When Red Turns Black: Influence of the 79 AD Volcanic Eruption and Burial Environment on the Blackening/Darkening of Pompeian Cinnabar.

It is widely known that the vivid hue of red cinnabar can darken or turn black. Many authors have studied this transformation, but only a few in the context of the archeological site of Pompeii. In this work, the co-occurrence of different degradation patterns associated with Pompeian cinnabar-containing fresco paintings (alone or in combination with red/yellow ocher pigments) exposed to different types of environments (pre- and post-79 AD atmosphere) is reported. Results obtained from the in situ and laboratory multianalytical methodology revealed the existence of diverse transformation products in the Pompeian cinnabar, consistent with the impact of the environment. The effect of hydrogen sulfide and sulfur dioxide emitted during the 79 AD eruption on the cinnabar transformation was also evaluated by comparing the experimental evidence found on paintings exposed and not exposed to the post-79 AD atmosphere. Our results highlight that not all the darkened areas on the Pompeian cinnabar paintings are related to the transformation of the pigment itself, as clear evidence of darkening associated with the presence of manganese and iron oxide formation (rock varnish) on fragments buried before the 79 AD eruption has also been found.

Chemometrics and elemental mapping by portable LIBS to identify the impact of volcanogenic and non-volcanogenic degradation sources on the mural paintings of Pompeii.

Crystallization of soluble salts is a common degradation phenomenon that threatens the mural paintings of Pompeii. There are many elements that contribute to the crystallization of salts on the walls of this archaeological site. Notably, the leachates of the pyroclastic materials ejected in 79 AD by Mount Vesuvius and local groundwater, rich in ions from the erosion of volcanic rocks. Both sources could contribute to increase the concentration of halides (fluorides and chlorides) and other salts in these walls. The distribution of volcanogenic salts and their impact on the conservation of Pompeian mural paintings have however not yet been fully disclosed. In this work, an analytical methodology useful to determine the impact of the main sources of degradation affecting the mural paintings of Pompeii is presented. This methodology combines the creation of qualitative distribution maps of the halogens (CaF and CaCl) and related alkali metals (Na and K) by portable Laser Induced Breakdown Spectroscopy (LIBS) and a subsequent Principal Component Analysis of these data. Such maps, together with the in-situ identification of sulfate salts by portable Raman spectroscopy, provided information about the migration and distribution of volcanogenic halides and the influence of ions coming from additional sources (marine aerosol and modern consolidation mortars). Additionally, the thermodynamic modeling developed using the experimentally determined ionic content of Pompeian rain- and groundwater allowed to determine their specific role in the formation of soluble salts in the mural paintings of Pompeii.

Analytical methodology to evaluate the Terrestrial Weathering of Libyan Desert Glasses and Darwin Glasses after their formation.

Libyan Desert Glasses (LDGs) and Darwin Glasses (DGs) are impact glasses produced by the impact of an extraterrestrial body into the Earth million years ago. LDGs were formed in the Libyan Desert (Africa) and DGs in Tasmania (Australia). From their formation, they have suffered terrestrial weathering processes due to their interaction with the environment. This is the first work that has evaluated their weathering processes according to their composition, the surrounding environment, and the climate. An innovative methodology based on the leaching of organic and inorganic ions and chemical modeling simulations was employed. Inductively coupled plasma-mass spectrometry (ICP-MS), ionic chromatography (IC), and solid-phase microextraction (SPME), and head space (HS) injections coupled to gas chromatography and mass spectrometry (GC-MS) detection were used. As a result, soluble organic compounds such as oxalates, n-hexadecanoic acid, and 4-chlorobenzalacetone were detected. The inorganic ions suffered a similar process, going inside the body of glasses and precipitating the corresponding salts when water evaporated. As these compounds are polar, they were probably transported by infiltration waters from outside the glasses, remaining inside in the pores, cavities, or cracks of the glasses during thousands of years. In the case of the DGs, it could be observed that under the oxidizing conditions of the terrestrial atmosphere, sulfides present in some samples transformed into sulfates. Finally, this methodology could be applied in other extraterrestrial materials discovered in deserts, ice fields, or in locations with great living activity like those of Tasmania.

