Search Results (880)

Estuaries along South Africa’s coastline are increasingly subjected to anthropogenic pressures that disrupt their biogeochemical function and increase the risk of contamination. This study presents the first seasonal assessment of heavy metal contamination and water quality indices in the Qholora Estuary, Eastern Cape Province. Surface water samples collected during wet and dry seasons were analysed for physicochemical properties and heavy metals (As, Cd, Cu, Fe, Hg, and Pb). Multiple pollution metrics (Pollution Index (PI), Nemerow Pollution Index (NPI), Heavy Metal Evaluation Index (HEI), Heavy Metal Pollution Index (HPI)), ecological risk indices ((Ecological Risk Index (ERI), and Potential Ecological Risk Index (PERI)), and the Water Quality Index (WQI) were applied and supported by Principal Component and Cluster Analyses to identify dominant pollutant, contamination sources and seasonal hydro-geochemical controls. Results reveal strong seasonal contrasts: wet-season conditions showed elevated ionic concentrations and enhanced mobilisation of Cu, Pb, Cd, Hg, and Fe due to storm-driven runoff and sediment resuspension, while dry-season patterns reflected evapo-concentration, prolonged residence times, and pH-mediated metal partitioning. Across indices, heavy metal contamination remained low in the dry season but increased significantly in the wet season, especially for Hg, which posed moderate to considerable ecological risk at most sites, indicating emerging ecological pressure under high-flow conditions. These findings highlight a generally low risk under average conditions but a pronounced seasonally vulnerable estuarine system, underscoring the need for intensified monitoring during periods of increased runoff. The study establishes an important baseline for regional water resource management. Full article

Cubane-type iron–sulfur clusters play central roles in biological nitrogen fixation, where precise redox regulation governs multi-electron transfer processes. However, how heterometal centers and terminal ligands cooperatively modulate the electronic structure and redox behavior of such clusters remains insufficiently understood. Herein, we report a systematic study on a series of cubane-type [MoFe₃S₃N] clusters as structural mimics of nitrogenase cofactors. Using [(Tp*)MoFe₃S₃(μ₃-NSiMe₃)Cl₃]⁻ as a common precursor, thiolate (RS⁻; R = Me, Et, Ph) and N-heterocyclic carbene (NHC^R; R = Me, Et, iPr) ligands were introduced to probe ligand effects under an invariant cluster framework. All complexes were fully characterized by single-crystal X-ray diffraction and electrochemical measurements. Combined with previously reported tungsten analogues, a direct comparison reveals that both heterometal identity (Mo vs. W) and terminal ligand environment significantly influence local electron density and intermetallic redox cooperativity. Notably, strong σ-donating NHC ligands and heavier heterometal centers induce distinct modulation patterns, highlighting their synergistic roles. This work provides a unified platform for disentangling metal- and ligand-driven effects and offers feasible strategies for the rational tuning of redox properties in heterometallic Fe–S clusters. Full article

To investigate the respective contributions of cations (Na⁺, K⁺, Zn²⁺, Fe³⁺) and anions (Cl⁻ and SO₄²⁻) to the formation of whey protein isolate (WPI)-based nanofibrils, eight salts with a 4 × 2 factorial design were added to WPI solutions. The morphology and aggregation process of the fibril aggregates were examined under fixed low salt concentration (10 mmol/L) to isolate ion-specific effects. The salts altered the pH, conductivity, and fibril yield. Notably, the Na⁺, K⁺, and Zn²⁺ salts increased fibril production, whereas Fe³⁺ salts reduced it. Mechanistically, Fe³⁺ strongly suppressed fibrillation via strong electrostatic interaction and accelerated protein hydrolysis, while SO₄²⁻ partially alleviated this inhibition. All the ions altered the kinetic parameters. Compared with Cl⁻ salts, SO₄²⁻ salts induced shorter, clustered fibrils and stronger kinetic suppression, preserving elongated fibrils. X-ray photoelectron spectroscopy (XPS) confirmed anion incorporation, and X-ray diffraction (XRD) revealed secondary structural changes. These results demonstrate that while cations contribute to fibril formation, anions play a deterministic role in regulating assembly kinetics and morphological outcomes, independent of cation valence. In this study, we establish a mechanistic basis for tailoring WPI fibril aggregation states through anion-specific salt selection. Full article

