Search Results (867)

Soil particle size fractions (PSFs)—sand, silt, and clay—are fundamental determinants of soil hydrological behavior, nutrient retention, and erodibility, yet their spatial prediction remains challenging due to the compositional nature of the data, unquantified prediction uncertainty, and limited interpretability of machine learning models. This study develops an integrated compositional mapping framework incorporating multi-source Sentinel-1/2 and topographic covariates, coupling the isometric log-ratio (ILR) transformation with Quantile Regression Forests (QRFs), a Monte Carlo simulation (MCS)-based latent-to-physical space uncertainty propagation strategy, and a Wrapper-SHAP attribution method to jointly address these challenges. The framework was evaluated across regional croplands in the central Shandong mountain-hilly region of China, using an elevation-stratified spatial cross-validation. Validations achieved R² values of 0.72, 0.61, and 0.59 for sand, silt, and clay, respectively, and a global Aitchison distance of 0.34. Critically, the MCS error propagation strategy effectively compensated for the probability distribution shift introduced by non-linear ILR back-transformation. This ensured that all predicted compositions strictly satisfied compositional closure and the [0, 100%] constraint, while aligning the prediction interval coverage probability (PICP) of each fraction closely with the 90% nominal level. Wrapper-SHAP overcame direct attribution limitations in compositional models, revealing the predictive associations of these multi-source covariates: high remote sensing-derived Bare Soil Index (BSI) and Moisture Stress Index (MSI) values primarily exhibited strong predictive associations with sand enrichment, whereas their lower values, combined with elevated Normalized Difference Moisture Index (NDMI), Enhanced Vegetation Index (EVI), and anthropogenic indicators, favored silt and clay accumulation. The proposed framework provides a transferable methodological reference for remote sensing-integrated compositional soil mapping with reliable uncertainty estimates and interpretable driver identification at regional scales. Full article

Tight gas is a critical unconventional energy resource, yet the geological characteristics and accumulation processes of tight gas in China’s Songliao Basin remain poorly documented. This study aims to investigate the tight gas system in the Songliao Basin as a representative continental basin, with key objectives including evaluating source rock and reservoir properties via mineralogical and geochemical analyses, characterizing lithologies and pore types, determining the gas charging mechanism in tight media, and identifying the main controlling factors for accumulation. Geochemical results indicate that the Shahezi Formation contains medium to good mudstones and excellent coals. Reservoirs consist of tight sandstones and conglomerates deposited in fan delta and braided river delta systems, with pore spaces dominated by dissolution pores and microfractures, resulting in ultra-low porosity and permeability. Conventional buoyancy-driven migration is ineffective; instead, gas charging is driven by hydrocarbon generation expansion force, creating overpressure that expels pore water and forces gas into reservoirs through fault-sand conduits. Accumulation is controlled by continuous gas supply from thick, highly mature source rocks, dissolution-enhanced and fracture-dominated reservoir space, and sufficient source–reservoir pressure difference. This study elucidates tight gas characteristics and accumulation mechanisms in continental basins, providing data applicable to both continental and marine settings. Full article

Transitions within the syn-rift stage provide a key window for examining sediment-routing changes and associated sedimentary responses in lacustrine rift basins. In the Bohai Bay Basin, the interval from the third member (Es3) to the second member (Es2) of the Eocene Shahejie Formation records a transition from early strong rifting toward relatively stable rifting. The Qinan Sag, a secondary sag along the Qikou Sag margin, was sensitive to this transition. Using cores, well logs, three-dimensional (3D) seismic data, and heavy-mineral data, this study reconstructs the source configuration, palaeogeomorphology, depositional-system evolution, and Es3–Es2 source-related sediment-dispersal domains. The results show that the supply pattern shifted from coeval supply by a southern regional source and northern and western local sources during Es3 to southern regional-source dominance during Es2. Accordingly, Es3 contains strongly differentiated braided-delta, fan-delta, and subaqueous-fan assemblages. Es2 contains weakly differentiated shallow-water delta and beach-bar assemblages. Three source-related sediment-dispersal domains coexisted during Es3. During Es2, the northern domain was no longer identified, and the western gentle-slope belt evolved into a high-sand-ratio beach-bar belt. This reorganization was mainly controlled by the combined effects of source-configuration changes, geomorphic segmentation, and contrasting slope–A/S conditions (A/S = accommodation/sediment supply). Supply-pattern simplification and weakened geomorphic segmentation shifted sediment routing after basin entry from multiple, dispersed pathways to dominant-source-controlled focused routing. Moderate-to-steep slopes and higher relative A/S proxy values during Es3 favoured discrete, segmented sandy-deposit preservation; gentle slopes and lower relative A/S proxy values during Es2 promoted focused routing and preservation of sandy deposits along the dominant direction, with local shallow-water enrichment. Across the Es3–Es2 syn-rift stage transition, regional-source-related sediment routing showed stronger persistence; local-source-related routing more often weakened or terminated, with corresponding areas tending to show shallow-water redistribution and enrichment signals. Full article

