Metal Abundance Research Articles

Spectroscopy and Photochemistry of [Al, N, C, O, H]: Connectivity to Aluminium-Bearing Species in the Universe.

Aluminium is one of the most abundant metals in the universe and impacts the evolution of various astrophysical environments. Currently detected Al-bearing molecules represent only a small fraction of the aluminium budget, suggesting that aluminium may reside in other species. AlO and AlOH molecules are abundant in the oxygen-rich supergiant stars such as VY Canis Majoris, a stellar molecular factory with 60+ molecules including the prebiotic NC-bearing species. Additional Al-bearing molecules with N, C, O, and H may form in O-rich environments with radiation-accelerated chemistry. Here, we present spectroscopic identification of novel aluminium-bearing molecules composed of [Al, N, C, O, H] and [Al, N, C, O] from the reactions of Al atoms and HNCO in solid argon matrix, which are potential Al-bearing molecules in space. Photoinduced transformations among six [Al, N, C, O, H] isomers and three [Al, N, C, O] isomers, along with their dissociation reactions forming the known interstellar species, have been disclosed. These results provide new insight into the chemical network of astronomically detected Al-bearing species in space.

Distribution of trace metals and metalloids in tissues of Eurasian Woodcock (Scolopax rusticola) from Southern Italy

Heavy metals and metalloids in the environment are recognised as a threat to the health of organism. Terrestrial birds are ideal subjects for the examination of these pollutants because of their high mobility and high intra- and interspecific variation in trophic levels. We examined the contents of 6 trace metals (Cd, Pb, Cr, Sb and V) and metalloids (As) in the liver, kidney, muscle, and feathers of woodcocks (Scolopax rusticola) from Southern Italy by a validated ICP-MS method. Significant differences in trace elements were found in all the tissues examined (p < 0.05). The highest Sb and Cr levels were found in feathers samples with mean values of 0.019 mg/Kg and 0.085 mg/Kg, respectively. High Pb levels were found in muscle, with 23 % of the samples exceeding the limits set by the European Union. Cd was predominantly found in the kidney samples (0.76 mg/Kg). Vanadium was the less abundant trace metal, showing the highest concentrations in the liver (0.028 ± 0.011 mg/Kg). Higher As levels were found in muscle (0.02 ± 0.015 mg/Kg). No significant differences between sex and age classes (juveniles vs. adults) were found, nor were there correlations between morphometric parameters and trace metal/metalloid contents. Principal Component Analysis determined differences in metal accumulation between tissues. Feathers were confirmed as useful indicators of metal contamination. The results of this work confirmed that the accumulation of toxic elements in the tissues of woodcocks is primarily influenced by ecological traits such as feeding habits and migration status. Statistical analysis of the tissues would seem to exclude important accumulation phenomena of Pb. The high levels found in the muscle could be due to lead ammunition. This work provides the first data on the accumulation of As, Cr, Sb, and V in woodcocks tissue, providing a more comprehensive insight into the potential impact of these pollutants on birds.

Fabricating Spinel-Type High-Entropy Oxides of (Co, Fe, Mn, Ni, Cr)3O4 for Efficient Oxygen Evolution Reaction.

Fabricating efficient oxygen evolution reaction (OER) electrocatalysts is crucial for water electrocatalysis. Herein, the spinel-type high-entropy oxides of (Co, Fe, Mn, Ni, Cr)3O4 were synthesized through the high-temperature calcination approach. The influences of calcination temperatures on structures and electrochemical properties were investigated. The optimized catalyst of HEO-900 contains the hybrid structure of regular polyhedrons and irregular nanoparticles, which is beneficial for the exposure of electrochemically active sites. It was identified that the abundant high-valence metal species of Ni3+, Co3+, Fe3+, Mn4+, and Cr3+ are formed during the OER process, which is generally regarded as the electrochemically active sites for OER. Because of the synergistic effect of multi-metal active sites, the optimized HEO-900 catalyst indicates excellent OER activity, which needs the overpotential of 366 mV to reach the current density of 10 mA cm-2. Moreover, HEO-900 reveals the prominent durability of running for 24 h at the current density of 10 mA cm-2 without clear delay. Therefore, this work supplies a promising route for preparing high-performance multi-metal OER electrocatalysts for water electrocatalysis application.

