Carbon Abundances Research Articles

Study of the Biogas Ebullition from Lacustrine Carbonate Enriched and Black Silt Bottom Sediments

The greenhouse effect, which is also promoted by naturally occurring biogas ebullition fluxes (released via bubbles), generated by the decomposition of organic matter in carbonate-enriched and black silt sediments, has been analyzed. This study is based on results obtained using passive gas collectors at different parts of eutrophic Lake Juodis, located in a temperate climate zone in the vicinity of Vilnius (Lithuania). The measured annual biogas (containing about 60% of biomethane) ebullition fluxes from carbonate-enriched sediments and black silt sediments were 16.9–23.0 L/(m2∙y) and 38.5–43.2 L/(m2∙y), respectively. This indicates that the gas fluxes from carbonate sediments were almost twice as low as those from black silt sediments. Oxygen, produced by the photosynthetic activity of green algae in the near-surface water and sediments, helps to retain carbonates in the sediments by preventing their dissolution. In turn, the calcite coating on sediment particles partially preserves organic matter from decomposition, reducing the effective thickness of the sediment layer generating biogas. The characteristic vertical distribution profile of 137Cs activity, with sharp peaks in sediments, suggests that generated biogas bubbles move to the surface of the sediments forming vertical channels by pushing sediment particles asides without noticeably mixing them vertically. This examination showed that factors such as abundance of carbonates in the sediments may result in a significant reduction in biogas generation and emissions from the lake sediments.

Eridanus III and DELVE 1: Carbon-rich Primordial Star Clusters or the Smallest Dwarf Galaxies?* *This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

We present spectroscopy of the ultra-faint Milky Way satellites Eridanus III (Eri III) and DELVE 1. We identify eight member stars in each satellite and place nonconstraining upper limits on their velocity and metallicity dispersions. The brightest star in each object is very metal poor, at [Fe/H] = −3.1 for Eri III and [Fe/H] = −2.8 for DELVE 1. Both of these stars exhibit large overabundances of carbon and very low abundances of the neutron-capture elements Ba and Sr, and we classify them as CEMP-no stars. Because their metallicities are well below those of the Milky Way globular cluster population, and because no CEMP-no stars have been identified in globular clusters, these chemical abundances could suggest that Eri III and DELVE 1 are dwarf galaxies. On the other hand, the two systems have half-light radii of 8 pc and 6 pc, respectively, which are more compact than any known ultra-faint dwarfs. We conclude that Eri III and DELVE 1 are either the smallest dwarf galaxies yet discovered, or they are representatives of a new class of star clusters that underwent chemical evolution distinct from that of ordinary globular clusters. In the latter scenario, such objects are likely the most primordial star clusters surviving today. These possibilities can be distinguished by future measurements of carbon and/or iron abundances for larger samples of stars or improved stellar kinematics for the two systems.

Puffy Venuses: The Mass–Radius Impact of Carbon-rich Atmospheres on Lava Worlds

The recent advancements in exoplanet observations enable the potential detection of exo-Venuses, rocky planets with carbon-rich atmospheres. How extended these atmospheres can be, given high carbon abundances, has not been studied. To answer this, we present a model for a theoretical class of exoplanets—puffy Venuses—characterized by thick, carbon-dominated atmospheres in equilibrium with global magma oceans (MOs). Our model accounts for carbon and hydrogen partition between the atmosphere and the MO, as well as the C–H–O equilibrium chemistry throughout a semi-gray, radiative-convective atmosphere. We find that radius inflation by puffy Venus atmospheres is significant on small and irradiated planets: carbon content of 1200 ppm (or that of ordinary chondrites) can generate an atmosphere of ∼0.16–0.3 R ⊕ for an Earth-mass planet with equilibrium temperatures of 1500–2000 K. We identify TOI-561 b as an especially promising puffy Venus candidate, whose underdensity could be attributed to a thick C-rich atmosphere. We also advocate for a puffy Venus interpretation of 55 Cancri e, where a recent JWST observation indicates the presence of a CO/CO2 atmosphere. Puffy Venuses may thus constitute a testable alternative interpretation for the interior structure of underdense low-mass exoplanets.

