Use Of pXRF Research Articles

Best Practices for Publishing pXRF Analyses

ABSTRACTWith its promise of nondestructive processing, rapid low-cost sampling, and portability to any field site or museum in the world, portable X-ray fluorescence (pXRF) spectrometry is rapidly becoming a standard piece of equipment for archaeologists. Even though the use of pXRF is becoming standard, the publication of pXRF analytical methods and the resulting data remains widely variable. Despite validation studies that demonstrate the importance of sample preparation, data collection settings, and data processing, there remains no standard for how to report pXRF results. In this article, we address the need for best practices in publishing pXRF analyses. We outline information that should be published alongside interpretive results in any archaeological application of pXRF. By publishing this basic information, archaeologists will increase the transparency and replicability of their analyses on an inter-analyst/inter-analyzer basis and provide clarity for journal editors and peer reviewers on publications and grant proposals for studies that use pXRF. The use of these best practices will result in better science in the burgeoning use of pXRF in archaeology.

Efficiency of Portable X-ray Fluorescence for Distinguishing Lead Slag.

In the Minier Valley (France, Aveyron), an archaeological site excavation has led to the discovery of 25 kg of lead (Pb) slag, found in a secondary position. On a macroscopic level, these slags can be classified into two distinct categories, vitreous black and porous gray. This clear visual differentiation has been previously documented at other Pb-silver (Ag) metallurgy sites dating from the 12th century to the 14th century in Europe, and more particularly in the workshops of Mont Lozère, located approximately 80 km away from Le Minier. However, to date, scant evidence exists regarding the specific metallurgical process that produced this slag. This study presents the results of the analysis of 218 Pb slags (Supplemental Material) using portable X-ray fluorescence (pXRF). This method does not appear to be ideally suited for investigating this type of artifact, as it does not provide quantification of oxygen content. Nevertheless, it can be used to quickly identify trends and determine whether the two identified facies exhibit dissimilar chemical compositions. The results indicate that, based on the elemental compositions of the slags, no discernible distinction can be made to categorize them into two separate groups, both in bivariate and multivariate analyses. Consequently, it can be inferred that the gray and black slags originate from a single process executed within the same type of furnace. Scanning electron microscopy energy dispersive spectrometry analyses on selected samples demonstrate that variations in metal content are considerably exaggerated by pXRF, but that the trends observed are confirmed. The use of pXRF is therefore a relevant tool for determining whether or not Pb-Ag slag is the result of the same process. However, this initial approach needs to be refined by other analyses to confirm whether the smelted ores are of local origin and to be able to better define the details of the metallurgical process used.

Paleosol marked by contrasting formation processes: A pilot study using digital morphometrics in Southeastern Brazil

Although soil formation results from the interactions of five classical factors and various pedogenic processes, such interactions can drastically change over time, which may be recorded in the so-called Paleosols. These soils may be formed under contrasting environmental conditions. Given such soils are rare in Brazil, this pilot study aimed to detail the morphological, physical, chemical (including elemental content and magnetic susceptibility (MS)), and mineralogical properties of a Paleosol with contrasting paleo- and current-drainage conditions, derived from sandstone having pellitic (fine) sediments intermixed, with support via digital morphometrics. Samples were collected in a regular grid of 15x15 cm along the soil profile down to 1.8 m depth. The soil samples were analyzed via portable X-ray fluorescence (pXRF) spectrometry and for assessment of magnetic susceptibility (MS), texture, fertility, and organic matter content. The mineralogy of the clay, silt, and sand fractions were determined via X-ray diffraction analyses. The pXRF and MS results were spatialized to the Paleosol profile. The first 108 cm of the soil profile are well-drained having reddish colors, contrasting with the underlying poorly-drained unity having greyish colors. The MS values were higher in the first 108 cm of the soil profile, reaching the lowest values in the 2Cg horizon at 142–180 cm depth. Quartz was the main mineral in sand and silt fractions, while kaolinite largely dominates the clay fraction in association with hematite. In the 2Cg horizon, the absence of hematite is related with the paleoredoximorphic conditions there. The Ti/Zr ratio indicated differences in parent materials of the reddish and greyish units of the Paleosol. The midslope position of the Paleosol makes colluvial deposition unlikely. The combined use of pXRF, MS, morphological, physical, chemical, and mineralogical analyses provided valuable details on the variation of the contrasting formation processes of the Paleosol studied.

