Molecular signatures of dissolved organic matter in a tropical karst system

Karst areas are widespread landforms present on all continents, formed by the dissolution of carbonate or evaporite host rock. Little is known about the composition and nature of dissolved organic matter (DOM) as it moves through karst systems, although karst DOM has been recognized as important for a range of natural processes. Microbial communities living in karst systems are some of the most diverse and intriguing on the planet, and their metabolism and life cycle can give clues related to the development of a host of different life forms. Karst areas are also of interest due to their mostly subterranean hydrology, and the repercussions of these processes on local carbon cycles. We illustrate some of the processes acting on DOM in karst waters through the analysis of soil, drip and cave pool waters at the tropical site of Yok Balum Cave, in southern Belize. Water samples were analyzed using ultra-high resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FT-ICR-MS), a technique that enables the resolution of single molecular formulae within a DOM spectrum. We perform multivariate statistics to detect trends in the data and identify provenance of detected molecular components. In addition to karst waters, four aliquots of a powdered stalagmite sample from the same cave system are analyzed. Our results show a clear gradient between the soil and the cave system. We hypothesize that both sorption on mineral surfaces and microbial reworking are responsible for the observed trend in DOM composition. The stalagmite extracts show an anomalous DOM pattern, which may be due to a variety of factors, including microbial activity on the stalagmite surface and different affinities of compounds to incorporation in the carbonate. The goal of this study was to follow the molecular transformations of DOM on its journey from the surface to the cave, and to provide a molecular basis for the establishment of stalagmite DOM proxies in karst systems

Speleothem evidence for Late Miocene extreme Arctic amplification – an analogue for near-future anthropogenic climate change?

The Miocene provides an excellent climatic analogue for near-future runaway anthropogenic warming, with atmospheric CO2 concentrations and global average temperatures similar to those projected for the coming century under extreme-emissions scenarios. However, the magnitude of Miocene Arctic warming remains unclear due to the scarcity of reliable proxy data. Here we use stable oxygen isotope and trace element analyses, alongside clumped isotope and fluid inclusion palaeothermometry of speleothems to reconstruct palaeo-environmental conditions near the Siberian Arctic coast during the Tortonian (8.68 ± 0.09 Ma). Stable oxygen isotope records suggest warmer-than-present temperatures. This is supported by temperature estimates based on clumped isotopes and fluid inclusions giving mean annual air temperatures between +6.6 and +11.1 °C, compared with −12.3 °C today. Trace elements records reveal a highly seasonal hydrological environment. Our estimate of &gt; 18 °C of Arctic warming supports the wider consensus of a warmer-than-present Miocene and provides a rare palaeo-analogue for future Arctic amplification under high-emissions scenarios. The reconstructed increase in mean surface temperature far exceeds temperatures projected in fully coupled global climate models, even under extreme-emissions scenarios. Given that climate models have consistently underestimated the extent of recent Arctic amplification, our proxy data suggest Arctic warming may exceed current projections.</p

Evaluating model outputs using integrated global speleothem records of climate change since the last glacial

Although quantitative isotope data from speleothems has been used to evaluate isotope-enabled model simulations, currently no consensus exists regarding the most appropriate methodology through which to achieve this. A number of modelling groups will be running isotope-enabled palaeoclimate simulations in the framework of the Coupled Model Intercomparison Project Phase 6, so it is timely to evaluate different approaches to using the speleothem data for data–model comparisons. Here, we illustrate this using 456 globally distributed speleothem δ18O records from an updated version of the Speleothem Isotopes Synthesis and Analysis (SISAL) database and palaeoclimate simulations generated using the ECHAM5-wiso isotope-enabled atmospheric circulation model. We show that the SISAL records reproduce the first-order spatial patterns of isotopic variability in the modern day, strongly supporting the application of this dataset for evaluating model-derived isotope variability into the past. However, the discontinuous nature of many speleothem records complicates the process of procuring large numbers of records if data–model comparisons are made using the traditional approach of comparing anomalies between a control period and a given palaeoclimate experiment. To circumvent this issue, we illustrate techniques through which the absolute isotope values during any time period could be used for model evaluation. Specifically, we show that speleothem isotope records allow an assessment of a model's ability to simulate spatial isotopic trends. Our analyses provide a protocol for using speleothem isotope data for model evaluation, including screening the observations to take into account the impact of speleothem mineralogy on δ18O values, the optimum period for the modern observational baseline and the selection of an appropriate time window for creating means of the isotope data for palaeo-time-slices

O-Glycosylation Regulates Ubiquitination and Degradation of the Anti-Inflammatory Protein A20 to Accelerate Atherosclerosis in Diabetic ApoE-Null Mice

