Radiation-induced alteration of apatite on the surface of Mars: first in situ observations with SuperCam Raman onboard Perseverance

Planetary exploration relies considerably on mineral characterization to advance our understanding of the solar system, the planets and their evolution. Thus, we must understand past and present processes that can alter materials exposed on the surface, affecting space mission data. Here, we analyze the first dataset monitoring the evolution of a known mineral target in situ on the Martian surface, brought there as a SuperCam calibration target onboard the Perseverance rover. We used Raman spectroscopy to monitor the crystalline state of a synthetic apatite sample over the first 950 Martian days (sols) of the Mars2020 mission. We note significant variations in the Raman spectra acquired on this target, specifically a decrease in the relative contribution of the Raman signal to the total signal. These observations are consistent with the results of a UV-irradiation test performed in the laboratory under conditions mimicking ambient Martian conditions. We conclude that the observed evolution reflects an alteration of the material, specifically the creation of electronic defects, due to its exposure to the Martian environment and, in particular, UV irradiation. This ongoing process of alteration of the Martian surface needs to be taken into account for mineralogical space mission data analysis.

Geographical distribution of metals and metalloids along the estuary of the Oka River in the biosphere reserve of Urdaibai, Spain

Sediments sampled at the estuary of the Oka River in the biosphere reserve of Urdaibai, Spain were analyzed for trace elements. Sediments were collected at 45 points of the estuary and the concentration of 14 elements was measured. The geoaccumulation indexes (Igeo), Normalized Average Weighted Concentrations (NAWC) and mean Effect Range-Median quotients (mERMq) were calculated. The results obtained were complementary and allowed intra- and inter-estuary comparison. According to the present findings, the estuary was classified as healthy, since the anthropogenic contribution of metals and metalloids was generally small. However, shipping and fishing activities at the ports of Bermeo and Mundaka and urban and industrial wastes from Gernika were regarded as the major pollution sources. Nevertheless, only slightly contaminated and toxic sediments, especially related to Ni and Cu, were found in the towns of Gernika and Mundaka.

Multi-analytical characterization of an oncoid from a high altitude hypersaline lake using techniques employed in the Mars2020 and Rosalind Franklin missions on Mars

In this work, a geological sample of great astrobiological interest was studied through analytical techniques that are currently operating in situ on Mars and others that will operate in the near future. The sample analyzed consisted of an oncoid, which is a type of microbialite, collected in the Salar Carachi Pampa, Argentina. The main peculiarity of microbialites is that they are organo-sedimentary deposits formed by the in situ fixation and precipitation of calcium carbonate due to the growth and metabolic activities of microorganisms. For this reason, the Carachi Pampa oncoid was selected as a Martian analog for astrobiogeochemistry study. In this sense, the sample was characterized by means of the PIXL-like, SuperCam-like and SHERLOC-like instruments, which represent instruments on board the NASA Perseverance rover, and by means of RLS-like and MOMA-like instruments, which represent instruments on board the future ESA Rosalind Franklin rover. It was possible to verify that the most important conclusions and discoveries have been obtained from the combination of the results. Likewise, it was also shown that Perseverance rover-like remote-sensing instruments allowed a first detailed characterization of the biogeochemistry of the Martian surface. With this first characterization, areas of interest for in-depth analysis with Rosalind Franklin-like instruments could be identified. Therefore, from a first remote-sensing elemental identification (PIXL-like instrument), followed by a remote-sensing molecular characterization (SuperCam and SHERLOC-like instruments) and ending with an in-depth microscopic analysis (RLS and MOMA-like instruments), a wide variety of compounds were found. On the one hand, the expected minerals were carbonates, such as aragonite, calcite and high-magnesium calcite. On the other hand, unexpected compounds consisted of minerals related to the Martian/terrestrial surface (feldspars, pyroxenes, hematite) and organic compounds related to the past biological activity related to the oncoid (kerogen, lipid biomarkers and carotenes). Considering samples resembling microbialites have already been found on Mars and that one of the main objectives of the missions is to identify traces of past life, the study of microbialites is a potential way to find biosignatures protected from the inhospitable Martian environment. In addition, it should be noted that in this work, further conclusions have been obtained through the study of the results as a whole, which could also be carried out on Mars.