Arbuscular mycorrhizal fungi regulation of soil carbon fractions in coal mining restoration: Dominance of glomalin-related soil proteins revealed by stable carbon isotopes (δ13C)

Arbuscular mycorrhizal fungi (AMF) play a pivotal role in soil carbon cycling by orchestrating the recruitment of microbial communities and establishing hyphal networks. Understanding whether these attributes of AMF are instrumental in restoring soil carbon pools in areas disrupted by coal mining is crucial for forecasting soil organic carbon (SOC) dynamics in post-disturbance restoration sites. This study conducted a year-long, in-situ leaf decomposition experiment (comprising three shrubs: Amorpha fruticose, Caragana, and Sea buckthorn; two treatments: inoculated with AMF and without AMF inoculation) at the mycorrhizal restoration demonstration base in Inner Mongolia's mining area. Utilizing stable isotope technology, we investigated the mycorrhizal regulatory effects on aggregate carbon dynamics during the leaf decomposition process. Our findings showed that the presence of AMF hyphae accelerated carbon transformation within aggregates, resulting in augmented content of mineral-bound carbon (+6.1 %) and δ13C abundance (7.1 %) within microaggregates in sea buckthorn plots. Analysis employing random forest and partial least squares regression models corroborated that the regulation of mycorrhizal dynamics on aggregate carbon composition after fresh leaf input was indirectly influenced by GRSP rather than directly by AMF hyphae. In summary, our findings elucidate the evolving patterns of aggregate carbon dynamics following AMF inoculation in coal mining reclamation sites under field conditions. This underscored the efficacy of planting sea buckthorn and inoculating AMF during the vegetation restoration process of open-pit mine reclamation land in Inner Mongolia.

Soil biological health assessment based on nematode communities under maize and peanut intercropping

BackgroundCereal/legume intercropping can enhance crop productivity and improve soil health in dryland farming. However, little is known about soil biological health under maize/peanut intercropping. The aim of this study was to assess soil biological health based on nematode communities in a maize/peanut intercropping system.MethodsWe conducted a field experiment with different planting patterns, including monoculture maize (M), monoculture peanut (P), and maize intercropped with peanut (IM, intercropped maize; IP, intercropped peanut) to determine the influence on soil biological health. We measured soil physicochemical properties and nematode communities, and employed exploratory factor analysis combined with cumulative normal distribution curve scoring to identify potential soil biological health traits.ResultsThe intercropped maize gave the highest plant parasitic nematode abundance, trophic diversity index, evenness index, and structure index. The monoculture peanut gave the highest enrichment index and least plant parasitic nematode abundance, trophic diversity index, Shannon diversity index, evenness index, structure index, and channel index. We identified four soil biological health traits, including basic nutrients and biodiversity, food web complexity, slow energy channel, and fast energy channel, mainly represented by soil ammonium nitrogen and Shannon diversity index, structural index and omnivore-predator nematode abundance, fungivorous nematode abundance and plant parasitic nematode abundance, microbial biomass carbon and bacterivorous nematode abundance, respectively. The intercropping systems improved the comprehensive score of soil biological health, especially maize intercropping soil. Intercropping maize and intercropping peanut significantly improved oil biological health traits representing the food web complexity compared with the corresponding monoculture soils.ConclusionsOur results indicate that soil nematode and physicochemical indicators reflect different soil biological health traits. Among those traits, the improvement of basic nutrients and biodiversity and the complexity of the food web were the main reasons for improving soil biological health through the intercropping system.

