Variations In Chemical Composition Research Articles

Zooming in the plastisphere: the ecological interface for phytoplankton-plastic interactions in aquatic ecosystems.

Phytoplankton is an essential resource in aquatic ecosystems, situated at the base of aquatic food webs. Plastic pollution can impact these organisms, potentially affecting the functioning of aquatic ecosystems. The interaction between plastics and phytoplankton is multifaceted: while microplastics can exert toxic effects on phytoplankton, plastics can also act as a substrate for colonisation. By reviewing the existing literature, this study aims to address pivotal questions concerning the intricate interplay among plastics and phytoplankton/phytobenthos and analyse impacts on fundamental ecosystem processes (e.g. primary production, nutrient cycling). This investigation spans both marine and freshwater ecosystems, examining diverse organisational levels from subcellular processes to entire ecosystems. The diverse chemical composition of plastics, along with their variable properties and role in forming the "plastisphere", underscores the complexity of their influences on aquatic environments. Morphological changes, alterations in metabolic processes, defence and stress responses, including homoaggregation and extracellular polysaccharide biosynthesis, represent adaptive strategies employed by phytoplankton to cope with plastic-induced stress. Plastics also serve as potential habitats for harmful algae and invasive species, thereby influencing biodiversity and environmental conditions. Processes affected by phytoplankton-plastic interaction can have cascading effects throughout the aquatic food web via altered bottom-up and top-down processes. This review emphasises that our understanding of how these multiple interactions compare in impact on natural processes is far from complete, and uncertainty persists regarding whether they drive significant alterations in ecological variables. A lack of comprehensive investigation poses a risk of overlooking fundamental aspects in addressing the environmental challenges associated with widespread plastic pollution.

Diversity pattern and antibiotic activity of microbial communities inhabiting a karst cave from Costa Rica.

The studies of cave bacterial communities worldwide have revealed their potential to produce antibiotic molecules. In Costa Rica, ~400 caves have been identified; however, their microbial diversity and biotechnological potential remain unexplored. In this work, we studied the chemical composition and microbial diversity of a Costa Rican cave (known as the Amblipigida cave) located in Puntarenas, Costa Rica. Additionally, through culture-dependent methods, we evaluated the potential of its microbiota to produce antibiotic molecules. Mineralogical and elemental analyses revealed that the Amblipigida cave is primarily composed of calcite. However, small variations in chemical composition were observed as a result of specific conditions, such as light flashes or the input of organic matter. The 16S rRNA gene metabarcoding revealed an extraordinarily high microbial diversity (with an average Shannon index of ~6.5), primarily comprising bacteria from the phyla Pseudomonadota, Actinomycetota, Firmicutes and Acidobacteriota, with the family Pseudomonadaceae being the most abundant. A total of 93 bacteria were isolated, of which 15% exhibited antibiotic activity against at least one Gram-positive or yeast strain and were classified within the genera Lysobacter, Streptomyces, Pseudomonas, Brevundimonas and Bacillus. These findings underscore the highly diverse nature of cave microbiota and their significant biotechnological potential, particularly in the production of antibiotic compounds.

Research Progress of High-entropy Oxides for Electrocatalytic Oxygen Evolution Reaction.

High-entropy oxides (HEOs), similar to high-entropy materials (HEMs), have "four-core effects", i. e., high-entropy effect, delayed diffusion effect, lattice distortion effect and cocktail effect, which have attracted more and more attention in the scientific field of renewable energy technology due to their unique structural characteristics, variable chemical composition and corresponding functional properties. HEOs have become potential candidates for electrocatalytic oxygen evolution reaction (OER), which is a key half reaction for electrolytic CO2, nitrogen reduction, and water electrolysis. However, the precise synthesis of HEOs with a wide range of components and structures is challenging, not to mention their active and stable operation for OER. In this paper, we review the recent advancements in the electrocatalytic oxygen evolution facilitated by HEOs in water electrolysis. We analyze these developments from the perspectives of activity and stability in acid and alkaline conditions, respectively. Furthermore, we summarize the design from the aspect of element composition, structure, morphology, and catalyst-support interactions, along with related reaction mechanism of HEOs. Additionally, we discuss the current challenges faced by HEOs in the field of OER and suggest potential directions for the future development of HEOs beyond water electrolysis application.

