Search Results (240)

The Eocene fourth member of the Shahejie formation (Es4x) in the Bonan Depression, Bohai Bay Basin, records syn-rift sedimentation under alternating arid and humid climates. It provides insight into how orbital-scale climatic fluctuations influenced tectonics, facies patterns, and reservoir distribution. This study integrates 406 m of core data, 92 thin sections, 450 km² of 3D seismic data, and multiple geochemical proxies, leading to the recognition of five facies associations (LFA): (1) alluvial fans, (2) braided rivers, (3) floodplain mudstones, (4) fan deltas, and (5) saline lacustrine evaporites. Three major depositional cycles are defined within the Es4x. Seismic reflections, well-log patterns, and thickness trends suggest that these cycles represent fourth-order lake-level fluctuations (0.8–1.1 Myr) rather than short 21-kyr precession rhythms. This implies long-term climate and tectonic modulation, likely linked to eccentricity-scale monsoon variability. Hyperarid phases are marked by Sr/Ba > 4, δ¹⁸O > +4‰, and thick evaporite accumulations. In contrast, Sr/Ba < 1 and δ¹⁸O < −8‰ reflect humid conditions with larger lakes and enhanced fluvial input. During wet periods, rivers produced sand bodies nearly 40 times thicker than in dry intervals. Reservoir quality is highest in braided-river sandstones (LFA 2) with 12%–19% porosity, preserved by chlorite coatings that limit quartz cement. Fan-delta sands (LFA 4) have <8% porosity due to calcite cementation, though fractures (10–50 mm) improve permeability. Floodplain mudstones (LFA 3) and evaporites (LFA 5) act as seals. This work presents a predictive depositional and reservoir model for arid–humid rift systems and highlights braided-river targets as promising exploration zones in climate-sensitive basins worldwide. Full article

As a sink for microplastics (MPs) in the aquatic environment, sediments have garnered considerable attention. However, the occurrence characteristics of MPs in sediments of different water seasons are not clear, especially for reservoir sediment cores. This study aimed to elucidate the occurrence, spatial and vertical distribution, fragmentation and pollution risk of MPs in the sediment cores of the Xiangxi River, Three Gorges Reservoir (TGR) during different seasons. In sediment cores, the average abundance of MPs was 8.57 × 10³ ± 5.65 × 10³ items/kg DW in the wet season (WS) and 7.98 × 10³ ± 4.00 × 10³ items/kg DW in the dry season (DS), respectively. The abundance of MPs in surface sediments and sediment cores exhibited spatial heterogeneity, reflecting seasonally contrasting hydrodynamic conditions between sites S1 and S3. However, the abundance of MPs in the river estuary was the highest, both in surface sediments and sediment cores. Interestingly, the occurrence characteristics of MPs in surface sediments indicated that in addition to anthropogenic activity, hydrological conditions of the river can also have an impact on the spatial distribution of MP abundance in surface sediments. Polypropylene (PP), polyethylene (PE), polystyrene (PS), and polyethylene-propylene copolymer (EPM) were identified as the dominant polymer types (57–99%), with small-sized microplastics (SMPs, 0–300 μm) being the most prevalent. Water seasons influenced the size distribution of MPs in surface sediments. Using a conditional fragmentation model, MP sources were inferred by comparing fragmentation parameters (λ and α) in sediments with those reported for atmospheric deposition, reservoir water, and water-level fluctuation zone soils. Furthermore, the pollution load index (PLI) exceeded 1, indicating MP accumulation in the sediments. The pollution risk index (PRI) values indicated a considerable (300 < PRI < 1000) pollution risk in two water seasons, primarily due to the presence of polyvinyl chloride (PVC). This study enhances the understanding of MP behavior and associated environmental risks in reservoir sediments, offering valuable insights for future research and pollution mitigation efforts. Full article