Proximal sensor data fusion for tropical soil property prediction: Soil fertility properties

Proximal sensors have proven capable of predicting multiple soil properties under different conditions. However, doubts remain about which sensor is preferable for delivering optimal prediction models and which preprocessing methods produce the most accurate results. Portable X-ray fluorescence (pXRF) spectrometry and visible near-infrared (Vis-NIR) diffuse reflectance spectroscopy have been widely used, while the NixProTM color sensor has been explored more recently. This study evaluated the use of pXRF, Vis-NIR, and NixProTM data to predict soil organic matter content (SOM), pH, base saturation (BS), the sum of bases (SB), cation exchange capacity (CEC) at pH = 7 and effective CEC (eCEC), via each sensor in isolation, and via combined sensors data. Moreover, factors interfering in the prediction models' accuracy (data preprocessing methods, soil horizon, soil class, parent material) were used as auxiliary variables. 604 soil samples were collected in Brazil, encompassing ten soil orders and 19 parent materials. Numerical and categorical prediction models (7,980) were created for six soil properties using a random forest algorithm, totaling 7980 models, delivering almost 24,000 results., Coefficient of determination (R2), root mean square error (RMSE), mean absolute error (MAE), and residual prediction deviation (RPD) were used for validation of numerical predictions., Overall accuracy and kappa coefficient were calcualted for categorical predictions. Although the combination of sensors provided most of the best predictions, pXRF in isolation achieved accuracies close to the three sensors combined. NixProTM offered superior contributions to SOM and CEC predictions, but pXRF and Vis-NIR were responsible for the best results of most studied variables. On average, by adding pXRF to Vis-NIR data, predictive accuracy improved 32%; while adding Vis-NIR to pXRF data increased accuracy by ca. 6%. Soil-order-specific models improved predictions for Ultisols compared to general models (without soil order distinction), reaching R2 > 0.90. Soil parent material and horizon did not improve models significantly. Categorical predictions improved the accuracy for some properties, reaching an overall accuracy of 100% and kappa index of 1.0 for pH in A horizons of Ultisols via pXRF + Vis-NIR data. Proximal sensor data with no auxiliary variables provided almost all the best results. The fusion of proximal sensors can provide better predictions, but pXRF alone can deliver satisfactory results in most cases for the six soil properties.

The measurement of trace elements in human nails and nail clippings using portable X‐ray fluorescence: A review

A variety of biomarkers are available for the assessment of human exposure to, and absorption of, trace elements. The measurement of trace elements in nail or nail clippings offers some benefits relative to other body sites. Typically, concentrations of elements are assessed in clippings, using high precision methods such as inductively coupled plasma mass spectrometry or instrumental neutron activation analysis. Over the last decade, portable X‐ray fluorescence (pXRF) has emerged as a novel method with potential advantages for the measurement of trace elements in nail and nail clippings. This review paper examines early developments and recent work in the use of pXRF to measure elements such as As, Se, Mn, Zn, Cr, Pb, and Hg in nails and nail clippings. While initial pXRF studies were limited to the use of nail phantoms and nail clipping phantoms, more recent work has applied the pXRF method with real nail clippings and nails. Results have been promising, but a number of issues have emerged requiring additional attention. These relate to the analysis of X‐ray spectra, selection of X‐ray beam for excitation, method validation and normalization, and practical aspects of study design. With consideration of these issues, pXRF offers significant potential to provide a straightforward, economical, and rapid measurement approach to help improve our understanding of trace element exposure and related health outcomes.

Identifying anthropogenic features at Seoke (Botswana) using pXRF: Expanding the record of southern African Stone Walled Sites.

