Portable X-ray Fluorescence Spectrometry Research Articles

Uncover the mantle: rediscovering Gregório Lopes palette and technique with a study on the painting “Mater Misericordiae”

Gregorio Lopes (c. 1490–1550) was one of the most prominent painters of the renaissance and Mannerism in Portugal. The painting “Mater Misericordiae” made for the Sesimbra Holy House of Mercy, circa 1535–1538, is one of the most significant works of the artist, and his only painting on this theme, being also one of the most significant Portuguese paintings of sixteenth century. The recent restoration provided the possibility to study materially the painting for the first time, with a multianalytical methodology incorporating portable energy-dispersive X-ray fluorescence spectroscopy, scanning electron microscopy–energy-dispersive spectroscopy, micro-X-ray diffraction, micro-Raman spectroscopy and high-performance liquid chromatography coupled to diode array and mass spectrometry detectors. The analytical study was complemented by infrared reflectography, allowing the study of the underdrawing technique and also by dendrochronology to confirm the date of the wooden panels (1535–1538). The results of this study were compared with previous ones on the painter’s workshop, and significant differences and similitudes were found in the materials and techniques used.

Rock varnish on architectural stone: microscopy and analysis of nanoscale manganese oxide deposits on the Smithsonian Castle, Washington, DC

The Smithsonian Institution Building, commonly referred to as the Castle, is located on the National Mall in Washington, DC, and was constructed in the mid-nineteenth century for the purpose of housing all museum and scientific functions for the newly formed institution. Matching gateposts designed by the Castle’s architect were erected more than a century later in the Enid A. Haupt Garden opposite the Castle. Black patches were recently noted on both structures, which are clad with locally quarried Seneca red sandstone. Portable x-ray fluorescence (XRF) spectrometry links the discoloration with elevated Mn concentrations. The discolored patches resemble rock varnish, a Mn-rich coating observed on rock surfaces formed in a variety of environments. Bulk rock and varnish chemistry, in addition to microscopy and microanalysis of the varnish, are presented here. On a bulk chemical basis, the Seneca sandstone is relatively poor in Mn, containing ~500 ppmw. In contrast, the rock varnish is greatly enriched in Mn relative to the stone and to a lesser degree in Pb, Ca, Zn, Cu and Ni. Cross sections of the black encrusted regions show that the stone’s red coloration has been modified by black pigmentation from the surface down to ~250 μm. X-ray diffraction of blackened particles produced no discernable pattern, indicating concentrations below the detection limit, poor crystallinity, or both. Scanning electron microscopy and EDS-based x-ray microanalysis of the uppermost portion of the cross section reveal nanometer scale (<20–200 nm) Mn-rich and clay particles concentrated in a thin film (≪1 μm) at the surface. Additionally, Mn oxide particles decorate the surfaces of fine-grained minerals in sandstone pores within the discolored zone. Imaging and microanalysis of the rock surface reveal that the Mn-rich varnish is a discontinuous film ≪1 μm in thickness with an estimated composition of Na0.2Ca0.1Mg0.1Al0.1Si0.5Mn1.9Fe0.5O6.7. This composition most likely represents a nanoscale mixture of a Mn oxide (e.g., birnessite or todorokite) and an Al-rich silicate mineral. Seneca sandstone on the Smithsonian Castle and gateposts is discolored in patches owing to the Mn-rich phase being deposited into two zones: (1) a vanishingly thin patina, and (2) nanoparticles coating grain boundaries and pores in the uppermost ~200–250 μm of the stone. While the mineralogy is similar to well-studied varnish formed in arid settings, rock varnish on the Smithsonian structures is significantly thinner. Because this architectural rock varnish is young, it may represent the earliest stages of formation of the more commonly described varnishes reported in the literature.

