M?ssbauer studies of Haltern 70 amphorae from Castro do Vieito, North of Portugal, and of amphora sherds from kilns in the Roman provinces Hispania Baetica and Lusitania

Haltern 70 amphora sherds from Castro do Vieito and from kilns in the Roman provinces Baetica and Lusitania were studied by Mössbauer spectroscopy, EDX and XRD. An amphora whose handle was carefully studied must have been fired reducingly at a temperature of or above about 900°C and cooled in oxidizing conditions in the end. Oxidation and hematite formation went hand in hand, and the amount of hematite formed depended sensitively of the speed of penetration of the oxygen and the cooling rate in the interior of the ceramic body.     

Mössbauer and XRD studies of Roman amphorae buried in the sea for two millennia

During the years 2004–2007 many Roman amphora sherds were found in the sea near Cortiçais, off the southern coast of the Peniche peninsula on the Atlantic coast of Portugal. The amphorae are of the Haltern 70 type and stem from a shipwreck that has been dated to the time of the emperor Augustus, between about 15 BC and 15 AD. They were produced in the Roman Province of Baetica in the south of Spain and used to transport wine and other staple foods by sea to other Roman settlements. We have studied several fragments of these amphorae by ⁵⁷Fe Mössbauer spectroscopy and X-ray diffraction in order to look for changes in the ceramic material caused by two millennia of exposure to sea water. For comparison Mössbauer data on a Haltern 70 type amphora handle excavated on land at the site of Castro do Vieito in the north of Portugal were used. The fragments on which we report here are a body sherd and two handles. The sherds show a visible layer structure. The different layers were studied separately. The Mössbauer spectra of the buff surface layers indicate that up to about 60 % of the iron is present as very fine goethite particles, which are superparamagnetic at RT but exhibit magnetically split spectra at 4.2 K. Their blocking temperature is around or even below 50 K. The goethite is too fine grained to be detected by X-ray diffraction. Re-firing experiments confirm the presence of goethite, which is found to convert to hematite between 300 and 600 ^°C. The results show that the iron in the silicate matrix of the ceramic material converts to goethite under the prolonged influence of the sea water, mainly in the outermost several millimetres and apparently depending on the nature of the ceramic material.     

Potentiality of non‐destructive XRF analysis for the determination of Corinthian B amphorae provenance

Numerous samples of archaic transport Corinthian B type amphorae coming from the archaeological excavations of Gela (Sicily, South Italy) were analysed using non‐destructive X‐ray fluorescence (portable InnovX‐Systems ‘Alpha 4000’). Between the 6th and the 5th century BC the Corinthian B amphorae were diffused throughout the Western Mediterranean regions and Greece. Some researchers assigned these amphorae to different production areas, both in Southern Italy and in Greece, although, up to now, the exact attribution to the production centres is still under discussion. In this paper, with the aim to characterise the production sites of this important typology of amphorae, common ceramics, undoubtedly produced in Corinth, Corfù and Sybaris, were also analysed as these important Greek and Magna Graecia cities are considered by the archaeologists as the production centres of ‘Corinthian B’ amphorae. The multivariate analysis, performed on selected elements, clearly distinguished two groups of amphorae which, on the basis of archeological considerations, and by the comparison with reference ceramics, were assigned to Magnae Grecia (Sybaris and surroundings) and Greek productions. Copyright © 2011 John Wiley & Sons, Ltd.     

X‐ray spectromicroscopy in soil and environmental sciences

X‐ray microscopy is capable of imaging particles in the nanometer size range directly with sub‐micrometer spatial resolution and can be combined with high spectral resolution for spectromicroscopy studies. Two types of microscopes are common in X‐ray microscopy: the transmission X‐ray microscope and the scanning transmission X‐ray microscope; their set‐ups are explained in this paper. While the former takes high‐resolution images from an object with exposure times of seconds or faster, the latter is very well suited as an analytical instrument for spectromicroscopy. The morphology of clusters or particles from soil and sediment samples has been visualized using a transmission X‐ray microscope. Images are shown from a cryo‐tomography experiment based on X‐ray microscopy images to obtain information about the three‐dimensional structure of clusters of humic substances. The analysis of a stack of images taken with a scanning transmission X‐ray microscope to combine morphology and chemistry within a soil sample is shown. X‐ray fluorescence is a method ideally applicable to the study of elemental distributions and binding states of elements even on a trace level using X‐ray energies above 1 keV.     

