Search Results (533)

Soil physicochemical and biochemical properties are fundamental to soil processes and ecosystem functioning in forest environments, yet their responses to dominant tree species in humid montane regions remain largely ununderstood. This study examined the effects of three widespread broadleaf species—Quercus pontica, Quercus petraea, and Fagus orientalis—on soil physical, chemical, and biochemical properties in natural forests in the Eastern Black Sea region, where these species play key ecological roles in structuring forest composition and biogeochemical processes. A total of 15 soil samples (5 per forest type) were collected under comparable climatic and geological conditions and analyzed for particle-size distribution, pH, electrical conductivity (EC), soil organic carbon, and key microbial activity indicators. Significant differences in soil properties were detected among forest types. Soils under Q. pontica were characterized by the lowest silt content and pH, but the highest sand content, soil organic carbon, microbial biomass carbon (C_mic), and microbial respiration. In contrast, soils under Q. petraea exhibited the highest clay content and pH, whereas F. orientalis soils showed lower sand content, EC, soil organic carbon, microbial biomass nitrogen (N_mic), and basal respiration. Multivariate analyses revealed that soil texture, pH, and C_mic are key factors driving soil differentiation across forest types. These patterns indicate that species-specific litter inputs and belowground processes regulate soil biochemical functioning by altering resource availability and habitat conditions. Crucially, this study sheds light on the soil-forming responses of these ecologically dominant species and their impacts on carbon cycle pathways and microbial dynamics at the regional scale. Overall, the study shows that tree species identity is a critical factor influencing soil function, with significant consequences for forest management, carbon sequestration strategies, and ecosystem resilience to changing environmental conditions. Full article

A remote analysis of coastal sedimentation in northern KwaZulu-Natal (KZN), South Africa, describes how summer runoff and winter wave-action operate within a highly variable climate. Despite rising sea levels, the sediment flux can sustain beaches under certain conditions. Daily satellite red-band reflectivity and ocean–atmosphere reanalysis datasets were studied over the period of 2018–2025. Statistical results indicate that streamflow discharges are spread northward by oblique wave-driven currents. Sediment concentrations peak during late winter (>1 mg/L, May–October) when deep turbulent mixing (>40 m) mobilizes sand from the seabed. A case study from September 2021 revealed that ridging high-pressure/cut-off low weather patterns can simultaneously increase streamflow, wave energy, and wind power, creating a surf-zone sediment conveyor along the coast of northern KZN. Long-term climate diagnostics from 1981 to 2025 reveal upward trends in coastal runoff, vegetation, and turbidity (0.29 σ/yr) that point to an increasingly vigorous water cycle. The warming of the southeast Atlantic intensifies the sub-tropical upper-level westerlies and late winter storms over southeast Africa. These processes occur in 5–8 year cycles and drive shoreline advance and retreat, from accretion ~1 T/m and storm surge inundations up to 5.5 m. Using Digital Earth, it was noted that ~1/4 of beaches around Africa are gaining sediment while ~1/3 are eroding. Although remote information could not close the sediment budget, realistic estimates of long-shore transport in the surf-zone (>10⁴ kg/yr/m) and on the beach (>10³ kg/yr/m) were calculated. These provide an emerging explanation for the resilience of northern KZN beaches, as sea levels rise at a rate of 0.6 cm/yr. Full article

This study quantifies the sustainable development thresholds of marine ecosystems under high-intensity human development by establishing a composite evaluation framework based on the Pressure–State–Response (PSR) model. Taking the Nantong sea area as a typical study region, this research indicates that prior to large-scale development (2006–2010), the comprehensive carrying capacity was higher in the northern region than in the south. The lowest capacity was observed near the Yangtze River Estuary, while the Subei Radial Sand Ridges in the north exhibited the highest capacity. Following the period of intensive coastal development (2016–2020), a significant decline in composite marine carrying capacity occurred in the northern radial sand ridge area, whereas the central waters remained stable. The nearshore areas in the south exhibited the poorest capacity. Despite a substantial increase in anthropogenic pressure, the overall decline of the sea area’s composite marine carrying capacity remains within an acceptable range, with all levels categorized as “Near Carrying Capacity” or above. Quantitative assessment of marine environmental carrying capacity and marine ecological carrying capacity provides an effective pathway for monitoring the specific status of the marine environment and determining whether critical thresholds have been reached under high-intensity human development scenarios. Full article

