F. Macias-Vazquez - Academia.edu (original) (raw)

Papers by F. Macias-Vazquez

Consejo Superior de Investigaciones Científicas (España), 1988

(**) y f. Guit.ián Rivera (*). RESUMEN Se realiza la identificación por métodos químicos e instru... more (**) y f. Guit.ián Rivera (*). RESUMEN Se realiza la identificación por métodos químicos e instrumentales de un fosfato magnésico hidratado localizado en form,a de re.cubrimientos y costras ,en ,las rocas graníticas de Monte Louro (La Coruña). La determinación del comportamiento de este mineral durante su deshidratación permite, comprobar el estrecho paraleNsmo •existente entre la pérdida de ,agua y ,la destrucción de la newberyita. Teniendo ,en cuenta la 'escas'a estabilidad de la newberyitaen los medios de alteración y su frecuente asociación con la «struvita» se atribuye a ,est,emineral un origen organógeno, discutiéndose la posibilidad de' que se encuentre estabilizado por la presenci,a de r,ecubrimi'entos de fosf.atos cálcicos (Brushita y/o Monetita). SUMMARV The identific'ation of .a hydrated magneslc phosphate is carried out by chemical and instrumentalmethods. This is found the shape of overlag and crust on the granitic rocks on Monte Lauro. The determination of its behaviour during the dehydratation 'is performend, let us check the elosed paraHe:lism hetween the loss of water ,and the destruction of the new" beryite structure. This mineral isimput,ed to have an organic origin taking into account its short ,stabilityin weatheringenvironments and its freguent assooiation with the «struviteD. Itis presumend the posibility of becomíng sta.bilited by the pres,enc-e of calcic phosphate co,atings (Brushitaand/or Monetite).

Anales de Edafologia y Agrobiologia, Aug 2, 1988

European Journal of Soil Science, 2011

Soil organic matter (SOM) in Alu-andic Andosols and Alu-humic Umbrisols is believed to accumulate... more Soil organic matter (SOM) in Alu-andic Andosols and Alu-humic Umbrisols is believed to accumulate because of the protection caused by binding to aluminium (Al). We investigated soils that differed in the abundance of organo-Al complexes to determine the effect of such binding on SOM chemistry. For this, the surface horizons of three types of acid soils in the Basque Country (northern Spain) under forest stands were studied: (i) Alu-andic Andosols (AND soils) on basalts and trachytes, (ii) Umbrisols or so-called 'aluminic'(ALU) soils also on basalts and trachytes and (iii) soils with a podzolizing trend (POD), on quartzites. Values of Al extractable with sodium pyrophosphate (Al p) in the surface horizons of these soils ranged between 8.5 and 13.1, 1.9 and 9.3, and 0.8 and 3.7 g kg −1 dry weight, for the AND, ALU and POD soils respectively. For POD and ALU soils, surface horizons were sampled at two depths, 0-5 and 5-20 cm, whereas the AND soils were sampled at different depths down to the B horizon. NaOH-extractable SOM from three AND soils, 12 ALU soils and 12 POD soils was studied by pyrolysis-gas chromatography/mass spectrometry. The POD soils had the largest loads of plant-derived markers (lignin, long-chain alkanes and alkenes, methyl ketones, fatty acids); SOM of the AND soils had the smallest amounts of plant-derived SOM and the largest amounts of microbial products (microbial sugars and N-compounds) of the soils studied. ALU soils had an intermediate pattern, as expected. The results indicate that the SOM of Alu-andic Andosols, developed from basalt and trachyte rocks, is essentially dissimilar to that of soils derived from quartz-rich parent material, under the same climate conditions and similar forest stands. The dominance of secondary (microbial-derived) SOM in Alu-andic Andosols, also observed in previous research on Sil-andic Andosols (these are dominated by shortrange ordered Si compounds in contrast to the dominance of organo-Al complexes in Alu-andic Andosols), reveals the small contribution of primary (plant-derived) material to SOM in soils with andic properties.

Fresenius Environmental Bulletin

ABSTRACT

Rock Mechanics and Rock Engineering, 2014

Abrasion on tunnel boring machine (TBM) cutters may be critical in terms of project duration and ... more Abrasion on tunnel boring machine (TBM) cutters may be critical in terms of project duration and costs. Several researchers are currently studying the degradation of TBM cutter tools used for excavating hard rock, soft ground and loose soil. So far, the primary focus of this research has been directed towards abrasive wear. Abrasive wear is a very common process in TBM excavation, but with a view to the environment in which the tools are working, corrosion may also exert an influence. This paper presents a selection of techniques that can be used to evaluate the influence of corrosion on abrasion on TBM excavation tools. It also presents the influence of corrosion on abrasive wear for some initial tests, with constant steel and geomaterial and varying properties of the excavation fluids (soil conditioners, anti-abrasion additives and water). The results indicate that the chloride content in the water media greatly influences the amount of wear, providing evidence of the influence of corrosion on the abrasion of the cutting tools. The presence of conditioning additives tailored to specific rock or soil conditions reduces wear. However, when chloride is present in the water, the additives minimise wear rates but fail to suppress corrosion of the cutting tools.