Hyperspectral remote sensing enables precise identification of alteration mineral through spectral–image integration and high-resolution capabilities. However, vegetation interference significantly hinders the extraction of alteration information in vegetated areas, thereby posing challenges to the reliable identification of alteration minerals. This study employs GF-5B satellite AHSI imagery acquired in the Huzhou region of Zhejiang Province, China, to address this challenge via a novel Zonal Adaptive Vegetation Suppression Technique (ZAVST). By constructing segmented statistical models that links reflectance characteristics across multiple spectral bands to NDVI values, ZAVST demonstrates an enhanced capability to mitigate vegetation obscuration effects on subsurface lithological features while substantially improving the identification of subtle spectral signatures characteristic of mineralization. Results reveal distinct spatial patterns: Fe-bearing alteration minerals (hematite, pyrite) align along NE-trending faults and volcanic basin margins; Al-OH alterations (montmorillonite, kaolinite) cluster near intrusive contacts; Mg-OH alterations (chlorite, epidote) occur at interfaces between carbonate sequences and concealed intrusions. Composite alteration anomalies exhibiting stacked mineral signatures (up to four distinct types) were identified across the region, demonstrating a strong spatial correlation with known mineralization centers. By integrating alteration zonation, structural lineaments, stratigraphy, geochemical anomalies, and orebody records, this study delineated four priority targets: Lijiaxiang Town, eastern Meixi Town, Miaoxi Town, and the central Moganshan Volcanic Basin. Full article

This study investigated the impact of recreational use on trails in the Atlantic Forest (Ubatuba Municipality, São Paulo State, Brazil) using physical, chemical and geochemical indicators. Five trails with different morphological characteristics were selected, and paired samples were collected from the trail surface (TR) and trail-side slope (TA). The statistical approach combined local analyses for each trail with global clustering (n = 19) using Student’s t-test, along with multivariate modeling through Principal Component Analysis (PCA) and Pearson correlation. The analysis included physical attributes (bulk density, particle size and porosity), chemical attributes (pH, organic matter and macronutrients) and geochemical compositions (major oxides and trace elements determined by XRF). The overall results reveal systematic compaction in the trail surface (TR), with bulk density increasing from 1.32 g/cm³ (TA) to 1.37 g/cm³ (TR) (p = 0.038), and total porosity decreasing from 47.26% to 45.34% (p = 0.016). In contrast, the geochemical oxide composition (SiO₂, Al₂O₃, Fe₂O₃) remained stable (p > 0.05), indicating the resilience of the mineral matrix. However, significant local dynamics (p < 0.05) in K₂O and MgO were observed in more preserved trails, associated with surface compaction and fragmentation of the litter layer, and phosphorus showed strong dependence on organic matter (r = 0.85). Multivariate analysis indicates that degradation is predominantly physical and micromorphological at the local scale, with bulk density and porosity being the most sensitive indicators for environmental monitoring. Full article

Slaughterhouse wastewater introduces potentially toxic elements into aquatic ecosystems, yet bioaccumulation patterns in commercial fish species and associated human health risks remain underexplored in West Africa. This study quantified zinc (Zn), lead (Pb), iron (Fe), magnesium (Mg), chromium (Cr), and cadmium (Cd) in three ecologically distinct fish species—Oreochromis niloticus (Nile tilapia), Clarias gariepinus (African sharptooth catfish), and Mugil cephalus (Flathead grey mullet)—from two slaughterhouse-impacted rivers (Transamadi and Mgbuosimini) and a control site (Iwofe) in Rivers State, Nigeria. Metal concentrations were measured using atomic absorption spectrophotometry. Two-way ANOVA assessed species and location effects. Principal component analysis (PCA) was performed, with Mg used as a potential geogenic tracer, as its loading pattern was independent of Pb and Cd and consistent with the natural background. A Water Quality Index (WQI) classified Mgboshimini and Iwofe as having poor water quality (WQI > 75), while Transamadi had medium quality. Health risks were evaluated using estimated daily intake (EDI), target hazard quotients (THQ), and hazard indices (HI) following USEPA guidelines. Metal levels varied significantly by species and location (p < 0.001). Flathead grey mullet from Mgbuosimini had the highest Pb (1.50 ± 0.05 mg/kg) and Cd (0.41 ± 0.02 mg/kg), exceeding EU maximum levels for fish muscle (Pb 0.30 mg/kg, Cd 0.05 mg/kg) by 500% and 800%, respectively. PCA explained 77.5% of the variance, with Pb and Cd clustering as anthropogenic sources, while Mg loaded independently. THQ for Pb approached unity in Flathead grey mullet (0.88), and THQ for Cd reached 0.97. HI exceeded 1.0 in all species from Mgbuosimini, peaking at 2.07 in Flathead grey mullet. Uncertainty analysis (using ±SD) gave a HI range of 1.89–2.25 for this species, all above the safety threshold. Carcinogenic risk for Flathead grey mullet (3.97 × 10⁻⁴) approached the upper acceptable limit. Slaughterhouse effluent appears to elevate Pb and Cd burdens in fish, with detritivorous Flathead grey mullet posing the highest health risk. Exceedance of safety thresholds and HI > 1.0 indicate potential non-carcinogenic and carcinogenic risks. We recommend improved wastewater treatment and species-specific consumption advisories. Full article