Discriminative characteristics of hydrochemical components and sedimentary organic matter in Korean coastal aquaculture systems during summer

Understanding the spatial distribution and sources of sedimentary organic matter (OM) in coastal environments is crucial for effective water quality management and the preservation of ecosystem health. Although extensive research has been conducted on OM dynamics, there remains a gap in understanding the ongoing biogeochemical processes in Korean coastal aquaculture zones, particularly during the summer season. To address this gap, we investigated the spatial variation of water chemical properties and isotopic composition of sedimentary OM to trace the composition, source, and reactivity of mixed OM in aquaculture systems along the Korean coast during the summer season. The isotopic approach was applied to surface sediments from five sections: western (W)-1, W-2, southern (S)-1, S-2, and eastern (E)-1. With respect to increased nutrients (mainly nitrate; 1.2 ± 0.6 mg/L) by dam-water discharge near W sections, our isotopic signatures revealed that a substantial fraction of sedimentary OM might dominantly originated from autochthonous OM source (algae; 36.5%) related to the increase of terrestrial nutrients. Simultaneously, the deposition of allochthonous OM (aquacultural feces; 44%) was predominant in the S-2 sections. The 34S-depleted patterns (approximately -7.2‰) in the S-2 section was indicative of active sulfate reduction occurring at the sedimentary boundary. Therefore, together with the precise determination of ongoing OM, our isotopic results provide valuable insights for effectively managing water-sedimentary qualities under the increase of anthropogenic contamination.

Structural nature of pyroelectric effect revisited: Experimental and theoretical studies of synthetic Ni,Al - rich tourmaline

Tourmaline, the first pyroelectric material discovered, is also a promising borosilicate material with non-linear optical and luminescence properties, high thermal stability, high hardness and variable chemical composition. The structural nature of pyroelectricity in tourmaline is a subject of scientific debate since it requires precise structural studies and measurements at elevated temperatures. Here, an in situ high temperature single-crystal and powder X-ray diffraction studies (up to ∼1000 °C) and the direct pyroelectric measurements (up to ∼200 °C) of synthetic Ni, Al-rich tourmaline were performed. The pyroelectric coefficient was calculated from the structural data. The results demonstrate that polyhedra XO9, YO6 and ZO6 exert the greatest influence on the pyroelectric effect. The pyroelectric coefficient of tourmaline is practically independent of boron-oxygen triangles and silicon-oxygen tetrahedra. The primary pyroelectric coefficient of tourmalines could be calculated from single crystal structural data. This study contributes to the synthesis of tourmalines with the required pyroelectric properties and may be used for the study of the nature and properties of other pyroelectric materials.

Metabolomic characteristics and anthraquinones accumulation patterns of Rhubarb in different tissues and roots from different developmental stages

Rhubarb’s multifaceted value in culinary and medicine is renowned, especially Rheum tanguticum (Rhubarb), whose bountiful content of anthraquinones (AQs) makes it increasingly attractive in the realms of dietary supplements and natural edible pigments. Current understanding of the spatiotemporal dynamics of AQs accumulation in Rhubarb remains limited, and the knowledge of other valuable metabolites is even more scarce. This gap limits the ability to fully explore Rhubarb's potential as a food ingredient and hinders its efficient use in food development, potentially leading to unnecessary resource waste. This study integrated widely targeted metabolomics and AQs quantification to determine the metabolic profiles in four tissues and the roots at three developmental stages in Rhubarb. The high levels of malic and citric acids in the stems paved the way for their use in flavored beverages and substantiated the practice of traditional consumption. The abundance of flavonoids in the leaves and seeds, and the AQs, phenolic acids of the seeds, which potentially bestowed upon them exceptional antioxidant capabilities, underscore the significant potential of edible product development. The widespread traditional use of roots was mirrored by the preferential accumulation of AQs, and the roots' value escalated in tandem with the time-accumulated increase of AQs. The root bark and root tip with high AQs should be given attention in production and not simply discarded. This research clarifies the chemical composition and spatiotemporal variation patterns of Rhubarb’s characteristic components, offering valuable scientific insights for their efficient use and value enhancement in the food industry.

