Maite García-Vallès

Biomineralization Processes on Rock and Monument Surfaces Observed in Field and in Laboratory Conditions

Monument surfaces lack mechanisms of self-protection and regeneration but tend to accumulate inorganic and organic substances from the surrounding environment, most of which can serve as nutrients for many microorganisms. When the precipitation of mineral phases is faster than the decay mechanisms, as a consequence of interactions among rock surfaces, pollutants, climate, and microorganisms, then crusts and patinas are formed. We report laboratory studies to characterize microorganisms, recreate geomicrobial processes, and characterize the mechanisms involved through the use of experimentally infected stone slabs. The aim of our article was to combine the characterization of natural stone and microflora presently colonizing rock surfaces and the laboratory experiments in which controlled conditions were applied to the observation of geomicrobial processes leading to surface deterioration. The results show that the majority of bacteria isolated from stone surfaces are able to precipitate CaCO3 in the form ...

Coloured mineral coatings on monument surfaces as a result of biomineralization: the case of the Tarragona cathedral (Catalonia)

Successive coloured coatings on the Taragona cathedral (Catalonia) were analyzed using chemical, microbiological and mineralogical techniques. The coatings consist of mainly biogenic minerals (calcite, several oxalates, phosphates) and their fabric and composition is independent of the underlying rock. The origin of the crusts or patinas is attributed to bygone (sub-fossil) microflores which formed biofilms and microbial mats on and within the surface of the limestones and marbles of the cathedral. The staining of the patina layers is not related to the mineral colours, nor to anthropogenic dust or fly-ashes. The colours are most probably organic pigments embedded between the crystals and Fe- and Mn-organic compounds remaining from bioactivity. A sequential hypothesis of the origin(s) of the patina layers is given.

Biological weathering and mineral deposits of the Belevi marble quarry (Ephesus, Turkey)

Rock samples from the Belevi quarry have been studied, in order to compare processes occurring in natural rocks with those on monuments. The quarry is formed by calcitic marble with different grain sizes. Surfaces affected by different kinds of patinas, whose colors range from black to beige-brown and orange, exhibit different thicknesses and structures. The alterations studied can be reported as two main types: (i) biological weathering (biopitting); (ii) mineral deposits (patinas). Main component of patina is calcite and a smaller quantity of calcium oxalate. From the textural point of view, there is a wide variety of typologies with a close relationship to the slope and water availability. The development of these patinas is related to the bioactivity. Their composition, morphology and evolution are comparable to those developed in other quarries and monuments of the Mediterranean basin.

Environmental geochemistry of ancient volcanic ashes.

Volcanic ashes from the Puna and surrounding Andean areas in northern Argentina show that sometimes volcanic ash deposits are very well preserved (up to several million years) and can remain a potential hazard for the environment in a similar way as current deposits. Eight ashes have been characterized by SEM-EDX and DRX, and their potential released geochemical fluxes were examined by using water and nitric acid batches, which are analyzed by ICP-OES, ICP-MS and ISE (F). Results demonstrate that water batch system is better medium than nitric acid for this study. The high and fast reactivity of these ancient ashes is mainly associated with their high content in glass. The order of magnitude of released contents of implied elements is consistent among the samples, i.e., Al>B>Fe>Zn>F>P>Mn>Ba>Sr>Li>Ti>Rb>Cu>Ni>Sb>Pb>As>Cr>V. Ash-water interaction, although infrequent in arid regions such as the Puna Region in northern Argentina, introduces rapid changes in the geochemical fluxes of elements and pH and may constitute a potential hazard for the environment. In fact, many of these elements are included in the drinking water guidelines due to their potential toxicity and may constitute potential hazards for the environment and human health.