Numerous and extensive ‘Stone Walled Sites’ have been identified in southern African Iron Age landscapes. Appearing from around 1200 CE, and showing considerable variability in size and form, these settlements are named after the dry-stone wall structures that characterize them. Stone Walled Sites were occupied by various Bantu-speaking agropastoral communities. In this paper we test the use of pXRF (portable X-ray fluorescence analysis) to generate a ‘supplementary’ archaeological record where evident stratigraphy is lacking, survey conditions may be uneven, and excavations limited, due to the overall site size. We propose herein the application of portable X-ray fluorescence analysis (pXRF) coupled with multivariate exploratory analysis and geostatistical modelling at Seoke, a southern African SWS of historical age (18th century CE). The aim of the paper is twofold: to explore the potential of the application of a low cost, quick, and minimally invasive technique to detect chemical markers in anthropogenic sediments from a Stone Walled Site, and to propose a way to analyse the results in order to improve our understanding of the use of space at non-generalized scales in such sites.

Assessment of magmatic fertility using pXRF on altered rocks from the Ordovician Macquarie Arc, New South Wales

This research presents a new method for assessing magmatic fertility using the portable X-ray fluorescence spectrometer (pXRF) in altered rocks from porphyry terranes. A study of Northparkes and global Cu--Au porphyries highlighted low Zr and Y trends associated with mineralising intrusions. Zircon saturation occurs at low Zr concentrations owing to low-temperature crystallisation depressed by high dissolved H2O in the melt. Yttrium depletion indicates hydrous magmatic conditions that cause hornblende to crystallise early. Previously geochemical differentiation of hydrous, potentially ore-forming (fertile) porphyries has relied on ratios of Sr/Y and Sr/MnO from geochemical and/or pXRF analysis of least altered rocks. Strontium is highly mobile and limits its use in altered terranes. Finding samples in porphyry terranes where Sr can be demonstrated to be retained is difficult given the ubiquity of alteration associated with porphyry emplacement. This precludes the widespread use of pXRF, as quantitative assessment of alteration is beyond the capabilities of pXRF technology. Using immobile elements overcomes issues with alteration and provides more reliable indicators of magmatic fertility. Using a systematic pXRF workflow, plots of Zr vs Y and Zr*Y vs Al2O3/TiO2 were successful in identifying 100% of the mineralising intrusions in the Northparkes intrusive complex and provide an indication of magmatic fertility and a proxy for melt hydration state. The ratios of Zr/Nb vs Y/Nb are insensitive to alteration including weathering and are indicative of evolution and dissolved H2O content of magmatic sources. Moving from bivariate plots to ratio plots shifts the data into a real-number space and provides a linear function to assess against magmatic fertility. Application of the fertility indicators to a regional dataset from New South Wales highlights areas of known porphyry mineralisation indicating that the method has the potential to be a useful indicator of fertility beyond the scope of the pilot study. KEY POINTS The fertility of porphyry intrusions is directly related to their dissolved H2O content and oxidation state. High dissolved H2O content in magmas causes early crystallisation of hornblende, and temperature depression. As a result Zr saturation occurs at low Zr concentrations that results in depletion of Y and the MREE in hydrous rocks compared with normal arc rocks. Magmatic fertility can be rapidly and cheaply assessed in the field using Zr and Y concentrations from pXRF analyses. The use of immobile elements facilitates magmatic fertility assessment in altered rock, which was previously impossible owing to the use of mobile elements Sr and MnO.

The use of pXRF for light element geochemical analysis: a review of hardware design limitations and an empirical investigation of air, vacuum, helium flush and detector window technologies

