Sulfur Abundance Research Articles

The stable sulfur isotope and abundance fluxes of reduced inorganic sulfur and organic sulfur phases recorded in the Permian-Triassic transition of the Meishan type section

Sulfur cycle fluxes implicated in the Permian-Triassic mass extinction have traditionally been studied by the sulfur phase abundances in sedimentary rocks and the stable sulfur isotopic value (δ34S) of seawater sulfate inferred from mineral sulfate analyses. This information might be complemented by studies of the reduced inorganic sulfur and organic sulfur produced following bacterial sulfate reduction. To explore this potential the δ34S and concentration analyses of total reduced inorganic sulfur (TRIS) and organic sulfur – separately in the forms of kerogen (Ker) and individual organosulfur compounds, specifically dibenzothiophenes (DBTs) – has been conducted on sediments across the Late Permian to Early Triassic marine type section of Meishan-1 (South China). The relatively steady δ34S profiles (e.g., < 5 ‰ variation) of all sulfur phases measured through much of the late Permian were indicative of a primary seawater sulfate control, but other biogeochemical modulators caused prominent δ34S fluctuations of TRIS and DBT adjacent to the extinction event. The late Triassic δ34STRIS profile of Meishan-1 displayed a notable 34S enrichment (+15 ‰ increase) in bed 22–24 sediments concomitant with lower δ34SDBT values (−7 ‰ decrease), whereas co-eval δ34SKerS values remained relatively constant. The contrasting δ34SDBT and δ34SKerS data suggests the dynamic behavior of specific diagenetic sulfurisation processes may be resolved by the δ34S of discrete organic sulfur compounds (i.e., dibenzothiophenes, DBTs), but dissipated by the sulfurisation collective represented by the bulk kerogen fraction. The inverse isotopic trend observed between DBT and TRIS resulted in negative Δδ34SDBT-TRIS values identifying an organic sulfurisation pathway(s) with an unusual preference over pyrite (FeS2) for the lighter stable sulfur isotope. A redox control of the δ34SDBTs and δ34STRIS deviations in the bed 22–24 extinction interval was confirmed by coincident variation in TRIS/(TRIS + KerS) and pyrite (Py) and highly reactive (HR) iron ratios (FePy/FeHR). The iron (Fe) speciation data indicated a transition to ferruginous conditions, ruling out Fe2+ limitation as a factor in the bias against 34S evident in DBT formation. The 34S depletion of the DBTs promoted by the ferruginous setting may arise from the rapid and irreversible reaction of organic substrates with labile sulfur anions (e.g. HS-) or be supported by an especially localised sediment–water depositional microenvironment. Our study highlights the potential of incorporating stable sulfur isotope analytics of reduced and organic sulfur phases, particularly of specific organic compounds, into a holistic assessment of the dynamic sulfur biochemical periods of Earth’s past.

Chemical abundances and deviations from the solar S/O ratio in the gas-phase interstellar medium of galaxies based on infrared emission lines

Context. The infrared (IR) range is extremely useful in the context of chemical abundance studies of the gas-phase interstellar medium (ISM) due to the large variety of ionic species traced in this regime, the negligible effects from dust attenuation or temperature stratification, and the amount of data that has been and will be released in the coming years. Aims. Taking advantage of available IR emission lines, we analysed the chemical content of the gas-phase ISM in a sample of 131 star-forming galaxies (SFGs) and 73 active galactic nuclei (AGNs). In particular, we derived the chemical content via their total oxygen abundance in combination with nitrogen and sulphur abundances, and with the ionisation parameter. Methods. We used a new version of the code HII-CHI-MISTRY-IR v3.1, which allowed us to estimate log(N/O), 12+log(O/H), log(U) and, for the first time, 12+log(S/H) from IR emission lines, which can be applied to both SFGs and AGNs. We tested whether the estimates from this new version, which only considers sulphur lines for the derivation of sulphur abundances, are compatible with previous studies. Results. While most of the SFGs and AGNs show solar log(N/O) abundances, we find a large spread in the log(S/O) relative abundances. Specifically, we find extremely low log(S/O) values (1/10 solar) in some SFGs and AGNs with solar-like oxygen abundances. This result warns against the use of optical and IR sulphur emission lines to estimate oxygen abundances when no prior estimation of log(S/O) is provided.

