Search Results (1,672)

This study investigates the spatiotemporal distribution of heavy metals in urban soils of Thessaloniki, Greece, over a four-year monitoring period (2021–2024). A total of 664 soil samples were collected across diverse land-use types during both wet (winter) and dry (summer) seasons. Soil physicochemical properties were analyzed alongside cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn) concentrations. The results reveal distinct, element-specific accumulation dynamics driven by continuous anthropogenic inputs. Statistical and geospatial analyses confirm that Cd exhibits a highly significant, progressive accumulation and spatial expansion toward residential areas. In contrast, Cu and Pb demonstrate a gradual, chronic enrichment, eventually reaching a saturation point where winter precipitation is insufficient to offset summer deposition. Zn presents as a severe but temporally stable contamination burden, anchored to the northwestern industrial–port sector. Furthermore, the alkaline properties of the local urban soils were found to act as an effective sink, immobilizing contaminants and preventing downward leaching. The Geo-accumulation Index (I_geo) confirms a progressive decline in soil quality driven primarily by cadmium, while the other trace elements exhibit persistent, stable profiles. Overall, this study establishes a vital geochemical baseline of total heavy metal loading in Mediterranean urban soils, emphasizing the need for targeted emission controls and future mobile-fraction assessments to guide sustainable urban management. Full article

The persistence of antibiotics like ciprofloxacin (CIP) in aquatic environments necessitates the development of efficient, low-cost wastewater treatment technologies. This study investigates a low-temperature fabrication strategy for mixed-phase copper oxide (CuO/Cu₂O) coatings synthesized via co-precipitation and immobilized using electrophoretic deposition (EPD). A critical finding was that a 25 min precursor aging time (T25) preserved a metastable mixture of CuO and Cu₂O phases, which is highly advantageous for creating heterojunction interfaces that enhance charge separation. In contrast, extended aging (T35) promoted phase consolidation toward bulk CuO, reducing catalytic surface area. During the EPD process, applied voltage acted as an influence to the relative phase composition and deposition behavior of the deposited coatings; 1.0 V was identified as the optimal condition, balancing high phase fidelity with enhanced crystallinity (average crystallite size of 30.6 nm) and mechanical stability. Photocatalytic experiments demonstrated significant CIP degradation, with the 0.9 V and 1.0 V films outperforming the 1.2 V film, possibly due to more favorable surface chemistry and phase diversity. While the 0.9 V film achieved the highest mineralization efficiency (18% TOC removal), the 1.0 V film offered the best balance between photocatalytic activity, structural stability, and phase selectivity for practical applications. High-Performance Liquid Chromatography-Mass Spectrometry HPLC-MS analysis suggested that degradation proceeds through oxidative pathways involving piperazine ring cleavage and defluorination. Full article

Seasonal freeze–thaw processes affect soil hydrothermal conditions in high-altitude valleys, yet evaluations based only on air temperature or maximum freezing depth may overlook the distinction between surface-connected freezing and delayed thawing within the soil profile. Meteorological conditions, ground surface temperature (GST), ground-temperature profiles, freezing depth, and volumetric water content (VWC) were continuously monitored in an arid valley on the Qinghai–Tibet Plateau. Mean annual GST was 3.23 °C higher than mean annual air temperature, and the freezing and thawing n-factors were 0.72 and 1.54, respectively, indicating weakened cold accumulation and enhanced heat accumulation at the ground surface. The maximum surface-connected freezing depth reached 3.30 m, whereas ground temperatures at 3.5 m and below remained above 0 °C. During spring thawing, a residual frozen layer persisted for 49 days after the shallow layer had thawed, with a maximum thickness of 3.24 m. GST-based freezing degree days represented freezing depth better than air-temperature-based freezing degree days. Soil VWC remained low, and precipitation responses were mainly confined to 0.2 m depth. These findings reveal a thermally dominated freeze–thaw regime with weak deep moisture response and show that distinguishing surface-connected freezing from residual frozen layers improves hydrothermal-state identification in low-water-content sandy gravel deposits. Full article

