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

Impact of a tire fire accident on soil pollution and the use of clay minerals as natural geo-indicators

Following the occurrence of a fire at a tire landfill in the surrounding area of Madrid City (Spain), polycyclic aromatic hydrocarbons (PAHs) and trace elements present in soils were analyzed to assess the impact of the fire. The capacity of the soils’ clay mineral fraction to reflect this air pollution incident was studied. Fourteen soil samples were collected at different distances under the smoke plume, and they were subjected to high-performance liquid chromatography–photodiode array detection, inductively coupled plasma mass spectrometry and X-ray diffraction analyses. Clay minerals content showed a strong correlation with the pollutants potentially released in the tire fire, acenaphthene, pyrene, benzo(a)pyrene and benzo(a)fluoranthene. Trace metals Zn and Se were related to the proximity of the tire fire without any relationship with clay minerals content. This work suggests the use of natural clay minerals as potential PAHs geo-indicators in response to air pollution, complementary to current air and biological analysesThis work has been economically supported by the Ministry of Economy and Competitiveness of Spain, Project AGL2016-78490-

Evaluation of the sorption potential of mineral materials using tetracycline as a model pollutant

Tetracycline (TC) is among the most used antibiotics in animal feedstock in the EU. Antibiotics’ persistence as emerging pollutants in the environment is evidenced by their long half-life in residual organic-mineral sediments and waters. The risk associated with this persistence favours antibiotic-resistant microbiota, affecting human health and ecosystems. The purpose of the present work is to assess the adsorption of TC into natural clay minerals, synthetic iron hydroxides and calcined sewage sludge. TC adsorption isotherms were performed in three replicated batch tests at three di erent pH values (4, 6, 8) and TC concentrations (33–1176 mg.L−1). X-Ray di raction (XRD) mineralogy, cation exchange capacity (CEC), Brunauer, Emmett and Teller specific surface area (BET-SSA) and point of zero charge salt effect (PZSE) were determined for the characterization of materials. Sorption was analysed by means of fitting Langmuir and Freundlich adsorption models, which showed good fitting parameters for the studied materials. Low-charge montmorillonite (LC Mnt) is displays the best sorption capacity for TC at maximum TC concentration (350–300 mgTC.g−1) in the whole range of pH (4–8). Sepiolite and smectites adsorbed 200–250 mgTC.g−1, while illite, calcined sludge or iron hydroxides present the lowest adsorption capacity (<100 mgTC.g−1). Nevertheless, illite, sepiolite and ferrihydrite display high adsorption intensities at low to medium TC concentrations (<300 mg.L−1), even at pH 8, as is expected in wastewater environmental conditionsThis work has been economically supported by the Ministry of Economy and Competitiveness of Spain (CTM2013-47874-C2-2-R and AGL2016-78490-R)

