The potential mechanism of black crust development on the historic buildings in Cairo and Venice

The development of black crusts on natural stones of historic buildings is mainly related to the surrounded polluted atmosphere. The blackening of surfaces is caused, in fact, by the accumulation of air pollutants produced by human activity, especially carbon particles originating from the incomplete combustion of fossil fuel. Investigations of the chemical composition of such layers in the monuments can be the basis for planning suitable strategies for the protection and conservation of the built cultural heritage. Cairo (Egypt) and Venice (Italy) are two cities with a large amount of cultural heritage buildings; moreover, they suffer high level of air pollution. Black crust with the hosted stones from different sites in Historic Cairo, as well as samples of different archaeological sites in Venice city, were collected and analyzed by using several techniques: polarizing optical microscopy (OM), scanning electron microscopy coupled with energy-dispersive X-ray spectrometry (SEM-EDS), infrared spectroscopic techniques (FT-IR) and laser ablation inductively coupled mass spectrometry (LA-ICP-MS). The characterization of such samples provided information on the chemical composition of black crusts, the state of conservation of the substrates and the crust-stone interactions. The chemical study highlighted a different pattern of elements within the two cities. Regarding the black crusts of Cairo, results suggest that the air pollution in Cairo is mainly related to vehicular traffic. Indeed, in the city there is high vehicular traffic almost 24 h a day and the direct impact of vehicle emissions is particularly severe. Samples from the Venice show different composition in terms of heavy metals with respect to Cairo that can be explained with the emission from several industries sited in the near industrial center of Porto Marghera and Island of Murano. Moreover, the fuels used for marine transportation, which is abundant into the area, have a slight different fingerprinting in terms of metals with respect to the vehicles

The assessment of the carbonaceous component in black crusts damaging the stone surfaces of historical monuments (from Trevi fountain Roma to square San Marco Venice)

The issue of conservation of the monumental heritage is mainly related to atmospheric pollution that causes the degradation of stone surfaces. Black crusts can be formed as a result of different chemical and physical reactions between the stone surface and environmental factors (such as gaseous pollutants and aerosol particulate matter, PM). These black layers present on the stone monuments reflect the composition of the aerosol particulate matter to which the surfaces are exposed. In particular elemental carbon (EC, also known as black carbon, typically emitted by combustion processes) is the PM component responsible for the characteristic black color of the crusts where it is embedded together with calcium sulphate due to the conversion of calcium carbonate, the main constituent of the stone. Organic carbon (OC) represents the other carbonaceous component of PM and it is present in the black crusts, too. It is of both primary or secondary origin and is linked to numerous sources (traffic, heating plants, biomass burning, etc.). A deep knowledge of the crust composition in terms of OC and EC optical properties is mandatory in order to get information on the sources responsible for the surface darkening. OC/EC in PM samples are generally quantified by a reference method (TOT, Thermal Optical Transmittance) not suitable for the analysis of these components in the crusts. A new approach for OC/EC quantification based on a thermal protocol and including CHN and TGA analyses, has been set-up. The method validation has been performed analyzing suitable reference standard samples prepared by mixing different chemical species in order to simulate the composition of the black crusts present on the monument surfaces. Real samples of black crusts coming from historical monuments placed in Rome, Milan and Venice have been analyzed

Study of The Corrosion Processes On Roman And Byzantine Glasses From Northern Tunisia

The present investigation focuses on some glass objects among those discovered in an area around the ancient city of Thugga in northern Tunisia, particularly flourishing during the Roman and Byzantine periods (1). The Late Roman-Byzantine time is not characterised by elaborate vessel shapes derived from precious metal prototypes, but rather by simpler multifunctional forms, as beakers, goblets, and dishes with similar features in the whole Mediterranean world. Also the glass composition seems to change between the 4th and the 5th century, turning to a yellowish-green or olive green colouration of the glass instead of the typical Roman blue-greenish colouration of earlier times. This new glass colouration varies further drastically in the 7th century, when a characteristic light blue-turquoise glass becomes the most widespread. A complete chemical characterization of these objects was carried out in a previous study (2) aimed to investigate the production technology including the chromophores responsible for the different shades. In the present work we have investigated the degradation and corrosion processes affecting some of these shards. It is worth to note that to ascertain the composition of the glass surfaces the analyses have been carried out by means of non-destructive techniques such as XPS (X-ray photoelectron spectroscopy), SEM-EDX (scanning electron microscopy coupled with energy dispersive X-ray analysis) and laser-ablation ICP-MS ((Inductively Coupled Plasma \u2013 Mass Spectrometry)

