying–wetting cycles. Three principal findings emerge. First, drying–wetting cycles produce a stable convection enrichment peak at 1 to 3 mm from the exposed surface, rather than a monotonic decay profile. Second, axial static loads exhibit pronounced tension–compression asymmetry: tensile stress enhances sulfate transport, while compressive stress exerts a comparatively weak inhibition effect. Third, fatigue loading introduces time-dependent accumulation and nonlinear acceleration driven by the dynamic evolution of microcrack connectivity. The tensile zone consistently exhibits markedly higher sulfate enrichment and deeper penetration than the compressive zone, identifying it as the dominant region for coupled deterioration. These findings provide a quantitative foundation for durability assessment of concrete structures under complex loading environments. Full article

Bentonite slurry (BS) and steel slag powder (SS) were co-utilized to develop bentonite-slurry/steel-slag foamed concrete (BS-SSFC). The evolution of compressive strength and the associated deterioration mechanisms were examined after repeated wetting–drying exposure in four environments, namely H₂O, H₂SO₄, NaOH, and Na₂SO₄, by combining mechanical testing with microstructural observations. The mix-design results indicate that, for the SS-only mixtures, 20% SS replacement produced a relatively high strength, whereas the binary SS-BS system reached its maximum strength at 10% SS and 5% BS; this combination was consequently adopted for the durability experiments. After 20 cycles, the severity of degradation followed Na₂SO₄ > H₂SO₄ > NaOH > H₂O. XRD and SEM-EDS evidence shows that sulfate ions in the H₂SO₄ and Na₂SO₄ solutions favored ettringite-type expansive products, and Na₂SO₄ further caused salt-crystallization pressure during drying. For NaOH exposure, the main damage was related to reduced stability of cementitious phases together with ion redistribution and localized re-precipitation in a strongly alkaline pore environment. Based on fractal theory, an empirical strength–degradation correlation model was established by using SEM-derived two-dimensional apparent areal porosity as a structural parameter and by linking fractal dimension with the number of cycles. Within the scope of the present experiments, the model captures the empirical link between strength loss and apparent pore-structure deterioration in BS-SSFC; however, its use remains dependent on the image-acquisition procedure, thresholding method, and material system considered. The results provide useful support for using BS-SSFC in aggressive engineering settings such as saline ground and acid-rain regions. Full article

A bond interface between new and old concrete is inherently present in bridge widening and rehabilitation projects. Under marine environmental conditions, this interface provides a preferential pathway for chloride ion transport, thereby accelerating chloride-induced corrosion of the bridge structure. Although the mechanical bonding performance of such interfaces has been extensively investigated, the durability of new-to-old concrete systems remains significantly inferior to that of monolithic concrete, particularly in terms of resistance to chloride penetration. In this study, chloride erosion tests on new-to-old concrete specimens were conducted under drying–wetting cycle conditions to investigate the influence of the bond interface on the spatial distribution and temporal evolution of chloride concentration. The results indicate that the chloride concentration at the bond interface is significantly higher than that in other regions. This leads to a dual transport mechanism, where chloride ions not only diffuse inward perpendicular to the exposed surface but also migrate laterally from the interface into the adjacent concrete driven by concentration gradients. Based on these findings, an interface influence coefficient is proposed to quantify the effect of the bond interface on chloride transport capacity. This coefficient exhibits a strong fit with the GaussAmp function. Furthermore, a diffusion coefficient model for new-to-old concrete incorporating the effect of the bond interface is established. Full article

Lithium-ion batteries are widely used in digital, power and energy storage fields due to their high capacity and high cycle life advantages. This paper systematically screens the formulation system and designs a high-efficiency production line that can effectively improve production efficiency, reduce production costs, and lower energy consumption per unit product. The produced nano-silicon-enhanced graphite anode material has excellent performance. The selection of silicon raw materials, types of solvents, types of dispersants, and grinding processes is studied to investigate the influence of these four factors on the wet grinding process for preparing nano-silicon. Finally, metal silicon obtained by air flow pulverization is selected as the raw material, isopropanol is used as the solvent, FA01 (carboxylic acid type) is used as the dispersant, and a two-stage wet grinding process is adopted to prepare the nano-silicon dispersion solution. Zirconia beads of 0.5 mm and 0.2 mm size are used as the grinding media for the first and second stages, respectively, with filling rates of 80% and 90%, respectively. The final prepared nano-silicon dispersion is stable in dispersion and has a narrow particle size distribution. The nano-silicon dispersion solution and the multi-walled carbon nanotube dispersion solution are mechanically ground and mixed using a sand mill. At the same time, the multi-walled carbon nanotubes are coated with the nano-silicon. Then, artificial graphite is added for compounding. Finally, through spray drying, the Si@MWCNTs@graphite (SMG) nano-silicon-enhanced graphite negative electrode material is prepared. The SMG nano-silicon-enhanced graphite negative electrode material with a silicon content of 2% has a first Coulomb efficiency of up to 84.32%. Full article