With the depletion of river sand and the rapid expansion of marine infrastructure, seawater–sea-sand concrete (SSC) has attracted increasing attention due to its low cost and sustainability. However, the high chloride content in SSC accelerates steel corrosion. This significantly limits its use in conventional reinforced concrete structures. In recent years, the rise in FRP–steel composite confinement has offered a new solution to this durability bottleneck. Based on this background, scholars have proposed a new type of FRP–steel composite tube confined seawater–sea-sand concrete (FCTSSC) column. This paper reviews the research progress on SSC, CFST, FCFST, and FCTSSC. The latter systems are developed based on the former. The results show that advanced FCTSSC columns exhibit strong synergistic confinement between the FRP and the steel tube when compared with CFST and FCFST. This synergy enhances the bearing capacity, ductility, and post-peak behavior of SSC. Both external and internal FRP configurations can reduce the brittleness and expansion of SSC. They also effectively restrain local buckling of the steel tube. Existing studies mainly focus on short columns. Research on intermediate slender and slender columns remains limited. This includes structural behavior, rational design models, and long-term durability. Finally, future research directions are proposed to support the practical application of FCTSSC in marine engineering. Full article

This paper presents the first study on the fatigue damage behavior of seawater sea-sand concrete (SSC) and its modeling. Experimental tests were conducted on cylindrical specimens subjected to uniaxial compression, investigating the effects of maximum stress level and material variability. The results indicate that the maximum stress-fatigue life curve for SSC can be well represented by a straight line, while the secant stiffness of SSC degrades in a two-phase process: initially in a decelerating manner, followed by an accelerating degradation until failure. Compared to ordinary concrete, SSC exhibits a significantly longer fatigue life. Due to material variability, the fatigue life of SSC shows considerable randomness, which can be effectively modeled using a Weibull distribution. A modification was made to a recently proposed damage model by the author and Li to capture the stochastic fatigue damage evolution behavior of SSC. The modified model successfully simulates both the maximum stress-fatigue life curve and the secant stiffness degradation curve, including their inherent randomness. Future research should explore the underlying specific factors contributing to the significantly longer fatigue life of SSC compared to ordinary concrete. Full article

Seawater sea sand-engineered cementitious composites (SS-ECCs) provide a potential solution to the shortage of freshwater and sand resources for coastal and offshore construction. However, systematic studies on the combined effects of fiber parameters in SS-ECC systems remain limited. This study examines the effects of polyethylene (PE) fiber content (0%, 1%, 1.5%, and 2%) and length (12 mm, 18 mm, and 24 mm) on the mechanical properties of SS-ECC via compressive, tensile, and bending tests. The results indicate that increasing the volume fraction of PE fibers effectively enhances the tensile strength, flexural strength, and flexural toughness of SS-ECC. SS-ECC attained its highest tensile strength with a 24 mm PE fiber length, showing increases of 41.1% and 44.2% over specimens with 12 mm and 18 mm fibers, respectively. Furthermore, based on 28-day curing, the utilization of seawater and sea sand led to increases in tensile and flexural strengths by 12.3% and 17.2%, respectively, relative to ECC prepared with freshwater and river sand, though it resulted in a reduction in toughness. A predictive model for tensile strength is established considering the characteristic value of PE fiber with an R² of 0.8461, indicating reasonable correlation within the tested range. Results from this paper can help to develop a favorable PE fiber-reinforced SS-ECC for ocean engineering. Full article

The 1964 M7.5 Niigata earthquake remains one of the most significant natural laboratories for understanding seismic–induced soil liquefaction and its dependence on geological setting. Among global field case histories, Niigata stands out for the exceptional documentation of liquefaction triggering, lateral spread displacements, and soil–structure interaction. This paper reexamines the event from an engineering–geologic perspective, emphasizing how Holocene coastal and fluvial depositional processes beneath the Echigo Plain controlled the spatial and stratigraphic distribution of liquefaction during the 1964 earthquake. The most severe ground deformations occurred in fluvially reworked sands derived from three major Holocene dune and barrier island systems (CSD1,2,3) formed along the paleo–shoreline of the Sea of Japan. The largest of these, a mid–Holocene transgressive barrier complex deposited to a thickness of 50–60 m of beach and aeolian sand between 8 and 5 ka B.P., now lies buried 5–8 km inland beneath fine–grained alluvial deposits. Tectonic downwarping and deltaic progradation by the Shinano and Agano rivers redistributed these sands into loose, saturated fluvial facies beneath modern Niigata city. Quantitative geotechnical analyses demonstrate that liquefaction occurs within these reworked Holocene units rather than anthropogenic fills. Full article

