1,721,058 research outputs found
Cultural heritage and aerobiology. Methods and measurement techniques for biodeterioration monitoring
No full textQuantitative data on carbon fractions in interpretation of black crusts and soiling on European built haritage
No full textThere is wide recognition of the pivotal role of gaseous multi-pollutants and aerosols in determining the damage encountered on monuments and built cultural heritage in European cities. The main effects of atmospheric pollution on building materials in urban areas are soiling and black crusts formation. Furthermore, anthropogenic pollutants have changed over time, and attention now focuses on the contribution to damage layer formation of particles, particularly soot/carbonaceous ones, whose importance in determining air quality in urban areas is steadily increasing. However, the analytical tools and currently available data remain inadequate to attain a correct approach to black crust characterization and identification of causes of damage: there is a pressing need to discriminate and quantify the pollutant amounts, particularly that of carbonaceous aerosols, which deposit and accumulate on monuments and building surfaces, giving rise to surface blackening. The present work makes a contribution to filling this gap by presenting data on carbon fraction speciation and concentrations, obtained from the application of a specific analytical methodology on black surface layers in different European cities. As well as providing a preliminary data base, the information obtained turn out to offer some insight into past, present and future pollutant sources contributing to the damage on the built heritage
The Corner Palace in Venice: a case of study on stone damage in urban area
No full textIn order to evidence both the products of damage reactions and the components due to atmospheric deposition, and to identify the pollutant sources, specimens of damaged stone, consisting of surface black crusts with underlying unaltered material, were sampled on the blackened façade of the Corner Palace on the Canal Grande in Venice and submitted to a combination of physico-chemical analytical techniques. The samples were observed in thin section under optical microscope, and the damaged surface was investigated using a scanning electron microscope. X-ray diffractometric analyses, gravimetric and differential thermal analyses, and ion chromatographic analyses were performed in order to identify the main crystalline species, quantify gypsum and carbonate, and measure the anion concentrations, respectively. Finally, the carbon fractions were discriminated and measured following a chemical-thermal methodology specifically developed for damage layer specimens. The data obtained indicate gypsum as the main product of damage processes occurring due to wet and dry SO2 deposition. The burning of fossil fuels produces gases, smoke and particulate carbonaceous matter that deposit on building surfaces and react with the underlying calcareous materials forming the damage layer. Carbonaceous particles have a catalytic effect on CaSO4·2H2O formation and the ensuing surface blackening on building exteriors
Carbon content evaluation of damage layer in a an urban Mediterranean site: the Vittoriano Monument in Rome
No full textThe work is a study on the carbon content and origin of damage layers on European monuments aimed to improve knowledge on the role of black crusts in stone decay, their relationship with the carbonaceous particle content of the atmosphere, and surface blackening rate
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Oxalate Patinas on Stone Monuments in the Venetian Lagoon: Characterization and Origin
No full textCalcium oxalate patinas have been sampled on architectural elements of two ancient churches located on Torcello Island (Venetian Lagoon) and subsequently analyzed. The site had been selected presenting patinas of exceptional amount and thickness, elsewhere generally found as thin alteration layers covering stone surfaces or within black crusts on monuments in urban environments. Optical and mineralogical analyses suggest that these patinas are not the result of a simple deposition process, but originate as surface "transformations" of the substrate, and are mainly composed of dihydrate calcium oxalate (weddellite) and gypsum. Among the experimental techniques, isotope analyses (C and S) have been specifically carried out aiming at achieving a better understanding of their origin and possible causes of formation. The observed carbon isotopic fingerprint reveals in fact a strong biological fractionation recorded in the oxalate patina (δ13C ranging from -22.3‰ to -28.0‰), almost exclusively attributable to C3 pathway photosynthesis processes. Slightly negative sulfur isotope ratio values seem to be inversely correlated with patina exposure to atmospheric agents and pollutants. The results obtained prove that calcium oxalate originates from a biomineralization process induced by lichen colonization in specific environmental conditions
Analisi isotopiche su patine di ossalato di calcio
No full textLe patine di ossalato di calcio rappresentano una delle forme di alterazione più conosciuta dei monumenti lapidei. In questo lavoro, alle analisi di routine sulle patine di ossalato di calcio campionate alla superficie di murature storiche dell'isola di Torcello (VE), sono state associate analisi isotopiche
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