Elemental mapping of frozen‐hydrated cells with cryo‐scanning X‐ray fluorescence microscopy

Visualizing the elemental distributions of cells and tissues is of growing importance in biology and medical science because such data deepen our understanding of the behavior of metal‐binding proteins and ions. Elemental mapping by X‐ray fluorescence analysis with a hard X‐ray nanobeam is very well suited for this purpose owing to its high sensitivity and high resolution. Using this technique, samples must be prepared without artifacts that are caused by treatments such as chemical fixation and staining procedures. In many studies of elemental mapping, sample preparation is not explicitly considered. To overcome this deficiency, we developed a cryo‐scanning X‐ray fluorescence microscope and installed it in the second experimental hutch of BL29XUL of SPring‐8. We used it to observe frozen‐hydrated cells that had been fixed by a quick‐freezing technique to preserve elemental data of the living state at an X‐ray energy of 11.5 keV. The distributions of K, Ca, Fe, Cu and Zn were successfully visualized. The distributions of these elements (especially those of K, Ca and Fe) differed from those in cells fixed with paraformaldehyde. Copyright © 2010 John Wiley & Sons, Ltd.     

X‐ray techniques applied to surface paintings of ceramic pottery pieces from Aguada Culture (Catamarca,Argentina)

X‐ray diffraction (XRD), energy dispersive spectrometry (EDS), x‐ray imaging (XRI) and scanning electron microscopy (SEM) techniques were applied to characterize and differentiate surface paintings of archeological pottery from the Aguada Ambato and Portezuelo styles (Catamarca, Argentina). Standard procedures are not always appropriate for such samples (paint layers are porous, nonplanar and discontinue). Image processing is necessary when chemical contrast is not discriminated. Soft x‐ray lines (e.g. Fe L) are more revealing because those detected come from shallower depths, clearly depicting the composition of the paint layer. These styles differ in mineralogy and chemistry suggesting that they are two distinctive entities not only on their designs but also on the materials chosen and the technology used. Aguada Portezuelo paints contain Ca (white), Fe? Mn (black), Fe? Mn? Ca (dark reddish) and Fe? Ca (reddish). The white ones correspond to gehlenite, a firing product (possible firing temperature ≥900–1000 °C); calcite and CaO occur in cases of firing temperatures <900 °C. Aguada Ambato presents difficulties for paint discrimination; only EDS spectra show slight differences. White paint from Tricolor Ambato contains mainly Pb‐phases (hatchite, anglesite, plumalsite), reddish paint resembles the paste (～Fe, hematite); reddish surfaces may have not been painted but polished. Black paint has scarce Mn–minerals. On Black Incised sherds no particular phase was identified suggesting possible organic pigments or resulting from the firing technique. The chemistry and mineralogy of the paste almost always overlap that of the paints; painted layer is irregular and partially worn by years of burial. Copyright © 2009 John Wiley & Sons, Ltd.     

Synchrotron X‐ray microfluorescence measurement of metal distributions in Phragmites australis root system in the Yangtze River intertidal zone

This study investigates the distributions of Br, Ca, Cl, Cr, Cu, K, Fe, Mn, Pb, Ti, V and Zn in Phragmites australis root system and the function of Fe nanoparticles in scavenging metals in the root epidermis using synchrotron X‐ray microfluorescence, synchrotron transmission X‐ray microscope measurement and synchrotron X‐ray absorption near‐edge structure techniques. The purpose of this study is to understand the mobility of metals in wetland plant root systems after their uptake from rhizosphere soils. Phragmites australis samples were collected in the Yangtze River intertidal zone in July 2013. The results indicate that Fe nanoparticles are present in the root epidermis and that other metals correlate significantly with Fe, suggesting that Fe nanoparticles play an important role in metal scavenging in the epidermis.     