Enhanced Co3O4 Nanoflakes Reactivity via Integrated Al-Doping and Metal Vacancy Engineering for Large Capacity Li-CO2 Batteries

Rechargeable Li-CO2 batteries are well-regarded for their high-energy, environmental friendliness, and resourceful use of CO2, but suffer from poor cycle reversibility. Herein, Al-doped Co3O4 nanoflakes featuring abundant metal vacancies (V-ACO/CC) were synthesized via a facile approach employing Al ions as both a dopant and sacrificial agents, which serve as high-efficient cathode catalyst for Li-CO2 batteries. Experiment results demonstrate that the incorporation of Al doping and metal vacancies modulates the electronic structure of Co-center and optimizes the growth path of discharge product. The cation vacancies generated by the sacrificed part of the Al atoms change the local charge distribution, strengthen the affinity of CO2 and reaction intermediates and facilitate the reversible decomposition of discharge products. Concurrently, the formation of covalent Al-O bonds by the remaining Al species reinforces the stability of nanostructures. Notably, the V-ACO/CC-based LCBs exhibit enhanced CO2 conversion kinetics, as evidenced by a high specific capacity (12.06 mAh cm−2 at 0.05 mA cm−2), fast rate capability and impressive stability (over 420 cycles under 0.1 mA cm−2).

First-Principles Study of High-Entropy Sulfides and their Alkali Metal-Doped Modification as Cathode Material for Sodium-Ion Batteries.

High-entropy materials (HEMs) have been explored as high-capacity cathode materials for sodium-ion batteries (SIBs) due to their excellent structural stability and abundant metal redox sites. Among them, high-entropy sulfides (HESs) have greater potential and more extensive research than high-entropy oxides, as they exhibit higher charging voltage and theoretical capacity as cathodes. Furthermore, alkali metal doping of HESs can further enhance their performance and broaden their application fields. Inspired by the cocktail effect of HEMs, we performed the first theoretical calculation of the properties of Na(MnFeCoNi)1/2S and its Li-doped derivative, Na7/8Li1/8(MnFeCoNi)1/2S, to understand their potential as SIB cathode materials. Using density functional theory based on first principles, we investigated the structure and electronic characteristics of Na(MnFeCoNi)1/2S and Na7/8Li1/8(MnFeCoNi)1/2S, and calculated their theoretical voltage and capacity, respectively. Compared with Na(MnFeCoNi)1/2S, Na7/8Li1/8(MnFeCoNi)1/2S showed better electronic performance in reducing the band gap and increasing the density of states, ultimately providing a specific capacity of 160.3 mAh ⋅ g-1 and a charging voltage of 4.85 V in sodium-ion storage. Moreover, Na7/8Li1/8(MnFeCoNi)1/2S exhibited remarkable structural stability throughout the sodium-ion deintercalation process, thus it can be reasonably concluded that Na7/8Li1/8(MnFeCoNi)1/2S can serve as an excellent cathode material for future SIB applications.

A Dynamical Model for IRAS 00500+6713: The Remnant of a Type Iax Supernova SN 1181 Hosting a Double Degenerate Merger Product WD J005311

IRAS 00500+6713 is a hypothesized remnant of a Type Iax supernova SN 1181. Multiwavelength observations have revealed its complicated morphology; a dusty infrared ring is sandwiched by the inner and outer X-ray nebulae. We analyze the archival X-ray data taken by XMM-Newton and Chandra X-ray Observatory to constrain the angular radius, mass, and metal abundance of the X-ray nebulae, and construct a theoretical model describing the dynamical evolution of IRAS 00500+6713, including the effects of the interaction between the SN ejecta and the intense wind enriched with carbon-burning ashes from the central white dwarf (WD) J005311. We show that the inner X-ray nebula corresponds to the wind termination shock while the outer X-ray nebula to the shocked interface between the SN ejecta and the interstellar matter. The observed X-ray properties can be explained by our model with an ejecta kinetic energy of E ej = (0.77–1.1) × 1048 erg, an ejecta mass of M ej = 0.18–0.53 M ⊙, if the currently observed wind from WD J005311 started to blow t w ≳ 810 yr after the explosion, i.e., approximately after 1990 CE. The inferred SN properties are compatible with those of Type Iax SNe and the timing of the wind launch may correspond to the Kelvin–Helmholtz contraction of the oxygen–neon core of WD J005311 that triggered a surface carbon burning. Our analysis supports that IRAS 00500+6713 is the remnant of SN Iax 1181 produced by a double degenerate merger of oxygen–neon and carbon–oxygen WDs, and WD J005311 is the surviving merger product.

