Nitrogen Abundances Research Articles

Water-soluble organic and inorganic nitrogen in ambient aerosols over the Himalayan middle hills: Seasonality, sources, and transport pathways

Atmospheric nitrogen is ubiquitous in the environment and hence plays an essential role in the nutrient balance over the whole ecosystem. However, its abundance and characteristics, particularly in the Himalayas, are not well understood. Therefore, to understand the abundance, sources, and seasonality of soluble nitrogenous species in the middle hills of the central Himalayas, aerosol samples were collected at Dhulikhel in Nepal from January to December 2018. The results of this study revealed that water-soluble inorganic nitrogen (WSIN) contributed the most to water-soluble total nitrogen with an abundance of ammonium nitrogen (NH4+–N). Moreover, water-soluble organic nitrogen (WSON) contributed approximately 18% to aerosol total water-soluble nitrogen. The aerosol mass and WSIN species exhibited strong seasonality with considerably higher concentrations during dry periods and lower concentrations during the wet period. Furthermore, for dry periods, the HYSPLIT model revealed that nitrogen aerosols mainly originated from the Indo-Gangetic Plain region and were transported and deposited in the Himalayas through long-range atmospheric transport. The strong correlations of WSON with nssK+ (biomass burning) and nssCa2+ (crustal sources) and lack of a significant correlation with SO42− indicated that primary sources are responsible for generating WSON rather than secondary processes in the Himalayas. The estimated dry deposition fluxes for NO3−–N, NH4+–N, and WSON were 1.56, 8.35, and 4.06 kg ha−1 y−1, respectively. This study also shows that increasing air contaminants and emissions over South Asia can enter the Himalayas and affect the human health and ecology of this fragile area.

Density functional theory study of nitrogen-doped graphene as a high-performance electrocatalyst for CO2RR

Metal-free catalysts for the CO2 reduction reaction (CO2RR) is a research hotspot to enhance CO2 utilization as a way to counteract global warming. Nitrogen-doped graphene attracts attention because of the abundance of nitrogen and promising catalytic performance of graphene. In this work, we investigated various N-doped configurations and their corresponding catalytic abilities for CO2RR to ethanol via spin-polarized density functional theory (DFT) computations. The final results indicate that site 43 of binary-N-doped graphene had high CO2RR activity, stable adsorption of reactants, and good activation of CO2. The catalysis process demonstrated features of low free energy barriers in the rising stage and obvious facilitation of the potential-limiting step. Compared with a catalyst-free process, it can effectively improve the reaction activity. The results provide theoretical guidance for the design and preparation of high-performance CO2RR catalysts.

Biological nitrogen fixation detected under Antarctic sea ice

Nitrogen fixation is the primary source of reactive nitrogen in the ocean. Most ecological models do not predict nitrogen fixation in the Antarctic Ocean because of the low availability of iron and high abundance of nitrogen. Here we extensively examined nitrogen fixation in the Antarctic Ocean, and found substantial nitrogen fixation (maximum: 44.4 nmol N l−1 d−1) near the Antarctic coast, especially around ice-covered regions. The nitrogenase gene (nifH) was detected at all coastal stations, including stations where no nitrogen fixation was found. At the stations where nitrogen fixation was detected, the nitrogen-fixing cyanobacterium UCYN-A (Candidatus ‘Atelocyanobacterium thalassa’) dominated nifH gene expression, and the nifH sequence was identical to that of the major oligotype in tropical and subtropical oceans. Our results suggest that marine nitrogen fixation is a ubiquitous process in the global ocean, and that UCYN-A is the keystone species for making it possible. Observational evidence of cyanobacterial activity in the Antarctic Ocean suggests that nitrogen fixation could be a ubiquitous process in the global ocean.