Constraining the formation of WASP-39b using JWST transit spectroscopy

Context. Understanding the formation history of planets is one of the goals of studying exoplanet atmospheres. The atmospheric composition of planets can provide insights into the formation pathways of planets. Even though the mapping of the atmospheric composition onto a formation pathway is not unambiguous, with the increasing sensitivity of modern instruments, we can derive promising constraints. Aims. In this work, we aim to understand the formation pathway of WASP-39b. We discuss whether the detection of SO2 in its atmosphere would impact our understanding of the formation of the planet and whether it enables us to determine the formation pathway of the planet with greater accuracy. Methods. We used the JWST transit observation of the planet together with the available HST and Spitzer observations. We used a formation model coupled with a radiative transfer retrieval model to derive the planet's atmospheric characteristics and formation history. Furthermore, we used a photochemical model to derive the impact of photochemistry on the atmosphere of the planet. Results. In this work, we show that the planet is most likely to have initiated beyond the CO2 ice line of its natal disk. Furthermore, the planet is likely to have have accreted some planetesimals during its formation. We show that the sulfur abundance in the atmosphere of the planet is probably lower than 2.27 × 10−4. This abundance indicates that the planet is likely to exhibit a lower metallicity than suggested by the retrievals. Furthermore, such an abundance for sulfur is more likely if WASP-39b had been formed beyond the CO ice line of its natal disk.

Contribution of very massive stars to the sulfur abundance in star-forming galaxies: Role of pair-instability supernovae

Context. Recent work presented increasing evidence of high non-constant S/O abundance ratios observed in star-forming metal-poor galaxies that deviated from the constant canonical S/O across a wide range of O/H abundances. Similar peculiarly high Fe/O ratios have also recently been detected. Aims. We investigate whether these high S/O ratios at low metallicities could be explained when the process of pair-instability supernovae (PISN) in chemical modelling is included, through which a similar behaviour of the Fe/O ratios was reproduced successfully. Methods. We used chemical evolution models that considered the stages of PISN in the previously published yields and adopted a suitable initial mass function (IMF) to characterize this evolutionary stage appropriately. Results. The peculiarly high values and the behaviour of the observed S/O versus O/H relation can be reproduced when the ejecta of very massive stars that go through the process of PISN are taken into account. Additionally, a bimodal top-heavy IMF and an initial strong burst of star formation are required to reach the reported high S/O values. Conclusions. We show that the role of very massive stars going through the process of PISN should be taken into account to explain the chemical enrichment of sulphur and oxygen in metal-poor star-forming regions.

Elemental Abundances in the Diffuse Interstellar Medium from Joint Far-ultraviolet and X-Ray Spectroscopy: Iron, Oxygen, Carbon, and Sulfur

In this study, we investigate interstellar absorption lines along the line of sight toward the galactic low-mass X-ray binary Cygnus X-2. We combine absorption line data obtained from high-resolution X-ray spectra collected with the Chandra and XMM-Newton satellites, along with far-UV absorption lines observed by the Hubble Space Telescope’s (HST) Cosmic Origins Spectrograph (COS) instrument. Our primary objective is to understand the abundance and depletion of oxygen, iron, sulfur, and carbon. To achieve this, we have developed an analysis pipeline that simultaneously fits both the UV and X-ray data sets. This novel approach takes into account the line-spread function of HST/COS, enhancing the precision of our results. We examine the absorption lines of Fe ii, S ii, C ii, and C i present in the far-UV spectrum of Cygnus X-2, revealing the presence of at least two distinct absorbers characterized by different velocities. Additionally, we employ Cloudy simulations to compare our findings concerning the ionic ratios for the studied elements. We find that gaseous iron and sulfur exist in their singly ionized forms, Fe ii and S ii, respectively, while the abundances of C ii and C i do not agree with the Cloudy simulations of the neutral ISM. Finally, we explore discrepancies in the X-ray atomic data of iron and discuss their impact on the overall abundance and depletion of iron.