Solar Models and Astrophysical S-factors Constrained by Helioseismic Results and Updated Neutrino Fluxes

The ratio of metal abundance to hydrogen abundance of the solar photosphere, (Z/X) s , has been revised several times. Standard solar models, based on these revised solar abundances, are in disagreement with seismically inferred results. Recently, Magg et al. introduced a new value for (Z/X) s , which is still under debate in the community. The solar abundance problem or solar modeling problem remains a topic of ongoing debate. We constructed rotating solar models in accordance with various abundance scales where the effects of convection overshoot and enhanced diffusion were included. Among these models, those utilizing Magg’s abundance scale exhibit superior sound speed and density profiles compared to models using other abundance scales. Additionally, they reproduce the observed frequency separation ratios r 02 and r 13. These models also match the seismically inferred surface helium abundance and convection zone depth within the 1σ level. Furthermore, the calculated neutrino fluxes from these models agree with detected ones at the level of 1σ. We found that neutrino fluxes and density profile are influenced by nuclear reactions, allowing us to use the combination of detected neutrino fluxes and seismically inferred density for diagnosing astrophysical S-factors. This diagnostic approach shows that S 11 may be underestimated by 2%, while S 33 may be overestimated by about 3% in previous determinations. The S-factors favored by updated neutrino fluxes and helioseismic results can lead to significant improvements in solar models.

Metal factories in the early Universe

ABSTRACT We have estimated the mass of metals in the molecular gas in 13 dusty star-forming galaxies at $z \sim 4$ in which the gas, based on previous observations, lies in a cold rotating disc. We estimated the metal masses using either the submillimetre line or continuum emission from three tracers of the overall metal content – carbon atoms, carbon monoxide molecules, and dust grains – using the first simultaneous calibration of all three tracers. We obtain very similar mass estimates from the different tracers, which are similar to the entire metal content of a present-day massive early-type galaxy. We used the dynamical masses of these galaxies to estimate an upper limit on the mass of the molecular gas in each galaxy, allowing us to estimate a lower limit on the metal abundance of the gas, finding values for many of the galaxies well above the solar value. We show that the high metal masses and metal abundances are what is expected shortly after the formation of a galaxy for a top-heavy IMF. We suggest a scenario for galaxy evolution in which massive galaxies reach a high metal abundance during their formation phase, which is then gradually reduced by dry mergers with lower mass galaxies. We show that the metals in the outflows from high-redshift dusty star-forming galaxies can quantitatively explain the long-standing puzzle that such a large fraction of the metals in galaxy clusters ($\simeq$0.75) is in the intracluster gas rather than in the galaxies themselves.

Determination of potentially toxic heavy metals in selected wood treatment sites in Uasin Gishu County and their associated health concerns

One of the monumental environmental and public health concerns of our time lies in the use of toxic preservatives in wood treatment plants. In this investigation, we report the results of potentially toxic heavy metals from wood treatment plants in Uasin Gishu County. A 20 g ground and sieved soil sample from each sampling site Cheplaskei (CK), Outspan (OS) and Sukunanga (SK) was weighed and treated with 0.5 M nitric acid for 2 h. The sample was then analyzed for potentially toxic metals using inductively coupled plasma atomic emission spectroscopy (ICP-AES). The statistical treatment of the data was done using Principal component analysis (PCA) and Pearson’s correlation. The highest concentration of copper was observed at SK, which contributed approximately 37% of all the potentially toxic heavy metal content analyzed, whereas the concentration of lead was found to be about 33% of the total heavy metal content analyzed at the same sampling site. Furthermore, the most abundant metal in the sampled sites is manganese, which was found to be 390.0 ± 8.63, 279.0 ± 8.05and 44.5 ± 2.95 ppm in OS, CK, and SK, respectively. PCA showed that the heavy metals in the sample sites originated from two independent sources—natural and anthropogenic. Evidently from the concentration profile data, all the potentially toxic heavy metals had concentrations above the World Health Organization (WHO) acceptable limits, although, based on the contamination factors determined, the wood treatment sites are less polluted; however, there is need for regular monitoring to ensure adherence to proper public and environmental health practices.