Evolution of nitrogen cycling and primary productivity in the tropics during the Late Ordovician mass extinction

The late Ordovician is characterized by significant environmental changes in global climate, oceanic redox conditions, as well as a major disaster for marine organisms—the Late Ordovician mass extinction (LOME) (ca. 445 Ma). During this event, planktonic and benthic faunas as well as microbial communities were substantially influenced, and changes in the microbial ecosystems could provide useful clues for the dynamics of marine nutrients and primary production. Here, we utilize new nitrogen isotope (δ15Nbulk) and abundance data, as well as organic carbon accumulation rates (OCARs) from an Ordovician-Silurian (OS) deep marine section, Tianba, deposited under consistently anoxic water columns in the Yangtze Shelf Sea (South China), to unravel the evolution of nitrogen cycling and primary productivity. The OCARs for Tianba section were the lowest during the sea level lowstands and Hirnantian glaciation maximum but were high at the eve and aftermath of the Hirnantian glaciation maximum, consistent with the OCARs dynamics for another anoxic deep-water section located in Laurentia Block in the tropical ocean. Low OCARs mainly demonstrate that the marine primary productivity was low, with N2-fixers populating the ecosystems during the Hirnantian glaciation maximum as evidenced by the spatial distribution of δ15Nbulk values in the paleotropical waters. However, the high OCARs mainly imply high marine primary productivity right before and after the Hirnantian glaciation maximum in the paleotropics, which were likely fueled by fixed nitrogen sourced from upwellings. The spatial heterogeneity in δ15Nbulk values for the top of Wufeng Formation and coeval strata in the paleotropics suggests that fixed nitrogen species (including NH4+ and NO3−) in surface waters may vary in space. The cooccurrence of zooplankton extinction with spatial variation of δ15Nbulk values suggests that the dynamics of surface waters redox conditions could have played a significant role in the extinction pattern of planktonic faunas during the LOME-1.

Constraining photoionization models with a reprojected optical diagnostic diagram

ABSTRACT Optical diagnostic diagrams are powerful tools to separate different ionizing sources in galaxies. However, the model-constraining power of the most widely used diagrams is very limited and challenging to visualize. In addition, there have always been classification inconsistencies between diagrams based on different line ratios, and ambiguities between regions purely ionized by active galactic nuclei (AGNs) and composite regions. We present a simple reprojection of the 3D line ratio space composed of [N ii]λ6583/H α, [S ii]λλ6716, 6731/H α, and [O iii]λ5007/H β, which reveals its model-constraining power and removes the ambiguity for the true composite objects. It highlights the discrepancy between many theoretical models and the data loci. With this reprojection, we can put strong constraints on the photoionization models and the secondary nitrogen abundance prescription. We find that a single nitrogen prescription cannot fit both the star-forming locus and AGN locus simultaneously, with the latter requiring higher N/O ratios. The true composite regions stand separately from both models. We can compute the fractional AGN contributions for the composite regions, and define demarcations with specific upper limits on contamination from AGN or star formation. When the discrepancy about nitrogen prescriptions gets resolved in the future, it would also be possible to make robust metallicity measurements for composite regions and AGNs.

Most lithium-rich low-mass evolved stars revealed as red clump stars by asteroseismology and spectroscopy

Lithium has confused scientists for decades at almost each scale of the universe. Lithium-rich giants are peculiar stars with lithium abundances over model prediction. A large fraction of lithium-rich low-mass evolved stars are traditionally supposed to be red giant branch (RGB) stars. Recent studies, however, report that red clump (RC) stars are more frequent than RGB. Here, we present a uniquely large systematic study combining the direct asteroseismic analysis with the spectroscopy on the lithium-rich stars. The majority of lithium-rich stars are confirmed to be RCs, whereas RGBs are minor. We reveal that the distribution of lithium-rich RGBs steeply decline with the increasing lithium abundance, showing an upper limit around 2.6 dex, whereas the Li abundances of RCs extend to much higher values. We also find that the distributions of mass and nitrogen abundance are notably different between RC and RGB stars. These findings indicate that there is still unknown process that significantly affects surface chemical composition in low-mass stellar evolution.

Comprehensive analysis of the Ppatg3 mutant reveals that autophagy plays important roles in gametophore senescence in Physcomitrella patens

