Carbon Composite Research Articles

Low-cost preparation and characterization of new CuO/ZnO and Cu3N/ZnO nanocomposites

CuO/ZnO and Cu3N/ZnO nanocomposites were prepared in a three-step synthesis consisting of the co-precipitation of Cu2+ and Zn2+ hydroxide carbonates (Cu/Zn-Carb) followed by their thermal treatment first in air and second in gaseous ammonia. The morphology and phase composition of the hydroxide carbonates were determined by the Cu:Zn molar ratio and the presence of polyvinylpyrrolidone (PVP) acting as a capping agent, respectively. The Cu/Zn-carbonates could be annealed in the air at 550 °C either as powders or as thin films. The latter were deposited on a silicon substrate using a choice of spin- or dip-coating techniques. The resulting CuO/ZnO samples were heated under gaseous ammonia at 300 °C in the final step of the process to form Cu3N/ZnO nanocomposites. The fabricated samples were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) with energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), thermogravimetric − differential thermal analysis (TG-DTA) and infrared spectroscopy (IR). SEM and XRD analysis indicates that the average diameter of spherical particles was about 130 nm (CuO/ZnO) and 100 nm (Cu3N/ZnO), composed of crystallites with 10–20 nm sizes. The thermal treatment under air and NH3 did not affect the morphology of the composites. The implication is, therefore, that the shape and size of CuO/ZnO oxide and Cu3N/ZnO nitride/oxide composite nanostructures are determined at the point of hydroxide carbonate coprecipitation and can be controlled during precursor synthesis. This has significant ramifications for the reproducible fabrication of nanocomposite films of precise stoichiometry and bespoke morphology.

Icelandic glacial dissolved organic carbon fluxes, composition and variability - relevance for the global glacial carbon budget

Despite their relatively large size, Icelandic glaciers, and their organic carbon (OC) fluxes, have not been explicitly considered in current global glacial OC flux calculations. Most global glacial OC estimates are based on limited individual flux estimates, often determined during the melt season, rarely accounting for the seasonal and diurnal variability of glacial dissolved organic matter (DOM). Using an annual dataset of 25 Icelandic glaciers (and their glacial streams) we investigate DOM concentration and composition, calculating an estimate for downstream OC fluxes from Icelandic glaciers, considering diurnal and seasonal variability. DOM source and composition distinctly changed from a terrestrial character toward a more proteinaceous character as melt increased, both on a seasonal and diurnal basis, likely reflecting the flow path of the meltwater. While DOC concentration did not change on a diurnal basis, DOM composition was more labile in the afternoons, possibly indicating photochemical or biological transformation processes. Overall, the glacial streams predominantly acted as CO2 sinks. However, higher DOC concentrations, along with contributions of more proteinaceous DOM in proglacial streams, led to a decrease in the uptake potential for CO2. Finally, we estimated an export flux of 0.0026 ± 0.0029 Gg C yr−1 km−2 of DOC, and 0.011 ± 0.007 Tg C yr−1 km−2 of POC, from Icelandic glaciers. We reveal larger than previously assumed DOC and POC fluxes from Icelandic glaciers, with higher-than-global-average areal fluxes (~3 % and 9 % of global glacial C flux respectively). Our findings underscore the importance of revising current global estimates to include the not-fully-accounted-for contribution of Icelandic, and other glaciers. This is particularly important considering ongoing climatic changes will likely affect glacial meltwater discharge and sources, leading to altered DOM composition and DOC concentration, having potentially considerable consequences for glacial OC export and CO2 uptake potentials of glacial streams.