This paper investigates the magnetization reversal processes in spring-exchange magnetic composites featuring irregular, dendritic structures. A disorder-based cluster Monte Carlo method combined with a Diffusion-Limited Aggregation (DLA) algorithm was used to model a fractal-like soft magnetic phase (Fe) embedded in a high-coercivity hard matrix (Fe-Nb-B-Dy). A multiparameter analysis was performed by varying the soft phase volume fraction (10–30%), intergrain exchange coupling via contact bridges (25–100%), system scale factors (1–20), surface-to-volume anisotropy ratios (K_S/K_V = 1–20), and the degree of random anisotropy contribution (RAC = 0–100%). The simulations reveal that highly branched fractal structures enhance the interfacial contact area, which accelerates the nucleation of domain reversal driven by the soft phase, paradoxically lowering the overall coercivity compared to compact morphologies. Furthermore, a lack of easy magnetization axis coherent alignment triggers a cascading reversal mechanism through local “weak links”, severely degrading the coercive field from approximately 4.2 T to below 0.4 T in extreme cases (at 30% Fe, 25% coupling and high K_S/K_V ratio). These findings suggest potentially the most important factors and their impact that should be taken into account in the design and optimization of next-generation powder-sintered permanent magnets. Full article

The Heilongtai–Maogudui (HM) mafic intrusions are exposed in the southern margin of the North China Craton (SNCC), which are contemporaneous with a variety of strategic metal/non-metal minerals (niobium, uranium, and high-purity quartz) and magmatic hydrothermal REE deposits. New geochronology and geochemistry of these intrusions are examined and interpreted to decipher their petrogenesis and tectonic settings. Zircon LA–ICP–MS data formed a concordant cluster, yielding a mean ²⁰⁶Pb/²³⁸U age of 397.5 ± 3.5 Ma, which is interpreted as an Early Devonian crystallization age. The HM mafic intrusions have similar whole-rock geochemical compositions, containing 48.94–51.51 wt% SiO₂, 1.26–1.61 wt% TiO₂, 5.96–7.13 wt% MgO, and 11.00–12.48 wt% FeO_t. The total alkali contents range from 1.61 wt% to 3.53 wt%, with Mg^# values of 47.23–52.30. The petrographic and geochemical results suggest the fractional crystallization of mainly olivine, clinopyroxene, and minor Fe–Ti oxide in the mafic intrusions. Being of tholeiitic composition, these mafic rocks display relatively flat rare earth element (REE) and trace element patterns, which are similar to those of the normal mid-ocean ridge basalt (N–MORB) and the enriched mid-ocean ridge basalt (E–MORB). The HM mafic intrusions are proposed to originate in the continental extensional environment through 5–10% partial melting of the depleted spinel asthenosphere mantle source. This is attributed to the gravitational delamination of the lithospheric mantle and the upwelling of the hot asthenosphere, marking the end of the Paleozoic Proto–Tethyan orogenic cycle. The Paleozoic strategic mineral deposits are proposed to have formed under this specific tectonic regime. Full article