Understanding the variation law and prediction method of thermal conductivity for NaCl-bearing aeolian sand is of great significance for the thermal parameter selection and temperature field analysis of engineering structures including subgrades, foundations and lined water conveyance canals in the saline soil region of southern Xinjiang. The thermal conductivity of NaCl-bearing aeolian sand under different dry densities, moisture contents and salt contents was measured via the transient plane source (TPS) method. The variation law and corresponding influence mechanism were analyzed, and a thermal conductivity prediction model was established. The experimental results indicate that the thermal conductivity of NaCl-bearing aeolian sand increases with increasing dry density and moisture content, showing strong linear correlations with both parameters. At a salt content of 2%, the maximum increase in thermal conductivity induced by increasing moisture content reached 29.3%, which was approximately 1.53 times the increase observed at a salt content of 8% (19.17%). In contrast, the influence of salt content on thermal conductivity exhibited a nonlinear trend. With increasing salt content, the thermal conductivity initially decreased and then increased, and the salt content corresponding to the minimum thermal conductivity shifted toward higher values with increasing moisture content. Specifically, this critical salt content gradually shifted from 2% to 6%. This law reveals that the increase in dry density and moisture content improves the thermal conductivity of the soil mainly by enhancing the solid and liquid heat transfer pathways, whereas the variation of salt content is controlled by the water–salt coupling effect. The model calculation results show that the established prediction model is in good agreement with the measured experimental data (R² = 0.9674), with favorable applicability and high prediction accuracy. It can provide a reliable reference for the thermal calculation of sandy foundations and related engineering materials in saline soil areas. Full article

Inaccurate prediction of shrinkage in self-compacting concrete (SCC) may result in underestimated cracking risk, increased permeability, serviceability deterioration, and reduced long-term durability of concrete structures. Although conventional empirical shrinkage models are widely used in engineering practice, their accuracy is often limited when applied to SCC mixtures with high paste volume, mineral admixtures, manufactured sand, and high-range water-reducing admixtures. Recent machine-learning-based models provide an alternative approach, but single learning algorithms may show limited robustness for small and heterogeneous datasets. In addition, random sample-level data splitting may introduce information leakage when shrinkage measurements obtained at different curing ages from the same mixture are assigned to both training and testing sets. To address these issues, this study develops a stacking-based ensemble learning framework for SCC shrinkage prediction using mixture proportions and curing age as input variables. A multi-source database containing 61 mixture designs and 448 data samples was established from published experimental studies. To obtain a more realistic assessment of model generalization, a mixture-level validation strategy was adopted, in which all age-dependent samples from the same mixture were assigned exclusively to either the training set or the testing set. Under this strategy, 358 data samples were used for model training and 90 data samples were used for independent testing. Four base learners, including multilayer perceptron (MLP), support vector regression (SVR), decision tree (DT), and gradient boosting decision tree (GBDT), were constructed and integrated through different ensemble configurations. The Stacking-SVR model achieved the best overall performance on the independent testing set, with a mean absolute error (MAE) of 13.6 με and a mean absolute percentage error (MAPE) of 7.5%. Compared with GBDT, Stacking-GBDT, and DT models, the proposed Stacking-SVR model reduced the MAPE by approximately 10.7%, 11.8%, and 35.3%, respectively. Stability and applicability analyses further indicate that the proposed framework can provide reliable shrinkage predictions within the investigated mixture and curing-age ranges. However, because the model was developed from a compiled database and does not explicitly include environmental variables such as relative humidity and temperature, its use should be limited to parameter ranges represented in the database. Overall, the results demonstrate that stacking ensemble learning combined with mixture-level validation offers a leakage-controlled and engineering-oriented approach for SCC shrinkage prediction. Full article