European Journal of Soil Science, 2008

The objective of this study was to determine to what extent the attenuation or loss of andic soil... more The objective of this study was to determine to what extent the attenuation or loss of andic soil properties caused by land use change-from forest (FOR, average C content 118.2 AE 23.7 g kg À1) to agricultural land (AGR, average C content 55.7 AE 16.7 g kg À1) use-is reflected in soil organic matter (SOM) at the molecular level. For this, NaOH-extractable SOM of A horizons from 17 soils developed on amphibolitic parent material in NW Spain was studied by pyrolysis gas chromatography spectrometry (Py-GC/MS). We also included two buried andic A horizons (PAL, 2200 cal yr BP in age) on the same parent material, as a reference for the molecular composition of SOM from soils without recent litter additions. Organic matter of PAL soils had a composition largely different from that of superficial soils (FOR and AGR), with an important relative contribution of microbial polysaccharides and Ncompounds, and an absence of compounds that characterize fresh plant litter (e.g. lignins). In the superficial soils, the relative contribution of lignin-derived compounds was greater in AGR than in FOR soils. Differences were also observed in the relative contribution of aliphatic compounds, FOR soils being enriched in this type of components compared with AGR soils. The results indicated that land use change from FOR to AGR, which was accompanied by a decrease in total SOM, resulted in an enrichment in primary SOM. The smaller relative abundance of primary SOM derivatives in andic FOR soils indicates that these compounds were quickly degraded in Andisols.

Se determinó la capacidad máxima de adsorción de fosfatos en un Tecnosol con propiedades ándicas.... more Se determinó la capacidad máxima de adsorción de fosfatos en un Tecnosol con propiedades ándicas. El Tecnosol fue diseñado, formulado y elaborado para reducir las concentraciones de P en sistemas acuáticos, contribuyendo a la reducción de la eutrofización y sus consecuencias nocivas. Después de seis meses sumergido en aguas del río Limia, la capacidad de adsorción del Tecnosol apena disminuyó. Por este motivo, se decidió realizar un ensayo de adsorción en laboratorio y someter el Tecnosol a ciclos de aporte de P. Para simular condiciones naturales en aguas eutrofizadas, los ensayos se realizaron con concentraciones de 1 mg.L-1, mientras que para monitorizar la respuesta a condiciones extremas se añadieron también dosis de 100 mg.L-1 en paralelo. Para contrastar el efecto que tuvo ese periodo sumergido en agua sobre el Tecnosol se utilizaron dos grupos de muestras: el Tecnosol usado y el mismo Tecnosol conservado sin uso. La máxima de adsorción del Tecnosol sin usar puede llegar a 75...

Clay Minerals, 1981

Analysis of the distribution of gibbsite in soils and saprolites of Galicia, NW Spain, leads to t... more Analysis of the distribution of gibbsite in soils and saprolites of Galicia, NW Spain, leads to the conclusion that this mineral is mostly formed by inorganic mechanisms in open, well-drained and desaturated systems in the initial stages of weathering of various aluminosilicates, especially plagioclases. No evidence has been found to support the hypothesis that it is a feature inherited from hotter climates, as it has not been identified to date either in ancient sediments or in the most evolved and weathered soils. The role of organic matter and the possibility ofa biogeochemical origin is also discussed: it is considered that this mechanism is only important during podsolic soil development.

Mantenimiento Ingenieria Industrial Y De Edificios, 2000

as published by the spanish Department of Public Works. Phase diagrams for the systems SiO r Al 2... more as published by the spanish Department of Public Works. Phase diagrams for the systems SiO r Al 2 0 r H 2 0, K20-Si02-AI203-H20, Na20-Si02-AI203-H20, MgO-Si0 2-A1 2 0 3-H 2 0, and CaO-SiO r A1 2 0 3-H 2 0, for 298 K and 1 atm. conditions, are used in order to determine the mineralogical stability, and therefore neoformation trends. Stable and metastable phases were taken into accaunt to draw the diagrams (Fernandez Marcos and Macias, 1987). The prevailing trend in the Peninsula, according to this method, is towards kaolinite neoformation. Nevertheless differences are observed between watersheds. So kaolinite is the only stable mineral neoformed in the North watersheds while there exist several stable minerals (kaolinite, mica, (kaolinite, mica, chlorite, pyraphillite) ar metastable ones (smectite) in the Tajo, Guadiana, Guadalquivir, South, Jucar, Segura and East Pyrenees watersheds, depending on sampling point and date. Geographic distribution of different minerals is satisfactorily explained by taking into account: rainfall distribution, sileceous or calcareous nature of ground, and upper, medium or lower position in the river course.

Congresos Carga Final, Jun 1, 1993

e presentan los datos qUlmlcos y mineralógicos de 77 muestras de rocas esquistosas de la "Unidad ... more e presentan los datos qUlmlcos y mineralógicos de 77 muestras de rocas esquistosas de la "Unidad Betan zos-Arzúa", perteneciente al "Complejo de Ordes" , coõ bjeto de analizar la variabilidad existente y discutir las posibilidades de sectorización de los distintos tipos de rocas en función de parámetros de composición.

Anales De Edafologia Y Agrobiologia, 1980