Search Results (162)

Suction anchors are widely used in offshore wind power foundations, where their penetration behavior critically influences installation efficiency and safety. Existing studies mainly focus on homogeneous soils, while the mechanisms of suction-assisted penetration in layered seabed remain less understood. This study establishes a numerical model based on the Material Point Method (MPM) to simulate suction anchor penetration in saturated soils, accounting for large deformations and hydro-mechanical coupling. The model is validated against physical tests, confirming the reliability of MPM. A series of simulations is conducted to examine penetration behavior under layered conditions, emphasizing the effects of stratigraphic sequence and configuration, including sand-over-clay (SC), clay-over-sand (CS), sand–clay–sand (SCS), and clay–sand–clay (CSC) profiles. The analysis reveals complex mechanical responses during penetration, including excess pore water pressure, soil displacement, effective stress, and penetration resistance. The results demonstrate that penetration behavior is governed by both the stratification sequence and the number of soil layers. Overall, this study clarifies the complex mechanical responses of suction caissons in layered soils, verifies the suitability of MPM for simulating large-deformation and hydro-mechanical coupling problems, and provides insights for the design and safe installation of suction caissons in stratified seabeds. Full article

In permanently submerged coastal wetlands, interactions between biogeochemical processes and microbial communities strongly influence greenhouse gas (GHG) fluxes. To improve our understanding of how redox-driven processes shape GHG dynamics in these ecosystems, we investigated the relationships among iron (Fe) pools, microbial dynamics, and the potential GHG production in subaqueous soils from an interdunal wetland in San Vitale Park (Italy), permanently submerged and affected by seasonal oscillations of the saline water table. Two subaqueous soil columns (WAS-2 and WAS-4), collected from similar settings, were analyzed. Surface layers of WAS-4 showed higher salinity and carbonate content, whereas WAS-2 was characterized by overall higher Fe concentrations. Distinct vertical distributions of organic matter and sulfur (S) were shown along depth. Laboratory incubations revealed that nitrous oxide (N₂O) production was up to ten times higher in WAS-2 than in WAS-4, with peaks in the top 13–14 cm, consistent with more active nitrification-denitrification in surface layers. Methane (CH₄) and carbon dioxide (CO₂) fluxes decreased with depth, reflecting reduced availability of labile carbon. Methanomicrobiales dominated CH₄-producing layers, indicating hydrogenotrophic methanogenesis, while amoA-carrying Nitrosomonadales and Thaumarchaeota, occurred in shallow, organic-rich layers where ammonia supported nitrification and denitrification. Denitrifiers mainly belonged to α- and β-Proteobacteria, consistent with their direct contribution to N₂O peaks. Spearman’s correlations showed N₂O positively correlated to sulfur and labile carbon (C), supporting denitrification under moderately reducing conditions. CH₄ and CO₂ positively correlated with organic C (Corg), total nitrogen (TN), and reactive Fe forms, reflecting redox-mediated microbial respiration and methanogenesis. Trace elements (B, Cr, Cu, Ni) acted as micronutrients or inhibitors depending on concentration. Canonical correspondence analysis indicated depth-structured links among gas fluxes, soil chemistry (Corg, TN, S/C, CaCO₃, P), and microbial distributions: surface layers, rich in labile C and nutrients, supported active bacteria and archaea involved in decomposition, nitrification, and denitrification, whereas deeper layers hosted oligotrophic archaea adapted to inorganic substrates. Overall, Fe pools appeared to be associated with soil processes relevant to GHG dynamics, although the extent of their regulatory role remains uncertain due to potential alterations of redox-sensitive Fe fractions during sample handling. These results contribute to broader efforts to predict GHG emissions in submerged wetland soils by linking redox stratification, inorganic chemistry, and microbial functional groups. Full article

