Activity For Combustion Research Articles

Surface in situ Co-Mn modification over LaMnO3 perovskite with enhanced activity for ethane combustion

Catalytic combustion is one of effective ways to remove short-chain alkanes. In this study, we elaborately designed a novel catalyst of in situ Co-Mn decorated LaMnO3 perovskite for ethane catalytic combustion, in which extra Mn and Co species were introduced via acidic KMnO4 and Co(NO3)2 solution precipitation method. The addition of Mn and Co could not only slightly etch LaMnO3, thereby increasing specific surface area and redox property, but also generate new active phase CoMn2O4, thus accelerating reaction. Among all the as-prepared catalysts, CMO/LMO-0.5 exhibited admirable ethane removal efficiency with a T90 of 365 °C, a reaction rate of 0.46 mmol·g−1·h−1, a TOF value of 0.64 mmol·g−1·h−1, and excellent hydrothermal stability and reusability. Moreover, according to in situ DRIFTS, a possible pathway was proposed. This work can rationalize an alternative approach to develop an active catalyst for short-chain alkanes catalytic combustion or other catalytic systems.

Local and regional enhancements of CH4, CO, and CO2 inferred from TCCON column measurements

Abstract. In this study, we demonstrate the utility of available correlative measurements of carbon species to identify regional and local air mass characteristics as well as their associated source types. In particular, we combine different regression techniques and enhancement ratio algorithms with carbon monoxide (CO), carbon dioxide (CO2), and methane (CH4) total column abundance from 11 sites of the Total Carbon Column Observing Network (TCCON) to infer relative contributions of regional and local sources to each of these sites. The enhancement ratios provide a viable alternative to univariate measures of relationships between the trace gases that are insufficient in capturing source-type and transport signatures. Regional enhancements are estimated from the difference between bivariate regressions across a specific time window of observed total abundance of these species (BERr for bulk enhancement regression ratio) and inferred anomalies (AERr for anomaly enhancement regression ratio) associated with a site-specific background. Since BERr and AERr represent the bulk and local species enhancement ratio, respectively, its difference simply represents the site-specific regional component of these ratios. We can then compare these enhancements for CO2 and CH4 with CO to differentiate between combustion and non-combustion air masses. Our results show that while the regional and local influences in enhancements vary across sites, dominant characteristics are found to be consistent with previous studies over these sites and with bottom-up anthropogenic and fire emission inventories. The site in Pasadena shows a dominant local influence (> 60 %) across all species enhancement ratios, which appear to come from a mixture of biospheric and combustion activities. In contrast, Anmyeondo shows more regionally influenced (> 60 %) air masses associated with high-temperature and/or biofuel combustion activities. Ascension Island appears to only show a large regional influence (> 80 %) on CO / CO2 and CO / CH4, which is indicative of transported and combustion-related CO from the nearby African region, consistent with a sharp rise in column CO (3.51 ± 0.43 % ppb yr−1) at this site. These methods have important applications to source analysis using spaceborne column retrievals of these species.

Size-Dependent Elemental Composition in Individual Magnetite Nanoparticles Generated from Coal-Fired Power Plant Regulating Their Pulmonary Cytotoxicity.

High-resolution characterization of magnetite nanoparticles (MNPs) derived from coal combustion activities is crucial to better understand their health-related risks. In this study, size distribution and elemental composition of individual MNPs from various coal fly ashes (CFAs) collected from a representative coal-fired power plant were analyzed using a single-particle inductively coupled plasma time-of-flight mass spectrometry technique. Majority (61-80%) of MNPs were identified as multimetal (mm)-MNPs, while the contribution of single metal (sm)-MNPs to the total increased throughout all the CFAs, reaching the highest in fly ash escaped through the stack (EFA). Among Fe-rich MNPs, Fe-sole and Fe-Al matrices were predominant, and Fe-sole MNPs were identified as the important carrier for toxic metals, with the highest mass contributions of toxic metals therein. Toxic potency results showed that the oxidative stress induced by MNPs was 1.2-2.2 times greater than those of <1 μm fractions in CFAs, while the reduction in cell viability showed no significant difference, elucidating that these MNPs can induce more distinct oxidative stress compared to cell toxicity. Based on structural equation model, MNP size can both directly and indirectly regulate the toxic potency, and the indirect regulation is through a size-dependent elemental composition of MNPs, including toxic metals. sm-MNPs and Fe-rich MNPs with Fe-sole, Fe-Cr, and Fe-Zn matrices can regulate the oxidative stress, whereas Cr, Zn, and Pb associated with Fe-sole, Fe-Al, Si-Fe, and Al-Fe MNPs showed significant effects on cell viability.