Efficient quantification procedures for data evaluation of portable X-ray fluorescence – Potential improvements for Palaeolithic cave art knowledge

Portable x-ray fluorescence spectrometry (pXRF) has become fundamental in prehistoric research since it enables chemical studies that preserve the integrity of rock art or other investigated archaeological objects. This unique and fragile expression of our ancestors requires the use of non-invasive and non-destructive in situ analytical techniques. This provides significant sources of physicochemical information for enhancing the comprehension of the symbolic and ideological realm of past societies. Thus, XRF data acquired in the field allow giving more detailed insights into the pigment used by Palaeolithic artists, the rock art organisation inside the cave and the different frequentation periods of it. However, if the qualitative study is now well established and routinely used, quantitative evaluation encounters difficulties linked to the context of the study (karstic environment in our case) and the heterogeneous nature of the analysed material (nature of the pigments used, presence of several layers, conservation state of the rock art, type of the rock art support). Moreover, the non-invasive nature of this technique is faced with a large number of data since it offers the acquisition of statistically relevant data by multiple measurements of different spots on the same figure. The present work struggles with the issue of filling the gap of well-adapted quantitative procedures devoted to caves or rock-shelters analyses, and offers efficient tools and methodologies, which take into account the specificities of the studied rock art and its context. Additionally, the evaluation procedures of the high volume of data have to be effective. The analyses of drawings, monochrome and polychrome paintings of three Palaeolithic key cave sites, namely Rouffignac and Font-de-Gaume in Dordogne, Southern-France, and La Garma in Cantabria, Northern Spain, illustrate the new approaches and procedures developed in this study.

Ferrous metallurgy from the Bir Massouda metallurgical precinct at Phoenician and Punic Carthage and the beginning of the North African Iron Age

Excavations of the Phoenician and Punic layers at the site of Bir Massouda in Carthage have provided evidence for ferrous metallurgical activity spanning several centuries. Archaeometallurgical analyses of slagged tuyères, slag, and alloys using optical microscopy, portable X-ray fluorescence spectroscopy (pXRF), and variable pressure scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (VPSEM-EDS) show that Carthaginian smiths were conducting primary smithing and forging of wrought iron and steel. Although the majority of slag specimens are remnant from ferrous production, a few select finds are from bronze recycling. The corpus represents the earliest known ferrous metallurgy in North Africa. As a Phoenician colony then later as an independent imperial metropolis, Carthage specialized in centrally organized ferrous technology at the fringes of the settlement in areas such as Bir Massouda and the Byrsa Hill from before 700 to 146 BC.

Wall painting pigments of Roman Empire age from Syria Palestina province (Israel)

This work is the first step of an extensive project aimed at chemical and mineralogical characterization of pigments of Roman Empire age throughout the provinces. Wall painting materials from two Roman archaeological sites in Israel (the ancient province of Iudaea , later known as Syria Palestina ) were studied: the Roman villa of Lod, dated to the fourth century CE and the synagogue of Migdal, dated between the first century BCE and the second century CE. A total of 165 samples were investigated, producing multi-analytical information from optical microscopy, scanning electron microscopy supported by energy-dispersive X-ray spectroscopy, micro-Raman spectroscopy, X ray diffraction, infra-red spectroscopy, and portable energy-dispersive X-ray fluorescence spectroscopy. This study shows that materials and techniques in the Roman province of Syria Palestina follow Empire tendencies, although advantage was taken also of the local availability of raw materials. Seven different pigments were identified, including Egyptian blue and cinnabar, and the predominant wall painting technique used was fresco occasionally supported by secco retouching.

In-Situ Differentiation of Acidic and Non-Acidic Tundra via Portable X-ray Fluorescence (PXRF) Spectrometry