Effects of different sources of air pollution on the carbonate stone surface of relevant European monuments

This contribution focuses on spectrometric analyses carried out on black crust samples, collected from buildings and churches belonging to the European built Heritage, i.e., the Corner Palace in Venice (Italy), the Cathedral of St. Rombouts in Mechelen (Belgium), the Church of St. Eustache in Paris (France) and the Tower of London (United Kingdom). Such monuments, all built in carbonate stones, were selected for their historic and artistic relevance, as well as for their location in different urban contexts (exposed to intense vehicular traffic or pedestrian areas). For a complete characterization of the black crusts, an approach integrating complementary techniques was used, including optical (OM) and scanning electron microscopy coupled with energy-dispersive X-ray spectrometry (SEM-EDS), Fourier transform infrared spectroscopy (FT-IR) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The complete characterization of the damage layers provided information on their chemical composition, the state of conservation of the underlying substrates and the interactions between crusts and stones. In particular, the geochemical study in terms of trace elements revealed that all crusts are enriched in heavy metals (As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sb, Sn, Ti, V, and Zn) compared to substrates. The different concentrations of such elements in all analyzed crust samples can be ascribed to several factors, such as: height of sampling, morphology of the sampled surfaces (vertical or horizontal), exposure to atmospheric agents, exposure to direct (road or boat traffic) or indirect (industries) sources of pollution, accumulation time of pollutants on the surfaces, wash out and particulate air pollution. Specifically, the crusts collected at lower heights (some samples of the Corner Palace, Cathedral of St. Rombouts and Tower of London) resulted to be mainly influenced by mobile sources of pollution (vehicular or boat traffic), while samples taken at higher heights (Church of St. Eustache and some samples of the Corner Palace) are generally mostly affected by stationary combustion sources. In some cases, the detailed analysis of multilayered crusts (Palazzo Corner) contributed to recognize the variation of combustion sources responsible for the deterioration of surfaces over time. In addition, the possibility of analyzing altered portions of the substrate (Tower of London) permitted to observe that some elements (Zn, Cu and Ni) show concentrations similar and, sometimes, higher than the overlying crusts. This result can be explained by the geochemical mobility of such elements (at specific environmental conditions), which accelerate the process of sulfating, rapidly creating new layers of crust In conclusion, the study of black crusts and altered substrates in terms of trace elements may provide information useful to understand the influence of the pollutants in the genesis of such degradation forms

The assessment of the carbonaceous component in black crusts damaging the stone surfaces of historical monuments.

The issue of conservation of the monumental heritage is mainly related to atmospheric pollution that causes the degradation of stone surfaces. Black crusts can be formed as a result of different chemical and physical reactions between the stone surface and environmental factors (such as gaseous pollutants and aerosol particulate matter, PM). These black layers present on the stone monuments reflect the composition of the aerosol particulate matter to which the surfaces are exposed. In particular elemental carbon (EC, also known as black carbon, typically emitted by combustion processes) is the PM component responsible for the characteristic black color of the crusts where it is embedded together with calcium sulphate due to the conversion of calcium carbonate, the main constituent of the stone. Organic carbon (OC) represents the other carbonaceous component of PM and it is present in the black crusts, too. It is of both primary or secondary origin and is linked to numerous sources (traffic, heating plants, biomass burning, etc.). A deep knowledge of the crust composition in terms of OC and EC optical properties is mandatory in order to get information on the sources responsible for the surface darkening. OC/EC in PM samples are generally quantified by a reference method (TOT, Thermal Optical Transmittance) not suitable for the analysis of these components in the crusts. A new approach for OC/EC quantification based on a thermal protocol and including CHN and TGA analyses, has been here proposed. The method validation has been performed analyzing suitable reference standard samples prepared by mixing different chemical species in order to simulate the composition of the black crusts present on the monument surfaces. In addition the characterization of OC optical properties with UV-visible spectrometry has been performed, to understand the role of light absorbing carbon (i.e. brown carbon) on surface stone darkening. The chemical composition of OC was further investigated with Fourier Transform infrared spectrometry (FT-IR) to identify the contribution of the different organic functional groups to the ageing/browning of stone surfaces. This research aims to get a new simple method for the evaluation of the carbonaceous component of the black crusts which are formed on carbonate stone surfaces. The protocol has been applied to some real samples of black crusts of different provenance

