Search Results (957)

This three-year case study integrated the results of annual soil-monitoring campaigns conducted in 2022–2024 at 17 predefined locations within and immediately surrounding the Morava Thermal Power Plant Complex, Serbia. We analyzed surface soil samples (0–30 cm) for physical and chemical properties, metals and metalloids, and selected organic pollutants. Contaminant concentrations were evaluated relative to national regulatory thresholds, while potential ecological risk and outdoor worker human health risk were assessed using the potential ecological risk index (RI), Hazard Index (HI), and total carcinogenic risk (TCR). Soil properties and total contaminant concentrations varied considerably among the monitored locations. Regulatory classification identified Ni and Cd as the most widespread concerns. Ni exceeded the applicable limit value at all 17 locations in each campaign, including three remediation-value exceedances in 2022 and one in 2024. Cd exceeded the limit value at 17, 11, and 16 locations in 2022, 2023, and 2024, respectively, without exceeding the remediation value. RI ranged from 210.02 to 963.08, indicating moderate to very high potential ecological risk, and was driven primarily by Cd and Hg. Aggregate HI values ranged from 0.211 to 0.484 and remained below the screening threshold of 1 at all locations. In contrast, TCR ranged from 5.98 × 10⁻⁵ to 2.12 × 10⁻⁴ and exceeded the target benchmark of 1 × 10⁻⁶ at every location in all three campaigns. Arsenic accounted for more than 94% of TCR, while the conservative estimate obtained by applying Cr (VI) toxicity parameters to total Cr represented the principal secondary contribution. The different assessment approaches identified distinct contaminant priorities and therefore provided complementary rather than interchangeable information. The results support continued monitoring, targeted investigation of locations with elevated regulatory or risk indicators, direct chromium-speciation analysis, and integration of soil monitoring with groundwater, drainage-water, bioavailability, and effect-based assessments to support future reclamation and environmental management. Full article

Ni-based catalysts supported on kaolin were synthesized via solution combustion synthesis and promoted with Fe and/or La to investigate their catalytic performance in CO₂ methanation. Catalytic tests showed that Fe significantly improved CO₂ conversion from approximately 52% for Ni-catalyst to 83% for Ni2.5Fe_SCS at 300 °C. However, the promotional effect of Fe showed only a weak dependence on its loading, with Ni modification already being achieved at the lowest Fe content. Among all investigated catalysts, the La-promoted sample exhibited the highest CO₂ conversion (85% at 300 °C), owing to the formation of highly dispersed Ni⁰ crystallites, enhanced surface basicity, and strong metal–support interactions. These interactions also effectively suppressed particle sintering during prolonged stability tests. In contrast, simultaneous promotion with Fe and La did not provide additional catalytic enhancement, indicating that the effects of both promoters were not simply additive. Full article

Upon entering aquatic ecosystems, coal fly ash (CFA) particles and their leachates distribute across all environmental compartments, from surface water to benthic sediments, rendering them accessible to aquatic organisms spanning multiple trophic levels. Although CFA is widely classified as non-hazardous waste, a growing body of toxicological evidence demonstrates its capacity to induce significant adverse biological effects. This discrepancy between laboratory-demonstrated toxicity and its current non-hazardous regulatory status highlights a critical knowledge gap in risk assessment frameworks and testing philosophies. Herein, we provide a comprehensive review of CFA characterization techniques, leaching methodologies and their environmental relevance, and the aquatic ecotoxicity of both particulates and leachates to primary, secondary, and tertiary consumers. Based on the findings from the review, we propose four paradigm shifts to more accurately characterize CFA ecotoxicological risks: from standardized leaching protocols to application-specific and maximum leachability tests, from single-species assays to multi-trophic-level bioassays, from single-metal analysis to comprehensive, whole-matrix testing that integrates particulate and dissolved fractions, and from standardizing the reporting of CFA provenance, coal types, and combustion conditions to meaningful meta-analyses and cross-study comparisons. It is believed that these suggestions will substantially advance the realistic ecotoxicological assessment of CFA and bridge the gap between laboratory toxicity data and regulatory classification. Full article