Heavy metal contamination in coastal and ballast waters motivates the development of low-cost, environmentally compatible filtration media. This study investigates how 6 MeV electron-beam irradiation (0–100 Gy) modifies the surface electronic and chemical properties of quartz-rich Baltic Sea sands collected from four Latvian coastal locations (Riga, Salacgriva, Ventspils, and Liepaja), and how these modifications affect chromium removal from aqueous K₂CrO₄ solutions. Surface electronic behavior was evaluated by near-threshold photoelectron emission spectroscopy (PEES), including electron work function (EWF) and analysis of differentiated spectra, while irradiation-associated changes in near-surface chemistry were assessed by X-ray photoelectron spectroscopy (XPS). Filtration performance was quantified by UV–Vis absorbance of filtrates. Across all sands, EWF values remained within ~4.7–4.9 eV; however, irradiation effects were strongly site-dependent. Liepaja sand exhibited the most pronounced response, including an EWF increase at 40 Gy, a shift in the differentiated PEES peak toward higher photon energies at ≥40 Gy, and the largest integrated photoemission intensity across doses, consistent with an elevated relative photoemission response under identical acquisition and processing conditions. XPS trends for Liepaja were consistent with irradiation-driven modification of the Si–O environment, while other sites showed comparatively minor changes. Filtration results mirrored these observations: Liepaja sand demonstrated the clearest dose-dependent enhancement in chromium removal with a non-monotonic feature at 40 Gy, consistent with competing formation and transformation of oxygen-related surface-reactive centers. Overall, the results show that electron-beam irradiation can modestly enhance Cr(VI) removal by natural quartz sands, with the magnitude governed by site-specific near-surface electronic structure and its dose-dependent evolution. Full article

Thermal energy storage (TES) plays a crucial role in improving the efficiency and reliability of solar thermal systems, particularly when low-cost and readily available materials are desired. This study experimentally investigates the performance of a water–salt thermal energy storage system using sodium chloride (NaCl) at different concentrations in a simple solar collector setup. Experiments were conducted using a laboratory-scale solar thermal energy system under controlled conditions, with water serving as the heat transfer fluid and a fixed flow rate of 15 L/h. The storage medium consisted of water mixed with salt, which was obtained from the Dead Sea before any treatment. In its raw form, this type of salt contains impurities, mainly sand, at a fixed concentration of approximately 1% by weight. The effects of salt concentration on storage temperature, system efficiency, and effective heat capacity were analyzed. The results show that moderate NaCl concentrations improved the average storage temperature by up to 12–18%, increased thermal storage efficiency by approximately 1%, and enhanced the effective specific heat capacity compared to pure water. In contrast, higher salt concentrations resulted in a performance reduction of up to 8–12% due to increased thermal resistance and reduced heat transfer effectiveness. An optimal salt concentration range was identified at which maximum storage efficiency and heat capacity were achieved. These findings demonstrate that common sodium chloride can serve as an effective and economical enhancement material for thermal energy storage when properly optimized. The study provides quantitative evidence and practical insights for the development of low-cost, salt-based thermal energy storage systems for solar thermal applications. This study highlights the importance of concentration optimization and provides practical insights for the development of low-cost, salt-based thermal storage systems for solar energy applications. Full article

The deep reservoir of the K gas field in the Xihu Depression of the East China Sea Basin has ample storage space and a vast reserve scale. However, these deep intervals remain poorly explored and developed, and their reservoir attributes and key controlling factors are not yet well constrained. Using integrated analyses of cores, cast thin sections, scanning electron microscopy, petrophysical statistics, grain-size data, high-pressure mercury intrusion, and nuclear magnetic resonance imaging, together with conventional well logs, we evaluate the roles of sedimentation, diagenesis, and overpressure in the development and distribution of high-quality reservoirs. Based on clastic grain texture and composition, authigenic minerals, diagenetic types and intensities, pore architecture, petrophysical properties, and gas saturation, two types of high-quality deep sandstone reservoirs are identified: rigid, moderately porous sandstones and strongly compacted, low-porosity sandstones. Compaction is the dominant diagenetic process controlling reservoir quality in the Eocene Pinghu Formation. Overpressure prolongs kaolinite stability and promotes precipitation within pore throats, enhancing fluid sealing and retention, yet does not significantly reduce porosity. Rigid moderately porous reservoirs mainly occur in subaqueous distributary channels, whereas strongly compacted low-porosity reservoirs are concentrated in mouth bars and sheet-sand microfacies. This distribution pattern provides guidance for exploring high-quality deep sandstone gas accumulations. Full article