Medieval stained glass in a Mediterranean climate: Typology, weathering and glass decay, and associated biomineralization processes and products

Abstract Medieval stained glass (13th-15th centuries) from three restoration works (Santa Maria del Mar and the Pedralbes Monastery church in Barcelona, and the Tarragona Cathedral in the northwestern Mediterranean area have been studied to characterize glass decay. Electron microprobe analysis gave evidence of two types of glass: an Na-rich type (stable, Mediterranean, of Roman-like tradition), and a K-Ca-rich type, similar to coeval Central European medieval stained glasses. The latter shows glass decay in the form of destructive (micro- and mesopitting) and constructive (patina and microcrust) glass surfaces. Nevertheless, this type of decay in the K-Ca-rich group of glasses is in terms of thickness reduction in flat glass an order of magnitude less than that commonly found in Central European countries with a continental climate. Macroscopic and microstructural studies (SEM-EDS, XRD) allowed us to identify biodeterioration decay with chemical effects similar to that for pure chemical hydration leaching and corrosion, associated with biomineralization with unspecific sulfate (gypsum, syngenite) and calcite mineralization as well as bioinduced (weddellite, whewellite, etc.) mineralization. Medieval-stained glass biodeterioration decay in the Mediterranean area shows patterns and products comparable to those developed on stone in the same historic buildings.

The red–orange patina developed on a monumental dolostone

Orange and reddish patinas developed on a dolostone of the cathedral of Lleida (Spain) have been analysed and characterised by XRD, SEM/EDX, ICP/MS, optical microscopy and Mossbauer spectroscopy. From the experimental data, a biologically induced transformation of the dolomite rock forming crystals, which form a dolomitic patina of micrite size, can be stabilised. Furthermore, the iron oxides as determined by Mossbauer spectroscopy play a role as colouring patina, together with organic matter from the bioactivity. Erosive and constructive processes, as determined through the SEM observations, lead to aesthetical and microstructural changes in the stone surface.

Acoustic barriers obtained from industrial wastes

Acoustic pollution is an environmental problem that is becoming increasingly more important in our society. Likewise, the accumulation of generated waste and the need for waste management are also becoming more and more pressing. In this study we describe a new material--called PROUSO--obtained from industrial wastes. PROUSO has a variety of commercial and engineering, as well as building, applications. The main raw materials used for this environmentally friendly material come from slag from the aluminium recycling process, dust from the marble industry, foundry sands, and recycled expanded polystyrene from recycled packaging. Some natural materials, such as plastic clays, are also used. To obtain PROUSO we used a conventional ceramic process, forming new mineral phases and incorporating polluted elements into the structure. Its physical properties make PROUSO an excellent acoustic and thermal insulation material. It absorbs 95% of the sound in the frequency band of the 500 Hz. Its compressive strength makes it ideal for use in ceramic wall building.

Mineralogical characterization of the Garumnian subbituminous lignite from the central Pyrenees by SEM-EDX, X-ray diffraction and Mössbauer spectroscopy

Abstract A full mineralogical characterization of a Garumnian subbituminous lignite found in the Pyrenees is performed and a good correlation between the mineral diagenesis and the coal rank is obtained. The mineral matter is characterized in the different sequences and analysed by optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction and transmission Mossbauer spectroscopy. Carbonates, quartz, clay minerals, sulfides and sulfates are identified and their presence is related to the diagenesis suffered by the mineral matter. Full transformation of smectite indicates temperatures > 360 °C, but the small formation of ankerite is related to low-grade metamorphism, in good agreement with the coal rank determination (Rock-Eval maximum temperature 430 °C).

Environmental geochemistry of volcanic ashes from the Southern Puna, NW Argentina

1 pagina.-- Resumen del trabajo presentado en la 19th Annual V.M. Goldschmidt Conference, V.M. Goldschmidt Conference.

Genesis of bottom vitrophyre facies in rhyolitic pyroclastic flows: a case study of syneruptive glass welding (Nuraxi unit, Sulcis, SW Sardinia, Italy)

Abstract Nuraxi unit is a near a peralkaline lithic-poor glassy pyroclastic rock with a broad outcrop in SW Sardinia. It has a constant vitrophyre at the bottom characterized by dense aggregation of glass lenticles, relative depletion of phenocrysts (respect to the overlying rest of the unit) and widespread cristobalite–anorthoclase spherulite devitrification. There is also local evidence of planar localized shear during cooling. The textural and chemical features of this vitrophyre is that expected for a syn-volcanic formation of the vitrophyre over a load compaction following cooling.