Madinah, Saudi Arabia, is a hot-desert pilgrimage city receiving millions of religious visitors annually, yet its fine particulate matter (PM_2.5) has not been chemically characterized. The city whose population is periodically influx by millions of religious visitors, generating concentrated increases in vehicular activity while simultaneously exposing a large transient population to ambient air pollution. Despite this, its fine particulate matter (PM_2.5) has not been chemically characterized. Twenty-four-hour PM_2.5 samples were collected at five urban sites between December 2014 and February 2016 and analyzed for black carbon, water-soluble inorganic ions, and trace elements; sources were resolved by enrichment factors and positive matrix factorization (PMF), and screening-level inhalation risks estimated for eight PM_2.5-bound metals. Site means ranged from 37.7 ± 20.5 µg m⁻³ at Uhad to 103 ± 50.7 µg m⁻³ at Al-Awali, exceeding the World Health Organization 24-h guideline of 15 µg m⁻³ at all sites in every season. Observed site–cycle means ranged from 37.7 ± 20.5 µg m⁻³ at Uhad to 103 ± 50.7 µg m⁻³ at Al-Awali, with concentrations exceeding the World Health Organization 24-h guideline of 15 µg m⁻³ across the monitored site–cycle datasets. Reconstructed mass was dominated by organic matter (53–80.5%) and crustal material (15–53%). Sulfate was the dominant water-soluble ion, but secondary inorganic aerosols contributed only 1–22% of mass, resembling rapidly urbanizing arid cities rather than Asian or European megacities. PMF resolved five sources: crustal dust, industrial mixed dust, oil combustion, vehicular emissions, and secondary aerosols. Hazard quotients remained below unity and cumulative carcinogenic risks below 10⁻⁶, principally from chromium and nickel. Because these measurements precede the Vision 2030 urban-transformation program, they establish a chemically resolved reference state for evaluating future air-quality change in Madinah. Full article

Underground coal mining operations remain significantly threatened by the accumulation of methane (CH₄) and carbon monoxide (CO): Methane poses an acute explosion risk, and carbon monoxide serves as a critical biomarker for spontaneous coal combustion. Consequently, rigorous real-time monitoring to ensure environmental safety is necessitated, which is based on superior gas sensor devices. Although various detection modalities exist, conventional methods are frequently constrained by environmental sensitivity and limitations regarding long-term sensor stability. This review provides a comprehensive analysis of recent advancements in chemiresistive gas sensors based on metal oxide (MO) semiconductor materials with low cost, high stability, high sensitivity, and easy preparation, which are engineered for the detection of methane and carbon monoxide in coal mining environments. This study examines the redox-sensing mechanisms of both n-type and p-type MO semiconductors, for which special attention is directed toward optimization strategies designed to overcome the high activation energy of methane and improve carbon monoxide response kinetics. Importantly, novel approaches to lower high operating temperatures and improve the selectivity of MO sensors under complex mine environments have been comprehensively discussed. Full article

Laser powder bed fusion (LPBF) enables fabrication of complex bimetallic structures, such as combustion chambers, that require a thermally conductive internal liner supported by a high-strength structural jacket. Inconel 625 (IN625) served as the substrate, with GRCop-42, a Cu-Cr-Nb alloy developed by NASA Glenn Research Center, deposited with varying laser powers and laser scanning speeds to create the IN625–GRCop-42 interface. Hot isostatic pressing (HIP) was performed to evaluate defect mitigation, and Vickers microhardness testing was conducted to assess the mechanical properties across the bimetallic interface. Microstructure characterization revealed porosity across the full processing window and, along with density measurements, we were able to establish that the HIP treatment was unsuccessful in eliminating the defects, indicating that densification is primarily achieved by LPBF process optimization. Microhardness testing showed that the as-printed samples showed higher microhardness values than the as-HIPped samples due to the fine microstructure, high dislocation density and residual stresses caused by the LPBF process. The decrease in microhardness following HIP suggests that recrystallization, grain coarsening and residual stress relief may have occurred during post-processing. These results highlight the importance of LPBF process optimization in achieving strong, thermally stable IN625–GRCop-42 bimetallic interfaces. This study investigates the microstructural and mechanical behavior of the IN625 and GRCop-42 dissimilar metal interfaces fabricated using the LPBF process and the effects of HIP on the bimetallic microstructure. Full article