The Jing River–Dongting Lake (DTL), a critical river–lake complex system in the Middle Yangtze River, China, plays a vital role in flood regulation and ecological sustainability. Recent decades have experienced significant morphology adjustments due to upstream reservoir operations; however, the long-term high-resolution hydro-morphodynamic evolution and its impacts on river–lake interactions remain insufficiently quantified. To address this gap, a two-dimensional hydro-morphodynamic model based on HEC-RAS was employed to simulate three decades of hydro-morphology evolution under projected flow–sediment conditions. The model was validated against observed data and reproduced erosion–deposition trends consistent with previous numerical studies. The results indicate sustained channel incision in the Jing River, with a cumulative erosion volume of 462 million m³, in contrast to net deposition in the DTL area totaling 276 million m³ over three decades. A comparison of results under a sediment reduction regulation shows that the overall spatial pattern of erosion and deposition remains largely consistent, although local areas, particularly the confluence of the three major inlets feeding the lake, exhibit pronounced sensitivity to sediment variations. Furthermore, continuous mainstream incision intensifies a draining effect on the lake during dry seasons, leading to declines in both water levels and surface area in the DTL. This effect is most pronounced in the eastern lake area, with reductions being markedly greater in dry periods than in wet periods. Finally, the lake’s storage capacity progressively decreases, with an average annual loss of approximately 36.5 million m³ in the wet periods, underscoring significant impairment of its flood-regulation function. This study provides a validated modeling framework and critical insights for predicting morphological evolution and informing adaptive management in large river–lake systems. Full article

Atmospheric nitrogen deposition in coastal areas has a significant impact on water nutrients, with increasing emission of atmospheric nitrogen-containing pollutants. Clarifying the characteristics, source, and nutrient impact of atmospheric inorganic N deposition is therefore critical for targeted eutrophication control in coastal areas. Dry and wet atmospheric nitrogen deposition samples were collected and integrated into the atmospheric deposition model to analyze the influence of the deposition flux and source on coastal water nutrients. The results showed that inorganic nitrogen in the atmosphere over Xiamen’s coast was mainly composed of NH₄⁺-N and NO₃⁻-N. A high concentration of nitrogen was found in the cold season. Source apportionment analysis revealed that NH₄⁺-N mainly originated from agricultural sources, while NO₃⁻-N was primarily derived from traffic sources (24%) and secondary sources (25%). The wet deposition flux of NH₄⁺-N and NO₃⁻-N was significantly larger than the dry deposition flux. The NO₃⁻-N wet deposition flux was elevated during winter and summer, whereas the dry deposition flux peaked in spring and winter. A high NH₄⁺-N wet deposition flux was also found in spring and summer. Spatially, the inorganic nitrogen deposition flux was higher in offshore areas than in the inner bay, which was attributed to the higher wind speed in the offshore region. The atmospheric inorganic nitrogen input accounted for only 0.9% to 1.8% of the inorganic nitrogen input from the Jiulong River to Xiamen Bay; however, the NO₃⁻ concentration in Xiamen Bay showed a significant positive correlation with the dry deposition flux of atmospheric nitrogen (p < 0.05). Atmospheric nitrogen deposition directly affects coastal water nutrients without estuarine filtration. This study clarifies the different sources of atmospheric inorganic nitrogen deposition and their contribution to coastal water nutrients, providing an important basis for eutrophication in coastal areas, as well as pollutant control and emission reduction efforts. Full article

Copper and iron species were co-deposited onto a hydroxyapatite surface to produce bimetallic catalysts. Characterization techniques (XRD, XPS, DR-UV spectroscopy and TEM-EDX) helped in unveiling the speciation, nuclearity, and electronic properties of copper and iron in samples with variable total metal loading (1–10 wt.%) and relative Cu-to-Fe ratios. The speciation of Cu was revealed to be not affected by Fe and vice versa. Conversely, the metal loading turned out to be a key factor ruling the aggregation state of Cu and Fe species. The samples were tested as catalysts in the Selective Catalytic Reduction of NO by NH₃ (NH₃-SCR) in dry and wet environments under quasi-real conditions (50,000 ppm O₂; 50,000 ppm H₂O, if present; 120,000 h⁻¹ GHSV) in the 200−500 °C interval. Although the combination of Cu and Fe affords a modest improvement in water resistance compared to their monometallic counterparts, no substantial enhancement in activity was observed for the bimetallic hydroxyapatite-based SCR catalysts. Full article