Micro‐EDXRF investigation of Chalcolithic gold ornaments from Portuguese Estremadura

Chalcolithic gold artefacts assigned to the Bell Beaker Culture in Portuguese Estremadura were analysed by micro‐energy dispersive X‐ray fluorescence spectrometry. These high‐status jewels comprise beads of tubular, spiral and double‐conical type, a spiral ring and a wire fragment. The collection is mainly composed of gold with 8.7–16.3 wt% Ag and <0.04 wt% Cu. Additionally, there is a typologically uncommon double‐conical bead showing a lower Ag content (6.7 wt%). The relative intensity of the Ag‐Kα and Ag‐Lα X‐rays from artefacts established the existence of a surface layer depleted in silver, while the reasonable effective penetration depth of the Ag‐Kα (about 25–30 μm) provided suitable results for such high fineness gold alloys. A uniform Au–Ag composition at the joint indicates that the double‐conical bead was made by joining two sheets without solder. Overall, the collection shows a composition that is similar to known Chalcolithic gold in Portuguese Estremadura but different from coeval gold in Southwestern Iberian Peninsula. The distinct compositional pattern of Chalcolithic gold in Portuguese Estremadura seems to be inconsistent with the natural variability of silver content in alluvial deposits of gold in Iberian Peninsula, thus suggesting a continuous use of particular sources and limited exchange of nuggets and jewels with the neighbouring region. Copyright © 2017 John Wiley & Sons, Ltd.     

X‐ray spectrometry applied for characterization of bricks of Brazilian historical sites

This paper presents the results of X‐ray fluorescence (XRF) analysis of bricks sampled from historical places in Pernambuco, a state in the northeastern region of Brazil. In this study, twenty bricks found in historical sites were analyzed. Two bricks made in the 17th century, presumably used as ballast in ships coming from Holland, five locally manufactured bricks: one from 18th century, three from 19th century, and one from 20th century, and thirteen bricks collected from a recent Archeological investigation of Alto da Sé, in the town of Olinda. Qualitative determination of the chemical elements present in the samples was undertaken using a self‐assembled portable XRF system based on a compact X‐ray tube and a thermoelectrically cooled Si‐PIN photodiode system, both commercially available. X‐ray diffraction analysis was also carried out to assess the crystalline mineral phases present in the bricks. The results showed that quartz (SiO₂) is the major mineral content in all bricks. Although less expressive in the XRD patterns, mineral phases of illite, kaolinite, anorthite, and rutile are also identified. The trace element distribution patterns of the bricks, determined by the XRF technique, is dominated by Fe and, in decreasing order, by K, Ti, Ca, Mn, Zr, Rb, Sr, Cr, and Y with slight differences among them. Analyses of the chemical compositional features of the bricks, evaluated by principal component analysis of the XRF datasets, allowed the samples to be grouped into five clusters with similar chemical composition. These cluster groups were able to identify both age and manufacturing sites. Dutch bricks prepared with different geological clays compositions were defined.     

Approaches to solid sample preparation based on analytical depth for reliable X‐ray fluorescence analysis

In this paper, we discuss approaches to prepare solid samples for X‐ray fluorescence spectrometry (XRF). Although XRF can be used to analyze major and minor elements in various solid samples including powders and grains without dissolution techniques, to obtain reliable XRF results, the prepared sample must meet certain criteria related to homogeneity, particle size, flatness, and thickness. The conditions are defined by the analytical depth of fluorescent X‐rays from analytes, and the analytical depth can be estimated from the X‐ray absorption related to the energy of each X‐ray and the composition and density of the sample. For example, when the sample flatness and particle size are less than the analytical depth and the sample possesses homogeneity within a depth less than the analytical depth, the XRF results are representative of the entire sample. Furthermore, an appropriate sample thickness that is larger than the analytical depth or constant can prevent changes in fluorescent X‐ray intensity with variations in sample thickness. To obtain accurate and reproducible measurements, inhomogeneous solid samples must be pulverized, homogenized, and prepared as loose powder, powder pellets, or glass beads. This paper explains the approaches used to prepare solid samples for XRF analysis based on the analytical depths of fluorescent X‐rays. Copyright © 2016 John Wiley & Sons, Ltd.     

Energy value determinations of industrialized foods: the potential of using X‐ray spectroscopy and partial least squares

This work reports the use of multivariate calibration models to determine energy values (EV) of industrialized dried vegetable products prepared for human consumption. These methods use energy dispersive X‐ray fluorescence spectra allied to chemometrics of the respective samples to substitute conventional EV determinations that are subject to several laborious steps. The samples are grouped in accordance with their principal raw material (corn, wheat, soy, milk and cassava). The chemometric tools applied reveal that the X‐ray scattering spectrum region furnishes the main contribution to the calibration models, where the presence of organic compounds is manifested through small variations in X‐ray scattering effects. These results are expected because EV values are based on the organic contents. The EV determination is fast, does not generate residuals and does not involve toxic reagents. The good results of the validation process (deviations < 14%) indicate that this is an alternative to conventional analytical methods and is very attractive for routine analysis. Copyright © 2010 John Wiley & Sons, Ltd.     

