Carbon Ratios Research Articles

Phytoplankton stoichiometry along the salinity gradient under limited nutrient and light supply.

Ongoing climate warming alters precipitation and water column stability, leading to salinity and nutrient supply changes in the euphotic zone of many coastal ecosystems and semi-enclosed seas. Changing salinity and nutrient conditions affect phytoplankton physiology by altering elemental ratios of carbon (C), nitrogen (N) and phosphorus (P). This study aimed to understand how salinity stress and resource acquisition affect phytoplankton stoichiometry. We incubated a phytoplankton polyculture composed of 10 species under different light, inorganic nutrient ratio and salinity levels. At the end of the incubation period, we measured particulate elemental composition (C, N and P), chlorophyll a and species abundances. The phytoplankton polyculture, dominated by Phaeodactylum tricornutum, accumulated more particulate organic carbon (POC) with increasing salinity. The low POC and low particulate C:N and C:P ratios toward 0psu suggest that the hypoosmotic conditions highly affected primary production. The relative abundance of different species varied with salinity, and some species grew faster under low nutrient supply. Still, the dominant diatom regulated the overall POC of the polyculture, following the classic concept of the foundation species.

Altitude Distribution Characteristics of Farmland Soil Bacteria in Loess Hilly Region of Ningxia

It is of great significance for the conservation of biodiversity in farmland ecosystems to study the diversity, structure, functions, and biogeographical distribution of soil microbes in farmland and their influencing factors. High-throughput sequencing technology was used to analyze the distribution characteristics of soil bacterial diversity, community structure, and metabolic function along elevation and their responses to soil physicochemical properties in farmland in the loess hilly areas of Ningxia. The results showed that:① The Alpha diversity index of soil bacterial was significantly negatively correlated with elevation (P < 0.05) and showed a trend of decreasing and then slightly increasing along the elevation. ② Seven phyla, including Proteobacteria, Actinobacteria, and Acidobacteria, were the dominant groups, and five of them showed highly significant differences between altitudes (P < 0.01). ③ At the secondary classification level, there were 36 metabolic functions of bacteria, including membrane transport, carbohydrate metabolism, and amino acid metabolism, of which 22 showed significant differences, and 12 showed extremely significant differences among different altitudes. ④ Pearson correlation analysis showed that soil water content, bulk density, pH, and carbon-nitrogen ratio had the most significant effects on bacterial Alpha diversity, whereas soil nutrients such as total organic carbon, total nitrogen, and total phosphorus had significant effects on bacterial Beta diversity. ⑤ Mantel test analysis showed that the soil water content, total organic carbon, and carbon-nitrogen ratio affected bacterial community structure at the phylum level, and soil pH, total organic carbon, total nitrogen, total phosphorus, and carbon-nitrogen ratio were significantly correlated with bacterial metabolic function. Variance partitioning analysis showed that soil water content had the highest explanation for the community structure of soil bacteria, whereas soil pH had the highest explanation for metabolic function. In conclusion, soil water content and pH were the main factors affecting the diversity, community composition, and metabolic function of soil bacteria in farmland in the loess hilly region of Ningxia.

Defective graphene-nanomaterials derived from banana-biomass for simultaneous electrochemical detection of xanthine, hypoxanthine, and uric acid: Insights from scanning electrochemical microscopy on edge and basal planes

While graphene and other graphene-based materials are promising for electrochemical sensors, developing a simple synthesis method and understanding how their structure affects their performance remains challenging. This study introduces a straightforward method to produce highly defective graphene-based nanomaterials (BP-GNMs) from banana pulp (BP) biomass. These BP-GNMs are suitable for efficiently detecting purine bases (xanthine (X), hypoxanthine (Hx), and uric acid (UA)) simultaneously using electrochemical techniques. The synthesis process involves heating at 180 °C in air. Compared to BP-derived graphene quantum dots (BP-GQDs) made using a hydrothermal method, BP-GNMs exhibit significantly better electrochemical activity. This is shown by well-defined, separated peaks with high currents in electrochemical measurements of the purine bases. In this study, we compared the physicochemical properties of BP-GNMs and BP-GQDs using various techniques like FESEM, TEM, XPS, UV–Vis, Raman, and FTIR spectroscopy. Our analysis revealed the formation of layered nanomaterials based on graphene, with sizes ranging from 400 mm to 10 μm. These nanomaterials exhibited a balanced ratio of sp2-bonded carbon (sp2C) to sp3-bonded carbon (sp3C). This balanced ratio is attributed to the presence of both defective basal planes (containing sp2C) and edge planes (containing sp3C) on the BP-GNMs. The heterogeneity on the surface in terms of edge and basal planes of the materials was viewed using scanning electrochemical microscopy (SECM) technique with ferrocene-carboxylic acid as a redox probe. As a practical application of this low-cost biomass material, an efficient and separation-free simultaneous electrochemical sensing of X, Hx and UA in various fishes and human urine samples were demonstrated with a recovery of 100±2%.