Thermal analysis of St. John's Wort wastes and biochars: A study of combustion characteristics and kinetics

St. John's wort, extensively utilized in industries such as food, medicine, and cosmetics, generates substantial biomass waste. Utilizing these wastes is crucial to reducing environmental harm and making an economic contribution. This study aimed to determine the potential of St. John's wort wastes and biochar forms produced from these wastes to be used as solid fuel. In this context, the combustion behavior of the biomass and biochar were determined by thermogravimetric analysis method. Additionally, the Kissenger-Akahira-Sunosa and Flynn-Wall-Ozawa techniques were used to compute the combustion activation energies of these samples. According to the analysis, biomass combustion commenced at approximately 250°C and occurred in two stages, whereas biochar combustion initiated at around 400°C and proceeded in a single stage. Furthermore, over 90% of the mass from both samples was observed to decompose during combustion, with average combustion activation energies ranging between 70.08 and 203.86 kJ/mol for biomass and biochar, respectively. These findings suggest that biomass exhibits more readily combustible characteristics compared to biochar but is less energy efficient. In conclusion, optimizing the biochar production process could enhance its energy efficiency and potentially narrow the performance gap between biomass and biochar. Additionally, further research into alternative methods or additives to improve the energy efficiency of biomass combustion is warranted.

Dissolved and particulate phase phthalic acid esters in urban, suburban, and rural riverine catchments along the southeast coast of India after the COVID-19 pandemic

Dumped waste plastics have been evidenced as a potential source for harmful chemicals along the riverine regions of India. Furthermore, Corona Virus Disease – 19 (COVID-19) pandemic resulted in a subsequent surge in the use of personal protective equipment (PPE) related single-use plastics and Tamil Nadu was India's second major waste generator. Given the newer challenges from dumped waste plastics along the four major rivers of Tamil Nadu emptying into the Bay of Bengal, we investigated thirteen phthalic acid esters (PAEs), in both dissolved and particulate phases of river water and drinking water samples. Ʃ13PAEs in both phases followed the urban > suburban > rural catchment trend. Di (2-ethyl hexyl) phthalate (DEHP) was ubiquitous in both phases and the sites having a prevalence of open burning activities in the urban catchment showed elevated levels. The suburban and rural catchments of the Kaveri River (KR) and Thamirabharani River (TR) were predominated by DEP and DEHP. It is noteworthy that in the urban catchment, Ln (DiBP) and dissolved organic carbon (Ln DOC), were strongly correlated (R2 = 0.894, p < 0.05). Furthermore, a significant increase of DiBP (p < 0.05) in the urban catchment after the second phase of the pandemic most likely resulted from the wide use of DiBP in PPE plastics. Community-stored water from urban catchment was found to have a maximum of ∑13PAEs up to 3769.38 ng/L in the dissolved phase with elevated DMP concentrations leading to higher estrogenic equivalent. The average daily intake for dissolved phase PAEs was below the USEPA-recommended limit for drinking water. However, prolonged exposure to heavier PAEs in particulate matter cannot be ignored. Estimated ecotoxicological risk assessment showed the highest risk for fish species due to DEHP.