Microstructural properties of Asian hornet nest paper-like materials: Preliminary step towards biomimicry materials for civil engineering applications

This paper presents a comprehensive examination of the microstructure and mineralogy of the paper-like material found in Asian hornet nests (referred to as AHN P-LM) and the nearby tree leaves, utilising scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) and X-ray diffraction (XRD). The analysis conducted through SEM-EDS demonstrates that AHN P-LM is primarily composed of plant fragments, with slight traces of inorganic substances (such as CaOx). The thread-like morphologies observed in the SEM analysis, which are linked to the secretion of hornets, warrant attention due to their significance in understanding the microstructure of AHN P-LM. The presence of nitrogen (N) in the EDS analysis of AHN P-LM, in contrast to its absence in analysed leaves, strongly implies that the nitrogen originates from hornet saliva. Additionally, SEM-EDS analysis revealed the impact of chemical composition variations on colour differences within AHN P-LM. Furthermore, X-ray diffraction analysis on ash samples from AHN P-LM confirmed the presence of minerals such as quartz, lime, phlogopite, and microcline. These findings about mineral composition align closely with results obtained from SEM-EDS analyses, presenting various aspects related to understanding the structure and compositional makeup of AHN P-LM. Biomimicry principles can be applied to draw inspiration from the AHN P-LM for replication in the civil engineering field, facilitating innovative solutions. Understanding hornet behaviour and nest material composition is essential. Future outlook includes utilising these materials in wood construction, 3D printing for structural components, shelters, infrastructure repair, green building, and architectural innovation.

The HST Large Programme on ω Centauri

We present a study of the white dwarf (WD) cooling sequence (CS) in the globular cluster (GC) Omega Centauri (or NGC 5139; hereafter, ω Cen), the primary goal of a dedicated Hubble Space Telescope (HST) programme. We find that the peak at the termination of the WD CS is located at mF606W = 30.1 ± 0.2 (equivalent to V ∼ 31). The brighter part of ω Cen’s WD CS is consistent with the presence of massive He-core WDs, in agreement with previous HST analyses with ultraviolet and blue filters. Comparative analyses of the WD luminosity function (LF) and theoretical counterparts show that a single-age population for the cluster is compatible with the data. However, an analysis of only the WD LF cannot entirely exclude the possibility of an age range, due to uncertainties in the present-day WD mass function, with a star formation history potentially spanning up to 5 billion years, predominantly comprising stars about 13 Gyr old, with a minority potentially as young as 8 Gyr. This underscores the need for global spectroscopic and photometric investigations that simultaneously include both the WD populations and the previous evolutionary phases, in order to fully understand the cluster’s diverse chemical compositions and ages.

Influence of the Blends of Sheep's and Goat's Milk on the Functional Properties and Volatile Compounds of Lighvan Cheese During Ripening: A Comparative Study

ABSTRACTIn this study, the influence of different ratios of sheep's to goat's milk (100:0, 75:25, 50:50, 25:75, and 0:100) on the content of functional metabolites and volatiles in Lighvan cheese throughout ripening was investigated. The samples were ripened under brine for 90 days and assessed in terms of variations in chemical composition, proteolysis, angiotensin‐converting enzyme, α‐amylase, and α‐glucosidase inhibitory activities, antioxidant power, total free amino acids, gamma amino butyric acid, free fatty acids, and volatile compounds. Results showed that by increasing the proportion of goat's milk, the samples exhibited higher antioxidant effect and inhibition of the angiotensin‐converting enzyme during ripening. After 90 days, an increase in α‐glucosidase and a slight decrease in α‐amylase inhibitory activities were observed in Lighvan cheese samples that were produced with 50%, 75% and 100% of goat's milk. In contrast, higher contents of sheep's milk led to a significant increase in the concentration of esters, terpenes and alcohols and a slight increase in gamma‐aminobutyric acid. The highest concentration of saturated and unsaturated fatty acids was observed in the cheese prepared with 100% raw sheep's milk after 90 days of ripening. The results revealed the possibility of making a functional white‐brined cheese by monitoring the type and ratio of the used milk and ripening time.