BackgroundAutophagy is an evolutionarily conserved system for the degradation of intracellular components in eukaryotic organisms. Autophagy plays essential roles in preventing premature senescence and extending the longevity of vascular plants. However, the mechanisms and physiological roles of autophagy in preventing senescence in basal land plants are still obscure.ResultsHere, we investigated the functional roles of the autophagy-related gene PpATG3 from Physcomitrella patens and demonstrated that its deletion prevents autophagy. In addition, Ppatg3 mutant showed premature gametophore senescence and reduced protonema formation compared to wild-type (WT) plants under normal growth conditions. The abundance of nitrogen (N) but not carbon (C) differed significantly between Ppatg3 mutant and WT plants, as did relative fatty acid levels. In vivo protein localization indicated that PpATG3 localizes to the cytoplasm, and in vitro Y2H assays confirmed that PpATG3 interacts with PpATG7 and PpATG12. Plastoglobuli (PGs) accumulated in Ppatg3, indicating that the process that degrades damaged chloroplasts in senescent gametophore cells was impaired in this mutant. RNA-Seq uncovered a detailed, comprehensive set of regulatory pathways that were affected by the autophagy mutation.ConclusionsThe autophagy-related gene PpATG3 is essential for autophagosome formation in P. patens. Our findings provide evidence that autophagy functions in N utilization, fatty acid metabolism and damaged chloroplast degradation under non-stress conditions. We identified differentially expressed genes in Ppatg3 involved in numerous biosynthetic and metabolic pathways, such as chlorophyll biosynthesis, lipid metabolism, reactive oxygen species removal and the recycling of unnecessary proteins that might have led to the premature senescence of this mutant due to defective autophagy. Our study provides new insights into the role of autophagy in preventing senescence to increase longevity in basal land plants.

Transcriptome-Wide Analysis of Nitrogen-Regulated Genes in Tea Plant (Camellia sinensis L. O. Kuntze) and Characterization of Amino Acid Transporter CsCAT9.1.

The vigor of tea plants (Camellia sinensis) and tea quality are strongly influenced by the abundance and forms of nitrogen, principally NO3−, NH4+, and amino acids. Mechanisms to access different nitrogen sources and the regulatory cues remain largely elusive in tea plants. A transcriptome analysis was performed to categorize differentially expressed genes (DEGs) in roots and young leaves during the early response to four nitrogen treatments. Relative to the continuously nitrogen-replete control, the three nitrogen-deprived and resupplied treatments shared 237 DEGs in the shoots and 21 DEGs in the root. Gene-ontology characterization revealed that transcripts encoding genes predicted to participate in nitrogen uptake, assimilation, and translocation were among the most differentially expressed after exposure to the different nitrogen regimes. Because of its high transcript level regardless of nitrogen condition, a putative amino acid transporter, TEA020444/CsCAT9.1, was further characterized in Arabidopsis and found to mediate the acquisition of a broad spectrum of amino acids, suggesting a role in amino acid uptake, transport, and deposition in sinks as an internal reservoir. Our results enhance our understanding of nitrogen-regulated transcript level patterns in tea plants and pinpoint candidate genes that function in nitrogen transport and metabolism, allowing tea plants to adjust to variable nitrogen environments.

Factors Influencing Survival Rates of Pronghorn Fawns in Idaho

ABSTRACTPronghorn (Antilocapra americana) occur throughout western North America. In Idaho, USA, following intensive hunting to reduce crop depredations in the late 1980s, pronghorn populations have not rebounded to desired levels. Because neonatal survival in ungulates is one factor limiting population growth, we evaluated cause‐specific mortality and the influence of intrinsic and extrinsic factors on survival rates of 217 radio‐collared pronghorn fawns across 3 study areas in Idaho during 2015–2016. For intrinsic variables, we determined the sex and body mass index (BMI) for each fawn. For extrinsic variables, we determined the abundance of predators and alternate prey, estimated the normalized difference vegetation index (NDVI) for 1 month pre‐ and post‐parturition, and measured fecal nitrogen and diaminopimelic acid (DAPA). We considered NDVI as a measure of plant productivity, and fecal nitrogen and DAPA as possible proxies of diet quality. We predicted NDVI, fecal nitrogen, and DAPA would be positively related to the nutritional status of females and positively related to fawn survival. We used Program MARK with known fate models to estimate semi‐monthly survival rates of pronghorn fawns for the first 4 months post‐parturition. During both years, the leading cause of fawn mortality was coyote (Canis latrans) predation (58%), followed by unknown causes of mortality (18%), unknown predation (12%), predation by bobcats (Lynx rufus; 6%), predation by golden eagles (Aquila chrysaetos; 3%), and other (3%). Mean fawn survival for the 4 months post‐parturition across years and study sites was 0.42 ± 0.04 (SE; range = 28–62%). The top survival model included BMI, lagomorph abundance, and DAPA and had a model weight of 83.3%. All 3 variables were positively related to pronghorn fawn survival. Because females with increased nutrition generally have heavier fawns, BMI was likely correlated to diet quality, which was supported by the positive relationship between DAPA and fawn survival. We hypothesize that high lagomorph abundance created an alternate prey base to buffer coyotes from preying on pronghorn neonates. We found no influence of measures of NDVI (pre‐ and post‐parturition), fecal nitrogen, or predator abundance on fawn survival. Management actions providing high‐quality forage for pronghorn are likely to contribute to production of heavier fawns having the highest chance of survival. © 2020 The Wildlife Society.