Transition Metal-Promoted LDH-Derived CoCeMgAlO Mixed Oxides as Active Catalysts for Methane Total Oxidation

A series of M(x)CoCeMgAlO mixed oxides with different transition metals (M = Cu, Fe, Mn, and Ni) with an M content x = 3 at. %, and another series of Fe(x)CoCeMgAlO mixed oxides with Fe contents x ranging from 1 to 9 at. % with respect to cations, while keeping constant in both cases 40 at. % Co, 10 at. % Ce and Mg/Al atomic ratio of 3 were prepared via thermal decomposition at 750 °C in air of their corresponding layered double hydroxide (LDH) precursors obtained by coprecipitation. They were tested in a fixed bed reactor for complete methane oxidation with a gas feed of 1 vol.% methane in air to evaluate their catalytic performance. The physico-structural properties of the mixed oxide samples were investigated with several techniques, such as powder X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX), elemental mappings, inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction under hydrogen (H2-TPR) and nitrogen adsorption–desorption at −196 °C. XRD analysis revealed in all the samples the presence of Co3O4 crystallites together with periclase-like and CeO2 phases, with no separate M-based oxide phase. All the cations were distributed homogeneously, as suggested by EDX measurements and elemental mappings of the samples. The metal contents, determined by EDX and ICP-OES, were in accordance with the theoretical values set for the catalysts’ preparation. The redox properties studied by H2-TPR, along with the surface composition determined by XPS, provided information to elucidate the catalytic combustion properties of the studied mixed oxide materials. The methane combustion tests showed that all the M-promoted CoCeMgAlO mixed oxides were more active than the M-free counterpart, the highest promoting effect being observed for Fe as the doping transition metal. The Fe(x)CoCeMgAlO mixed oxide sample, with x = 3 at. % Fe displayed the highest catalytic activity for methane combustion with a temperature corresponding to 50% methane conversion, T50, of 489 °C, which is ca. 40 °C lower than that of the unpromoted catalyst. This was attributed to its superior redox properties and lowest activation energy among the studied catalysts, likely due to a Fe–Co–Ce synergistic interaction. In addition, long-term tests of Fe(3)CoCeMgAlO mixed oxide were performed, showing good stability over 60 h on-stream. On the other hand, the addition of water vapors in the feed led to textural and structural changes in the Fe(3)CoCeMgAlO system, affecting its catalytic performance in methane complete oxidation. At the same time, the catalyst showed relatively good recovery of its catalytic activity as soon as the water vapors were removed from the feed.

Environmental risk estimation of potentially toxic metal(loid)s (PTMs) in fine particulate dust on the surface of children's playgrounds in parks

To determine the priority control factors for risk control and management of potentially toxic metal(loid)s (PTMs) in fine particulate dust (FPD) on the surface of children's playgrounds in parks, a comprehensive study was conducted on the pollution, risks, and sources of 12 PTMs in the FPD, taking Xi’an, China as a case. The pollution, ecological and health risks of PTMs were assessed using Nemerow integrated enrichment factor, modified Nemerow integrated eco–risk index, and health risk evaluation model, combined with Monte Carlo simulation. The sources of PTMs in the FPD were quantitatively apportioned using a positive matrix factorization model. Priority control factors for PTMs risk control and management were determined based on the results of source–oriented pollution and risk assessment. The results showed that the average contents (mg kg–1) of Cd (1.9), Cr (99.8), Cu (96.3), Hg (0.2), Pb (61.1), and Zn (239.4) in the FPD were considerably greater than local background values. The sources of PTMs in the FPD are industrial emission, coal combustion and medical activities, mixed source, and natural source, contributing 24.7%, 18.2%, 35.1%, and 22.1% to the total content of PTMs in the FPD, respectively. PTMs in the FPD posed a certain cancer risk to the elderly and children. Industrial emissions and mixed sources are priority control sources, while Cd and Cr are priority PTMs. It is recommended that local eco–environmental departments strengthen environmental monitoring of playgrounds, as well as management of industrial and transportation emissions, to ensure the health of residents.