Previous characterisation of historic blue bricks (qingzhuan) from Beijing identified compositional and physical differences across periods, but their effect on early-stage freeze–thaw behaviour was untested. An adapted laboratory wetting–freezing–thawing procedure was applied to four Ming-attributed and four Qing-attributed Great Wall bricks from the Miyun section as the primary cohort, with Lingyue Temple and Guanyin Chanlin bricks as supporting cases. The 10-cycle endpoint is below the 15 cycles GB/T 2542-2012 prescribes for a frost-resistance rating, so the results index early-stage damage sensitivity, not freeze–thaw durability. Dry mass loss, colour difference (ΔE*_ab), gloss change and visible damage were evaluated. The lower-density, higher-absorption (Ming-attributed) group lost 1.22 ± 0.84% of its dry mass versus 0.37 ± 0.12% for the denser, lower-absorption (Qing-attributed) group, with complete rank separation that persists after normalising by estimated coupon surface area. At four bricks per group, the exact Mann–Whitney result (U = 16, p = 0.029) sits at the smallest attainable p-value, so the comparison is exploratory and hypothesis-generating and establishes no dynastic difference in frost resistance. Bulk properties predicted neither damage magnitude nor mode: a low-mass-loss coupon fractured through, and the metrics ranked specimens differently. Conservation assessment should report material loss, structural integrity and surface preservation as separate endpoints, and match repair material by water absorption, pore structure and freeze–thaw behaviour rather than colour and composition alone. Full article

The degradation of the natural fibers in the hydraulic binder alkaline matrix is widely known. This study investigates the effect of two fiber treatments, namely immersion in sodium hydroxide (NaOH) solution and hornification, in two types of alkaline environmental ordinary Portland cement (OPC) and a mixture of OPC and natural hydraulic lime (NHL). After curing for 28 days, the specimens were subjected to 25 and 50 dry–wet aging cycles to evaluate their degradation behavior. Subsequently, the specimens underwent flexural and compressive strength tests. This study reveals that the specimens with the mixed binder of ordinary Portland cement (OPC) and natural hydraulic lime (NHL), after 50 aging cycles, reached toughness values in the descending branch compared to the total toughness obtained in the flexural–displacement diagram, of 17% and 27% for the treatment with NaOH and hornification fiber, compared to 3% and 10% obtained for the matrix with an OPC binder. Therefore, the inclusion of NHL as a matrix binder provided better softening behavior than those with only the OPC binder, providing better protection of the fibers against environmental alkalinity due to matrix alkalinity. In addition, the hornification treatment better preserved the fibers throughout the aging process. Full article

The disposal of construction and demolition waste (CDW) and the rehabilitation of water-rich goafs present two pressing challenges in sustainable mining and geotechnical engineering. This study introduces a bio-carbonated reactive magnesia cement (RMC) technology to solidify CDW for goaf backfilling applications. A comprehensive experimental program was conducted to evaluate the mechanical properties, water stability, and durability of bio-carbonated RMC-solidified CDW under simulated water-rich goaf environments. The unconfined compressive strength (UCS) of the 16% RMC specimens reached 3.12 MPa after 28 days, which was approximately 21% higher than that of the 12% Portland cement (OPC) control. Under dynamic water erosion conditions of 1.0 m/s for 72 h, the 16% RMC specimens showed a mass loss rate of 2.68% and a strength retention rate of 84.2%, both of which were superior to those of the 12% OPC control. The water–land strength ratio of the 16% RMC specimens reached 0.90 after 28 days of immersion, and the strength retention rate remained at 73.1% after 12 wet–dry cycles. Compared to the OPC control, these two indicators respectively represent a precise increase of 25% and approximately 60%. Microstructural analysis revealed that hydrated magnesium carbonates (HMCs), including nesquehonite and hydromagnesite, formed a dense spatial network that binds CDW particles and blocks pore channels. Additionally, a random forest model quantified the relative importance of RMC content, curing age, and carbonation degree on UCS, confirming that RMC dosage and the extent of carbonation are the dominant controlling factors. The optimal RMC content was determined to be 16%, balancing performance and cost. This study demonstrates that bio-carbonated RMC-solidified CDW is a technically viable and low-carbon backfill material with substantial CO₂ sequestration potential for water-rich goafs. Full article