Environmental risk assessment, spatial distribution, and abundance of heavy metals in surface sediments of Dal Lake-Kashmir, India

This study assesses the pollution levels of Dal Lake in Kashmir, India, focusing on the spatial distribution, abundance, and risk of heavy metals in surface sediments. Granulometric analysis revealed a complex interplay of sedimentation processes, characterized by a wide range of sand (1.25% to 47.03%), silt (2.65% to 58.21%), and clay (38.35% to 94.48%) contents across sediment samples. The average CaCO3 content of 18.65% is notably higher than observed in other regional and global lakes, indicating higher production or preservation of carbonates. The organic matter (OM) content within the sediment samples varied significantly, ranging from 3.9% to 25.01%, reflecting complex sedimentary dynamics. Utilizing environmental assessment indices (Contamination Factor, degree of contamination, Pollution Load Index, Potential ecological risk index, Enrichment Factor, and Geo-accumulation Index) and multivariate statistical analyses (Pearson's Correlation, Principal Component Analysis, Cluster Analysis), it examines the contamination by Iron, Manganese, Cobalt, Chromium, Copper, Nickel, Lead, and Zinc across 32 samples. Results indicate spatial variability in metal concentrations, with Cobalt ranging from 24.1178 ppm to 52.95 ppm and Iron from 25,800.99 ppm to 164,747.82 ppm, highlighting areas of significant contamination and potential ecological risks, especially from Nickel, which exceeds safe levels for benthic invertebrates. The Pollution Load Index suggests moderate contamination of the lake. These findings emphasize the urgent need for continuous monitoring and effective management to protect Dal Lake's ecological integrity.

Assessing an Abandoned Pyrite Cinder Deposit in Southeast Spain with Electrical Resistivity Tomography: A Case Study

Industrial activities have historically generated significant quantities of by-products, including pyrite cinders, a residue produced during the synthesis of sulphuric acid. This study presents a multidisciplinary approach to characterise an abandoned pyrite cinder deposit. Combining geophysical (electrical resistivity tomography—ERT), geochemical, and statistical methods, we assess the physicochemical properties of the deposit and its environmental implications. Our findings reveal the presence of heavy metals, with lead (7017.5 mg.kg−1) being the most concentrated element on the surface of the deposit, exceeding local legal thresholds by more than 163 times, posing environmental risks and inhibiting vegetation growth. Subsurface characterisation indicates a decreasing concentration trend of metals with depth, alongside variations in pH and electrical conductivity. Clustering analysis identifies groups of similar behaviours between resistivity, the most abundant heavy metals, and other variables, providing valuable insights into the complex interplay within the deposit. Our study underscores the importance of integrated approaches in assessing and managing hazardous waste sites, with implications for environmental remediation strategies.

N-doped hollow nanofibers loaded with RuCoNi ternary alloy as an efficient catalyst for hydrogen evolution reaction

Alloying noble metals with abundant transition metals is an effective strategy for preparing cost-effective electrocatalysts for efficient hydrogen evolution reaction. In this study, hollow carbon nanofibers loaded with RuCoNi ternary alloy nanofiber catalysts (RuCoNi/CNFs) were synthesized by coaxial electrostatic spinning and a high-temperature carbonization approach. The interconnected three-dimensional hollow nanofibers, uniformly loaded with RuCoNi alloy nanoparticles, provided a large specific surface area and a hierarchical porous structure to enhance the interaction between the electrolyte and the active sites. Additionally, the hollow structure facilitated active sites exposure, charge transport, and gas diffusion, resulting in excellent HER activity of RuCoNi/CNFs. The overpotential required to achieve a current density of 10 mA cm−2 under alkaline conditions was only 47 mV, outperforming the homemade Pt/C catalyst (54 mV). Moreover, the carbon structure acted as a conductive carrier for efficient electron transfer, protecting the alloy nanoparticles from aggregation and corrosion. The RuCoNi/CNFs demonstrated remarkable stability and durability, maintaining consistent performance even after 100 hours of continuous operation. Importantly, the catalyst also exhibited favorable HER activity (186 mV@100 mA cm−2) at high current density, highlighting its potential for practical applications in large-scale industry.