Metallurgical slags produced in the zinc–lead, copper, iron and steel metallurgical industries are characterized by a variety of technical parameters and varying chemical and mineral compositions, which depend on the type of raw material and the technological process selected and its workflow. These slags are characterized by a high content of valuable elements, including Cu, Pb, Zn, and Fe, which form complex multiphase conglomerates. In the chemical composition of Zn-Pb smelting slags, the contents of the dominant elements, i.e., Fe, Zn, and Pb, range from a few to several dozen %. These elements occur mainly in the form of polyphase oxides and silicates. The chemical composition of Cu smelting slag contains up to a few % Cu and up to several dozen % Fe, with these elements mainly forming silicates and sulphides. Iron and steel metallurgy slag contains up to several dozen % Fe, which occurs mainly in the form of silicates, oxides, and spinels. Due to their phase composition, metallurgical slags stored in landfills can have a negative impact on the environment. The phase composition of slags is one of the main factors determining their behavior in a weathering environment, i.e., their ability to release metals when exposed to atmospheric factors such as precipitation or temperature. On the other hand, such high concentrations of elements in metallurgical slags mean that they become anthropogenic deposits, and the phase composition of the slags determines how the deposited slags are processed. The aim of this article is to present the mineralogical and chemical characteristics of Zn, Pb, Cu and steel metallurgical slags deposited in landfills, along with an assessment of these materials as a source of secondary raw materials. Full article

Turbidite sandstones of the Chang 6 member and delta-front sandstones of the Chang 8 member in the Yuele Block, southwestern Yishan Slope, Ordos Basin, serve as the primary tight oil reservoirs. In this study, a total of 243 continuous core samples from multiple wells were collected for integrated analyses, including cast thin-section observation, scanning electron microscopy (SEM), X-ray diffraction (XRD) of clay minerals, routine core physical property measurements and mercury intrusion porosimetry (MIP), to systematically compare sedimentary–diagenetic disparities between semi-deep lacustrine turbidites (Chang 6) and delta-front sandstones (Chang 8). Measured data indicate that the two intervals have similar average porosities of 9.27% and 9.88%, while their respective geometric mean permeabilities differ markedly, with values of only 0.142 × 10⁻³ μm² for Chang 6 and 0.260 × 10⁻³ μm² for Chang 8. Micro-pore-throat size and connectivity dominate reservoir fluid flow capacity, and total porosity alone cannot objectively evaluate reservoir quality. Delta-front sandstones of the Chang 8 member are supplied by a proximal magmatic-rich provenance from the southwest, and widespread grain-coating chlorite forms during early diagenesis, effectively mitigating compaction damage and inhibiting quartz overgrowth, leading to well-preserved primary pores. As mixed-provenance deposits lacking protective chlorite rims, Chang 6 turbidites experience more intensive compaction, and abundant fibrous illite and carbonate cements precipitate in the subsequent diagenetic stage to fill and separate pore throats, forming an isolated micropore network. Quantitative comparison with baseline parameters of the Longdong region reveals that the Yuele Block is located closer to the southwestern sediment source, resulting in higher contents of magmatic lithics and chlorite in Chang 8 as well as elevated illite concentrations in Chang 6 relative to regional averages, which verifies that source-to-sink transport distance regulates reservoir quality by driving the differentiation of clay mineral assemblages. A complete quantitative coupling sequence of “provenance supply–authigenic clay mineral-pore evolution” is defined herein, and two distinct sedimentary–diagenetic evolutionary routes are classified: high-quality delta-front reservoirs protected by grain-coating chlorite, and low-quality turbidite reservoirs blocked by illite–carbonate cements. This research refines the diagenetic differentiation rules for continental tight sandstones with diverse sedimentary origins in the Ordos Basin and provides quantitative mineralogical criteria for identifying tight oil sweet spots in proximal provenance blocks. Full article

