Search

Chemical and mineralogical investigations of the FEBEX repository demonstration experiment after 18 years confirmed those reactions which were identified in previous large scale tests: Fe-corrosion, Mg-accumulation, cation exchange, and mineral dissolution/precipitation. These reactions were mostly restricted to the bentonite-heater contact. However, other processes were detected. Fe oxidation of carbon-containing steel was dominated by oxic corrosion and hydrolysis possibly through a similar Fischer-Tropsch synthesis reaction, leading to the monitored generation of H2, CO2 and both reduced (alkanes, alkenes) and oxidized non-volatile (carboxylic acids) hydrocarbons, which are in partial equilibrium with CO2/carbonate under oxidation states highly reduced. Therefore, temperature, water, oxygen (due to no gas-tight conditions), and other oxidizing agents regulated the redox state and activities of all species involved in the bentonite barrier, being sulfates reduced to H2S and pyrite, Fe-oxides (hematite/goethite) to magnetite and siderite, and Fe(III)-bearing smectite to saponite and chlorite. These mineral phases were detected as main corrosion products. The dissolved Fe2+ ions generated by reduction of Fe-oxides diffused away forming surrounding greenish halos in the bentonite. Because air was not excluded, most of the corrosion was oxic but locally reducing conditions were established. Significant Mg accumulation was observed at the heater contact, which is related with the highest salinity values of the porewater (Na Mg Ca Cl water-type, 0.41 M ionic strength), the presence of saponite (trioctahedral Mg-smectite), brucite and Fe-rich chlorite; and a modification in the dehydroxylation temperature of the dioctahedral smectite clay mineral particles, together with the precipitation of carbonates and an increase in Ca/Mg at interlayer sites, Na being depleted. The mechanism for the structural clay mineral alteration seems to be Fe(III) structural reduction, rather than the C-steel heater/liner corrosion. Because Fe2+ cations are more stable in trans octahedral sites, rearrangements in crystal lattice seem to have formed cis-trans interstratifications favouring the migration of Mg to octahedral sites and the segregation of Mg2+ trioctahedral domains. Thus, both a solid-state transformation, producing high-charge/low charge layers similar to vermiculite ones; as well as dissolution-precipitation transformation, with the crystallization of a trioctahedral Mg-smectite (saponite), brucite and chlorite in localized zones of the bentonite barrier, seem to be inferred, depending probably on f(O2), temperature, the amount of structural Fe(II) and Mg concentration in the pore water. The observed clay mineral transformations induced changes in some of the physico-chemical properties of the bentonite, decreasing the total cation exchange capacity and BET surface area. However, these modifications were restricted to the bentonite at close contact with the heater. The rest of bentonite from the FEBEX in situ test maintained its performance as an engineered barrier.

Bipolar disorder is a heritable mental illness with complex etiology. We performed a genome-wide association study of 41,917 bipolar disorder cases and 371,549 controls of European ancestry, which identified 64 associated genomic loci. Bipolar disorder risk alleles were enriched in genes in synaptic signaling pathways and brain-expressed genes, particularly those with high specificity of expression in neurons of the prefrontal cortex and hippocampus. Significant signal enrichment was found in genes encoding targets of antipsychotics, calcium channel blockers, antiepileptics and anesthetics. Integrating expression quantitative trait locus data implicated 15 genes robustly linked to bipolar disorder via gene expression, encoding druggable targets such as HTR6, MCHR1, DCLK3 and FURIN. Analyses of bipolar disorder subtypes indicated high but imperfect genetic correlation between bipolar disorder type I and II and identified additional associated loci. Together, these results advance our understanding of the biological etiology of bipolar disorder, identify novel therapeutic leads and prioritize genes for functional follow-up studies. © 2021, The Author(s), under exclusive licence to Springer Nature America, Inc.