The waste recycling approach for enhancing wastewater sludge dewaterability by using iron-mud (IM)/sawdust derived carbon composite

The dewaterability of wastewater sludge by the solid waste of iron-mud (IM)/carbon (IMS) composite prepared via the in-situ carbothermal reduction method was systematically studied in this paper. It investigated the effects of different IMS materials, IM dosages and stirring speeds on sludge dewaterability, including water content (WC), capillary suction time (CST), extracellular polymeric substances (EPS) contents and particle size. The results of dewatering tests demonstrated that IMS materials significantly enhanced sludge dewaterability, resulting in a reduction of 39.85 % in CST and 13.26 % reduction in WC in the dewatered sludge under optimum condition (IMS-3 dosage of 8 % dry solids; stirring speed of 250 r/min for 30 min). Electron paramagnetic resonancec (EPR) and scavenging experiments were conducted to better understand the dewatering process mechanism. This results indicated that both hydroxyl radicals (•OH) and superoxide radicals (•O2−) collaborate during the dewatering process. Furthermore, analysis were performed on the particle size of sludge flocs and scanning electron microscopy (SEM) imaging of sludge morphology to reveal the synergistic effects of IMS treatment. A two-step mechanism involving oxidation and Fe(III)-based re-flocculation maybe explain the synergistic effect of IMS treatment. This novel recycle-based IMS composite approach offers a new management strategy for industrial solid wastes while enhancing the sludge dewatering efficiency.

Chromium Oxide Nanoparticles Anchored in Hydrogel-Derived Three-Dimensional N-Doped Porous Carbon Anode Materials as Lithium-Ion Batteries.

Transition metal oxides (TMOs) have been identified as the most promising anode materials for lithium-ion batteries (LIBs). However, these materials tend to undergo volumetric expansion during battery operation, which disrupts their internal structure and ultimately leads to a degradation of battery performance. Cr2O3/N-doped porous carbon (Cr2O3@NC) composites were successfully synthesized through high-temperature calcination using Cr2O3-containing hydrogels as precursors. The results show that the carbon material not only improves the electron transfer ability of Cr2O3 but also effectively prevents its agglomeration. The Cr2O3@CN composite as a novel anode material for LIBs exhibits a reversible capacity of 936 mAh g-1 after 200 cycles at a current density of 1 A g-1, showcasing excellent cycling and structural stability during cycling. Scanning electron microscopy analysis reveals that the Cr2O3@NC composite remains structurally intact throughout cycling. The innovative approach proposed in this study provides a new direction for the advancement of electrode materials for energy storage technologies.

THIN FILM METHANE SENSOR BASED ON CARBON COMPOSITE

Today, with the oil and gas industry playing a key role in the global energy sector, issues related to the effective control and detection of methane leaks are becoming an integral part of the strategic tasks of the industry. The article is devoted to the research and development of a thin-film sensor for detecting methane in the air using a carbon composite. The technical result of this study is the creation of a highly sensitive and energy efficient sensor for measuring methane concentration. The basis for the sensitive element is a thin film of a carbon composite, consisting of a polymer, single-wall carbon nanotubes and graphene oxide, with aluminum electrodes. The sensor has a number of advantages, including responding to the presence of methane without the need for heating, the simplicity of the sensitive material preparation process, and low cost. The ability to quickly start small-scale production, simplified manufacturing due to the use of only one pair of electrodes, as well as increased energy efficiency due to the absence of the need for heating are also positive characteristics of this device. The study presents the results of manufacturing the sensor, including the steps of cleaning the surface of the substrate, creating a shadow mask, spraying electrodes, forming a thin film of the composite by centrifugation, as well as analyzing the microstructure of the sensor using an atomic force microscope. Also presented are data on obtaining multilayer structures of thin-film resistive sensors based on a polymer matrix nanocomposite, single-wall carbon nanotubes and graphene oxide, including the process of creating electrodes. This study is important for the development of methane monitoring methods in the oil and gas industry and other industrial areas, offering promising technical solutions to ensure environmental and economic sustainability of production.

IoT real-time monitoring system implemented to observe sunlight-influenced methylene blue degradation by AC/HAp.

Activated carbon (AC) and hydroxyapatite (HAp) composite were successfully prepared via mechanical mixing and exhibited a crushed snack-like morphology compared to the well-defined pore structure of pure AC. The purpose of this research was to explore the potential of AC/HAp for the degradation of methylene blue (MB) dye and hydrogen production. Despite the morphological changes, AC and AC/HAp achieved a high MB degradation rate (92.75 and 82.05) % under sunlight, at a temperature of 26.24°C and pH of 4.18, and showed optimum hydrogen production (3579mol/g.h). These performances are suspected from the decrease in crystallite size and narrowed and confirmed by image processing results with RBG enhancement showing more light transmitted by the solution. Increasing in indicates the potential for improved light interaction. IoT-enabled real-time monitoring system demonstrates its efficacy in facilitating wastewater treatment and hydrogen production, offering a promising solution for aquatic ecosystem restoration.