Background: Accelerated atherosclerosis is the leading cause of morbidity and mortality in diabetic patients. Hyperglycemia is a recognized independent risk factor for heightened atherogenesis in diabetes mellitus (DM). However, our understanding of the mechanisms underlying glucose damage to the vasculature remains incomplete. Methodology/Principal Findings: High glucose and hyperglycemia reduced upregulation of the NF-κB inhibitory and atheroprotective protein A20 in human coronary endothelial (EC) and smooth muscle cell (SMC) cultures challenged with Tumor Necrosis Factor alpha (TNF), aortae of diabetic mice following Lipopolysaccharide (LPS) injection used as an inflammatory insult and in failed vein-grafts of diabetic patients. Decreased vascular expression of A20 did not relate to defective transcription, as A20 mRNA levels were similar or even higher in EC/SMC cultured in high glucose, in vessels of diabetic C57BL/6 and FBV/N mice, and in failed vein grafts of diabetic patients, when compared to controls. Rather, decreased A20 expression correlated with post-translational O-Glucosamine-N-Acetylation (O-GlcNAcylation) and ubiquitination of A20, targeting it for proteasomal degradation. Restoring A20 levels by inhibiting O-GlcNAcylation, blocking proteasome activity, or overexpressing A20, blocked upregulation of the receptor for advanced glycation end-products (RAGE) and phosphorylation of PKCβII, two prime atherogenic signals triggered by high glucose in EC/SMC. A20 gene transfer to the aortic arch of diabetic ApoE null mice that develop accelerated atherosclerosis, attenuated vascular expression of RAGE and phospho-PKCβII, significantly reducing atherosclerosis. Conclusions: High glucose/hyperglycemia regulate vascular A20 expression via O-GlcNAcylation-dependent ubiquitination and proteasomal degradation. This could be key to the pathogenesis of accelerated atherosclerosis in diabetes

[Dataset] SISALv3: A global speleothem stable isotope and trace element database

All trace elements are reported normalized as ratios with respect to Ca (, where X stands for the individual elements) in units of millimoles per mole. In the following paper, “trace element” refers to the normalized ratio to Ca. A standardized conversion sheet is used to facilitate conversions from grams to moles (available in the repository). Sr-isotope data are reported as values. For internal consistency and to facilitate future intercomparison and synthesis studies, the measurement method and reference materials used as well as the measurement precision are also reported for both trace elements and Sr isotopes.Palaeoclimate information on multiple climate variables at different spatiotemporal scales is becoming increasingly important to understand environmental and societal responses to climate change. A lack of high-quality reconstructions of past hydroclimate has recently been identified as a critical research gap. Speleothems, with their precise chronologies, widespread distribution, and ability to record changes in local to regional hydroclimate variability, are an ideal source of such information. Here, we present a new version of the Speleothem Isotopes Synthesis and AnaLysis database (SISALv3), which has been expanded to include trace element ratios and Sr isotopes as additional, hydroclimate-sensitive geochemical proxies. The oxygen and carbon isotope data included in previous versions of the database have been substantially expanded. SISALv3 contains speleothem data from 365 sites from across the globe, including 95 Mg/Ca, 85 Sr/Ca, 52 Ba/Ca, 25 U/Ca, 29 P/Ca, and 14 Sr-isotope records. The database also has increased spatiotemporal coverage for stable oxygen (892) and carbon (620) isotope records compared with SISALv2 (which consists of 673 and 430 stable oxygen and carbon records, respectively). Additional meta information has been added to improve the machine-readability and filtering of data. Standardized chronologies are included for all new entities along with the originally published chronologies. Thus, the SISALv3 database constitutes a unique resource of speleothem palaeoclimate information that allows regional to global palaeoclimate analyses based on multiple geochemical proxies, permitting more robust interpretations of past hydroclimate and comparisons with isotope-enabled climate models and other Earth system and hydrological models. The database can be accessed at 10.5287/ora-2nanwp4rk (Kaushal et al., 2024).Peer reviewe

Chemisches Recycling von gemischten Kunststoffabfällen als ergänzender Recyclingpfad zur Erhöhung der Recyclingquote

Zusammenfassung Kunststoffabfälle, speziell Verpackungsabfälle, liegen oft als Gemische mit hohem Verschmutzungsgrad vor. Die werkstoffliche Verwertung wird dadurch enorm erschwert, da die Sortierung und Reinigung dieser Fraktionen in vielen Fällen nicht ökonomisch sinnvoll oder technisch umsetzbar sind. Um diese Materialströme dennoch rohstofflich rezyklieren zu können, bietet das chemische Recycling eine vielversprechende Methode durch die Rückgewinnung von Einsatzstoffen für die Kunst- und Kraftstoffproduktion sowie für die petrochemische Industrie. Durch das Einwirken von Wärme, Katalysatoren und Lösungsmitteln werden dabei die Polymerketten in kürzere Einheiten bis hin zu Monomeren aufgespalten. Die dabei gewonnenen Kohlenwasserstoffe können dem Stoffkreislauf erneut zugeführt werden, um primäre Ressourcen zu ersetzen. Diese Technologien weisen eine hohe Toleranz gegenüber Störstoffen und Sortenunreinheiten auf und sind deshalb besonders attraktive Optionen für die Verwertung von verunreinigten Verpackungsabfällen. In den letzten 40 Jahren wurden hierzu verschiedene Ansätze zur Solvolyse und Pyrolyse mit und ohne Katalysator verfolgt, die zugrunde liegenden Mechanismen untersucht sowie zahlreiche Reaktorsysteme und Prozesswege entwickelt. Ein Überblick über die chemischen Grundlagen, die entwickelten Verfahren und deren Werdegang gibt Aufschluss über die Chancen und Problematiken des Feedstockrecyclings als ergänzende Maßnahme zum werkstofflichen Recycling. Weiters werden die neuesten Forschungs- und Entwicklungsaktivitäten dargestellt, um den heutigen Entwicklungsstand und zukünftige Trends abzubilden und aufzuzeigen, dass das chemische Recycling eine potente Option zur Rückgewinnung von Rohstoffen und Schonung von Ressourcen darstellt.</jats:p