This study reports a combined morphological, surface chemical, and mineralogical characterization of fine particulate matter (PM_2.5) collected at three coastal sites—Northern (Abhour), Middle (Alhamraa), and Southern (Alkhomra)—in Jeddah, Saudi Arabia, during the summer (15 June–15 September 2017). The work complements a companion trace-element study of the same campaign by adding scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS/EDX mapping), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD), thereby linking bulk concentrations to particle morphology, surface oxidation state, and crystalline phase. Mean PM_2.5 concentrations were 22.2, 18.9, and 14.2 µg m⁻³ at the North, Middle, and South sites, respectively. Because samples were collected on borosilicate glass-fibre filters, the SEM images are dominated by the intrinsic fibrous matrix of the substrate; the collected aerosol is resolved as discrete sub-micrometre particles and agglomerates decorating the fibres, and the morphological interpretation is framed accordingly. XPS confirmed that surface metals (Fe, Al, Ca, and traces of Pb, Cu, Zn) occur predominantly in oxidized states, with the Middle urban site showing the strongest Fe and Pb signals. XRD identified quartz, calcite, gypsum, hematite/magnetite, and aluminum oxides, with additional Pb and Cu phases at the Middle and South sites. Principal component analysis (PCA) resolved four sources—mixed marine–crustal, terrigenous/industrial (Fe–Ti–Mn), oil combustion and shipping (V–Ni–Cu), and combustion/legacy-traffic (Pb–Zn)—consistent with prior Jeddah and Red Sea studies. The integrated approach provides surface-speciation and mineralogical details not available from bulk elemental analysis alone and establishes baseline information relevant to source management and health-risk assessment in arid coastal cities. Full article

Multi-component solid waste combustion can recover energy and reduce the difficulty of waste classification, but variable solid composition complicates the reduction of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), which has been paid attention to by the international community. Therefore, this paper comprehensively elaborates on the application characteristics of multi-component solid waste, analyzes the current situation of its source-controlling of generation and emission, and summarizes the source inhibition of PCDD/Fs emission and the research methods of PCDD/Fs in terms of three aspects: PCDD/Fs degradation technology, quantum chemical analysis method, and new regulation technology. The PCDD/Fs degradation technology includes photocatalytic degradation technology, metal catalytic degradation technology, and catalytic degradation technology under high temperature conditions. Quantum chemical analysis methods include physical adsorption and desorption phase catalytic synthesis and degradation and heterogeneous catalytic synthesis and degradation. New control technologies include solid waste control technology, chemical looping combustion (CLC) technology, and flow field simulation control technology. The technology of PCDD/Fs degradation is an important aspect in further optimizing the conditions of source inhibition of PCDD/Fs. Calculating the energy barrier of formation and degradation from the perspective of quantum chemistry is an effective method for analyzing the migration and transformation of dioxin precursors. Furthermore, exploring the new regulation technology is also the new research direction for inhibiting and controlling the source of PCDD/Fs. Full article

Coal fires are a significant source of greenhouse gas emissions and ecological pollutants, yet their emission characteristics and carbon accounting remain poorly constrained. To reveal the pollutant generation characteristics and carbon emission levels of the typical underground coal fire area in Sulabulak, Xinjiang, this study integrated laboratory simulation, multi-source remote sensing inversion, and in situ field monitoring. Thermogravimetric analysis, a high-temperature tube furnace, HSC thermodynamic simulation, and multi-source remote sensing data from Landsat-8/9 and Sentinel-1A were employed to investigate the gaseous products and heavy metal migration mechanisms at different combustion stages, and to delineate the spatial extent of different combustion states in the fire area. A coal loss model was then constructed by coupling experimentally determined carbon emission factors with remote sensing-derived areas and was compared with an emission flux model based on field measurements. The results show that the coal oxidation process proceeds through three distinct stages, with indicator gas ratios (CO₂/CO and C₂H₄/C₂H₆) serving as effective indicators for combustion state identification. Heavy metal partitioning is governed by elemental volatility and redox conditions: As and Se partition predominantly into the gas phase, while Zn becomes enriched in fly ash. Remote sensing time series analysis documents continuous fire expansion accompanied by progressive surface subsidence. By cross-validating the indirect coal loss model (constrained by remote sensing area) against the direct emission flux model (constrained by field measurements), we estimate the current annual GHG emission of the Sulabulak fire area at approximately 0.65 × 10⁴ t CO₂ equivalent. This study proposes a coupled “micro-experiment–macro-remote sensing–field measurement” approach for carbon emission accounting, providing reliable data support for environmental pollution control and the development of carbon inventories for coal fires in arid regions. Full article