Maintaining ballast performance in seasonal frozen regions is essential for resilient and sustainable railway infrastructure because freeze–thaw-driven fouling can shorten service life and increase maintenance-related material consumption. To investigate the deterioration mechanisms of fouled railway ballast in seasonal frozen regions, freeze–thaw cycle tests and cyclic loading model tests were conducted in sequence using a custom low-temperature geotechnical system. The test results processed by Origin software indicate that unfrozen water migrates toward the freezing front under temperature gradients and forms ice lenses during freezing. During thawing, meltwater is retained above the underlying frozen soil. Repeated freeze–thaw cycles therefore promote progressive water accumulation in the upper soil layers, eventually forming a clay layer with high water content. Under cyclic loading, interlayer thickening exhibited clear moisture thresholds relative to the clay liquid limit (LL = 24%). Below the LL (18–24%), ballast penetration and fines migration were limited and thickness increased slowly. Above the LL, rapid strength loss accelerated penetration and upward transport. At an initial water content of 32%, fines migration surpassed the ballast surface and the ballast became fully fouled, meaning that the fouled interlayer thickness equaled the full 100 mm ballast-layer thickness. Fouling severity increased sharply with moisture: the void contaminant index exceeded the maintenance criterion (VCI > 40%) at 28% water content and evolved into severe mud pumping at higher concentrations. Excess pore water pressure developed stratification with depth, maintaining an upward hydraulic gradient near the interface and yielding a net water loss of 2.24–6.91% in the upper fine-grained layer. These quantified thresholds and mechanistic insights provide actionable trigger points for condition-based maintenance and climate-adaptive design, helping extend track-bed service life and reduce resource-intensive ballast renewal in seasonal frozen regions. Full article

The soil–water interface (SWI) represents a critical biogeochemical hotspot where steep physicochemical gradients across millimetre-to micrometre-scales create diverse ecological niches controlling nutrient cycling, carbon stabilisation, and contaminant transformation. This review synthesises emerging understanding of micro-scale microbial dynamics, biofilm architecture, and functional processes shaping SWI ecosystems. We examine redox stratification driving microbial community assembly, biofilm-mediated nutrient trapping and soil aggregate stabilisation, and dynamic drivers including hydrological fluctuations, viral lysis, and differential transport at gas–water versus solid–water interfaces. Advanced methodologies, microsensor profiling, cryo-sectioning, spatially resolved metatranscriptomics, and non-destructive imaging, now enable unprecedented resolution of SWI microhabitat chemistry and microbial organisation. Horizontal gene transfer within interface biofilms accelerates adaptive responses to environmental stressors. Integration of micro-scale observations into ecosystem-level models remains challenging but essential for predicting soil carbon sequestration, contaminant fate, and microbial resilience under climate change. Strategic SWI management through biofilm engineering and controlled redox manipulation offers novel pathways for sustainable agriculture and bioremediation, though it requires careful balance of multiple ecosystem functions. Full article

The behavior of phosphorus (P) fertilizers in soil is governed not only by fertilizer solubility, but also by P mobility and vertical redistribution within the soil profile under contrasting water regime. This study aimed to investigate the combined effects of water regime, fertilizer type, and soil properties on the vertical redistribution of ammonium acetate–lactate extractable phosphorus (P-AL) in the surface soil layer under controlled pot conditions. Experiments were conducted using three soils with contrasting chemical properties: AC-LO (acidic loam, pH 5.9), NE-CL (neutral clay loam, pH 6.8), and AL-SL (alkaline sandy loam, pH 8.0). Four simulated rainfall regimes were applied at a constant rate of 25 mm day⁻¹, corresponding to cumulative water inputs of 0 mm (W0), 50 mm (W50), 100 mm (W100), and 150 mm (W150). Fertilizer treatments included an unfertilized control (NF), a liquid NP 4–18 fertilizer applied at a low dose (L1), a liquid NP 4–18 fertilizer applied at a high dose (L2), and a solid NPK 15–15–15 fertilizer (S). Water regime exerted the strongest control on P mobility, with P-AL increasing by approximately 40–60% from W0 to W150, depending on soil type. In AC-LO, strong P fixation under low moisture minimized differences among fertilizer treatments, whereas under higher moisture (W100–W150), liquid fertilizers—particularly L2—resulted in P-AL levels approximately 10–30% higher than those of the solid fertilizer. In NE-CL, P mobility was moderate and, under W100–W150, L2 produced P-AL values approximately 10–15% higher than the solid fertilizer, promoting a more uniform P redistribution within the 2–8 cm layer. In AL-SL, the response under wet conditions depended on the water regime: at W100, L2 generated P-AL values comparable to the solid fertilizer, whereas at W150, L2 increased P-AL by approximately 11% relative to the solid form. Overall, the results indicate that soil chemical properties primarily regulate the extent of phosphorus redistribution, while water regime controls its intensity and fertilizer form influences the initial spatial configuration of P within the surface soil layer. The findings provide mechanistic insight into short-range phosphorus transport in soil, without allowing direct inferences regarding agronomic efficiency or crop response. Full article