A new methodology for kerogen maturity estimation based on Raman spectroscopy and chemometric analysis

Diverse criteria or parameters have been cited as tools to determine the maturity of carbonaceous matter (CM) found in geologic samples using Raman spectroscopy. However, these approaches involve the mathematical decomposition of Raman bands which can vary with the specific method, the software employed, or even the individual user. Data should be treated spectrum by spectrum and a similar spectroscopic pre-treatment should be applied to the whole dataset. All these factors affect the final result and can introduce a wide uncertainty and bias. We propose an alternative chemometric method that avoids these sources of uncertainty by considering the entire spectrum, not just certain regions, while allowing specific regions of interest to be defined. Moreover, spectra pre-treatment is not required. We employ principal component analysis (PCA) across the whole range of spectra. While the method does not provide an absolute maturity value, it allows comparison of different CM in terms of maturity or H:C ratio. In the analysis of coal standards, samples were grouped by maturity.

Aqueously altered igneous rocks sampled on the floor of Jezero crater, Mars

The Perseverance rover landed in Jezero crater, Mars, to investigate ancient lake and river deposits. We report observations of the crater floor, below the crater's sedimentary delta, finding the floor consists of igneous rocks altered by water. The lowest exposed unit, informally named Séítah, is a coarsely crystalline olivine-rich rock, which accumulated at the base of a magma body. Fe-Mg carbonates along grain boundaries indicate reactions with CO₂-rich water, under water-poor conditions. Overlying Séítah is a unit informally named Máaz, which we interpret as lava flows or the chemical complement to Séítah in a layered igneous body. Voids in these rocks contain sulfates and perchlorates, likely introduced by later near-surface brine evaporation. Core samples of these rocks were stored aboard Perseverance for potential return to Earth.

Characterization of sedimentary and volcanic rocks in Armintza outcrop (Biscay, Spain) and its implication for Oxia Planum (Mars) exploration

The landing site of the next planetary mission lead by ESA (ExoMars 2022) will be Oxia Planum. This location has been chosen due to different reasons, among them, the existence of sedimentary rocks that could host remains of organic matter. The fact that this type of rocks coexists with volcanic ones makes of high importance the study of the processes and the possible interactions that could happen among them. Therefore, in this research work the Armintza outcrop (Biscay, North of Spain) is proposed as an Oxia Planum analogue since it has the dichotomy of volcanic and sedimentary rock layers that is expected on the landing site of the ExoMars 2022 mission. As Raman and visible near infrared spectroscopies will be in the payload of the rover of that mission, they have been used to characterize the samples collected in the Armintza outcrop. With the help of these techniques, feldspars (albite mainly) and phyllosilicates (kaolinite and dickite, together with micas and chlorite minerals) have been identified as the major products on the samples, together with some weathering products (carbonates, sulphates, oxides) and apatite. Moreover, remains of kerogen have been detected in the sedimentary layers in contact with the interlayered lava flows, confirming the capability of similar sedimentary-volcanic layers to trap and store organic remains for millions of years. After establishing which compounds have volcanic or sedimentary origin, and which must be considered alteration phases, we can consider Armintza as a good Oxia Planum analogue.

Development of innovative non-destructive analytical strategies for Mars Sample Return tested on Dar al Gani 735 Martian Meteorite

This work proposes an innovative non-destructive analytical strategy, based on Confocal Raman micro-spectroscopy, High Resolution Raman Imaging and micro-X-Ray Fluorescence imaging, as part of the quick non-destructive techniques that could be used to characterize the Martian samples from the Mars Sample Return mission when back on Earth. Until that moment, Martian Meteorites are the only Martian samples in our hands to develop such Analytical Strategies. To demonstrate its capabilities, this analytical strategy has been applied to characterize the Dar al Gani 735 Martian Meteorite with the aim to identify the terrestrial and non-terrestrial alterations suffered by the meteorite as a very valuable complementary methodology to the more traditional petrographic analyses and single point measurements. The combination of these techniques allows extracting at the same time elemental, molecular and structural information of the studied area of the sample. The most relevant results on the analyzed DaG 735 shergottite thick samples revealed the presence of several altered mineral phases originated from the temperature and pressure conditions during the shock on Mars (anhydride, calcite and ilmenite), as well as from terrestrial weathering processes that degraded the meteorite from its landing on Earth (calcite and hematite in fractures together with gypsum, mirabilite and thenardite). As most of the conclusive results come from Raman spectroscopy, this study shows the potential of Raman spectroscopy as a key technique in the upcoming new explorations of Mars materials by the Rosalind Franklin rover (Exomars2022 mission from ESA) and the Perseverance rover (Mars2020 mission from NASA), where Raman spectrometers are mounted for the first time in an extra-terrestrial research in the field.

