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Black crusts (BCs) are one of the most critical alteration forms found on stones belonging to architectural heritage. Since they could be considered as passive samplers of atmospheric pollution, it would be plausible to establish relations between the air contamination and the BCs. With this aim, we have characterized BCs collected on historic buildings from two Spanish cities (Granada and Vigo) with different polluted atmospheres, as well as formed on stone substrates of varied mineralogy and texture. Likewise, in order to assess the impact of the atmospheric pollutants on the growth of BCs, quartz fiber filters were used as surrogate substrates and placed nearby the studied buildings to collect and analyze the aerosol particulate matter (PM). To this end, an array of complementary analytical techniques was used to evaluate the mineralogy, chemical composition, and texture of the BCs and to establish the correlation with the ions, OC (organic carbon), and EC (elemental carbon) detected in the PM on the quartz fiber filters. As result, BCs developed on carbonate substrates from Granada show more complex structure than those from Vigo, which are thinner because of frequent rain episodes. In both cities, NaCl, Pb-Cl, and Ca-Cl-rich particles, Ca-phosphate particles and clusters of Ba-sulfate-rich particles were detected. However, metal-rich rounded particles were more abundant in Granada's BCs, including soot particles. BCs from Granada were richer in carbonaceous components (OC and EC) than the Vigo's BCs. Although in the filters PM did not show EC-mainly due to traffic-, in the BCs from both locations OC and EC were detected. Therefore, this different composition was related to the mineralogy of the stones and the higher pollution of Granada in contrast to the industrial and sea-exposed city of Vigo., (© 2021. The Author(s).)

The surface coating present on a marble Piety dating to the Renaissance period and stored at the Castello Sforzesco-Museum of Ancient Art (Milan, Italy) was studied and chemically characterised. For this purpose, both portable non-invasive (XRF and colorimetric measurements) and micro-invasive techniques (FTIR-ATR and SEM-EDS), have been applied. The statue has been recently submitted to a restoration, since its surface appeared dark and yellowed, before an exhibition at the Louvre Museum and the original appearance of the marble surface recovered thanks to the surface coating removal. Through the analytical characterisation carried out before and after the marble cleaning, the presence of a degradation layer composed by gypsum was evidenced on the stone. The origin of this layer is ascribable to the exposure of the statue to outdoor environment and interaction with atmospheric pollution. The chemical nature of the coating applied at the end of nineteenth century also responsible for the surface alteration was hypothesized. [ABSTRACT FROM AUTHOR]

This research deals with the characterization of black crusts collected from the Dome of Monza (Milan, Italy). Air pollution is responsible for the degradation of historical buildings surfaces. In urban and industrial areas, the degradation process is accelerated, due to carbonaceous particles and heavy metals emitted by combustion processes which contribute to the formation of black crust (BCs). In this study the characterization of BC was performed using different analytical techniques such as: HRSEM-EDX, IC, LA-ICP/MS and digital image analysis. In particular, the research focused on the study of "heavy metals" which contribute to the identify the main sources of pollution responsible for the surface's deterioration over time. BCs variability in composition also depends on the exposure of the analyzed surfaces. [ABSTRACT FROM AUTHOR]

This paper deals with the analysis of black crust coming from the statue of Oceanus belonging to the Fontana di Trevi (Rome). This monument is undoubtedly one of the main touristic attractions of Rome. During the restoration held between 2014 and 2015, some diagnostic analyses had been carried out. It has been highlighted that the sheltered surfaces suffer the formation of black crust, especially on the marble statues. The possibility to sample those degradation products, together with the unaltered substrate, represented an excellent opportunity to characterize the marble itself, to assess the impact of the urban air pollution on the stone material, and to detect the pollutant on a precise timescale. In fact, it is known that the previous restoration of the fountain had been carried out between 1989 and 1991 then, information about the air pollution over the last 25 years can be highlighted, because it has been proved that black crusts act as passive samplers of pollution. In order to fully characterize those samples, several techniques were used, including optical and scanning electron microscopy, X-ray diffraction, laser ablation inductively coupled plasma mass spectrometry, infrared spectroscopy and ion chromatography. Furthermore, a new methodology based on CHN (Carbon, Hydrogen, Nitrogen) analysis has been developed for the quantification of the two main constituents of the carbonaceous fraction present in the black crusts, i.e. OC (organic carbon) and EC (elemental carbon). This integrated approach proposed in the present study allowed us to gain information about the mineralogical phases and the elements within the crusts and at the crust-substrate interface, giving the possibility to identify the pollution sources causing the stone decay within the monument. [ABSTRACT FROM AUTHOR]