Long term monitoring of metal pollution in sediments as a tool to investigate the effects of engineering works in estuaries. A case study, the Nerbioi-Ibaizabal estuary (Bilbao, Basque Country).

The Nerbioi-Ibaizabal estuary (Bilbao, Basque Country) suffered an important input of contaminants, including metals and metalloids, between 1875 and 1975. We collected sediments in the tidal part of the river in January 2018 and measured the concentrations of 27 elements in them. At that time, two important construction works were taking place in the area: the extension of the commercial port and the opening of long semi-closed channel. Comparing the current metallic hotspots with the geographical distribution of elements in previous years (2009, 2010 and 2014) showed us that these works seem to have significantly influenced the distribution of toxic elements in the estuary, even if the critical point of the second one is still to arrive with the inundation of the connection to the mainland. Long term pollution monitoring reveals as a powerful tool to check the effects of ongoing engineering works in estuarine environments.

Evidence of mercury sequestration by carbon nanotubes and nanominerals present in agricultural soils from a coal fired power plant exhaust.

Mercury (Hg) in agricultural soils could have negative effects on the environment and the human health. The exposure to high level of Hg through different absorption pathways, such as ingestion and diet through soil-plant system could permanently damage developing foetus of animals and humans. With the aim to assess the potential environmental and health risk and to study the behaviour and fate of Hg from agricultural soils to the environment, 47 soil samples were collected around a thermoelectric power plant in the Santa Catarina (Brazil). The Hg concentration measured by inductively coupled plasma mass spectrometry (ICP-MS) ranged from 0.16 to 0.56 mg kg-1. The distribution obtained by kriging interpolation allowed the identification of the main pollution sources. To see the morphology and composition of soil samples, field emission scanning electron microscopy (FE-SEM) and high resolution transmission electron microscopy (HR-TEM) were used combined with energy dispersive X-ray spectroscopy (EDS), showing that the carbon nanotubes and magnetite as nanomineral contributed to Hg retention. The mentioned molecular characterization, and the low Contamination Factors (CF) values obtained, suggested that there is low risk to the food security of the agro-ecosystems area near to the CFPP in the terms of Hg inputs and contamination.

Evaluating the role of particle size on urban environmental geochemistry of metals in surface sediments.

In this study, non-destructive techniques (X-ray Diffraction, Infrared and Scanning Electron Microscopy with Energy Dispersive spectroscopies) and invasive procedures (pseudo-total and sequential metal extraction methodologies) were used to highlight the significance of evaluating different particle sizes of sediments for assessing the potential environmental and health implications of metal geochemistry in an urban ecosystem. The variability in composition and properties between bulk (<2 mm) and fine (<63 µm) fractions influenced the availability, and by extension, the toxicity of metals. Indeed, the fine fraction presented not only higher metal pseudo-contents, but also greater available metal percentages. Besides the larger surface area per unit of mass and the high content of clay minerals, it was observed that it was principally Fe/Mn oxyhydroxides that favour adsorption of metals on the fine surface sediments. However, although we demonstrated that the origin of metals in the bulk surface sediments was predominantly lithogenic, use of the <2 mm fraction proved to be a useful tool for identifying different sources of available metals throughout the Deba River catchment. Specifically, discharges of untreated industrial and urban wastewaters, and even effluents from wastewater treatment plants were considered to greatly increase the health risk associated with metal availability. Finally, an evaluation of sediment dynamics in different hydrological conditions has highlighted the role played by each particle size as a vector of metal transport towards the coastal area. While resuspension of fine surface sediments notably induced significantly higher particulate metal concentrations in water during the dry season, resuspension of bulk surface sediments and, fundamentally, downstream transport of suspended particulate matter became more relevant and lowered the ecological risk during the wet season. Greater attention therefore needs to be paid to the new hydrological scenarios forecast to result from climate change, in which longer seasons with low river discharges are forecast.