The spatial variability of soil physicochemical properties significantly influences irrigation efficiency, nutrient availability, and the long-term sustainability of irrigated agriculture in semi-arid regions. This study aimed to quantify and model the spatial distribution of soil properties in a semi-arid irrigation district in central Mexico (Irrigation District 001 “Pabellón de Arteaga”, Aguascalientes), providing spatially explicit information for differential irrigation and fertilization management. Ninety-seven crop and four natural sampling sites were established under a stratified random design at two soil depths (0–30 and 30–60 cm). Geostatistical and machine learning models (Ordinary Kriging, OK; Generalized Additive Models, GAM; and Random Forest, RF) were applied to predict spatial patterns, and their performance was evaluated using statistical metrics. The findings reveal high spatial and vertical variability, with most properties (such as organic matter, total nitrogen, and texture) showing significant stratification with depth. In contrast, others (pH and electrical conductivity, EC) remained remarkably homogeneous vertically. Correlation patterns were identified, highlighting the negative influence of alkaline pH (≈8.0) on the availability of micronutrients (Fe²⁺ and Mn²⁺) and the positive association between EC and soluble cations (Ca²⁺, K⁺, and Na⁺). Moran’s Index confirmed significant spatial autocorrelation for most properties, reducing the effective sample size by 30–70%. The comparative evaluation of predictive models demonstrated the superiority of RF over OK and GAMs for predicting chemical properties, thanks to its ability to capture nonlinear relationships and complex interactions. However, the overall predictive performance was moderate, reflecting the multifactorial complexity of the edaphic system. This study lays the foundation for the development of an accessible, low-cost Decision Support System by providing a robust methodological framework for spatial soil characterization and contributing to more sustainable, resilient agriculture, where decision-making is based on quantitative data and predictive models. Full article

When cold waves occur in winter, the entire vineyard greenhouse is completely covered with plastic film to improve heat insulation. However, differences in vertical stratification of soil faunal communities between pre-sealing (PSP) and sealing periods (SP) have not been fully quantified. We compared soil fauna communities and hydrothermal nutrient conditions between PSP and SP in standardized protected vineyards, sampling 0–10, 10–20, and 20–30 cm soil layers. Community traits were analyzed via paired Wilcoxon tests and mixed-effects models, while compositional differentiation was assessed using PCoA/PERMANOVA, NMDS/ANOSIM, and redundancy analysis with hierarchical partitioning. Soil fauna abundance decreased significantly in SP, with sharp declines in 0–10 and 20–30 cm layers, whereas the 10–20 cm layer showed minimal shifts. Taxon richness and alpha-diversity indices exhibited no consistent stage-specific variations. Inter-layer compositional differentiation intensified in SP, indicating enhanced vertical community stratification. Depth-specific analysis revealed the main drivers of community shifts: SOC and C: N in 0–10 cm, pH and C: N in 10–20 cm, and moisture and temperature in 20–30 cm. Overall, we observed layer-dependent shifts in soil microenvironments and faunal communities between PSP and SP, suggesting that soil depth should be considered in protected vineyard management. Full article