Organic matter processing by heterotrophic bacterioplankton in a large tropical river: Relating elemental composition and potential carbon mineralization.

River hydrology shapes the sources, concentration, and stoichiometry of organic matter within drainage basins. However, our understanding of how the microbes process dissolved organic matter (DOM) and recycle nutrients in tropical rivers needs to be improved. This study explores the relationships between elemental DOM composition (carbon/nitrogen/phosphorus: C/N/P), C and N uptake, and C mineralization by autochthonous bacterioplankton in the Usumacinta River, one of the most important fluvial systems in Mexico. Our study investigated changes in the composition and concentration of DOM and evaluated carbon dioxide (CO2)production rates (C-CO2) through laboratory experiments. We compared three sites representing the middle and lower river basins, including their transitional zones, during the rainy and dry seasons. After incubation (120 h at 25°C), the DOM decreased between 25% and 89% of C content. Notably, the initial high proportion of C in DOM in samples from the middle-forested zone and the transition led to elevated C-CO2 rates (>10 mg l-1 day-1), in contrast to the lower initial C proportion and subsequent C-CO2 rates (<7 mg l-1 day-1) in the lower river basin. We also found that dissolved organic carbon uptake and NO3- and NH4+ production were higher during the dry season than in the rainy season. The low water flow in the river during the dry season accentuated the differences in elemental composition and microbial processing of DOM among the sites, while the high water flow of the rainy season homogenized these factors. Our findings indicate that microbial metabolism operates with reduced efficiency in C-rich environments like forests, particularly when faced with high C/N and C/P ratios in DOM. This study highlights the influence of the tropical hydrological regime (rainy and dry seasons) and the longitudinal changes in the river basin (middle and lower) topography and land cover on microbial metabolism by constraining DOM characteristics, emphasizing the crucial role of elemental ratios in river DOM processing.

Composite Mesozoic Carbon and Oxygen Isotope Signals of Selected Events as Encountered in the Southern Tethyan Margin: an Overview

Composite Mesozoic Carbon and Oxygen Isotope Signals of Selected Events as Encountered in the Southern Tethyan Margin: an Overview

Analysis of Brucine using Poly(L-Arginine) modified biosynthesized CuO nanoparticle composite sensor

The study investigated the sensitive and selective electrochemical behavior of Brucine (BC) using electrochemically polymerized L-Arginine (LA) modified with a composite comprising biosynthesized copper oxide (CuO) nanoparticles (NPs) and carbon paste electrode (PAMCuONPs/CPE). PAMCuONPs/CPE showed an optimum reversible redox-peak at 0.2 M phosphate buffer solution (PBS) at pH 2.5, allowing detection of BC. The characterization of PAMCuONPs/CPE and bare CuONPs composite carbon paste electrode (BCuONPs/CPE) was performed using scanning-electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive spectroscopy (EDS). Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and linear sweep voltammetry (LSV) methods were employed to evaluate the performance of PAMCuONPs/CPE. Experimental parameters, including pH, and variation of concentration, were investigated. PAMCuONPs/CPE exhibited an electrochemical performance with a limit of detection (LOD) of 0.12×10−6 M and a limit of quantification (LOQ) of 0.43×10−6 M. It demonstrated good reproducibility, repeatability, and stability. PAMCuONPs/CPE was successfully validated in determining BC in real samples.