North and South in Medieval Iberia: A historical and environmental estimate through isotopic analyses.

The Middle Ages in the Iberian Peninsula is a period of special interest for studying the relationship of climate change with historical and socioeconomic processes. Between the 8th and 15th centuries AD, the Peninsula was characterized not only by complex political, cultural, and social transitions but also by major variations in the climate. The objective of this study was to examine differences in diet and mobility between distinct populations of the Peninsula and explore the possible relationship of diet, mobility, and culture with environmental variables and geographical settings. For this purpose, we obtained stable isotopic ratios of carbon and oxygen (δ13C and δ18O) from the enamel apatite of first upper incisors from 145 individuals at eight archeological sites that represent both Christian and Islamic communities and both rural and urban social settings. Results revealed a dietary difference between Christian and Islamic populations, observing a greater contribution of C4 plants, possibly sorghum, in the diet of the latter, especially in a rural setting. The disparity in oxygen isotopic ratios between populations from the North and South of the Peninsula is consistent with modern climatic differences between these regions. In this line, intraregional variability in oxygen isotopic ratios may hint at diachronic occupation phases under varying climatic conditions. The few isotopic outliers in our sample suggest overall low mobility levels.

ANN model of co-gasification process in bubbling fluidized bed: Contribution ratio analysis

Co-gasification of coal and biomass in a bubbling fluidized bed may offer an effective and economical method to partially replace coal to produce hydrogen, thereby addressing the objectives of achieving a carbon dioxide emissions peak and carbon neutrality. An Artificial neural network (ANN) model was utilized to simulate the hydrogen and other performance of co-gasification in the bubbling fluidized bed. Five types of ANN architectures were tested, including FFBP, CFBP, EFBP, LR, and NARX. Five optimization algorithms were also applied, including L-M, GA, GD, GDX, and PSO, to identify the optimal model to give a more accurate predicate the hydrogen production. The input data were derived from the ultimate analysis of the mixed coal and biomass, the proximate analyzes of mixed coal and biomass, and the operational conditions. The output data consisted of gas composition, carbon conversion, gasification efficiency, total gas yield, syngas yield, low and high heating values of the gas. The LR-PSO with 6 hidden neurons (R2 = 0.9995 and MSE = 0.1357) outperformed other ANN types and optimization algorithms. To further understand the performance of co-gasification, the influences of biomass to coal ratio, equivalence ratio, steam to carbon ratio and temperature on ratio of H2 to CO and syngas yield were predicted. The highest ratio of H2 to CO for the work of Li et al. (2010) [26], Song et al. (2013) [27] and Valdés et al. (2015) [28] were 0.7, 1.2 and 0.88, respectively. And those for syngas yield were 0.85, 1.09 and 1.55 m3/kg, respectively. To reveal the important factor on the ratio of H2 to CO, a detailed analyzed of the contribution ratio was conducted. The most critical factor affecting co-gasification performance in the work of Song et al. (2013) [27] were identified as SC ratio and temperature, which was higher than those of W and ER. The effect of SC exceeded that of T at SC ratio of 0.4, while it came to a reverse at temperature above 700 °C. These findings may serve as a valuable tool for adjusting the various factors to achieve the desired performance in the co-gasification of coal and biomass.

Correlation of methane production with physiological traits in Trichodesmium IMS 101 grown with methylphosphonate at different temperatures.