Improved Selectivity and Stability in Methane Dry Reforming by Atomic Layer Deposition on Ni-CeO2-ZrO2/Al2O3 Catalysts.

Ni can be used as a catalyst for dry reforming of methane (DRM), replacing more expensive and less abundant noble metal catalysts (Pt, Pd, and Rh) with little sacrifice in activity. Ni catalysts deactivate quickly under realistic DRM conditions. Rare earth oxides such as CeO2, or as CeO2-ZrO2-Al2O3 (CZA), are supports that improve both the activity and stability of Ni DRM systems due to their redox activity. However, redox-active supports can also enhance the undesired reverse water gas shift (RWGS) reaction, reducing the hydrogen selectivity. In this work, Ni on CZA was coated with an ultrathin Al2O3 overlayer using atomic layer deposition (ALD) to study the effects of the overlayer on catalyst activity, stability, and H2/CO ratio. A low-conversion screening method revealed improved DRM activity and lower coking rate upon the addition of the Al2O3 ALD overcoat, and improvements were subsequently confirmed in a high-conversion reactor at long times onstream. The overcoated samples gave an H2/CO ratio of ∼1 at high conversion, much greater than uncoated catalysts, and no evidence of deactivation. Characterization of used (but still active) catalysts using several techniques suggests that active Ni is in formal oxidation state >0, Ni-Ce-Al is most likely present as a mixed oxide at the surface, and a nominal thickness of 0.5 nm for the Al2O3 overcoat is optimal.

Airborne Aluminum as an Underestimated Source of Human Exposure: Quantification of Aluminum in 24 Human Tissue Types Reveals High Aluminum Concentrations in Lung and Hilar Lymph Node Tissues.

Aluminum (Al) is the most abundant metal in the earth's crust, and humans are exposed to Al through sources like food, cosmetics, and medication. So far, no comprehensive data on the Al distribution between and within human tissues were reported. We measured Al concentrations in 24 different tissue types of 8 autopsied patients using ICP-MS/MS (inductively coupled plasma-tandem mass spectrometry) under cleanroom conditions and found surprisingly high concentrations in both the upper and inferior lobes of the lung and hilar lymph nodes. Al/Si ratios in lung and hilar lymph node samples of 12 additional patients were similar to the ratios reported in urban fine dust. Histological analyses using lumogallion staining showed Al in lung erythrocytes and macrophages, indicating the uptake of airborne Al in the bloodstream. Furthermore, Al was continuously found in PM2.5 and PM10 fine dust particles over 7 years in Upper Austria, Austria. According to our findings, air pollution needs to be reconsidered as a major Al source for humans and the environment.

Time-Resolved X-ray Emission Spectroscopy and Synthetic High-Spin Model Complexes Resolve Ambiguities in Excited-State Assignments of Transition-Metal Chromophores: A Case Study of Fe-Amido Complexes.

To fully harness the potential of abundant metal coordination complex photosensitizers, a detailed understanding of the molecular properties that dictate and control the electronic excited-state population dynamics initiated by light absorption is critical. In the absence of detectable luminescence, optical transient absorption (TA) spectroscopy is the most widely employed method for interpreting electron redistribution in such excited states, particularly for those with a charge-transfer character. The assignment of excited-state TA spectral features often relies on spectroelectrochemical measurements, where the transient absorption spectrum generated by a metal-to-ligand charge-transfer (MLCT) electronic excited state, for instance, can be approximated using steady-state spectra generated by electrochemical ligand reduction and metal oxidation and accounting for the loss of absorptions by the electronic ground state. However, the reliability of this approach can be clouded when multiple electronic configurations have similar optical signatures. Using a case study of Fe(II) complexes supported by benzannulated diarylamido ligands, we highlight an example of such an ambiguity and show how time-resolved X-ray emission spectroscopy (XES) measurements can reliably assign excited states from the perspective of the metal, particularly in conjunction with accurate synthetic models of ligand-field electronic excited states, leading to a reinterpretation of the long-lived excited state as a ligand-field metal-centered quintet state. A detailed analysis of the XES data on the long-lived excited state is presented, along with a discussion of the ultrafast dynamics following the photoexcitation of low-spin Fe(II)-Namido complexes using a high-spin ground-state analogue as a spectral model for the 5T2 excited state.

