Geochemical evolution of mg-bentonite affected by the contact of carbon steel and a hydrothermal gradient

Publisher source must be acknowledged with citationCarbon steel and bentonite are materials selected as engineered barriers for high-level radioactive waste confinement. Their long-term interaction must be evaluated to confirm the barrier’s stability. Three laboratory experiments of the carbon steel—Mg-bentonite interaction were conducted for 1, 6, and 22 months under a hydrothermal gradient. Changes in bentonite’s water content, specific surface area, and cation exchange capacity were measured. Mineralogy was studied by X-ray diffraction and scanning electron microscopy. The redistribution of aqueous species and the redox state of iron were determined across the bentonite columns. Results indicated water saturation after 22 months. The specific surface area of bentonite was reduced near contact with the steel, while the cation exchange capacity mostly decreased at 3–6 mm from the steel interface. The corrosion rate decreased with time and bentonite enriched in Fe in the first 1.5 mm from the steel contact. The formation of new Fe-bearing minerals, such as di-tri ferri-sudoite, magnetite, hematite, maghemite, lepidocrocite, siderite and ankerite was observed. Aqueous species redistributed in the porewater of bentonite with decreasing concentrations of Fe and Cl as a function of time and increasing concentrations of Na, Ca and SO4 after 22 months. This occurs under conditions where the bentonite is saturated with Mg, which conditioned the formation and nature of iron clay minerals with timeThis research has been developed by the UAM AcMe research group to support the WP.2 EURAD-ACED project results, which has received funding from the European Union\u2019s Horizon 2020 research and innovation program under grant agreement No. 84759

Genome-Based Genotype × Environment Prediction Enhances Potato (Solanum tuberosum L.) Improvement Using Pseudo-Diploid and Polysomic Tetraploid Modeling

Potato breeding must improve its efficiency by increasing the reliability of selection as well as identifying a promising germplasm for crossing. This study shows the prediction accuracy of genomic-estimated breeding values for several potato (Solanum tuberosum L.) breeding clones and the released cultivars that were evaluated at three locations in northern and southern Sweden for various traits. Three dosages of marker alleles [pseudo-diploid (A), additive tetrasomic polyploidy (B), and additive-non-additive tetrasomic polyploidy (C)] were considered in the genome-based prediction models, for single environments and multiple environments (accounting for the genotype-by-environment interaction or G × E), and for comparing two kernels, the conventional linear, Genomic Best Linear Unbiased Prediction (GBLUP) (GB), and the non-linear Gaussian kernel (GK), when used with the single-kernel genetic matrices of A, B, C, or when employing two-kernel genetic matrices in the model using the kernels from B and C for a single environment (models 1 and 2, respectively), and for multi-environments (models 3 and 4, respectively). Concerning the single site analyses, the trait with the highest prediction accuracy for all sites under A, B, C for model 1, model 2, and for GB and GK methods was tuber starch percentage. Another trait with relatively high prediction accuracy was the total tuber weight. Results show an increase in prediction accuracy of model 2 over model 1. Non-linear Gaussian kernel (GK) did not show any clear advantage over the linear kernel GBLUP (GB). Results from the multi-environments had prediction accuracy estimates (models 3 and 4) higher than those obtained from the single-environment analyses. Model 4 with GB was the best method in combination with the marker structure B for predicting most of the tuber traits. Most of the traits gave relatively high prediction accuracy under this combination of marker structure (A, B, C, and B-C), and methods GB and GK combined with the multi-environment with G × E model

Bistratamides M and N, Oxazole-Thiazole Containing Cyclic Hexapeptides Isolated from Lissoclinum bistratum Interaction of Zinc (II) with Bistratamide K

[Abstract] Two novel oxazole-thiazole containing cyclic hexapeptides, bistratamides M (1) and N (2) have been isolated from the marine ascidian Lissoclinum bistratum (L. bistratum) collected in Raja Ampat (Papua Bar, Indonesia). The planar structure of 1 and 2 was assigned on the basis of extensive 1D and 2D NMR spectroscopy and mass spectrometry. The absolute configuration of the amino acid residues in 1 and 2 was determined by the application of the Marfey’s and advanced Marfey’s methods after ozonolysis followed by acid-catalyzed hydrolysis. The interaction between zinc (II) and the naturally known bistratamide K (3), a cyclic hexapeptide isolated from a different specimen of Lissoclinum bistratum, was monitored by 1H and 13C NMR. The results obtained are consistent with the proposal that these peptides are biosynthesized for binding to metal ions. Compounds 1 and 2 display moderate cytotoxicity against four human tumor cell lines with GI50 values in the micromolar range.Ministerio de Economía, Industria y Competitividad; RTC-2016-4611-