Mineralogical, petrographic and chemical analyses for the study of the canvas "Cristo alla Colonna" from Cosenza, Italy : a case study

A multi-technique study on materials used for the painting "Cristo alla Colonna" by Luigi Bria (private collection, Cosenza, Italy) was carried out for the first time during the restoration plan. Pigments, binder media and raw materials used for the application of ground and priming layers were studied using optical (OM) and electronic microscopy equipped with energy dispersive spectroscopy qualitative microanalysis (SEM-EDS), infrared spectroscopy (FTIR) and gas chromatography coupled with mass spectrometry (GC/MS). The goal of this study was to characterize this canvas and to set up a scientific aid and guide for its restoration, taking into account the, severe damage not exclusively due to natural decay processes. Our data can provide information about historical and stylistic background as well as advises for correct planning of the cleaning procedures. Riassunto - II dipinto su tela "Cristo alla Colonna", opera di Luigi Bria (collezione privata, Cosenza, Italia), \ue8 stato sottoposto, durante le fasi di restauro, per la prima volta ad indagine strumentale tramite varie tecniche analitiche. I pigmenti, i leganti ed altri materiali utilizzati per la sua realizzazione sono stati analizzati tramite microscopia ottica (OM), microscopia elettronica e microanalisi tramite spettrometria a dispersione di energia (SEM-EDS), spettroscopia infrarossa (FTIR) e gascromatografia accoppiata spettrometria di massa (CG/MS). Lo scopo del lavoro \ue8 stato quello di offrire una caratterizzazione dell'opera pittorica, nonch\ue9 fornire un supporto scientifico ad un un corretto intervento di restauro su un'opera fortemente degradata. I risultati hanno permesso di fornire informazioni di natura storico-artistico nonch\ue9 informazioni utili ad un corretto intervento di pulitura della tela oggetto di questo studio

Consolidating Properties Of Regalrez 1126 And Paraloid B72 Applied To Wood

This study is aimed at an assessment of the properties oftwopolymeric products applied toNorwayspruce (Picea abies) and White poplar (Populus alba)woodspecies. It contributes to ongoing research experiments on the consolidating properties of two synthetic resins and their potential synergic action on wood, resulting from their different interaction with the substrate: Paraloid B72 and Regalrez 1126. Experiments were carried out on a series of samples of the two wood varieties. The consolidants were applied alone and one after the other, with one coat of Regalrez and then one of Paraloid. Porosity and variations in pore size distribution were ascertained by mercury intrusion porosimetry (MIP). Colorimetric and IR spectroscopic measurements were also taken before and after aging by solar radiation and freeze/thaw cycles, to verify the possible slowing of photodegradation of the treated wood and the consolidating resistance. Results confirm that both products penetrate the wood with a different behaviour. After double treatment with Regalrez + Paraloid, a significant advantage was observed in terms of mechanical resistance and pore size distribution, although no advantages as regards resistance to photo-oxidizing processes or colour changes were observed

Diagnostic analysis of bricks from the underwater archaeological site of Baia (Naples, Italy): Preliminary results

In this multidisciplinary contribution, several diagnostic tests were carried out in order to characterize the archaeological materials, as well as the alteration and degradation products, present in the submerged archaeological site of Baia (Naples, South Italy). Founded by the Romans in the 1st century B.C., this archaeological area represents one of the greatest evidence of Roman architecture and it includes ancient ruins whose structures range from maritime villas and imperial buildings. Fragments of bricks belonging from walls of a monumental villa, called Villa con ingresso a protiro, were studied with different and complementary techniques. In particular, polarized optical microscopy and X-ray diffraction were performed in order to characterize the raw materials employed for their production, while to evaluate the state of conservation and identify the biodeteriogen agents, samples were studied under a stereomicroscope and scanning electron microscopy. Analytical data highlighted that: a) different types of bricks were used in the ancient roman city of Baia; b) the presence of several degree of biological colonisation is mainly correlated to the type of temper used for their production