Frozen soils or those with permafrost cover large areas of the earth's surface and support unique vegetative ecosystems. Plants growing in such harsh conditions have adapted to small niches, which allow them to survive. In northern Alaska, USA, both moist acidic and non-acidic tundra occur, yet determination of frozen soil pHs currently requires thawing of the soil so that electrometric pH methods can be utilized. Contrariwise, a portable X-ray fluorescence (PXRF) spectrometer was used in this study to assess elemental abundances and relate those characteristics to soil pH through predictive multiple linear regressions. Two operational modes, Soil Mode and Geochem Mode, were utilized to scan frozen soils in-situ and under laboratory conditions, respectively, after soil samples were dried and ground. Results showed that lab scanning produced optimal results with adjusted coefficient of determination (R2) of 0.88 and 0.33 and root mean squared errors (RMSEs) of 0.87 and 0.34 between elemental data and lab-determined pH for Soil Mode and Geochem Mode, respectively. Even though the presence of ice attenuated fluoresced radiation under field conditions, adjusted R2 and RMSEs between the datasets still provided reasonable model generalization (e.g., 0.73 and 0.49 for field Geochem Mode). Principal component analysis qualitatively separated multiple sampling sites based on elemental data provided by PXRF, reflecting differences in the chemical composition of the soils studied. Summarily, PXRF can be used for in-situ determination of soil pH in arctic environments without the need for sample modification and thawing. Furthermore, use of PXRF for determination of soil pH may provide higher sample throughput than traditional eletrometric-based methods, while generating elemental data useful for the prediction of multiple soil parameters.

Bog iron ore as a resource for prehistoric iron production in Central Europe — A case study of the Widawa catchment area in eastern Silesia, Poland

Spreading from the Near East in the declining Bronze Age from the 2nd millennium BCE onwards, the technique of iron smelting reached Eastern Silesia, Poland, in approximately the 2nd century BCE (pre-Roman Iron Age). At this time the region of the Widawa catchment area was inhabited by the Przeworsk culture. While the older moraine landscape of the study area lacks ores from geological rock formations, bog iron ores were relatively widespread and, due to their comparatively easy accessibility, were commonly exploited for early iron production. This paper investigates the mineralogical and elemental composition of local bog iron ore deposits and iron slag finds, as a by-product of the smelting process, also taking into account the state of the art in research regarding the formation, distribution and utilization of bog iron ores and considering data from comparative studies.The crystalline mineralogical composition of local bog iron ores is dominated by quartz (SiO2) and goethite (α-FeO(OH)), in contrast to slag samples in which fayalite (Fe2SiO4), wüstite (FeO) and quartz, with traces of goethite, represent the main minerals. Ores and slags are both characterized by notable hematite (Fe2O3), magnetite (Fe3O4) and maghemite (γ-Fe2O3) contents. Analyzed bog iron ore samples show iron contents of up to 64.9mass% Fe2O3 (equivalent to 45.4mass% Fe), whereas the iron contents of bloomery slags vary between 48.7 and 72.0mass% FeO (equivalent to 37.9 and 56.0mass% Fe). A principal component analysis of the element contents, which were quantified by portable energy-dispersive X-ray fluorescence spectrometry, indicates local variations in the elemental composition. The results of this study show that bog iron ores are relatively widely distributed with spatially varying iron contents along the Widawa floodplain but present-day formation conditions, such as changed groundwater levels, are negatively affected by modern land-use practices, such as agriculture and melioration measures.

Evaluation of a new optic-enabled portable X-ray fluorescence spectrometry instrument for measuring toxic metals/metalloids in consumer goods and cultural products

X-ray fluorescence spectrometry (XRF) is a rapid, non-destructive multi-elemental analytical technique used for determining elemental contents ranging from percent down to the μg/g level. Although detection limits are much higher for XRF compared to other laboratory-based methods, such as inductively coupled plasma mass spectrometry (ICP-MS), ICP-optical emission spectrometry (OES) and atomic absorption spectrometry (AAS), its portability and ease of use make it a valuable tool, especially for field-based studies. A growing necessity to monitor human exposure to toxic metals and metalloids in consumer goods, cultural products, foods and other sample types while performing the analysis in situ has led to several important developments in portable XRF technology. In this study, a new portable XRF analyzer based on the use of doubly curved crystal optics (HD Mobile®) was evaluated for detecting toxic elements in foods, medicines, cosmetics and spices used in many Asian communities. Two models of the HD Mobile® (a pre-production and a final production unit) were investigated. Performance parameters including accuracy, precision and detection limits were characterized in a laboratory setting using certified reference materials (CRMs) and standard solutions. Bias estimates for key elements of public health significance such as As, Cd, Hg and Pb ranged from −10% to 11% for the pre-production, and −14% to 16% for the final production model. Five archived public health samples including herbal medicine products, ethnic spices and cosmetic products were analyzed using both XRF instruments. There was good agreement between the pre-production and final production models for the four key elements, such that the data were judged to be fit-for-purpose for the majority of samples analyzed. Detection of the four key elements of interest using the HD Mobile® was confirmed using archived samples for which ICP-OES data were available based on digested sample materials. The HD Mobile® XRF units were shown to be suitable for rapid screening of samples likely to be encountered in field based studies.

