Search Results (116)

The background modification of ecosystems affected by fire can cause black or dark colours in animals to become adaptive, providing better protection against visually oriented predators. We surveyed fire-prone Mediterranean woodlands to describe the behaviour, position and background characteristics of the black cicada Tibicina quadrisignata Hagen, 1855 found in recently burnt and unburnt trees. A human detectability test, using cicada pictures in natural backgrounds taken during the fieldwork, was used to assess detection risk. Most cicadas found were solitary males uttering courtship song. Many cicadas flew when approached, with 82% of flight initiation distances being less than 3 m and half of the flights being less than 30 m. Cicadas favoured sunny locations in early morning, and shady sites as the temperature increased. Fire altered fine-scale microhabitat use by cicadas, since cicadas were found in 71% thicker stems and at 14% lower height on the tree, in burnt trees, in relation to unburnt trees. Generalised Linear Mixed Models (GLMMs) revealed a negative fire effect on cicada detection by human test participants. The probability of detection fell from 0.62 in unburnt backgrounds to 0.48 in burnt backgrounds, while the time needed for detection did not change between burnt and unburnt sites. Overall, these results show that T. quadrisignata cicadas adjust their substrate use after fire and are less detectable on burnt backgrounds. Real predation risk, however, also depends on thermoregulation-associated exposure, courtship song activity and predator densities. Full article

Fire refugia are critical for post-disturbance recovery, yet microhabitats such as stones remain understudied despite their ubiquity and thermal persistence. This study tested whether the depth- and area-dependent refugial capacity of stones previously demonstrated in Mediterranean oak forests also operates in intensively managed plantations and how forest type and management modulate this capacity. Immediate wildfire effects (1–8 days post-fire) on ground-dwelling macroinvertebrates were quantified under 660 stones across burnt and unburnt native maritime pine and exotic eucalypt plantations following a medium- to high-severity wildfire. Stones acted as thermal refugia in both plantation types, with burial depths greater than 5 cm and surface areas greater than 500 cm² predicting survival. Despite severe impacts (richness declined by 56% in pine and 63% in eucalypt; overall mortality exceeding 50%), diverse taxa persisted under stones, particularly ground spiders, ants, centipedes, rock bristletails, and harvestmen, while plant-associated and moisture-dependent groups suffered the highest losses. Native pine supported a higher abundance and richness per stone than exotic eucalypt in both burnt and unburnt conditions, reflecting management-driven differences in stone size, depth, and availability. These findings show that retaining sufficiently large, deeply buried stones during plantation establishment can enhance post-fire biodiversity recovery in increasingly fire-prone production landscapes. Full article

Coal combustion residues are often useful components for the cement industry. This study represents a material characterization and screening analysis by focusing on the mineralogical, physicochemical, and petrographic compositions of fly and bottom ash samples from four Greek power plants in order to evaluate their suitability and potential in industrial applications, especially as fillers in cement manufacturing. Proximate analysis revealed LOI values exceeding ASTM C618-22 limits. The sum of SiO₂, CaO, and Al₂O₃ classifies the studied samples as Class C except one. Iron and magnesium oxides are among the major components, while S, Ni, and Sr are also contained in significant amounts. Calcite, quartz, and plagioclases dominate, corresponding to their geochemical profile, while secondary mineral phases (i.e., neo-formed minerals during coal combustion) such as natrolite and gehlenite, were also identified. Relatively high amounts of carbonized organic matter and unburnt organic particles point to the incomplete combustion process, revealing the risk of slagging into the combustion chamber; this is confirmed through the high slagging and fouling indices. The amount of the magnetic fraction is low; magnetic spherules with complex surface structures and a wide range of spherule sizes were observed. While the pozzolanic character of the samples is strong, high values of LOI, S content, and carbonized organic material make them suitable for the cement industry after further treatment only. Full article