Physicochemical Variation of Water, Diversity, and Bacterial Community Structure in Post-coal Mining Ponds of Different Ages in Samarinda, East Kalimantan, Indonesia

&lt;p&gt;This study aims to determine physicochemical variation of water, diversity, and community structure of bacteria at post-coal mining ponds of various ages located in Samarinda, East Kalimantan, Indonesia. Bacteria species were identified using a metagenomic approach on the Next-Generation Sequencing (NGS) nanopore platform and analyzed using the QIIME2 pipeline. The result showed that ponds aged &amp;gt; 20 years old had better water quality compared to others &amp;lt; 5 years old. In addition, ponds &amp;gt; 20 years old had lower conductivity values (0,21-0,40 mS/cm), water temperature (29,1-30,1oC), and sulfur content (2,35-6,44 mg/L), as well as higher pH (6,57-7,61) and abundance of sulfur-oxidizing bacteria (SOB) (217-364 CFU/mL). Based on the results, ponds &amp;lt; 5 years old had water quality characterized by higher conductivity (0,27-1,29 mS/cm), water temperature (30,1-31,4 oC), and sulfur content (6,56-15,03 mg/L), lower pH (2,93-3,72), and abundance of SOB (0-38 CFU/mL). Diversity and structure of bacteria community showed that the Operational Taxonomic Unit (OTU) in post-coal mining ponds &amp;gt; 20 years old was 3819 compared to 2027 in those &amp;lt; 5 years old. Bacteria community in post-coal mining ponds &amp;gt; 20 years old consisted of 11 phyla and 45 classes, while those &amp;lt; 5 years old had 9 phyla and 38 classes. Moreover, the relative abundance of families, genera, and species at ponds &amp;gt; 20 years old was also higher. The high water quality, diversity, and community structure of bacteria at ponds &amp;gt; 20 years old showed the successful remediation of ponds water by SOB.&lt;/p&gt;

High-Loading Lithium-Sulfur Batteries with Solvent-Free Dry-Electrode Processing.

Lithium-sulfur (Li-S) batteries, with their high energy density, nontoxicity, and the natural abundance of sulfur, hold immense potential as the next-generation energy storage technology. To maximize the actual energy density of the Li-S batteries for practical applications, it is crucial to escalate the areal capacity of the sulfur cathode by fabricating an electrode with high sulfur loading. Herein, ultra-high sulfur loading (up to 12mgcm-2) cathodes are fabricated through an industrially viable and sustainable solvent-free dry-processing method that utilizes a polytetrafluoroethylene binder fibrillation. Due to its low porosity cathode architecture formed by the binder fibrillation process, the dry-processed electrodes exhibit a relatively lower initial capacity compared to the slurry-processed electrode. However, its mechanical stability is well maintained throughout the cycling without the formation of electrode cracking, demonstrating significantly superior cycling stability. Additionally, through the optimization of the dry-processing, a single-layer pouch cell with a loading of 9mgcm-2 and a novel multi-layer pouch cell that uses an aluminum mesh as its current collector with a total loading of 14mgcm-2 are introduced. To address the reduced initial capacity of dry-processed electrodes, strategies such as incorporating electrocatalysts or employing prelithiated active materials are suggested.

A Synthetic Microbiome Based on Dominant Microbes in Wild Rice Rhizosphere to Promote Sulfur Utilization