The diazotrophic cyanobacterium Trichodesmium has been recognized as a potentially significant contributor to aerobic methane generation via several mechanisms including the utilization of methylphophonate (MPn) as a source of phosphorus. Currently, there is no information about how environmental factors regulate methane production by Trichodesmium. Here, we grew Trichodesmium IMS101 at five temperatures ranging from 16 to 31°C, and found that its methane production rates increased with rising temperatures to peak (1.028 ± 0.040 nmol CH4 μmol POC-1 day-1) at 27°C, and then declined. Its specific growth rate changed from 0.03 ± 0.01 d-1 to 0.34 ± 0.02 d-1, with the optimal growth temperature identified between 27 and 31°C. Within the tested temperature range the Q10 for the methane production rate was 4.6 ± 0.7, indicating a high sensitivity to thermal changes. In parallel, the methane production rates showed robust positive correlations with the assimilation rates of carbon, nitrogen, and phosphorus, resulting in the methane production quotients (molar ratio of carbon, nitrogen, or phosphorus assimilated to methane produced) of 227-494 for carbon, 40-128 for nitrogen, and 1.8-3.4 for phosphorus within the tested temperature range. Based on the experimental data, we estimated that the methane released from Trichodesmium can offset about 1% of its CO2 mitigation effects.

Cyanobacteria-ferrihydrite aggregates, BIF sedimentation and implications for Archaean- Palaeoproterozoic seawater geochemistry

Abstract Precambrian banded iron formations (BIFs) are iron- and silica-rich (bio)chemical sediments that are widely believed to have been precipitated by microbial oxidation of dissolved Fe(II). The by-product of these metabolisms – insoluble ferric iron – would have settled through the water column, often as aggregates with the cell biomass. While the mineralogy, composition and physical properties of cell-iron mineral aggregates formed by anaerobic Fe(II)-oxidising photoferrotrophic bacteria have been extensively studied, there are limited studies that characterise cyanobacteria-iron mineral aggregates that formed during oxygenic photosynthesis. This gap in knowledge is important because it impacts sedimentation velocities and the Fe(III) to organic carbon (Corg) ratios in the marine sediment pile. Here, we used a recently introduced approach to precisely measure the sedimentation velocity of cyanobacteria-ferrihydrite aggregates and the Fe(III):Corg ratios of the cyanobacteria-ferrihydrite aggregates over a wide range of pH and initial Fe(II) concentrations under predicted Palaeoproterozoic atmospheric conditions. Our results indicate that it was highly unlikely BIFs formed at pH <7 via chemical oxidation due to the insufficient sedimentation velocity, even at the maximum predicted Fe(II) concentration of 1800 μM with excess oxygen. Instead, large Banded Iron Formation (BIF) deposits, such as those associated with the ca. 2.47 Ga Kuruman Formation in South Africa, would only had been deposited at minimum Fe(II) concentrations of 500 μM at pH 7 or 250 μM at pH 8. The Fe:Corg ratios in cyanobacteria-ferrihydrite sediments formed during initially anoxic Fe(II) oxidation experiments represent the maximum values under each condition because we specifically extracted samples after all Fe(II) was oxidised. The Fe(III) to organic carbon ratio was consistently below 4, which is also the ratio required for dissimilatory Fe(III) reduction (DIR). This result indicates that biomass in this case was in excess, which contradicts the low organic carbon content seen in most BIFs. Thus, we suggest that biomass was either physically separated from ferrihydrite aggregates during sedimentation under the influence of ocean currents and waves, or it was degraded prior to DIR. The mineralogical and geochemical evidences of both oxide and carbonate facies from the Kuruman Iron Formation (IF) suggest that ferrihydrite was most likely the precursor along with a significant initial organic carbon input, supporting the proposed cyanobacterially-mediated BIF depositional model and experimental results.