Reporte de Estabilidad Financiera - II semestre 2020

El sistema financiero colombiano no ha sufrido mayores traumatismos estructurales durante estos meses de profunda contracción económica, y ha continuado prestando con normalidad sus funciones básicas, facilitando la respuesta de la economía a condiciones extremas. Ello es el resultado de la solidez de las entidades financieras al inicio de la crisis, reflejada en elevados indicadores de liquidez y solvencia, y de la oportuna respuesta de distintas entidades. El Banco de la República redujo 250 puntos sus tasas de interés de política, hasta 1,75%, el menor nivel desde la creación del nuevo Banco independiente en 1991, y otorgó amplia liquidez transitoria y permanente, tanto en pesos como en moneda extranjera. Por su parte, la Superintendencia Financiera de Colombia adoptó medidas prudenciales para facilitar cambios en las condiciones de los créditos vigentes y reglas transitorias de calificación y constitución de provisiones. Finalmente, el Gobierno Nacional expandió las transferencias y los programas de créditos garantizados a la economía. El acervo de crédito real (i.e. descontando la inflación) en la economía supera hoy en 4% el de hace 12 meses, con crecimientos especialmente marcados en la cartera de vivienda (5,6%) y comercial (4,7%) (2,3% en consumo y -0,1% en microcrédito), pero ha habido cambios importantes en el tiempo. En los meses iniciales de la cuarentena las firmas elevaron fuertemente sus demandas por liquidez, y los consumidores las redujeron, mientras que en los meses recientes la dinámica del crédito a las firmas ha tendido a desacelerarse, y la del crédito a los consumidores y a la vivienda ha crecido. El sistema financiero ha respondido satisfactoriamente a la evolución de la demanda relativa de cada grupo o sector, y el crédito posiblemente crecerá a tasas altas en 2021 si el PIB crece a tasas cercanas a 4,6% como lo espera el equipo técnico del Banco, pero los pronósticos son altamente inciertos. Luego de la fuerte cuarentena implementada por las autoridades en Colombia, las turbulencias observadas en marzo y comienzos de abril, evidentes en el enrojecimiento repentino de variables macroeconómicas en el mapa de riesgos del Gráfico A , y la caída en los precios del petróleo y el carbón (nótese las altas volatilidades registradas en la región de riesgo de mercado del Gráfico A), los mercados financieros locales se estabilizaron con relativa rapidez. En esta estabilización tuvo un papel determinante la respuesta de política creíble y sostenida del Banco de la República en lo referente a la provisión de liquidez, con una fuerte expansión de operaciones repo (y variaciones en montos, plazos, contrapartes e instrumentos admisibles), la compra definitiva de deuda pública y privada, y la reducción del encaje de los bancos. En este sentido, hoy se observa abundante liquidez agregada y mejoras importantes en la posición de liquidez de los fondos de inversión colectiva. En este contexto, el principal factor de incertidumbre para la estabilidad financiera en el corto plazo continúa siendo el alto grado de incertidumbre que rodea a la calidad de la cartera. En primer lugar, es incierta la trayectoria futura del número de contagiados y fallecidos como consecuencia del virus y la eventual necesidad de medidas sanitarias adicionales. Por tal razón, también existe incertidumbre sobre la senda de recuperación de la economía en el corto y mediano plazo. En segundo lugar, es incierto el grado en que el choque actual se reflejará en la calidad de la cartera una vez se materialice el riesgo en los estados financieros. De momento, el mapa de riesgos (Gráfico B) indica que la cartera vencida y la cartera riesgosa no han mostrado mayores deterioros, pero la experiencia histórica indica que períodos de fuerte desaceleración económica tienden a coincidir eventualmente con aumentos de la cartera vencida: los cálculos incluidos en este reporte sugieren que el impacto de la recesión sobre la calidad del crédito en el corto plazo podría ser significativo. Ello es particularmente preocupante teniendo en cuenta que la rentabilidad de los establecimientos de crédito ha venido reduciéndose en meses recientes, lo cual podría afectar su capacidad para otorgar crédito al sector real de la economía. Con el fin de adoptar un enfoque prospectivo de cara a las vulnerabilidades identificadas, este reporte presenta varios ejercicios de sensibilidad (stress tests) que evalúan la resiliencia de la liquidez y la solvencia de los establecimientos de crédito y de los fondos de inversión colectiva ante escenarios hipotéticos que buscan aproximarse a una versión extrema de las condiciones económicas actuales. Los resultados sugieren que, en tales escenarios, se observarían fuertes impactos sobre el volumen de crédito y la rentabilidad de los establecimientos de crédito, aunque los indicadores agregados de solvencia total y básica permanecerían en niveles superiores a los límites regulatorios durante el horizonte de los ejercicios. Al tiempo, los ejercicios resaltan la alta capacidad que tiene la liquidez del sistema para enfrentar escenarios adversos. En cumplimiento de sus objetivos constitucionales y en coordinación con la red de seguridad del sistema financiero, el Banco de la República continuará monitoreando de cerca el panorama de estabilidad financiera en esta coyuntura y tomará aquellas decisiones que sean necesarias para garantizar el adecuado funcionamiento de la economía, facilitar los flujos de recursos suficientes de crédito y liquidez, y promover el buen funcionamiento del sistema de pagos. Juan José Echavarría Gerente GeneralRecuadro 1. Consideraciones de largo plazo sobre el acceso temprano al ahorro pensional en Colombia. Autores: Javier E. Pirateque Niño - Daniela X. Gualtero Briceño*Recuadro 2. Indicador de salud financiera para Colombia. Autores: Juan Sebastián Lemus Esquivel - Laura Viviana León Díaz*Recuadro 3. Ejercicios de estrés en tiempos de Covid-19. Autores: Angélica Lizarazo Cuéllar - María Fernanda Meneses*Recuadro 4. Principales medidas tomadas por algunos bancos centrales para canalizar crédito al sector real durante la pandemia. Autor: Daniela X. Gualtero Briceño*Sombreado 1. Efectos de los alivios otorgados a deudores en el marco de la emergencia por el Covid-19. Autor: Eduardo Yanquen

Clonal chromosomal mosaicism and loss of chromosome Y in elderly men increase vulnerability for SARS-CoV-2

The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, COVID-19) had an estimated overall case fatality ratio of 1.38% (pre-vaccination), being 53% higher in males and increasing exponentially with age. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, we found 133 cases (1.42%) with detectable clonal mosaicism for chromosome alterations (mCA) and 226 males (5.08%) with acquired loss of chromosome Y (LOY). Individuals with clonal mosaic events (mCA and/or LOY) showed a 54% increase in the risk of COVID-19 lethality. LOY is associated with transcriptomic biomarkers of immune dysfunction, pro-coagulation activity and cardiovascular risk. Interferon-induced genes involved in the initial immune response to SARS-CoV-2 are also down-regulated in LOY. Thus, mCA and LOY underlie at least part of the sex-biased severity and mortality of COVID-19 in aging patients. Given its potential therapeutic and prognostic relevance, evaluation of clonal mosaicism should be implemented as biomarker of COVID-19 severity in elderly people. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, individuals with clonal mosaic events (clonal mosaicism for chromosome alterations and/or loss of chromosome Y) showed an increased risk of COVID-19 lethality