Soiling is one of the main performance risks for bifacial photovoltaic (PV) technology, particularly in arid environments such as the Atacama Desert, where dust is deposited asymmetrically on the front and rear surfaces of the modules. This study evaluates one year (July 2022 to June 2023) of soiling behavior in bifacial modules installed in fixed-tilt and horizontal single-axis tracking (HSAT) configurations, enabling a comparison to be made between static and moving structures. The average dust accumulation was found to be 0.33 mg/cm² on the front surface and 0.15 mg/cm² on the rear surface of the fixed modules. In contrast, the respective values for the HSAT systems were found to be lower at 0.25 mg/cm² and 0.035 mg/cm². These differences resulted in performance losses of 5.8% for fixed modules and 3.7% for HSAT systems. Microstructural analysis revealed that wetting and drying cycles had formed dense, cemented layers on the front surface of fixed modules, whereas tracking modules exhibited looser deposits. Natural cleaning events, such as fog, dew and frost, only provided partial and temporary mitigation. These findings demonstrate that bifaciality introduces differentiated soiling dynamics between the front and rear surfaces, emphasizing the importance of tailored cleaning strategies and the integration of monitoring systems that consider bifacial gain as a key operational parameter. These insights are crucial for developing predictive models and cost-effective O&M strategies in large-scale bifacial PV deployments under desert conditions. Full article

As the residual products of severe chemical weathering, bauxite deposits serve both as essential economic Al-Fe resources and geochemical archives that reveal information about the parent rocks’ composition, paleoenvironments and paleoclimates, and the tectonic settings responsible for their genesis. The well-developed Early Paleocene bauxite deposits of the Salt Range, Pakistan, provide an opportunity for deciphering their ore genesis and parental affinities. The deposits occur as lenticular bodies and are typically composed of three consecutive stratigraphic facies from base to top: (1) massive dark-red facies (L-1), (2) composite conglomeratic–pisolitic facies (L-2), and (3) Kaolinite-rich clayey facies (L-3). Results from optical microscopy, X-ray powder diffraction (XRPD), and scanning electron microscopy with Energy-Dispersive X-Ray Spectroscopy (SEM-EDS) reveal that facies L-1 contains kaolinite, hematite, and goethite as major minerals, with minor amounts of muscovite, quartz, anatase, and rutile. In contrast, facies L-2 primarily consists of kaolinite, boehmite, hematite, gibbsite, goethite, alunite/natroalunite, and zaherite, with anatase, rutile, and quartz as minor constituents. L-3 is dominated by kaolinite, quartz, and anatase, while hematite and goethite exist in minor concentrations. Geochemical analysis reveals elevated concentrations of ${\mathrm{Al}}_2$${\mathrm{O}}_3$, ${\mathrm{Fe}}_2$${\mathrm{O}}_3$, ${\mathrm{SiO}}_2$, and ${\mathrm{TiO}}_2$. Trace elements, including Th, U, Ga, Y, Zr, Nb, Hf, V, and Cr, exhibit a positive trend across all sections when normalized to Upper Continental Crust (UCC) values. Field observations and analytical data suggest a polygenetic origin of these deposits. L-1 suggests in situ lateritization of some sort of precursor materials, with enrichment in stable and ultra-stable heavy minerals such as zircon, tourmaline, rutile, and monazite. This facies is mineralogically mature with bauxitic components, but lacks the typical bauxitic textures. In contrast, L-2 is texturally and mineralogically mature, characterized by various-sized pisoids and ooids within a microgranular-to-microclastic matrix. The L-3 mineralogy and texture suggest that the conditions were still favorable for bauxite formation. However, the ongoing tectonic activities and wet–dry climate cycles post-depositionally disrupted the bauxitization process. The accumulation of highly stable detrital minerals, such as zircon, rutile, tourmaline, and monazite, indicates prolonged weathering and multiple cycles of sedimentary reworking. These deposits have parental affinity with acidic-to-intermediate/-argillaceous rocks, resulting from the weathering of sediments derived from UCC sources, including cratonic sandstone and shale. Full article