S-process nucleosynthesis in chemically peculiar binaries

Context. Around half of the heavy elements in the Universe are formed through the slow neutron capture (s-) process, which takes place in thermally pulsing asymptotic giant branch (AGB) stars with masses of 1 − 6 M⊙. The nucleosynthetic imprint of the s-process can be studied by observing the material on the surface of binary barium (Ba), carbon (C), CH, and carbon-enhanced metal-poor (CEMP) stars. Aims. We study the s-process by observing the luminous components of binary systems polluted by a previous AGB companion. Our radial velocity (RV) monitoring program establishes an ongoing collection of binary stars exhibiting enrichment in s-process material for the study of elemental abundances, the production of s-process material, and binary mass transfer. Methods. From high-resolution optical spectra, we measured RVs for 350 stars and derived stellar parameters for approximately 150 stars using ATHOS. For a subsample of 24 chemically interesting stars, we refined our atmospheric parameters using ionization and excitation balance with the Xiru program. We used the MOOG code to compute one-dimensional local thermodynamic equilibrium (1D-LTE) abundances of carbon, magnesium, s-process elements (Sr, Y, Zr, Mo, Ba, La, Ce, Nd, Pb), and Eu to investigate neutron capture events and stellar chemical composition. We estimated dynamical stellar masses via orbital optimization using Markov chain Monte Carlo techniques in the ELC program, and we compared our results with low-mass AGB models in the FUll-Network Repository of Updated Isotopic Tables & Yields (FRUITY) database. Results. In our abundance subsample, we find enhancements in s-process material in spectroscopic binaries, a signature of AGB mass transfer. We add the element Mo to the abundance patterns, and for 12 stars we add Pb detections or upper limits, as these are not known in the literature. Computed abundances are in general agreement with the literature. Comparing our abundances to dilution-modified FRUITY yields, we find correlations in s-process enrichment and AGB mass, which are supported by dynamical modeling from RVs. Conclusions. From our high-resolution observations, we expand heavy element abundance patterns and highlight binarity in our chemically interesting systems. We find trends in s-process element enhancement from AGB stars, and agreement between theoretical and dynamically modeled masses. We investigate evolutionary stages for a small subset of our stars.

SDSS J102915.14+172927.9: Revisiting the chemical pattern

Context. The small- to intermediate-mass (M < 0.8 M⊙), most metal-poor stars that formed in the infancy of the Universe are still shining today in the sky. They are very rare, but their discovery and investigation brings new knowledge on the formation of the first stellar generations. Aims. SDSS J102915.14+172927.9 is one of the most metal-poor star known to date. Since no carbon can be detected in its spectrum, a careful upper limit is important, both to classify this star and to distinguish it from the carbon-enhanced stars that represent the majority at these metallicities. Methods. We undertook a new observational campaign to acquire high-resolution UVES spectra. The new spectra were combined with archival spectra in order to increase the signal-to-noise ratio. From the combined spectrum, we derived abundances for seven elements (Mg, Si, Ca, Ti, Fe, Ni, and a tentative Li) and five significant upper limits (C, Na, Al, Sr, and Ba). Results. The star has a carbon abundance A(C) < 4.68 and therefore is not enhanced in carbon, at variance with the majority of the stars at this Fe regime, which typically show A(C) > 6.0. A feature compatible with the Li doublet at 670.7 nm is tentatively detected. Conclusions. The upper limit on carbon implies Z < 1.915 × 10−6, more than 20 times lower than the most iron-poor star known. Therefore, the gas cloud out of which the star was formed did not cool via atomic lines but probably through dust. Fragmentation of the primordial cloud is another possibility for the formation of a star with a metallicity this low.

Chemical Evolution of R-process Elements in Stars (CERES)

Context. Carbon, nitrogen, and oxygen are the most abundant elements throughout the universe, after hydrogen and helium. Studying these elements in low-metallicity stars can provide crucial information on the chemical composition in the early Galaxy and possible internal mixing processes that can alter the surface composition of the stars. Aims. This work aims to investigate the chemical abundance patterns for CNO elements and Li in a homogeneously analyzed sample of 52 metal-poor halo giant stars. From these results, we have been able to determine whether internal mixing processes have taken place in these stars. Methods. We used high-resolution spectra with a high signal-to-noise ratio (S/N) to carry out a spectral synthesis to derive detailed C, N, O, and Li abundances for a sample of stars with metallicities in the range of −3.58 ≤ [Fe/H] ≤ −1.79 dex. Our study was based on the assumption of one-dimensional (1D) local thermodynamic equilibrium (LTE) atmospheres. Results. Based on carbon and nitrogen abundances, we investigated the deep mixing taking place within stars along the red giant branch (RGB). The individual abundances of carbon decrease towards the upper RGB while nitrogen shows an increasing trend, indicating that carbon has been converted into nitrogen. No signatures of ON-cycle processed material were found for the stars in our sample. We computed a set of galactic chemical evolution (GCE) models, implementing different sets of massive star yields, both with and without including the effects of stellar rotation on nucleosynthesis. We confirm that stellar rotation is necessary to explain the highest [N/Fe] and [N/O] ratios observed in unmixed halo stars. The predicted level of N enhancement varies sensibly in dependence of the specific set of yields that are adopted. For stars with stellar parameters similar to those of our sample, heavy elements such as Sr, Y, and Zr appear to have unchanged abundances despite the stellar evolution mixing processes. Conclusions. The unmixed RGB stars provide very useful constraints on chemical evolution models of the Galaxy. As they are more luminous than unevolved (main sequence and turnoff) stars, they also allow for stars to be probed at greater distances. The stellar CN-cycle clearly changes the atmospheric abundances of the lighter elements, but no changes were detected with respect to the heavy elements.

