Maite Maguregui

Analytical diagnosis methodology to evaluate nitrate impact on historical building materials.

Nitrate salts have become of greater importance in the decay of materials from historical buildings due to changes in the environment. This work presents an analytical diagnosis methodology to evaluate the impact of nitrate salts in mortars and bricks, combining noninvasive and microdestructive analytical techniques together with chemometric and thermodynamic data analyses. The impact of nitrate salts cannot be well ascertained if other soluble salts are not taken into account. Therefore, the principal results from this work relate to nitrate salts but some results for other kinds of salts are included. Data from Raman microprobe spectroscopy and micro X-ray fluorescence (μ-XRF) are used to characterise the original composition and a first approximation of the nature of the decay compounds, mainly nitrates. The soluble salts are extracted and the anions and cations are quantified by means of ion chromatography with conductimetric detection for anions/cations and inductively coupled plasma mass spectrometry (ICP/MS) for cations. The values obtained allow two different data treatments to be applied. First, chemometric analysis is carried out to search for correlations among anions and cations. Second, thermodynamic modelling with the RUNSALT program is performed to search for environmental conditions of soluble salt formation. All the results are finally used to diagnose the impact of nitrates.

Spectroscopic evaluation of the environmental impact on black crusted modern mortars in urban–industrial areas

AbstractA multianalytical characterisation of black crusted modern construction materials from buildings located in the Bilbao Metropolitan area (North Spain) was carried out. According to the mineral composition determined by Raman spectroscopy, calcite and hematite were the major compounds found while aragonite, limonite, rutile, quartz and some aluminosilicates such as obsidian or amazonite (KAlSi3O8) were also present in minor percentages. As deterioration products, gypsum and anhydrite were widely found not only in the surface but also in the inner part of strongly deteriorated samples. Coquimbite (Fe2(SO4)3·9H2O) was identified as well in the most protected facade where high amounts of Fe, having probably an anthropogenic origin, were measured by micro X-ray fluorescence (μ-XRF). Zn was found to be in high amounts while Cu, Pb, Ti, Mn, Sr and K were identified as minor elements. Considering the non-expected concentrations found for some anthropogenic elements, a sequential extraction was carried out in order to determine their chemical form by means of ion chromatography and inductively coupled plasma mass spectrometry. The orientation of the facades, which had a different influence from rain washing and industrial and traffic impact, was shown to affect the accumulation of different compounds in the black crust. Finally, the MEDUSA software was used to simulate the reactions among the original compounds, deposited pollutants and the atmospheric acid gases in order to explain the presence of the decaying species found. FigureMultianalytical Speciation protocol applied on the analysis of modern mortars

Thermodynamic and spectroscopic speciation to explain the blackening process of hematite formed by atmospheric SO2 impact: the case of Marcus Lucretius House (Pompeii).

After many decades exposed to a polluted environment, in some areas of Marcus Lucretius House, there are clear signs that plasters and hematite pigments are suffering deterioration. In the exhaustive analysis of the black layer covering the red pigment hematite it was possible to identify magnetite (Fe(3)O(4)) as responsible for the black colour, which always appears in combination with gypsum. Thermodynamic modelling stated that the presence of gypsum as well as the transformation of hematite into magnetite is a consequence of the attack of atmospheric SO(2).

Nature and origin of white efflorescence on bricks, artificial stones, and joint mortars of modern houses evaluated by portable Raman spectroscopy and laboratory analyses.

Bricks and mortar currently constitute one of the most important building materials used in the construction of most modern facades. The deterioration of these materials is caused primarily by the impact of numerous external stressors, while poor manufacturing quality, particularly of mortars, can also contribute to this process. In this work, the non-invasive Raman spectroscopy technique was used to identify the recently formed deterioration compounds (primarily sulfates and nitrates) in bricks, artificial stones, and joint mortars from detached houses in the Bilbao metropolitan area (Basque Country, North of Spain), as well as to investigate the deterioration processes taking place in these materials. Additionally, to confirm and in some cases complement the results obtained with Raman spectroscopy, SEM-EDS and XRD measurements were also carried out.

In situ characterization by Raman and X-ray fluorescence spectroscopy of post-Paleolithic blackish pictographs exposed to the open air in Los Chaparros shelter (Albalate del Arzobispo, Teruel, Spain)

An in situ study of post-Palaeolithic blackish pictographs found in an open air rock-shelter, Los Chaparros site (Albalate del Arzobispo, Teruel province, Spain), was carried out to identify the black pigments used. The composition of the pigments was analyzed by means of non-invasive instrumentation, such as a portable Raman spectrometer (RS) and a hand-held energy dispersive X-ray fluorescence (EDXRF) analyzer. In addition, some black natural deposits with a dendritic pattern, typical of manganese compounds, were also in situ analysed with the aforementioned techniques to explore the possibility that post-Paleolithic people used minerals from the surroundings of the Los Chaparros rock-shelter to elaborate the paintings. The results obtained by the EDXRF analyses of black pigments showed differences in composition between a black Levantine deer, in which manganese was present as the main element, and a deep red Schematic pictograph that included manganese as the secondary element. The results of Principal Component Analysis (PCA) of collected EDXRF spectra showed similarities in the elemental composition between the manganese dendrite formations present in the rock-shelter and the black deer. In order to confirm this, the in situ analytical campaign was completed with some analysis in the laboratory by using micro-RS (μ-RS) and X-ray diffraction (XRD) on mineral samples having black crystallisations. Two specimens were taken, one from the black dendrite present in the same rock-shelter and the other from the Los Mases de Crivillen mining area (which is near to Los Chaparros). These analyses revealed that the characteristic bands of Mn–O and Mn–OH bending and stretching vibrations obtained in situ on the black pictograph were the same as those observed in the Raman spectra of the dendrite mineralization of Los Chaparros obtained in the laboratory by μ-RS.