Non-destructive characterisation of the Elephant Moraine 83227 meteorite using confocal Raman, micro-energy-dispersive X-ray fluorescence and Raman-scanning electron microscope-energy-dispersive X-ray microscopies.

The application of a non-destructive analytical procedure to characterise the mineral phases in meteorites is a key issue in order to preserve this type of scarce materials. In the present work, the Elephant Moraine 83227 meteorite, found in Antarctica in 1983 and originated from 4 Vesta asteroid, was analysed by micro-Raman spectroscopy, micro-energy-dispersive X-ray fluorescence and the structural and chemical analyser (Raman spectroscopy coupled with scanning electron microscopy-energy-dispersive spectroscopy) working in both point-by-point and image modes. The combination of all these techniques allows the extraction of, at the same time, elemental, molecular and structural data of the studied microscopic area of the meteorite. The most relevant results of the Elephant Moraine 83227 were the finding of tridymite for the first time in a 4 Vesta meteorite, along with quartz, which means that the meteorite suffered high temperatures at a certain point. Moreover, both feldspar and pyroxene were found as the main mineral phases in the sample. Ilmenite, apatite, chromite and elemental sulphur were also detected as secondary minerals. Finally, calcite was found as a weathering product, which was probably formed in terrestrial weathering processes of the pyroxene present in the sample. Besides, Raman spectroscopy provided information about the conditions that the meteorite experienced; the displacements in some feldspar Raman bands were used to estimate the temperature and pressure conditions to which the Elephant Moraine 83227 was subjected, because we obtained both low and high formation temperature feldspar.

Detection of organic compounds in impact glasses formed by the collision of an extraterrestrial material with the Libyan Desert (Africa) and Tasmania (Australia).

Impact glasses are rich silica melted formed at high temperature and pressure by the impact of an extraterrestrial body on Earth. Here, Libyan Desert glasses (LDGs) and Darwin glasses (DGs) were studied. Two non-destructive analytical techniques were used to detect and characterize organic compounds present in their inclusions: Raman spectroscopy and scanning electron microscopy coupled to energy-dispersive X-ray spectroscopy (SEM-EDS). Phytoliths, humboldtine, palmitic acid, myristic acid, oleic acid, 4-methyl phthalic acid, and S-H stretching vibrations of amino acids were identified. The presence of these particular organic compounds in such materials has not been reported so far, providing information about (a) the ancient matter of the area where the impact glasses were formed, (b) organic matter belonging to the extraterrestrial body which impacted on the Earth, or (c) even to current plant or bacterial life, which could indicate an active interaction of the LDG and DG with the surrounding environment. Moreover, the identification of fullerene allowed us to know a pressure (15 GPa) and temperatures (670 K or 1800-1900 K) at which samples could be subjected.

Metal contaminations impact archaeal community composition, abundance and function in remote alpine lakes.

Using the 16S rRNA and mcrA genes, we investigated the composition, abundance and activity of sediment archaeal communities within 18 high-mountain lakes under contrasted metal levels from different origins (bedrock erosion, past-mining activities and atmospheric depositions). Bathyarchaeota, Euryarchaeota and Woesearchaeota were the major phyla found at the meta-community scale, representing 48%, 18.3% and 15.2% of the archaeal community respectively. Metals were equally important as physicochemical variables in explaining the assemblage of archaeal communities and their abundance. Methanogenesis appeared as a process of central importance in the carbon cycle within sediments of alpine lakes as indicated by the absolute abundance of methanogen 16S rRNA and mcrA gene transcripts (105 to 109 copies g-1 ). We showed that methanogen abundance and activity were significantly reduced with increasing concentrations of Pb and Cd, two indicators of airborne metal contaminations. Considering the ecological importance of methanogenesis in sediment habitats, these metal contaminations may have system wide implications even in remote area such as alpine lakes. Overall, this work was pioneer in integrating the effect of long-range atmospheric depositions on archaeal communities and indicated that metal contamination might significantly compromise the contribution of Archaea to the carbon cycling of the mountain lake sediments.