The Mar Menor is the second largest coastal lagoon in the Mediterranean Sea, with a surface area of about 136 km². It is restricted from the open sea by a sandy barrier system (La Manga) interrupted by three tidal inlets. As a result of high evaporation, it is hypersaline (42–47 ppt) in parts. This study examines the factors leading to the rise in sea surface temperature in the Mar Menor through an analysis of long-term sea surface temperature using HadSST1.1 data together with shorter-term Moderate-Resolution Imaging Radiometer and Optimum Interpolation Sea Surface Temperature data. A thermal box model has been constructed for the lagoon in an attempt to balance major heat sources and sinks. Additionally, a thermal probe was deployed in 0.3 m of water to evaluate the benthic flux of heat of the shelly fine sand that covers the lagoon seabed. The results show that the vertical thermal gradient in the seabed inverts between the day and night. Prior to circa 1977, there was no clear trend in SST, and variations were strongly associated with the Atlantic Mutidecadal Oscillation and the North Atlantic Oscillation. Post circa 1980, the maximum summertime sea surface temperature showed a steady increase of 0.34 °C/decade. The cross-correlation of SST in the Mar Menor with external drivers showed that it is dominated by the sea surface temperature of the Western Mediterranean, followed by local air temperature, with a minor contribution from the Indian Ocean Dipole. No other significant correlations were evident, suggesting that local temperature was dominated by local drivers. In addition, a Spearman rank order evaluation and principal component analysis showed that the general trends of the Mar Menor SST were also influenced by the Atlantic Multidecadal Oscillation, CO₂, and GDP. Full article

Saltmarshes have emerged as important sinks for microplastic (MP) pollution, yet little is known about the long-term accumulation and retention mechanisms of MPs in these environments. This study presents the first chronological record of MPs in Mediterranean saltmarsh sediments, using sediment cores dated via a combination of AMS radiocarbon (¹⁴C) and radionuclide (²¹⁰Pb, ¹³⁷Cs, ²⁴¹Am) from two saltmarshes located on the Adriatic Sea coast of Croatia (Blace and Jadrtovac). MPs were extracted and analysed across core depths and assessed in relation to geochemical parameters (organic matter (OM), carbonates, organic carbon (C-org), total nitrogen (TN), phosphorus (P) forms’ content, and grain size distribution). Results show that MPs first appear in sediments dated to 1950 in Jadrtovac and post-1960 in Blace, with concentrations increasing markedly in more recent surface layers. Jadrtovac exhibited higher MP concentrations (up to 0.5 MPs g⁻¹), dominated by fibres (86%) associated with urban and maritime sources, while Blace showed lower concentrations, dominated by fragments (60%), likely from localised sources such as agriculture or single-use packaging. Polymer analysis confirmed contrasting source profiles, with rayon and cellophane dominating in Jadrtovac, and polypropylene and olefin in Blace. MPs positively correlated with OM, C-org, P, TN and sand content, and negatively with clay and carbonate content. Principal component analysis (PCA) confirmed that MPs were associated with organic-rich, sandy sediments. These findings demonstrate that OM composition and sediment texture significantly influence MP retention and highlight the role of saltmarshes as long-term archives of plastic pollution in low-energy coastal settings. Full article

To overcome the high cost, marine ecological risks of traditional coral sand reinforcement, and the insufficient mechanical performance of standalone Enzyme-Induced Carbonate Precipitation (EICP), this study proposes a novel soil improvement method integrating EICP with aluminum chloride hexahydrate (AlCl₃·6H₂O). The objectives are to identify optimal EICP curing parameters, evaluate AlCl₃·6H₂O’s enhancement effect, and reveal the synergistic micro-mechanism. Through aqueous solution, unconfined compressive strength, permeability, X-ray diffraction (XRD), nuclear magnetic resonance (NMR), and Scanning Electron Microscope (SEM) tests, this study systematically investigated the reaction conditions, mechanical properties, anti-seepage performance, mineral composition, and pore structure. The results demonstrate that EICP achieves the best curing effect under specific conditions: temperature of 30 °C, pH of 8, and cementing solution concentration of 1 mol/L. Under these optimal conditions, the unconfined compressive strength of EICP-solidified coral sand columns reaches 761.6 kPa, and the permeability coefficient is reduced by one order of magnitude compared to unsolidified samples. Notably, AlCl₃·6H₂O incorporation yields a significant synergistic effect, boosting the UCS to 2389.1 kPa (3.14 times standalone EICP) and further reducing permeability by 26%. Micro-mechanism analysis reveals that AlCl₃·6H₂O acts both by generating cementitious aggregates that provide nucleation sites for uniform calcite deposition and by accelerating the transformation of metastable aragonite and vaterite to stable calcite, thereby enhancing cementation stability. This study delivers a cost-effective, eco-friendly solution for coral sand reinforcement, providing practical technical support for marine engineering in environments like the South China Sea. By addressing the core limitations of conventional bio-cementation, it opens new avenues for advancing soil improvement science and applications. Full article