Navigating the depths of refuse-derived fuel in Canada: From heterogeneity to insightful analysis

ABSTRACT Refuse-derived fuel (RDF) presents inherent heterogeneity, encompassing diverse physical and chemical compositions. This study aims to comprehensively investigate the thermogravimetric characteristics of key RDF fractions and compare them with RDF compositions from Canada and other countries. A representative RDF sample was obtained using three ASTM standard procedures, including the quartering technique, manual sorting, and laboratory preparation. Five major RDF fractions – cardboard (46%), mixed papers (17%), mixed plastics (19%), other organics (3%), and fines (13%) – were manually separated and subjected to cryogenic grinding for characterization analysis. Thermogravimetric characterization at 20°C/min in a nitrogen atmosphere, along with proximate/ultimate analysis and heating value measurements, revealed significant variability in decomposition behavior. DTG analysis showed that LDPE exhibited the highest thermal stability, which peaks at 483.6°C, whereas cardboard and mixed paper underwent single-step decomposition, peaks at 361.4°C, and 359.3°C, respectively. In contrast, mixed plastics, other organics, fines, and raw RDF displayed complex, multi-step decomposition behaviors, underscoring the heterogeneous nature of RDF and informing thermal processing optimization. The Canadian RDF sample showed notably higher cardboard 45% and fines content 13% compared to other studies from different countries averaged 25% cardboard, and 8% fines. Additionally, sorting a 2 kg representative sample required 5 man-hours per kilogram, highlighting the labor-intensive nature of the process.

Characterization of Lithium-Ion Battery Fire Emissions—Part 2: Particle Size Distributions and Emission Factors

The lithium-ion battery (LIB) thermal runaway (TR) emits a wide size range of particles with diverse chemical compositions. When inhaled, these particles can cause serious adverse health effects. This study measured the size distributions of particles with diameters less than 10 µm released throughout the TR-driven combustion of cylindrical lithium iron phosphate (LFP) and pouch-style lithium cobalt oxide (LCO) LIB cells. The chemical composition of fine particles (PM2.5) and some acidic gases were also characterized from filter samples. The emission factors of particle number and mass as well as chemical components were calculated. Particle number concentrations were dominated by those smaller than 500 nm with geometric number mean diameters below 130 nm. Mass concentrations were also dominated by smaller particles, with PM1 particles making up 81–95% of the measured PM10 mass. A significant amount of organic and elemental carbon, phosphate, and fluoride was released as PM2.5 constituents. The emission factor of gaseous hydrogen fluoride was 10–81 mg/Wh, posing the most immediate danger to human health. The tested LFP cells had higher emission factors of particles and HF than the LCO cells.

Synthesis, characterization, and electrical properties of Nd3+‐doped (Bi0.4Na0.2K0.2Ba0.2)TiO3 high‐entropy ceramics

AbstractRecently, high‐entropy perovskites have attracted considerable attention due to their diverse chemical composition and multifunctionality. In this study, the high‐entropy approach was employed in a (Bi0.4Na0.2K0.2Ba0.2)TiO3 matrix, and Nd3+ was introduced to enhance the configurational entropy and modify its dielectric and ferroelectric properties. Notably, despite Nd3+ doping, all samples maintained a tetragonal perovskite structure at room temperature. The configurational entropy increased with the Nd3+ concentration, consequently leading to a gradual decline in the ferroelectric properties along with the associated temperature (Tm) and maximum dielectric constant (εm). The P–E loops of the ceramics also became thinner as Pm and Pr decreased, resulting in a slow decrease in the recoverable energy density (Wrec) and a simultaneous increase in the energy storage efficiency (η). Especially, the energy storage performance reached its peak at an Nd3+ concentration of 12 mol%, exhibiting an energy storage efficiency of 85.8% and a recoverable energy storage density of 0.74 J/cm3 at a low electric field of 100 kV/cm. These results highlight the potential of this material for dielectric applications in low electric fields and contribute to the advancement of alternative high‐entropy energy storage perovskite ceramics.

Multi-omics analysis of chemical composition variation among different muscle types in Hu lamb.