Geochemical Anomalies in Soils and Surface Waters in an Area Adjacent to a Long-Used Controlled Municipal Landfill

Municipal landfills, even when controlled, are potential sources of soil and water pollution in surrounding areas, due to the migration of pollutants through water and air. This research assesses geochemical anomalies of heavy elements and rare earth elements in soils and surface waters in an adjacent area to a controlled municipal landfill near Madrid (Central Spain), under long-term operation. Twenty soil and eighteen water samples were collected in 2017 and 2018 and analyzed for this purpose. Spatial distribution and concentrations of heavy elements (Ag, Cd, Cu, Mn, Ni, Pb, Tl, and Zn) and rare Earth elements (La, Ce, and Gd) are heterogeneous and significantly higher than soil background levels, but below the legal limits to consider intervention. Accumulation of heavy and rare Earth elements in soil nearest the landfill is attributed to occur via wind and wind-driven rain transport, while their accumulation in sediments is attributed to water transport through the creeks. Surface waters show large contamination by organic and inorganic compounds and influence geochemical anomalies in sediments. The water quality is below allowable concentrations for drinking water. The combined evaluation of the soil and water samples performed in the present work is proposed as a pilot study that may be applicable to similar surrounding landfill areas worldwideThe work has been partially financed by the Faculty of Sciences of the Autonomous University of Madrid

Pulverized quartz clasts in gouge of the Alhama de Murcia fault (Spain): evidence for coseismic clast pulverization in a matrix deformed by frictional sliding

The fault gouge of the Alhama de Murcia fault (southeast Spain) shows a texture that resembles a mylonite, including a prominent foliation, S-C fabric, and isoclinal folds. It also embeds a large number of isolated pulverized quartz clasts (PQCs). Structural analysis indicates that the gouge fabric was mainly developed by slow frictional sliding along phyllosili- cate-lined Riedel shear bands during continued shearing. In contrast, the PQCs show tensile fracture network features that are typically reported in seismically pulverized rocks found along seismogenic faults. This suggests that quartz-clast pulverization was due to a transient dilatational mechanism rather than shearing. We propose that the PQCs are the result of a rapid confined stress drop related to transient tensile stresses during coseismic ruptures that interrupt creep faulting along the gouge zone. The present study suggests that there is probably a large amount of evidence for paleoseismicity in fault rocks that is currently overlookedThis research was supported by the Spanish Ministry of Economy and Competitiveness under the INTERGEO (CGL2013–47412-C2–1-P) and QUAKESTEP (CGL2017–83931-C3–1-P) project

Ammonium concentration in stream sediments resulting from decades of discharge from a wastewater treatment plant

A study of ammonium pollution in the sediments of a stream that receives wastewater treatment plant (WWTP) discharge has been carried out. It is urgently necessary to find environmental indicators that can help prevent and detect potential contamination of water, as water is an increasingly scarce resource. To understand the behaviour of ammonium ions introduced by a historical (50-year) contamination process, vertical boreholes were drilled in the stream banks to depths between 30 and 120 cm. Moisture, pH, ammonium (soluble and exchangeable), and clay fraction content were analysed. The variation profile of these parameters was evaluated as a function of depth to determine factors related to the distribution of ammonium in several locations along the stream banks. The ammonium concentration was asymmetrically distributed among samples collected in near-surface locations, with ammonium concentrations between 0.3048 mmol/kg soil and 0.0007 mmol/kg soil. Ammonium was typically concentrated at sediment depths of 30–40 cm, which also exhibited the highest clay fraction content. High positive correlations were detected (r > 0.8; p < 0.0001) among the different ammonium variables (exchanged and dissolved species). No contamination effect was observed below 60–70 cm depth, which was due to ammonium retention in a natural barrier layer of clayey sediment. The clays in our study area (previously identified as smectite, a 2:1 sheet silicate) were able to control the contamination by retaining ammonium in the interlayers, which retarded nitrification. It is suggested that clay could serve as a geo-indicator of ammonium pollution evolutio