Enhanced low-temperature catalytic activity and stability in methane combustion of Pd−CeO2 nanowires@SiO2 by Pt dispersion

The long-standing contradiction between low-temperature activity and high-temperature stability is one of the difficulties in catalytic combustion of low-concentration methane. The traditional Pd−CeO2 catalyst system has been applied to the oxidation of methane with low concentrations. However, the problem of sintering at high temperatures still exists. In this work, we prepared the Pt-modified Pd−CeO2 nanowires (NW) sample (in which the actual Pt, Pd, and Ce contents were 0.12, 0.86, and 9.8 wt%, respectively) using the one-pot reverse-micelle emulsion method. It was found that Pt-Pd−CeO2NW@SiO2 showed the highest low-temperature catalytic activity at a space velocity of 20,000 mL/(g h) and the best water resistance and high-temperature stability in the combustion of methane. The T50 % and T90 % (the temperatures for achieving methane conversions of 50 and 90 %) were 298 and 342 ℃, respectively, methane reaction rate at 270 ℃ was 0.49 μmol/(gcat s), and turnover frequency (TOF) at 270 °C was 0.198 s−1 over Pt-Pd−CeO2NW@SiO2; whereas over Pd−CeO2NW@SiO2 (in which the actual Pd and Ce contents were 0.82 and 10.6 wt%, respectively), the T50 % and T90 % were 360 and 420 ℃, respectively, methane reaction rate at 270 ℃ was 0.074 μmol/(gcat s), and TOF at 270 °C was 0.032 s−1. The introduction of the highly dispersed Pt to Pd−CeO2NW@SiO2 could effectively increase the PdOx sites of unsaturated coordination through the electron-donating interaction of the Pt with PdO, which played an important role in activating the C−H bonds in methane. In addition, the unique structure of encapsulation also rendered the Pt-Pd−CeO2NW@SiO2 sample to possess good water resistance and thermal stability in methane combustion. We are sure that the present work provides a possibility for developing the catalysts with stable catalytic and water-resistant performance at low and high temperatures in the combustion of methane.

Engineering Oxygen Vacancies of Co-Mn-Ni-Fe-Al High-Entropy Spinel Oxides by Adjusting Co Content for Enhanced Catalytic Combustion of Propane.

Transition metal-based oxides with similar oxidation activities for catalytic hydrocarbon combustion have attracted much attention. In this study, a new class of metal high-entropy oxides (CoxMnNiFeAl)3O4 (x = 1, 2, 3, 4, 5) with a porous structure was fabricated through a simple and inexpensive NaCl template-assisted sol-gel approach, which was employed for the catalytic oxidation of propane. The results indicated that the content of cobalt has a great impact on its activity, and the (Co4MnNiFeAl)3O4 catalyst exhibited the best catalytic activity. At the high space velocity of 60 000 mL·g-1·h-1, the optimized one with high-temperature treatment can still achieve 90% propane conversion at 309 °C, which is 68 and 178 °C lower than those of the (CoMnNiFeAl)3O4 catalyst and pure cobalt oxide, respectively. Meanwhile, it has the lowest apparent activation energy (46.6 KJ·mol-1) and the fastest reaction rate (26.976 × 10-6 mol·gcat-1·s-1 at 290 °C). The improved performance of the (Co4MnNiFeAl)3O4 catalyst could be attributed to the enhancement of low-temperature reducibility, the increased number of reactive surface oxygen species, and the cocktail effect of the high-entropy oxides. This work provides new insights into the preparation of efficient light alkane degradation catalysts and a realistic approach for the large-scale application of high-entropy oxides in the field of oxidation catalysts.

Liquid template synergizing combustion activation to construct vesicular porous carbon anode for sodium ion batteries

In this study, B, N and O tri-doped porous carbon material (EBNK) is successfully prepared by liquid template synergistic combustion activation. Benefiting from this method, the generated EBNK exhibits a unique vesicle-like spherical shell structure, which significantly accelerates the transport of sodium ions, and therefore the initial coulombic efficiency of its half-cells in ether-based electrolyte is as high as 95.6 %. Moreover, the synergistic effect of the three dopant atoms increases the number of defects and the spacing of the carbon layers, resulting in the EBNK anode exhibiting rare and excellent properties. The specific capacity is 487.5 mAh/g at 0.05 A/g, and 125 mAh/g at 50 A/g; the capacity is maintained at 138.9 mAh/g after 5500 cycles at 20 A/g. The NVP//EBNK full cell has an energy density of 192.2 Wh kg−1 at a power density of 159.7 W kg−1. This study will undoubtedly expand the methods for preparing sodium-ion batteries with excellent performance, provide new perspectives on the energy storage mechanism of multi-doped porous carbon, and promote the development of the energy storage field.