Portable x-ray fluorescence in sourcing prehistoric whelk shell artifacts

Portable x-ray fluorescence spectrometry was used to chemically source Busycon shell items from three eastern Tennessee Mississippian period sites. Discriminant function analysis of portable x-ray fluorescence data from control shells from the Atlantic and Gulf coasts indicated variation in strontium levels in Busycon provides a statistically significant predictor of shells’ origins, correctly classifying 86.5% of controls to their coasts of origin. Application of the discriminant function to shell items from Mississippian sites in northeastern and southeastern Tennessee indicated significant differences by region in proportions of artifacts classified as deriving from Atlantic or Gulf coast shell. More than 60% of items from southeastern Tennessee exhibited strontium levels similar to Gulf coast control shells; less than 50% of northeastern Tennessee items were classified as deriving from the Gulf. Variation in ratios of Gulf- to Atlantic-sourced shell artifacts by region is consistent with past predictions that late prehistoric inhabitants of southeastern and northeastern Tennessee participated in different long-distance exchange networks.

Utilizing portable X-ray fluorescence spectrometry for in-field investigation of pedogenesis

In recent years portable X-ray fluorescence (pXRF) spectrometers have been recognised as an in-field tool for soil analyses as they offer rapid, real-time, simultaneous multi-element analysis of soil samples with no or minimal sample preparation. Portable XRF has been used quite extensively to estimate the degree of soil contamination with heavy metals and to measure the concentration of elements in soils that are important for the soil's fertility, but more recently it has also been used to calibrate for a range of soil chemical and physical properties to perform digital soil morphometrics. However, this still relatively new technology also offers an opportunity for soil scientists to investigate processes of pedogenesis in the field, which in turn will complement the in-field descriptions of soils profoundly. Here, we employed a handheld pXRF spectrometer to investigate the pedogenesis pathways and likely parent materials of three different soil types, utilizing elemental concentration data and geochemical indices. Our study site, a property called ‘Nowley’, is situated on the Liverpool Plains in the Spring Ridge district on the North West Slopes of New South Wales, Australia, in one of the most versatile dryland cropping regions of the continent. The variation in soil types and parent materials across the property offers an unique opportunity to study the impact of parent materials and topography on soil formation. A total of three soil pits were excavated to a depth of 1.0m to expose the lower B horizons. Soil pit faces were then scanned at 0.1m depth increments starting from the top of the soil profile to the lowest B horizon exposed. Our results show that elemental data acquired in field condition, which are affected by sample heterogeneities and soil moisture content, are comparable to elemental data acquired in air-dried, ground condition, as geochemical index values show similar trends down the soil profile. We found that the use of pXRF is a very effective in-field tool to assess pedogenic pathways and parent material origin, because of the instant computation of weathering indices and elemental ratios. We conclude that pXRF can be applied successfully and readily to study the soil's weathering history and identify processes of soil formation in the field.

