The Valborraz tungsten mine: Description of a potential source of arsenic pollution

[Abstract] Soil contamination levels were studied in the land affected by an abandoned tungsten mine in Valdeorras (NW Spain). The mine worked mainly in the first half of the twentieth century, and it was definitely closed by 1953. Soil samples were taken in thirteen points within the mine (including both natural soils and soils developed over mine wastes), and in two natural soils close to the mine area. Total heavy metals (Fe, Zn, Ni and Cu) and As were analyzed by X-ray fluorescence in sieved (1000 mg kg-1) were found in all the samples of the mine area, whereas for the heavy metals analyzed no abnormally high concentrations were observed. Although high As background levels are common in soils developed over slates in the region, the concentrations found for the natural soils within the mine were too high to have a geological origin, and they are probably due to contamination from the close mine dumps. The As concentrations in the mine soils were higher than in the natural soils, ranging from 0.5-1% approximately. The highest As concentrations (near 4%) were found in iron oxyhydroxide deposits, which precipitate directly from water in some places in the area. This high As concentrations represent a certain threat to environmental health which has not been quantified yet. Although additional research is needed to determine the potential ecological and human health risks associated with the mine, our results suggest that this location could act as a dangerous As source

Protocol for assessing the effectiveness of protective coatings for roofing slate

España es líder mundial en producción de pizarras de techar; la producción supera las 600.000 toneladas de pizarra de gran calidad, suponiendo más de 300 millones de euros. La aplicación de la pizarra con productos protectores permite comercializar placas más oxidables reduciendo escombreras y problemas ambientales. El presente protocolo sirve para evaluar estos nuevos productos protectores que empiezan a utilizarse en el sector pizarrero. Se propone una combinación de tres ensayos tecnológicos junto con un cuestionario visual para otorgar índices de calidad. Cada ensayo está orientado para clarificar una propiedad importante en el uso de la pizarra de techar: (i) Ciclo térmico para determinar el grado de oxidación de los sulfuros de hierro; (ii) Exposición al gas SO2 para conocer su comportamiento en ambientes urbanos ácidos; (iii) Exposición a la niebla salina y rayos UV para evaluar la eficacia de la capa protectora frente a la corrosión salina y la radiación solaroduction, quarriying more than 600,000 tons of slate of great quality and generating around 300 euros million in sales each year. However, an enormous quantity of slate plates is considered as a low quality product or discarded every year as waste. The application of protective products on roofing slate tiles helps to commercialise slate with higher oxidation rates, reducing wastes and environmental problems. The present protocol serves to evaluate the new protective products that are now used by slate producers. A combination of three technological tests is proposed here, along with a visual questionnaire to grant quality indices. Each test is oriented to clarify critical properties for the future use of the roofing slate, as follows: (i) Thermal cycles were used to determine the oxidation rate of iron sulphides; (ii) Slate behaviour in acid urban atmospheres was interpreted by exposition of slate tiles to SO2 gas; (iii) Effectiveness of the protective layer under saline corrosion and solar radiation was obtained by exposition to saline fog and UV-irradiationFinancial support was provided by the project “Development of a new methodology to protect the roofing slate from oxidation” sponsored by Dirección Xeral de I+D de la Consellería de Industria de la Xunta de Galicia. Thanks are also due to projects S-0505/MAT/000094 of author J.G.Guinea and CGL2004-03564/BTES

Ensayos normativos para la caracterización de patologías en pizarras para cubiertas

The pathologies formed in slate roofs are mainly due to the presence of potentially unstable minerals (iron sulfides, carbonates and organic matter). These minerals may become altered by the effect of environmental agents, once the slate roof is finished. The pathologies are mainly associated with oxidation and gypsification processes of the cited mineral phases. In this work, the potential pathologies of several Spanish roofing slates are identified, using the tests defined in the European Norms EN 12326:2005, 14147:2004 and 11597:2007.Las patologías que se originan en pizarra para cubiertas son debidas fundamentalmente a la presencia de materiales alterables (sulfuros de hierro, carbonatos y materia orgánica). Estos minerales pueden llegar a alterarse por efecto de los agentes medioambientales, una vez que la pizarra es puesta en obra. Las patologías están principalmente asociadas a procesos de oxidación y yesificación de las citadas fases minerales. En este trabajo se determinan las patologías potenciales de varias pizarras para cubiertas españolas, utilizando los ensayos definidos en las normas UNE-EN 12326:2005, 14147:2004 y 11597:2007

Standard tests for the characterization of roofing slate pathologies

Las patologías que se originan en pizarra para cubiertas son debidas fundamentalmente a la presencia de materiales alterables (sulfuros de hierro, carbonatos y materia orgánica). Estos minerales pueden llegar a alterarse por efecto de los agentes medioambientales, una vez que la pizarra es puesta en obra. Las patologías están principalmente asociadas a procesos de oxidación y yesificación de las citadas fases minerales. En este trabajo se determinan las patologías potenciales de varias pizarras para cubiertas españolas, utilizando los ensayos definidos en las normas UNE-EN 12326:2005, 14147:2004 y 11597:2007.The pathologies formed in slate roofs are mainly due to the presence of potentially unstable minerals (iron sulfides, carbonates and organic matter). These minerals may become altered by the effect of environmental agents, once the slate roof is finished. The pathologies are mainly associated with oxidation and gypsification processes of the cited mineral phases. In this work, the potential pathologies of several Spanish roofing slates are identified, using the tests defined in the European Norms EN 12326:2005, 14147:2004 and 11597:2007.El presente trabajo se ha desarrollado en el marco del proyecto PERDURABLE: Durabilidad de materiales de piedra natural. Análisis y prevención de patologías. MICINN-09-CIT-380000-2009-25, financiado por el Ministerio de Ciencia e InnovaciónS