Mechanisms of secondary carbonate precipitation on felsic, intermediate and mafic igneous rocks: a case study for NW Scotland

Silicate weathering is a natural regulator of atmospheric carbon dioxide (CO 2 ), where the majority of carbonate is stored in the oceans. In some instances, carbonates may form via bedrock weathering in terrestrial landscapes, but this is commonly noted in ultramafic rock owing to its desirable mineralogy. In NW Scotland, carbonate minerals surround felsic, intermediate and mafic igneous bedrock. Their abundance suggests that these rocks could potentially be targeted for carbonation, given the absence of other known cation sources nearby. We present geochemical and mineralogical data for bedrock samples and mineralogy and stable carbon and oxygen isotope data for the carbonate samples. Whole-rock geochemistry demonstrates that major abundances of CaO and MgO are present in the bedrock samples and would be sourced from plagioclase and pyroxene, which are target minerals for CO 2 mineralization. The stable carbon and oxygen isotope data demonstrate that there are probably mixed carbon sources (atmospheric and organic), and other environmental factors including temperature, CO 2 degassing or evaporation and nearby waters influence the isotopic composition. Results suggest that rocks traditionally overlooked in CO 2 mineralization studies have the potential to serve as a feedstock for carbonation, given the abundance of secondary carbonates found in NW Scotland.

GA-NIFS: an extremely nitrogen-loud and chemically stratified galaxy at z ~ 5.55

ABSTRACT We report the chemical abundance pattern of GS_3073, a galaxy hosting an overmassive active black hole at $z=5.55$, by leveraging observations from JWST/NIRSpec and Very Large Telescope/VIsible Multi-Object Spectrograph. Based on the rest-frame ultraviolet (UV) emission lines, which trace high-density ($\sim 10^5~{\rm cm^{-3}}$) and highly ionized gas, we derive $\rm \log (N/O) = 0.42^{+0.13}_{-0.10}$. At an estimated metallicity of $0.2~Z_{\odot }$, this is the most extreme nitrogen-rich object found by JWST thus far. In comparison, the relative carbon abundance derived is $\rm \log (C/O) = -0.38^{+0.13}_{-0.11}$, which is not significantly higher than those in local galaxies and stars with similar metallicities. We also found potential detection of [Fe vii]$\lambda 6087$ and [Fe xiv]$\lambda 5303$, both blended with [Ca v]. We inferred a range of Fe abundances compatible with those in local stars and galaxies. Overall, the chemical abundance pattern of GS_3073 is compatible with enrichment by supermassive stars with $M_* \gtrsim 1000~M_\odot$, asymptotic giant branch stars, or Wolf–Rayet stars. Interestingly, when using optical emission lines that trace lower density ($\sim 10^3~{\rm cm}^{-3}$) and lower ionization gas, we found a sub-solar N/O ratio, consistent with local galaxies at the same metallicity. We interpret the difference in N/O derived from UV lines and optical lines as evidence for a stratified system, where the inner and denser region is both more chemically enriched and more ionized. Our results suggest that nitrogen loudness in high-z galaxies might be confined to the central, dense, and highly ionized regions of the galaxies, while the bulk of the galaxies evolves more normally.