Consumers' preferences for lamb meat vary greatly depending on the specific cut. Variations in the chemical composition across different muscle types play a crucial role in determining meat quality, particularly with regard to flavor. Therefore, it is essential to study the variations in chemical composition among different muscle types in lamb, as well as the mechanisms behind their formation, aiming to understand the flavor variation across the muscle types. Flank muscles showed significantly higher intramuscular fat content and muscle fiber diameter compared to triceps brachii and biceps femoris (BF), at the same time as displaying a significantly lower percentage of type I muscle fibers. Forty-three differentially abundant volatile compounds (DAVC) were identified across five muscles, with the majority of DAVCs being more abundant in the BF. In total, 161 differentially abundant lipids were identified across five muscles, with triglycerides (TG), phosphatidylcholines (PC), phosphatidyl ethanolamines (PE) and phosphatidylmethanol (PMeOH) showing a strong correlation with DAVCs. A lipid-gene regulatory network was established, encompassing 664 lipids and 11 107 genes, leading to the identification of pathways and genes that regulate the metabolism of PEs, PMeOH, PCs and TGs. The present study showed the significant variation in flavor compounds among the five edible muscles, as well as the potential reasons for their formation. The results potentially provide a theoretical foundation for improving the meat quality of lamb. © 2024 Society of Chemical Industry. Published by John Wiley & Sons Ltd.

Energy Values and Standardized Ileal Digestibility of Amino Acids in Fermented Soybean Meal Fed to Growing Pigs.

This study aimed to evaluate the digestible energy (DE), metabolizable energy (ME), and standardized ileal digestibility (SID) of amino acids (AA) in fermented soybean meal (FSBM) fed to growing pigs. In experiment 1, twenty-two growing pigs (Duroc × Landrace × Yorkshire; 32.0 ± 4.2 kg BW) were fed one of 11 diets in a replicated 11 × 3 incomplete Latin square design to determine the DE and ME of FSBM. The diets included a corn-based diet and 10 experimental diets formulated by replacing the corn with 29.10% FSBM. In experiment 2, eleven growing pigs (Duroc × Landrace × Yorkshire; 24.3 ± 2.3 kg BW) were surgically equipped with a T-cannula and arranged in an 11 × 6 incomplete Latin square design with 11 diets and six periods. The diets included an N-free diet and 10 experimental diets containing 40% FSBM as the sole source of AA. The results showed that the contents of dry matter (DM), gross energy, crude protein, crude fiber, neutral detergent fiber, acid detergent fiber, calcium, and phosphorus averaged 91.83% (ranging from 89.24 to 94.55%), 18.44 MJ/kg (ranging from 18.00 to 18.95 MJ/kg), 50.63% (ranging from 50.00 to 51.81%), 4.51% (ranging from 3.41 to 5.40%), 9.17% (ranging from 7.02 to 10.30%), 6.38% (ranging from 4.97 to 7.45%), 0.32% (ranging from 0.29 to 0.34%), and 0.67% (ranging from 0.61 to 0.84%), respectively. The average DE and ME were 17.55 and 16.33 MJ/kg DM, respectively, with ranges of 15.72 to 18.80 MJ/kg DM and 14.30 to 17.72 MJ/kg DM, respectively. Significant differences were observed in the SID of essential AA (p < 0.05), except for Thr and Arg. The SID of Lys, Met, Trp, and Thr ranged from 68.13 to 83.27% (mean = 76.62%), 62.23 to 89.30% (mean = 75.25%), 72.30 to 90.29% (mean = 80.96%), and 74.17 to 84.41% (mean = 77.90%), respectively. These results indicate significant variability in chemical composition, energy content, and the SID of AA among the selected FSBM samples. The chemical composition of FSBM can be used to predict DE and ME values.

Optimized thermal pretreatment for lignocellulosic biomass of pigeon pea stalks to augment quality and quantity of biogas production

By applying heat to the feedstock during the thermal treatment of biomass for the production of biogas, the organic material's biodegradability can be greatly increased. Biogas production is a huge research area for alternate energy production technology. Increased biodegradability, improved methane yield, pathogen, and weed seed destruction, and overall process efficiency are all benefits of this type of pretreatment. It is a useful pretreatment technique for maximizing the production of biogas because it can decrease inhibitory compounds, and increase the digestibility of biomass. This work focused on increasing the efficiency of biogas production from lignocellulosic biomass of pigeon pea stalks by a novel thermal pretreatment. The pigeon pea stalk is initially imposed to physical pretreatment (PT) by an automatic hammer mill which is considered as a base for comparing performance. Thermal pretreatment was carried out for one hour, and two hours durations at different temperatures like 100 °C, 125 °C, 150 °C, 175 °C, and 200 °C. Compared to physically pretreated pigeon pea stalks, 200ᴼC thermal pretreated pigeon pea stalks for two hours have produced 88.41 % higher biogas, 16.14 % increase of cellulose, 19.9 % higher volatile solid removal, and 3.94 % lesser lignin. The enhanced chemical characteristics were ensured by analyzing the chemical composition variations through the FTIR, XRD, and SEM images. So, this is recommended for enhanced biogas production.