Rainwater harvesting is increasingly recognized as a sustainable supplement to conventional water supplies and a strategy to improve water resilience. However, harvested rainwater may contain organic and inorganic contaminants introduced by atmospheric deposition and contact with collection surfaces, requiring adequate treatment before safe use. This review critically evaluates the application of adsorbent materials for harvested rainwater treatment, namely carbon-based materials, surface-modified mineral matrices, and biosorbents. The available literature was analyzed considering adsorbent characteristics, treatment conditions, removal performance, and the mechanisms potentially governing contaminant removal. The reviewed studies demonstrate that activated carbon is the most investigated adsorbent class, while surface-modified minerals and biosorbents remain less explored. Direct comparison between studies is limited by differences in experimental conditions and incomplete characterization of adsorbent properties. Adsorption performance depends on both adsorbent characteristics and rainwater chemistry, particularly pH, which affects surface charge and the aqueous speciation of many contaminants. Reported removal efficiencies do not always reflect adsorption alone, as treatment configuration and operating conditions may also promote precipitation, physical retention, and in some cases, biologically mediated degradation. Future research should prioritize standardized material characterization, mechanistic evaluation, regeneration strategies, and long-term validation to support the development of more predictable and reproducible rainwater treatment technologies. Full article

Magnetite (Fe₃O₄) nanoparticles have been explored for biomedical applications. Their surface behavior in physiological-like environments has not been fully established. Fe₃O₄ nanoparticles obtained by chemical co-precipitation were exposed to simulated body fluid (SBF) for up to 28 days, and in vitro bioactivity was examined. Structural and surface changes were investigated using XRD, FTIR-ATR, SEM/EDS and thermal analysis, while pH and electrical conductivity measurements were used to monitor changes at the particle–solution interface. Magnetite was the main crystalline phase, and the main crystalline structure was preserved during SBF exposure within the detection limits. Progressive surface transformations occurred, including hydration/hydroxylation and formation of calcium–phosphate-containing surface deposits. Changes in pH and variations in electrical conductivity were interpreted as complementary indicators of interfacial processes. Cytotoxicity tests on L929 fibroblast cells showed that Fe₃O₄_14SBF was well tolerated at 25–50 µg/mL, whereas higher concentrations reduced cell viability. These findings suggest that Fe₃O₄-based magnetic materials may be further considered for biomedical applications, provided that concentration-dependent cytocompatibility is considered. Full article

Magnesium alloys are promising candidates for biomedical implants, but their rapid corrosion limits clinical use. Simulated body fluid (SBF) is commonly used to evaluate corrosion behaviour; however, Ca-P and carbonate deposits can mask the intrinsic performance of protective coatings. Tris(hydroxymethyl)aminomethane (Tris) has been proposed as an SBF modifier, although its effect on coated magnesium remains poorly understood. While Tris modifies the buffering characteristics of the solution, it also alters the stability of Mg(OH)₂ and the precipitation equilibria of corrosion products, resulting in more aggressive corrosion conditions than standard SBF. Here, the corrosion behaviour of AZ31 alloy, a plasma electrolytic oxidation (PEO) coating, and a sol-gel sealed PEO coating was investigated in SBF with and without Tris. Electrochemical impedance spectroscopy, immersion tests, pH monitoring, and post-immersion SEM/EDS analyses were used to evaluate coating performance under physiological and aggressive conditions. The results show that AZ31 and PEO coatings exhibit higher apparent corrosion resistance in SBF without Tris due to corrosion-product stabilization and Ca-P-rich deposits that partially block electrolyte access. In contrast, SBF with Tris accelerates degradation, causing uniform corrosion of AZ31 and premature PEO failure through electrolyte penetration and coating cracking. The PEO-AR/ZTP system maintains the highest electrochemical resistance and the best protective performance in both media. Full article

