Borosilicate glasses are the favored material for immobilization of high-level nuclear waste (HLW) from the reprocessing of spent fuel used in nuclear power plants. To assess the long-term stability of nuclear waste glasses, it is crucial to understand how self-irradiation affects the structural state of the glass and influences its dissolution behavior. In this study, we focus on the effect of heavy ion irradiation on the forward dissolution rate of a non-radioactive ternary borosilicate glass. To create extended radiation defects, the glass was subjected to heavy ion irradiation using 197Au ions that penetrated ~50 µm deep into the glass. The structural damage was characterized by Raman spectroscopy, revealing a significant depolymerization of the silicate and borate network in the irradiated glass and a reduction of the average boron coordination number. Real time, in situ fluid-cell Raman spectroscopic corrosion experiments were performed with the irradiated glass in a silica-undersaturated, 0.5 M NaHCO3 solution at temperatures between 80 and 85 °C (initial pH = 7.1). The time- and space-resolved in situ Raman data revealed a 3.7 ± 0.5 times increased forward dissolution rate for the irradiated glass compared to the non-irradiated glass, demonstrating a significant impact of irradiation-induced structural damage on the dissolution kinetics.
Fossilization processes and especially the role of bacterial activity during the preservation of organic material has not yet been well understood. Here, we report the results of controlled taphonomic experiments with crayfish in freshwater and sediment. 16S rRNA amplicon analyzes showed that the development of the bacterial community composition over time was correlated with different stages of decay and preservation. Three dominating genera, Aeromonas, Clostridium and Acetobacteroides were identified as the main drivers in the decomposition of crayfish in freshwater. Using micro-computed tomography (µ-CT), scanning electron microscopy (SEM) and confocal Raman spectroscopy (CRS), calcite clusters were detected after 3–4 days inside crayfish carcasses during their decomposition in freshwater at 24 °C. The precipitation of calcite clusters during the decomposition process was increased in the presence of the bacterial genus Proteocatella. Consequently, Proteocatella might be one of the bacterial genera responsible for fossilization.
The evolutionary history of latex, a widespread chemical defense against insect herbivores, is not fully understood, yet a more detailed understanding of the fossil record of latex could help answer important evolutionary questions. This is, however, hampered by the difficulty of recognizing fossil latex and our still incomplete comprehension of the processes preserving latex. The best-studied fossil latex comes from the middle Eocene Geiseltal lignites in Germany, where fibrous laticifer mats, called “monkeyhair,” are preserved in the severely degraded remains of some ancient trees in the brown coals. Laticifers are specialized elongate cells that carry latex throughout the plant. In previous studies, researchers have hypothesized that these fossil laticifers are preserved through natural low temperature vulcanization of rubber within the latex. Here, we report the results of Raman spectroscopic study on Geiseltal laticifers to identify the vulcanization of natural rubber and on spatially associated carbonaceous material to test various Raman carbon geothermometers for their accuracy for low-thermal-maturity samples. Raman spectra of the fossil laticifers are virtually identical to that of rubber (cis-1,4-polyisoprene) with additional bands demonstrating sulfur vulcanization. Raman spectra from the surrounding lignite and existing Raman-based carbon thermometers, currently calibrated down to about 100 °C, clearly indicate that these samples were never exposed to temperatures higher than the surrounding lignite. These results directly validate the previous hypothesis of fossilization through natural vulcanization. Moreover, this work demonstrates that Raman spectroscopy is a rapid, non-destructive method for reliably identifying and characterizing fossil latex and that further development and calibration of the carbon thermometer may allow quantitative temperature measurements for low-thermal-maturity carbonaceous material.
Fossilized tree resin, or amber, commonly contains fossils of animals, plants and microorganisms. These inclusions have generally been interpreted as hollow moulds or mummified remains coated or filled with carbonaceous material. Here, we provide the first report of calcified and silicified insects in amber from the mid‐Cretaceous Kachin (Burmese) amber. Data from light microscopy, scanning electron microscopy (SEM), energy‐dispersive and wavelength‐dispersive X‐ray spectroscopy (EDX and WDX), X‐ray micro‐computed tomography (Micro‐CT) and Raman spectroscopy show that these Kachin fossils owe their preservation to multiple diagenetic mineralization processes. The labile tissues (e.g. eyes, wings and trachea) mainly consist of calcite, chalcedony and quartz with minor amounts of carbonaceous material, pyrite, iron oxide and phyllosilicate minerals. Calcite, quartz and chalcedony also occur in cracks as void‐filling cements, indicating that the minerals formed from chemical species that entered the fossil inclusions through cracks in the resin. The results demonstrate that resin and amber are not always closed systems. Fluids (e.g. sediment pore water, diagenetic fluid and ground water) at different burial stages have chances to interact with amber throughout its geological history and affect the preservational quality and morphological fidelity of its fossil inclusions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.