Sulfur (S) is one of the main components of important biomolecules, which has been paid more attention in the anaerobic environment of rice cultivation. In this study, 12 accessions of rice materials, belonging to two Asian rice domestication systems and one African rice domestication system, were used by shotgun metagenomics sequencing to compare the structure and function involved in S cycle of rhizosphere microbiome between wild and cultivated rice. The sulfur cycle functional genes abundances were significantly different between wild and cultivated rice rhizosphere in the processes of sulfate reduction and other sulfur compounds conversion, implicating that wild rice had a stronger mutually-beneficial relationship with rhizosphere microbiome, enhancing sulfur utilization. To assess the effects of sulfate reduction synthetic microbiomes, Comamonadaceae and Rhodospirillaceae, two families containing the genes of two key steps in the dissimilatory sulfate reduction, aprA and dsrA respectively, were isolated from wild rice rhizosphere. Compared with the control group, the dissimilatory sulfate reduction in cultivated rice rhizosphere was significantly improved in the inoculated with different proportions groups. It confirmed that the synthetic microbiome can promote the S-cycling in rice, and suggested that may be feasible to construct the synthetic microbiome step by step based on functional genes to achieve the target functional pathway. In summary, this study reveals the response of rice rhizosphere microbial community structure and function to domestication, and provides a new idea for the construction of synthetic microbiome.

Oxygen abundance of γ Vel from [O iii] 88 μm Herschel/PACS spectroscopy

ABSTRACT We present Herschel PACS spectroscopy of the [O iii] 88.4 μm fine-structure line in the nearby WC8+O binary system γ Vel to determine its oxygen abundance. The critical density of this line corresponds to several 105R* such that it is spatially extended in PACS observations at the 336 pc distance to γ Vel. Two approaches are used, the first involving a detailed stellar atmosphere analysis of γ Vel using cmfgen, extending to Ne ∼ 100 cm−3 in order to fully sample the line formation region of [O iii] 88.4 $\mu$m. The second approach involves the analytical model introduced by Barlow et al. and revised by Dessart et al., additionally exploiting ISO LWS spectroscopy of [O iii] 51.8 $\mu$m. We obtain higher luminosities for the WR and O components of γ Vel with respect to De Marco et al., log L/L⊙ = 5.31 and 5.56, respectively, primarily due to the revised (higher) interferometric distance. We obtain an oxygen mass fraction of XO = 1.0 ± 0.3 per cent for an outer wind volume filling factor of f = 0.5 ± 0.25, favouring either standard or slightly reduced Kunz et al. rates for the 12C(α, γ)16O reaction from comparison with BPASS binary population synthesis models. We also revisit neon and sulphur abundances in the outer wind of γ Vel from ISO SWS spectroscopy of [S iv] 10.5 $\mu$m, [Ne ii] 12.8 $\mu$m, and [Ne iii] 15.5 $\mu$m. The inferred neon abundance XNe = 2.0$_{-0.6}^{+0.4}$ per cent is in excellent agreement with BPASS predictions, while the sulphur abundance of XS = 0.04 ± 0.01 per cent agrees with the solar abundance, as expected for unprocessed elements.

Spatially resolving the volatile sulfur abundance in the HD 100546 protoplanetary disc

ABSTRACT Volatile elements play a crucial role in the formation of planetary systems. Their abundance and distribution in protoplanetary discs provide vital insights into the connection between formation processes and the atmospheric composition of individual planets. Sulfur, being one of the most abundant elements in planet-forming environments, is of great significance, and now observable in exoplanets with JWST. However, planetary formation models currently lack vital knowledge regarding sulfur chemistry in protoplanetary discs. Developing a deeper understanding of the major volatile sulfur carriers in discs is essential to building models that can meaningfully predict planetary atmospheric composition, and reconstruct planetary formation pathways. In this work, we combine archival observations with new data from the Atacama Large sub-Millimeter Array (ALMA) and the Atacama Pathfinder EXperiment (APEX), covering a range of sulfur-bearing species/isotopologs. We interpret this data using the dali thermo-chemical code, for which our model is highly refined and disc-specific. We find that volatile sulfur is heavily depleted from the cosmic value by a factor of ∼1000, with a disc-averaged abundance of S/H ∼ 10−8. We show that the gas-phase sulfur abundance varies radially by ≳3 orders of magnitude, with the highest abundances inside the inner dust ring and coincident with the outer dust ring at r ∼ 150–230 au. Extracting chemical abundances from our models, we find OCS, H2CS, and CS to be the dominant molecular carriers in the gas phase. We also infer the presence of a substantial OCS ice reservoir. We relate our results to the potential atmospheric composition of planets in HD 100546, and the wider exoplanet population.