The formation and disappearance of paleolakes are sensitive indicators of environmental evolution in arid and semi-arid regions. Their disappearance records comprehensive information on regional hydrological conditions, climatic changes, and tectonic activities, thereby offering unique research value for elucidating the environmental driving mechanisms behind water resource changes in historical human settlements and the concomitant rise and fall of civilizations. This study analyzed the contact interface between extensively distributed lacustrine deposits and the overlying aeolian dune sands around Tongwan City using optically stimulated luminescence (OSL), and combined with relevant documentary evidence to elucidate the relationship between paleolake disappearance and the abandonment of the ancient city. The OSL dating results demonstrated that the disappearance of paleolakes and the initiation of desertification around Tongwan City were mainly concentrated between about 1200 and 900 years before present, closely corresponding to the abandonment of Tongwan City in AD 994. Field investigations additionally revealed that well-developed fluvial erosion surfaces are pervasively present at the top of lacustrine deposits around Tongwan City, while multiple fluvial terraces are exposed along the Wuding River. These features collectively indicate that regional crustal uplift event led to fluvial incision. The results indicated that the abandonment of Tongwan City was not attributable solely to climatic aridification, but instead resulted from the combined influences of favorable hydrothermal conditions during the High-Temperature Period of the Northern Song (HTNS, AD 994–1094) and regional tectonic uplift. Tectonic uplift facilitated deep incision of the Wuding River valley, while increased precipitation during the warm period enhanced surface water infiltration and drainage, resulting in a significant decline in groundwater levels, the disappearance of paleolakes, and ultimately the depletion of water resources upon which the ancient city relied. These findings provide new evidence from an environmental geological perspective and present a key scientific explanation for the paradox that Tongwan City was abandoned during a relatively warm climatic interval. Furthermore, the coupled mechanism of tectonic uplift, fluvial incision, sharp groundwater decline, and societal collapse revealed in this study not only provides a valuable reference for investigating the abandonment of ancient cities in arid and semi-arid regions during historical periods, but also offers important implications for assessing water resource vulnerability of ancient settlements on analogous geomorphic units under global climate change, and may serve as a geological–historical warning and reference for water security management in human habitations under current and future warm-climate conditions. Full article

AlCoCrFeNi-based high-entropy alloys have garnered significant attention for high-end applications in aerospace, marine engineering, and the nuclear industry due to their exceptional comprehensive properties, including high strength and good corrosion resistance. However, their widespread application is critically hindered by a fatal disadvantage: poor ductility. Optimizing the ductility of this alloy system has therefore become a key research priority. Optimizing their ductility has emerged as a key research priority in recent literature. This review systematically examined the influences of diverse fabrication techniques on the mechanical properties, particularly ductility, of these alloys. Melting routes (vacuum arc melting and vacuum induction melting), powder consolidation (spark plasma sintering and hot pressing), and additive manufacturing (selective laser melting, laser melting deposition, electron beam melting, and wire arc additive manufacturing) were covered in this review. This review underscores that while each fabrication route offers distinct advantages, future breakthroughs require multi-process hybridization, data-driven optimization, and precise control of precipitation kinetics to overcome the strength–ductility trade-off and enable large-scale applications of AlCoCrFeNi-based HEAs. Full article

In the Western Anti-Atlas, the stratiform copper mineralisations of the Tabia Member are distinctly hosted within sedimentary rocks, forming deposits comparable to the sediment-hosted stratabound copper (SSC) type. In Tizert, Ouarmdaz, and Talat n’Ouamane, the sandstones and clays host primary sulphides as disseminations and copper carbonates occurring as small continuous or lenticular beds, small geodes, and coatings on clay laminations. In Tiferki, the conglomerates are more mineralised; sulphides are represented by chalcopyrite and bornite, locally altered into chalcocite. Copper carbonates appear as malachite and azurite coating pebbles and deeply impregnate the granular matrix. From a sedimentological and sequence-stratigraphic perspective, the conglomeratic level at Tiferki represents a low-sea-level prism (LST) formed during a stage of maximum platform exposure allowing erosion products to accumulate at the base of the slope. By contrast, the silty–sandy complex known as the “Talat n’ Ouamane level” corresponds to a prograding sedimentary sequence (Highstand Systems Tract, HST) that developed after a relative regression where the platform was only partially exposed. In both cases, relative sea-level fall promoted the emergence of the hinterland and active erosion, supplying the depositional environment with coarse detrital during the maximum drops in sea level and sandy-to-micro-conglomeratic deposits during less pronounced regressions. This detrital supply probably brought copper in the form of grains and especially dissolved copper, which is largely deposited at the bottom of slopes and in marine environments where microbial communities contribute to the precipitation of copper. The selective distribution of sulphides within the Tabia Member shows that only the low-sea-level and high-sea-level prisms are enriched in stratiform copper, while the transgressive and maximum flooding systems tracts lack significant mineralisation. This suggests that sea-level variations played a controlling role in copper deposition. The regressive trend of the high sea-level suite continued until emergence, reflected by the invasion of the environment by red or ochre siltstones from the alluvial plain. The emergence at the transition from sandstones to dolomites, and the “Red Beds”-type mineralisation embedded in these subaerial facies, support the syngenetic origin of the sulphides in the Tabia Member. After this main emplacement of stratiform copper, the sulphides would have undergone remobilisation and alteration during a significant episode of vertical water escape that deformed the host facies and enhanced mineral concentration within permeable sandstones. Even the clays were delaminated and coated with a thin films of copper carbonates on their surfaces. In the Tamjout dolomites, carbonates are percolated by acidic solutions, contributing to the brecciation and silicification of the stromatolitic layers. Copper mineralisation accompanies this silicification and fills the karstification pockets. Full article

