Microbial carbonate precipitation in construction materials: A review

A new Palaeolithic discovery: tar-hafted stone tools in a European Mid-Pleistocene bone-bearing bed

Analytical applications of Laser Induced Breakdown Spectroscopy (LIBS), namely optical emission spectroscopy of laser-induced plasmas, have been constantly growing thanks to its intrinsic conceptual simplicity and versatility. Qualitative and quantitative analysis can be performed by LIBS both by drawing calibration lines and by using calibration-free methods and some of its features, so as fast multi-elemental response, micro-destructiveness, instrumentation portability, have rendered it particularly suitable for analytical applications in the field of environmental science, space exploration and cultural heritage. This review reports and discusses LIBS achievements in these areas and results obtained for soils and aqueous samples, meteorites and terrestrial samples simulating extraterrestrial planets, and cultural heritage samples, including buildings and objects of various kinds.

Laser induced breakdown spectroscopy for elemental analysis in environmental, cultural heritage and space applications: a review of methods and results.

In the present work the application of laser cleaning in the conservation of cultural assets is reviewed and some further developments on the interpretation of the associated laser-material interaction regimes are reported. Both the state of the art and new insights mainly focus on systematic approaches addressed to the solution of representative cleaning problems, including stone and metal artifacts along with wall and easel paintings. The innovative part is entirely dedicated to the extension of the application perspective of the Nd:YAG lasers by exploiting the significant versatility provided by their different pulse durations. Besides extensively discussing the specific conservation and physical problems involved in stone and metal cleaning, a significant effort was also made to explore the application potential for wall and easel paintings. The study of the latter was confined to preliminary irradiation tests carried out on prepared samples. We characterized the ablation phenomenology, optical properties, and photomechanical generation associated with the irradiation of optically absorbing varnishes using pulse durations of 10 and 120 ns. Further results concern the nature of the well-known problem of the yellowish appearance in stone cleaning, removal of biological growths and graffiti from stones, cleaning of bronze and iron artifacts and related aspects of laser conversion of unstable minerals, removal of calcareous stratification from wall paintings, and other features.

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Laser cleaning in conservation of stone, metal, and painted artifacts: state of the art and new insights on the use of the Nd:YAG lasers

Novel analytical methods for characterising binding media and protective coatings in artworks.

Organic and inorganic consolidants display an unsatisfying behavior particularly in the case of artifacts highly porous stone in presence of soluble salts and water. Therefore, in this study of the mechanism for the consolidating action of ammonium oxalate, treatment with ammonium phosphate was considered. This product is very promising due to its high water solubility, absence of toxicity, and very low solubility of the reaction product, calcium phosphate. Tests were conducted on two kind of limestone applying a cellulose poultice with 5% water solutions of the following agents: diammonium hydrogen phosphate (DAHP) (pH 8.0), ammonium dihydrogen phosphate (ADHP) (pH 5.6–6.0), and ammonium-dihydrogen phosphate(ADHP) equilibrated with NH3 (30%) up to pH 7.0–8.0. Contact times of 4, 8, and 17 hours were used. The consolidating effect was evaluated with other parameters (water capillary absorption capacity, color variation), by comparison with the untreated samples and with the ammonium oxalate treatment. The...

Ammonium Phosphates as Consolidating Agents for Carbonatic Stone Materials Used in Architecture and Cultural Heritage: Preliminary Research

GC-MS characterization of paint varnishes

The use of microorganisms for the removal of sulphates on artistic stoneworks

Among the different pathologies of stone materials, the presence of sulphates and nitrates is the most frequent. In addition, the presence of organic matter on artistic stoneworks can be attributed to inadequate past restorations, to the lysis of microbial cells of the primary surface colonisation, and to the presence of hydrocarbons originating from oil combustion. The latter appears to be a serious danger for the preservation of artworks themselves. Until today, chemical and physical techniques have been largely used to remove pollutants and residual substances from works of art by using surfactants and solubilizing agents. We developed a multiple bioremediation system for the biological removal of sulphates, nitrates and organic matter present on artistic stoneworks utilizing microbial cultures carefully selected and grown on a suitable support. The study consisted of: screening of microorganisms in order to select cultures with a high sulphate-reducing, denitrifying and biodegradative ability of organic matter; setting up of simulated laboratory tests with stone samples artificially enriched with nitrates, sulphates and organic matter; testing appropriate inert matrices on which to immobilize the selected bacterial strains; and testing sulphate, nitrate and organic matter removal from artificially enriched stones as well as from naturally degraded artworks. Sepiolite was used to develop bacterial biofilms with a high active biomass per cm3. However, in order to eliminate or reduce interferences and the release of undesirable ions and contaminant trace elements, Hydrobiogel97, a mixture of polyacrylamide at different molecular weights, appears to be a good carrier. As regards nitrate removal, Pseudomonas aeruginosa and P. stutzeri were selected for their high denitrifying activity. Treatment with colonised sepiolite of stone specimens artificially enriched with nitrates and of real stone samples showed that, after 30 h, a very high percentage (90% and 88%, respectively) of nitrate was removed. For sulphate removal, Desulfovibrio vulgaris and D. desulfuricans were selected and tested in liquid cultures, on stone specimens artificially enriched with sulphates, and on real marble samples. The highest removal efficiency (81%) was achieved on real marble samples after 36 h of treatment. Finally, for the removal of organic matter, bioremediation tests on ancient frescoes (XV century) located near Pisa, altered by the presence of undesirable residual collagen, were carried out before intervention with traditional restoration. The treatment with pure cultures of P. stutzeri, at a temperature of 17–22°C, showed the complete removal of collagen after 8 h. The results confirm the potentiality of bioremediation processes as soft innovative technology based on the use of microorganisms and their metabolic activity in the recovery of degraded artworks.

Mauro Matteini

Papers

Ammonium Phosphates as Consolidating Agents for Carbonatic Stone Materials Used in Architecture and Cultural Heritage: Preliminary Research

GC-MS characterization of paint varnishes

The use of microorganisms for the removal of sulphates on artistic stoneworks

Bioremediation of Cultural Heritage: Removal of Sulphates, Nitrates and Organic Substances

Laser cleaning methodology for the preservation of the Porta del Paradiso by Lorenzo Ghiberti