The ancient city of Gela (built in the 7th century BCE) is located in the southern sector of the Sicily Island (Southern Italy) on a Pleistocene marine terrace near the mouth of the Gela River. Gela was one of the most important Greek colonies in the Mediterranean Sea, strategically positioned at the crossroads of the major maritime trade routes and with a rich production of cereals thanks to the fertile Gela River alluvial plain. To reconstruct the coastal and environmental configuration during the Greek period and to improve the understanding of the location of the harbour basin, a multidisciplinary approach was applied to a sector of the Gela River alluvial–coastal plain. This area, located very close to the ancient city, is known as Conca (Italian for “Basin”) and was identified through the analysis of historical and modern maps as well as aerial photographs. The multidisciplinary approach includes geomorphology (derived from maps and aerial photos), stratigraphy (boreholes and archeological trench), paleoecology (ostracoda, foraminifera and fossil contents of selected layers), geochronology (¹⁴C dating of selected organic materials) and archeology (historical sources and maps, pottery fragments extracted from boreholes and trench layers). The main results show that this area was occupied by lower shoreface environments in the time intervals between 4.4 and 2.8 ka, which progressively transitioned to upper shoreface environments until the Greek age. During the Roman period, these environments were significantly reduced due to repeated alluvial sedimentation of the Gela River transforming the area into fluvial–marshy environments. A time interval of aeolian sand deposition was recorded in the upper part of the coastal stratigraphical succession, which can be related to climatic conditions with high aridity. Available data show that marine environments persisted in the Conca sector during the Greek age, allowing hypothesizing the presence of an ancient harbour in this area. The depth of the Greek age marine environments is estimated to be between 4.5 and 7 m below the current ground level. Further investigation, mainly based on geophysical and stratigraphical methods, will be planned aimed at identifying the presence of buried archeological targets. Full article

The Jianggang sand ridges (JSR) in the southwestern Yellow Sea are a radiating tidal sand ridge system that plays crucial roles in ecological preservation, coastal protection, and terrestrial resource supply. Clay and silt fractions constitute important sediment components of the Jianggang sand ridges. In this study, the Sr-Nd isotopes of clay fractions and the Pb isotopes of K-feldspar in the silt fractions, along with their elemental geochemistry, are investigated to reveal the provenance and transport patterns of clay-size and silt-size sediments in the study areas. The results show that in both the clay-size sediments and the K-feldspar of the silt-size sediments, Ba exhibits the highest content, with the ranges of 432.24 μg/g to 531.05 μg/g and 398.02 μg/g to 2822.36 μg/g, respectively. In contrast, Lu shows the lowest abundance (<0.5 μg/g and <0.1 μg/g, respectively). The ⁸⁷Sr/⁸⁶Sr and ε_Nd(0) values of the clay fraction vary from 0.7158 to 0.7265 and from −14.65 to −10.92, respectively. The ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, and ²⁰⁸Pb/²⁰⁴Pb of K-feldspar in silt fraction are 17.959~18.429, 15.450~15.689, and 38.066~38.551, respectively. Through the MixSIAR model, it is suggested that the Yangtze River Mouth is the dominant contributor to clay-size sediments in both the onshore and offshore sand ridges (53.9 ± 8.8% and 51.9 ± 8.4%, respectively), followed by the Modern Yellow River Mouth and the Old Yellow River Delta (sum of contributions: <36%). For the silt fraction, the primary sediment sources of the onshore and offshore sand ridges are the Yangtze River Mouth (46.8 ± 5.5%) and the Old Yellow River Delta (42.4 ± 5.3%), while the Modern Yellow River contributes less than 16%. The Northern Chinese Deserts and the Korean rivers make only minor contributions to both fractions. Elemental and isotopic tracers indicate that the silt-size and clay-size sediments derived from the Modern Yellow River are transported southward along the Jiangsu coast by the Subei Coastal Current. Meanwhile, the silt fraction from the Yangtze River Mouth is carried northward along the coast under the influence of the Subei Coastal Current, whereas the clay fraction of it has another longer path, which moves through the central Yellow Sea and migrates southward along the Jiangsu coast to the Jianggang sand ridges under the influence of the Yellow Sea Warm Current. This study enriches the geochemical dataset of the southern Yellow Sea. Full article