Stable isotopic evidence for increased terrestrial productivity through geological time

Marine life on Earth is known back to the Archean Eon, when life on land is assumed to have been less pervasive than now. Precambrian life on land can now be tested with stable isotopes because living soil CO2 is isotopically distinct for both carbon and oxygen from both marine and volcanic CO2. Our novel compilation of previously published oxygen and carbon isotopic compositions of pedogenic and paleokarst carbonate can be compared with the coeval marine record. Long-term enrichment (to heavier isotopic composition) of oxygen, but no significant trend in carbon through time, long apparent from marine carbonate, is now demonstrated also for pedogenic and paleokarst carbonate. Oxygen isotopic enrichment is not due to changing global temperature or hypsometry, but to increased evapotranspiration and photosynthesis on larger continents. Differences in isotopic composition between land and sea have increased in an episodic fashion, peaking at times of major evolutionary innovations for life on land, and also at times of ice ages. The δ13C and δ18O divergences between land and sea correspond to terrestrial productivity spikes including evolution of Neoproterozoic (635 Ma) lichens, middle Ordovician (470 Ma) non-vascular land plants, middle Devonian (385 Ma) forests, early Cretaceous (125 Ma) angiosperms, and middle Miocene (20 Ma) sod grasslands.

Transcriptomics-guided rational engineering in Bacillus licheniformis for enhancing poly-γ-glutamic acid biosynthesis using untreated molasses

The utilization of non-food raw materials for microbial synthesis of poly-γ-glutamic acid (γ-PGA) presents a promising alternative to conventional food-based biosynthesis. However, the complex carbon source and composition of molasses, a prevalent non-food raw material, may impose constraints on its conversion and utilization by microorganisms. This study aimed to enhance the capacity of Bacillus licheniformis to convert untreated molasses into γ-PGA through transcriptomic analysis to guide metabolic modifications. Initial results from the transcriptomic analysis indicated that the strain utilizing molasses exhibited decreased expression of genes associated with substrate utilization (Module 1) and by-product synthesis (Module 2), while upregulating genes related to precursor synthesis (Module 3). Furthermore, we performed a knockout of the acetolactate synthase (AlsS) to reduce the synthesis of metabolic by-products and a knockout of the global regulator (CcpA) to alleviate carbon catabolite repression (CCR) and then promote substrate utilization. Ultimately, following the tandem overexpression of precursor supplying key genes, the titer of γ-PGA reached 48.26 g/L with a productivity of 1.15 g/L/h, using untreated molasses as the sole carbon source, which was 3.12-fold of the starting strain. These findings offer significant insights into the cost-effective synthesis of γ-PGA by bioconversion of untreated molasses during fermentation.

Progress in the application of silicon-based materials in lithium-ion batteries anodes

From the battery that powers the remote control to the battery that powers electric cars, lithium-ion batteries (LIBs) are a crucial component of contemporary energy storage. The large theoretical capacity of silicon anodes provides significant benefits inside LIBs. However, the main issue with the conventional silicon bulk anode is its considerable volume expansion, which forms an unstable Solid Electrolyte Interface (SEI) layer during the charge and discharge process and severely reduces battery performance and lifespan. Therefore, to solve these issues, researchers have explored multiple improved silicon anodes, three of which are mentioned in this essay. Firstly, the researchers delve into the usage of nanotechnology. When manipulating silicon particles at the nano-scale, the nano-silicon can mitigate the volume expansion, improving the reaction kinetics. Then, a composite of carbon and silicon is proposed, combining silicon's high capacitance and carbon's high conductivity. After that is the silicon-metal composite, which utilizes metals' mechanical strength and conductivity to stabilize Si anodes further and improve thermal stability. Overall, the significance of this study lies in the exploration of the application of silicon anodes in LIBs, highlighting the potential of these composite materials and advanced technology, which may help guide the future exploration of better silicon anodes.

Innovative Marine-Sourced Hydroxyapatite, Chitosan, Collagen, and Gelatin for Eco-Friendly Bone and Cartilage Regeneration.

In recent years, the exploration of sustainable alternatives in the field of bone tissue engineering has led researchers to focus on marine waste byproducts as a valuable resource. These marine resources, often overlooked remnants of various industries, exhibit a rich composition of hydroxyapatite, collagen, calcium carbonate, and other minerals essential to the complex framework of bone structure. Marine waste by-products can emit gases such as methane and carbon dioxide, highlighting the urgency to repurpose these materials for innovative tissue regeneration solutions, offering a sustainable approach to address environmental challenges while advancing medical science. Using these discarded materials offers a promising pathway for sustainable development in regenerative medicine. This review investigates the distinctive properties of marine waste byproducts, emphasizing their capacity to be recycled effectively to contribute to the rebuilding of bone and cartilage tissue during regeneration processes. We also highlight the compatibility of these resources with biological materials such as platelet-rich plasma (PRP), stem cells, exosomes, and natural bioproducts, as well as nanoparticles (NPs) and polymers. By using the natural potential of these resources, we simultaneously address environmental challenges and promote innovative solutions in skeletal tissue engineering, initiating a new era of environmentally green biomedical research.