XRF法在四川盆地须家河组沉积相研究中的应用

X射线荧光光谱仪在地质样品测定上的应用还不是很广泛,而将X射线荧光光谱法应用到沉积相的研究中则更少。将X射线荧光光谱法(XRF)应用到川中地区上三叠统须家河组二段沉积环境及古气候的识别中,针对四川盆地上三叠统须家河组二段沉积相及沉积环境有争议的问题,特别是须二段地层属于陆相沉积还是海相沉积的问题,采集了四川盆地内四个有代表性地区的须家河组样品,采用X 射线荧光光谱法分析须家河组各段沉积物的元素含量及变化特征,并根据不同相带及沉积环境的元素含量标志,定量分析须家河组沉积相带与沉积环境。研究结果表明： 须家河组二段的Sr/Ba值、Mn/Fe 值和Sr/Ca值均落在陆相沉积的范围内,且与须家河组三-四段的元素含量特征无明显差异,Sr/Cu元素比分析结果表明须家河组沉积时期为温暖—湿润的古气候环境,结果证明四川盆地上三叠统须家河组二段属于温湿气候下的陆相沉积,且与须家河组三-四段沉积环境相类似。X射线荧光光谱法与常规化学分析法实验结果相对误差小于3%,该方法简单易行,为沉积相及沉积环境的识别提供了一种简单、可行且能够定量分析的研究方法。为解决有争议地层沉积相的问题提供了一种较可行的新方法,推动了X射线荧光光谱分析法在地质上的应用。     

Sample thickness and quantitative concentration measurements in Br K‐edge XANES spectroscopy of organic materials

While XANES spectroscopy is an established tool for quantitative information on chemical structure and speciation, elemental concentrations are generally quantified by other methods. The edge step in XANES spectra represents the absolute amount of the measured element in the sample, but matrix effects and sample thickness complicate the extraction of accurate concentrations from XANES measurements, particularly at hard X‐ray energies where the X‐ray beam penetrates deeply into the sample. The present study demonstrates a method of quantifying concentration with a detection limit approaching 1 mg kg^?1 using information routinely collected in the course of a hard X‐ray XANES experiment. The XANES normalization procedure unambiguously separates the signal of the absorber from any source of background. The effects of sample thickness on edge steps at the bromine K‐edge were assessed and an empirical correction factor for use with samples of variable mass developed.     

Measuring partial fluorescence yield using filtered detectors

Typically, X‐ray absorption near‐edge structure measurements aim to probe the linear attenuation coefficient. These measurements are often carried out using partial fluorescence yield techniques that rely on detectors having photon energy discrimination improving the sensitivity and the signal‐to‐background ratio of the measured spectra. However, measuring the partial fluorescence yield in the soft X‐ray regime with reasonable efficiency requires solid‐state detectors, which have limitations due to the inherent dead‐time while measuring. Alternatively, many of the available detectors that are not energy dispersive do not suffer from photon count rate limitations. A filter placed in front of one of these detectors will make the energy‐dependent efficiency non‐linear, thereby changing the responsivity of the detector. It is shown that using an array of filtered X‐ray detectors is a viable method for measuring soft X‐ray partial fluorescence yield spectra without dead‐time. The feasibility of this technique is further demonstrated using α‐Fe₂O₃ as an example and it is shown that this detector technology could vastly improve the photon collection efficiency at synchrotrons and that these detectors will allow experiments to be completed with a much lower photon flux reducing X‐ray‐induced damage.     