This study presents a detailed numerical analysis of impinging propane flames within confined enclosures using the Fire Dynamics Simulator (FDS, v6.5.3). Two archetypal configurations were examined: (i) free buoyant plumes in unconfined environments, and (ii) ceiling-impinging flames under both open and confined conditions. The investigation encompassed a range of heat release rates (0.5–18.6 kW) and five degrees of ventilation confinement. The simulation results confirm that FDS reliably reproduces flame height evolution under free plume conditions, exhibiting strong consistency with Heskestad’s empirical correlation and available experimental benchmarks. Under ceiling impingement, confinement markedly influences the thermal field, the distribution of major gas species (O₂, CO₂, C₃H₈), and the accumulation of unburnt gas. Distinct from previous works primarily centered on unconfined plume dynamics, the present study systematically characterizes the onset of auto-ignition through combined lower flammability limit (LFL) and auto-ignition temperature (AIT) criteria for confined propane combustion. The highest auto-ignition risk was identified in partially confined configurations (Conf. 2 and Conf. 3) at an HRR of 18.6 kW, where unburnt propane concentrations locally exceeded the LFL (≈0.2%) and ceiling temperatures surpassed the AIT of propane (455 °C). The findings elucidate critical trade-offs between ventilation and safety. They also contribute to a validated FDS-based methodology for evaluating fire-induced flow structures, combustion behavior, and ignition hazards in confined spaces. Full article

The impact of the aviation sector on the Earth’s atmosphere and climate is not limited to the effects of CO₂ emissions generated by the combustion of hydrocarbon-based fuel in an aircraft engine. It is complemented by other combustion products and non-CO₂ emissions, such as CO, NO_x, unburnt hydrocarbons (UHCs), and soot, as well as the formation of condensation trails (contrails) as a result of emitted H₂O and condensation nuclei. To evaluate the overall atmospheric impact of an aircraft mission, it is necessary to model the aero engine and the combustion chamber in context with the atmospheric conditions over the course of the flight trajectory. Following that rationale, this paper presents the novel multidisciplinary ‘Modeling and System analysis of Aero Engines’ (MSAE) platform, aiming to evaluate the emission products over the flight trajectory with realistic atmospheric and operative boundary conditions. MSAE comprises an ambient condition model, an aircraft operating model, an aero engine performance model, and a combustion chamber model. The functionality of the individual models as well as their interconnections are demonstrated using the example of an Airbus A320 powered by an International Aero Engines V2500-A1 turbofan engine. Non-CO₂ emissions, including CO, NO_x, UHC, and soot emission indices, can be predicted at a selected operating point. Furthermore, an evaluation of contrail formation for both annually averaged and intraday ambient conditions is conducted, showing the benefit of considering ambient conditions in a finer temporal resolution. The results show the functionality of the presented MSAE platform and the necessity of performance and emission analysis under realistic conditions. Full article

The purpose of this research article is to assess the emissions performance of a marine genset that was retrofitted to combust biomethane in a dual-fuel mode. The retrofits are part of our research efforts to provide a green cold-ironing solution for vessels at berth or in anchorage, and to advocate for a greener electrification of the port sector. An experimental campaign is presented to test the emissions performance by substituting biomethane as an energy basis. Up to 60% biomethane energy substitution is tested under low, medium, and high engine loads. The engine load is controlled via a resistive load bank, and the respective emissions were captured using portable gas analyzers. The results reveal a poor utilization of the gaseous fuel, leading to low engine efficiencies, high CO, and unburnt hydrocarbons at low and intermediate engine loads. However, marine gensets are utilized at high engine loads. At these loads, the specific fuel consumption improves. As indicated in the open literature, biomethane leads to high CO, and unburnt hydrocarbons and the respective NO_x emissions drop compared to diesel-only cases. Full article

Predicting wildland fire spread requires numerical schemes that can resolve sharp gradients at the fireline while remaining stable and efficient on practical grids. We develop a compact high-order finite-difference scheme for Hamilton–Jacobi level-set formulations of wildfire propagation, based on the anisotropic spread law of Mallet and co-authors. The spatial discretization employs a compact finite-difference derivative scheme to achieve spectral-like resolution with narrow stencils, improving accuracy and boundary robustness compared with wide-stencil ENO/WENO reconstructions. To control high-frequency artifacts intrinsic to non-dissipative compact schemes, an implicit high-order low-pass filter is incorporated and activated after each Runge–Kutta stage. Convergence is verified on the eikonal expanding-circle benchmark, where the method attains the expected high-order spatial accuracy as the grid is refined. The proposed scheme is then applied to wind-driven wildfire simulations governed by Mallet’s non-convex Hamiltonian, including a single ignition under moderate and strong wind. A complex topology test case is also considered, involving two ignitions that merge into a single front with the evolution of an internal unburnt island. The results demonstrate that the proposed method accurately reproduces fireline evolution even on coarse grids, achieving accuracy comparable to fifth-order WENO while maintaining superior fidelity in complex fireline topologies, where it better resolves multi-front interactions and topological changes in the fireline. This makes the method an efficient, accurate alternative for level-set wildfire modeling and readily integrable into existing frameworks. Full article