Using portable X-ray fluorescence (pXRF) to determine fecal concentrations of non-absorbable digesta kinetic and digestibility markers in sheep and cattle

Concentration of indigestible markers in feces is routinely used to estimate the digestibility or rate of passage of feed through the gut. Current procedure for measuring fecal marker concentrations is an acid digest before analysis using inductively coupled plasma optical emission spectroscopy (ICP). Portable X-ray fluorescence (pXRF) spectroscopy uses short wavelength X-rays to excite sample material and generate characteristic elemental emissions proportional to the concentration of the element present in ground fecal material. The aim of this study was to measure fecal concentrations of Co, Cr, Ti, and Yb digesta marker by both ICP and pXRF and determine any correlation between the two methods, thereby assessing the potential of using pXRF as a marker analysis method. Silica (Si) concentrations in fecal and feed samples were also measured using both methods. Cattle and sheep feces and various feed samples collect from four separate studies were analyzed for concentrations of Co (CoEDTA), Cr (Cr mordanted fibre), Ti (TiO2), Yb (Yb(III)acetate), and Si using ICP and pXRF. Regression analysis used to assess the relationship between ICP and pXRF determined fecal concentrations indicated strong linear relationships (P<0.01) between pXRF and ICP estimates of Co (r2=1.00), Cr (r2=0.95), Ti (r2=0.97), Yb (r2=0.94), and Si (r2=0.88). All curves were validated using a second set of independent fecal samples. A full set of total collection fecal samples for six sheep were also analyzed by pXRF for Co and Cr (digesta kinetics), and Si (digestion) marker concentrations. These fecal Co and Cr concentrations were used to estimate digesta mean retention times (MRT) and compared to estimated digesta MRT from the same sheep using Co and Cr marker concentrations determined by ICP analysis. No differences in estimated MRT were found when using either analytical method. Silica concentrations from the same fecal samples as determined by pXRF were used to determine the rate of DMD for each animal. When compared to apparent DMD for the same animals as determined using feed DM intake and fecal DM output collected during the total collection, no differences were again found using either analytical method. The results indicate that pXRF can be used as an alternative to standard ICP procedure, obviating the need for acid digestion, reducing cost and time; and may also offer an alternative analytical method for determining livestock DM digestibility.

Portable X-ray fluorescence spectroscopy as a rapid screening technique for analysis of TiO2 and ZnO in sunscreens

This investigation reports a rapid and simple screening technique for the quantification of titanium and zinc in commercial sunscreens using portable X-ray fluorescence spectroscopy (pXRF). A highly evolved technique, inductively coupled plasma-mass spectroscopy (ICP-MS) was chosen as a comparative technique to pXRF, and a good correlation (r2>0.995) with acceptable variations (≤25%) in results between both techniques was observed. Analytical figures of merit such as detection limit, quantitation limit, and linear range of the method are reported for the pXRF technique. This method has a good linearity (r2>0.995) for the analysis of titanium (Ti) in the range of 0.4–14.23wt%, and zinc (Zn) in the range of 1.0–23.90wt%. However, most commercial sunscreens contain organic ingredients, and these ingredients are known to cause matrix effects. The development of appropriate matrix matched working standards to obtain the calibration curve was found to be a major challenge for the pXRF measurements. In this study, we have overcome the matrix effect by using metal-free commercial sunscreens as a dispersing media for the preparation of working standards. An easy extension of this unique methodology for preparing working standards in different matrices was also reported. This method is simple, rapid, and cost-effective and, in comparison to conventional techniques (e.g., ICP-MS), did not generate toxic wastes during sample analysis.

Archaeometrical studies on some bronze buckles with portable (Handheld) XRF spectroscopy

Portable handheld X-Ray Fluorescence Spectroscopy (pXRF) is very effective and widely used technique for chemical analysis in field of archaeometry. The most advantageous feature of this technique is the possibility of analysing objects, artefacts on the spot without any sample-taking. In this study raw materials of 31 buckles from 7th century AD made of various kinds of bronze and silver alloys were analyzed to check similarities or differences between these objects via chemical analysis. Concentration ratios and distributions of alloying (Cu, Sn, Pb, Ag) and minor elements (Sb, Bi, Zn, Au) in material of bronze artifacts may have useful information suggesting important data about provenance and technology. Our recent study 27 bronze and 4 silver buckles were analyzed by pXRF and the results were used in statistical evaluation in order to get closer to provenance of raw materials and alloying technologies.