Nowadays, high-time resolved aerosol studies are mandatory to better understand atmospheric processes, such as formation, removal, transport, deposition or chemical reactions. This work focuses on PM10 physical and chemical characterisation with high-time resolution: elements (from Na to Pb), ions and OC/EC fractions concentration were determined during two weeks in summer and two in winter 2006 with 4-hours resolution. Further measurements aimed at hourly elemental characterisation of fine and coarse fractions and at the determination of particles number concentration in the 0.25–32 μm size range in 31 bins. The chemical mass closure was carried out in both seasons, enhancing intra-day differences in PM10 composition. In Milan, the highest contribution came from organic matter (34% and 33% in summer and winter, respectively); other important contributors were secondary inorganic compounds (16% and 24% in summer and winter, respectively) and, in summer, crustal matter (14%). Temporal trends showed strong variations in PM10 composition during contiguous time-slots and diurnal variations in different components contribution were identified. Moreover, peculiar phenomena, which would have hardly been detected with 24-hours samplings, were evidenced. Particles removal due to precipitations, aerosol local production and long range transport were studied in detail. [ABSTRACT FROM AUTHOR]

Abstract: Fireworks are one of the most unusual sources of pollution in atmosphere; although transient, these pollution episodes are responsible for high concentrations of particles (especially metals and organic compounds) and gases. In this paper, results of a study on chemical–physical properties of airborne particles (elements, ions, organic and elemental carbon and particles size distributions) collected during a fireworks episode in Milan (Italy) are reported. Elements typically emitted during pyrotechnic displays increased in 1h as follows: Sr (120 times), Mg (22 times), Ba (12 times), K (11 times), and Cu (6 times). In our case study, Sr was recognised as the best fireworks tracer because its concentration was very high during the event and lower than, or comparable with, minimum detection limits during other time intervals, suggesting that it was mainly due to pyrotechnic displays. In addition, particles number concentrations increased significantly during the episode (up to 6.7 times in 1h for the 0.5

COVID-19 has reduced tourism in both museums and historical sites with negative economic effect. The wellbeing and good preservation of monuments is a key factor to encourage again tourism. Historical monuments exposed to outdoor pollution are subjected to well known degradation phenomenon including the formation on their surface of black crusts (BCs) causing blackening and deterioration of the monuments and, as a consequence, a worst fruition by the visitors. The aim of this research is the development and validation of a novel method to characterize and quantify the various components present in the black crusts. SO 2 together with the carbonaceous fraction (i.e. OC, organic carbon, and EC, elemental carbon) represent the main atmospheric pollutants involved in the process of BCs formation which consists in the partial transformation of the carbonate substrate into gypsum where black particles are embedded. A new methodology based on the use of TGA/DSC (Thermogravimetric Analysis/Differential scanning calorimetry) and CHN (Carbon, Hydrogen, Nitrogen) analysis was set up allowing to determine organic carbon and elemental carbon together with other components such as gypsum. Four standard mixtures simulating BCs composition were prepared and analysed by the set-up methodology. The new procedure was subsequently applied to study real BCs samples taken from monuments and historical buildings placed in cities heavily affected by atmospheric pollution and by PCA (principal component analysis) their main features, from the point of view of carbonaceous fraction, were highlighted. • Historical monuments exposed to outdoor pollution are subjected to deterioration. • Degradation phenomenon known as black crusts (BCs). • New method for the quantification of organic and elemental carbon within BCs. • A relation exists between air pollution and BCs composition. • Pollutants mitigations policies are mandatory to preserve cultural heritage. [ABSTRACT FROM AUTHOR]

In the last decades, many researchers investigated the relation between environmental pollution and the degradation phenomena on the built heritage, because of their rapid increase and growing harmfulness. Consequently, the identification of the main pollution sources has become essential to define mitigation actions against degradation and alteration phenomena of the stone materials. In this way, the present paper is focused on the study of the effect of air pollution on archaeological buildings in Historic Cairo. A multi-methodological approach was used to obtain information about the chemical composition of examined black crusts and to clarify their correlation with the air pollution, specifically the heavy metals and the carbonaceous fraction, their main sources, and their impact on the state of conservation of the studied sites. All specimens were characterized by polarized optical microscopy (POM), X-Ray Diffraction (XRD), Electron Probe Micro Analyser coupled with energy dispersive X-ray spectrometry (EPMA-EDS), laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and Thermo-gravimetric analysis (TGA). The study conducted on heavy metals and carbonaceous fraction showed that the greatest contribution of the accumulation of pollutants is attributable to vehicular traffic and industrial activities, the main polluting sources in Cairo city. Furthermore, the comparison with other studies conducted on the carbonaceous fraction in the black crusts coming from both European and non-European cities, has allowed to discriminate the contribution of the primary and secondary polluting sources. Finally, the correlation of the data obtained on the heavy metals and the carbonaceous fraction allowed to formulate important hypothesis about the processes of sulphation. Unlabelled Image • Black crusts from Cairo have been analysed by several techniques. • The effect of urban air pollution on the monuments of Cairo has been investigated. • The methodology allowed identification of pollution sources in the black crusts. [ABSTRACT FROM AUTHOR]