Fire has had a profound impact on Australia’s landscapes and biodiversity since the late Tertiary. Indigenous (Aboriginal) people have lived in Australia for at least 65,000 years and fire is an integral part of their culture and cosmology. In 2015, an Indigenous cultural burn was undertaken by Banbai rangers at Wattleridge Indigenous Protected Area, New England Tablelands, NSW. We compared the impact of this burn on the composition, cover, abundance, and species richness of dry sclerophyll vegetation and fuel hazard, with a hazard reduction burn at nearby Warra National Park, using a Before-After-Control-Impact experimental design. Our study found that the low-severity cultural burn and moderate-severity hazard reduction burn reduced fuel loads but did not have a significant impact on the composition of the vegetation overall or the herb layer. The hazard reduction burn had a significant impact on shrub and juvenile tree (woody species) cover, while the abundance of woody species was significantly affected by both fires, with a mass germination of ‘seeder’ species, particularly after the cultural burn. The long unburnt fire regime at Wattleridge may have made the vegetation more responsive to fire than the more frequently burnt vegetation at Warra, through accumulation of seed in the seed bank, so that the patchy cultural burn had a greater impact on woody species abundance. In terms of ecological and bushfire management outcomes, this study provides evidence to support claims that Indigenous cultural burning decreases fuel loads, stimulates regeneration of shrubs and trees, and manages at a local, place-based scale. We recommend cultural burning as a key management tool across Indigenous Protected Areas and other land tenures, with its implementation monitored and adaptively managed through two-way science, to foster fire regimes that are both culturally and ecologically beneficial. This is a vital element of our resilience in the Pyrocene and a significant step toward decolonizing science and land management. Full article

The construction industry is the biggest consumer of raw materials, and there is growing pressure for this industry to reduce its environmental footprint through the adoption of sustainable solutions. Waste plastic in a recycled form can be used to produce valuable products that can decrease dependence on natural resources. Despite the growing trend of exploring the potential of recycled plastics in construction through composite manufacturing and nonstructural products, to date no scientific data is available about converting waste plastic into recycled plastic to manufacture interlocking hollow blocks (IHBs) for construction. Thus, the current study intended to fill this gap by investigating the dynamic, mechanical, and physicochemical properties of engineered IHBs made out of recycled plastic. Engineered IHBs are able to self-center via controlled tolerance to lateral displacement, which makes their design novel. High-density polyethylene (HDPE) waste was considered due to its anticipated material properties and abundance in daily-use household products. Mechanical recycling coupled with extrusion-based pressurized filling was adopted to manufacture IHBs. Various configurations of IHBs and prism samples were tested for compression and shear strength, and forensic tests were conducted to study the physicochemical changes in the recycled plastic. In addition, to obtain better dynamic properties for energy dissipation, the compressive strength of the IHBs was 30.99 MPa, while the compressive strength of the prisms was 34.23 MPa. These values are far beyond the masonry strength requirements in applicable codes across the globe. In-plane shear strength was greater than out-of-plane shear strength, as anticipated. Microstructure analysis showed fibrous surfaces with good resistance and enclosed unburnt impurities. The extrusion process resulted in the elimination of contaminants and impurities, with limited variation in thermal stability. Overall, the outcomes are favorable for potential use in house construction due to sufficient masonry strength and negligible environmental concerns. Full article