Morphological and dynamic mechanical properties of biobased epoxy composites with anisotropic, green carbon aerogels as reinforcement

Hierarchically porous, anisotropic, and green carbon aerogels (CAs) prepared from second most abundant and underutilized biopolymer lignin is used together with biobased epoxy resin to prepare green composite materials with superior mechanical properties. Green and facile preparation route involving ice-templating, lyophilization followed by carbonization was followed for the preparation of CAs. Ice-templating cooling rate is an important parameter in determining the porous structure of the CAs and by choosing a slower cooling rate bigger macropores can be achieved which facilitate the capillary impregnation of the epoxy resin through the CA structure. Hence in this study a cooling rate of 5 K/min was used and the CAs were prepared at 1000 °C from lignin/CNF suspensions containing 3, 5 and 7 wt% of total solid contents. Composites prepared using these CAs as reinforcements showed interesting morphologies which were analyzed using scanning electron microscopy and X-Ray microtomography. Prepared composites contained a mass fraction of 5–9 wt% of CAs. Composites showed remarkable 72 % higher dynamic mechanical properties compared to neat epoxy. Thus, this study introduces new synthesis strategy for carbon composites with completely biobased anisotropic CAs as oriented and strong reinforcements.

CO2-free production of hydrogen via pyrolysis of natural gas: influence of non-methane hydrocarbons on product composition, methane conversion, hydrogen yield, and carbon capture

Methane pyrolysis represents a CO2-free hydrogen production route that enables simultaneous carbon capture. While the majority of previous studies in the field focus on pure CH4 as feed gas stream, commercial processes will typically rely on natural gas as feedstock that contains also non-methane hydrocarbons such as ethane, propane, and n-butane. Therefore, the present study evaluates how CH4 conversion, H2 selectivity, product composition, and solid carbon yield evolve when using either pure CH4 or synthetic natural gas (SNG) as feed gas stream for a thermal pyrolysis process in a lab-scale high-temperature reactor. For this, industrially viable conditions are applied, namely temperatures between 1000 °C and 1600 °C, residence times between 1 s and 7 s, and molar H2 dilution ratios between 1:1 and 4:1. Although the use of SNG results in slightly lower hydrocarbon conversions because the additional components in SNG result in a higher effective H2 dilution ratio compared to a CH4-only feed, the non-methane hydrocarbons in the SNG have a positive effect on both H2 selectivity and solid carbon yield. Taking existing mechanistic understanding into account, these positive effects are attributed to radicals formed from the non-methane hydrocarbons, which facilitate dehydrogenation steps from ethane to ethylene and hereby increase the relative amount of H2 originating from CH4. The introduction of a carbonaceous fixed bed further benefits the performance of the pyrolysis process and ultimately enables to capture more than 98% of carbon in its solid form under industrially viable process conditions.

Strength Retention of Carbon Fiber/Epoxy Vitrimer Composite Material for Primary Structures: Towards Recyclable and Reusable Carbon Fiber Composites