Long-term tillage management fundamentally reshapes soil’s physical and chemical environment, yet an integrated, predictive characterization of the distinct chemical signatures induced by no-tillage (NT) versus chisel tillage (CT) remains limited. We analyzed an eight-year dataset (2010–2017) from a long-term experiment in Iowa, USA, focusing on pH, available phosphorus (Bray1-P), and macro- and micronutrients (K, Ca, Mg, Cu, Fe, Zn) at two depths (0–5 and 5–15 cm). A convergent multi-method framework combined robust univariate statistics, multivariate ordination (PCA, PERMANOVA), linear mixed-effects models, and machine learning (Random Forest and Firth-penalized logistic regression). Results reveal a clear stratification–homogenization pattern. NT is associated with surface accumulation of Zn (+14%), Fe (+16%), and Cu (+5%), with mild acidification (−0.4 pH units) and high temporal stability. CT favored vertical nutrient redistribution, marked by subsurface K enrichment (up to 6% higher than NT), progressive alkalinization, and greater temporal variability. Predictive modeling highlighted subsurface K and surface Zn/Fe as key discriminators, with Firth regression confirming their complementary effects. These findings indicate that long-term NT and CT are associated with distinct, depth-specific chemical configurations—integrated systems defined by concentration gradients, temporal stability, and element covariation—rather than isolated element changes. This work provides a robust, quantitative framework for diagnosing soil management history and characterizing the pedochemical imprint of tillage. Full article

Soil texture-dependent responses and time-scales of soil quality change, especially soil carbon, remain poorly understood. We addressed this gap using a dual time-scale design of long-term field experiments: 11 years of minimum (MT) versus ploughing tillage (CT), both followed by 5-year transitions to no-till (NT) in contrasting textures (loamy vs. silty clay) in NE Slovenia. In loamy soils, reduced tillage in the 0–10 cm layer increased soil organic carbon by 40–48%, dissolved organic carbon by 36–64%, permanganate oxidizable carbon by 67–84%, particulate organic carbon by 76–95%, and mineral-associated organic carbon (MAOC < 50 μm) by 28–34%. In silty clay soils, high clay content masked tillage effects, though labile pools showed stratification. MAOC < 20 μm remained stable across treatments and textures (2.0–2.5%), except under CT in loamy soil (1.73%), indicating enhanced decomposition. In loamy soils CT increased by 0.5–1 and 1–2 mm and decreased >20 mm and in silty clay soils increased <0.5, 1–2 and 2–4 mm aggregate formations. The MWD, GMD, Dm indices correlated strongly with C fractions, confirming physical protection mechanisms. Our dual time-scale approach reveals labile C pools and aggregate recovery respond within 5 years of NT, while texture modulates response magnitude and detectability. Full article

Soil moisture is a critical variable in the eco-hydrological processes of arid regions; however, the vertical stratified mechanisms of soil moisture response to meteorological factors in artificial grassland remain inadequately quantified. Based on 10-min interval monitoring data from 2015 to 2024 in the middle reaches of the Heihe River, this study investigated the dynamics of soil moisture within a 0–160 cm depth profile in an arid artificial grassland. By integrating the Mann–Kendall trend test, Pearson correlation, time-lagged cross-correlation, multiple regression analysis and redundancy analysis, we systematically investigated the changing relationships between meteorological factors and soil moisture. The results revealed the following: (1) main meteorological factors driving surface processes (e.g., net radiation, air temperature, vapor pressure deficit) showed significant increasing trends with strong variability, while relative humidity decreased significantly, and these findings collectively point to a general trend of warming and drying in the region; (2) WS, Ta, rainfall, and RH are the principal factors explaining soil moisture variations, wherein temperature and humidity exhibit positive correlations with soil moisture; (3) RDA results showed that shallow soil moisture (0–20 cm) was primarily governed by air temperature and rainfall, whereas deep soil moisture was increasingly regulated by vapor pressure deficit; (4) time-lagged cross-correlation analysis showed that the response time of soil moisture to rainfall almost increased with soil depth, while the correlation coefficient gradually weakened from 0.43 to 0.06. This study quantitatively elucidates the stratified control mechanism of meteorological factors on the vertical pattern of soil moisture, contributing to a deeper understanding of the response of eco-hydrological processes under climate change and providing a scientific basis for water resource management, agricultural planning, and climate prediction. Full article