An in situ water sampling experiment was performed in the Opalinus Clay formation (Switzerland), with the aim of obtaining undisturbed pore water samples for its characterization. The study was made from a dedicated borehole, named BDI-B1, drilled in March 2002 in the DI niche of the Mont Terri Rock Laboratory, located at the north-western part of the formation, a few meters away of the underlying Jurensis Marl formation. Five water sampling campaigns have been completed, and on site measurements of the key parameters of the water, such as pH, Eh, Fe(II), S2− and alkalinity, were performed under controlled conditions inside an anoxic glove box. The chemical composition of the seepage waters obtained from the borehole is Na–Cl type, with an ionic strength of about 0.4 M. The Cl concentrations fit the concentration profile of the Opalinus Clay pore water obtained in previous experiments from boreholes and squeezed water samples. The highest salinity is found in this zone of the Opalinus Clay, with around 12 g/L of chloride. A perturbation of the rock system was produced during the first stages of the experiment due to a packer failure. As a consequence, the borehole was exposed to air during the first phase of the experiment. The main perturbations induced were: (1) pyrite oxidation that caused an increase of sulphate, calcium, magnesium and bicarbonate content in the waters; and (2) the inflow of 3H-bearing water vapour that could penetrate the EDZ. This fresh water infiltration could have mixed with the original formation water, and tritium contents of up to 3.8 TU were measured in the first water sampling campaigns. Nevertheless, after some time the hydrogeochemical conditions of the formation were recovered, and the long-term instrumentation and monitoring of the borehole made possible to obtain different parameters of the formation. Successive water sampling campaigns show a tendency to the stabilization of the main parameters of the water, such as sulphate and pH to values of 1600 mg/L and 7.6, respectively. The on site determination of the key parameters of the pore waters such as pH, Fe(II) and alkalinity has allowed to model the main water–rock interaction processes of the Opalinus Clay formation. A redox potential of −196 mV at pH 7.6 was obtained.

International audience; Knowledge of the pore water chemistry in clayrock formations plays an important role in determining radionuclide chemical speciation and migration in the context of nuclear waste disposal. Among the different in situ and ex situ techniques for pore water sampling in clay sediments and soils, the squeezing technique dates back 115 years. Although different studies have been conducted on the reliability and representativeness of squeezed pore waters, most of these involved high-porosity, high water content and unconsolidated clay sediments. Very few of them analysed squeezed pore water from low-porosity, low water content and highly consolidated clayrocks.In this paper, a specially designed and fabricated one-dimensional compression, two-directional fluid flow cell was used to extract and analyse the pore water composition of Opalinus Clay core samples from Mont Tern (Switzerland) with water contents between 6.2 and 7.8 wt.% A study of the influence of the squeezing pressure on the chemistry of the pore water was performed at pressures of up to 200 MPa. To validate and demonstrate the validity of the squeezing technique for obtaining reliable pore water, different tests were performed at various pressures and the squeezed waters were compared with those obtained by other methods, such as in situ collected borehole waters. The reproducibility and quality of the squeezing method was also checked, as well as different artifacts which could affect the reliability of the pore water data.The results show that the reproducibility of the technique is good and no membrane effect (ionic ultrafiltration, chemical fractionation, anion exclusion) was found in Opalinus Clay at Mont Terri in the range of pressures analysed (70-200 MPa). Pore waters extracted in this range of pressures do not decrease in concentration as a function of pressure, which indicates that a dilution of water by mixing of the free pore water and the outer layers of diffuse layer water does not occur and a threshold (safety) squeezing pressure of 175 MPa could be established to avoid membrane effects. Furthermore, a direct comparison against in situ collected borehole waters shows that the pore waters extracted at these pressures are representative of the Opalinus Clay Formation at Mont Terri. Extraction artifacts such as temperature effect, oxidation and degassing can be avoided or minimised by taking special precautions when preparing and handling the core sample and extracting the pore water. Finally, we show that it is possible to obtain insightful information on anion-accessible porosity by combining squeezing data with aqueous leaching data to characterise the pore water composition and solute distribution for different rock porosities.