Study of the soluble salts formation in a recently restored house of Pompeii by in-situ Raman spectroscopy.

The walls and mural paintings of Pompeii exposed directly to the rainfalls are the most impacted in view of the observed decay. However, there are also wall paintings in protected rooms showing evidences of decaying. The aim of this research was to study the salts formed in such protected wall paintings only by non-invasive and in-situ Raman spectroscopy to understand their decaying processes. The perystile of the House of the Gilded Cupids (Regio VI, Insula 16), one of the most important houses of Pompeii was studied. Although an exhaustive restoration was carried out in 2004, a new conservation treatment was needed in 2013 and only two years later, extensive crystallizations of soluble salts were again threatening several of the restored surfaces, thus, the presence of an unsolved degradation pathway was deduced. Thank to the proposed methodology, it was pointed out that the key is the acidified rainfall impact in the non-protected backside of the walls containing the wall paintings. Thus, a new concept in the preservation of the houses of Pompeii is provided, in which the need of the protection of those walls from both sides is suggested to avoid the movement of water through the pores of the walls.

Combination of in situ spectroscopy and chemometric techniques to discriminate different types of Roman bricks and the influence of microclimate environment.

Red and yellow bricks are the wall-building materials generally used in Roman masonries. The reasons for the different coloration are not always understood, causing loss of crucial information both for the conservation and for the archaeological knowledge of the cultural sites. In this work, a combination of in situ analyses, employing portable Raman spectroscopy and handheld energy dispersive X-ray fluorescence (HH-ED-XRF) spectroscopy along with chemometric analysis, was carried out on ancient Roman bricks of the "Casa di Diana" building (Ostia Antica, Italy-130 CE). Specifically, the compounds and the characteristic elements, which describe each type of brick (red and yellow), were studied avoiding destructive or invasive sampling. The molecular analysis allowed us to identify the major and minor compounds that characterise the bricks (anatase, hematite, quartz, calcite and silicates). However, the elemental analysis gave more useful information. Thus, the complex HH-ED-XRF data matrix generated was treated by a specific principal component analysis (PCA) to identify behavioural differences of the coloured bricks. The results revealed that Ca and Fe are the discriminatory elements for the two types of bricks. The PCA outcomes suggest that the contribution of certain elements is different in the bricks (mainly Ca, P, Sr, As and S, for yellow bricks), which could indicate different raw materials. Even among bricks with the same red colour (Al, Si, Ti, K, Fe, Cr, Mn, Ni, Zn, Cu, Rb and Zr, seemed to be the elements linked to raw materials), as a function of the surface impacts (orientation and microclimate affect the salts' formation), a distinction was made. Furthermore, the PCA pointed out that the yellow bricks are those more affected by decaying processes (related with Ca, P and S), complying with the Raman spectroscopy results in which the efflorescences (gypsum) affect especially the surface of these types of bricks.

Metallurgical residues reused as filler after 35years and their natural weathering implications in a mountain area.