A first evaluation of the usefulness of Kudzu starch in cultural heritage restoration

In recent times, the use of natural and harmless products for the environment and restorer is taking place in the field of Cultural Heritage restoration. In this sense, wheat, rice and corn starches as adhesives, have suitable characteristics without toxicity risks. A new starch in this field, is the Kudzu, an almost pure compound (99.5% starch) that is processed by a natural way from a plant called Pueraria lobata. This is a preliminary study of the potential use of Kudzu starch for the restoration of Cultural Heritage, focusing, firstly, in its capacity as adhesive through a comparative evaluation with common starches. The accelerated aging process carried out proved that Kudzu ensures optimal chromatic behaviour. On the other hand, the main problem in starch paste is the biological colonization. The daidzein, a natural antimicrobial compound implicit in Kudzu starch, confirmed the resistance to microorganism in this preliminary approach. The evaluation of the adhesive capacity, and the reversibility of the starches, suggest that Kudzu starch is a valid adhesive in the field of paper restoration. Thus, the potential of this starch in the conservation of Cultural Heritage is evidenced and its use as cleaner, resistance to biological colonization and consolidant is promising.

SuperCam Calibration Targets: Design and Development

SuperCam is a highly integrated remote-sensing instrumental suite for NASA's Mars 2020 mission. It consists of a co-aligned combination of Laser-Induced Breakdown Spectroscopy (LIBS), Time-Resolved Raman and Luminescence (TRR/L), Visible and Infrared Spectroscopy (VISIR), together with sound recording (MIC) and high-magnification imaging techniques (RMI). They provide information on the mineralogy, geochemistry and mineral context around the Perseverance Rover. The calibration of this complex suite is a major challenge. Not only does each technique require its own standards or references, their combination also introduces new requirements to obtain optimal scientific output. Elemental composition, molecular vibrational features, fluorescence, morphology and texture provide a full picture of the sample with spectral information that needs to be co-aligned, correlated, and individually calibrated. The resulting hardware includes different kinds of targets, each one covering different needs of the instrument. Standards for imaging calibration, geological samples for mineral identification and chemometric calculations or spectral references to calibrate and evaluate the health of the instrument, are all included in the SuperCam Calibration Target (SCCT). The system also includes a specifically designed assembly in which the samples are mounted. This hardware allows the targets to survive the harsh environmental conditions of the launch, cruise, landing and operation on Mars during the whole mission. Here we summarize the design, development, integration, verification and functional testing of the SCCT. This work includes some key results obtained to verify the scientific outcome of the SuperCam system.

A non-invasive spectroscopic study to evaluate both technological features and conservation state of two types of ancient Roman coloured bricks

The study of both original and decaying compounds is relevant in understanding the chemistry behind the deterioration processes, above all in open museum contexts where environmental stressors affect the artefacts. In this sense, a combination of non-invasive spectroscopy techniques (Raman spectroscopy, μ-X-ray fluorescence and X-ray diffraction) was applied on an ancient Roman building (130 CE), the "Casa di Diana" Mithraeum at Ostia Antica archaeological site. The aim is to study the raw materials, manufacturing and decaying products of the two observed types of Roman fired bricks (red and yellow) that compose the building. The present study estimates an illite raw material of carbonate-bearing marine clay likely referring to the common deposits of central/southern Italy, which contain calcite as accessory phase and a-plastic fraction constituted by quartz, feldspar and opaques. This clay material was added with volcanic temper characterised by abundant clinopyroxene and analcime (from analcimization of leucite) that are typical of the Roman Province volcanism. The firing would be probably the result of oxidizing conditions, as proved by the hematite presence. Thanks to the existence of specific neoformed mineral phases during firing it was possible to assess different temperatures ranges. In detail, the red/orange bricks, for the existence of gehlenite (formed from calcite and its reaction with silicates), were fired at 800-900 °C range; whereas, the yellow ones are characterised by the lack of gehlenite and the disappearance of illite/muscovite, which indicates firing temperature at over 900 °C. Regarding the decaying products, the gypsum covers most of the surface of most bricks, both red and the yellow ones, but these latter are more susceptible to environmental stressors (sulphates and carbonates). Therefore, this work points out how by integrated non-invasive approaches it is possible trace back to original firing temperature, technology of manufacture, interpreting ceramic data.

In-situ multianalytical approach to analyze and compare the degradation pathways jeopardizing two murals exposed to different environments (Ariadne House, Pompeii, Italy)

This study aimed at using portable analytical techniques to characterize original and decayed materials from two murals paintings of Ariadne House (archaeological site of Pompeii, Italy) and define the degradation pathways threatening their conservation. The first wall, located in an outdoor environment, has been directly exposed to degradation processes triggered by weathering and atmospheric pollution. The second wall, placed in a basement under the ground floor, has been constantly sheltered from sunlight exposure and drastic temperature fluctuations. The analytical data obtained in-situ by using Raman spectroscopy and Laser Induced Breakdown Spectroscopy (LIBS) correlates the degradation patterns affecting the two surfaces to their environmental context. The deterioration processes detected on the outdoor wall, which entailed the complete loss of the paint layer, were mostly related to leaching and thermal fluctuation phenomena. The mural painting from the basement instead, showed deep degradation issues due to soluble salt infiltration and biological colonization. The results obtained from this unique case of study highlight the indispensable role of in-situ spectroscopic analysis to understand and predict the degradation pathways jeopardizing the cultural heritage and provide to the Archaeological Park of Pompeii important inference to consider in future conservation projects.