Biomineralization in a cold environment: Insights from shield compositions and transcriptomics of polar sternaspids (Sternaspidae, Polychaeta)

The survival and physiological functions of polar marine organisms are impacted by global climate changes. Investigation of the adaptation mechanisms underlying biomineralization in polar organisms at low temperatures is important for understanding mineralized organismal sensitivity to climate change. Here, we performed electron probe analysis on the shields of Antarctic polychaete Sternaspis sendalli and Arctic polychaete Sternaspis buzhinskajae (Sternaspidae), and sequenced the transcriptomes of the tissues surrounding shields to examine biomineral characteristics and adaptive mechanisms in persistently cold environments. Compared to the temperate relative species, the relative abundance of iron, phosphorus, calcium, magnesium, nitrogen, sulfur and silicon in two polar sternaspid shields was similar to Sternaspis chinensis. However, the diversity and expression levels of biomineralization-related shell matrix proteins differed between the polar and temperate species, suggesting distinct molecular mechanisms underlying shield formation in cold environments. Tubulin and cyclophilin were upregulated compared to the temperate species. Furthermore, 42 positively selected genes were identified in Antarctic S. sendalli, with functions in cytoskeletal structure, DNA repair, immunity, transcription, translation, protein synthesis, and lipid metabolism. Highly expressed genes in both polar species were associated with cytoskeleton, macromolecular complexes and cellular component biosynthesis. Overall, this study reveals conserved elemental composition yet distinct biomineralization processes in the shields of polar sternaspids. The unique expression of biomineralization related genes and other cold-adaptation related genes provide molecular insights into biomineralization in cold marine environments.

Potassium and Sulfur Fertilizer Sources Influence Alfalfa Yield and Nutritive Value and Residual Soil Characteristics in an Arid, Moderately Low-Potassium Soil

Alfalfa (Medicago sativa L.) requires a large amount of potassium (K) for maintaining forage yield and stand persistence. Therefore, soil inherently low in K levels must be supplemented with K fertilizers. Although several commercial K fertilizers are available on the market, choosing an appropriate K-supplementing source for a particular soil can be crucial in boosting alfalfa yield and nutritive value. A two-year study was conducted in an arid southern New Mexico location near Tularosa to evaluate the efficacy of three K commercial fertilizer sources in improving alfalfa yield and nutritive value in a moderately low potassium (84 ppm) soil. Nine K treatments or combinations and a no-K control were tested in a randomized complete-block design with four replications. Overall, supplementation of 160 kg ha−1 of K2O in all treatments resulted in a significant increase in alfalfa seasonal forage yield and nutritive value compared to the control. Sulfate of potash combined with ammonium sulfate (AS) produced greater seasonal yield compared to other fertilizers (muriate of potash and potassium nitrate) or combinations with gypsum (p &lt; 0.05). This treatment combination also showed greater crude protein, neutral detergent fiber, tissue Fe and S, and soil residual sulfate-S and nitrate-N. A positive correlation between sulfur abundance and nitrogen availability in alfalfa production was evident in the study. Addition of AS to all three K fertilizers yielded better seasonal forage yield than K fertilizers alone or K fertilizers in combination with gypsum. Adding gypsum to the K-fertilizers appeared to have negative effect on the seasonal forage yield. Future research should evaluate various combinations of the levels of K and S to determine the most reasonable balance.

Electrochemical Investigations of Sulfur-Decorated Organic Materials as Cathodes for Alkali Batteries.