Hadza Landscape Burning.

We present the first published ethnographic description of landscape burning by Hadza hunter-gatherers of northern Tanzania and identify environmental, social, and cultural influences on Hadza landscape burning, thereby broadening the ethnographic record of anthropogenic burning practices described for hunter-gatherer communities. We report interview data collected in 2022 and 2023, describing their practices and attitudes regarding the causes and consequences of burning. We provide context by comparing our observations with those recorded for hunting and gathering populations in Africa, Australia, and North America. Hadza landscape burning is generally a solitary and male-dominated activity, contrary to ethnographic accounts of Indigenous landscape burning from North America and Australia. The primary goals stated by Hadza for landscape burning were improved hunting, reduced hazards from dangerous animals, and to reduce the density of livestock. Firsthand observations suggest that landscape burning has decreased over the past 20 years, and this historical trend is supported by interviews. Satellite imagery also suggests an overall decrease in burning activity in the region from 2001 to 2022. Among the Hadza, landscape burning is a culturally influenced and strongly gender-biased activity that is rapidly disappearing. Because burning can radically transform landscapes, these practices often generate or amplify conflicts of interest between groups with different land use strategies. Hadza report serious social conflict with pastoralists over landscape burning, and our study suggests this tension has constrained the practice in the past two decades.

Mechanistic understanding of oxygen spillover enables efficient propane combustion over Pt/AlSOx catalyst

Understanding of the mechanism of saturated alkanes catalytic combustion is crucial for the petrochemical industrial exhaust elimination. Noble metals are commonly proposed to be the active sites for C–H bond activation of saturated alkanes, whereas the critical role of support is largely underestimated. Herein, we reveals a novel pathway for propane activation and combustion on acidic support of Pt catalyst, driven by oxygen spillover, which differs significantly from previously reported reaction mechanisms. Specifically, the Pt/AlSOx-I catalyst was prepared by pyrolyzing the Al2(SO4)3 sol–gel to obtain the acidic micro-mesoporous AlSOx support, followed by loading the Pt active sites using wetness impregnation. In comparison to Pt catalysts supported by Al2O3 nanoparticles (10 nm) or commercially available common γ-Al2O3, the Pt/AlSOx-I catalyst demonstrates superior catalytic activity for propane combustion. It is found that gaseous oxygen species activated on Pt active sites spillovers to acidic support of Pt/AlSOx-I and then drives propane to activation and further oxidation on acidic support, thereby remarkably decreasing the apparent activation energies (Ea) from 112.4 to 72.0 kJ·mol−1. Kinetic results suggest that the negative effect of oxygen competitive adsorption is weakened because propane can be activated on the acidic AlSOx support. Additionally, high proportion of metallic Pt species benefits to gaseous oxygen activation as observed on Pt/AlSOx-R, leading to the further increased catalytic activity with highest specific mass reaction rate of 170.2 μmol gPt−1 s−1 and TOFPt of 0.289 s−1 at 220 °C. Our primary results provide novel insights into revealing the reaction mechanism of saturated alkanes combustion on dual active sites.