Resonance Raman imaging as a tool to assess the atmospheric pollution level: carotenoids in Lecanoraceae lichens as bioindicators

Raman spectroscopy differentiation of carotenoids has traditionally been based on the ν 1 position (C = C stretching vibrations in the polyene chain) in the 1500-1600 cm(-1) range, using a 785 nm excitation laser. However, when the number of conjugated double bonds is similar, as in the cases of zeaxanthin and β-carotene, this distinction is still ambiguous due to the closeness of the Raman bands. This work shows the Raman results, obtained in resonance conditions using a 514 mm laser, on Lecanora campestris and Lecanora atra species, which can be used to differentiate and consequently characterize carotenoids. The presence of the carotenoid found in Lecanoraceae lichens has been demonstrated to depend on the atmospheric pollution level of the environment they inhabit. Astaxanthin, a superb antioxidant, appears as the principal xanthophyll in highly polluted sites, usually together with the UV screening pigment scytonemin; zeaxanthin is the major carotenoid in medium polluted environments, while β-carotene is the major carotenoid in cleaner environments. Based on these observations, an indirect classification of the stress suffered in a given environment can be assessed by simply analysing the carotenoid content in the Lecanoraceae lichens by using resonance Raman imaging.

Focused ultrasound solid-liquid extraction for the determination of organic biomarkers in beachrocks

Beachrocks are consolidated coastal sedimentary formations resulting mainly from the relative rapid cementation of beach sediments by different calcium carbonate polymorphs. Although previous works have already studied the elemental composition and the mineral phases composing these cements, few of them have focused their attention on the organic matter present therein. This work describes an extraction methodology based on focused ultrasound solid-liquid extraction (FUSLE), followed by analysis using large volume injection (LVI) in a programmable temperature vaporizer (PTV) combined with gas chromatography-mass spectrometry (GC-MS) in order to determine organics such as polycyclic aromatic hydrocarbons (PAHs) and biomarkers (hopanes), which can increase and confirm the information obtained so far. This goal has been achieved after the optimization of the main parameters affecting the extraction procedure, such as, extraction solvent, FUSLE variables (amplitude, extraction time and pulse time) and also variables affecting the LVI-PTV (vent time, injection speed and cryo-focusing temperature). The developed method rendered results comparable to traditional extraction methods in terms of accuracy (77-109%) and repeatability (RSD<23%). Finally, the analyses performed over real beachrock samples from the Bay of Biscay (Northern Spain) revealed the presence of the 16 EPA priority PAHs, as well as some organic biomarkers which could increase the knowledge about such beachrock formation.

A chemical status predictor. A methodology based on World-Wide sediment samples

As a consequence of the limited resources of underdeveloped countries and the limited interest of the developed ones, the assessment of the chemical quality of entire water bodies around the world is a utopia in the near future. The methodology described here may serve as a first approach for the fast identification of water bodies that do not meet the good chemical status demanded by the European Water Framework Directive (WFD). It also allows estimating the natural background (or reference values of concentration) of the areas under study using a simple criterion. The starting point is the calculation the World-Wide Natural Background Levels (WWNBLs) and World-Wide Threshold Values (WWTVs), two indexes that depend on the concentration of seven elements present in sediments. These elements, As, Cd, Cr, Cu, Ni, Pb and Zn, have been selected taking into account the recommendations of the UNEP (United Nations Environment Programme) and USEPA (United States Environmental Protection Agency), that describe them as elements of concern with respect to environmental toxicity. The methodology has been exemplified in a case study that includes 134 sediment samples collected in 11 transitional water bodies from 7 different countries and 4 different continents. Six of the water bodies considered met the good chemical status demanded by the WFD. The rest of them exceeded the reference WWTVs, at least for one of the elements. The estuaries of the Nerbioi-Ibaizabal (Basque Country) and Cavado (Portugal), the sea inlet of Río San Pedro (Spain), the Sepetiba Bay (Brazil) and the Yucateco lagoon (Mexico) belong to that group.