Alkali metal-sulfur batteries (particularly, lithium/sodium- sulfur (Li/Na-S)) have attracted much attention because of their high energy density, the natural abundance of sulfur, and environmental friendliness. However, Li/Na-S batteries still face big challenges, such as limited cycle life, poor conductivity, large volume changes, and the "shuttle effect" caused by the high solubility of Li/Na-polysulfides. Herein, novel organosulfur-containing materials, i.e., bis(4-hydroxy-2,2,6,6-tetramethylpiperidin-1-yl)disulfide (BiTEMPS-OH) and 2,4-thiophene/arene copolymer (TAC) are proposed as cathode materials for Li and Na batteries. BiTEMPS-OH shows an initial discharge/charge capacity of 353/192mAhg-1 and a capacity of 62mAhg-1 after 200 cycles at 100mAg-1 in ether-based Li-ion electrolyte. Meanwhile, TAC has an initial discharge/charge capacity of 270/248mAhg-1 and better cycling performance (106mAhg-1 after 200 cycles) than BiTEMPS-OH in the same electrolyte. However, the rate capability of TAC is limited by the slow diffusion of Li-ions. Both materials show inferior electrochemical performances in Na battery cells compared to the Li analogs. X-ray powder diffraction reveals that BiTEMPS-OH loses its crystalline structure permanently upon cycling in Li battery cells. X-ray photoelectron spectroscopy demonstrates the cleavage and partially reversible formation of S-S bonds in BiTEMPS-OH and the formation/decomposition of thick solid electrolyte interphase on the electrode surface of TAC.

Multifunctional separator modified with catalytic multishelled structural CoS2 enables stable lithium-sulfur battery

Lithium-sulfur battery has been considered as a promising next-generation energy storage device, due to its ultrahigh theoretical energy density and natural abundance of sulfur. However, the shuttle effect and sluggish...

Multi-Scale Analysis of Lithium-Sulfur Pouch Cells Using Imaging Methods

Lithium-sulfur batteries (Li-S) are promising energy storage technologies. Its high gravimetric energy density, the abundance of sulfur and low costs at high production volume, this battery type is especially applicable for automotive and aerospace applications. In recent years, the number of reported prototype cells has increased, as well as their accessible energy density. This underlines the progress of technology readiness of the Li-S system. However, despite this important breakthrough density and cycling stability have to be overcome in the Li-S research. Additionally, the influence of the cathode porosity as well as the surface of the carbon material and the electrolyte composition play an important role on the conversion of sulfur and the performance of prototype cells.Hard X-ray beamlines, as BAMline at the electron storage ring BESSY II in Berlin, Germany, have now been in service for over two decades. Several improvements have been implemented, allowing for operando tomography and fast radiographic measurements on the micrometer scale by using well-shaped synchrotron X-ray beam. In this study, operando X-ray imaging measurements on Li-S pouch cells are complemented by scanning and transmission electron microscopy and focused-ion-beam measurements on the nanometer scale delivering unique and multi-scale results about the morphology of sulfur inside the porous cathode material. Therefore, tiny pouch cells designs have been developed, allowing for operando tomography of stacked cells. Figure 1

Challenges and Breakthroughs Towards the Development and Optimisation of a Zero Excess Li-S Battery

There is currently a large demand to produce batteries and energy storage devices offering both improved volumetric and gravimetric energy densities to help prevent the catastrophic effects of climate change. One promising candidate is the lithium-sulfur (Li-S) chemistry due to the high theoretical capacity and abundance of sulfur. However, current designs require a 1000% excess of Li metal which impedes their commercialisation. An area gaining momentum is the development of “anode-free” or zero excess lithium (ZEL) cells which minimise inactive materials and mitigate the challenges of handling Li metal foils during fabrication. So far, most studies involving anode-free have been based on the Li-ion chemistry and there are significantly fewer systematic studies concerning ZEL Li-S cell fabrication and optimisation. However, nearly all fall short of targets required for commercialisation.Here we present the development of an Li2S ZEL cell composed of a Li2S/C65/SBR positive electrode material paired with a metallic current collector. The design allows for a Li-limited LiS battery where Li-ions are reversibly plated and stripped to a metallic current collector surface. We initially investigate the effects of electrolyte volume :Li2S mg (ES) ratio, conductive carbon loading, C-rate capacity dependency, various current collector materials and positive electrode substrates. The optimised cell achieves good capacity retention with a Coulombic efficiency of over 98% after 50 cycles, and a final capacity of 400 mAh g-1.Previous studies have shown difficulties in achieving consistent results and are often distorted by a large volume of conductive carbon present in the cathode substrate [1, 2]. Therefore, investigations into capacity losses stemming from the cathode are presented using a range of air-tight characterisation techniques. The performance is also closely correlated to the efficiency of reversible Li deposition onto the metallic current collector, as evaluated by comparison to the use of Li negative electrodes. In the ZEL set up, losses from dead Li formation and SEI instability result in permanent loss of Li inventory with no reservoir to replenish. To counter this, initial investigations attempting to apply an ionically conductive coating to the metal current collector surface are shown.[1]. S. Nanda, A. Gupta and A. Manthiram, Adv. Energy Mater., 2018, 8, 2–7.[2]. S. Nanda, A. Bhargav and A. Manthiram, Joule, 2020, 4, 1121–1135.