Compositional and functional succession of soil bacterial communities during long-term rice cultivation on saline-alkali soils: Insights derived from a new perspective of the core bacterial taxa

The conversion of saline-alkali soils into paddy fields for long-term rice cultivation involves multiple disturbances, and as a result, soil microbial communities are altered to adapt to a changing environment. A comprehensive understanding of the succession of soil bacterial communities that occurs during this process, however, is still lacking. In the present study, we utilized data obtained from rice paddies of different cultivation years to investigate the compositional and functional succession of the soil bacterial community. We focused on core bacterial taxa that were specifically enriched at different successional stages. Generalized joint attribute modeling (GJAM) was used to identify core bacterial taxa. Results indicated that bare saline-alkali soils shared few core amplicon sequence variants (ASVs) with paddy fields. Longimicrobiaceae from the phylum Gemmatimonadetes was dominant in bare saline-alkali soils, while their dominance was subsequently replaced by Burkholderiaceae and Pedosphaeraceae, phyla affiliated with the Proteobacteria and Verrucomicrobia, after 5 years and 23 years of rice cultivation, respectively. The abundance of nitrogen metabolism functions in the core bacterial community present in bare saline-alkali soils were higher than they were in other successional stages, while sulfur metabolism functions exhibited the opposite trend. These data indicate that the role of the core bacterial taxa in mediating nutrient cycling also changed and adapted to changing soil conditions as rice cultivation became established. Redundancy analysis (RDA) indicated that the compositions of the core bacterial community in Y0, Y5s, Y10s, and Y20s groups were driven by nitrate-nitrogen content, soil pH, available phosphorus content, and the ratio of total carbon to total nitrogen, respectively. In summary, the present study provides insights into the succession of soil bacterial communities and core bacterial taxa that occur during long-term rice cultivation.

Biochemical components of nitrogen balance in soil under crude oil contamination and phytoremediation

Introduction. Nitrogen availability in oil contaminated soil is adversely affected due to an increase in the inorganic carbon (C) and nitrogen (N) ratio, unfavorable changes in physical, chemical and biological properties of the soil. Phytoremediation of oil contaminated soil may have a positive effect on N cycling. Changes in soil enzyme activity, content of organic and mineral N in the soil can be used as indicators of nitrogen balance. This paper aims to identify some biochemical elements of N cycling in oil contaminated soil and the effect of plants in recovering N balance in the soil. Materials and Methods. In this study artificially oil contaminated soil (50 mL of crude oil per 1 kg of soil) was remediated by plants Zea mays L. and Vicia faba var. minor. Soil samples were collected on the 10th day after oil pollution, on the 22nd day (seeds were sown), on the 65th day (30 days of plants’ growth), and on the 95th day (60 days of plants’ growth). Soil without oil and plant vegetation was used as control. We determined the nodulation ability of soil, activity of soil protease and urease, content of labile organic nitrogen and free amino acids accumulation in the soil. Results. Our study revealed the absence of nodules on V. faba roots in oil contamination conditions. Protease activity was inhibited in oil contaminated soil compared to control. Under plant vegetation and oil contamination conditions, soil protease activity increased on the 65th day, and decreased on the 95th day compared to oil contaminated soil without plants. Amino acid concentration was significantly smaller for oil contaminated soil during the experiment than for soil without oil, but amino acid content was significantly greater for soil planted with Z. mays than for soil without plants. V. faba had a stimulating effect on amino acid accumulation only for uncontaminated soil compared to soil without plants. The results have shown that the urease activity decreased in oil contaminated soil during all experimental period. Results indicated that 22 days after oil pollution, the content of labile organic N decreased in oil contaminated soil, whereas on further stages of the experiment it was not significantly different compared to control. Significant reduction of labile N was revealed for oil contaminated soil with Z. mays plants on the 95th day and with V. faba plants on the 65th day compared to uncontaminated soil with plants. Conclusions. Oil-contamination had a negative effect on all studied biochemical characteristics of soil: protease activity, urease activity, labile organic nitrogen, free amino acids accumulation. In oil contamination conditions the positive effect of Z. mays and V. faba plants was determined for protease activity on the 65th day, a positive effect of Z. mays plants on accumulation of free amino acids accumulation was observed on the 95th day. The shortage of labile N in oil contaminated soil increased during phytoremediation. Therefore application of Z. mays and V. faba plants for optimization of biochemical components of N balance in oil contaminated soil may be controversial and requires further exploration.

