Depositional environment of the Upper Cretaceous oil shales in the Negev Desert, Israel: Geochemical constraints based on trace elements and stable isotopes

A study in inorganic geochemistry from the Campanian (Mishash Formation) - Maastrichtian (Ghareb Formation) transition of southern Israel was done to provide insights into the inference of foraminiferal assemblages, water column-oxygen levels, trace metal enrichment on a high-productivity seafloor. A series of high-resolution approaches in inorganic geochemistry applied on a 50 m sequence in the Efe`s syncline of the Negev desert. A conceptual model of the deposition history was developed

Geochemical evidence for the link between sulfate reduction, sulfide oxidation and phosphate accumulation in a late cretaceous upwelling system

Background: On Late Cretaceous Tethyan upwelling sediments from the Mishash/Ghareb Formation (Negev, Israel),bulk geochemical and biomarker analyses were performed to explain the high proportion of phosphates in thelower part and of organic matter (OM) preserved in upper parts of the studied section. The profile is composed ofthree facies types; the underlying Phosphate Member (PM), the Oil Shale Member (OSM) and the overlying MarlMember (MM). Results: Total organic carbon (TOC) contents are highly variable over the whole profile reaching from 0.6% in theMM, to 24.5% in the OSM. Total iron (TFe) varies from 0.1% in the PM to 3.3% in the OSM. Total sulfur (TS) rangesbetween 0.1% in the MM and 3.4% in the OSM, resulting in a high C/S ratio of 6.5 in the OSM section. A meanproportion of 11.5% total phosphorus (TP) in the PM changed abruptly with the facies to a mean value of only 0.9% in the OSM and the MM. The TOC/TOC$_{OR}$ ratios argue for a high bacterial sulfate reduction activity and in addition, results from fatty acidanalyses indicate that the activity of sulfide-oxidizing activity of bacteria was high during deposition of the PM,while decreasing during the deposition of the OSM. Conclusions: The upwelling conditions effected a high primary productivity and consequently the presence of abundant OM. This, in combination with high sulfate availability in the sediments of the PM resulted in a higher sulfide production due to the activity of sulfate-reducing bacteria. Iron availability was a limiting factor during the deposition of the whole section, affecting the incorporation of S into OM. This resulted in the preservation of a substantial part of OM against microbial degradation due to naturally-occurring sulfurization processes expressed by the high C/S ratio of 6.5 in the OSM. Further, the abundant sulfide in the pore water supported the growth of sulfide-oxidizing bacteria promoting the deposition of P, which amounted to as much as 15% in the PM. These conditions changed drastically from the PM to the OSM, resulting in a significant reduction of the apatite precipitation and a high concentration of reactive S species reacting with the OM

Chronology with a pinch of salt:Integrated stratigraphy of Messinian evaporites in the deep Eastern Mediterranean reveals long-lasting halite deposition during Atlantic connectivity