Nitrogen removal and abundances of associated functional genes in rhizosphere and non-rhizosphere of a vertical flow constructed wetland in response to salinity

It investigated the nitrogen removal performance and the abundances of nitrogen functional genes in the rhizosphere and non-rhizosphere when vertical flow constructed wetland (VFCW) was used to treat brackish eutrophic water. The results demonstrated that both total nitrogen (TN) and ammonia nitrogen (NH4-N) removal efficiencies decreased with the salinity increasing from 0.05% to 1.0%. However, the removal efficiency of nitrate nitrogen (NO3-N) remained more than 93%. It was found by quantitative real-time polymerase chain reaction (qPCR) that abundances of amoA, nosZ, napA, nirK and nirS were greater in the rhizosphere than in the non-rhizosphere at the salinities of 0.05%, 0.5% and 1.0%. As the salinity increased, the abundance of amoA reduced. It indicated that the salinity inhibited the growth of ammonia oxidizing bacteria (AOB) and further hindered the nitrification, which resulted in the deterioration of TN removal performance. The abundances of nosZ, napA, nirK and nirS in the rhizosphere and non-rhizosphere were the highest at 1.0% salinity. The denitrifying bacteria might adapt to the salinity stress, which guaranteed high NO3-N removal efficiency.

The Te[N ii]–Te[O iii] temperature relation in H ii regions and the reliability of strong-line methods

ABSTRACT We use a sample of 154 observations of 124 H ii regions that have measurements of both Te[O iii] and Te[N ii], compiled from the literature, to explore the behaviour of the Te[O iii]–Te[N ii] temperature relation. We confirm that the relation depends on the degree of ionization and present a new set of relations for two different ranges of this parameter. We study the effects introduced by our temperature relations and four other available relations in the calculation of oxygen and nitrogen abundances. We find that our relations improve slightly on the results obtained with the previous ones. We also use a sample of 26 deep, high-resolution spectra to estimate the contribution of blending to the intensity of the temperature-sensitive line [O iii] λ4363, and we derive a relation to correct Te[O iii] for this effect. With our sample of 154 spectra, we analyse the reliability of the R, S, O3N2, N2, ONS, and C strong-line methods by comparing the metallicity obtained with these methods with the one implied by the direct method. We find that the strong-line methods introduce differences that reach ∼0.2 dex or more, and that these differences depend on O/H, N/O, and the degree of ionization.

A chromosome map to unveil stellar populations with different magnesium abundances. The case of ω Centauri

ABSTRACT Historically, photometry has been largely used to identify stellar populations [multiple populations (MPs)] in globular clusters (GCs) by using diagrams that are based on colours and magnitudes that are mostly sensitive to stars with different metallicities or different abundances of helium, carbon, nitrogen, and oxygen. In particular, the pseudo-two-colour diagram called chromosome map (ChM), allowed the identification and the characterization of MPs in about 70 GCs by using appropriate filters of the Hubble Space Telescope (HST) that are sensitive to the stellar content of He, C, N, O, and Fe. We use here high precision HST photometry from F275W, F280N, F343N, F373N, and F814W images of ω Centauri to investigate its MPs. We introduce a new ChM whose abscissa and ordinate are mostly sensitive to stellar populations with different magnesium and nitrogen, respectively, in monometallic GCs. This ChM is effective in disentangling the MPs based on their Mg chemical abundances, allowing us to explore, for the first time, possible relations between the production of these elemental species for large samples of stars in GCs. By comparing the colours of the distinct stellar populations with the colours obtained from appropriate synthetic spectra we provide ‘photometric-like’ estimates of the chemical composition of each population. Our results show that, in addition to first-generation (1G) stars, the metal-poor population of ω Cen hosts four groups of second-generation stars with different [N/Fe], namely, 2GA–D. 2GA stars share nearly the same [Mg/Fe] as the 1G, whereas 2GB, 2GC, and 2GD are Mg depleted by ∼0.15, ∼0.25, and ∼0.45 dex, respectively. We provide evidence that the metal-intermediate populations host stars with depleted [Mg/Fe].