The new Euro 7 standard will be the first legislation to limit the emissions produced by an automotive brake system. This has caused brake manufacturers to seek radical solutions to reduce the emissions generated from conventional grey cast iron (GCI) friction brakes. The regenerative braking system of electric vehicles (EVs) will require the friction brakes to be used less frequently than for an internal combustion engine vehicle. This may lead to a build-up of corrosion products on the friction surfaces that may not only affect the performance and service life of the GCI friction brake but also increase wear particle emissions when braking. Plasma electrolytic oxidation (PEO) ceramic-coated aluminium alloy rotors could be an alternative solution to reduce the effects of corrosion, produce lower brake emissions and also improve the energy efficiency of the EV by reducing its unsprung mass. To understand the interrelation between brake rotor corrosion and particulate emissions, this study concentrates on quantifying wear particles from a PEO-coated Al6082 brake rotor, both before and after exposure to salt fog corrosion. The results are compared to those for a standard uncoated GCI rotor and for an aluminium metal matrix composite (MMC) rotor subject to the same braking and corrosion test cycles. It was found that the PEO brake rotor produced a higher steady-state coefficient of friction in both the uncorroded and corroded conditions than either the GCI or MMC rotor, but emitted fewer wear particles in the uncorroded state, apart from at the highest brake line pressure. In the corroded state, the PEO rotor produced far lower emissions than either the corroded GCI or MMC rotors across all brake line pressures. Full article

Modern pyrotechnic materials are evolving from conventional fuel–oxidizer mixtures toward function-oriented energetic systems designed for controlled ignition, light emission, gas generation, pressure output and thermal response. This review analyzes recent progress in pyrotechnic materials through oxidizer chemistry, thermal and kinetic behavior, study-normalized performance comparison and bibliometric mapping. Representative oxidizer families, including nitrates, perchlorates, chlorates, metal oxides, hybrid oxide–salt systems, high-nitrogen salts, halogen-oxo oxidizers and coordination nitrate complexes, are compared in terms of chemical role and functional output. Thermal data show that decomposition temperature, heat release and activation energy must be interpreted together, since lower activation energy can indicate either enhanced reactivity or degradation during aging. A study-normalized relative performance factor (RPF) was used to compare performance changes within individual publications. The strongest relative improvements were associated with oxide selection, particle-size reduction, hybrid oxidizer design and coupling of nanothermites with gas-generating components. Bibliometric mapping confirmed a shift toward metal-based energetic materials, nanothermites, gas generators, combustion diagnostics, color systems and pyrotechnic devices. These trends show that oxidizer chemistry, particle architecture and additive function are increasingly selected for defined pressure, gas, light or thermal outputs. Full article

Under high-Mach-number flight conditions, the combustion chambers of hypersonic vehicles encounter extreme thermal environments marked by unilateral heating, high-heat-flux density, and supercritical pressure. Traditional hydrocarbon fuel cooling often suffers from insufficient heat sinks, high-temperature cracking and coking blockages, making it difficult to meet long-endurance thermal protection requirements. Liquid metal, due to its extremely high thermal conductivity, wide liquid phase temperature range, low Prandtl number and electromagnetic pump driving capability, has become a key technology for breaking through the bottleneck of high-heat-flux thermal protection. Apart from the magnitude of heat flux, the heat-transfer time scale (such as the characteristic thermal response time of the wall and the fluid) is also crucial. During hypersonic flight, transient thermal loads can change within milliseconds, requiring rapid thermal response. Liquid metals, due to their high thermal diffusivity, have a shorter thermal diffusion time compared to hydrocarbon fuels. This review employs a systematic literature review of approaches using gallium-indium-tin alloy, GaInSn, focusing on three core directions: the flow and heat-transfer characteristics of liquid metals, the optimization of cooling micro-channels, and the application of thermal protection systems. It summarizes the research progress at home and abroad, compares and analyzes the performance differences and applicable scenarios of typical liquid-metal working fluids, and summarizes the advantages and disadvantages of existing models, structural designs, and system schemes. The research shows that liquid metals can significantly alleviate thermal stratification and eliminate coking, and deep, narrow, tree-shaped, and biomimetic micro-channels can effectively enhance heat transfer. The liquid-metal-fuel dual-channel waste heat recovery and thermoelectric power generation system has demonstrated engineering application potential. Currently, the field still faces key challenges, such as unclear heat-transfer mechanisms under extreme conditions, the lack of general heat-transfer correlation formulas, insufficient compatibility with high-temperature materials, poor miniaturization and vibration resistance of electromagnetic pumps, and low system integration. In the future, efforts should be focused on developing multi-field coupled heat-transfer models under extreme thermal environments using engineered micro-channel structures, corrosion-resistant materials, and lightweight electromagnetic pumps, promoting the research and development of integrated thermal protection, heating and power generation systems, and providing support for the development of advanced thermal management systems for hypersonic aircraft and aviation engines. Full article