The natural weathering of EAF (Electric Arc Furnace) and LF (Ladle Furnace) steel slag was evaluated through changes in the mineralogical and elemental composition. For that purpose, black steel slag and mixture of black and white steel slag were collected from two forest tracks, where they had been used as filler 19 and 35years ago respectively in a protected mountain area. Primary/original and secondary/degradation compounds were identified by spectroscopic techniques (Raman Spectroscopy, X-Ray Diffraction (XRD) and Scanning Electron Microscopy/Energy Dispersive X-Ray Spectroscopy (SEM/EDS)). Among secondary compounds, brucite (Mg(OH)2), portlandite (Ca(OH)2), thaumasite (Ca3Si(CO3)(SO4)(OH)6.12H2O) were identified. Secondary compounds indicated the reactivity of the slag with the surrounding environment (underground waters, atmosphere, lands and organisms), and volume change of the material. This effect could promote fractures in the road and thus, increase the possibility of leaching of hazardous elements (HE), present in the slags, to lands, rivers, etc. Besides, potentially toxic compounds such as hashemite (BaCrO4) and crocoite (PbCrO4) were identified as Cr(VI), which means a potential hazard to the surrounding environment and human life, since the sampling location is a mountain area with recreational activities. Cr(VI) can affect to the growth and development of plants, soil microbial communities, animals and cause allergy, asthma and respiratory tract cancer in humans. Moreover, Inductively Coupled Plasma Mass Spectrometry (ICP-MS) allowed us to observe similar ranges of elemental concentrations in slag samples of the two forest tracks, with the exception of Ca, Mg, Sr, Pb, Ni and As concentration values. They were higher in the forest track with mixture of black and white slag than in the track with only black slag, and therefore, more likely to be leached and to be an environmental risk over time. By contrast, Na, V, Cr and W values were higher in the track with only black steel slag.

Are children playgrounds safe play areas? Inorganic analysis and lead isotope ratios for contamination assessment in recreational (Brazilian) parks.

In city playgrounds, there is a potential risk of harming children's health by contamination coming from anthropogenic activities. With the aim to determinate the sources and the risk of hazardous elements, soil samples were collected in 19 selected playgrounds of different urban and rural areas from the Rio Grande do Sul state (Brazil). The concentration of 23 metals and metalloids and lead isotopic ratios were determined by ICP-MS. The methodology proposed here, firstly, classified the parks according to the average metal content by means of the NWACs (Normalized-and-Weighted Average Concentrations) and assess the contamination risk determining the Contamination Factors (CFs). Finally, statistical tools (correlation analysis and principal component analysis) were used to identify the most important contamination sources. The statistical tools used, together with lead isotopic composition analysis of the samples, revealed that coal combustion is the main source of contamination in the area. Vegetation was identified as a barrier for the contamination coming from the city. Nonetheless, some of the soils present a possible toxicological risk for humans. In fact, Cr, Sb, and Pb concentrations were higher than the Residential Intervention Values (VIRs) defined by the Environmental Protection Agency of the State of São Paulo, also in Brazil.

Contamination study of forest track soils located in a recreational area and filled with steel industry waste 30years ago.

The reuse of waste is increasingly widespread in order to avoid the exploitation of natural resources and to reduce costs. An example of that reuse is the employment of steel slag, a by-product from the steel making process. When the steel is produced through an electric arc furnace (EAF), two types of slag are generated: black and white slag. One application rarely used for this waste is as filler in forest tracks. In this work, two forest tracks of the Basque Country (northern Spain) filled with black and white slag 19 and 35years ago, respectively, have been studied. Leaching tests were performed using Milli-Q water and acetic acid over the slags collected in that area. Additionally, soil samples collected near the slags were subjected to acid digestion. In these soil samples, there were elements of natural origin and others that could come from the leaching of the slag. Some of the more leached elements from the black slag (Ca, Fe, K, Cr, Se, W, Mn and Mo) and white slag (Mg, Al, Na, Co, Ni and Cu) coincided with the elements of highest concentration found in the soil samples. Moreover, there were differences in some elemental concentrations of soil samples with only black slag (higher presence of Ca and Mg) and soil samples with a mixture of both types of slag. It was noticeable that the highest concentration values of the measured elements were found on a specific side of the forest tracks, possibly due to the runoff water or the higher inclination of that side. On the other hand, some areas of both forest tracks could be considered contaminated by Cr according to a standard values from the Basque regulation, posing a risk to human health since they are recreational areas.

Comparison between non-invasive methods used on paintings by Goya and his contemporaries: hyperspectral imaging vs. point-by-point spectroscopic analysis.