This research presents a comprehensive spatiotemporal assessment of the effects of climate change and anthropogenic pressures on the water surface area and quality of the Sidi Salem Dam, the largest reservoir in Northern Tunisia. Located within a sub-humid to Mediterranean humid bioclimatic zone, the dam plays a vital role in regional water supply, irrigation, and flood control. Utilizing a 40-year dataset (1985–2025), this study integrates multi-temporal satellite imagery and geospatial analysis using Geographic Information System (GIS) and remote sensing (RS) techniques. The temporal variability of the dam’s surface water extent was monitored through indices such as the Normalized Difference Water Index (NDWI). The analysis was further supported by climate data, including records of precipitation, temperature, and evapotranspiration, to assess correlations with observed hydrological changes. The findings revealed a significant reduction in the dam’s surface area, from approximately 37.8 km² in 1985 to 19.8 km² in 2025, indicating a net loss of 18 km² (47.6%). The Mann–Kendall trend test confirmed a significant long-term increase in annual precipitation, while annual temperature showed no significant trend. Nevertheless, recent observations indicate a decline in precipitation during the most recent period. Furthermore, Pearson correlation analysis revealed a significant negative relationship between precipitation and temperature, suggesting that wet years are generally associated with cooler conditions, whereas dry years coincide with warmer conditions. This hydroclimatic interplay underscores the complex dynamics driving reservoir fluctuations. Simultaneously, land use changes in the catchment area, particularly the expansion of agriculture, urban development, and deforestation have led to increased surface runoff and soil erosion, intensifying sediment deposition in the reservoir. This has progressively reduced the dam’s storage capacity, further diminishing its water storage efficiency. This study also investigates the degradation of water quality associated with declining water levels and climatic stress. Indicators such as turbidity and salinity were evaluated, showing clear signs of deterioration resulting from both natural and human-induced processes. Increased salinity and pollutant concentrations are primarily linked to reduced dilution capacity, intensified evaporation, and agrochemical runoff containing fertilizers and other contaminants. Full article

Cold gas dynamic spraying (CGDS) enables the production of protective coatings without melting or oxidation. In this study, Al–Zn–TiO₂ composite powders were prepared by wet agglomeration with binders and by dry mechanical mixing, and deposited onto mild steel substrates. COMSOL simulations of gas dynamics and particle acceleration identified optimal parameters (0.6 MPa, 600 °C, 15 mm, 90°), which were then validated experimentally. Coatings formed under these conditions exhibited dense microstructures, minimal porosity (~0.5%), and continuous, defect-free interfaces with the substrate. SEM and XRD confirmed solid-state bonding without new phase formation. Corrosion tests in 3.5% NaCl revealed a tenfold reduction in corrosion current density compared to bare steel, resulting from synergistic sacrificial (Zn), barrier (Al), and reinforcing/passivating (TiO₂) effects. Tribological tests demonstrated reduced friction (CoF ≈ 0.4–0.5) and wear volume. Compared with reported Al- or Zn-based cold- and thermal-sprayed coatings, the optimized Al–Zn–TiO₂ system shows superior performance, highlighting its potential for industrial anti-corrosion and wear-resistant applications. Full article

Polyethylene terephthalate (PET) is widely used in food packaging, biomedical, and optical applications, but its inherent wettability limitations can hinder its performance in extreme environments. To this end, several methods have been developed to improve PET wetting properties. Yet, most of the methods proposed are wet and involve the use of chemical reagents, whereas, in most of the dry-based methods, such as plasma-based methods, which can easily tune the wetting properties of polymeric materials such as PET, achieving long-term stability, especially in extreme wetting states (superhydrophilicity and superhydrophobicity), remains a challenge. In this work, oxygen plasma etching is used to micro-nanotexture thin and, therefore, flexible PET films (thickness: 50 μm) for three different time durations of 4, 6, and 12 min followed by a C₄F₈ plasma deposition of a hydrophobic film or a hydrophilic poly (ethylene glycol) coating depending on the wettability profile targeted. Using this dry and, therefore, “green” and simple two step method, durable superhydrophilic and superhydrophobic surfaces that last for at least one year have been successfully realized. Finally, it is also shown that wetting control can be achieved without significantly affecting the inherent optical properties of the PET film (texturing duration up to 6 min), highlighting the multifunctionality of the plasma micro-nanotextured PET film. Full article

Globally, sediment transport from rivers and the morphological evolution of deltas are strongly shaped by human activities. The Yellow River Delta is a typical representative of this. In this paper, Delft 3D v4.01.00 software was used to simulate the sediment diffusion in the subaqueous delta of the Yellow River in 2017 so as to explore the influence of the sediment and water transported by the Yellow River on the subaqueous delta without water and sediment regulation. The results reveal the occurrence of a low–high–low suspended sediment concentration distribution from the coastlines to the far shore. The main accumulation areas shifted from the coasts of Bohai Bay and Laizhou Bay in the dry season to the estuary in the wet season. The sediments entering the sea formed deposition zones along the coastline, and erosion zones were formed outside these deposition zones, with a maximum depth of about 5 m. In 2017, the impact of the sediment inflow into the Yellow River on its subaqueous delta generally resulted in the erosion being greater than the sedimentation, and the erosion/deposition volume in 2017 was −1.28 × 10⁸ m³, and the estimated critical value of the sediment inflow balance was 2.13 × 10⁸ tons. Full article

