Kepa Castro

Study of environmental pollution and mineralogical characterization of sediment rivers from Brazilian coal mining acid drainage

Acid drainage from coal mines and metal mining is a major source of underground and surface water contamination in the world. The coal mining acid drainage (CMAD) from mine contains large amount of solids in suspension and a high content of sulphate and dissolved metals (Al, Mn, Zn, Cu, Pb, Fe, etc.) that finally are deposited in the rivers. Since this problem can persist for centuries after mine abandonment, it is necessary to apply multidisciplinary methods to determine the potential risk in a determinate area. These multidisciplinary methods must include molecular and elemental analysis and finally all information must be studied statistically. This methodology was used in the case of coal mining acid drainage from the Tubarao River (Santa Catarina, Brazil). During molecular analysis, Raman Spectroscopy, electron bean, and X-ray diffraction (XRD) have been proven very useful for the study of minerals present in sediment rivers near this CMAD. The obtained spectra allow the precise identification of the minerals as jarosite, quartz, clays, etc. The elemental analysis (Al, As, Fe, K, Na, Ba, Mg, Mn, Ti, V, Zn, Ag, Co, Li, Mo, Ni, Se, Sn, W, B, Cr, Cu, Pb and Sr) was realised by inductively coupled plasma mass spectrometry (ICP-MS). Statistical analysis (Principal Component Analysis) of these dates of concentration reveals the existence of different groups of samples with specific pollution profiles in different areas of the Tubarao River.

Green copper pigments biodegradation in cultural heritage: from malachite to moolooite, thermodynamic modeling, X-ray fluorescence, and Raman evidence.

Moolooite (copper oxalate), a very rare compound, was found as a degradation product from the decay of malachite in several specimens of Cultural Heritage studied. Computer simulations, based on heterogeneous chemical equilibria, support the transformation of malachite to moolooite through the intermediate copper basic sulfates or copper basic chlorides, depending on the presence of available free sulfate or chloride anions in the chemical system. Raman and X-ray fluorescence spectral evidence found during the analysis of the three case studies investigated supported the model predictions. According to the study, the presence of lichens and other microorganisms might be responsible for the decay phenomena. This work tries to highlight the importance of biological attack on specimens belonging to Cultural Heritage and to demonstrate the consequences of oxalic acid, excreted by some of these microorganisms, on the conservation and preservation of artwork.

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.

Noninvasive and nondestructive NMR, Raman and XRF analysis of a Blaeu coloured map from the seventeenth century

A complete multianalytical study of a hand-coloured map from the seventeenth century is presented. The pigments atacamite, massicot, minium, gypsum, carbon black and vermilion were determined by means of XRF and Raman spectroscopy. The state of conservation of the cellulosic support was monitored by means of unilateral NMR. The analysis was nondestructive and noninvasive, and thus several spectra were collected from the same areas, yielding more reliable results without damaging the artwork. The role of copper pigments in the oxidation processes observed in the cellulosic support is discussed, as well as the possible provenance of atacamite as a raw material instead of as a degradation product of malachite.

Classification and identification of organic binding media in artworks by means of Fourier transform infrared spectroscopy and principal component analysis

AbstractFourier transform infrared spectroscopy is a powerful analytical technique to study organic materials. However, in Cultural Heritage, since the sample under analysis is always a complicated matrix of several materials, data analysis performed through peak-by-peak comparisons of sample spectra with those of standard compounds is a tedious method that does not always provide good results. To overcome this problem, a chemometric model based on principal component analysis was developed to classify and identify organic binding media in artworks. The model allows the differentiation of five families of binders: drying oils, waxes, proteins, gums, and resins, taking into account the absorption bands in two characteristic spectral windows: C–H stretching and carbonyl band. This new methodology was applied in the characterization of binders in three kinds of artworks: papers of historical, archeological, and artistic value, easel paintings, and polychromed stone-based sculptures. FigureAnalysis of the binder in a wallpaper of the 19th century by means of FTIR spectroscopy and chemometrics

Analysis of a coloured Dutch map from the eighteenth century: the need for a multi-analytical spectroscopic approach using portable instrumentation.

A Dutch map from the eighteenth century was multi-analytically analysed making use of energy dispersive X-ray fluorescence (EDXRF), Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), Raman and scanning electron microscopy coupled to energy dispersive spectrometry (SEM-EDS). The cellulosic support was characterised and its state of conservation was evaluated. Besides, paramagnetic impurities were detected together with copper metallic chips. The colours present in some areas of the map were also analysed. Vermilion, carbon black and organic pigments were found. Surprisingly, in the green areas, the rare presence of the mineral moolooite (copper oxalate) was detected. A possible biological attack is discussed in order to explain the presence of such compound. Almost all of the techniques used in the analysis were portable, non-destructive and non-invasive, which is very desirable when analysing objects belonging to Cultural Heritage. The need for a multi-analytical approach using portable instrumentation is also discussed.

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).

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.

Non-destructive spectrometry methods to study the distribution of archaeological and geological chert samples

The study of lithic raw materials recovered from archaeological sites offers relevant data on source catchment areas. Additionally, it can provide first hand information on artefact displacement, interchange networks and it can reflect the way in which the artefacts were employed. In order to characterize geological and archaeological chert samples and with the aim of finding an analytical fingerprint infrared and Raman spectroscopies were used for molecular analysis and X-ray Fluorescence spectrometry for elemental analysis. In this work, different chert samples coming from several localities with geological and archaeological importance from the Basque Country have been collected and analysed. As a consequence, Raman spectroscopy allowed to distinguish between alpha-quartz and moganite in chert samples without organic matter and it is suggested that the ratio of those two components is related to the source of the chert. In addition, the impurities that appear in the samples (CaCO(3), iron oxides and organic matter) can open new features to distinguish the samples and in this way, it would be possible to discuss the use and transport of the lithic artifacts from the sources to the final settlements.