The development of non-invasive techniques for the characterization of pigments is crucial in order to preserve the integrity of the artwork. In this sense, the usefulness of hyperspectral imaging was demonstrated. It allows pigment characterization of the whole painting. However, it also sometimes requires the complementation of other point-by-point techniques. In the present article, the advantages of hyperspectral imaging over point-by-point spectroscopic analysis were evaluated. For that purpose, three paintings were analysed by hyperspectral imaging, handheld X-ray fluorescence and handheld Raman spectroscopy in order to determine the best non-invasive technique for pigment identifications. Thanks to this work, the main pigments used in Aragonese artworks, and especially in Goya's paintings, were identified and mapped by imaging reflection spectroscopy. All the analysed pigments corresponded to those used at the time of Goya. Regarding the techniques used, the information obtained by the hyperspectral imaging and point-by-point analysis has been, in general, different and complementary. Given this fact, selecting only one technique is not recommended, and the present work demonstrates the usefulness of the combination of all the techniques used as the best non-invasive methodology for the pigments' characterization. Moreover, the proposed methodology is a relatively quick procedure that allows a larger number of Goya's paintings in the museum to be surveyed, increasing the possibility of obtaining significant results and providing a chance for extensive comparisons, which are relevant from the point of view of art history issues.

In situ X-ray fluorescence-based method to differentiate among red ochre pigments and yellow ochre pigments thermally transformed to red pigments of wall paintings from Pompeii.

Most of the magnificent wall paintings from the ancient city of Pompeii are decorated with red and yellow colors coming from the ochre pigments used. The thermal impact of the pyroclastic flow from the eruption of Vesuvius, in AD 79, promoted the transformation of some yellow painted areas to red. In this work, original red ochre, original yellow ochre, and transformed yellow ochre (nowadays showing a red color) of wall paintings from Pompeian houses (House of Marcus Lucretius and House of Gilded Cupids) were analyzed by means of a handheld energy-dispersive X-ray fluorescence spectrometer to develop a fast method that allows chemical differentiation of the original red ochre and the transformed yellow ochre. Principal component analysis of the multivariate obtained data showed that arsenic is the tracer element to distinguish between both red colored ochres. Moreover, Pompeian raw red and yellow ochre pigments recovered from the burial were analyzed in the laboratory with use of a benchtop energy-dispersive X-ray fluorescence spectrometer to confirm the elemental composition and the conclusions drawn from the in situ analysis according to the yellow ochre pigment transformation in real Pompeian wall paintings.

Multispectroscopic methodology to study Libyan desert glass and its formation conditions.

Libyan desert glass (LDG) is a melt product whose origin is still a matter of controversy. With the purpose of adding new information about this enigma, the present paper analyzes the inner part of LDG specimens and compares them with the results of LDG surfaces. An integrated analytical methodology was used combining different techniques such as Raman spectroscopy, in point-by-point and imaging modes, scanning electron microscopy with X-ray microanalysis (SEM-EDS), energy-dispersive micro X-ray fluorescence spectrometry (µ-EDXRF), electron probe micro analyzer (EPMA), and optical cathodoluminescence (Optical-CL). According to our results, flow structures of the melt and the amorphous nature of the matrix could be discerned. Moreover, the observed displacement of Raman bands, such as in the cases of quartz and zircon, and the identification of certain compounds such as coesite (the most clarifying phase of high pressures), α-cristobalite, gypsum, anhydrite, corundum, rutile, amorphous calcite, aragonite, and calcite allowed us to know that LDGs could be subjected to shock pressures between 6 and more than 30 GPa, and temperatures between 300 and 1470 °C. The differences of temperature and pressure would be provoked by different cooling processes during the impact. Besides, in most cases the minerals corresponding to high pressure and temperatures were located in the inner part of the LDGs, with some exceptions that could be explained because they were trapped subsequently to the impact; there was more than one impact or heterogeneous cooling.Furthermore, nitrogen and oxygen gases were identified inside bubbles, which could have been introduced from the terrestrial atmosphere during the meteorite impact.These data helped us to clarify some clues about the origin of these enigmatic samples.