Assessment of probable health risk of potentially toxic metals in irrigable wetland soils from Ogun and Lagos States, Southwestern Nigeria

ObjectiveThe present study aimed at investigating the probable health risk associated with potentially toxic metals (PTMs) in irrigable wetland soils from Ogun and Lagos states, Southwestern Nigeria. MethodologyA total of 36 composite soil samples were collected from twelve monitoring sites and analyzed for potentially toxic metals [cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), nickel (Ni), lead (Pb), and zinc (Zn)] using atomic absorption spectrophotometry. PTM data underwent inferential and descriptive statistical analysis using IBM SPSS. Health risk indices were assessed for hazard quotient (HQ), hazard index (HI), and cancer risk (CR) using the standard method. Ecological and pollution risks were also assessed. ResultsFe (1465±977 to 47,785±12,049 mg kg−1) was the most abundant metal observed in irrigable wetland soils. The distribution pattern of PTMs in irrigable wetland soils followed the decreasing order of Fe > Zn > Cu > Cr > Pb > Ni > Co > Cd. The pollution index risk indicated values greater than 1.0 for Cd (2.43–133), Zn (1.60–6.32), Cu (1.49–5.89), and Pb (1.15–2.94). Cadmium indicated a considerable ecological risk index (4002), a moderate-to-high pollution level according to the Nemerov integrated pollution index (12.33), and a very high enrichment factor (14.1–227). The HQs of PTMs were generally less than 1.0 for adults, while a HI greater than 1.0 was observed for children. The CRs exceeding the threshold limit of 1.0 × 10−4 were observed for Co, Cd, Cr, and Ni [at one or more sampling sites] in the wetland soils exposed to by adults and children. ConclusionIn this study, the irrigated wetland soils showed high ecological, pollution, and carcinogenic risks of Cd, particularly at the Odo Aro monitoring site. The findings from the study could offer a theoretical basis and data support for pollution monitoring, assessment, and control in the study area.

Evaluation of thermal conductivity models and dielectric properties in metal oxide-filled poly(butylene succinate-co-adipate) composites

This study examines how various nanofillers impact thermal conductivity, dielectric characteristics, and electromagnetic interference (EMI) shielding potential of bio-based and biodegradable poly(butylene succinate-co-adipate) (PBSA). TiO2, NiFe2O4, Fe2O3, and Fe3O4 were selected as fillers for nanocomposites at 4–50 vol.% (12–81 wt.%). The nanocomposites were analyzed in three domains: structural (scanning electron microscopy, energy dispersive X-ray spectroscopy mapping, density, tensile testing), thermal (light flash analysis, literature models), and dielectric (AC conductivity, permittivity, EM shielding effectiveness (SE)). The investigated fillers showed good dispersion and compatibility with the PBSA matrix. LFA was analyzed according to literature models, where Bruggeman and Agari models showed the best fit at high concentrations. The dielectric analysis revealed that most of the nanocomposites did not reach percolation; thus, producing thermally conductive plastics that are electrically insulating. EMI shielding was limited to frequencies below 10 Hz, with the notable exception of Fe3O4 (100 nm and loading of > 25 vol.%), which showed shielding at frequencies up to 105 Hz. The investigated composites based on a biodegradable polyester and abundant metal oxide nanofillers are suitable for the production of cheap, ecological, and electrically insulating heat dissipation solutions required for modern and lightweight applications.

Heavy metals pollution and ecological risk assessment around artisanal gold mines in Zamfara, Nigeria.