Enigmazole C: A Cytotoxic Macrocyclic Lactone and Its Ring-Opened Derivatives from a New Species of Homophymia Sponge

[Abstract] A new macrolide, enigmazole C (1), and two additional analogues, enigmazoles E (2) and D (3), were obtained from a new species of the Homophymia genus as part of an ongoing discovery program at PharmaMar to study cytotoxic substances from marine sources. The structures were fully characterized by cumulative analyses of NMR, IR, and MS spectra, along with density functional theory computational calculations. All three of the new compounds feature an unusual 2,3-dihydro-4H-pyran-4-one moiety, but only enigmazoles C (1) and D (3) showed cytotoxic activity in the micromolar range against A-549 (lung), HT-29 (colon), MDA-MB-231 (breast), and PSN-1 (pancreas) tumor cells.We gratefully acknowledge the Expeditions, Collection and Cell Biology Departments of PharmaMar S.A.U. We also thank S. Bueno and Dra. M. J. Uriz (CEAB-Centro de Estudios Avanzados de Blanes, Spain) for determining the sponge taxonomy and S. Munt for revision of the manuscript. PharmaMar also acknowledges the Udayana University of Bali, Indonesia. J.R. and C.J. acknowledge Xunta de Galicia and CESGA for the computational resource

SEM-EDX study of bentonite alteration under the influence of cement alkaline solutions

Bentonite is a key barrier for the isolation of high-level radioactive waste within Deep Geological Repository. However, bentonite may be altered by contact with cementitious materials and their alkaline pore fluids. This study offers an extensive morphological and semi-quantitative characterization of the bentonite surface exposed to three types of alkaline pore fluids released by different cement-based materials. The bentonite surfaces were studied using a thorough scanning electron microscopy exploration and analysed using an energy-dispersive ꭕ-ray detector (SEM-EDX). In addition, statistical, element mappings, ꭕ-ray diffraction and infrared spectroscopy analyses were performed. The aim was to have a picture of the morphological and chemical alterations of bentonite at very early stages in accordance with the integrated approach necessary to address bentonite stability in the long-term. As a consequence of the reactivity, two types of morphologies stood out in the matrix of bentonite: platelets and coatings-like crusts characterized by their high Mg and Ca content. These alterations presented a different scope depending on the type of alkaline pore solution involved and suggested the precipitation of authigenic magnesium silicate hydrates (M-S-H) and/or trioctahedral clay minerals and Ca‑carbonates. The knowledge of the performance of bentonite subjected to these alkaline solutions can help in the evaluation of the most suitable cement-based materials to be used next to bentoniteThe experimental work was supported by funding from the European Union‘s Horizon 2020 Research and Training programme from EURATOM [H2020-NFRP 2014, 2015] under grant agreement n◦662147; CEBAM

Geochemical interactions at the steel-bentonite interface caused by a hydrothermal gradient

Bentonites are used in deep geological disposal facilities as an engineered barrier to isolate high level radioactive waste, contained in metallic canisters. The present study, performed at laboratory scale, evaluated the behaviour of MX-80 (Na-bentonite) and FEBEX (Ca-Mg-Na-bentonite) in contact with carbon steel, subjected to a hydrothermal gradient. A dominant Na-Cl-SO4 saline solution was injected towards the compacted bentonite from the top, while a heater, located at the bottom in contact with the steel disc, maintained a constant temperature of 100 °C. The cells were studied after one and six months of interaction. Changes in the physical (water content and specific surface area) and chemical (cation exchange capacity and element distribution) properties of the bentonite were observed, as well as the formation of a corrosion layer on the steel, at the interface with bentonite, mainly composed of magnetite, maghemite and hematite. The bentonites were mainly altered at the mm scale, being enriched in iron content, and changing their ion distribution to Ca-dominant smectite (in MX-80 bentonite)This project has received funding from the European Union’s Horizon 2020 research and innovation programme 2014-2018 under grant agreement N◦84759