Increasing tree phylogenetic diversity stimulates microbial functional potential in a subtropical forest

Abstract Soil microbial functions are closely related to ecosystem productivity, carbon sequestration and their responses to global change. Tree phylogenetic diversity has been found to impact microbial community composition, diversity, and functions, but how it modulates the linkage between microbial community facets and functions remains unclear. Here, 45 plots covering a natural gradient of tree phylogenetic diversity (TPD) were selected in a subtropical forest of southwest China to explore how increasing TPD impacts soil microbial community facets and microbial functional potential. The microbial functional potential was evaluated based on the abundances of carbon, nitrogen, and phosphorus cycling-related functional genes. Soil fungal alpha diversity increased significantly, but bacterial alpha diversity did not change as TPD increased. Both soil microbial network complexity and stability improved significantly with increasing TPD. Ultimately, increasing TPD promoted soil microbial functional potential by stimulating soil carbon and nitrogen availability, microbial keystone diversity, and network stability collectively. These findings emphasize the critical roles of keystone taxa and network stability as microbial factors in stimulating soil microbial function in response to increasing TPD. Therefore, it is strongly recommended to increase TPD in order to stimulate soil microbial functions and other ecosystem functions when implementing afforestation or ecological restoration projects.

How biochar curbs the negative impacts of plastic mulching on soil enzymes and microorganisms while elevating crop yields in ridge-furrow systems

Ridge-furrow tillage is an important tillage and yield enhancement method used in dry farming areas; however, the spatial characteristics of the soil microenvironment under ridge-furrow tillage and the response of crop yields to mulching and biochar addition are not known. In this study, we conducted a three-year field experiment in which mulch and biochar, alone or combined, were introduced into ridge-furrow tillage system to explore their interactive effects on soil enzyme activities, bacterial communities, functional genes, and crop yields. The findings reveal significant spatial differences in soil physicochemical composition, enzyme activity, microbial communities, and functional genes under ridge-furrow tillage, which are further exacerbated by the addition of mulching and biochar. Under the premise of ridge-furrow tillage, both mulching and biochar addition reduce the α diversity of bacterial communities. Mulching simplifies the bacterial network, while biochar addition has the opposite effect. Mulching and biochar addition increase the relative abundance of carbon, nitrogen, and phosphorus functional genes and accelerate nutrient cycling, especially on the ridges. Mulching significantly improves crop yield but is detrimental to alkaline phosphatase activity and the abundance of the gene function. The addition of biochar mitigates the harm of mulching and further increases alfalfa yield. These findings not only provide scientific support for optimizing ridge-furrow tillage but also deepen our comprehensive understanding of the soil biochemical environment after the addition of mulching and biochar, further revealing their positive effects on yield formation.

Variation of soil organic carbon stability in restored mountain marsh wetlands

The replacement of farmland by native hygro-plants is increasingly common globally within the context of wetland ecosystem restoration. Understanding the long-term effects of this replacement on the abundance and persistence of soil organic carbon (SOC) in mountain marshes is important for soil carbon management. Here, the restored plateau mountain marshes of Duliu River Wetland Provincial Nature Reserve, China was selected. The properties, soil moisture content (SMC), pH, texture, free-form iron oxides (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:{\ ext{F}\ ext{e}}_{\ ext{d}}$$\\end{document}), amorphous iron oxides (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:{\ ext{F}\ ext{e}}_{\ ext{o}}$$\\end{document}), mineral-associated organic carbon (MAOC), and iron-bound organic carbon (Fe-OC) were analyzed in topsoil samples (0 ~ 20 cm) during the restoration of rice paddies to Sphagnum palustre L. wetlands for 0, 2, 10, and 20 years. Natural Sphagnum wetlands were also used as the control. We found that marsh restoration increased SMC, \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:{\ ext{F}\ ext{e}}_{\ ext{o}}$$\\end{document}, \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:{\ ext{F}\ ext{e}}_{\ ext{d}}$$\\end{document}, \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:{\ ext{F}\ ext{e}}_{\ ext{o}}$$\\end{document}/\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:{\ ext{F}\ ext{e}}_{\ ext{d}}$$\\end{document}, SOC, MAOC, Fe-OC, Fe-OC/SOC, but decreased the MAOC/SOC ratio. MAOC/SOC ratio of marshes were expectedly lower than the proportion of labile SOC in total SOC during the restoration period. SMC, SOC, and MAOC were higher in the natural Sphagnum wetlands than in other habitats. Both SOC and Fe-OC/SOC were positively correlated with SMC, \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:{\ ext{F}\ ext{e}}_{\ ext{o}}$$\\end{document}, \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:{\ ext{F}\ ext{e}}_{\ ext{d}}$$\\end{document}, \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:{\ ext{F}\ ext{e}}_{\ ext{o}}$$\\end{document}/\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:{\ ext{F}\ ext{e}}_{\ ext{d}}$$\\end{document}, and Fe-OC, but negatively correlated with soil pH. 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These results emphasized the significance of reconverting rice paddies to marsh wetlands for increasing the sequestration of labile SOC and Fe-OC. Further studies are required to identify and quantify the organo-mineral stabilization mechanisms of SOC at the different SOC fractionations throughout the restoration period.