Inactivation of guanylate kinase in Bacillus sp. TL7-3 cultivated under an optimized ratio of carbon and nitrogen sources influenced GTP regeneration capability and sporulation

Bacillus sp. TL7-3 has potential as a dietary supplement to promote human and animal health. It produces spores that can survive in harsh environments. Thus, when supplemented with nutrients, these spores can withstand the acidic pH of the stomach and resume vegetative development in the gut when exposed to growth-promoting conditions. Spores are formed as a cellular defense mechanism when a culture experiences stress and process optimization to achieve high spore production in a typical batch process remains challenging. Existing literature on the manipulation of gene expression and enzyme activity during batch cultivation is limited. Studies on the growth patterns, morphological changes, and relevant gene expression have aided in enhancing spore production. The present study used the response surface methodology for medium optimization. The model suggested that yeast extract and NH4Cl were significant factors controlling spore production. A comparison between the high weight ratio of carbon and nitrogen (C:N) substrates (8.57:1) in the optimized and basal media (0.52:1) showed an 8.76-fold increase in the final spore concentration. The expression of major genes, including codY, spo0A, kinA, and spo0F, involved in the sporulation was compared when cultivating Bacillus sp. TL7-3 in media with varying C:N ratios. At high C:N ratios, spo0A, kinA, and spo0F were upregulated, whereas codY was downregulated. This led to decreased guanylate kinase activity, resulting in a low guanosine triphosphate concentration and inactivation of CodY, thereby reducing the repression of spo0A and CodY-repressed genes and stimulating sporulation.

Response of carbon, nitrogen, and phosphorus in leaves of different life forms to altitude and soil factors in Tianshan wild fruit forest

IntroductionThe ecological stoichiometric ratio of carbon, nitrogen, and phosphorus is an important index to understand the utilization and distribution of plant nutrients.MethodTo explore how leaf carbon, nitrogen, and phosphorus contents, along with the stoichiometric ratio of different life forms of plants, respond to variations in altitude and soil physical and chemical properties, leaves and soil samples were collected from different life forms of plants at different altitudes (1,100~1,700 m) within the Guozigou region of the forest. Subsequently, the contents and ratios of carbon, nitrogen, and phosphorus in the leaves, as well as the physicochemical properties of the soil, were determined.ResultsThe results showed the following: (1) The three life forms of plants in the study area showed that the coefficient of variation of leaf carbon content was the smallest and the distribution was the most stable, while the coefficient of variation of carbon–nitrogen ratio was the largest. (2) Altitude had a significant effect on the carbon, nitrogen, and phosphorus contents of different life form of plants, among which the leaf nitrogen content of trees, shrubs, and herbs increased significantly with altitude (p < 0.01), the leaf phosphorus content of trees increased significantly with altitude (p < 0.01), and the leaf C:N of the three life form of plants decreased significantly with altitude (p < 0.01). The C:P of the arbor decreased significantly with altitude (p < 0.05), and the N:P of shrub and herb leaves increased significantly with altitude (p < 0.01). (3) Soil organic carbon and soil moisture content were the main environmental factors affecting the changes of carbon, nitrogen, and phosphorus in leaves of arbors, and nitrate nitrogen was the main environmental factor affecting the changes of carbon, nitrogen, and phosphorus in leaves of shrubs. Available phosphorus affected the changes of carbon, nitrogen, and phosphorus in the leaves of herbaceous plants.DiscussionThe results provide new insights into community-level biogeographical patterns and potential factors of leaf stoichiometry among plant life forms.

A review of carbon and phosphorus ratios in fresh water ecosystems dominated by phytoplankton: Effects of climate and geography

AbstractIn freshwater systems, carbon, nitrogen, and phosphorus are essential macroelements. Changing ecological communities as a result of anthropogenic activity and climate change has become a global issue. C:P has been demonstrated to be a trustworthy and sensitive assay for detecting and monitoring single or multiple species in a wide range of samples. We look at how C:P can be utilized to manage and reduce eutrophication and harmful algal blooms (HABs) in freshwater environments in this review work. Recent research show how C:P has been shown to be a useful strategy for gathering complete data in freshwater ecosystem studies. The total number of papers in ScienceDirect from 2000 to 2023 with the terms “carbon and phosphorus ratios, fresh water ecosystems, and phytoplankton” in the title, abstract, or keywords was acquired for this review. Based on the number of published research demonstrating an increased understanding of the basic scientific concepts behind the carbon and phosphorus ratio, the overall temporal trend in publications on the ratio showed a steady growth. Compared to eutrophic Lake Victoria, which had a C:P of 149, mesotrophic Lakes Malawi and Kivu had a ratio of 263. Applying the carbon‐to‐phosphorus ratio to lake and reservoir eutrophication assessment is feasible, and the increasing C:P ratio serves as a prime indicator for the initiation of lake and reservoir reoligotrophication. Our findings establish the framework for future study into the relationship between organic nutrients and eutrophication, as well as the ecological ramifications of these relationships in freshwater systems. Furthermore, our prediction was that increases in C:P would change the structure of phytoplankton communities.