This study presents a field-validated, scenario-based two-layer dispatch framework for sustainable rural electrification, demonstrated at the Khlong Ruea hybrid microgrid (50 kW micro-hydro, 20 kWp PV, 48 kWh LiFePO₄ BESS, 48 kW diesel) in Chumphon Province, southern Thailand. The framework combines an offline mixed-integer linear program (MILP) with scenario-based uncertainty handling (k-medoid clustering, N = 8; CVaR penalty at α = 0.9) and an operator-assisted execution layer implementing source transitions via manual changeover switches. A Fluke 435 IEC 61000-4-30 Class-A field campaign with stationary block-bootstrap inference (B = 2000 resamples, 10 min blocks) documented substantial power quality improvements under BESS supply: the three-phase average THD-V reduced from 5.4% to 2.9% with 95% confidence intervals that do not overlap between the two supply modes; the THD-I dropped from 55.8% to 4.9% (Phase A; 91.2% reduction; three-phase average 64.0% → 7.8%); the voltage unbalance fell from 0.86% to 0.03%; and the displacement power factor improved from 0.92 to 0.95. IEEE Std 1459-2010 decomposition reveals that 93% of the non-fundamental apparent power under diesel supply is attributable to current-distortion volt-amperes (Dᵚ = 4737 VA vs. 283 VA under BESS). A composite power quality index confirms that diesel operation fails the IEEE 519-2022 current-distortion limits while BESS supply satisfies all EN 50160 and IEEE 519-2022 thresholds (PQI: 0.75 vs. 3.89). A 365-day closed-loop simulation confirmed an 18.4% reduction in annual operating cost and a 27.6% reduction in diesel runtime relative to a rule-based baseline, while maintaining LPSP at or below 0.53%. Techno-economic projection from field-verified HOMER inputs reduced the levelized cost of electricity from approximately 0.69 USD/kWh (diesel-only) to 0.36 USD/kWh for the proposed PV + BESS + Hydro + Diesel configuration, which retains diesel as a low-utilization backup at a near-100% renewable energy share. The same configuration delivered a 47.9% net present cost advantage over diesel-only operation and a 12.8 t (82%) annual CO₂ reduction. Manual source-transfer interruptions of 1–3 min are fully characterized, and a cost-estimated ATS + SCADA upgrade roadmap is defined. Full article

The electrochemical co-conversion of CO₂ and H₂O into valuable products is a promising approach toward carbon-neutral energy systems. Alloy exsolution from perovskite lattices has emerged as an effective strategy to engineer catalytic interfaces, yet the mechanistic influence of exsolved bimetallic species on CO₂/H₂O co-electrolysis remains insufficiently clarified. To address this gap, density functional theory (DFT) calculations were performed in this study to systematically examine how NiFe alloy clusters exsolved from the LSFNO (La_0.7Sr_0.3Fe_0.9Ni_0.1O_3-δ) (111) surface modify the electronic structure of the interfacial region and promote the RWGS reaction in CO₂/H₂O co-electrolysis. Our work highlights bimetallic alloy exsolution as a powerful strategy for improving co-electrolysis catalysts and offers valuable guidance for the rational design of next-generation high-entropy oxide systems. Full article

Ordered mesoporous carbons have emerged as versatile supports for Fischer–Tropsch catalysts due to their high surface area, tunable pore architectures, and chemical stability. However, the influence of active-metal identity on product selectivity within a common carbon framework remains insufficiently understood, particularly when Fe and Co are compared under rigorously identical conditions. To address this aspect, we prepared Fe- and Co-based catalysts with comparable nominal metal loadings supported on CMK-5 carbon material and evaluated their structural, surface, and catalytic properties. Comprehensive characterization revealed distinct metal-dependent behaviors, and catalytic testing between 423 and 598 K at 2 MPa showed that the catalyst CMK-5(Co10) exhibited substantially higher activity, whereas CMK-5(Fe10) provided a more stable product distribution and exclusively paraffinic C₂–C₃ products across the studied temperature range. In contrast, CMK-5(Co10) displayed a pronounced temperature-dependent selectivity, with increasing methane formation and the emergence of olefinic C₂–C₃ species at intermediate and high temperatures. Chain-growth probabilities were consistent with these trends. Complementary Density Functional Theory and Kinetic Monte Carlo analyses indicated stronger binding of carbonaceous intermediates on Fe clusters and more accessible C–C coupling pathways on Co clusters. Together, these results clarify how active-metal identity governs selectivity within a shared CMK-5 architecture and provide guidelines for designing carbon-supported Fischer–Tropsch catalysts with controlled product distributions. Full article

While viral diseases of domestic cats (Felis catus) can threaten the recovery of the European wildcat (Felis s. silvestris), their epidemiology in wildcat populations remains poorly understood. Here, we analyzed 428 road-killed wildcats from Western and Central Germany for the presence of antibodies/antigens of six feline viruses. The presence of at least one viral antigen or antiviral antibody was detected in 53.3% of the animals. Antibodies against feline parvovirus (FPV) showed the highest seroprevalence (29.2%), while feline leukemia virus (FeLV) antigens were detected in 22.2% of the animals. Antibodies to feline coronavirus (FCoV), feline herpesvirus (FHV) and feline calicivirus (FCV) were detected in 10% or fewer of the wildcats. No antibodies to feline immunodeficiency virus (FIV) were detected. FeLV antigens clustered spatially, with prevalence declining from southwest to northeast, consistent with the geographic expansion of the virus antigens. Seroprevalence of FPV and prevalence of FeLV increased with age, suggesting cumulative exposure, while juvenile males were particularly unlikely to be seropositive for FPV. Proximity to built-up areas did not predict seroprevalence for any virus. FeLV and FPV in particular warrant further investigation as potential threats to wildcat recovery in Germany and highlight the need for longitudinal health monitoring alongside existing conservation efforts. Full article