Linking microbial community and biological functions to redox potential during black-odor river sediment remediation.

The black-odor phenomenon in polluted urban rivers is a serious environmental problem that has received increasing attention in the recent years. The low redox potential (less than - 100mV) in the sediment is considered to be the key factor causing the occurrence of black-odor phenomenon. Here, we studied the structure and function of the microbial community during the remediation of urban rivers. Results showed a clear improvement in water quality after undergoing river remediation processes. The on-site treatments showed a succession in the microbial composition and their predicted functions. The primary iron- and sulfur-reducing bacteria (Thiobacillus, Sulfuricurvum, and Sulfursoma) and the related reactions rapidly decreased after the dredging treatment but reappeared after a year. The structure and abundance of nitrogen and methane participants were also affected by river remediation process. These results indicated that although the water quality temporarily improved shortly after a dredging process, a recurrence of the black-odor phenomenon may occur as a result of the rebound in the microbial communities.

Microbial interspecific interaction and nitrogen metabolism pathway for the treatment of municipal wastewater by iron carbon based constructed wetland

In order to explore the pollutant removal performance and interspecific interaction in constructed wetland (CW) with Fe0-C filler, constructed wetland with Fe0-C filler (CW-Fe) and with ceramsite filler (CW-C) were set up. Besides, the nutrients removal and interspecific interaction were analyzed, and the results showed that total nitrogen (TN) removal efficiency of CW-Fe system without carbon source was lower than that in CW-C system though CW-Fe system could convert macro-molecular organic matter into micro-molecular organic matter. However, ammonia nitrogen (NH4+-N) increase was observed in CW-Fe system with better total phosphorus (TP) removal performance. High-throughput sequencing showed that the microbial richness and abundance of Bacteroides, Firmicutes, Chlorofeli and Actinobacteria in the CW with Fe0-C filler was significantly higher than with ceramsite filler. The interaction between two CWs was significantly different, and the functional enzymes abundance of nitrate nitrogen (NO3−-N) to NH4+-N transformation in CW-Fe system significantly increased.

Land-use type, and land management and disturbance affect soil δ15N: a review

We compared the patterns of natural abundance of nitrogen (N) isotope ratio (δ15N) of total soil N among cropland, forest, and grassland soils, with special interests in the effects of farming system on cropland and grassland, and climate zone on forest soils, as well as the general effect of land-use change and site disturbance. We analyzed data on δ15N of terrestrial N sources (n = 532), cropland (n = 168), forest (n = 227 for organic and 428 for mineral soil layers), and grassland soils (n = 624). Forest soils had the lowest δ15N (– 1.0 ± 0.2‰ and + 3.1 ± 0.2‰ for mineral and organic soil layers, respectively), reflecting the influence of the 15N-depleted source N and the more closed nature of the N cycle. Tropical forest soil had higher δ15N than other climate zones, reflecting the influence of the high N availability and loss in tropical forests. The low δ15N in subtropical forest soils likely reflected the influence of the high rate of deposition of 15N-depleted N. The δ15N of cropland (+ 5.0 ± 0.2‰) and grassland (+ 6.2 ± 0.1‰) soils was greater with manure than with synthetic fertilizer applications. Soil δ15N was also affected by land-use change and was often increased (followed by progressive decreases) by site disturbance. Land-use type and land management effects on soil δ15N reflect changes in both the N sources and loss, while land disturbance effects are primarily associated with the degree of N loss. We also conclude that subtropical forest soil δ15N is affected by the high rate of atmospheric N deposition.

Has agricultural intensification impacted maize root traits and rhizosphere interactions related to organic N acquisition?