Safe drinking water production from compositionally variable surface sources requires treatment systems that combine effective contaminant removal with stable membrane operation. This study experimentally evaluated a hybrid treatment train consisting of slow sand or zeolite pretreatment followed by NF for surface water representative of South-East Kazakhstan. The results showed that pretreatment reduced turbidity, iron, and organic load before the membrane stage, thereby improving flux stability and decreasing fouling propensity. Among the tested pretreatment options, zeolite provided the most favorable feed conditions and extended stable membrane operation. These findings demonstrate that the practical performance of NF depends not only on membrane properties but also on effective upstream conditioning of the feed stream. Under the tested recovery conditions, the selected operating regime produced permeate of acceptable final quality, confirming that hybrid pretreatment–NF systems are a robust option for drinking-water treatment from challenging surface sources. Full article

This study focuses on optimizing backfill materials to enhance the heat transfer performance of ground heat exchangers (GHEs) in ground source heat pump (GSHP) systems. A series of composite phase change material/original sand soil (CPCM/OSS) backfill materials was prepared using capric acid–myristic acid/expanded graphite (CA-MA/EG) at mass ratios of 5%, 10%, 15%, and 20%. Thermal conductivity testing, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), laboratory heat transfer tests, and 3D numerical simulations under typical intermittent summer conditions were systematically conducted. The results show that thermal conductivity, specific heat capacity, and thermal storage coefficient all increase with rising moisture content and CPCM dosage. The newly developed CPCM/OSS backfill material significantly improves the heat transfer performance of GHEs. Comprehensive thermophysical characterization indicates that the 10 wt% CPCM sample is the optimal formulation. Laboratory tests demonstrate that, relative to pure OSS backfill, the 10 wt% CPCM-doped CPCM/OSS raises the average soil temperature by approximately 2.5–2.8 °C. Numerical simulations over three consecutive days show that, relative to pure OSS backfill, the 10 wt% CPCM-doped composite enhances the heat exchange capacity per linear meter of the GHEs by 8.8%. The newly developed CPCM/OSS backfill material significantly improves the heat transfer performance of GHEs. It provides a feasible material solution and technical reference for GSHP system design. Full article

Enzyme-Induced Carbonate Precipitation (EICP) represents a sustainable advancement in geotechnical engineering for stabilizing fine-grained soils (e.g., silt). Utilizing plant-derived urease (~12 nm) to catalyze urea hydrolysis, this technique generates calcium carbonate (CaCO₃) for soil reinforcement. Unlike Microbially Induced Carbonate Precipitation (MICP), EICP overcomes microbial size constraints (0.5–3 µm) by penetrating soil micropores, enabling uniform cementation. Its innovative single-phase low-pH method achieves >98% calcium conversion efficiency, yielding 6.41 MPa unconfined compressive strength (UCS) in sand—a 92.97% improvement over MICP. EICP demonstrates versatility: enhancing soil strength (up to 650% for silt), erosion resistance (wind erosion modulus increased ~20-fold), anti-seepage performance (permeability reduced from 10⁻⁶ to <10⁻⁹ cm/s), and heavy metal immobilization (>99%). However, challenges include unstable crystal morphologies (e.g., excessive vaterite), urease stability/cost constraints, and environmental concerns related to NH₃ emissions from urea hydrolysis. The manuscript acknowledges these emissions’ impacts and introduces mitigation strategies: ammonia capture technologies, optimized dosing protocols, and exploration of alternative N-sources. Long-term durability data under complex field conditions remain insufficient. Ongoing research addresses these gaps through nucleating agents (dried skim milk, biochar), enzyme immobilization, process optimization, and byproduct treatment. As a low-carbon technology with targeted mitigation measures, EICP advances environmentally conscious soil stabilization practices. This study presents a comparative narrative analysis of EICP’s performance and challenges, integrating laboratory findings and field applications. Full article

Waste materials are abundant and often act as slow environmental contaminants, creating severe ecological challenges. With rapid industrialization, electricity demand has increased substantially, and in India, coal-based thermal power plants (TPPs) remain the dominant source of power generation. Coal combustion produces two major by-products: fly ash and bottom ash (BA). While fly ash is widely utilized in blended cements due to its pozzolanic nature, BA has received comparatively limited attention despite having similar chemical characteristics. Owing to its coarser particle size, BA shows strong potential as a substitute for natural river sand, the excessive extraction of which has led to severe resource depletion and sustainability concerns. Unlike previous studies that focused on single-source BA or limited performance evaluation, this study investigates the use of BA from multiple sources to develop resource-efficient bottom ash concrete (BAC). Concrete mixes containing 0%, 20%, 35%, and 50% BA as volumetric replacements of river sand were evaluated for their fresh, mechanical, durability, and microstructural properties. The results indicate that BA significantly influences concrete performance due to its porous structure. Among the investigated mixes, 35% river sand replacement with BA showed the most favorable performance for the specific materials and sources used in this study, achieving up to 17.46% higher compressive strength and up to 16.14% higher resistance to transport-related properties at 90 days. Microstructural analysis confirmed the formation of secondary C–S–H gel, which enhanced matrix densification. However, 50% replacement resulted in reduced performance. The findings demonstrate that BA can be effectively utilized in concrete at replacement levels of up to 35% as a sustainable substitute for river sand under the investigated material conditions. Full article