Shallow groundwater in the Dongting Lake area is an important resource for domestic, agricultural, and industrial use, and its quality is essential for regional sustainable development and public health. Therefore, effective protection of this resource is urgently needed. In this paper, we integrate Positive Matrix Factorization (PMF) and Self-Organizing Map (SOM) machine-learning algorithms to conduct an in-depth analysis of the distribution, sources, and risks of toxic elements in shallow groundwater along the southern shore of Dongting Lake. The results indicate that Fe and Mn in the groundwater of the study area are at a severe pollution level, while As is at a light pollution level. The model analysis identified four pollution sources: natural sources (Fe, Mn) accounting for 31.33%, agricultural production (Zn) for 18.96%, traffic-mining mixed source (Pb, Cu, Cd) for 32.67%, and mineral dissolution-redox driven (As) for 17.04%. The average concentrations of Fe and Mn exceeded the standard limits. Although the carcinogenic metal Cd did not pose a health risk, the health risk value of As exceeded the maximum acceptable level, which requires serious attention. The PMF model quantified four potential sources of toxic elements, while SOM was used as a complementary nonlinear clustering tool to examine the consistency of the PMF-derived source contribution patterns. The integrated PMF–SOM framework, together with spatial distribution and geochemical evidence, improved the interpretability and robustness of source identification. Full article

The Gulf Cooperation Council (GCC) countries consistently rank among the highest per capita CO₂ emitters globally, yet rigorous empirical analysis of the structural drivers of these emissions in the post-Paris Agreement era remains scarce. This study investigates the determinants of CO₂ emissions per capita across six GCC economies—Bahrain, Kuwait, Oman, Qatar, Saudi Arabia, and the United Arab Emirates—over the period 2015–2022, using pooled ordinary least squares (OLSs) and country fixed effects (FEs) panel regression models with country-clustered standard errors. The focal explanatory variable is energy use per capita, complemented by GDP per capita, trade openness, urbanization, foreign direct investment (FDI), and industry value added as controls. A quadratic income term explicitly tests the environmental Kuznets curve (EKC) hypothesis. Results consistently show that energy use is the dominant driver of emissions. The EKC hypothesis is supported in the FE framework. The implied turning point of approximately USD 85,500 per capita (constant 2015 USD) is already exceeded by Qatar (panel mean: USD 114,835) and approached by the UAE (USD 71,434), while Bahrain (USD 55,681), Kuwait (USD 51,531), Saudi Arabia (USD 61,232), and Oman (USD 38,591) remain on the EKC’s rising slope, consistent with their continued emissions’ growth trajectories. Urbanization exerts a significant positive within-country effect on emissions. Trade openness reduces emissions in cross-sectional specifications, while FDI is systematically insignificant. These findings support energy efficiency reforms, renewable energy expansion, and low-carbon urban planning as the most effective policy levers for GCC decarbonization. Full article

Iron-exchanged bentonites derived from a natural montmorillonite-rich clay (Taganskoe deposit, Kazakhstan) were prepared through a simple aqueous ion-exchange route using Fe(II) or Fe(III) inorganic salt precursors, yielding final Fe contents of ca. 5–7 wt.%, while preserving the smectite layered framework. A mild thermal treatment under air was applied to tune iron coordination without triggering major structural collapse. The resulting materials were characterized by ED-XRF, PXRD, FE-SEM/EDX, DLS/ζ-potential and DR UV–Vis–NIR spectroscopy, revealing predominantly exchanged Fe species with a limited fraction of surface iron-oxide clusters, whose contribution increases after activation. Structure–reactivity relationships were probed under mild conditions in liquid-phase ethyl acetate using dimethyl methylphosphonate (DMMP) and 2-chloroethyl ethyl sulfide (2-CEES) as organophosphorus and organosulfur hazardous chemicals and chemical warfare agent simulants, respectively. Fe(III)-bentonite enabled very fast DMMP removal (ca. 93% within 0.5 h) with a remarkable improved performance with respect to Fe(II)-bentonite and the pristine mineral clay. For 2-CEES, the presence of H₂O₂ markedly enhanced oxidation on Fe-containing clays, reaching quantitative abatement within 24 h (up to >90%), with strong retention of oxidized sulfur products by the clay matrix. These results highlight Fe-exchanged natural bentonites as robust, cheap and multifunctional adsorption/catalytic solids for decontamination and water-treatment applications. Full article