To enhance the assessment accuracy of tunnel face instability risks of active collapse during shield tunneling, this study establishes a novel unified analytical framework that couples the effects of unsaturated transient seepage induced by excavation drainage with soil stratification and heterogeneity. Grounded in unsaturated effective stress theory, the framework explicitly incorporates matric suction into the Mohr–Coulomb failure criterion via suction stress and apparent cohesion. By employing a horizontal two-layer nonhomogeneous soil model and solving the one-dimensional vertical Richards’ equation, an analytical solution for the face drainage boundary is derived to quantify the spatiotemporal evolution of suction stress and apparent cohesion. Subsequently, the critical support pressure is evaluated using the upper bound theorem of limit analysis, incorporating a horizontal layer-discretized rotational failure mechanism and the power balance equation. The validity of the proposed framework is confirmed through comparative analyses. Parametric studies reveal that in the upper hard and lower soft strata, the critical support pressure decreases and converges over time, indicating that unsaturated transient seepage exerts a significant influence in the short term that stabilizes over the long term. Additionally, sand–silt stratum exhibits lower overall stability and higher sensitivity to groundwater levels and temporal factors compared to silt–clay stratum. Conversely, silt–clay stratum displays a non-monotonic evolution with increasing cover-to-diameter ratios ($C/D$), reaching a minimum critical support pressure at approximately $C/D=1.1$. Regarding heterogeneity, the internal friction angle of the lower layer exerts dominant control over the critical support pressure compared to seepage velocity, while the influence of other strength parameters remains secondary. These findings provide a theoretical basis for the time-dependent design of tunnel face support pressure under excavation drainage conditions. Full article

Soil degradation and limited root-exploitable depth restrict maize productivity in Plinthosols of tropical regions. However, the combined effects of subsoiling and amendments derived from termite mound materials on soil functionality and yield remain insufficiently quantified. This study examines how variations in a functionally exploitable rooting depth, within a management system combining subsoiling and termite mound amendments, are associated with soil physicochemical properties and spatial variability of maize (Zea mays L.) grain yield in the Lubumbashi region of the Democratic Republic of the Congo. Spatial soil sampling and correlation analyses were used to identify the dominant pedological factors controlling yield variability. The results indicate a reduced vertical stratification of most nutrients within the explored depth, reflecting a more homogeneous distribution of soil properties within the managed profile, although direct causal attribution to specific practices cannot be established in the absence of untreated control plots. Improved rooting conditions were reflected by high and spatially variable productivity (2.3 to 11.1 t ha⁻¹ across blocks), accompanied by a moderate average gain between seasons (<1 t ha⁻¹), while extractable manganese emerged as a consistent negative predictor of yield. These patterns are consistent with a larger functionally exploitable rooting depth and an improved soil environment, although causal contributions of subsoiling and termite mound amendments cannot be isolated in the absence of control plots. Overall, the results highlight the importance of jointly considering structural and chemical soil properties when interpreting productivity gradients in Plinthosols and designing sustainable management strategies for degraded tropical soils. Full article