As a core and priority region of the Beijing-Tianjin Sandstorm Source Control Project, the mountainous area of northern Hebei plays a critical role in restraining desertification and ensuring the ecological security and sustainable development of the capital region. To reveal the ecosystem service flow mechanism of windbreak and sand fixation and support regional ecological sustainability, this study first used the Revised Wind Erosion Equation (RWEQ) to evaluate the spatial distribution of windbreak and sand-fixation services in northern Hebei mountainous area. Then, the HYSPLIT model was applied to simulate the spatial flow paths, identify the radiation scope, and quantify the radiation intensity of these ecosystem services. The results reflect the modeled patterns under given assumptions rather than fully verified actual ecosystem service supply. In 2024, the total amount of windbreak and sand-fixation service in the study area reached 10.3553 × 10⁶ tons. Sand-dust weather mainly occurred in spring and autumn, accounting for 39.23% and 33.46% of the total, respectively. The spatial flow paths were dominated by the northwest pathway (43.01%) and west pathway (38.17%). The total radiation scope of windbreak and sand-fixation services was 396.16 × 10⁴ km², among which 342.96 × 10⁴ km² was within the study area, accounting for 86.57%. The average service density was 21.06 kg/hm². The service density along flow paths decreased with increasing transport distance, while the radiation scope expanded with the increase in trajectory frequency. Spatially, the sand-fixation material density showed a circular decreasing trend from the center to the periphery of the study area. This study clarifies the flow characteristics and radiation benefits of windbreak and sand-fixation ecosystem services, which can provide a scientific basis for regional ecological protection, ecosystem service management, and the promotion of regional ecological sustainability. Full article

Methane generation from anaerobic biodegradation of fugitive diluent hydrocarbons is an important source of greenhouse gas emissions from oil-sands tailings, yet predictive tools that preserve hydrocarbon-level information remain limited. This study develops a hydrocarbon-resolved methane-prediction model and tests it on a case study involving a twelve-component diluent mixture containing BTEX, normal alkanes, and iso-alkanes. The model integrates stoichiometric methane yields, compound-specific lag times, Monod-type hydrocarbon consumption, logistic activation, and a single methane-conversion factor to simulate cumulative methane production and group-level methane contributions through time. Model performance is evaluated against measured methane and residual hydrocarbon data using normalized mean square error. The model reproduces cumulative methane with improved normalized mean square error relative to the existing stoichiometric benchmarks, while group-resolved outputs and robustness analyses show that predictive performance is governed primarily by conversion efficiency and lag structure. On the other hand, inclusion of an unresolved biodegradable-substrate fraction did not strengthen model agreement. These results indicate that the modeled hydrocarbon set captures the principal methane-generating substrate pool and that the proposed framework provides an accurate and mechanistically interpretable basis for methane prediction in oil-sands tailings. Full article