Volatile composition of the HD 169142 disk and its embedded planet

Abstract The composition of a planet’s atmosphere is intricately linked to the chemical makeup of the protoplanetary disk in which it formed. Determining the elemental abundances from key volatiles within disks is therefore essential for establishing connections between the composition of disks and planets. The disk around the Herbig Ae star HD 169142 is a compelling target for such a study due to its molecule-rich nature and the presence of a newly-forming planet between two prominent dust rings. In this work, we probe the chemistry of the HD 169142 disk at small spatial scales, drawing links between the composition of the disk and the planet-accreted gas. Using thermochemical models and archival data, we constrain the elemental abundances of volatile carbon, oxygen, and sulfur. Carbon and oxygen are only moderately depleted from the gas phase relative to their interstellar abundances, with the inner ~60 au appearing enriched in volatile oxygen. The C/O ratio is approximately solar within the inner disk (~0.5) and rises above this in the outer disk (>0.5), as expected across the H2O snowline. The gas-phase sulfur abundance is depleted by a factor of ~1000, consistent with a number of other protoplanetary disks. Interestingly, the observed SiS emission near the HD 169142 b protoplanet vastly exceeds chemical model predictions, supporting previous hypotheses suggesting its origin in shocked gas or a localised outflow. We contextualise our findings in terms of the potential atmospheric composition of the embedded planet, and highlight the utility of sulfur-bearing molecules as probes of protoplanetary disk chemistry.

Chemical composition of planetary hosts: C, N, and α-element abundances

Accurate atmospheric parameters and chemical composition of planet hosts play a major role in characterising exoplanets and understanding their formation and evolution. Our objective is to uniformly determine atmospheric parameters and chemical abundances of carbon (C), nitrogen (N), oxygen(O), and the alpha -elements, magnesium (Mg) and silicon (Si), along with C/O, N/O and Mg/Si abundance ratios for planet-hosting stars. In this analysis, we aim to investigate the potential links between stellar chemistry and the presence of planets. e tai Observatory telescope. The determination of stellar parameters was based on a standard analysis using equivalent widths and one-dimensional, plane-parallel model atmospheres calculated under the assumption of local thermodynamical equilibrium. The differential synthetic spectrum method was used to uniformly determine the carbon C(C2), nitrogen N(CN), oxygen O I magnesium Mg I, and silicon Si I elemental abundances as well as the C/O, N/O, and Mg/Si ratios. We analysed elemental abundances and ratios in dwarf and giant stars, finding that C/Fe O/Fe and Mg/Fe are lower in metal-rich dwarf hosts; whereas N/Fe is close to the Solar ratio. Giants show smaller scatter in C/Fe and O/Fe and lower than the Solar average C/Fe and C/O ratios. The (C+N+O) abundances increase with Fe/H in giant stars, with a minimal scatter. We also noted an overabundance of Mg and Si in planet-hosting stars, particularly at lower metallicities, and a lower Mg/Si ratio in stars with planets. In giants hosting high-mass planets, nitrogen shows a moderate positive relationship with planet mass. C/O and N/O ratios show moderate negative and positive slopes in giant stars, respectively. The Mg/Si ratio shows a negative correlation with planet mass across the entire stellar sample.