The Messinian Salinity Crisis (MSC; 5.97–5.33 Ma) is considered an extreme environmental event driven by changes in climate and tectonics, which affected global ocean salinity and shaped the biogeochemical composition of the Mediterranean Sea. Yet, after more than 50 years of research, MSC stratigraphy remains controversial. Recent studies agree that the transition from the underlying pre-evaporite sediments to thick halite deposits is conformal in the deep Eastern Mediterranean Basin. However, the age of the base and the duration of halite deposition are still unclear. Also disputed is the nature of the intermediate and upper MSC units, which are characterized as periods of increased clastic deposition into the Eastern Mediterranean based on marginal outcrops and seismic data. We provide a multidisciplinary study of sedimentary, geochemical, and geophysical data from industrial offshore wells in the Levant Basin, which recovered a sedimentary record of deep-basin Mediterranean evaporites deposited during the MSC. In combination with previous observations of the MSC throughout the Mediterranean Basin, our results promote the need for a new chronological model. Remarkably, the one-kilometer-thick lower part of the evaporitic unit is composed of essentially pure halite, except for a thin transitional anhydrite layer at its base. The halite is undisturbed and homogeneous, lacking diverse features apparent in more proximal sections, indicating a deep-sea depositional environment. We find that distinct, meters-thick non-evaporitic intervals interbedded with the halite, previously thought to be clastic layers, are diatomites. While XRD analysis confirms an increase in clastic components in these sediments, they are composed primarily of well-preserved marine and freshwater planktonic diatoms. The occurrence of marine planktonic diatoms in these intervals indicates the input of Atlantic waters into the Mediterranean Basin during the deposition of the massive halite unit. Seismic stratigraphy and well-log cyclostratigraphy further support deep basin halite deposition, which started about 300 kyr earlier than widely assumed (~5.97 Ma). We propose that halite deposition in the deep Mediterranean took place during stage 1 of the MSC, rather than being limited to the short 50 kyr MSC acme when sea level was presumably at its lowest. Thus, brine formation, salt precipitation, and faunal extinction occurred at least in part in a deep, non-desiccated basin, with a restricted yet open Mediterranean-Atlantic connection that allowed inflow of oceanic water. We observe an increase in heavy minerals and reworked fauna within the clastic-evaporitic, Interbedded Evaporites of the basinal MSC section, and argue that these settings correspond in the deep basins with a significant sea-level drawdown during stage 2 of the MSC, as observed in the marginal sections. This correlation is corroborated by astrochronology and chemostratigraphic markers, such as the distribution of n-alkanes and biomarker-based thermal maturity indices. The Levant deposits indicate that high sea level and partial connectivity with global oceans promoted the deposition of deep-basin deep-water halite, while sea-level drawdown promoted deposition of reworked and transported material from the margins into deep Mediterranean basins. This study modifies the current understanding of the mechanisms governing salt deposition throughout the MSC with implications for other evaporitic events in the geologic record

On the number of signals in multivariate time series

We assume a second-order source separation model where the observed multivariate time series is a linear mixture of latent, temporally uncorrelated time series with some components pure white noise. To avoid the modelling of noise, we extract the non-noise latent components using some standard method, allowing the modelling of the extracted univariate time series individually. An important question is the determination of which of the latent components are of interest in modelling and which can be considered as noise. Bootstrap-based methods have recently been used in determining the latent dimension in various methods of unsupervised and supervised dimension reduction and we propose a set of similar estimation strategies for second-order stationary time series. Simulation studies and a sound wave example are used to show the method's effectiveness