Evaluation of residual sodium carbonate (RSC) and sodium adsorption ratio (SAR) in fresh water and laundry grey water for irrigation usage

AbstractThe current study was carried out to assess the suitability of laundry grey water (LGW) for reuse in irrigation so that it can help in the reduction of freshwater stress in irrigation sector. To address this objective, concentration of sodium (Na+), calcium (Ca2+), magnesium (Mg2+), carbonate (CO32−), bicarbonate (HCO3−), and phosphate (PO43−) were tested in fresh water (FW) collected before laundry washing and LGW generated after laundry washing from different households. The suitability of LGW for irrigation purpose was determined by using water quality indices such as Sodium adsorption ratio (SAR) and Residual Sodium Carbonate (RSC). The SAR values of FW at the rural and urban area sites varied from 0.84 to 1.10 and 0.82 to 4.30 respectively and remained in the excellent category for irrigation purpose. The SAR values of LGW at the rural and urban sites varied from 10.06 to 13.01 and 6.26 to 9.68, respectively. In contrast to the SAR values of the LGW at rural site, which remained under good quality category, SAR values remained under excellent category for irrigation purpose at urban sites. RSC values of FW and LGW were below 3.97 showing low or medium hazards associated with it for irrigation.

Influence of Growth Process on Suppression of Surface Morphological Defects in 4H-SiC Homoepitaxial Layers.

To address surface morphological defects that have a destructive effect on the epitaxial wafer from the aspect of 4H-SiC epitaxial growth, this study thoroughly examined many key factors that affect the density of defects in 4H-SiC epitaxial wafer, including the ratio of carbon to silicon, growth time, application of a buffer layer, hydrogen etching and other process parameters. Through systematic experimental verification and data analysis, it was verified that when the carbon-silicon ratio was accurately controlled at 0.72, the density of defects in the epitaxial wafer was the lowest, and its surface flatness showed the best state. In addition, it was found that the growth of the buffer layer under specific conditions could effectively reduce defects, especially surface morphology defects. This provides a new idea and method for improving the surface quality of epitaxial wafers. At the same time, we also studied the influence of hydrogen etching on the quality of epitaxial wafers. The experimental results show that proper hydrogen etching can optimize surface quality, but excessive etching may lead to the exposure of substrate defects. Therefore, it is necessary to carefully control the conditions of hydrogen etching in practical applications to avoid adverse effects. These findings have important guiding significance for optimizing the quality of epitaxial wafers.

Declining freshwater habitats in Greenland may shift diets of the ubiquitous wolf spider Pardosa glacialis

Freshwater habitats in Arctic landscapes provide essential food resources to predaceous terrestrial fauna. However, climate change threatens the continuation of aquatic resources as increased temperatures prompt widespread drying. We investigated how declines in surface waters in the Arctic may have implications for the diets of the wolf spider Pardosa glacialis (Araneae: Lycosidae), an abundant top predator in western Greenland known to consume both aquatic and terrestrial prey. We estimated the abundance of ground-dwelling prey taxa near and far from shallow ponds to compare resource availability for P. glacialis. We also measured the stable isotopes ratios of carbon and nitrogen of potential prey taxa and used linear mixing models to estimate the relative proportions of aquatic and terrestrial prey in the diets of P. glacialis collected near ponds versus drier, upland locations. Overall, near ponds there was a 3.7 times greater abundance of ground-dwelling organisms compared to locations far from ponds. Near ponds, depleted δ13C values of P. glacialis compared to the upland locations were explained by the consumption of aquatic insects, which were relatively depleted in 13C compared to terrestrial ground-dwelling and canopy taxa. Our linear mixing model indicated that the mean relative contribution of aquatic taxa to the diets of P. glacialis at pond locations was ~ 23% versus ~ 0% at upland locations, though these results were accompanied by significant uncertainty. Our results emphasize the importance of Arctic ponds in providing habitat to potential prey of terrestrial predators. We highlight how climate change, and the continued disappearance of aquatic habitats, could disrupt critical linkages between aquatic insects and terrestrial predators.