The Pristine Inner Galaxy Survey (PIGS)

We aim to constrain the chemo-dynamical properties of the Sagittarius (Sgr) dwarf galaxy using carbon abundances. At low metal- licities in particular, these properties reveal the early chemical evolution of a system, tracing the contributing supernovae (SNe) and how much of their ejecta eventually made it into the next stellar generation. Our sample from the Pristine Inner Galaxy Survey (PIGS) includes ~350 metal-poor ([Fe/H] < −1.5) stars in the main body of Sgr with good quality spectroscopic observations. Our metal-poor Sgr population has a larger velocity dispersion than metal-rich Sgr from the literature, which could be explained by outside-in star formation, extreme Galactic tidal perturbations, and/or the presence of a metal-rich disc and bar + metal-poor halo. The average carbon abundance [C/Fe] in Sgr is similar to that of other classical dwarf galaxies (DGs) and consistently lower than in the Milky Way by ~0.2–0.3 dex at low metallicities. The interstellar medium in DGs, including Sgr, may have retained yields from more energetic Population III and II supernovae (SNe), thereby reducing the average [C/Fe]. Additionally, SNe Ia producing more Fe than C would start to contribute at lower metallicity in DGs/Sgr than in the Galaxy. The presence of a [C/Fe] gradient for Sgr stars with [Fe/H] ≳ −2.0 (~6.8 × 10−4 dex arcmin−1) suggests that SNe la contributed to the system at those metallicities, especially in its inner regions. There is a low frequency of carbon-enhanced metal-poor (CEMP) stars in our Sgr sample. At higher metallicities and carbon abundances (i.e. mostly CEMPs), this may be due to photometric selection effects, but those are less likely to affect non-CEMP stars. Given the lower average [C/Fe] in DGs, we propose using the same CEMP definition ([C/Fe] > +0.7) as that applied to the Galaxy at large ends up underpredicting the number of CEMP stars in DGs. Burthermore, for Sgr, a cut at [C/Fe] ∽ +0.35 may be more appropriate, which brings the frequency of CEMP stars in agreement with that of the whole Galaxy.

The Wanderer: Charting WASP-77A b’s Formation and Migration Using a System-wide Inventory of Carbon and Oxygen Abundances

The elemental and isotopic abundances of volatiles like carbon, oxygen, and nitrogen may trace a planet’s formation location relative to H2O, CO2, CO, NH3, and N2 “snowlines,” or the distance from the star at which these volatile elements sublimate. By comparing the C/O and 12C/13C ratios measured in giant exoplanet atmospheres to complementary measurements of their host stars, we can determine whether the planet inherited stellar abundances from formation inside the volatile snowlines, or nonstellar C/O and 13C enrichment characteristic of formation beyond the snowlines. To date, there are still only a handful of exoplanet systems where we can make a direct comparison of elemental and isotopic CNO abundances between an exoplanet and its host star. Here, we present a 12C/13C abundance analysis for host star WASP-77A (whose hot Jupiter’s 12C/13C abundance was recently measured). We use MARCS stellar atmosphere models and the radiative transfer code TurboSpectrum to generate synthetic stellar spectra for isotopic abundance calculations. We find a 12C/13C ratio of 51 ± 6 for WASP-77A, which is subsolar (∼91) but may still indicate 13C enrichment in its companion planet WASP-77A b (12C/13C = 26 ± 16, previously reported). Together with the inventory of carbon and oxygen abundances in both the host and companion planet, these chemical constraints point to WASP-77A b’s formation beyond the H2O and CO2 snowlines and provide chemical evidence for the planet’s migration to its current location ∼0.024 au from its host star.