Untersuchung anorganischer Reaktionsmechanismen in ionischen Flüssigkeiten

In this study, the possibility to perform detailed kinetic and mechanistic studies in ionic liquids was investigated. Fundamental studies of ionic liquid properties and their behaviour under variation of temperature and pressure were performed, as well as the influence of ion-pair interactions in ionic liquids and their implication on dissolved substrates and the IL properties, were determined. Furthermore, the influence of different ionic liquids on the reaction rate and mechanism of a nucleophilic substitution reaction in two different model systems was investigated. In Chapter 2, purification procedures for the two examined ionic liquids are described and enable UV-vis spectroscopic investigation of reactions in these ionic liquids. The resulting ionic liquids showed only negligible absorbance in the UV region down to a wavelength of 250 nm. To check the intermolecular forces between the cations and anions of the ionic liquids, NMR-measurements of pure samples of several different liquids were performed. The nature of the counter ion seemed to have a major influence on the cation-anion interaction. The difference in the interactions between the ion-pairs seem to be of great importance, as dissolved substrates can also be influenced by these. In Chapter 3, the influence of ionic liquids on a model complex system was studied. The reaction of the selected Pt(II) complex showed several variations from its conventional behaviour. The reaction with thiourea was decelerated significantly by at least a factor of 6, up to a factor of 240, compared to the reaction in water or methanol, depending on the ionic liquid used. The determined second order rate constants measured in the ionic liquids showed significant changes depending on the ionic liquid anion. With the nucleophile thiocyanate, the rate constants differed by a factor of over 2000, thus pointing to significant differences between the solvents. In Chapter 4, the model complex system was modified by replacing the central Pt(II) by Pd(II) to increase the lability of the complex system and thus the reaction rate. The reaction with thiourea in [emim][NTf2] was accelerated by a factor of 500 compared to the Pt(II) analogue, leading to kobs values of up to 127 s-1, reaching the actual limit of stopped-flow measurements in ionic liquids with the experimental set-up used. The reaction with thiourea proceeded via an associative or associative interchange mechanism, as expected. This was also the case in the ionic liquid [emim][EtOSO3], where the reaction was accelerated by a factor of 100 compared to the Pt(II) analogue. The reactions with charged nucleophiles showed a different behaviour and proceeded via the establishment of a pre-equilibrium in [emim][NTf2]. In [emim][EtOSO3] the reaction with thiocyanate was much slower and the concentration dependence showed, in contrast to the results in the other ionic liquid, a linear behaviour and a significant intercept. In Chapter 5, the possible binding of the [NTf2]- anion to the labile Pd(II) centre in [Pd(II)(ppp)Cl]+ was studied, as this could interfere with the kinetic investigations and lead to unwanted side reactions. From several different preparation procedures three different crystals were isolated for which X-ray crystal structures could be determined. This work clearly demonstrates the possibility of mechanistic investigations in ionic liquids. The ILs turned out to behave as normal solvents in some aspects, like the temperature or pressure dependent changes of some properties as polarity. Other aspects like the strong cation-anion interactions turned out to distinguish this new class of liquids from molecular solvents. The ion-pair interactions of ILs can, as this work demonstrated, influence reactions incorporating metal complexes and drastically change the rate of such reactions. For industrial applications, exact knowledge of these effects can help to select the most appropriate ionic liquid for a certain catalytic reaction.In der vorliegenden Arbeit wurde die Durchführbarkeit detaillierter kinetischer und mechanistischer Untersuchungen in ionischen Flüssigkeiten überprüft. Neben grundlegenden Analysen der Eigenschaften ionischer Flüssigkeiten und deren Modifikation bei Druck- und Temperaturvariation, wurden des weiteren die Auswirkungen der Wechselwirkungen zwischen den Ionenpaaren auf gelöste Substrate und einige Eigenschaften der ionischen Flüssigkeiten ermittelt. Darüber hinaus wurde der Einfluss verschiedener ionischer Flüssigkeiten auf Reaktionsgeschwindigkeit und Mechanismus einer nukleophilen Substitutionsreaktion anhand zweier Modell-Katalysatorsysteme betrachtet. In Kapitel 2 werden Konzepte zur Aufreinigung der zwei untersuchten ionischen Flüssigkeiten aufgezeigt, durch deren Anwendung eine spektroskopische Untersuchung mit UV-vis-Spektroskopie ermöglicht wurde. Die so gewonnenen ionischen Flüssigkeiten wiesen nur vernachlässigbare Absorption innerhalb des UV-Bereiches oberhalb einer Wellenlänge von 250 nm auf. Zur Ermittlung der intermolekularen Kräfte zwischen den Kationen und Anionen der ionischen Flüssigkeit wurden NMR-spektroskopische Messungen an reinen Proben verschiedener Flüssigkeiten durchgeführt. Die unterschiedliche Stärke der Wechselwirkung zwischen den Ionen kann große Auswirkungen haben, da auch in ionischen Flüssigkeiten gelöste Substrate unterschiedlich beeinflusst werden könnten. Im dritten Kapitel wurde der Einfluss der ionischen Flüssigkeiten auf einen Modellkomplex untersucht. Das Reaktionsverhalten des ausgewählten Pt(II) Komplexes zeigte mehrere Abweichungen von seinem normalen Verhalten. Die Reaktionsgeschwindigkeit der Reaktion mit Thioharnstoff wurde in ionischen Flüssigkeiten merklich verlangsamt. Abhängig von der verwendeten ionischen Flüssigkeit war eine 6- bis 240-fache Verlangsamung messbar. Vergleiche der Reaktionsgeschwindigkeiten der Reaktion des Nukleophils Thiocyanat mit dem Modellkomplex zeigten eine bis zu 2000-fache Verlangsamung in den verschiedenen Flüssigkeiten. In Kapitel 4 wurde ein modifizierter Modellkomplex untersucht, bei dem das Pt(II) durch ein Pd(II) Zentralatom ersetzt wurde, um eine höhere Labilität und somit größere Reaktivität des Komplexes zu erreichen, was zu höheren Geschwindigkeitskonstanten führt. Die Reaktion mit dem Nukleophil Thioharnstoff in [emim][NTf2] wurde im Vergleich zum Pt(II) Analogon um das 500-fache beschleunigt, wobei kobs Werte von bis zu 127 s-1 gemessen wurden. Dies stellt die Höchstgrenze der unter dem verwendeten Versuchsaufbau mittels der stopped-flow Methoden messbaren Reaktionsgeschwindigkeiten dar. Mit Thioharnstoff verlief die Reaktion wie erwartet entsprechend einem assoziativen bzw. assoziativen Interchange Mechanismus. Im Fall der ionischen Flüssigkeit [emim][EtOSO3] wurde ebenfalls dieser Mechanismus beobachtet und eine 100-fache Erhöhung der Geschwindigkeitskonstante im Vergleich zum Pt(II) Analogon. Bei den Reaktionen der geladenen Nukleophile in [emim][NTf2] war im Gegensatz zu den ungeladenen Nukleophilen die Ausbildung eines vorgelagerten Gleichgewichtes und somit ein abgewandelter Reaktionsverlauf beobachtbar. In [emim][EtOSO3] war die Reaktion des Nukleophils Thiocyanat stark verlangsamt und zeigte, im Gegensatz zum beobachteten Reaktionsverlauf in [emim][NTf2], eine lineare Konzentrationsabhängigkeit mit einem signifikanten Achsenabschnitt. In Kapitel 5 wurde die Möglichkeit einer Koordination des [NTf2]- Anions an das labile Pd(II) Zentrum des [Pd(II)(ppp)Cl]+ Komplexes untersucht, da hierdurch Beeinträchtigungen der kinetischen Messungen und störende Nebenreaktionen auftreten können. Aus den vielfältigen Präparationsansätzen konnten drei verschiedene Kristalle isoliert und röntgendiffraktometrisch untersucht werden. Diese Arbeit verifiziert die Durchführbarkeit mechanistischer Untersuchungen in ionischen Flüssigkeiten. Die ionischen Flüssigkeiten zeigten in einigen Kriterien ein, den molekularen Lösemitteln vergleichbares Verhalten, beispielsweise bei der temperatur- und druckabhängigen Beeinflussung einiger Lösemitteleigenschaften, wie der Polarität. Andere Aspekte, wie die starke intermolekulare Wechselwirkung der Ionenpaare, grenzen diese neue Lösemittelklasse von den molekularen Lösemitteln deutlich ab. Wie in dieser Arbeit nachgewiesen, können die Wechselwirkungen der Ionenpaare Reaktionen, die Metall-komplexe involvieren, unter teilweise extremer Änderung der Geschwindigkeitskonstanten beeinflussen. Zur Optimierung industrieller Prozesse könnte das genaue Wissen um die Natur und Auswirkung dieser Effekte zur Selektion einer, für die jeweilige Reaktion optimal geeigneten, ionischen Flüssigkeit beitragen