Nanominerals and potentially hazardous elements from coal cleaning rejects of abandoned mines: Environmental impact and risk assessment.

Soils around coal mining are important reservoir of hazardous elements (HEs), nanominerals, and ultrafine compounds. This research reports and discusses the soil concentrations of HEs (As, Cd, Cr, Cu, Ni, Pb, and Zn) in coal residues of abandoned mines. To assess differences regarding environmental impact and risk assessment between coal abandoned mines from the Santa Catarina state, eighteen coal cleaning rejects with different mineralogical and chemical composition, from eight abandoned mines were collected. Nanominerals and ultra-fine minerals from mining-contaminated areas were analyzed by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and high-resolution transmission electron microscope (HR-TEM), providing new information on the mineralogy and nano-mineralogy of these coal residues. The total contents of 57 elements (HEs, alkali metals, and rare earth elements) were analyzed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The calculation of NWACs (Normalized Average Weighted Concentration), together with the chemometric analysis by Principal component analysis (PCA) confirmed the variability of the samples regarding their city and their mine of origin. Moreover, the results confirmed the existence of hotspots in mines near urban areas.

Multispectroscopic and Isotopic Ratio Analysis To Characterize the Inorganic Binder Used on Pompeian Pink and Purple Lake Pigments.

Because of the fact that pigments are not ubiquitous in the archeological record, the application of noninvasive analytical methods is a necessity. In this work, pink and purple lake pigments recovered from the excavations of the ancient city of Pompeii (Campania, Italy) and preserved in their original bowls at the Naples National Archaeological Museum (Italy) were analyzed to characterize the composition of their inorganic binders (mordants). In situ preliminary analyses using a hand-held energy dispersive X-ray fluorescence spectrometer (HH-ED-XRF) allowed us to determine the use of an aluminosilicate enriched in Cu and Pb. Scanning electron microscopy coupled to energy dispersive X-ray spectrometry (SEM-EDS) and benchtop ED-XRF analyses confirmed these results, while inductively coupled plasma mass spectrometry (ICPMS) allowed one to determine the concentration of major, minor, and trace elements. The use of other techniques such as X-ray diffraction (XRD), and micro-Raman and infrared spectroscopies allowed one to characterize the pigments at the molecular level. The high concentration of Cu detected in the pigments (1228-12937 µg g(-1)) could be related to the addition of Cu salts to obtain the desired final hue. The concentrations of Pb (987-2083 µg g(-1)) was also remarkable. Lead isotopic ratio analysis ((206)Pb/(207)Pb) suggested a possible origin related to the leaching of the ancient lead pipes from Pompeii and the subsequent transfer to the buried pigments or to the inorganic binder. Molecular analysis also showed that the binder is composed of an allophane-like clay. Moreover, it was possible to determine that to obtain the final purple hue of a specific pigment, Pompeian blue pigment was also mixed into the dyed clay.

Spatial distribution of some trace and major elements in sediments of the Cávado estuary (Esposende, Portugal).

For the first time, the occurrence and spatial distribution of several elements, including some toxic metals, have been investigated in sediments of the estuary of the Cávado River (Esposende, Portugal). The pseudo total concentrations of Al, As, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Sn, V and Zn in sediments collected at 24 sites covering the tidal part of the estuary were determined. According to the concentrations measured, the Cávado estuary can be considered as non-contaminated. For most of the elements, the concentrations tended to be higher upstream. Only a moderate enrichment in Cr and Ni was detected in a few sites. An important decrease in concentration was observed for the most toxic metals compared to historical data reported in the literature. Several hotspots were identified, but even in those cases the amount of metals stored in the sediments does not represent a toxicological threat to living organisms.