Light element data are required for robust and accurate lithogeochemical interpretations and are important components in the study of hydrothermal alteration and mineralization processes. In this contribution we review the latest available portable energy dispersive X-Ray Fluorescence (pXRF) technologies exclusively in the context of light element analysis, with focus on the acquisition of data for Na, Mg, Al and Si. We discuss pXRF hardware design limitations, quantify variables that attenuate X-ray energies through numerical modelling, including common pXRF configurations, and empirically investigate modern pXRF technologies used to mitigate X-ray attenuation and improve light element analysis. The void between the sample and detector is a key issue regarding the success of pXRF light element analysis. Dry-air (normal conditions), vacuum purge and helium flush systems are evaluated. Modelled data that use a nominal sample-detector void of 10 mm show that using helium in lieu of air improves X-ray transmission effectiveness from ≈2% to ≈99% for Na and ≈10% to ≈100% for Mg. Modelled detector window data show that using a graphene detector window in lieu of a traditional beryllium detector window improves X-ray transmission effectiveness for Na from ≈38% to ≈64% and ≈57% to ≈77% for Mg. Progressive X-ray transmission effectiveness equates to ≈63% Na and ≈76% Mg when using a helium-graphene pXRF configuration v. ≈1% for Na and ≈6% Mg when using a traditional in-air beryllium pXRF arrangement (i.e. without sample or X-ray entrance window media). Empirically determined improvements of the resolved signal are more modest than those of modelled X-ray transmission effectiveness data. Instrument noise, spectral overlaps and random counting errors are unavoidable and inherent with the limitations of modern detector technologies. However, the employment of helium with graphene detector window technology allows very precise data to be obtained at significantly shorter scan times (i.e. 20 s, instead of the traditional 60–180 s, i.e. 3–9 times faster): a scan time of 20 s can achieve a precision of ≈18% @ ≈0.4% Na and ≈8% @ ≈0.3% Mg for elemental interference-free samples. Precision will improve with increasing analyte concentration.

Assessing soil contamination in automobile scrap yards by portable X-ray fluorescence spectrometry and magnetic susceptibility.

A by-product of industrialization and population growth, automobile scrap yards are a potential source of metal contamination in soil. This study evaluated the use of portable X-ray fluorescence (pXRF) spectrometry and magnetic susceptibility (χ) analysis in assessing metal soil contamination in scrap yards located in Brazil. Five automobile scrap yards were selected in Curitiba, Paraná State (CB1, CB2, and CB3) and Lavras, Minas Gerais State (LV1 and LV2). By evaluating metal concentrations and geoaccumulation index values, we verified moderate Cu, Pb, and Zr contamination and moderate to high Zn contamination, primarily in the topsoil (0-10cm). Soil Zn concentrations in automobile scrap yards were on average four times higher than in reference soils, suggesting that galvanized automobile parts may be the primary source of this soil contaminant. Although other elements (i.e., As, Cr, Fe, Nb, Ni, and Y) were slightly increased compared to reference values in one or more soils, concentrations did not constitute contamination. Automobile scrap yard topsoil had higher χ values (5.8 to 52.9 × 10-7m3kg-1) at low frequency (χlf) compared to reference soil (3.6 to 7.5 × 10-7m3kg-1). The highest values of χlf occurred in LV soils, which also represented the highest Zn contamination. Magnetic multidomain characteristics (percent frequency-dependent susceptibility between 2 and 10) indicated magnetic particle contributions of anthropogenic origin. The use of pXRF and χlf as non-destructive techniques displays potential for identifying soil contamination in automobile scrap yards.

Interdisciplinary examinations carried out on heterogeneous coarse ceramics from Neolithic lakeside settlements in the Northern Alpine Foreland (3900–3500 BCE): Analysis strategy and preliminary results from a test series using pXRF

In recent decades numerous Neolithic lakeside and wetland settlements have been investigated in Switzerland, southern Germany and eastern France. The finds from these settlements indicate that complex relationships and close contacts existed between the inhabitants of different settlements and regions. This can be seen in ceramic vessels that exhibit similarities to those from other regions based on their style, manufacturing technique and raw materials. Although the use of chemical and archaeometric analyses to determine the origin of pottery has been well established for years and despite promising investigations, such analyses have hardly ever been carried out in the study region; as a result, the topic of mobility has rarely been examined. In order to better understand mobility patterns in Neolithic societies by combining stylistic analyses with a chemical characterisation of the potter's clay used, this paper explores the use of portable energy dispersive X-ray fluorescence (pXRF) analysis as a means of chemically characterising ceramics. Since studies on the use of pXRF to examine handmade, heterogeneous and coarsely tempered ceramics are rare, it seems necessary to evaluate the method. This paper presents the development of a strategy for the analysis of large series of handmade coarse ceramics from prehistoric settlements. Two examples illustrate the possibilities of and limitations to pXRF analysis on pottery for the detection of mobility patterns of Neolithic societies in the Northern Alpine Foreland.