Soil organic carbon (SOC) and total nitrogen (TN) are fundamental indicators of soil fertility and long-term agricultural sustainability. However, intensive cultivation, residue removal, and imbalanced fertilization have resulted in substantial declines in SOC and TN across many agroecosystems, particularly in Northeast China. This study investigated SOC and TN dynamics within the 0–35 cm profile of four representative soils in Northeast China under a continuous maize cropping system. Five treatments were assessed: conventional tillage (CT), deep tillage (DT), deep tillage with straw (SDT), deep tillage with organic fertilizer (MDT), and deep tillage combined with straw and organic fertilizer (SMDT). Compared with DT, organic amendment treatments increased SOC and TN contents in the 0–20 cm layer by 9.41–57.57% and 5.29–60.76%, respectively. The SMDT treatment achieved the highest SOC and TN stocks (65.03 Mg ha⁻¹ and 7.91 Mg ha⁻¹) and enhanced nutrient accumulation in the 20–35 cm layer. In the subsoil, the ratio of soil C and N (C/N) under SMDT increased by 3.11%, 11.08%, 2.10%, and −7.01% across the four soils, indicating improved C–N balance and reduced nutrient stratification. SOC and TN stocks were linearly correlated with cumulative C input, confirming that organic amendments were among the main drivers of C and N sequestration. Mantel and path analyses further revealed that clay content and mean annual precipitation enhanced SOC and TN storage by improving soil structure and C–N balance through increased C input and reduced bulk density. Overall, deep tillage combined with amendments strengthened C–N coupling, improved soil fertility, and provided a mechanistic basis for reconstructing fertile tillage layers and sustaining productivity in Northeast China. Full article

Agrivoltaic systems (AVS) are gaining global attention as an innovative solution to simultaneously address food, water, and energy security challenges. However, the effective design and management of these dual-use systems hinge on a comprehensive understanding of their microclimatic impacts. This systematic review critically analyzes the current literature on AVS microclimates, focusing on key atmospheric (air temperature, relative humidity, wind speed), radiation (Photosynthetically Active Radiation—PAR, global radiation, shading rate), and soil parameters (temperature, moisture). Results indicate that while reduced soil temperature and enhanced moisture retention are consistent and agronomically significant benefits, the effects on air temperature are highly variable. These often demonstrate site-specific warming or pronounced vertical thermal stratification. Furthermore, AVS significantly alters light availability, with PAR reduction ranging from 5% to 94%, emphasizing the system’s inherent spatial and temporal heterogeneity. A major gap identified is the lack of standardized measurement methodologies, limiting data comparability. To address this, we propose a “Minimum Viable Monitoring” (MVM) framework, advocating for multi-zone and multi-height sensor placement to accurately capture microclimatic variability. These findings highlight that the observed heterogeneity, rather than a limitation, presents a unique opportunity for precision agriculture and zoned management strategies. Full article

The coal mining subsidence area constitutes a distinct ecotone in the transition from agricultural soil to sediment, yet the microbially mediated nitrogen cycle within it remains inadequately understood. This investigation comprehensively analyzed physicochemical properties, microbial communities, functional genes, and co-occurrence networks along a 0–6500 mm depth gradient. Results indicated that pH transitioned from acidic to alkaline, while TN, TP, OM, and NH₄⁺–N accumulated with depth. NO₃⁻–N decreased rapidly within 1000 mm and then stabilized. Alpha-diversity showed an S-shaped increase in richness, with Shannon index peaking at 1500 mm. Beta-diversity shifted along PC1, and the shallow subsidence area (SS) influenced by NO₃⁻–N; the transition zone (TZ) regulated by OM, TN, and NH₄⁺–N; deep subsidence area (DS) was constrained by TP and pH. Microbial communities transitioned from aerobic/facultative to strictly anaerobic phyla, yet Pseudomonadota remained dominant (24–32%) across depths. With increasing depth, gene abundances for denitrification, assimilatory nitrate reduction to ammonium (ANRA), and nitrate assimilation declined, while those for dissimilatory nitrate reduction to ammonium (DNRA) and nitrification increased; nitrogen fixation remained weak. Co-occurrence networks shifted from highly connected, short-pathlength, and clustered in TZ to highly modular and long-pathlength in DS, with Aminicenantes, Syntrophus, and Methanoregula as key taxa. Overall, the thick and stable reducing zone in the subsidence area restructured the nitrogen cycle, shifting terminal products from N₂ removal to NH₄⁺ retention. These findings advance the understanding of nitrogen transformation in soil-sediment ecotones and provide a mechanistic framework for nitrogen cycling in mining-affected ecosystems. Full article