Recrystallization and stability of Zn and Pb minerals on their migration to groundwater in soils affected by Acid Mine Drainage under CO2 rich atmospheric waters

The extent of vertical contamination is intimately related to the soil solution and surface chemistry of the soil matrix with reference to the metal and waste matrix in question. The present research demonstrated the impact that the dissolved CO2 of the meteoric waters, which acidify the environment with pH values below 4, has in the increase of the metal mobility. Although under the given conditions the Zn remains mainly dissolved, the initial PbS and ZnS have evolved into newly formed secondary carbonates and sulphates (i.e., hydrozincite, gunningite, hydrocerussite) that can be found in the efflorescences. The chemical simulation done on the weathering of the original sulphide ores for the formation of these secondary minerals has proved the transient storage mainly of Pb. Nonetheless, many of the minerals formed inside the galleries will be easily dissolved in the next rains and release in an ionic form to the groundwater. The analytical procedure exposed has been proved to be useful not only for the characterization of AMD but also for the prediction of the mobility of metals.

The problem of sampling on built heritage: a preliminary study of a new non-invasive method

The relevance of a risk assessment of the built heritage was clearly justified due to the fact that it acts as a pollutant repository and hazardous pollutants have the capacity to penetrate into materials. However, the limitation of the sampling processes due to the high value of the built heritage makes a correct evaluation difficult. For that reason, in the present work, the potential of agar gels as non-invasive samplers of built heritage deterioration products, like crusts and patinas, was evaluated. Different gels of agar and Carbopol® (as control gel) were applied on these built surfaces considering several factors: the treatment time, the effectiveness of the addition of EDTA (ethylenediaminetetraacetic acid, C10H16N2O8) and its concentration and the use of a buffer at pH 7.5. All these factors were evaluated in order to determine the capacity of these gels as sampling systems under non-controlled atmospheric conditions. The results obtained in the assays were evaluated by visual examination, by evolution of pH and by the most important techniques used in the risk assessment analysis of the built heritage (Raman spectroscopy, scanning electron microscope (SEM)/energy dispersive X-ray (EDX) and inductively coupled plasma mass spectrometry (ICP-MS)). In this evaluation, the agar gels showed an intrinsic capacity as sampler with respect to the gel Carbopol® and thus, the best option between the studied gels consisted on agar gels with 2 % of EDTA and the longest application time. On the whole, the agar gels showed an interesting potential as non-invasive samplers of built heritage deterioration materials which should be studied more in depth.

Buildings as repositories of hazardous pollutants of anthropogenic origin

In the present work the pollutant content of diverse building materials was evaluated by the combination of spectrometric and chromatographic techniques. A first non-destructive analysis carried out by μ-XRF and Raman spectroscopy revealed a high impact of pollutants, which reached depths higher than 6mm. The quantitative analyses pointed out that black crust as accumulation nucleus where concentration values up to 3408 mg/kg of lead, 752 mg/kg of chromium or 220 mg/kg of arsenic, high amounts of diverse sulphates and nitrates as well as substantial amounts of polycyclic aromatic hydrocarbons (PAHs) of a clear pyrolytic source were determined. On the other hand, samples without black crust showed also a surprising soluble salt content up to 5%. Polychlorinated biphenyls (PCB) were found to be absent in all material types. The chemometric analysis of the quantitative results revealed that the accumulation capacity and the subsequent pollutant content depends on the type of construction materials, being mortars the most susceptible.

Optimization of two methods based on ultrasound energy as alternative to European standards for soluble salts extraction from building materials

The Italian recommendation NORMAL 13/83, later replaced by the UNI 11087/2003 norm, were used as standard for soluble salts extraction from construction materials. These standards are based on long-time stirring (72 and 2h, respectively) of the sample in deionized water. In this work two ultrasound based methods were optimized in order to reduce the extraction time while efficiency is improved. The instrumental variables involved in the extraction assisted by ultrasound bath and focused ultrasounds were optimized by experimental design. As long as it was possible, the same non-instrumental parameters values as those of standard methods were used in order to compare the results obtained on a mortar sample showing a black crust by the standards and the optimized methods. The optimal extraction time for the ultrasounds bath was found to be of two hours. Although the extraction time was equal to the standard UNI 11087/2003, the obtained extraction recovery was improved up to 119%. The focused ultrasound system achieved also better recoveries (up to 106%) depending on the analyte in 1h treatment time. The repeatabilities of the proposed ultrasound based methods were comparables to those of the standards. Therefore, the selection of one or the other of the ultrasound based methods will depend on topics such as laboratory facilities or number of samples, and not in aspects related with their quality parameters.