Plant–microbe interactions in the rhizosphere influence rates of organic matter mineralization and nutrient cycling that are critical to sustainable agricultural productivity. Agricultural intensification, particularly the introduction of synthetic fertilizer in the USA, altered the abundance and dominant forms of nitrogen (N), a critical plant nutrient, potentially imposing selection pressure on plant traits and plant–microbe interactions regulating N cycling and acquisition. We hypothesized that maize adaptation to synthetic N fertilization altered root functional traits and rhizosphere microbial nutrient cycling, reducing maize ability to acquire N from organic sources. Six maize genotypes released pre-fertilizer (1936, 1939, 1942) or post-fertilizer (1984, 1994, 2015) were grown in rhizoboxes containing patches of 15N-labelled clover/vetch residue. Multivariate approaches did not identify architectural traits that strongly and consistently predicted rhizosphere processes, though metrics of root morphological plasticity were linked to carbon- and N-cycling enzyme activities. Root traits, potential activities of extracellular enzymes (BG, LAP, NAG, urease), abundances of N-cycling genes (amoA, narG, nirK, nirS, nosZ) and uptake of organic N did not differ between eras of release despite substantial variation among genotypes and replicates. Thus, agricultural intensification does not appear to have impaired N cycling and acquisition from organic sources by modern maize and its rhizobiome. Improved mechanistic understanding of rhizosphere processes and their response to selective pressures will contribute greatly to rhizosphere engineering for sustainable agriculture.

Characteristics of molecular nitrogen generation from overmature black shales in South China: Preliminary implications from pyrolysis experiments

High content of molecular nitrogen (N2) is one of the natural gas exploration risks in petroliferous basins where black shales act as source rocks of either hydrocarbon gas or molecular nitrogen. In this study, two overmature and one low-maturity shale samples and their kerogens were investigated to determine the generation characteristics of molecular nitrogen as well as methane and the differences in the release processes of inorganic nitrogen fixed in ammonium-bearing minerals and organic nitrogen bound in kerogen. The results illustrate that with increasing pyrolysis temperature, the yield of methane first increases and then decreases with an inflection temperature of 650 °C (EqVRo = 3.4%), whereas the yield of molecular nitrogen shows a continuous increase throughout the pyrolysis experiment. The molecular nitrogen during the stage of methane generation (i.e., EqVRo < 3.4%) is more preferentially derived from the inorganic nitrogen in ammonium-bearing minerals, whereas the significant generation of molecular nitrogen from organic nitrogen in kerogen commences only after the methane generation potential is exhausted (EqVRo > 3.4%). The results also reveal that at the experimental maxima of thermal maturity (EqVRo = 4.9%), the generation potential of inorganic molecular nitrogen (mg/g Ninorg) is much lower than that of organic molecular nitrogen (mg/g Norg), indicating that in our experiments the organic nitrogen in kerogen is more easily to be converted into molecular nitrogen than the inorganic nitrogen in ammonium-bearing minerals. All these results indicate that molecular nitrogen content in shale gas may change dramatically during thermal evolution, and source rocks with exceptionally high maturity and high abundance of organic nitrogen likely lead to a high molecular nitrogen risk, particularly in regions of poor preservation conditions of shale gas, which may be the main reasons for the high molecular nitrogen content in the Lower Cambrian shale gas in South China.

Chemical abundances in active galaxies

ABSTRACT The Sloan Digital Sky Survey (SDSS) has proved to be a powerful resource for understanding the physical properties and chemical composition of star-forming galaxies in the local Universe. The SDSS population of active galactic nuclei (AGNs) remains as of yet less explored in this capacity. To extend the rigorous study of H ii regions in the SDSS to AGNs, we adapt methods for computing direct-method chemical abundances for application to the narrow-line regions (NLR) of AGNs. By accounting for triply ionized oxygen, we are able to more completely estimate the total oxygen abundance. We find a strong correlation between electron temperature and oxygen abundance due to collisional cooling by metals. Furthermore, we find that nitrogen and oxygen abundances in AGNs are strongly correlated. From the metal–temperature relation and the coupling of nitrogen and oxygen abundances, we develop a new, empirically and physically motivated method for determining chemical abundances from the strong emission lines commonly employed in flux-ratio diagnostic diagrams (BPT diagrams). Our approach, which for AGNs reduces to a single equation based on the BPT line ratios, consistently recovers direct-method abundances over a 1.5 dex range in oxygen abundance with an rms uncertainty of 0.18 dex. We have determined metallicities for thousands of AGNs in the SDSS, and in the process have discovered an ionization-related discriminator for Seyfert and LINER galaxies.