Roofing Slate Deposits in the Iberian Peninsula

España es el principal exportador mundial de pizarras, debido tanto a la calidad excepcional de sus yacimientos, como a los avances tecnológicos que se han ido incorporando en los últimos años en el proceso productivo. El presente artículo describe de manera general los principales litotectos de la Península Ibérica, incluidos dentro del área noroeste del Macizo Ibérico Hespérico, y entre los que destacan los pertenecientes a la Formación Pizarras de Luarca, que en Portugal se correlaciona con la Formación Pizarras de Valongo. En total, en la Península Ibérica se pueden distinguir 12 distritos mineros de pizarra para cubiertas, los cuales son valorados como yacimientos según criterios de tipo minero y petrológico.The exceptional quality of the slate of northwest Spain and the new technological advances incorporated in the last years into the production process have made the country the largest roofing slate producer in the World. This article describes the main slate lithotecs of the Iberian Peninsula. Most of them belong to the Luarca Slates Formation, which in Portugal correlates into the Valongo Slates Formation. Following mining and petrological criteria, a total of 12 mining districts of the Iberian Peninsula have been evaluated as roofing slates deposits.Depto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUEConselleria de Industria y Minas de la Xunta de Galiciapu

COMPARISON BETWEEN FOUR USUAL METHODS OF IDENTIFICATION OF Candida SPECIES

SUMMARY Infection by Candidaspp. is associated with high mortality rates, especially when treatment is not appropriate and/or not immediate. Therefore, it is necessary to correctly identify the genus and species of Candida. The aim of this study was to compare the identification of 89 samples of Candida spp. by the manual methods germ tube test, auxanogram and chromogenic medium in relation to the ID 32C automated method. The concordances between the methods in ascending order, measured by the Kappa index were: ID 32C with CHROMagar Candida(κ = 0.38), ID 32C with auxanogram (κ = 0.59) and ID 32C with germ tube (κ = 0.9). One of the species identified in this study was C. tropicalis,which demonstrated a sensitivity of 46.2%, a specificity of 95.2%, PPV of 80%, NPV of 81.1%, and an accuracy of 80.9% in tests performed with CHROMagar Candida;and a sensitivity of 76.9%, a specificity of 96.8%, PPV of 90.9%, NPV of 91%, and an accuracy of 91% in the auxanogram tests. Therefore, it is necessary to know the advantages and limitations of methods to choose the best combination between them for a fast and correct identification of Candidaspecies

Mineral inlays in natural stone slabs: techniques, materials and preservation

9 paginas, 8 figuras, 1 table et alItaly (first) and Spain (second) are the largest producers of marble in the world, and they share a rich history of quarrying and artworks made from natural stone and coloured stones inlaid in marbles. The present decrease of manufactured marble from Spain and Italy is directly related to the increased imports of high quality manufactured natural stone products from Asian countries. Indian stone products are following classic Florentine patterns coupled with modern uses of resins and heavy machinery. Historic lapidary remains of marbles, rocks and semi-precious stones inlaid in tables displayed in the Prado Museum (Madrid, Spain) have been analysed by X-ray diffraction and microscopy using optical lens with guide lights (in situ samples), polarising and scanning-EDAX microscopes. The Florentine table studied has approximately 8000 pieces; however, they belong to a small number of mineralogical species such as quartz, perthite-feldspar, olivine, garnet, sodalite, hauyne, nosean, pyrite, beryl, chrocidolite, chrysotile, malachite, variscite, etc. The classic stone-cutting techniques were analysed through the study of the historic Gasco hydraulic sawmill, which is well preserved and composed of a dam, canal, waterwheel, well, saw room, external workshops and refuse dump (containing the remains of cut marbles, screws, iron fragments, iron balls, etc.). Decolourisation and phase transition tests of stones were carried out using an original self-simultaneous optical stimulation and X-ray diffraction (SOSXRD) system.The work was supported by the Spanish DGICYT PB98-050l and PNICYDT 1FD97-0959-C03-0l projects.Peer reviewe

Fire resistance of roofing slates: Mechanical, mineralogical and aesthetic changes alongside temperature increase

Fire is a major destructive agent for dimension stone. Practically all historic buildings have suffered one or more fires over the course of their lifespan. There are numerous studies on the effect of fire on stone. Generally speaking, these effects can be divided into aesthetic and structural. Aesthetic effects involve a color shift to reddish hues, due to the oxidation processes triggered by temperature increase. Moreover, structural effects involve the formation of cracks and delaminations that may cause the rock to disintegrate. However, even though roofing slates are a group of metamorphic rocks that are widely represented in the historical architectural heritage of many European countries, none of the scientific studies alluded to above have taken them into account. The present study examines 6 lithotypes, covering the metamorphic range of rocks used as roofing slates. The roofing slates were subjected to a heating test reaching 900 ◦C, and then analyzed using X-ray diffraction and fluorescence, Thermogravimetric and Differential Thermal analyses, and were also tested for bending strength and water absorption following the European standard for roofing slates, EN 12326. All samples studied exhibited a reduction in their bending strength, together with an increase in water absorption. Likewise, the oxidation processes triggered by the high temperatures induced a general oxidation of the iron, lending all of the samples a reddish hue. On the other hand, the roofing slate samples proved to be non-combustible and did not release any toxic or hazardous fumes.This paper has not received funding from any organization or government.Peer reviewe