Evaluation of appendicitis risk prediction models in adults with suspected appendicitis

Background Appendicitis is the most common general surgical emergency worldwide, but its diagnosis remains challenging. The aim of this study was to determine whether existing risk prediction models can reliably identify patients presenting to hospital in the UK with acute right iliac fossa (RIF) pain who are at low risk of appendicitis. Methods A systematic search was completed to identify all existing appendicitis risk prediction models. Models were validated using UK data from an international prospective cohort study that captured consecutive patients aged 16–45 years presenting to hospital with acute RIF in March to June 2017. The main outcome was best achievable model specificity (proportion of patients who did not have appendicitis correctly classified as low risk) whilst maintaining a failure rate below 5 per cent (proportion of patients identified as low risk who actually had appendicitis). Results Some 5345 patients across 154 UK hospitals were identified, of which two‐thirds (3613 of 5345, 67·6 per cent) were women. Women were more than twice as likely to undergo surgery with removal of a histologically normal appendix (272 of 964, 28·2 per cent) than men (120 of 993, 12·1 per cent) (relative risk 2·33, 95 per cent c.i. 1·92 to 2·84; P < 0·001). Of 15 validated risk prediction models, the Adult Appendicitis Score performed best (cut‐off score 8 or less, specificity 63·1 per cent, failure rate 3·7 per cent). The Appendicitis Inflammatory Response Score performed best for men (cut‐off score 2 or less, specificity 24·7 per cent, failure rate 2·4 per cent). Conclusion Women in the UK had a disproportionate risk of admission without surgical intervention and had high rates of normal appendicectomy. Risk prediction models to support shared decision‐making by identifying adults in the UK at low risk of appendicitis were identified

High-pH/low pH ordinary Portland cement mortars impacts on compacted bentonite surfaces: application to clay barriers performance

The design of engineered barrier systems for high-level radioactive waste isolation requires the use of cement-based materials. Small-scale surface reactivity interface experiments were designed to perform a reference laboratory study. It simulated granitic groundwater infiltration through cement mortar/bentonite (CB) binary columns. The tests ran duplicated over 6 and 18 months and included low-pH, CEM I and CEM II ordinary Portland cement mortars in contact with bentonite. After the experiments, the materials were analysed using scanning electron microscopy attached to energy dispersive energy X-ray analysis (EDX), surface mineralogy using grazing incidence X-ray diffraction configurations, specific surface area and effluent chemistry. EDX chemical profiles measured from CB interface contact reproduced, in 100 μm to 1 mm thickness, a characteristic geochemical Mg perturbation in the bentonite and calcite precipitation in cement materials. These processes are known to be developed in 10–15-years within < 5 mm of the interface. The comparison of these long, large scale experiments with the small scale experiments showed that the chemical perturbation thickness development rate will decrease over time. The limestone addition (CEM II) leaves less room for calcite precipitation, and ettringite became stabilized, which limited the extent of dissolution-precipitation processes. Then, the CEM II mortar had better resistance to perturbationThe 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

Bentonite/CEM-II cement mortar INTERFACE EXPERIMENTS: A proxy to in situ deep geological repository engineered barrier system surface reactivity

The present study focuses on the interaction between cement mortar (OPC-based CEM-II) and the FEBEXbentonite; this interaction takes place at a small spatial scale (~1 cm/~1 cm; compacted cement mortar/compacted bentonite thickness) within a timeline of 6 and 18 months. This work was designed to determine the early interaction processes and compare them with large-scale FEBEX in situ underground research laboratory experiments. The study aimed at the primary reactions that occurred at the interface in a small spatial scale (nm- μm scale). The experimental device consisted of a composite column containing the cement mortar/bentonite materials. A granitic groundwater solution was injected through the cement mortar/bentonite system and collected out of the column in sequential syringes for analysis of the chemical composition evolution. For the study of the post-mortem samples, an innovative use of grazing incidence X-ray diffraction was performed to determine the phases produced at the interface. Scanning electron microscopy coupled to energy dispersive X-rays and local specific surface area measurements were also applied. The main results showed the initial development of a Mg perturbation in FEBEX-bentonite at the interface related to the formation of 7 Å precursors of Mg-clay 2:1 sheet silicates as the main neogenic phases expected in the long term. Additionally, a Ca-carbonation skin (calcite) occurred in cement mortar at the interface. The specifications of the reaction products observed at small scales of time and space (μm) are highly promising for the development of reaction concepts and support modelling in the future, which could offer a useful perspective for advancement in the upscaling of concrete/bentonite interface perturbation.This work was supported by funding from the European Union’s Horizon 2020 Research and Training programme from EUROATOM [H2020-NFRP 2014, 2015] under grant agreement nº662147; CEBAM