Beachrock formation in temperate coastlines: examples in sand-gravel beaches adjacent to the Nerbioi-Ibaizabal Estuary (Bilbao, Bay of Biscay, North of Spain)

Beachrocks are coastal sedimentary formations resulting from a relative rapid cementation of beach sediments by the precipitation of carbonate cements. These lithified structures are not usually observed at temperate settings. The present work is focused on the occurrence of a significant intertidal cementation in sand-gravel beaches formed among 43°N latitude coastline, close to the Nerbioi-Ibaizabal estuary (Bilbao, Bay of Biscay, North of Spain). Raman micro-spectroscopy combined with SEM-EDX analyses and petrographic descriptions have been applied for the determination of the cement generations and the cemented materials compositions of the beachrock outcrops. In general terms, the cements described were: Cement Generation 1 (CG 1, aragonite, high-magnesium calcite and silicate mixtures), Cement Generation 2 (CG 2, aragonite) and Cement Generation 3 (CG 3, mixtures of CaCO(3) polymorphs and iron oxides). The rest of the interstitial porosity of the rocks appeared either empty or filled with heterogeneous cemented mixtures of previously reworked compounds. The mineralogy, the regular distribution and the isopachous character of the carbonate cements together with the accurate cementation at advanced seaward bands propose a possible marine-phreatic context for the beachrock formation. However, the impure cements and the materials covering the interstitial porosity seem to be the result of both, the weathering actions consequences and the surface alterations of specific grains. Moreover, the presence of modern cemented materials (e.g. slag, bricks and pebbles) suggest a recent formation of the phenomenon.

Micro-Raman spectroscopic identification of natural mineral phases and their weathering products inside an abandoned zinc/lead mine

Mining activities provide a good source of minerals of different nature. On the one hand, the primary minerals for whose formation a geological time-scale is required. On the other hand, secondary minerals, formed from removed products after the earlier weathering and alteration states. These are characteristic of the local geology and the environment context that commonly appears due to the low chemical stability of their original primary minerals. This work shows how quickly the reactions promoting secondary minerals may have taken place, due to the fact that these were found in newly formed solid materials called efflorescences. To achieve this purpose, the sampling is crucial. It was carried out in such a way that tried to guarantee that the samples collected consisted in the very top soil matter (first 2 cm depth). Thus, unlike the deeper soil, the material analysed may have been newly formed due to the interactions that they had with the place weathering agents (i.e. air oxygen, humidity, and microbial activities). Raman spectroscopy has emerged as a good and fast non-destructive technique that provides molecular information of the local mineralogy without the need of any pre-treatment of the samples. At the same time, the work looked for information on the variety of non-stable lead and-or zinc containing minerals due to the possible health and environmental risks they convey. Among the different minerals identified, 16 were of primary nature while 23 may be classified as secondary minerals, probably formed in the last decades as the result of the extractive activities.

Brazilian coal mining residues and sulphide oxidation by Fenton's reaction: an accelerated weathering procedure to evaluate possible environmental impact

Fenton's reaction is proposed as an accelerated weathering test for sulphides associated with Brazilian Coal Mining Residues (CMR), that are exposed to oxygen and water during the mining of coal. TEM and SEM/EDX were used to evaluate the nature, occurrence and distribution of minerals in remaining coals and other lithological units, before and after applying the test. Oxidation of CMRs was examined by analyzing soluble sulphur (sulphate) and dissolved metals by ICP-MS or ICP OES. As dissolved sulphate increases, dissolved Zn, Cd, Cu and Co concentrations increase, leading to undetectable amounts in the remaining solid phases; dissolved Ni and Mn also increase with the mobilized sulphur, but the remainder in the solids is the most important fraction; Fe and Pb are not mobilized due to precipitation as jarosite or hematite in the case of Fe or as sulphate in the case of Pb. Agreement between the observed results and the predictions by geochemical modelling is discussed.

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

A 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 (KAlSi(3)O(8)) 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 (Fe(2)(SO(4))(3)·9H(2)O) 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.

Trace metals in oysters, Crassotrea sps., from UNESCO protected natural reserve of Urdaibai: space-time observations and source identification

The seasonal and spatial variability of trace metal concentrations of oyster tissues (Crassostea sps.) was studied. The samples were collected between 2002 and 2004 along the Urdaibai estuary (Murueta, Kanala and Arteaga). The seasonal influence on some metal concentrations (higher values in spring-summer season than in autumn-winter season) is more pronounced than the local site-specific influence. Furthermore, within each location a significant time-specific dependence on the trace metal concentration variations can be detected. Substantially higher concentrations of Zn (445.5-2,403.3 mg kg(-1)) and Mn (29.4-169.6 mg kg(-1)) were recorded in oysters inhabiting estuarine locations, possibly indicating a markedly higher natural bioavailability at these locations. Principal component analysis demonstrated that oysters could be separated depending on the inhabiting areas: Sn for Murueta, essential metals for Kanala, and Co and Cd for Arteaga sampling points, respectively.

