Toward the Control of the Smoldering Front in the Reaction-Trailing Mode in Oil Shale Semicoke Porous Media

Results of an experimental investigation on the feasibility of propagating a smoldering front in reaction-trailing mode throughout an oil shale semicoke porous medium are reported. For oil recovery applications, this mode is particularly interesting to avoid low-temperature oxidation reactions, which appear simultaneously with organic matter devolatilization in the reaction-leading mode and are responsible for oxidation of part of the heavy oil. The particularity of this mode is that, contrary to the reaction-leading mode largely studied in the literature, the heat-transfer layer precedes the combustion layer. This leads to two separated high-temperature zones: (i) a devolatilization zone (free of oxygen), where the organic matter is thermally decomposed to incondensable gases, heavy oil, andfixed carbon, also called coke in the literature, without any oxidation, followed by (ii) an oxidation zone, where thefixed carbon left by devolatilization is oxidized. The transition from reaction-leading to reaction-trailing mode was obtained using low oxygen contents in the fed air. It is shown that two distinct layers, the heat-transfer layer and the combustion layer, propagate in a stable and repeatable way. The decrease of the oxygen fraction leads to a decrease of the smoldering temperature and to strongly limit the decarbonation of the mineral matrix. The CO2 emissions are limited. Regardless of the front temperature, all of the fed oxygen is consumed and all of thefixed carbon is oxidized at the passage of the smoldering front

Lactic Acid Induces Aberrant Amyloid Precursor Protein Processing by Promoting Its Interaction with Endoplasmic Reticulum Chaperone Proteins

Lactic acid, a natural by-product of glycolysis, is produced at excess levels in response to impaired mitochondrial function, high-energy demand, and low oxygen availability. The enzyme involved in the production of β-amyloid peptide (Aβ) of Alzheimer's disease, BACE1, functions optimally at lower pH, which led us to investigate a potential role of lactic acid in the processing of amyloid precursor protein (APP).Lactic acid increased levels of Aβ40 and 42, as measured by ELISA, in culture medium of human neuroblastoma cells (SH-SY5Y), whereas it decreased APP metabolites, such as sAPPα. In cell lysates, APP levels were increased and APP was found to interact with ER-chaperones in a perinuclear region, as determined by co-immunoprecipitation and fluorescence microscopy studies. Lactic acid had only a very modest effect on cellular pH, did increase the levels of ER chaperones Grp78 and Grp94 and led to APP aggregate formation reminiscent of aggresomes.These findings suggest that sustained elevations in lactic acid levels could be a risk factor in amyloidogenesis related to Alzheimer's disease through enhanced APP interaction with ER chaperone proteins and aberrant APP processing leading to increased generation of amyloid peptides and APP aggregates

Iodine solubility and speciation in glasses

International audienceThe study of iodine in glasses and melts is critical in many areas, from geosciences to materials science to waste management. Glasses in the ternary system Na2O-B2O3-SiO2 were studied with the goal of identifying a glass matrix able to dissolve large quantities of this element, and to identify the main parameters affecting the solubility of iodine. Two sets of experiments were carried out: the first one with the aim of determining the solubility limit of iodine, and the second one to identify the structural variations occurring within the glass network upon iodine incorporation, and to identify the parameters influencing the most both iodine solubility and speciation. We demonstrated that there is a strong dependence of iodine incorporation on bulk chemistry and glass physical properties. A solubility limit of ~5 mol% I has been assessed for B2O3-rich glasses and of ~1 mol% for SiO2-rich ones, and this composition dependence has been explained by considering the fragility parameter of the glass network. Structural variations in the iodine local environment and in the glass network were characterized by Raman, X-ray Absorption Spectroscopy, and 11B NMR. Spectroscopy data point out the coexistence of different I species within the glasses, with iodide being the predominant one, surrounded by Na+ ions

Iron speciation in olivine-hosted melt inclusions inferred from Mössbauer spectroscopy

International audienceXANES spectroscopy is widely used to provide the oxidation state of magmas by determining their Fe3+/ΣFe ratios. This technique applied to glasses and olivine-hosted melt inclusions suggests that arc basalts are generally much more oxidized (Fe3+/ΣFe ratios from 0.190 to 0.344; [1-4]) than MORBs (Fe3+/ΣFe ratio of 0.14 ± 0.01; [5]).These resultsimply thatthe mantle beneath arcs ismore oxidized by one log unit relative to the QFM buffer than the mantle source of MORBs [1-5]. However, a recent study demonstrates that hydrous glasses canbe affected by beam-induced oxidation during XANES analysis that can lead to an over-estimation of their Fe3+/ΣFe ratios [6]. In this study, and for the first time, Fe3+/ΣFe ratios in olivine-hosted melt inclusions from various arcs, OIB and MORB localities were analyzed by synchrotron Mössbauer spectroscopy. Fe3+/ΣFe ratios obtained with this method allow us to constrain the oxidation state of those magmas by avoiding the effect of photo-oxidation that occurs during XANES analysis. A comparison between Fe3+/ΣFe ratios obtained by XANES and Mössbauer is carried out to determine whethera correction for beam-induced oxidation can be applied. Then, Fe3+/ΣFe ratios in these magmas will be used to constrain the oxidation state of the primary magmas formed in these different geological settings.[1] Brounce et al. (2014) J. Petrol. 55, 12, 2513‑2536 [2] Brounce et al. (2015) Geology43, 9, 775‑778 [3] Kelley & Cottrell (2009) Science325, 605‑607 [4] Kelley & Cottrell (2012) Earth Planet. Sci. Lett. 329‑330, 109‑121 [5] Zhang et al. (2018) Chem. Geol. 479, 166‑175 [6] Cottrell et al. (2018) Am. Mineral. 103, 4, 489‑50

Iron speciation at the riverbank surface in wetland and potential impact on the mobility of trace metals

International audienceFe oxyhydroxides in riverbanks and their high binding capacity can be used to hypothesize that riverbanks may act as a “biogeochemical filter” between wetlands and rivers and may constitute a major mechanism in the trapping and flux regulation of chemical elements. Until now, the properties of Fe minerals have been very poorly described in riverbanks. The goals of the present work are to identify Fe speciation in riverbanks where ferric deposits are observed and to determine their impact on the metal behavior (As, Co, Cu, Ni, Pb, Zn, etc.).At the surface, Fe speciation is mainly composed of small poorly crystalline Fe phases, i.e. ferrihydrite (~30%), Fe-OM associations (~40%) as well as crystalline Fe phases, i.e. goethite (~35%). At the subsurface, the Fe distribution is dominated by goethite (~35%) and Fe-mica (~35%), the proportion of which increases at the expense of ferrihydrite and the Fe-OM associations.At the riverbank surface, ferrihydrite and the Fe-OM associations are therefore the main Fe hosting phases in response to (i) the fast Fe(II) oxidation induced by the presence of O2 and (ii) the high amount of OM favoring the formation of nano-phases bound to OM (Fe monomers, polymers and nanoparticles) and preventing mineralogical transformation (ferrihydrite into goethite).During the high-water level period (high flow), a strong erosion of the riverbank transfers these ferric deposits into the river. However, the physicochemical parameters of the river (pH 6.6–7.6 and continuous oxic conditions) do not promote the dissolution of Fe oxyhydroxides and OM. Ferric deposits and the associated trace metals are therefore maintained as colloids/particles and are exported to the outlet. All of the results presented here demonstrate that the ferric deposits trap metals on a seasonal basis and are therefore a key factor in the mobilization of metals during riverbank erosion by river flow