Gold-vein deposits of the Nazca–Ocoña belt constitute an important economic resource for small- and medium-scale mining in Peru. However, the mineralogical and physicochemical controls governing gold distribution in these veins remain poorly understood. This study presents an integrated analysis of the Millonaria vein, San Juan de Chorunga, aimed at establishing the paragenetic sequence, characterizing the mode of occurrence of gold, and reconstructing the evolution of the hydrothermal fluids. Petrographic, ore microscopy, scanning electron microscopy, fluid inclusion microthermometry, and Au fire-assay data were integrated. The results indicate a main mineralizing stage, in which gold precipitated mainly in fractures and interstices of pyrite I and, subordinately, in microcavities within quartz I, as anhedral aggregates of native gold and electrum (Au ≈ 80%, Ag ≈ 20%). Specularite was also identified in fractures and interstices of pyrite I. A post-mineral substage I, characterized by milky quartz, carbonates, and subordinate sulfides, was also recognized, without significant gold precipitation. Fluid inclusions record homogenization temperatures of ~180–350 °C and low- to intermediate-salinity fluids (0.8–7.86 wt.% NaCl eq.). The data suggest at least two thermal contexts for gold mineralization, possibly influenced by dilution/mixing, local cooling, and redox changes. Full article

Paraffin wax precipitation and deposition significantly hinder crude oil production and transportation by reducing flow efficiency, increasing operational downtime, and requiring costly remediation procedures. Conventional wax mitigation methods commonly rely on environmentally unfriendly chemicals and energy-intensive thermal or mechanical treatments. This study investigates the use of a natural polymer from Swietenia macrophylla (Mahogany), modified with metal nanoparticles (MNPs), namely silver oxide (Ag₂O), zinc oxide (ZnO), and silver-doped zinc oxide (Ag-ZnO), for petroleum wax inhibition. Material characterization was conducted using FTIR, TGA and GC-MS analyses, while performance evaluation employed rheological measurements, Cross-Polarized Microscopy (CPM), and pour point testing. GC-MS analysis revealed the presence of oxygenated fatty acid esters such as glycidyl oleate (59.61%) and glycidyl palmitate (16.86%). These compounds indicate the presence of hydrocarbon-compatible and surface-active constituents beneficial for wax crystal modification. FTIR spectra further confirmed carbonyl, aliphatic hydrocarbon, and ether functionalities associated with natural wax-mitigation compounds and effective MNP binding sites. The application of 2 wt% polymeric materials demonstrated significant wax inhibition performance. The unmodified polymer reduced the activation energy (Ea) for crude oil flow by 49.4 kJ·mol⁻¹ from the virgin crude oil value of 213.6 kJ·mol⁻¹. The polymer + ZnO formulation achieved the highest pour point reduction of 1.72 °C, while polymer + Ag-ZnO recorded the greatest viscosity reduction of 77.1% at 1 s⁻¹ and 91.6% at 200 s⁻¹. This study demonstrates, for the first time, the potential of Swietenia macrophylla-derived nanocomposite polymers as sustainable and effective wax mitigation agents for waxy crude oil systems. Full article