Recently, the growth of the recyclability of carbon fiber reinforced polymer (CFRP) composites has been driven by environmental and circular economic aspects. The main aim of this research work is to investigate the strength retention of a bio-based vitrimer composite reinforced with carbon fibers, which offers both recyclability and material reusability. The composite formulation consisted of an epoxy resin composed of diglycidyl ether of bioshpenol A (DGEBA) combined with tricarboxylic acid (citric acid, CA) and cardanol, which was then reinforced with carbon fibers to enhance its performance. Differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy were performed to analyze the chemical composition and curing behavior of the vitrimer. Mechanical testing under tensile loading at room temperature was carried out on epoxy, vitrimer, and associated carbon fiber reinforced composite materials. The results demonstrated that the DGEBA/CA/cardanol vitrimer exhibited thermomechanical properties comparable to those of an epoxy cured with petroleum-based curing agents. It was observed that the maximum tensile strength of vitrimer is about 50 MPa, which is very close to the range of epoxy resins cured with petroleum-based curing agents. Notably, the ability of the vitrimer composite to be effectively dissolved in a dimethylformamide (DMF) solvent is a significant advantage, as it enables the recovery of the fibers. The recovered carbon fiber retained comparable tensile strength to that of the fresh carbon composites. More than 95% strength was retained after the first recovery, which confirms the use of fibers for primary and secondary applications. These research results open up new avenues for efficient recycling and contribute to the overall sustainability of the composite material at an economic level.

Deep eutectic solvent-mediated synthesis of CuCo2O4 @ Sargassum tenerrimum derived carbon heterostructure as an efficient electrocatalyst for oxygen and hydrogen evolution reactions

Developing bifunctional electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) through simple, economical, and innovative methods is vital for sustainable energy conversion. Here, we showcase a green and sustainable approach for synthesizing CuCo₂O₄ - Sargassum Tenerrimum derived carbon composites (CCST) directly from fresh seaweed and a deep eutectic solvent (DES), marking its initial application in HER/OER. The successful transformation of seaweed and metal precursors into CCST was accomplished using a direct pyrolysis method at 900 °C in an inert atmosphere. Here, Seaweed granules acted as the carbon source, with DES employed for its multifunctional properties, including serving as a solvent, a structural template, and a catalyst for fostering material development. When these materials were assessed as electrocatalysts for OER in 1 M KOH media, the optimal catalyst (CCST-9 (1:2)) exhibited a low overpotential of 381 mV at 10 mA cm−2 with a Tafel slope of 44 mV dec−1. In addition, the same material achieved low overpotential of 383 mV at 10 mA cm−2 with a Tafel slope of 100 mV dec−1 when tested as an electrocatalyst for HER in 0.5 M H2SO4 media. Interestingly, CCST-9 (1:2) demonstrated excellent long-term stability in OER in 1 M KOH during a 24-h chronoamperometry test, with only a minor reduction in current density. The present study contributes new perspectives to the development of scalable and high-performance bifunctional catalysts, achieved through an environmentally friendly and cost-effective synthetic strategy.

Constraints on the continental weathering intensity through the Permian using lithium isotopes of well-preserved brachiopod shells

Lithium isotopic compositions (δ7Li) in marine carbonates provide a powerful means to track continental weathering intensity through geological history and promote our understanding of how and why Earth remained habitable. However, δ7Li values in ancient carbonates can be affected by factors such as primary carbonate mineralogy (e.g., aragonite, high-Mg calcite, low-Mg calcite) and post-depositional diagenesis, which may alter their primary signals. Modern articulate brachiopod shells have shown a constant δ7Li offset compared to contemporary seawater, suggesting that fossil brachiopod shells could serve as robust archives for this geochemical proxy due to their diagenetically resistant low-Mg calcite composition. Despite this potential, few studies have explored this topic. In this study, we analyze and compare the geochemical compositions of fossil brachiopod shells and their enclosing carbonate rocks from Permian strata in South China to investigate whether brachiopod shells can reliably preserve the δ7Li values of ancient seawater and, if they do, to obtain new constraints on changes in the continental weathering regimes through the Permian. We used several diagenetic screening methods, including scanning electron microscopy, cathodoluminescence microscopy, and elemental concentrations to detect potential diagenetic alteration. Our results indicate that 32 out of 49 shells preserve primary δ7Li values. Notably, we observed that δ7Li offsets between brachiopod shells and their enclosing carbonate rocks vary across the studied sections, likely due to diagenetic alteration of the bulk carbonates. Using the δ7Li values from well-preserved brachiopod shells, we reconstructed δ7Li variations of Permian seawater. We identified three distinct intervals: (1) extremely low δ7Lisw values (as low as 6.7 ± 2.9‰, n = 12, 1sd) during the Asselian and Sakmarian stages, (2) high δ7Lisw values (32.6 ± 4.5‰, n = 3, 1sd) similar to modern seawater during the Kungurian stage, and (3) relatively low δ7Lisw values (13.6 ± 3.9‰, n = 14, 1sd) from the Capitanian to the Changhsingian stages. These significant changes in δ7Li values of Permian seawater indicate dramatic changes in continental weathering regimes during the Permian, possibly linked to major climate changes, such as the termination of the Late Paleozoic Ice Age and warming associated with the emplacement of the large igneous provinces.