Efficient broadband sea urchin-like Fe3O4@C electromagnetic wave absorbing materials

The development of electromagnetic wave absorbing materials is crucial for various applications. Carbon materials and ferrite materials were recognized as ideal candidates of absorbing agents due to their respective dielectric loss and magnetic loss capabilities. In this study, Fe3O4@C were prepared using hydrothermal carbonization coupling method. The microstructure and morphology of Fe3O4@C were studied using SEM, TEM, XRD and TG. The results showed that Fe3O4@C exhibited a hollow sea urchin-like structure. The molar ratio of carbon to iron sources in the raw materials significantly influenced the crystal structure of the product. The growth mechanism of sea urchin-like Fe3O4@C was proposed. The carbon content in Fe3O4@C increased with the increase of molar ratio of glucose and iron (III) sulfate. The Fe3O4@C with carbon content of 31.10 % exhibited optimal absorption performance, with a minimum reflection loss of −57.1 dB at a matching thickness of 5.10 mm and effective absorption bandwidth (EAB) of 4 GHz. Electromagnetic parameters and absorption performance could be adjusted by varying the molar ratio of glucose and iron (III) sulfate. The unique sea urchin-like structure enhanced multiple reflection of electromagnetic waves. Interface polarization, conductivity loss and synergistic effect between carbon and Fe3O4 also contributed to the favorable absorption properties.

Increase in potato yield by the combined application of biochar and organic fertilizer: key role of rhizosphere microbial diversity.

The large-scale planting of potatoes leads to soil degradation, thus limiting the potato yield. An effective method of improving soil quality involves the combined application of biochar and organic fertilizer. However, the proportion of biochar and organic fertilizer at which potato yield can be improved, as well as the improvement mechanism, remain unclear. A combined application experiment involving biochar (B) and organic fertilizer (O) with four concentration gradients was conducted using the equal carbon ratio method. On this basis, rhizosphere soil fertility, bacterial community composition, and bacterial diversity in potato crops, as well as the potato yield difference under different combined application ratios, were investigated. Then, the direct and indirect effects of these factors on potato yield were analyzed. The results suggest that soil fertility was improved by the combined application of biochar and organic fertilizer, with the best effect being achieved at a ratio of B:O=1:2. The dominant bacterial communities in the potato rhizosphere included Proteobacteria, Actinobacteria, Gemmatimonadetes, Chloroflexi, and Bacteroidetes. When compared to the control, the relative abundance and diversity index of soil bacteria were significantly improved by the treatment at B:O=1:2, which exerted a stronger effect on improving the relative abundance of beneficial bacteria. Soil available phosphorus (AP), soil pH (SpH), and soil organic carbon (SOC) explained 47.52% of the variation in bacterial composition. Among them, the main factor was the content of soil available nutrients, while SpH generated the weakest effect. The bacterial diversity index showed a significant positive correlation with soil AP, SOC, available potassium (AK), total nitrogen (TN), and C/N ratio, and a significant negative correlation with SpH. Bacterial diversity directly affected the potato yield, while soil fertility indirectly affected potato yield by influencing the soil bacterial diversity. The combined application of biochar and organic fertilizer elevates potato yield mainly by improving the diversity of bacterial communities in potato rhizosphere soil, especially the combined application of biochar and organic fertilizer at a 1:2 ratio (biochar 0.66 t ha-1+organic fertilizer 4.46 t ha-1), which made the largest contribution to increasing potato yield.