Paleoclimate, paleoenvironment, and human impact over the last 400 years based on lipid biomarkers from Lake Höglwörth, Germany

Lipid biomarkers are valuable proxies for reconstructing paleoclimate and paleoenvironmental changes as well as human impact. However, little attention has been paid on evaluating how the combination of biomarkers can be used to reconstruct various aspects of local paleoenvironmental conditions. This study presents a suite of lipid biomarker records from a sediment core from Lake Höglwörth, southern Germany, covering the past 400 years. Compound-specific hydrogen isotopic compositions (δD) of terrestrial n-alkanes (n-C29-alkane) and n-alkanoic acids (n-C30-acid) indicate minor changes in isotopic composition of precipitation. The δD of n-C22-acid is interpreted to record the isotopic composition of the lake water and evaporative enrichment, which drops after 1700 CE, coinciding with the construction of a mill and the related rerouting of a creek into Lake Höglwörth. The δD of n-C25-alkane is also enriched but decoupled from the reconstructed isotopic composition of precipitation and lake water. Therefore, we suggest that δD of n-C25-alkane reflects the leaf water isotopic composition of Sphagnum, which is present in the catchment and undergoes transpirative enrichment. Both short-chain compounds have become more enriched over the last century, maybe related to increasing temperature associated with anthropogenic climate warming. The faecal biomarkers record the changes in human population, partly related to the history of the local Monastery, the World Wars I and II as well as the intensive farming after the mid-20th century. Polycyclic aromatic hydrocarbons (PAHs) reveal a significant change in combustion activities associated with human activities such as the industrial revolution, biomass burning, and environmental cleanup as well as the implementation of emission standards. Our study demonstrates that the combination of plant wax compounds, faecal biomarkers, and PAHs from lacustrine sediment serves as a valuable tool to reconstruct and distinguish various aspects of paleoclimate and paleoenvironmental changes including human impacts.

Nitrogen isotope characteristics and importance of NOx from biomass burning in China

Biomass burning is a primary source of atmospheric nitrogen oxide (NOx), however, the lack of isotopic fingerprints from biomass burning limits their use in tracing atmospheric nitrate (NO3−) and NOx. A total of 25 biomass fuels from 10 provinces and regions in China were collected, and the δ15N values of biomass fuels (δ15N-biomass) and δ15N-NOx values of biomass burning (δ15N-NOx values of BB, open burning, and rural cooking stove burning) were determined. The δ15N-NOx values of open burning and rural cooking stove burning ranged from −0.8 ‰ to 11.6 ‰ and 0.8 ‰ to 9.5 ‰, respectively, indicating a significant linear relation with δ15N-biomass. Based on the measured δ15N-NOx values of BB and biomass burning emission inventory data, the δ15N-NOx values of BB in different provinces and regions of China were calculated using the δ15N-NOx model, with a mean value of 5.0 ± 1.8 ‰. The spatial variations in the estimated δ15N-NOx values of BB in China were mainly controlled by the differences in the δ15N-NOx values and the proportions of NOx emissions from various straw burning activities in provinces and regions of China. Furthermore, by using the combined local emissions of biomass burning with regional transportations of NOx based on air-mass backward trajectories, we established an improved δ15N-NOx model and obtained more accurate δ15N-NOx values of BB in regions (2.3 ‰ to 8.4 ‰). By utilising the reported δ15N-NOx values of precipitation and particulate matter from 21 cities in China and the more accurate δ15N-NOx values of BB, the NOx contributions from four sources (mobile sources, coal combustion, biomass burning, and microbial N cycle) at the national scale were estimated using a Bayesian model. The significant contributions of biomass burning (20.9 % to 44.3 %) to NOx emissions were revealed, which is vital for controlling NOx emissions in China.

Enhancing long-term trend simulation of the global tropospheric hydroxyl (TOH) and its drivers from 2005 to 2019: a synergistic integration of model simulations and satellite observations