Proximal sensing of Cu in soil and lettuce using portable X-ray fluorescence spectrometry

This article demonstrates the use of proximal sensing for rapid assessment of Cu concentrations in agricultural soil and lettuce (Lactuca sativa L.) using portable X-ray fluorescence (P-XRF) spectrometry. We show that the approach is adequate for the screening of Cu contamination in agricultural soil. Biomass assays were conducted with Cu contaminated agricultural soil and lettuce (Lactuca sativa L.), and we collected samples from soil, roots and stems and leaves. The samples were measured with the P-XRF and the spectra were analysed to identify the Cu energy bands. The full width at half height (FWHH) and the maximum height of the Cu peak in the energy spectra were correlated with Cu concentrations that we determined using conventional analytical methods. Results show that P-XRF is a good technique for assessing soil contaminated with Cu. Results for roots and stems/leaves were not as accurate as those for soil. However, there is potential for this technique to be used as a first-pass measure to assess the Cu concentrations in plants because it is rapid and requires very little sample preparation. There is also scope to improve the approach using multivariate statistics. P-XRF sensing provides a useful alternative for the screening soil and plants that are contaminated with Cu, and potentially also other heavy metals. It is faster, cheaper, non-destructive and practical compared to conventional laboratory methods that rely on wet chemistry.

Coade, Blashfield or Doulton? The in situ identification of ceramic garden statuary and ornament from three eighteenth and nineteenth century manufacturers

In the eighteenth century, the emergence of a neo-classical style in architecture created a growing demand for a range of classically-inspired products - not only for architectural decoration but also for ornamentation of the garden. Producing individual items in stone, however, was time-consuming and expensive, so cheaper clay-based alternatives were adopted, most notably from manufacturers such as Coade (1769-1830), Blashfield (1840s-1875) and Doulton (1854-1890s). The artefacts of these manufacturers are now considered of high historic value and significance and their identification is important, not only for the historical record, but also for provision of the evidence necessary to carry out informed conservation. As the sale and copy of moulds was common practice during the eighteenth and nineteenth centuries, stylistic considerations do not provide reliable identification. Through the analysis of 24 historic objects of garden statuary and ornamentation, this research evaluates the use of portable X-ray fluorescence spectroscopy (pXRF), and more specifically element profiles, in identifying, and differentiating between the products of Coade, Blashfield and Doulton. Key questions around heterogeneity and representative material analysis are addressed. Despite the inherent heterogeneity of these materials, it is shown that discrimination is nevertheless possible using pXRF, primarily due to the significant differences observed across a range of elements at both macro- and trace-level. Objects of known provenance from Coade, Blashfield and Doulton produced three distinct and statistically significant groups demonstrating that the data reflect the composition of the bulk material – rather than surface characteristics. Through identifying the main discriminators for the Coade, Blashfield and Doulton materials, a simple presumptive test is proposed that can be used in an initial evaluation of any unsigned works. Analysis of a selection of unsigned objects with a probable Coade, Blashfield or Doulton provenance was in many cases successful in confirming the documentary evidence. A few objects, however, presented anomalous element profiles. These most likely result from past conservation treatments or polychromy - the two major limitations of the technique.

Study of mosaic glass tesserae from Delos, Greece using a combination of portable μ-Raman and X-ray fluorescence spectrometry

The present work discusses the results of an archaeometrical investigation on glass tesserae present in the mosaics from Delos (Greece) that was conducted in situ using two complementary non-invasive techniques, namely μ-Raman and portable X-ray Fluorescence spectrometry. The main objective of this work was to provide a compositional and technical characterisation of the glass tesserae. Since they are generally coloured and opaque or translucent, the study mainly focused on the identification of the employed colouring and opacifying agents.The three hundred and fifty four mosaics from the Cycladic island of Delos (130 to 88 BCE) form one of the most relevant mosaic corpus of the Hellenistic period. These numerous mosaics are often of high quality and stand out by the large use of artificial materials, in particular glass and faience, which is remarkable for the period.During three in situ analytical campaigns, around 270 glass tesserae were analysed by pXRF and nearly 40 tesserae using portable μ-Raman spectroscopy. This integrated approach allowed to gain an overview of the raw materials and the techniques employed in the production of these glasses. In particular, for all the tesserae the use of natron as a flux could be hypothesised. The majority of red glass tesserae were identified as a high-copper high-lead glass generally referred to as sealing-wax. The colourings agents used in the other tesserae (Fe, Co and Cu ions, Pb2Sb2O7) are the common ones used in Antiquity and the antimony-based opacifiers are typical for the considered period and geographic area. Blue and turquoise tesserae remarkably show a highly variable lead concentration which appears correlated with antimony. This correlation raised the hypothesis that an antimony ore rich in lead was used for the opacification of these glasses.