Organic Matter Removal on Oxide Determination in Oxisols Via Portable X-ray Fluorescence

ABSTRACTMany factors can influence the results obtained by portable X-ray fluorescence analysis (pXRF). The effect of soil organic matter on pXRF results is not satisfactory understood. Thus, we conducted this study to verify the effect of organic matter removal on oxide determination by pXRF in Oxisols. To obtain soil material with different organic matter contents and maintaining the same elemental composition from soil minerals, six contrasting Oxisols were heated in a muffle furnace for 30 min at the following temperatures (°C): 100; 200; 300; 400; 500 and 600. After heating, the soil samples were scanned using a pXRF Bruker® S1 Titan LE model (Dual Soil mode) for 60 s and the contents of SiO2, Al2O3, Fe2O3, TiO2, P2O5, and MnO were recorded. The soil organic matter presence underestimated the pXRF results for lightest oxides (Si and Al) compared to heaviest oxides (Fe, Ti, and Mn). These oxides are important for tropical soils classification and for many soil-related studies and pXRF technology has been a useful tool for soil chemical characterization. Our findings contribute to more suitable use of pXRF highlighting the possible effect of organic matter.

Portable X-Ray Fluorescence Spectroscopy for Rapid and Cost-Effective Determination of Elemental Composition of Ground Forage.

The recent development of portable X-ray fluorescence spectrometers (PXRF) has created new avenues for rapid plant elemental concentration determination at reduced cost while avoiding hazardous chemicals. A few studies have indicated the potential use of PXRF for homogenous plant tissue analysis. However, there is a lack of information for analysis of heterogeneous plant samples like livestock forage, which consists of a mixture of several species and plant parts, each varying in elemental concentration. Our objective was to evaluate PXRF for forage analysis, specifically the effect of forage particle size and scan time on important elements including P, K, Ca, and Fe determination. Hay samples (n = 42) were oven dried (60°C for 3 days) and ground into three particle sizes (≤0.5 mm, 0.25–0.5 mm and 1–2 mm). Prepared samples were scanned by PXRF using a vacuum (<10 torr) without a filter. Samples were placed in cups over thin prolene X-ray film and scanned for 180 s. A subset (n = 29) were also scanned for 60 and 120 s. PXRF counts for P, K, Ca, and Fe were compared with laboratory Inductively Coupled Plasma Optical Emission Spectroscopy (ICP) determinations, using regression models. Results indicated that these elements could potentially be determined with PXRF (r2 ≥ 0.70) in heterogeneous forage samples. Relationship strength increased with decreasing particle size, however, the relationship was still strong (r2 ≥ 0.57) at the largest particle size. Scanning time did not affect the relationship with ICP concentration for any of the particle sizes evaluated. This work demonstrated that with the right sample preparation PXRF can obtain results comparable to acid digestion and ICP regardless of sample composition, and suggests the potential for in situ determinations.

Sourcing qingbai porcelains from the Java Sea Shipwreck: Compositional analysis using portable XRF

This paper evaluates the use of portable x-ray fluorescence (pXRF) on glazes and pastes for sourcing Chinese porcelains from the 12th-13th century Java Sea Shipwreck (JSW) collection at the Field Museum. Three types of qingbai (bluish-white) wares from the JSW collection were chosen for pXRF analysis. Samples from four kiln complexes in China—Jingdezhen, Dehua, Huajiashan, and Minqing, hypothesized to be potential sources of the shipwreck’s qingbai ceramics based on visual inspection—were also analyzed to establish reference groups. Results from kiln samples show that different kiln complexes can be clearly differentiated by pXRF analysis of glazes. Based on pXRF analysis of ceramic samples from the JSW, there appear to be four compositional groups, and each group closely matches one of the four kiln reference groups. These findings support the use of pXRF on glazes, especially when pastes are difficult to access, as a method for identifying the potential sources for overseas cargos found distant from production contexts for Chinese porcelains.