Mobility of Cr and V in Spent Oil Shale: Impact of Thermal Treatment

AbstractSpent oil shale samples were evaluated for potential chromium and vanadium release upon aerobic combustion used in power generation, or anaerobic retorting used in shale oil recovery. Combusted samples released more Cr than retorted or raw samples due to chromate formation. The behavior of vanadium was just opposite in that more V was released from retorted than from aerobically combusted samples, probably due to reduced vanadyl cation formation

Ceftriaxone-loaded PLLA-co-PEG nonwovens towards implant-associated infection prevention

Implant-associated infections remain a challenge in biomedical engineering and prevention of such complications is a topical subject. For that, local drug delivery is associated with a number of advantages over systemic antibiosis. In this context, incorporation of antibiotic drugs into fibrous nonwovens is a promising approach for the generation of antiinfective implant envelopes or wrappings. Such materials can be manufactured in large scale and electrospinning process is suitable for a wide range of drugs to be incorporated. With regard to increasing numbers of pacemaker implantations and associated risk factors for infections, biodegradable ceftriaxone loaded poly(L-lactide)-co-poly(ethylene glycol) (PLLA-co-PEG) nonwovens have been characterised concerning the influence of the drug on morphology, thermal and mechanical properties and drug release behaviour. Our results show that the chosen material combination is promising for further approaches towards an antiinfective nonwoven pacemaker envelope