Loess, a typical unsaturated soil, is a Quaternary sedimentary deposit widely distributed across arid and semi-arid regions worldwide. In recent years, global climate change has led to significant temperature fluctuations in Northwest China, impacting loess properties and soil–water characteristic curves (SWCCs). This study investigated typical loess deposits in Mizhi County, Shaanxi Province, systematically analyzing their basic physical properties and microstructure. The SWCCs of the loess were measured at three temperature gradients (15 °C, 20 °C, and 25 °C) using the dynamic dew-point isotherm method to investigate the impact of temperature on SWCC hysteresis. The results showed that with increasing temperature, the SWCC exhibited increasing divergence. The magnitude of the water content change and the corresponding suction forces along the wetting and drying paths increased, leading to an enlargement of the hysteresis loop area. These findings indicate that temperature significantly affects the hysteresis behavior of loess, providing a certain basis and ideas for the study of the soil–water characteristic curves of unsaturated soils such as loess under the influence of temperature. Full article

Machining chromium–nickel alloy steel is challenging due to its material properties, such as high strength and toughness. These properties often lead to tool damage and degradation of tool life, which overall impacts the production time, cost, and quality of the product. Therefore, it is essential to investigate early signs of tool damage to determine the effective machining conditions for chromium–nickel alloy steel, thereby increasing tool life and improving product quality. In this study, the early signs of tool wear were observed in a physical vapor deposition (PVD) carbide-coated tool (Seco Tools, Björnbacksvägen, Sweden) during the machining of X5CrNi18-10 steel under both dry and wet conditions. A finish turning operation was performed on the outer diameter (OD) of the workpiece with a 0.4 mm nose radius tool. At the early stage, the tool was examined from the functional side (f–side) and the passive side (p–side). The results indicate that dry machining leads to increased coating removal, more heat generation, and visible damage, such as pits and surface scratches. By comparison, wet machining helps reduce heat and wear, thereby improving tool life and machining quality. These findings suggest that a coolant must be used when machining chromium–nickel alloy steel with a PVD carbide-coated tool. Full article

Age-related macular degeneration (AMD) is an ocular pathology in humans characterized by the buildup of lipid-rich extracellular deposits, which leads to retinal degeneration. In recent years, considerable effort has been made to observe the effect of dietary fatty acids on oxidative stress and inflammation. In continuation of this, much effort has been made to study the effect of dietary fatty acids on the pathogenesis of AMD. Although studies have shown that dietary fatty acids are effective against few forms of AMD, particularly wet AMD or neovascular AMD, no dietary lipids have shown any conclusive results for dry AMD or geographic AMD. It is therefore important to look for new lipids and lipoproteins that can be helpful in treating various stages of AMD. This article reviews the impact of saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs), and polyunsaturated fatty acids (PUFAs) on retinal health and the progression of AMD. Furthermore, this manuscript discusses all studies investigating the implications of fatty acids on AMD, which may be beneficial for future treatment strategies and dietary guidelines related to it. In conclusion, studies suggest that omega-3 PUFAs, particularly docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), might provide protection against AMD, highlighting the necessity for additional clinical trials to evaluate their efficacy in the prevention and treatment of AMD. Full article

This investigation examined the physicochemical characteristics and heavy metal contamination within the surface sediments and aquatic environments of Pattani Bay, Thailand, throughout both wet and dry seasons. The sediments were primarily composed of fine-grained materials, specifically silt and clay, and exhibited greater propensity to absorb heavy metals from water. Notably elevated concentrations of Cd and Pb were detected, particularly within riverine sediment deposits. This indicates that riverine inputs are significant pathways of the contamination and potentially associated with historical mining activities. Seasonal fluctuations affected physicochemical parameters as well as metal concentrations. The heightened levels of Cd and Pb during the wet season were attributed to runoff phenomena. Pollution indices including the Contamination Factor (CF), pollution load index (PLI), and geoaccumulation index (Igeo) demonstrated moderate to extremely high contamination levels of Cd and Pb in certain areas. The Principal Component Analysis (PCA) suggested possible similar sources for multiple metals including Cd, Cu, Pb, and Zn. The results showed that the heavy metal pollution present is serious, especially for Cd and Pb. These could lead to high ecological health risks and so it is necessary to focus on implementing environmental management strategies for Pattani Bay. Full article