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 (micro-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 characterisation of moonmilk deposits in Pozalagua tourist cave (Karrantza, Basque Country, North of Spain)

Composition of moonmilk deposits located in different zones of the tourist Dolomite Cave of Pozalagua (Karrantza, Basque Country, North of Spain) was established by Raman spectroscopy. The deposits were located in column bases and detached rocks near a gour full of water or a dripping zone. Hydromagnesite (Mg(5)(CO(3))(4)(OH)(2).4H(2)O) with a strong Raman band at 1116 cm(-1) and weaker ones at 1522vw, 1487vw, 1452vw, 756w, 727w, 466w, 434w, 371w, 327m, 291w, 258w, 247vw and 230 m cm(-1) was found as the main component of the moonmilk. Aragonite is the unique calcium carbonate compound that sometimes composes the moonmilk but always together with the hydromagnesite. Among non-carbonate minerals, some nitrates (nitrocalcite, niter, nitromagnesite, nitratine and gwihabaite) and sulphates (arkanite) were also identified as minor compounds. Most of the deposits were matt white and pasty, but occasionally some samples appear greyish on the surface. In these samples, carbon particles were also found, apart from the above, and Raman shift changes were observed in the hydromagnesite spectra. Apart from the elements involved in the mentioned minerals, Si, Fe, Mn, Zn and Ti were identified by X-ray microfluorescence as trace elements and the results were correlated with mineral compositions found by Raman measurements. Furthermore, quantification of the soluble salts of moonmilk deposits was carried out by ionic chromatography and the results were chemometrically treated to find correlations among soluble ions and the composition of the mineral phases spectroscopically characterised.

An integrated analytical approach to diagnose the conservation state of building materials of a palace house in the metropolitan Bilbao (Basque Country, North of Spain)

Raman microprobe spectroscopy and microX-ray fluorescence were used to analyse the original composition and degradation products of the limestone and the sandstones from the facades of one historical building. Carbon particles, gypsum (CaSO(4).2H(2)O) and some nitrate compounds were determined by Raman measurements, while elemental characterisation carried out by microXRF revealed the presence of lead, sulphur and copper as pollutants. On the one hand, the grey sandstone is the most deteriorated and in some cases pollutants reach 3 cm depth. On the other hand, quantification of soluble salts (chlorides, sulphates, nitrates, nitrites, fluorides and carbonates) was accomplished by ion chromatography. Chloride and sulphates are not significant soluble salts in the façades of the building, but the amount of nitrate is even 136 g kg(-1) in some of the most deteriorated samples and of 147 g kg(-1) in black-crusts. Finally, organic compounds (mainly PAHs) were characterised by GC-MS. Concentrations higher than 20 ppm of total PAHs were measured in the black-crusts of the rain-protected facades. The presence of certain PAHs indicated combustion of fuels as the main source of deterioration for the palace house building materials.

Improvements in the wallpaper industry during the second half of the 19th century: micro-Raman spectroscopy analysis of pigmented wallpapers

Scientific studies of the pigments used in the manufacturing process of some pigmented wallpapers are presented in this work. Non-destructive micro-Raman spectroscopy was selected for this purpose, and provides important information about how the 19th century wallpaper industry incorporated new materials in their works and designs. At the same time, analysis can help to date the samples of uncatalogued wallpapers. Chrome yellow, burnt Sienna, Prussian blue, ultramarine blue, red lead, carbon black, calcium carbonate, red iron oxide and a red organic pigment were identified. According to the palette used, as well as to the manufacturing process, the wallpapers in this study can be dated to the second half of the 19th century.

On-line FT-Raman and dispersive Raman spectra database of artists’ materials (e-VISART database)

Raman spectroscopy has been widely applied in the analysis of different types of artwork. This technique is sensitive, reliable, non-destructive and can be used in situ. However, there are few references in the literature regarding specific Raman spectra libraries for the field of artwork analysis. In this paper, the development of two on-line databases with Fourier transform Raman (FT-Raman; 1064 nm) and dispersive Raman (785 nm) spectra of materials used in fine art is presented; both are implemented in the e-vibrational spectroscopic databases of artists' materials database (e-VISART). The database provides not only spectra, but also information about each pigment. It must be highlighted that for each pigment or material several spectra are available from different dealers. Some of the FT-Raman spectra available in the e-VISART database have not been published until now. Some examples in which the e-VISART database has been successfully used are presented.