Predicting sulfide precipitation in magma oceans on Earth, Mars and the Moon using machine learning

The sulfur content at sulfide saturation (SCSS) of a silicate melt can regulate the stability of sulfides and, therefore, chalcophile elements’ behaviors in planetary magma oceans. Many studies have reported high-pressure experiments to determine SCSS using either linear or exponential regressions to parameterize the thermodynamics of the system. Although these empirical equations describe the effects of different parameters on SCSS, they perform poorly when predicting laboratory measurements. Here, we compiled 542 published analyses of experiments performed on a range of sulfide and silicate compositions at varying P-T conditions (<24 GPa, <2673 K). Using empirical equations, linear regression, Random Forest algorithms, and a hybrid algorithm employing empirical fits to P-T conditions and the Random Forest algorithm for compositions, we developed several SCSS models and compared them to laboratory measurements. The Random Forest and hybrid models (R2 = 0.82–0.91, mean average error [MAE] < 746 ppmw S, residual mean standard error [RMSE] < 972 ppmw S), significantly outperform previous empirical models (R2 = 0.28–0.69, MAE = 622–1,170 ppmw S, RMSE = 1,070–1,744 ppmw S), whereas linear regression performs moderately well, i.e., between the classic and machine learning models. We applied our hybrid model to predict SCSS during magma ocean solidification on Earth, Mars, and the Moon, and we compared our model results to expected S contents in the residual magma oceans calculated by mass balance. Our results confirm that during early accretion, sulfides precipitated from magma oceans and into the outer cores of Earth and Mars, but not the Moon. Subsequently, once the respective magma oceans began precipitating minerals with increasingly FeO-rich and SiO2-, Al2O3-, and MgO-depleted compositions, the increasing S concentration in the residual magma was offset by temperature and compositional effects on SCSS, preventing sulfide precipitation during intermediate stages of crystallization. Sulfides precipitated late during magma ocean crystallization, but failed to percolate through the underlying crystalline mantle, significantly contributing to the modern bulk-silicate sulfur abundances of Earth, Mars, and the Moon. Our calculations suggest that late-stage sulfide precipitation occurred at shallow depths of 120–220 km, 40–320 km, and < 10 km in the magma oceans of Earth, Mars, and the Moon, respectively.

PTFE nanofiber cross-linked acetylene black: A flexible self-supporting semi-confined architecture for ultra-high sulfur loading and areal capacity

Lithium-sulfur batteries attract great interest due to their high energy density, sulfur abundance and environment friendly. However, the shuttle effect of lithium polysulfide and serious capacity fading especially at high sulfur loading remains a challenge for their commercial applications. In this work, we propose a scalable and feasible strategy to construct a flexible host for sulfur and catalyst carrier, in which polytetrafluoroethylene is employed as a precursor and in-situ polymerized into nanofibers to link acetylene black (PTFE NF/AB) through a blend and low temperature (∼ 180 °C) treatment process. The PTFE NF/AB exhibits semi-confined architecture for sulfur accommodation, electrolyte infiltration and electron transformation. Impressively, the electrode achieves a high areal capacity of 14.6 mAh cm−2 at the current density of 4.82 mA cm−2 with a sulfur loading of 20.6 mg cm−2. Moreover, the PTFE NF/AB architecture can be employed as the catalyst supports. The capacity can be further enhanced to 17.4 mAh cm−2 when MoS2 fabricated into the PTFE NF/AB using a ball mill approach. Assembled into a pouch cell, the PTFE NF/AB architecture delivers a high capacity of 825.4 mAh g−1 in the folded state, showing its excellent potential in the high-energy flexible territory.