Multivariate analysis of hyperspectral hard X‐ray images

This article describes methods to analyse and process hyperspectral hard X‐ray imaging data. We focus on the use of multivariate techniques that exploit the spectral information to make informed decisions on the material content within each pixel of an X‐ray image. These analysis methods have the ability to auto‐segment data without prior knowledge of the sample composition or structure, and are particularly useful for studying completely unknown, diluted or complex specimens. We demonstrate the methods on a variety of hard X‐ray images including X‐ray fluorescence and absorption data recorded using a hard X‐ray imaging spectrometer. The multivariate methods described are very powerful with the ability to segment, distinguish and, in some cases, identify different materials within a single X‐ray image. Potential uses of hyperspectral X‐ray imaging are discussed varying from materials science to industrial or security applications. Copyright © 2013 John Wiley & Sons, Ltd.     

Element‐selective three‐dimensional imaging of microparticles with a confocal micro‐PIXE arrangement

A detailed report about the confocal experiment and the corresponding data analysis is presented to determine local atomic concentrations in a thick sample with a micrometer resolution. X‐ray emission from a quartz substrate, loaded by aerosol particles, was induced by a scanning proton microbeam and observed by an Si(Li) spectrometer whose field of view was narrowed by a polycapillary lens. A series of X‐ray images were recorded at different positions of the sample along the microbeam axis when the particles were driven through the sensitive microvolume. The concentrations reconstructed in three dimensions were used to extract penetration profiles of the strongest X‐ray emitters (Fe, Ca, S) in an aerosol sample together with the surface profile of the matrix (Si). The results show exponentially dumped depth profiles with characteristic length depending on particle size. Copyright © 2009 John Wiley & Sons, Ltd.     

A miniature closed‐circle flow cell for high photon flux X‐ray scattering experiments

A closed‐circle miniature flow cell for high X‐ray photon flux experiments on radiation‐sensitive liquid samples is presented. The compact cell is made from highly inert material and the flow is induced by a rotating magnetic stir bar, which acts as a centrifugal pump inside the cell. The cell is ideal for radiation‐sensitive yet precious or hazardous liquid samples, such as concentrated acids or bases. As a demonstration of the cell's capabilities, X‐ray Raman scattering spectroscopy data on the oxygen K‐edge of liquid water under ambient conditions are presented.     

A scanning transmission X‐ray microscope at the Pohang Light Source

A scanning transmission X‐ray microscope is operational at the 10A beamline at the Pohang Light Source. The 10A beamline provides soft X‐rays in the photon energy range 100–2000 eV using an elliptically polarized undulator. The practically usable photon energy range of the scanning transmission X‐ray microscopy (STXM) setup is from ～150 to ～1600 eV. With a zone plate of 25 nm outermost zone width, the diffraction‐limited space resolution, ～30 nm, is achieved in the photon energy range up to ～850 eV. In transmission mode for thin samples, STXM provides the element, chemical state and magnetic moment specific distributions, based on absorption spectroscopy. A soft X‐ray fluorescence measurement setup has been implemented in order to provide the elemental distribution of thicker samples as well as chemical state information with a space resolution of ～50 nm. A ptychography setup has been implemented in order to improve the space resolution down to 10 nm. Hardware setups and application activities of the STXM are presented.     

Investigation of a fossilized calotte from Lagoa Santa,Brazil, by EDXRF

The origin of the component parts of a fossilized calotte (skull cap) from Lagoa Santa in Brazil was investigated by using energy‐dispersive x‐ray fluorescence analysis. The specimen was irradiated with a miniaturized and low‐power x‐ray generator (2.25 W, tungsten anode). The calotte and rock samples from the two known sites have a similar chemical composition, especially rich in S, K, Ca, Ti, Mn, Fe, Cu, Zn, Pb, Br, Rb and Sr. These elements are associated with the geological constitution of the limestone complex where the archaeological samples were found. The small differences in the relative amount of each element, especially the Ca/Sr ratio, in different parts of the calotte reinforce the hypothesis that the calotte had been mounted with pieces from different origins. Copyright © 2005 John Wiley & Sons, Ltd.     

Hard X‐ray microbeam lithography using a Fresnel zone plate with a long focal length

Focused hard X‐ray microbeams for use in X‐ray nanolithography have been investigated. A 7.5 keV X‐ray beam generated at an undulator was focused to about 3 µm using a Fresnel zone plate fabricated on silicon. The focused X‐ray beam retains a high degree of collimation owing to the long focal length of the zone plate, which greatly facilitates hard X‐ray nanoscale lithography. The focused X‐ray microbeam was successfully utilized to fabricate patterns with features as small as 100 nm on a photoresist.