Atmospheric PM₁₀ was investigated across Campania, southern Italy, during August 2024 to assess its elemental composition and probable sources. In total, 132 daily samples were collected at six ARPAC sites representing harbor, traffic, industrial, school, and regional-background conditions. PM₁₀ concentrations ranged from 2 to 72 µg m⁻³, with the highest and lowest values recorded at the traffic and background sites, respectively. Elemental composition was determined by particle-induced X-ray emission and complemented by SEM–EDS. Elemental-based Positive Matrix Factorization (PMF) resolved six profiles, tentatively assigned to S-rich secondary aerosol, Cl-rich marine aerosol, mixed combustion/industrial emissions, Cu-rich traffic emissions, Ca–Sr-rich road dust, and Pb–Zn-rich waste combustion. At the industrial site, the three anthropogenic profiles together represented 74% of the apportioned mass. Traffic-related, marine, and S-rich secondary aerosol represented 49%, 65%, and 30% at the traffic, harbor, and background sites, respectively. SEM–EDS identified representative irregular S–K-rich and Ca-rich particles, crystalline Na–Cl-rich particles, and fine spherical metal-rich particles. Conditional probability function and trajectory analyses indicated local and regional influences, including a possible secondary sulfate contribution from the Mount Etna region. As the PMF analysis relied exclusively on elemental data, these source assignments should be regarded as indicative rather than definitive. Full article

A key challenge facing modern society, fueled by the relentless growth in energy and food requirements, is meeting rising energy needs without exacerbating greenhouse gas emissions. Nevertheless, fossil fuel combustion remains the primary contributor to human-induced pollution. As environmental concerns intensify and fossil resources become increasingly scarce, there is a growing push within the research community to identify alternative energy carriers and to advance more sustainable, low-impact technologies. Thus, this review focuses on catalytic CH₄ decomposition (CDM) for hydrogen production over Ni-, Fe, and Co-metal-based catalysts. Fe-based catalysts have received considerable attention for CDM due to their low cost and environmental sustainability. Furthermore, a discussion of deactivation and regeneration, along with the identified reaction mechanisms of CH₄ decomposition over these catalysts, is presented. Full article

Dry reforming of methane (DRM) represents a promising route for the valorization of CO₂ captured from industrial emissions through high-temperature catalytic conversion. In this work, a LaMn_1−xNi_xO₃ perovskite catalyst (x = 0.25, 6 wt% Ni) was synthesized as a powder by solution combustion synthesis and subsequently deposited onto γ-alumina supports to obtain a structured catalyst. X-ray diffraction confirmed the formation of the perovskite structure, characterized by corner-sharing BO₆ octahedra with Ni substitution at the B-site. H₂-temperature-programmed reduction (H₂-TPR) revealed the reduction of Mn⁴⁺ and Mn³⁺ species to MnO, accompanied by the complete reduction of oxidized Ni species to metallic Ni over the investigated temperature range. Raman spectroscopy of the spent catalyst indicated negligible carbon deposition after DRM. Moreover, the Mn–O stretching band shifted from 657 cm⁻¹ in the fresh catalyst to 643 cm⁻¹ after reaction, consistent with changes in the manganese oxidation state associated with the collapse of the perovskite structure and the formation of MnO. During a 25 h stability test at 700 °C, the powdered LaMn_1−xNi_xO₃ catalyst achieved a CH₄ conversion of 75% at a WHSV of 60 L g⁻¹ h⁻¹. DRM tests performed with the structured catalyst confirmed the catalytic performance under larger-scale operating conditions and different reaction parameters, including temperature, residence time, and CH₄/CO₂ feed ratio, reaching CH₄ conversions of up to 94% at 800 °C. Full article