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Abstract: Swelling of shale in response to interaction with water is an important consideration within subsurface energy systems. In the case of waste disposal, swelling can provide important barriers around the waste and enhance the sealing ability of rocks. For shale gas exploration purpose, however, swelling may cause wellbore instability. Therefore, a careful study of shale swelling is critical for subsurface energy related applications. Here, the swelling effects of shale were imaged at nanoscale using an advanced synchrotron Transmission X-ray Microscopy (TXM) imaging technique for the first time, with a spatial resolution down to 40.9 nm. Organic matter and clays within the analysed sample were observed to display large swelling effects which resulted in a 50% reduction in porosity. Strain maps generated using Digital Volume Correlation (DVC) show deformation and significant strain were mostly localized to between the contact boundaries of sharp brittle minerals and softer organic matter and clays. This is the first study, to our knowledge, to directly image the swelling deformation of shale at the tens of nanometer scale and provide local information on the strain evolution.

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Abstract: The reactions of H2, CO2, and CO gas mixtures on the surface of Cu at 200 °C, relevant for industrial methanol synthesis, are investigated using a combination of ambient pressure X-ray photoelectron spectroscopy (AP-XPS) and atmospheric-pressure near edge X-ray absorption fine structure (AtmP-NEXAFS) spectroscopy bridging pressures from 0.1 mbar to 1 bar. We find that the order of gas dosing can critically affect the catalyst chemical state, with the Cu catalyst maintained in a metallic state when H2 is introduced prior to the addition of CO2. Only on increasing the CO2 partial pressure is CuO formation observed that coexists with metallic Cu. When only CO2 is present, the surface oxidizes to Cu2O and CuO, and the subsequent addition of H2 partially reduces the surface to Cu2O without recovering metallic Cu, consistent with a high kinetic barrier to H2 dissociation on Cu2O. The addition of CO to the gas mixture is found to play a key role in removing adsorbed oxygen that otherwise passivates the Cu surface, making metallic Cu surface sites available for CO2 activation and subsequent conversion to CH3OH. These findings are corroborated by mass spectrometry measurements, which show increased H2O formation when H2 is dosed before rather than after CO2. The importance of maintaining metallic Cu sites during the methanol synthesis reaction is thereby highlighted, with the inclusion of CO in the gas feed helping to achieve this even in the absence of ZnO as the catalyst support.

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Abstract: The agricultural soils of West Limerick, Ireland, contain very localised, extremely high natural Se concentrations that reach levels that are very toxic to grazing livestock. The Carboniferous shales that formed in anoxic deep-water marine environments are the source of the selenium, which, along with the other redox-sensitive elements of molybdenum, uranium, arsenic and vanadium, were mobilised and reprecipitated in post-glacial anoxic marshes. The result has been a history of selenosis and molybdenosis in livestock in this important dairy province. Soils collected at 10–20 cm from five different agricultural sites were analysed, and all yielded concentrations greatly in excess of the safe Se limits of 3–10 mg kg−1; the highest value recorded was 1265.8 mg kg−1 Se. The highest recorded value for Mo in these soils was 1627.5 mg kg−1, and for U, 658.8 mg kg−1. There was a positive correlation between Se, Mo U and organic matter in the soils. Analysis of non-accumulator pasture grasses (Lolium perenne (perennial ryegrass), Festuca arundinacea (tall fescue), Dactylis glomerata (cocksfoot) and Phleum pretense (timothy grass)) revealed the shoot/leaf to contain up to 78.05 mg kg−1 Se while Trifolium repens (white clover) leaves contained 296.15 mg kg−1 Se. An in situ growing experiment using the Se accumulator species Brassica oleracea revealed 971.2 mg kg−1 Se in the leaves of premier kale, which also contained 1000.4 mg kg−1 Mo. Translocation factors (TFs) were generally higher for Mo than Se across all plant species. Combined X-ray absorption near edge spectroscopy (XANES) with micro-X-ray fluorescence (μ-XRF) showed the Se was present in the soil predominantly as the reduced immobile phase, elemental Se (Se0), but also as bioavailable organoselenium species, mainly selenomethionine (SeMet). SeMet was also the main species identified within both the Se non-accumulator and Se accumulator plants. The Se soil–plant system in West Limerick is dominated by SeMet, and uptake into the cattle pasture results in selenosis in the grazing dairy herds. The hyperaccumulating Brassica oleracea species could be used to extract both the Se and Mo to reduce the toxicity of the blighted fields.