Ceramic studies using portable XRF: From experimental tempered ceramics to imports and imitations at Tell Mozan, Syria

Studies of Northern Mesopotamian complex societies have long been predicated on ceramic wares, whereby ceramic variation is thought to reflect cultural variation. There is, however, an increasing appreciation for the role of imitation, itinerancy, and other phenomena in the distribution of ceramic styles. Much of this newfound nuance is due to chemical studies. Increasingly ceramics have been studied using portable X-ray fluorescence (pXRF). The utility of pXRF in ceramic research relies on being able to interpret the data in behaviorally meaningful ways. Thus, one approach to considering the efficacy of pXRF for ceramic studies proceeds from understanding the ways in which clays and tempers act as variables and influence the data in ways that reflect past behaviors. First, this study uses experimental replicas to exert systematic control over individual parameters (e.g., temper size, volume), allowing a better understanding of their influence. Second, this study considers Bronze Age wares at Tell Mozan in northeastern Syria. The experimental ceramics and Tell Mozan sherds are technological products that retain chemical evidence of choices made during their production. In the experimental ceramic set, a predicted phenomenon (e.g., the “dilution” effect from temper) occurred as expected, and elemental data differentiated clays and tempers selected for their manufacture. In the archaeological assemblage, elemental approaches established that distinctions between imports and locally made imitations are not always apparent by conventional means, and the use of pXRF is one way to overcome current shortcomings as well as contribute new insights.

The use of portable X-ray spectrometer in monitoring anthropogenic toxic metals pollution in soils and sediments of urban environment of Dar es Salaam Tanzania

The levels of toxic metals in sediments and soils along high traffic Sam Nujoma highway and in the densely populated Sinza area in Dar es Salaam Tanzania were determined using portable X-ray fluorescence spectrometer (pXRF) and atomic absorption spectrometer (AAS) in order to assess the levels of the metals in the sediments and soil and evaluate the use of pXRF in monitoring anthropogenic toxic metal pollution in the urban environment.Sediments from different areas in Sinza, especially those occurring near metal workshops, contained high toxic metal contents (e.g. Co, Zn, Pb and Ti) above the maximum permissible allowable limit by the Tanzania Bureau of Standards (TBS) for soils or sediments in an urban environment. This toxic metal content decreases sharply (~5m) away from workshops, and so reflecting pollution of the metals by workshop activities. Along Sam Nujoma highway, toxic metal contents of sediments and soils were lower than those of samples from Sinza, but also decreases as one moves from the road to the surroundings of the highway. Chromium and Zn contents in parts of Sam Nujoma highway were found, in places, to be above the maximum permissible allowable limit by the TBS for soils or sediments. As the geology of Dar es Salaam is mainly unconsolidated sands and clay and coral limestones, which are not likely natural source of the metals, then results of this study reflect anthropogenic addition of the metals to the Dar es Salaam environment.Similarity in concentration of Pb in sediments determined from previous study in the year 2009 along Sam Nujoma highway and those presented for this study suggests that Pb and most likely other metals as well, are not accumulating along or near the highway over time, but dispersed by water during wet season, when water table is high and most of roads and street are covered by surface runoff. Part of these contaminated surface runoff ends up in water, sediments and soils in downstream in the Msimbazi River, in which most of vegetables are grown and food sources like fish thrive, which highlights a potential risk of exposure of toxic metals in human food chain. Moreover, high levels of toxic metals in soils and sediments near workshops in Sinza pose high exposure risk to children and people leaving around the workshops.Successful application of pXRF in monitoring of anthropogenic toxic metals pollution in urban environment of Dar es Salaam open up possibility for similar applications in fast growing cities or artisanal miners’ sites that are frequently affected by anthropogenic pollution in the country and abroad.

Mineralogical and geochemical evidence of weathering in a middle to late Pleistocene paleosol sequence in the Driftless Area of Wisconsin

AbstractPaleosols occur in the Driftless Area of southwestern Wisconsin because this area escaped direct Pleistocene glaciation, allowing long-term loess and colluvium accumulation in selected settings. The most complete known depositional sequence at Oil City, Wisconsin, contains eight lithologic units with five paleosols, all with normal remanent magnetism (i.e., &lt;780 ka). Previous work characterized the stratigraphy, pedology, micromorphology, and clay mineralogy of the section. We investigate chemical weathering of the 8–63 µm silt fraction using X-ray diffraction (XRD) and elemental geochemistry by portable X-ray fluorescence (pXRF). Elemental ratios TiO2/CaO, Zr/Sr, and Rb/Sr generally align with the pedological evidence of weathering. Mineral ratios plagioclase/quartz and K-feldspar/quartz display greater scatter and less certainty in interpretation. The paleosols with Bt horizons have ratios indicating greater weathering than the modern soil. The most weathered paleosol is formed in the unnamed fourth loess unit stratigraphically below the Loveland Member. The stratigraphic position and higher degree of weathering support correlation of the fourth loess with the Yarmouth Geosol and Crowley’s Ridge Silt of the Middle Mississippi valley. Geochemical indices by pXRF are more consistent with established lithologic breaks than mineralogy by XRD. Our results support the use of pXRF for stratigraphic and weathering studies of Quaternary sediments.