Reduction of graphene oxide film on glass substrate using argon ion beam irradiation: A systematic study with X-ray photoelectron spectroscopy analysis

In our research, we explored a novel and eco-friendly method of utilizing argon ion beam irradiation to thin down graphene oxide (GO) films on glass substrates, aiming to enhance their mechanical, electrical, and optical properties. By employing high-energy argon ions, we developed a groundbreaking, environmentally conscious technique that not only permits micro-patterning directly on GO films but also facilitates concurrent material characterization. Varying the energy levels (1000, 2000, and 3000 eV) and exposure times (0 to 80 s, in 20-second increments), we meticulously examined the impact on carbon and oxygen atomic ratios of the GO using X-ray photoelectron spectroscopy (XPS) for in-depth analysis. Our findings revealed that increasing the argon ion beam energy to 2000 eV and extending the irradiation time significantly reduced oxygen content while increasing the carbon atomic ratio, indicating effective GO surface reduction. However, further increasing the energy to 3000 eV resulted in a slight increase in oxygen content and a decrease in the carbon atomic ratio compared to the energy 2000 eV, suggesting a decrease in reduction efficacy. This method's simplicity, eco-friendliness, and precision mark a significant advancement over traditional chemical reduction methods, offering a solid understanding of high-energy argon ion beam irradiation's effectiveness in GO reduction. Our comprehensive analysis, including survey and high-resolution C 1s and O 1s XPS spectra, highlights the surface chemistry modifications induced by this treatment, demonstrating the versatility of argon ion beam irradiation in producing reduced graphene oxide (rGO) for various applications.

Amorphous/Graphitic carbon phase engineering of Corrosion-Resistant Fe@C Core-Shell nanowires for optimized dipole polarization and enhanced microwave absorption

The study of designing and developing ferromagnetic nanocomposites with both microwave absorption (MA) and corrosion protection properties through microscopic heterogeneous interfacial engineering and crystal phase engineering remains challenging. In this study, Fe@C core–shell nanowires (FCNWs) are obtained by magnetic field-controlled in situ reduction method and annealing process to de-regulate the carbon shell thickness and carbon morphology. The enhancement of Fe-C heterogeneous relative interfacial effects and dielectric/magnetic response is revealed using density functional theory and simulated electromagnetic field distribution, and the modulation of the amorphous carbon/graphitic carbon ratio achieves the enhancement of dipole polarization in the low-frequency region. The FCNWs absorber had a minimum reflection loss (RLmin) of −47.6 dB at a thickness of 4.9 mm, and the maximum effective absorption bandwidth (EABmax) was achieved at 5.5 mm up to 4.0 GHz. In addition, the shielding effect of the graphitic carbon shell on the corrosion medium and the addition of additional electron conduction pathways allow the FCNWs absorber to obtain smaller corrosion currents and larger polarization resistances compared to Fe nanowires. Thus, modulation of atomic-scale heterogeneous interfaces and crystal phases has great potential in modulating the dielectric response.

Assessment of Nocturnal NOx Heterogeneous Reaction Mechanisms in the Community Multiscale Air Quality (CMAQ) Model

AbstractNitrogen oxides (NOx) have adverse human health impacts and play a central role in the production of ozone and PM2.5. Nighttime heterogeneous chemistry regulates the nocturnal reservoirs and sinks of NOx such as N2O5 removal and ClNO2 production. However, existing parameterizations of nocturnal NOx heterogeneous chemistry in air quality models do not capture the variability in observations. Here, we implemented for the first time in the Community Multiscale Air Quality (CMAQ) model the Gaston N2O5 uptake (γ(N2O5)) mechanism that accounts for the role of particulate organic matter in regulating N2O5 uptake and the Staudt ClNO2 yield (Φ(ClNO2)) mechanism that includes the role of reactive solutes in suppressing ClNO2 production. With the Gaston and Staudt parameterizations, the coarse mode contributed modestly to N2O5 loss (17.2%) but significantly to ClNO2 production (60.3%), highlighting the impact of coarse mode chemistry. The Gaston γ(N2O5) parameterization in the fine mode increased agreement between modeled N2O5 concentration and observations (RMSEnew = 0.37ppb) compared to the model default (RMSEdefault = 0.43ppb). The Gaston γ(N2O5) parameterization was overall biased low due to underestimates in modeled particle oxygen to carbon ratio (O:C). The Staudt Φ(ClNO2) parameterization resulted in further underestimation (NMBnew = −73.7%) compared to the model default (NMBdefault = −37.9%) because of underestimation of fine mode particle chloride concentration. We expect that the updated parameterizations may more accurately capture the mean state and variability in γ(N2O5) and Φ(ClNO2) under conditions where model particulate O:C and chloride are better represented.