Biogenic carbonate mercury and marine temperature records reveal global influence of Late Cretaceous Deccan Traps

High-Performance Single-Crystal Lithium-Rich Layered Oxides Cathode Materials via Na2WO4-Assisted Sintering

Single-crystal lithium-rich layered oxides (LLOs) with excellent mechanical properties can enhance their crystal structure stability. However, the conventional methods for preparing single-crystal LLOs, require large amounts of molten salt additives, involve complicated washing steps, and increase the difficulty of large-scale production. In this study, a sodium tungstate (Na2WO4)-assisted sintering method is proposed to fabricate high-performance single-crystal LLOs cathode materials without large amounts of additives and additional washing steps. During the sintering process, Na2WO4 promotes particle growth and forms a protective coating on the surface of LLOs particles, effectively suppressing the side reactions at the cathode/electrolyte interface. Additionally, trace amounts of Na and W atoms are doped into the LLOs lattice via gradient doping. Experimental results and theoretical calculations indicate that Na and W doping stabilizes the crystal structure and enhances the Li+ ions diffusion rate. The prepared single-crystal LLOs exhibit outstanding capacity retention of 82.7% (compared to 65.0%, after 200 cycles at 1 C) and a low voltage decay rate of 0.76 mV per cycle (compared to 1.80 mV per cycle). This strategy provides a novel pathway for designing the next-generation high-performance cathode materials for Lithium-ion batteries (LIBs).

Carbon reservoir perturbations induced by Deccan volcanism: Stable isotope and biomolecular perspectives from shallow marine environment in Eastern India

The Deccan Traps in Western India is hypothesized to have caused significant fluctuations in climatic condition and organic matter (OM) productivity across the Cretaceous-Paleogene Boundary (K/PgB). The periodic release of large amounts of volatiles into the atmosphere is thought to drive these changes. Yet, direct impact of volcanism on the carbon cycle and ecosystem remains relatively unconstrained. For the first time, we attempt to trace changes in both marine and terrestrial carbon reservoirs from pre- and intervolcanic sedimentary units (infra- and inter-trappeans respectively) from Rajahmundry, ~1500 km SE of main eruption sites in Western India. Molecular level characterization of OM and stable isotope composition of carbonates (δ¹³ C_carb ), bulk OM (δ¹³ C_org ), and n-alkane (δ¹³ C_alk and δD_alk ) have been analysed to provide a chemo-stratigraphic framework. In Rajahmundry, high CO₂ concentration estimated from infra-trappean carbonate nodule is synchronous with the onset of the Deccan Traps and the Late Maastrichtian warming episode. Impact of the warming event is reflected in Rajahmundry from a major shift in the terrestrial ecosystem. Marine OM production also seems to have been low throughout the infra-trappean. A steady decrease in δ¹³ C_carb values, increase in mortality rates and dwarfism in invertebrates immediately below the first volcanic units in Rajahmundry suggest stressed conditions from eruption in the western part of India ~40-60 kyrs prior to K/PgB. A significant increase in heterotrophic activity is observed after the volcanic deposits in Rajahmundry that seems to have controlled the marine carbon reservoir for a maximum of ~200 kyrs after the boundary. Advent of pteridophytes, increase in carbon content and positive shifts in δ¹³ C_carb and δ¹³ C_alk values in the upper inter-trappean units mark the onset of recovery in terrestrial and marine environments. Overall, our results suggest significant perturbations in the carbon reservoir as a consequence of the Deccan eruption.