Portable X-ray fluorescence (pXRF) applications in tropical Soil Science

ABSTRACT The X-ray fluorescence (XRF) is an analytical technique for determination of elemental composition of different materials. In soils, the XRF has many pedological, environmental and agronomic applications, mainly after the emergence of portable equipments (pXRF). This technique has been recently adopted and successfully used for soil characterization worldwide, but very rare works have been carried out in soils of developing countries. The soil characterization includes the complete elemental composition determination (nutrients, trace and rare-earth elements) and allows estimating some soil physical and chemical properties. In Brazil, this technique is still incipient, mainly the use of pXRF, however, it can greatly contribute to soil characterization in-field or in-lab conditions and also replacing methods of soil analyses considered non-environmentally friendly. This review summarizes the XRF technique including principles and the main applications of pXRF in soils highlighting its potential for tropical Soil Science.

Beyond the colonial curtain: Investigating indigenous use of obsidian in Spanish California through the pXRF analysis of artifacts from Mission Santa Clara

Obsidian artifacts recovered from Mission Santa Clara in central California (1780s–1840s) provide the opportunity to evaluate the persistence of regional economic connections and stone tool technologies in the California missions. Portable x-ray fluorescence (pXRF) analysis was conducted on a sample of 1020 obsidian artifacts, which could be linked to five major geological sources of obsidian found in different regions of California. Obsidian source profiles from features in different areas of the site indicate differential access to or preference for obsidian from particular sources. Despite the small size of many of the obsidian artifacts in the sample, this study found that the use of pXRF was suitable for assigning small artifacts (>0.3cm) to regional obsidian sources. The results illuminate the connections that native people living in mission contexts may have maintained to outside resources and provide the basis for further investigation into indigenous stone tool traditions in colonial contexts.

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.

The Non-Destructive Analysis of Some Ancient Jade Artifacts Unearthed from Henan Province by a Variety of Optical Techniques

A total of 14 pieces of ancient jade artifact unearthed from Henan Province were non-destructively analyzed by means of a portable X-ray fluorescence spectrometer (pXRF), laser Raman spectroscopy (portable and mobile) and optical coherence tomography (OCT) technology, comprehensively. The raw materials of ancient jade artifacts could be determined accurately through the combination of pXRF and portable Raman spectrometer in a short time. With the advantages of small size and easy-operation, these two instruments are suitable to in situ non-destructive analysis of ancient jade artifacts. The results of the pXRF shows that these ancient jade artifacts can be divided into 6 categories such as rich in Si Al K, rich in Ca, rich in Si Ca, rich in Si Mg, rich in Si, rich in Ca P. Their main phases have been successfully identified by the portable Raman spectrometer. In the lab, the mobile confocal laser Raman spectrometer, which help us find the Raman vibration peak of [OH] in the tremolite jade, is used to make up the disadvantages of the portable Raman spectrometer such as lower spectral resolution, lower accuracy and narrower measuring range. We can use the OCT to analyze the transparency, fiber fineness and inclusion etc. of the jade artifacts. The confocal laser Raman spectroscopy combined with OCT is used to analyze 2 containing inclusion of tremolite jade samples. OCT image can visually display the distribution characteristics of the inclusion in these 2 samples. Confocal laser Raman spectroscopy can accurately locate the sample surface of inclusion, then we can observe the micro morphology and analyze its phase. The results show that the black inclusion is graphite. This work is very significant to study the geographical origin of jade. Through the study we find, the use of pXRF, laser Raman spectroscopy (portable and mobile) and OCT can be achieved on the identification and analysis of cultural relic's phase composition and texture feature and meet the basic requirements of field archaeological work analysis.