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Abstract: The alteration of olivine-rich rocks to serpentine minerals, (hydr)oxides, and aqueous hydrogen through serpentinization is long thought to have influenced the distribution of habitable environments on early Mars and the evolution of the early Martian hydrosphere and atmosphere. Nevertheless, the planetary importance of Martian serpentinization has remained a matter of debate. To constrain the process and products of Martian serpentinization, we studied serpentinized iron-rich olivines from the 1.1-billion-year Duluth Complex. These data indicate that serpentinized iron-rich olivine would have been accompanied by a fivefold increase in hydrogen production relative to serpentinized terrestrial mantle peridotites. In contrast to previous expectations, this style of serpentinization yields hisingerite as the dominant iron serpentine mineral at comparatively low temperature and pH, consistent with meteorite mineralogy and in situ rover data. The widespread occurrence of oxidized iron-bearing phyllosilicates in highly magnetized regions of the Martian crust supports the hypothesis that serpentinization was more pervasive on early Mars than currently estimated.

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Abstract: An understanding the organic matter (OM) in primitive interplanetary materials can provide us with important constraints on both the early solar system carbon cycle and incipient prebiotic synthesis before the origin of life. As a window to the past, primitive chondrites preserve the most pristine record of parent body, nebular and interstellar components and the occurrence of OM in them has been shown in both soluble (SOM) (1) and insoluble (IOM) (2) form. Total organic carbon (TOC) abundance reaches ~3-4 wt% in the most primitive carbonaceous chondrite (CCs) (3), such as Ivuna-type chondrites (CIs) – thus making them highly desirable for the OM studies, and relevant to the study of Asteroid 162173 Ryugu samples from the Hayabusa-2 mission. A combination of both SOM and IOM analysis of organic bulk meteorite separates together with in-situ analysis of OM have provided a comprehensive account of chondritic OM (4). In the case of in-situ analysis, the combination of both scanning (SEM) and transmission electron microscopy (TEM) together with soft X-Ray scanning transmission microscopy (STXM) have shown the presence of micron to submicron distinctive organic particles (OPs) (5). Carbon K-edge X-ray absorption near edge structure (XANES) has shown the aromatic-carbonyl-carboxyl chemical nature of these organic particles (5). In addition, aromatic-poorer and carboxylic-richer diffuse OM (6) within both amorphous and phyllosilicate occurs as well. As observation techniques are getting better, aberration corrected TEM coupled with electron energy loss spectroscopy (EELS) might provide the same results as carbon XANES, but with higher image magnification, rapid data acquisition and better accessibility. In this context, we present the results of a comparative carbon K-edge XANES and EELS study of CI meteorite Ivuna. An approximately 100 nm lamella of the Ivuna meteorite was prepared using focused ion beam (FIB)-SEM with the Helios 5 Hydra DualBeam (CEITEC, Masaryk University, Czechia) and analysed by TEM-EELS with the JEOL ARM200CF (ePSIC, Diamond Light Source, UK) and STXM-XANES at Beamline BL19A of the KEK Photon Factory, Japan. We observed that (I) XANES on samples that did not experience TEM-EELS are in agreement with the previous studies of aromatic-carbonyl-carboxylic macromolecular OPs and IOM, while (II) the TEM-EELS of OPs show aromatic-carbonyl functional chemistry but with amorphous carbon convoluting the carboxylic peak, and aromatic-poor spectra with a sharp carbonate peak in diffuse OM. The difference between XANES and EELS particularly in the diffuse OM can be interpreted by electron-beam damage. Thickness and e-beam damage leads to amorphous C formation in the OPs. In the case of more labile OM in the phyllosilicate, its change by heating and oxidation is expected.