A systematic study of Pseudobulbus Cremastrae seu Pleiones: Characteristics, Origin, chemical composition and toxicology

Ethnopharmacological relevancePseudobulbus Cremastrae seu Pleiones (PCSP) is a multi-source traditional Chinese medicine (TCM) with diverse chemical compositions and toxicity levels. The authenticity identification and safety evaluation of PCSP have attracted widespread attention in clinical applications. Aim of this studyThe objective of this study was to evaluate the authenticity and safety of commercially available PCSP. Materials and methodsMorphological and microscopic identification, HPLC chromatogram, UPLC-Q-TOF-MS/MS with molecular networking were applied to the authenticity identification of PCSP. The safety of different PCSPs was evaluated by acute toxicity in zebrafish at maximum non-lethal concentration (MNLC) and 10% lethal concentration (LC10). Intestinal toxicity of PCSP was assessed through histological staining, intestinal goblet cells, neutrophils, and intestinal opacity. ResultsFour sources of PCSP varied in size, epidermal longitudinal grooves, and microscopic features. GNPS analysis identified 61, 47, 44, and 56 chemical compounds in Cremastra appendiculate (CA), Oreorchis patens (Lindl.) Lindl. (OPL), Iphigenia indica A. Gray (IIG), and Tulipa edulis (Miq.) Baker (TEB). Colchicine and militarine, were discovered as distinguishing markers. Acute toxicity in zebrafish ranked as follows: IIG > OPL > CA > TEB. Further studies on the intestinal toxicity of the authentic PCSP (CA, OPL) showed that CA induced less damage with a smaller lumen area, fewer neutrophils and goblet cells, and reduced peristalsis inhibition compared to OPL, indicating greater safety. ConclusionFour different sources of PCSP were accurately distinguished based on three dimensions: character, components, and toxicity. OPL and CA were considered as genuine products, while CA with lower toxicity was more suitable for clinical applications.

Atomic and electronic properties of 2D Chevrel phases: A case study of the superatomic two-dimensional semiconductor Re6Se8Cl2

The design of two-dimensional superatomic materials, which form their atomic structures through covalently bonded clusters with variable chemical compositions, will enable the development of new materials with promised electronic properties that are beneficial for modern nanoelectronics. This paper presents ab initio calculations of the atomic and electronic structures of both bulk and 2D Re6Se8Cl2. The calculations were carried out using density functional theory, incorporating noncollinear spin density and the pseudopotential method. The results include data on the atomic structure, band gap value, formation energy of the Re6Se8Cl2 2D layer, and the redistribution of atomic charges within the structures. The differences in effective masses for electrons and holes in the two-dimensional and bulk Re6Se8Cl2 materials are demonstrated, along with an explanation of how these differences impact their transport properties. The findings are expected to be of great significance for the design, synthesis, and implementation of new two-dimensional superatomic materials with controlled properties in modern nanoelectronics.

Simultaneous comparison of the chemical composition and attributable source of PM2.5 during 2014–2018 in major metropolitan cities in South Korea: impacts of policy interventions