During the production of high-sulfur-content gas–water wells, elemental sulfur saturated in natural gas gradually precipitates as solid particles with decreasing wellbore temperature and pressure. When these sulfur particles cannot be continuously carried upward in the gas–liquid–solid three-phase flow formed with natural gas and formation water, they tend to deposit in the wellbore, potentially blocking the production string and even severely restricting the gas well’s deliverability. Current research on predictive models for the critical gas flow velocity required to carry sulfur particles remain inadequate. Therefore, accurately predicting this critical velocity and adjusting production to prevent deposition are crucial for managing high-sulfur gas wells. The primary innovation of this study lies in the development of a predictive model for the critical gas flow velocity required for sulfur particle entrainment. Grounded in the “gas–liquid coalescence–liquid film entrainment” coupling mechanism revealed by preliminary experiments, this model is established through a mechanical analysis of sulfur particles within liquid films in vertical and inclined pipes. Recognizing liquid film thickness and velocity as pivotal parameters for model solving, auxiliary models for predicting these two parameters in inclined pipe annular flow were developed based on experimental results and the momentum balance principle. The proposed model comprehensively incorporates factors such as well inclination angle, pipe diameter, liquid flow rate, and sulfur particle size, rendering it applicable to diverse well configurations including vertical, horizontal, and deviated wells. Evaluation against 48 sets of experimental data yielded a Mean Absolute Percentage Error (MAPE) of 2.28%, demonstrating high predictive accuracy. Furthermore, an engineering calculation program for the critical gas flow velocity was developed. A case study involving a well in the Puguang Gas Field was conducted to predict and diagnose sulfur deposition conditions, thereby verifying the model’s practical utility. This research provides a scientific basis for the safe and efficient development of high-sulfur gas fields. Full article

Lead and zinc mineralization have been documented in low-temperature Mississippi Valley type (MVT), Volcanogenic Massive Sulfide (VMS), and high-temperature porphyry and skarn ore deposits. These deposits are characterized by the precipitation of galena (PbS) and sphalerite (ZnS) from a saline hydrothermal fluid. The direct relationship between metal concentration and the total chloride of the fluid has been documented previously; however, the role of acidity has not been studied extensively. Experiments were conducted in René 41 cold-seal pressure vessels at temperatures of 200, 300, and 500 °C and a pressure of 100 MPa to provide better constraints on the formation of galena and sphalerite in hydrothermal systems spanning a range of fluid acidities (pH). The concentrations of Pb and Zn in the synthetic hydrothermal fluids were determined at galena and sphalerite saturation as a function of HCl and at a total chloride of 15 wt.% NaCl_eq.. Zn concentrations ranged from 1.7 (±0.3) × 10² µg/g at 200 °C and an HCl concentration of 2.28 × 10³ µg/g to 2.55 (±0.5) × 10³ µg/g at 500 °C and an HCl concentration of 3.40 × 10⁴ µg/g. Pb concentrations were 1.8 (±0.4) µg/g at 200 °C and a HCl of 2.28 × 10³ µg/g and increased to 7.93 (±1.5) × 10³ µg/g at 500 °C and a HCl concentration of 3.40 × 10⁴ µg/g. Zn/Pb mass ratios in the fluids at sphalerite and galena saturation decreased with increasing temperature. The experimental data demonstrate that the concentration of Pb and Zn in the fluid increase with both temperature and HCl concentration and, consequently, decrease with increasing pH. These results demonstrate that acidic fluids can transport substantially greater concentrations of Pb and Zn than neutral or basic fluids. Experimentally determined slopes of Pb and Zn concentrations as a function of HCl in the fluid provide empirical measurements of the apparent dependence of metal solubility on HCl at a constant total salinity. These results are consistent with Pb and Zn being transported predominantly as chloride-complexes under acidic, although the experiments do not directly determine aqueous metal speciation. Consequently, the experimentally determined HCl dependencies should be interpreted as empirical measures of apparent metal solubility rather than direct measurements of speciation or ligand coordination. The observed dependence of dissolved metal concentrations on HCl likely reflects the combined effects of chloride complexation, increasing HCl association with increasing temperature, non-ideal solution behavior, and changes in the distribution of dissolved chloride- and possibly sulfur-based complexes. Therefore, the neutralization of an acidic Pb- and Zn-bearing, chloride-rich hydrothermal fluid could produce substantial galena and sphalerite mineralization if sufficient reduced sulfur is available. In hydrothermal fluids depleted in reduced sulfur, H₂S must be supplied through sulfate reduction or by mixing with an H₂S-rich fluid to promote galena and sphalerite precipitation. Full article