Variation of carbon and nitrogen stable isotope composition in leaves and roots of Littorella uniflora (L.) Asch. in relation to water pH and nutrient availability

In a phytotron experiment, the effects of pH variation and eutrophication on isoetids plants from soft-water lakes specifically the submerged form of Littorella uniflora (L.) Asch. was investigated by analyzing stable carbon and nitrogen isotopes (δ13C and δ15N). Conducted in late October 2020, 200 specimens from Lake Zawiad, near Gdansk, Poland, were examined over 75 days. The study tested three pH levels (∼4.5, ∼7.0, and ∼8.5) and a detailed 12-step nutrient gradient (nitrogen: 0–10 mg/l; phosphorus: 0–0.3 mg/l). The analysis focused on isotopic composition in leaves and roots, revealing that acidic conditions favored higher δ13C values (leaves: −22.67 ‰; roots: −23.23 ‰), suggesting a preference for lighter carbon forms in photosynthesis and intensive use of limited sources of CO2. The neutral pH variant showed the lowest δ13C values (leaves: −25.53 ‰; roots: −25.47 ‰), indicating less optimal conditions. δ15N values exhibited minimal fluctuation across pH levels, with slight variations in acidic and alkaline environments compared to neutral conditions. An observed decrease in δ13C across all pH levels with increased nutrients, alongside a rise in δ15N values, indicates a complex interaction between isotopic composition and environmental factors. Our findings suggest that L. uniflora shows a distinct isotopic response to varying pH levels, with higher δ13C values under acidic conditions potentially indicating enhanced CO2 uptake through a specialized carbon assimilation strategy. This highlights the species' adaptive mechanisms to environmental stressors, suggesting that the isotopic composition of aquatic vegetation can serve as a sensitive indicator of changes in lake ecosystems.

Regional differences in soil stable isotopes and vibrational features at depth in three California grasslands

There are major gaps in our understanding of how Mediterranean ecosystems will respond to anticipated changes in precipitation. In particular, limited data exists on the response of deep soil carbon dynamics to changes in climate. In this study we wanted to examine carbon and nitrogen dynamics between topsoils and subsoils along a precipitation gradient of California grasslands. We focused on organic matter composition across three California grassland sites, from a dry and hot regime (~ 300 mm precipitation; MAT: 14.6 ∘C) to a wet, cool regime (~ 2160 mm precipitation/year; MAT: 11.7 ∘C). We determined changes in total elemental concentrations of soil carbon and nitrogen, stable isotope composition (δ13C, δ15N), and composition of soil organic matter (SOM) as measured through Diffuse Reflectance Infrared Fourier Transformed Spectroscopy (DRIFTS) to 1 m soil depth. We measured carbon persistence in soil organic matter (SOM) based on beta (β), a parameter based on the slope of carbon isotope composition across depth and proxy for turnover. Further, we examined the relationship between δ15N and C:N values to infer SOM’s degree of microbial processing. As expected, we measured the greatest carbon stock at the surface of our wettest site, but carbon stocks in subsoils converged at Angelo and Sedgwick, the wettest and driest sites, respectively. Soils at depth (> 30 cm) at the wettest site, Angelo, had the lowest C:N and highest δ15N values with the greatest proportion of simple plant-derived organic matter according to DRIFTS. These results suggest differing stabilization mechanisms of organic matter at depth across our study sites. We infer that the greatest stability was conferred by associations with reactive minerals at depth in our wettest site. In contrast, organic matter at our driest site, Sedgwick, was subject to the most microbial processing. Results from this study demonstrate that precipitation patterns have important implications for deep soil carbon storage, composition, and stability.