Determination of Fe in blood using portable X-ray fluorescence spectrometry: an alternative for sports medicine

An alternate methodology based on a portable X-ray fluorescence spectrometry (PXRFS) for determination of Fe in blood was evaluated. The iron concentrations was determined in whole blood of 18 male amateur athletes (runners) using this portable XRF spectrometer and compared with a control group (54 male donors at the same age but not involved with physical activities) obtained by XRF and NAA techniques. The Fe concentration in the blood of runners is an important factor in sports medicine contributing to the performance of endurance athletes as well as for proposing new protocols of clinical evaluation.

Empirical study of the effect of count time on the precision and accuracy of pXRF data

As a cost-effective and non-destructive method for multi-element analysis, portable X-ray fluorescence spectrometry (pXRF) has the potential for broad archeological application; however, recent applications of pXRF remain inconsistent. For example, sourcing studies using pXRF have irradiated artifacts and geologic source materials for widely varying amounts of time. In this study, we investigate the effect of count time on the precision and accuracy of pXRF data obtained for two geologic standards, as well as for obsidian, fine-grained volcanic (e.g., andesites, dacites), metamorphic, and chert specimens from the North American Great Basin. We find that the precision and reliability of pXRF data does not improve significantly at count times greater than 180s. Our analysis also indicates that count time has little bearing on the accuracy or validity of pXRF data, as expected from the mathematical relationships between count time, intensity, and concentration. Finally, we demonstrate that a well-calibrated pXRF instrument generates compositional data comparable to data obtained using other analytical methods. We offer this study as a step toward the development of a consistent and rigorous analytical protocol for archeological applications of pXRF.

Elemental quantification, chemistry, and source apportionment in golf course facilities in a semi-arid urban landscape using a portable X-ray fluorescence spectrometer

Abstract. This study extends the application of the portable X-ray fluorescence (PXRF) spectrometry to the examination of elements in semi-arid urban landscapes of the Southern High Plains (SHP) of the United States, focusing on golf courses. The complex environmental challenges of this region and the unique management practices at golf course facilities could lead to differences in concentration and in the chemistry of elements between managed (irrigated) and non-managed (non-irrigated) portions of these facilities. Soil samples were collected at depths of 0–10, 10–20, and 20–30 cm from managed and non-managed areas of seven different facilities in the city of Lubbock, Texas, and analyzed for a suite of soil properties. Total elemental quantification was conducted using a PXRF spectrometer. Findings mostly indicated no significant differences in the concentration of examined elements between the managed and non-managed areas of the facilities. However, strong positive relationships (R = 0.82−0.91, p &lt; 0.001) were observed among elements (e.g., Fe on the one hand and Cr, Mn, Ni, and As on the other; Cu and Zn; As and Cr) and between these elements and soil constituents or properties such as clay, calcium carbonate, organic matter, and pH. The strengths of these relationships were mostly higher in the non-managed areas, suggesting a possible alteration in the chemistry of these elements by anthropogenic influences in the managed areas. Principal component and correlation analyses within the managed areas suggested that As, Cr, Fe, Mn, and Ni could be of lithogenic origin, while Cu, Pb, and Zn could have anthropogenic influences. Only one possible, likely lithogenic, source of the elements was identified within the non-managed areas. As evidenced by the study, the PXRF spectrometer can be a valuable tool for elemental quantification and rapid investigation of elemental interaction and source apportionment in semi-arid climates.

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