Heavy metals pollution and potential ecological risk index were assessed in artisanal gold mining areas of Zamfara state, Nigeria. Soil samples were collected from three mines namely Kwali (05°45.49'E-11°59.66'N), Duke (06°19.56'E-12°21.45'N) and Maraba (06°22.43'E-12°20.26'N) while a non-mining area; Kadauri (06°08.71'E-12°13.56'N) was also chosen as a control. Samples were analysed using atomic absorption spectrophotometer and the results obtained showed that; the most abundant metal was Pb (148.59 mg/kg) in Kwali and the least was Ni (1.25 mg/kg) in Kadauri while the metals generally occurred in the order; Pb > Fe > Au > Al > Zn followed by other metals in an unspecified manner. All metal concentrations differed significantly (P<0.05) across sampling stations except Mn and Zn and they were all above the WHO limit which portrays a health risk. A strong positive correlation was found between metal pairs with r ≥ 0.5 (*p<0.05) in about 70% of them indicating commonality of source. Pb, Cd, Al and Au had contamination factors > 1in all sampling locations indicating increment in their concentrations above the pre-anthropogenic activities reference levels. Geoaccumulation index showed concentrations above background values of Pb, Cd, Al and Au while potential ecological risk index was highest (782.79) in Kwali and lowest (142.15) in Kadauri. Two principal components accounted for about 99.64% of the total variation in metals concentration with PC1 (95.21%) and PC2 (4.43%). This study showed the influence of artisanal gold mining on heavy metals concentration and suggested regulation of these practices.

Investigation of Combustion and NO/SO2 Emission Characteristics during the Co-Combustion Process of Torrefied Biomass and Lignite.

This paper investigates the combustion characteristics and pollutant emission patterns of the mixed combustion of lignite (L) and torrefied pine wood (TPW) under different blending ratios. Isothermal combustion experiments were conducted in a fixed bed reaction system at 800 °C, and pollutant emission concentrations were measured using a flue gas analyzer. Using scanning electron microscopy (SEM) and BET (nitrogen adsorption) experiments, it was found that torrefied pine wood (TPW) has a larger specific surface area and a more developed pore structure, which can facilitate more complete combustion of the sample. The results of the non-isothermal thermogravimetric analysis show that with the TPW blending ratio increase, the entire combustion process advances, and the ignition temperature, maximum peak temperature, and burnout temperature all show a decreasing trend. The kinetic equations of the combustion reaction process of mixed gas were calculated by Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) kinetic equations. The results show that the blending of TPW reduces the activation energy of the combustion reaction of the mixed fuel. When the TPW blending ratio is 80%, the activation energy values of the mixed fuel are the lowest at 111.32 kJ/mol and 104.87 kJ/mol. The abundant alkali metal ions and porous structure in TPW reduce the conversion rates of N and S elements in the fuel to NO and SO2, thus reducing the pollutant emissions from the mixed fuel.

CCD UBV(RI)KC photometry and dynamics of the open cluster NGC 1513

ABSTRACT We derive astrophysical parameters of the open cluster NGC 1513 by means of colour indices built with new CCD UBV(RI)KC photometry. Based on early-type members, the mean foreground reddening and total to selective extinction ratio are E(B − V) = 0.79 ± 0.09 mag and RV = 2.85 ± 0.05. Through the differential grid method, we derive the metal abundance [Fe/H] = −0.06 dex (Z = +0.013), which is consistent with the value [Fe/H] = −0.088 of the bright giant member – LAMOST 695710060. Z = +0.013 isochrone fit to the V × (B − V) colour–magnitude diagram leads to a turn-off age of 224 ± 27 Myr (thus an intermediate-age cluster), and a distance modulus of (V0 − MV) = 10.90 ± 0.15 mag, thus implying a distance from the Sun d = 1514 ± 105 pc. Within the uncertainties, our photometric distance is consistent with the value d = 1435 ± 14 pc from the Gaia DR3 parallax. We find signs of small mass segregation through a minimum spanning tree analysis for the 190 most massive stars, together with the rather steep mass function (χ = +2.39) slope. The high core to half-light radius ratio Rcore/Rh = 0.82, together with the compact half-light to tidal radius ratio Rh/Rt = 0.22, suggest that it is probably related to cluster-formation effects, due to little dynamical evolution, instead of driving its dynamical evolution by internal relaxation. Indeed, NGC 1513 is located in the second quadrant (ℓ = 152${_{.}^{\circ}}$59 and Galactocentric distance RGC = 9.57 kpc), which tends to minimize tidal effects by external processes and tidal disruption. Therefore, internal mass segregation effects in NGC 1513 seem to be more efficient than cluster evaporation processes. We find that NGC 1513 migrated about 0.50 kpc from its birth place.