Raman fibre optic approach to artwork dating

Raman micro-probe spectroscopy has been applied to the analysis of a non catalogued hand-crafted wallpaper during its restoration process. The analysis has been totally non-destructive without the necessity of taking any sample. The artwork showed a great chromatic palette having been detected the presence of calcium carbonate, Prussian blue, ultramarine blue, gypsum (CaSO4.2H2O), minium (Pb3O4), vermilion (HgS), chrome orange (CaCO3), chrome yellow (PbCrO4), barium sulphate and carbon black (C). From the spectroscopic analysis the date of its manufacturing has been set between 1828 and 1830, introduction of chrome yellow and orange, as well as artificial ultramarine blue, and 1840, when continuous industrial wallpapers were extensively manufactured in Europe.

Micro-Raman analysis of coloured lithographs

Raman micro-spectroscopy was chosen for analysis and identification of the pigments present in four nineteenth-century hand-coloured lithographs, as this technique has several advantages over others for this purpose. The possibility of performing completely non-destructive analysis without any sampling is probably one of its most favourable qualities for art analysis. Raman spectroscopy can also be used to determine some pigments that cannot be detected using FTIR, such as vermilion, carbon blacks, cadmium pigments, etc. Among others, Prussian blue, ultramarine blue, carbon black, chrome yellow, yellow ochre, red lead, red iron oxide, burnt Sienna, indigo blue, chrome orange, phthalocyanine green, and some other organic pigments, were determined in the specimens. The results obtained have led to doubts about the age of the lithographs.

Analysis of bulk and inorganic degradation products of stones, mortars and wall paintings by portable Raman microprobe spectroscopy

This work reports the use of a portable Raman microprobe spectrometer for the analysis of bulk and decaying compounds in carbonaceous materials such as stones, mortars and wall paintings. The analysed stones include limestone, dolomite and carbonaceous sandstone, gypsum and calcium oxalate, both mono- and dihydrated, being the main inorganic degradation products detected. Mortars include bulk phases with pure gypsum, calcite and mixtures of both or with sand, soluble salts being the most important degradation products. The pigments detected in several wall paintings include Prussian blue, iron oxide red, iron oxide yellow, vermilion, carbon black and lead white. Three different decaying processes have been characterised in the mortars of the wall paintings: (a) a massive absorption of nitrates that reacted with calcium carbonate and promoted the unbinding of pigment grains, (b) the formation of black crusts in the vault of the presbytery and (c) the thermodecomposition of pigments due to a fire.

Automation of a procedure to find the polynomial which best fits (kappa, c1, c2, T) data of electrolyte solutions by non-linear regression analysis using MATHEMATICA software

A MATHEMATICA package, 'CONDU.M', has been developed to find the polynomial in concentration and temperature which best fits conductimetric data of the type (kappa, c, T) or (kappa, c1, c2, T) of electrolyte solutions (kappa: specific conductivity; ci: concentration of component i; T: temperature). In addition, an interface, 'TKONDU', has been written in the TCL/Tk language to facilitate the use of CONDU.M by an operator not familiarised with MATHEMATICA. All this software is available on line (UPV/EHU, 2001). 'CONDU.M' has been programmed to: (i) select the optimum grade in c1 and/or c2; (ii) compare models with linear or quadratic terms in temperature; (iii) calculate the set of adjustable parameters which best fits data; (iv) simplify the model by elimination of 'a priori' included adjustable parameters which after the regression analysis result in low statistical significance; (v) facilitate the location of outlier data by graphical analysis of the residuals; and (vi) provide quantitative statistical information on the quality of the fit, allowing a critical comparison among different models. Due to the multiple options offered the software allows testing different conductivity models in a short time, even if a large set of conductivity data is being considered simultaneously. Then, the user can choose the best model making use of the graphical and statistical information provided in the output file. Although the program has been initially designed to treat conductimetric data, it can be also applied for processing data with similar structure, e.g. (P, c, T) or (P, c1, c2, T), being P any appropriate transport, physical or thermodynamic property.

Optimization and comparison of MAE, ASE and Soxhlet extraction for the determination of HCH isomers in soil samples

The microwave-assisted extraction (MAE), accelerated solvent extraction (ASE) and Soxhlet extraction of two isomers of hexachlorocyclohexane, alpha-HCH and gamma-HCH, from a polluted landfill soil have been optimized following different experimental designs. In the case of microwave-assisted extraction, the following variables were considered: pressure, extraction time, microwave power, percentage of acetone in n-hexane mixture and solvent volume. When ASE extraction was studied the variables were pressure, temperature and extraction time. Finally, the percentage of acetone in n-hexane mixture and the extraction time were the only variables studied for Soxhlet extraction. The concentrations obtained by the three extraction techniques were, within their experimental uncertainties, in good agreement. This fact assures the possibility of using both ASE and MAE techniques in the routine determination of lindane in polluted soils and sediments.