Abstract Ambient fine particulate matter (PM2.5) is one of the most concerning pollutants, characterized by its diverse chemical composition. Although various studies have revealed PM2.5 chemical components, there is limited knowledge on how to reduce PM2.5 concentrations through administrative policies focusing on source management. We compared PM2.5 compositional characteristics and performed source apportionment using the positive matrix factorization in four metropolitan cities (Seoul, Daejeon, Gwangju, and Ulsan) in South Korea from 2014 to 2018. The annual average of PM2.5 concentrations exceeded the annual national ambient air quality standard of 15 μg m−3 in all areas while secondary inorganic aerosols constituted the largest fraction of PM2.5. This implies that secondary formation from gaseous precursors in the atmosphere was the main factor contributing to ambient PM2.5. However, the concentrations of PM2.5 constituents varied significantly across cities, suggesting that PM2.5 is a heterogeneous pollutant considerably influenced by region-specific conditions. In line with the chemical composition, secondary nitrate, secondary sulfate, and mobile-related sources were found to be significant contributors of PM2.5. Additionally, the extent of contribution from each source varied across the study regions. We also evaluated the impacts of policy interventions by comparing the PM2.5 composition and source apportionment before and after the policies for improving air quality. Intensive programs focused on the vehicle sector in Seoul led to a considerable decrease in the concentrations of carbonaceous compounds and mobile-related sources. In addition, strengthened regulations on coal-fired power plants (CFPPs) since 2016 have influenced the contributions of coal combustion sources in two cities adjacent to the west coastal area, where approximately half of the CFPPs of the country are densely distributed. Overall, the study’s findings indicate that region-specific PM2.5 chemical constituents and source contributions should be considered for establishing PM2.5-related policies, considering the high heterogeneity of PM2.5.

Chemical Composition and Spectral Variation in Gem-Quality Blue Iron-Bearing Tourmaline from Brazil

This study, conducted a spectroscopic analysis of 10 gem-quality blue tourmaline samples from Minas Gerais, Brazil, focused on detailed variations in their infrared, Raman, and UV-VIS spectra. Conventional gemological tests, electron-probe microanalysis, infrared spectroscopy (mid- and near-infrared), Raman spectroscopy, and UV-visible spectroscopy were used to systematically analyze the chemical composition and spectral characteristics of the samples. The infrared spectra revealed vibrations of [YO6], [TO4], [BO3], [OH], and H2O groups, indicating different bonding profiles, with the [OH] vibrational frequency showing a direct correlation with FeO and MnO content. The Raman spectra primarily reflected the stretching vibrations of metal–oxygen bonds and hydroxyl groups, indicating the complexity of the local environment in the crystal structure. The UV-VIS spectra showed that the broad absorption band around 725 nm was due to intermetallic charge transfer between Fe2+ and Fe3+. This work provides new insights into the local bonding environment within the crystal structure by providing precise spectral data of natural blue tourmaline, and a more accurate classification and evaluation of blue tourmaline through fine spectral change characteristics related to crystal chemistry has important implications for both academic research and the gemstone industry.

Impacts of elevated anthropogenic emissions on physicochemical characteristics of black-carbon-containing particles over the Tibetan Plateau

Abstract. Black carbon (BC) in the Tibetan Plateau (TP) region has distinct climate effects that strongly depend on its mixing state. The aging processes of BC in the TP are subject to emissions from various regions, resulting in considerable variability of its mixing state and physicochemical properties. However, the mechanism and magnitude of this effect are not yet clear. In this study, field observations on physicochemical properties of BC-containing particles (PMBC) were conducted in the northeast (Xihai) and southeast (Lulang) regions of the TP to investigate the impacts of transported emissions from lower-altitude areas on BC characteristics in the TP. Large spatial discrepancies were found in the chemical composition of PMBC. Both sites showed higher concentrations of PMBC when they were affected by transported air masses outside the TP but with diverse chemical composition. Source apportionment for organic aerosol (OA) suggested that primary OA in the northeastern TP was attributed to hydrocarbon OA (HOA) from anthropogenic emissions, while it was dominated by biomass burning OA (BBOA) in the southeastern TP. Regarding secondary aerosol, a marked enhancement in nitrate fraction was observed on aged BC coating in Xihai when the air masses were brought by updrafts and easterly winds from lower-altitude areas. With the development of boundary layer, the enhanced turbulent mixing promoted the elevation of anthropogenic pollutants. In contrast to Xihai, the thickly coated BC in Lulang was mainly caused by elevation and transportation of biomass burning plumes from south Asia, showing a large contribution of secondary organic aerosol (SOA). The distinct transported emissions lead to substantial variations of both chemical composition and light absorption ability of BC across the TP. The thicker coating and higher mass absorption cross-section (MAC) of PMBC in air masses elevated from lower-altitude regions reveal the promoted BC aging processes and their impacts on the mixing state and light absorption of BC in the TP. These findings emphasize the vulnerability of plateau regions to influences of elevated emissions, leading to significant changes in BC concentration, mixing states and light absorption across the TP, all of which need to be considered in the evaluation of BC radiative effects for the TP region.