On 6 June 1944, more than 156,000 Allied troops landed along the heavily fortified beaches of Normandy, France, during Operation Overlord, the largest amphibious assault in modern history. Intensive naval bombardment, ground combat, and subsequent occupation resulted in the introduction and emplacement of substantial quantities of anthropogenic metal into the coastal environment. Previous work has documented the presence of shrapnel and other metallic detritus within Normandy beach sands, with estimates suggesting ~1% of sediment may be derived from wartime activity; however, these observations were based on limited sampling. This study presents the first systematic, coast-wide investigation of sediment across all five Allied landing beaches (Utah, Omaha, Gold, Juno and Sword). A total of 460 surface and subsurface samples were collected in June 2024 and April 2025 and analyzed for metallic grain abundance, grain size, morphology and composition. Metallic grains comprise an average of 0.4 wt.% of the total sediment across the D-Day beaches. These grains are dominantly iron-rich based on geochemical characterization of a representative subset of samples (n = 33), with lower concentrations of aluminum, titanium and trace amounts of other metallic elements. These grains display a range of morphologies indicative of anthropogenic origin, including angular fragments and metallic spherules and rounded grains consistent with primary fragmentation and subsequent reworking. The combined evidence of morphology, magnetic properties, spatial distribution, and regional sediment compartmentalization supports a predominantly anthropogenic origin. Potential contributions from natural magnetite and industrial sources are considered but are unlikely to account for the observed patterns across all sites. Metallic grains are non-uniformly distributed and partitioned along the beach profile, with consistent enrichment within the swash zone relative to supratidal environments. Subsurface profiles show metallic grain persistence to depths exceeding 1 m, with peak concentrations consistently observed at 5–15 cm and 45–75 cm. These results demonstrate that the sedimentary record of Operation Overlord remains preserved within the modern Normandy coastline eighty years after emplacement. This anthropogenic material provides a temporally constrained stratigraphic tracer within a dynamic macrotidal system, offering insight into sediment redistribution, beach aggradation rates, and coastal processes operating on decadal timescales. Full article

The sustainable application of ultra-high-performance concrete (UHPC) is often constrained by high material costs and environmental footprints. While the individual effects of various industrial wastes have been extensively studied, the synergistic mechanism of multi-source waste in UHPC remains poorly understood. To fill the research gap, an eco-UHPC was developed wherein river sand (RS) was partially replaced by spontaneous combustion gangue sand (SCGS), and Portland cement (PC) was partially replaced by spontaneous combustion gangue (SCG) powder and phosphorous slag (PS). A systematic investigation was conducted to assess the packing density, flowability, mechanical properties, chloride ion penetration resistance, and micromorphology. The results indicate that 40% SCGS substitution (by mass) optimizes particle packing density and aggregate gradation, while PS incorporation significantly improves flowability by up to 16.83%. Notably, persistent pozzolanic reactions and the consumption of Ca(OH)₂ facilitate the generation of dense C-S-H gel, which creates a uniform microstructure and enhances late-stage compressive strength. Furthermore, superior chloride penetration resistance is achieved when the PS content is maintained below 20%. These findings support the synergistic utilization of SCGS, SCG, and PS in UHPC production, while facilitating broader application of UHPC through reduced costs and lower carbon emissions. Full article

Rapid urbanization has increased the demand for building materials, depleting natural resources used in cement production and prompting the use of alternative and waste materials. This research verifies that eggshell powder waste can fully replace limestone in clinker synthesis. Five clinkers were produced using eggshell powder, aluminum sources (bentonite, zeolite, fly ash, and kaolinitic–illitic clay), Fe-slag, and quartz sand, with mechanical preprocessing (10–30 min) before sintering at 1300 °C. Experimental tests assessed the effects of mix design and mechanical activation on clinkerization, phase formation, temperature, and mechanical properties. XRD, FTIR, and SEM/EDS confirmed consistent phase compositions and primary cement minerals. Aluminum source raw materials contributed significantly to tricalcium aluminate and tetracalcium aluminoferrite formation. Eggshell and fly ash promoted tricalcium silicate and dicalcium silicate synthesis, enhancing cement strength at early and late ages. Longer mechanical pretreatments hindered clinkerization. Eggshell-based cements untreated or pretreated for 10 min are suitable for structural concrete; 20–30 min pretreatment is appropriate for low-demand or non-structural applications. The proposed methodology reduces clinker manufacturing temperature by about 100 °C from the typical range of 1400–1450 °C while maintaining mechanical properties comparable to ordinary Portland cement. Full article

Climate change amplifies urban sustainability challenges, with intensifying sand and dust storm (SDS) hazards highlighting the important role of Ecosystem wind erosion prevention (EWEP) as an ecosystem service (ES). In northern China, a region prone to wind erosion, EWEP mitigates aeolian processes at sand sources and reduces downwind dust transport to urban centers. This study employs the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model to simulate diffusion dynamics of EWEP and to assess its hazard mitigation effects for cities in northern China. The findings are as follows: (1) EWEP capacity increased consistently from 2000 to 2024; (2) Aggregated preventive benefits rose, which aligns with the interpretation that systemic ecological restoration reduces dust dispersion; (3) Preventive benefits exhibit stratification across different urban agglomerations. These findings can inform SDS risk management and climate adaptation strategies to support urban sustainability. Full article