Forest fires are commonly regarded as negative for ecosystems; however, they also represent a major ecological force shaping the biodiversity of invertebrates and many other organisms. The aim of this study was to better understand how multiple groups of invertebrates respond to wildfire across different forest types in Central Europe. The research was conducted following a large forest fire (ca. 1200 ha) that occurred in 2022. Data were collected over two years (2023 and 2024), from April to September. The research was conducted in coniferous forests and included six pairwise study types: burnt and unburnt dead spruce (bark beetle affected), burnt and unburnt clear-cuts, and burnt and unburnt healthy stands. In total, 96 traps were deployed each year. Across both years, 220,348 invertebrates were recorded (1.Y: 128,323; 2.Y: 92,025), representing 24 taxonomic groups. A general negative trend in abundance following forest fire was observed in the groups Acari, Auchenorhyncha, Blattodea, Dermaptera, Formicidae, Chilopoda, Isopoda, Opiliones, and Pseudoscorionida. Groups showing a neutral response included Araneae, Coleoptera, Collembola, Diplopoda, Heteroptera, Psocoptera, Raphidioptera, Thysanoptera, and Trichoptera. Positive responses, indicated by an increase in abundance, were recorded in Hymenoptera, Orthoptera, Lepidoptera, and Diptera. However, considerable differences among management types (clear-cut, dead spruce, and healthy) were evident, as their distinct characteristics largely influenced invertebrate abundance in both unburnt and burnt variants of the types across all groups studied. Forest fire primarily creates favorable conditions for heliophilous, open-landscape, and floricolous invertebrate groups, while less mobile epigeic groups are strongly negatively affected. In the second year post-fire, the total invertebrate abundance in burnt sites decreased to 59% of the first year’s levels. Conclusion: Forest fire generates a highly heterogeneous landscape from a regional perspective, creating unique ecological niches that persist more than two years after fire. For many invertebrates, successional return toward pre-fire conditions is delayed or incomplete. Full article

The Portuguese forest plays a crucial role in maintaining ecological balance and fostering socio-economic sustainability within rural areas. Nonetheless, it is currently facing significant challenges due to the increasing intensity and frequency of forest fires observed in recent decades. The deterioration of traditional agricultural practices, the proliferation of monocultures, and alterations in land use patterns have significantly exacerbated these challenges. Consequently, the landscape has undergone considerable transformations, resulting in a decline in biodiversity and a weakening of local economies. This study examines land use in mainland Portugal from 1995 to 2018, utilising data on land occupation, land cover, and burnt areas from the Institute for Nature Conservation and Forests. The cartographic analysis of three periods—1995, 2007, and 2018—along with the fire data recorded between 1996 and 2018, enabled the observation of changes in the predominant land use and land cover (LULC) classes, particularly among forests, scrubland, and agricultural areas. The results highlight a significant increase in forested areas, especially eucalyptus, as well as urbanisation, while scrubland and agricultural areas have decreased. Using specific LULC level 4, and burnt (BA) and unburnt (NB) areas, temporary crops decreased substantially (−14% NB/−4% BA 1995–2007; −23% NB by 2018). Eucalyptus showed strong continuous growth (16% NB/35% BA 1995–2007; 23% NB/47% BA 2007–2018). Maritime pine suffered severe losses, especially in burnt areas (−42%/−28%). Cork oak remained stable (1–4% growth). Other oaks showed minimal changes. Bushes (scrubland) declined sharply post-2007 (−31% BA/−6% NB). The most significant transformation occurred between 1995 and 2007, particularly in the south of Portugal, where wildfires promoted the replacement of maritime pine with eucalyptus, a species that offers greater profitability, leading to agricultural abandonment in burned areas. Full article

This paper investigates the influence of ventilation conditions, including oxidizer flow speed and oxygen concentration, on major species composition in favor of estimating a risk of flame acceleration at reduced gravity. A two-step chemical reaction for gas phase and a soot formation model based on laminar smoke point are used. To calculate thermal radiation from flame, a discrete-ordinates method is coupled with a non-grey model by taking into account the radiative properties of CO, CO₂, H₂O and soot. The predictions provide further insights into the intimate coupling of fuel types, such as heptane and dodecane, with burning rate, flame structure and toxic emissions as a consequence of changes in ventilation conditions such as oxidizer flow velocity and oxygen concentration. From a boundary-layer microgravity flame, the CO₂ to CO ratio is less than 3, and the unburnt hydrocarbons C_mH_n to CO ratio is less than 2, with a concentration of unburnt fuel that exceeds the Lower Flammability Limit. This finding on the production of unburnt species is contrasted to the case of a buoyancy-controlled flame at Earth gravity. Full article