Coprecipitation of Mercury from Natural Iodine-Containing Seawater for Accurate Isotope Measurement

Oceans play a key role in the global mercury (Hg) cycle, but studies on Hg isotopes in seawater are rare due to the extremely low Hg concentration and the lack of a good preconcentration method. Here, we introduce a new coprecipitation method for separating and preconcentrating Hg from seawater for accurate isotope measurement. The coprecipitation was achieved by sequential addition of 0.5 mL of 0.5 M CuSO₄, 1 mL of 0.5 M Na₂S, and 1 mL of 0.5 M CuSO₄ reagents, which allowed for quantitatively precipitating Hg from up to 10 L of seawater. The protocol was validated by testing synthetic solutions with varying Hg and iodide (I^-) concentrations and by comparing the reaction times of various reagents added. The method resulted in a quantitative recovery of 98 ± 12% (n = 32, two standard deviations, 2 SD) and a relatively low procedure blank (103 pg of Hg, n = 8). The precipitates were filtrated and analyzed for Hg isotopes. Repeated measurements of synthetic seawaters spiked with certificated standard materials (NIST 3133 and 3177) using the entire method gave identical Hg isotope ratios with near-quantitative Hg recovery, indicating no isotope fractionation during preconcentration. A total of six nearshore seawater samples from the Yellow Sea and the Bohai Sea (China) were analyzed using the coprecipitation method. The data showed a large fractionation of Hg isotopes and revealed the possible impact of both atmospheric and anthropogenic inputs to the coastal seawater Hg budget, implying the potential application of this method in studying marine Hg systematics and global Hg cycling.

Reconciling early Deccan Traps CO2 outgassing and pre-KPB global climate

A 2 to 4 °C warming episode, known as the Latest Maastrichtian warming event (LMWE), preceded the Cretaceous-Paleogene boundary (KPB) mass extinction at 66.05 ± 0.08 Ma and has been linked with the onset of voluminous Deccan Traps volcanism. Here, we use direct measurements of melt-inclusion CO2 concentrations and trace-element proxies for CO2 to test the hypothesis that early Deccan magmatism triggered this warming interval. We report CO2 concentrations from NanoSIMS and Raman spectroscopic analyses of melt-inclusion glass and vapor bubbles hosted in magnesian olivines from pre-KPB Deccan primitive basalts. Reconstructed melt-inclusion CO2 concentrations range up to 0.23 to 1.2 wt% CO2 for lavas from the Saurashtra Peninsula and the Thakurvadi Formation in the Western Ghats region. Trace-element proxies for CO2 concentration (Ba and Nb) yield estimates of initial melt concentrations of 0.4 to 1.3 wt% CO2 prior to degassing. Our data imply carbon saturation and degassing of Deccan magmas initiated at high pressures near the Moho or in the lower crust. Furthermore, we find that the earliest Deccan magmas were more CO2 rich, which we hypothesize facilitated more efficient flushing and outgassing from intrusive magmas. Based on carbon cycle modeling and estimates of preserved lava volumes for pre-KPB lavas, we find that volcanic CO2 outgassing alone remains insufficient to account for the magnitude of the observed latest Maastrichtian warming. However, accounting for intrusive outgassing can reconcile early carbon-rich Deccan Traps outgassing with observed changes in climate and atmospheric pCO2.

Foamy oysters: vesicular microstructure production in the Gryphaeidae via emulsification

The vesicular microstructure is a very distinctive arrangement of calcite, consisting of hollow cavities (vesicles) of diverse sizes and shapes, usually elongated in the direction of shell thickening. It is uniquely found among living bivalves in a single oyster family, Gryphaeidae. The vesicles are distributed in lenses interleaved with compact foliated layers. We have studied the morphology and distribution of vesicles within the lenses using optical and electron microscopy, and micro-computed tomography. At a small scale, vesicles do not follow a classical von Neumann-Mullins route typical of ideal foams. At a larger scale, the initiation and evolution of a vesicular layer statistically proceed like a foam, with vesicles becoming more numerous, larger and more even in size. In summary, the vesicular material follows a foam-like coarsening to reduce the number of energetically costly interfaces. However, a steady state is never reached because the animal permanently introduces energy in the system by creating new vesicles. The fabrication of the vesicular material is mediated by the production of an emulsion between the extrapallial fluid and the precursor PILP of the calcitic walls within the thin extrapallial space. For this mechanism to proceed, the mantle cells must perform highly sophisticated behaviours of contact recognition and secretion. Accordingly, the vesicular material is under mixed physical-biological control.