Biological colonization and biodeterioration of architectural ceramic materials: An overview

The Grande Albergo Ausonia & Hungaria (Venice Lido, Italy) has an Art Nouveau polychrome ceramic coating on its facade, which was restored in 2007. Soon after the conservation treatment, many tiles of the facade decoration showed coloured alterations putatively attributed to the presence of microbial communities. To confirm the presence of the biological deposit and the stratigraphy of the Hungaria tiles, stereomicroscope, optical and environmental scanning electron microscope observations were made. The characterisation of the microbial community was performed using a PCR–DGGE approach. This study reported the first use of a culture-independent approach to identify the total community present in biodeteriorated artistic tiles. The case study examined here reveals that the coloured alterations on the tiles were mainly due to the presence of cryptoendolithic cyanobacteria. In addition, we proved that the microflora present on the tiles was generally greatly influenced by the environment of the Hungaria hotel. We found several microorganisms related to the alkaline environment, which is in the range of the tile pH, and related to the aquatic environment, the presence of the acrylic resin Paraloid B72® used during the 2007 treatment and the pollutants of the Venice lagoon.

Microbial Deterioration of Artistic Tiles from the Façade of the Grande Albergo Ausonia & Hungaria (Venice, Italy)

5 paginas.-- 2 figuras.- 1 tabla.-- 16 referencias.-- Conferencia presentada en Proceedings of International Course Ceramic Material in Building Heritage: Conservation problems and Intervention.-- that took place In Madrid the 29th and the 30th of June, 2016 at the Instituto de Ceramica y Vidrio (lCV-CSIC), Madrid (Spaln).

Biological colonization and biodeterioration of architectural ceramic materials

Microbial communities on deteriorated artistic tiles from Pena National Palace (Sintra, Portugal)

Titania (TiO2) minerals are minor diagenetic phases in many sandstone–shale successions, but the conditions of Ti mobility and titania authigenesis are poorly known. Here, new modes of occurrence of authigenic titania minerals, filling pores and replacing phytodetritus, are documented from Lower Cretaceous prodeltaic sandstones in the offshore Scotian Basin of southeastern Canada. Textural relationships suggest that titania minerals formed at the same time as kaolinite, most commonly below lowstand sequence boundaries, related to flux of meteoric water. Such authigenic titania is most abundant in thin-bedded sandstones interbedded with thick prodeltaic mudstone in which fine-grained detrital Ti-rich minerals are concentrated. Textures in titania that has replaced uncompacted phytodetritus suggest microbial mediation in near-surface eodiagenesis. Eogenetic titania is enriched in phosphorus (∼ 0.6% P2O5) and may co-occur with authigenic fluorapatite and crandallite crystals. Such titania resulted from prolonged flow of meteoric water that dissolved P from apatite and feldspar, thereby enhancing Ti solubility. In basins with supply of immature sediment from granitic terranes and important diagenesis by meteoric water, the assumption that Ti is an immobile element and that rutile or other titania minerals are exclusively of detrital origin may not be valid. Probable mesodiagenetic titania has low P content, suggesting that Ti mobility under these conditions was facilitated by some other agent, probably organic acids. The results of this study illustrate that even in cases where titania minerals are volumetrically insignificant, their microtextures and trace-element chemistry can provide important insights into the character of fluid flow during diagenesis of siliciclastic rocks.

Authigenesis of Titania Minerals and the Mobility of Ti: New Evidence from Pro-Deltaic Sandstones, Cretaceous Scotian Basin, Canada

Elemental behaviour, during the process of weathering of glazed sekishu roof-tiles affected by Lecidea s.lat. sp. (a crustose lichen), was investigated using optical and fluorescence microscopy, field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy. Sekishu roof tiles have an opaque reddish brown glaze on their surfaces which consist of an alkali feldspar-type X-ray amorphous glass recrystallized at 1200°C. Optical and fluorescence microscopy revealed the presence of corrosion pits (at a depth of ∼50 μm) at the lichen-glaze interface. Elemental mapping by FE-SEM identified the concentrations of Ti and Fe in the section of the glazed tile analysed. The behaviour of C was correlated with those elements, suggesting the possibility of biomineralization.

Elemental behaviour during the process of corrosion of sekishu glazed roof-tiles affected by Lecidea s.lat. sp. (crustose lichen)

The mineralogy of the glazed surfaces of Japanese sekishu roof tiles covered by a crustose lichen – Lecidella asema (Nyl.) Knoph & Hertel – was investigated using transmission electron microscopy (TEM). The study sought to identify the Ti-Fe mineral observed as a low concentration of Ti and Fe in a previous study of the glazed surfaces of the same roof tile. The TEM analysis revealed that: (1) a thin layer of the Ti-Fe mineral pseudobrookite exists on the glaze surface; (2) the pseudobrookite consists of well-ordered single crystals, continuously and widely distributed on the glaze surface.

Nanoscale pseudobrookite layer in the surface glaze of a Japanese sekishu roof tile

The alteration mechanism of biotite in granitic rock caused by crustose liche \"Porpidia\" was investigated by means of X-ray diffraction, optical microscope, EPMA and electron microscope with EDX. Vertical thin sections of lichen-rock interface were observed by a scanning electron microscope to make clear the physico-chemical phenomenon caused by lichens. The contact surfaces between lichen and a biotite were physically observed with this section, and were further investigated chemically by EPMA. As a result, physical destruction of biotite grains by lichen thallus was observed, and the formation of iron oxide or hydroxide was recognized. The chemical compositions of some parts of the biotite crystal were analyzed by EPMA, such as altered parts closed to lichen thallus, altered parts far from lichen thallus and fresh parts. Consequently, comparison of the different parts revealed increase in Si02 content on one hand and decrease in FeO and 1 (20 on the other hand from the fresh biotite crystal throughout the licheni alteration. Due to the lower solubility of Si02 and higher solubility of Fe203 and Al2O3 from minerals under strong acid condition, which is formed by lichen thallus, it seems that Si4+ content in tetrahedral site is increased by cation exchange. Also due to the low pH and activity of high molecular weight polymers, the possible weakening of the iron-xygen bonds will lead to the dissolution of Fe 3+ ions. Consequently, it is likely that, due to the increasing negative charge of biotite layers with dissolutio of Fe 3+, dissolution of K+ will be disturbed. Vermiculite-like minerals in biotite formed with the actio or effect of lichen were identified by quantitative chemical analysis as wt% of oxides and calculation of structural formulae on the basis of 22 oxygen atoms per unit cell.

Katsuaki Watanabe

Papers

Elemental behaviour during the process of corrosion of sekishu glazed roof-tiles affected by Lecidea s.lat. sp. (crustose lichen)

Nanoscale pseudobrookite layer in the surface glaze of a Japanese sekishu roof tile

Alteration mechanism of biotite in granitic rock caused by crustose lichen "porpidia"

Fluoride Content in Biotite from Hiroshima Granite

Dissolution Process of Sekishu Roof Tiles Affected by Crustose Lichen Lecidea sp. Grown on Their Surfaces