Carbon-loud SDSS BOSS type II quasars at z &amp;gt; 2: high-density gas or secondary production of carbon?

ABSTRACT We study the ultraviolet (UV) emission-line ratios of a sample of 145 type II quasars (QSO2s) from Sloan Digital Sky Survey iii Baryon Oscillation Spectroscopic Survey, and compare against a grid of active galactic nucleus (AGN) photoionization models with a range in gas density, gas chemical abundances, and ionization parameter. Most of the quasars are ‘carbon-loud’, with C iv/He ii ratios that are unusually high for the narrow-line region, implying higher than expected gas density (&amp;gt;106 cm−3) and/or significantly supersolar-relative carbon abundance. We also find that solar or supersolar nitrogen abundance and metallicity are required in the majority of our sample, with potentially significant variation between objects. Compared to radio galaxies at similar redshifts (HzRGs; z &amp;gt; 2), the QSO2s are offset to higher N v/He ii, C iv/He ii, and C iii]/He ii, suggesting systematically higher gas density and/or systematically higher C and N abundances. We find no evidence for a systematic difference in the N/C abundance ratio between the two types of objects. Scatter in the N iv]/C iv ratio implies a significant scatter in the N/C abundance ratio among the QSO2s and HzRGs, consistent with differences in the chemical enrichment histories between objects. Interestingly, we find that adopting secondary behaviour for both N and C alleviates the long-standing ‘N iv] problem’. A subset of the QSO2s and HzRGs also appear to be ‘silicon-loud’, with Si iii] relative fluxes suggesting Si/C and Si/O are an order of magnitude above their solar values. Finally, we propose new UV-line criteria to select genuine QSO2s with low-density narrow-line regions.

Mineralogical composition and C/N contents in soil and water among betel vineyards of coastal Odisha, India

The Piper betle L. leaves and their significance were described in various ayurvedic studies of India and China for its diverse use in cultural practices and treatment of various health disorders. The leaves of P. betle were used as post-meal mouth freshener in India for centuries. However, it offers economic benefits to farmers of Coastal India at large. Betel leaves cultivated agricultural soils play a significant role for their mineralogical composition. So, this present study aimed to find out the soil physicochemical characteristics and C/N contents of Betel vineyards of coastal Odisha. The soil and water samples were collected from local varieties of P. betle L. cultivated vineyards of Balasore, Ganjam, and Puri districts of Odisha and investigated their mineralogical composition. The soil mineralogy plays crucial role to understand the soil–plant relations. Coastal soil samples also contain the most prized mineral aggregations from economical perspectives. The mineralogical composition involves chemical composition, essential elemental composition, and surface morphology. The mineralogical and elemental composition of soil samples were carried out by using various techniques like Fourier transform infrared spectroscopy, X-ray diffraction (XRD) and energy-dispersive X-ray fluorescence, scanning electron microscopy attached with energy-dispersive X-ray system. CHNS analyzer for quantification of hydrogen, nitrogen, carbon, and sulfur content. H2O2 (30%)-treated soil is employed to eliminate the organic carbon from mass soil samples. The scanning electron microscopy analysis revealed the presence of heterogeneity shape and size of surface soils of both treated and untreated soils. For estimation of total organic carbon (TOC), inorganic carbon, total nitrogen, and total carbon, water samples were analyzed through TOC analyzer. Percentage variation arises in GAN and PUR sites soil due to more assumption of organic matter from clay soils in comparison with sandy soils of BAL. The spectra of FTIR point out Kaolinite and Quartz as the key components and others are minor components. The common minerals like quartz, hematite, kaolinite, montmorillonite, calcite, organic matter and illite in diverse compositions are recognized. Further, the presence of these above minerals was confirmed by the XRD analysis. Morphological analysis of kaolinite indicated euhedral, hexagonal, and pseudo-hexagonal-shaped plates. The mineralogical data revealed the relative abundance of phosphorus and nitrogen was less in all soils. Depletion of P and N may be resulted due to introduction of fresh plowed soil from grazed pastoral land. The present research uncovers that soils requires adequate input of additional compost, manures, and fertilizers for maximal vegetative growth and economic yield as well. As P. betle species is very precious medicinal plant, and this research suggested not to use contaminated water for betel cultivation. Our results also helpful for the improvement in soil management in the vineyards to determining the mineral nutrients that affect plant growth and development.