Raman spectroscopy after accelerated ageing tests to assess the origin of some decayed products found in real historical bricks affected by urban polluted atmospheres.

AbstractBricks, together with stones and mortars, can be considered as one of the most important building materials that constitute our built heritage. Numerous factors which cause several decaying pathologies in bricks can be listed, but it should be emphasised that the most severe and damaging one is the wet and dry deposition of both combustion and greenhouse gases (CO2, SOx and NOx mainly). For instance, after the impact of CO2 and SOx, the decayed products promoted in bricks are carbonates and sulphates. Once identified in all these kinds of salts in real samples, it is necessary to make sure that the aggressive atmospheric conditions are sufficient to promote the formation of these salts. Therefore, accelerated exposure test are a good alternative in order to simulate the formation of these decayed compounds and to predict the reactions that promote the decaying mechanism. In this work, brick samples manufactured at different firing temperatures following ancient methods were subjected to humidity/dryness, freeze/thaw, CO2 and SO2 (KESTERNICH DIN 50018) accelerated ageing tests followed by a Raman spectroscopy screening in order to verify the formation of sulphate and carbonate salts in bricks on accelerated conditions, simulating the damage caused by a polluted atmosphere throughout many years of exposure. FigureRaman spectra of a white grain after the SO2 ageing experiments. Traces of calcite are observed together with the gypsum signals.

Multianalytical approach to the analysis of English polychromed alabaster sculptures: μRaman, μEDXRF, and FTIR spectroscopies

A complete study of several English polychromed alabaster sculptures is presented. The support, pigment, and binders were characterised by combining μEDXRF, μRaman, and FTIR spectroscopies. Among the pigments, minium, vermilion, lead white, carbon black, red iron oxide, and a degraded green copper pigment were determined, together with gold leaf. The presence of the rare mineral moolooite (copper oxalate) was also found as a degradation product in the green areas, where weddellite (calcium oxalate dihydrate) was also determined. These facts, together with degradation of the green copper pigment, suggest microbiological degradation of the original materials. Remains of glue and a varnish were also determined by FTIR spectroscopy and principal-components analysis (PCA) of the spectra. Finally, PCA analysis was carried out to confirm whether the pieces came from the same quarry.

Use of portable devices and confocal Raman spectrometers at different wavelength to obtain the spectral information of the main organic components in tomato (Solanum lycopersicum) fruits

Tomato (Solanum lycopersicum) fruit samples, in two ripening stages, ripe (red) and unripe (green), collected from a cultivar in the North of Spain (Barrika, Basque Country), were analyzed directly, without any sample pretreatment, with two different Raman instruments (portable spectrometer coupled to a micro-videocamera and a confocal Raman microscope), using two different laser excitation wavelengths (514 and 785 nm, only for the confocal microscope). The combined use of these laser excitation wavelengths allows obtaining, in a short period of time, the maximum spectral information about the main organic compounds present in this fruit. The major identified components of unripe tomatoes were cutin and cuticular waxes. On the other hand, the main components on ripe tomatoes were carotenes, polyphenoles and polysaccharides. Among the carotenes, it was possible to distinguish the presence of lycopene from β-carotene with the help of both excitation wavelengths, but specially using the 514 nm one, which revealed specific overtones and combination tones of this type of carotene.

Study of particulate matter from Primary/Secondary Marine Aerosol and anthropogenic sources collected by a self-made passive sampler for the evaluation of the dry deposition impact on built heritage

Dry deposition is one of the most dangerous processes that can take place in the environment where the compounds that are suspended in the atmosphere can react directly on different surrounding materials, promoting decay processes. Usually this process is related with industrial/urban fog and/or marine aerosol in the coastal areas. Particularly, marine aerosol transports different types of salts which can be deposited on building materials and by dry deposition promotes different decay pathways. A new analytical methodology based on the combined use of Raman Spectroscopy and SEM-EDS (point-by-point and imaging) was applied. For that purpose, firstly evaporated seawater (presence of Primary Marine Aerosol (PMA)) was analyzed. After that, using a self-made passive sampler (SMPS), different suspended particles coming from marine aerosol (transformed particles in the atmosphere (Secondary Marine Aerosol (SMA)) and metallic airborne particulate matter coming from anthropogenic sources, were analyzed. Finally in order to observe if SMA and metallic particles identified in the SMPS can be deposited on a building, sandstone samples from La Galea Fortress (Getxo, north of Spain) located in front of the sea and in the place where the passive sampler was mounted were analyzed.

Portable Raman monitoring of modern cleaning and consolidation operations of artworks on mineral supports

Any restoration performed on cultural heritage artworks must guarantee a low impact on the treated surfaces. Although completely risk-free methods do not exist, the use of tailor-made procedures and the continuous monitoring by portable instrumentation is surely one of the best approaches to conduct a modern restoration process. In this work, a portable Raman monitoring, combined sometimes with spectroscopic techniques providing the elemental composition, is the key analysis technique in the three-step restoration protocol proposed: (a) in situ analysis of the surface to be treated (original composition and degradation products/pollutants) and the cleaning agents used as extractants, (b) the thermodynamic study of the species involved in the treatment in order to design a suitable restoration method and (c) application and monitoring of the treatment. Two cleaning operations based on new technologies were studied and applied to two artworks on mineral supports: a wall painting affected by nitrate impact, and a black crusted stone (chalk) altarpiece. Raman bands of nitrate and gypsum, respectively, decreased after the step-by-step operations in each case, which helped restorers to decide when the treatment was concluded, thus avoiding any further damage to the treated surface of the artworks.