Ammonia (NH₃) and hydrogen (H₂) are considered promising fuels for the power sector’s decarbonization. Their combustion is capable of producing energy with zero direct CO₂ emissions, and ammonia can act as a stable energy H₂ carrier. This study numerically investigates the design and implementation of staged combustion of a mixture of NH₃/H₂ by means of CFD simulations. The investigation employed the single-phase flow RANS governing equations and the eddy dissipation concept (EDC) combustion model, with the incorporation of a detailed kinetic mechanism. The combustion chamber operates under the RQL (rich–quench–lean) combustion regime. The first stage operates under rich conditions, firing mixtures of ammonia in air, enriched by hydrogen (H₂) to enhance combustion properties in a swirl and bluff-body stabilized burner. The secondary stage injects additional air and hydrogen to mitigate unburnt ammonia and NO_x emissions. Simulations of the first stage were performed for a thermal input ranging from 4 kW to 8 kW and flames with an equivalence ratio of 1.2. In the second stage, additional hydrogen is injected with a thermal input of either 1 kW or 2 KW, and air is added to adjust the global equivalence ratio to 0.6. Full article

With conventional fuels dwindling and emissions rising, there is a necessity to develop and assess innovative substitute fuel for compression ignition (CI) engines. This study investigates the potential of magnesium oxide (MgO) nanoparticles as a sustainable additive to enhance the performance and reduce emissions of used cooking oil (UCO) biodiesel–diesel blends in CI engines. MgO nanoparticles were biosynthesized using Citrus aurantium peel extract, offering an environmentally friendly production method. A single-cylinder CI engine was used to test the performance of diesel fuel (B0), a 20% biodiesel blend (B20), and B20 blends with 30 ppm (B20M30) and 60 ppm (B20M60) MgO nanoparticles. Engine performance parameters (brake thermal efficiency (BTE), brake-specific fuel consumption (BSFC), and exhaust gas temperature (EGT)) and emission characteristics (CO, NO_x, unburnt hydrocarbons (HCs), and smoke opacity) were measured. The B20M60 blend showed a 2.38% reduction in BSFC and a 3.38% increase in BTE compared to B20, with significant reductions in unburnt HC, CO, and smoke opacity. However, NO_x emissions increased by 6.57%. The green synthesis method enhances sustainability, offering a promising pathway for cleaner and more efficient CI engine operation using UCO biodiesel, demonstrating the effectiveness of MgO nanoparticles. Full article

Fire is important in boreal forest ecosystems, but comprehensive recovery analysis is lacking for soil nutrients and plant traits in China boreal forests, where the strict “extinguish at sight” fire prevention policy has been implemented. Based on over 50 years of forest fire recordings in the Daxing’anling Mts, 48 pairs of burnt and unburnt controls (1066 plots) were selected for 0–20 cm soil sampling and plant surveys. We recorded 18 plant parameters of the abundance of each tree, shrub, grass, and plant size (height, diameter, and coverage), 7 geo-topographic data parameters, and 2 fire traits (recovery year and burnt area). We measured eight soil properties (soil organic carbon, SOC; total nitrogen, TN; total phosphorus, TP; alkali-hydrolyzed P, AP; organic P, Po; inorganic P, Pi; total glomalin-related soil protein, T-GRSP; easily-extracted GRSP, EE-GRSP). Paired T-tests revealed that the most significant impact of the fire was a 25%–48% reduction in tree sizes, followed by decline in the plant diversity of arbors and shrubs but increasing plant diversity in herbs. GRSP showed an >18% increase and P_o decreased by 17% (p < 0.05). Redundancy ordination showed that the post-fire recovery years and burnt area were the most potent explainer for the variations (p < 0.05), strongly interacting with latitudes and longitudes. Plant richness and tree size were directly affected by fire traits, while the burnt area and recovery times indirectly increased the GRSP via plant richness. A fire/control ratio chronosequence found that forest community traits (tree size and diversity) and soil nutrients could be recovered to the control level after ca. 30 years. This was relatively shorter than in reports on other boreal forests. The possible reasons are the low forest quality from overharvesting in history and the low fire severity from China’s fire prevention policy. This policy reduced the human mistake-related fire incidence to <10% in the 2010s in the studied region. Chinese forest fire incidences were 3% that of the USA. The burnt area/fire averaged 5 hm² (while the USA averaged 46 hm², Russia averaged 380 hm², and Canada averaged 527 hm²). Overharvesting resulted in the forest height declining at a rate of >10 cm/year. Our finding supports forest management and the evaluation of forest succession after wildfires from a holistic view of plant–soil interactions. Full article