Abstract. The tropospheric hydroxyl (TOH) radical is a key player in regulating oxidation of various compounds in Earth's atmosphere. Despite its pivotal role, the spatiotemporal distributions of OH are poorly constrained. Past modeling studies suggest that the main drivers of OH, including NO2, tropospheric ozone (TO3), and H2O(v), have increased TOH globally. However, these findings often offer a global average and may not include more recent changes in diverse compounds emitted on various spatiotemporal scales. Here, we aim to deepen our understanding of global TOH trends for more recent years (2005–2019) at 1×1°. To achieve this, we use satellite observations of HCHO and NO2 to constrain simulated TOH using a technique based on a Bayesian data fusion method, alongside a machine learning module named the Efficient CH4-CO-OH (ECCOH) configuration, which is integrated into NASA's Goddard Earth Observing System (GEOS) global model. This innovative module helps efficiently predict the convoluted response of TOH to its drivers and proxies in a statistical way. Aura Ozone Monitoring Instrument (OMI) NO2 observations suggest that the simulation has high biases for biomass burning activities in Africa and eastern Europe, resulting in a regional overestimation of up to 20 % in TOH. OMI HCHO primarily impacts the oceans, where TOH linearly correlates with this proxy. Five key parameters, i.e., TO3, H2O(v), NO2, HCHO, and stratospheric ozone, can collectively explain 65 % of the variance in TOH trends. The overall trend of TOH influenced by NO2 remains positive, but it varies greatly because of the differences in the signs of anthropogenic emissions. Over the oceans, TOH trends are primarily positive in the Northern Hemisphere, resulting from the upward trends in HCHO, TO3, and H2O(v). Using the present framework, we can tap the power of satellites to quickly gain a deeper understanding of simulated TOH trends and biases.

Urban sources of methane characterised by long-term eddy covariance observations in central Europe

Multiyear eddy covariance measurements of methane and carbon dioxide were performed in Innsbruck, Austria, a mid-sized European city in the Alps. Annual mean methane and carbon dioxide fluxes were on the order of 21.6 nmol/m2/s and 11.7 μmol/m2/s respectively. Methane fluxes increased significantly with decreasing temperature and showed a negligible weekend to weekday effect. Accompanying non-methane volatile organic compound (NMVOC) measurements provided additional constraints on urban methane sources during an intensive 6-week campaign in 2021. Positive matrix factorization analysis identified a unique and dominant methane source. Contributions from biomass burning and vehicle emissions were found to be small. No evidence was found for a large unknown biogenic source. A second intensive campaign in 2023 revealed that the measured ethane to methane enhancement in turbulent plumes showed a typical ratio of 5.2 ± 0.6%, close to the unburned ratio of natural gas (5%) in Austria. The analysis suggests that urban methane fluxes are likely to be dominated by end-user releases rather than natural gas leaks in the pipeline system. Long-term eddy flux observations also allowed identifying the existence of urban super-emitters, which brought area weighted methane fluxes up to 39 nmol/m2/s in 2022. On average, the 100 y global warming potential of methane emitted by natural gas combustion activities is 6% relative to the total urban CO2 flux, and ∼12% relative to CO2 emissions from the residential, commercial and public sectors in Innsbruck.

Liquid bath-assisted combustion activation preparation of nitrogen/sulfur-doped porous carbon for sodium-ion battery applications

A liquid-bath-assisted salt-template combustion activation method has been developed to overcome the shortcomings of the conventional template method, including elaborate processes and environmental pollution. Herein, N/S double-doped porous carbon material (ECSK-15) with high specific surface area (1148.60 m2 g−1) is synthesized through it for sodium-ion batteries (SIBs). Benefitting from this approach, the number of ion diffusion channels and the ion exchange rate of the product are significantly increased. When using ether-based electrolyte, after 1000 cycles at a large current density of 2 A g−1, the reversible capacity could still be maintained at 135.60 mA h g−1. The assembled full cell exhibits a high reversible capacity of 480.49 mAh g−1 at a current rate of 0.5 A g−1. The energy density is calculated to be 204.11 Wh kg−1 at a power density of 160.71 W kg−1. This work provides a porous carbon anode material with good sodium-ion storage capacity and rate performance for application in SIBs.