Spectral study of the planetary nebula NGC 2452

We provide a detailed study for the Galactic planetary nebula (PN) NGC 2452, which has long been suspected to be a member of the Galactic cluster NGC2453. The present study uses integral field unit (IFU) spectroscopic observations of the PN to explore its physical conditions, chemical abundances, kinematical characteristics, and morphological features. The strength of the singly ionized helium (HeII λ4686) line reveals that the PN is of high excitation class. The presence of the neutral lines of [OI] and [NI] a long with the value of the flux ratio F([Nii]λ6583)/F(Hα) indicates that the object is slightly optically thick. We compute the nebular density and temperature from a large number of diagnostic line ratios. The ionic and total abundances of helium (He) and carbon (C) are derived from their optical recombination lines (ORLs), while the abundances of nitrogen (N), oxygen (O), neon (Ne), argon (Ar), sulphur (S), and chlorine (Cl) are derived from their collisionlly-excitation lines (CELs). Faint lines like Krypton (Kr), Manganese (Mn), and Chromium (Cr), which are known to be products of the slow-process (s-process), are also seen in the PN spectrum. To illustrate the morphology and excitation structures of the PN, we generate a gallery of emission-line maps using the nebular data cubes. We find that the PN has an overall elliptical shape with a few interior clumps. In terms of physical and chemical properties, we find no significant differences between the entire PN and its accompanying clumps, considering the uncertainties associated with these parameters. Both the astronomical data from Gaia and the inferred radial velocity suggest that the PN belongs to the Galactic thin-disk.

Hypoxia diversifies molecular composition of dissolved organic matter and enhances preservation of terrestrial organic carbon in the Yangtze River Estuary

Dissolved organic matter (DOM) is an essential component of the global carbon cycle, and estuaries link the rivers and the oceans, thus playing important roles in land-ocean DOM transformation and transport. However, the effects of hypoxia on DOM transport and fate in estuaries and coastal oceans remains poorly understood. To address this gap, we characterized the molecular composition of DOM in bottom water (BW) and sediment porewater (PW) at hypoxic and non-hypoxic sites in the Yangtze River Estuary (YRE) using ultra-high-resolution Fourier transform ion cyclotron resonance mass spectrometry. Our results showed significant differences in DOM molecular composition between hypoxic and non-hypoxic areas for both BW and PW. Specifically, DOM in hypoxic sites was more recalcitrant than that in non-hypoxic areas for both BW and PW, with lower H/C, and higher O/C, double bond equivalent, and modified aromaticity index. The presence of higher polyphenols, and black carbon in hypoxic areas suggested that hypoxic conditions could facilitate the preservation of terrestrial organic matter. Furthermore, we identified a much higher number of hypoxia-unique formulas than ocean-non-hypoxia-unique formulas, indicating that hypoxia could diversify the DOM pool. Within hypoxia-unique formulas for PW, both biologically labile (unsaturated aliphatic compounds and peptides) and recalcitrant formulas (carboxyl-rich alicyclic molecules) were found, suggesting that hypoxia could facilitate the preservation of labile formulas and the production of recalcitrant formulas. In addition, we formulated that the sulfurization is more important in PW than BW in hypoxic areas based on the higher dissolved organic sulfur (DOS) abundance and larger number of hypoxia-only formulas in hypoxic PW, and also the precursor analysis results. Overall, our study provides insights into the effect of hypoxia on the molecular characteristics and preservation of DOM in estuaries and coastal oceans, highlighting the importance of considering hypoxia in understanding the biogeochemical processes of these ecosystems.