LITERATUR STUDI MENGENAI ADSORBEN LIMBAH CANGKANG HEWAN LAUT DALAM BERBAGAI KEILMUAN

The utilization of marine animal waste as a base material for adsorbents has become an increasingly popular research topic across various scientific fields, including chemistry, environmental science, and materials science. Waste from marine animals, such as crab shells, oyster shell, seashell, and shrimp shell, possesses high potential to be processed into adsorbents due to their abundant calcium carbonate, chitosan, and protein content. The use of this waste as adsorbents not only provides a solution to environmental issues related to the accumulation of organic waste but also offers cheaper and eco-friendly alternative for water treatment, air purification, and contaminated soil remediation. Research has shown that marine animal waste-based adsorbents are effective in removing various pollutants, including heavy metals, textile dyes, and hazardous organic compounds. With specific modification techniques, the performance of these adsorbents can be enhanced, making them competitive with commercial adsorbents. Overall, the use of marine animal waste as adsorbents represents an innovative approach that contributes to waste reduction and the enhancement of environmental sustainability.

Organic Carbon and Ca‐Rich Carbonate Detections in Soils of the Northern Plains, Mars: Evaluation of Unreported Data From the Mars Phoenix Scout's Thermal Evolved Gas Analyzer (TEGA)

AbstractThe Thermal Evolved Gas Analyzer (TEGA) analysis of surface and icy subsurface Phoenix landing site soils consisted of low (300–700°C) and high (>700°C) temperature CO2 evolutions that were attributed to organic carbon (83–1,484 μgC/g) and Ca‐rich carbonate (1.1–2.6 wt.%). Total carbon abundances ranged from 1,143 to 4,905 µgC/g, which is the highest soil carbon concentration so far detected on Mars. Low temperature CO2 was attributed to oxidized organic C (e.g., oxalates, acetates), while hydrocarbon combustion was indicated in two soils by the detection of coevolved CO2 and O2 (perchlorate). Combustion reactions may have prevented the detection of hydrocarbon masses in the Phoenix landing site soils. Organic C was likely derived from meteoritic and igneous/hydrothermal sources, but microbiological sources cannot be excluded. CO2 evolved at high temperatures was consistent with Ca‐rich carbonate along with possible minor contributions from macromolecular organic carbon and mineral/glass vesicle CO2. Carbon detected in the Phoenix landing site soil and other landing site soils and sands (e.g., Gale/Jezero craters) would be consistent with global organic C and carbonate in soils and sand across Mars. However, oxidizing water thin films derived from the near‐surface ice in the Phoenix soils favor Ca‐carbonate over Fe‐carbonate, which is likely more stable in the ice‐free regions of Mars (e.g., Gale/Jezero craters). The global carbon budget on Mars inferred from these results emphasizes that Mars Sample Return should yield carbon bearing soil/rock that would allow the identification of the origin of carbon and any possible connections to ancient martian microbiology.

Microbial Community and Functions Depending on Tillage and Straw Returning Management: Consequences for Soil Health and Ecosystem Services

ABSTRACTTillage and straw returning are promising practices to improve soil quality, especially because of the unclear controlling effects on microbial communities and functions. A 5‐year field experiment in a winter wheat‐summer maize cropping system was implemented in the North China Plain to address this research gap. Management practices were deep tillage, rotary tillage, and no‐tillage, each with either wheat only or both wheat and maize straw returning. Shotgun metagenomic sequencing was performed to investigate the microbial community, diversity, co‐occurrence network, and function in the topsoil (0–20 cm). The associations between soil physiochemical properties and microbial community characteristics were also evaluated. Rotary tillage with only wheat straw returning (RTS) significantly increased Shannon's diversity index by 0.24%–1.71% compared to other treatments. No‐tillage with only wheat straw returning (NTS) showed the most stable microbial network with the highest betweenness centrality (199.09), average path distance (2.31), and modularity (0.50). NTS had the highest relative abundance of microbial carbon (C), nitrogen (N) metabolisms, and C fixation pathways. Among deep tillage practices, both wheat and maize straw returning (DTD) were more beneficial to the stability of microbial networks than only wheat straw returning (DTS), yet without improvement in microbial diversity and function. In conclusion, microbial community and function are practical predictors of variations in soil nutrient availability, and pH value in response to different tillage and residue management practices. In particular, our study provides a basis for the development of a sustainable crop residue management system.