Multi-Year Continuous Observations of Ambient PM2.5 at Six Sites in Akure, Southwestern Nigeria

The spatial–temporal variations of fine particulate matter (PM2.5) in Akure, a city in southwestern Nigeria, are examined based on multi-year continuous observations using low-cost PM2.5 sensors at six different sites. The average annual concentration of PM2.5 across these sites was measured at 41.0 µg/m3, which surpassed both the Nigerian national air quality standard and the World Health Organization air quality guideline level. PM2.5 levels were significantly higher during the dry season (November–March), often exceeding hazardous levels (over 350 µg/m3), than during the wet season. The analyses of trends in air mass trajectories and satellite data on fire occurrences imply that the transport of dust and accumulation of PM2.5 originating from local/regional open burning activities played crucial roles in increased PM2.5 concentrations during the dry season. Further, site-to-site variations in the PM2.5 levels were observed, with relatively high concentrations at less urbanized sites, likely due to high local emissions from solid fuel combustion, waste burning, and unpaved road dust. Diurnal patterns showed morning and evening peaks at less urbanized sites, accounting for an estimated 51–77% of local emissions. These results highlight the importance of local emission sources in driving spatial–temporal PM2.5 variations within the city and the need for targeted mitigation strategies to address the significant air pollution challenges in Akure and similar regional cities in West Africa.

Evidence of a dual African and Australian biomass burning influence on the vertical distribution of aerosol and carbon monoxide over the southwest Indian Ocean basin in early 2020

Abstract. During the 2020 austral summer, the pristine atmosphere of the southwest Indian Ocean (SWIO) basin experienced significant perturbations. This study examines the variability of aerosols and carbon monoxide (CO) over this remote oceanic region and investigates the underlying processes in the upper troposphere–lower stratosphere (UT-LS). Aerosol profiles in January and February 2020 revealed a multi-layer structure in the tropical UT-LS. Numerical models – the FLEXible PARTicle dispersion model (FLEXPART) and the Modèle Isentropique de transport Mésoéchelle de l'Ozone Stratosphérique par Advection (MIMOSA) – indicated that the lower-stratospheric aerosol content was influenced by the intense and persistent stratospheric aerosol layer generated during the 2019–2020 extreme Australian bushfire events. A portion of this layer was transported eastward by prevailing easterly winds, leading to increased aerosol extinction profiles over Réunion on 27 and 28 January. Analysis of advected potential vorticity revealed isentropic transport of air masses containing Australian biomass burning aerosols from extratropical latitudes to Réunion at the 400 K isentropic level on 28 January. Interestingly, we found that biomass burning (BB) activity in eastern Africa, though weak during this season, significantly influenced (contributed up to 90 % of) the vertical distribution of CO and aerosols in the upper troposphere over the SWIO basin. Ground-based observations at Réunion confirmed the simultaneous presence of African and Australian aerosol layers. This study provides the first evidence of African BB emissions impacting the CO and aerosol distribution in the upper troposphere over the SWIO basin during the convective season.

Analysis of a CRDI diesel engine powered by ternary fuel blends (diesel, biodiesel, and pentanol) doped with alumina nano-additives

Environmental constraints associated with fossil fuels have driven researchers to find a novel, potential and environmentally benign alternative fuel. Biodiesel, vegetable oil, and alcohol have gained rapid momentum thanks to their renewable nature and comparable energy contents in recent years. Accordingly, a Ternary fuel blend is prepared comprising three fuels namely diesel, biodiesel, and pentanol. Waste cooking oil was identified as the source for biodiesel and Pentanol was chosen among various alcohol alternatives due to improved energy density, reduced toxicity. These are endorsed to the enhancement in surface area-volume ratio of nano additives which boosts the catalytic combustion activity and also causing lesser fuel to take part in combustion for maintaining a constant engine speed. The experimentation is done with ternaryfuel blends with varying pentanol and biodiesel concentrations of diesel, biodiesel and pentanol). Upon experimentation, it was observed that, ternary fuel blend ‘TF’ comprising 70% diesel, 20% biodiesel and 10% pentanol, yielded best performance and was used for doping of Alumina oxide (Al2O3) nano additives. The Al2O3 nanoparticles were doped with ternary blends at fractions of 10 ppm, 20 ppm, and 30 ppm. It was observed that 20 ppm Al2O3 nanoparticle blended TF blend improved BTE and lowered BSFC by about 12.01% and 22.57% respectively. The performance tremendously along with lowered the CO emission by 49.21%, HC emission by 18.91% and smoke opacity by 9.02%.