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

Ribeiro, Bruno Teixeira; Silva, Sérgio Henrique Godinho; Silva, Elen Alvarenga; Guilherme, Luiz Roberto Guimarães

doi:10.1590/1413-70542017413000117

Cited by 70 publications

(29 citation statements)

References 37 publications

(65 reference statements)

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“…Sediment elemental composition was determined by X-ray fluorescence (XRF), using a portable XRF spectrometer equipped with a 50 kV/100 μA X-ray tube. XRF technology has been increasingly used for quantifying soil geochemistry, given that it provides a non-destructive method with rapid results and no chemical waste generation (Ribeiro et al 2017;Silva et al 2017). The analysis allows for the quantification of the following 45 elements: Ag, Al 2 O 3 , As, Au, Ba, Bi, CaO, Cd, Ce, Cl, Co, Cr, Cu, Fe, Hf, Hg, K 2 O, La, MgO, Mn, Mo, Nb, Ni, P 2 O 5 , Pb, Pd, Pt, Rb, Rh, S, Sb, Se, SiO 2 , Sn, Sr, Ta, Th, Ti, Tl, U, V, W, Y, Zn, Zr.…”

Section: Laboratory Analysismentioning

confidence: 99%

Using pedological knowledge to improve sediment source apportionment in tropical environments

et al. 2018

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Purpose Soils are important regulators of Critical Zone processes that influence the development of geochemical signals used for sediment fingerprinting. In this study, pedological knowledge of tropical soils was incorporated into sediment source stratification and tracer selection in a large Brazilian catchment. Materials and methods In the Ingaí River basin (~1200 km 2), Brazil, three source end-members were defined according to the interpretation of soil and geological maps: the upper, mid, and lower catchment. A tributary sampling design was employed, and sediment geochemistry of three different size fractions was analyzed (2-0.2 mm; 0.2-0.062 mm, and < 0.062 mm). A commonly used statistical methodology to element selection was compared to a knowledge-based approach. The mass balance un-mixing models were solved by a Monte Carlo simulation. Modeled source contributions were evaluated against a set of artificial mixtures with known source proportions. Results and discussion For the coarse fraction (2-0.2 mm), both approaches to element selection yielded high errors compared to the artificial mixtures (23.8% and 17.8% for the statistical and the knowledge-based approach, respectively). The knowledgebased approach provided the lowest errors for the intermediate (0.2-0.062 mm) (10.9%) and fine (< 0.062 mm) (11.8%) fractions. Model predictions for catchment outlet target samples were highly uncertain for the coarse and intermediate fractions. This is likely the result of the spatial scale of the source stratification not being able to represent sediment dynamics for these fractions. Both approaches to element selection show that most of the fine sediments (median > 90%) reaching the catchment outlet were derived from Ustorthents in the lower catchment. Conclusions The different element selection methods and the artificial mixtures provide multiple lines of evidence for evaluating the fingerprint approaches. Our findings highlight the importance of considering pedogenetic processes in source stratification, and demonstrate that different sampling strategies might be necessary to model specific sediment fractions.

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Section: Laboratory Analysismentioning

confidence: 99%

Using pedological knowledge to improve sediment source apportionment in tropical environments

et al. 2018

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“…For soil investigations, some studies have obtained data by placing the instrument directly onto a field‐moist core or profile face (e.g., Ribeiro, Silva, Silva, & Guilherma, ; Stockmann et al., ; Silva et al., 2018). Samples returned to the laboratory are also sometimes scanned while they are field moist, although at this point most researchers dry, disaggregate, and/or sieve the samples before treatment or measurement.…”

Section: Introductionmentioning

confidence: 99%

Impact of sample preparation methods for characterizing the geochemistry of soils and sediments by portable X‐ray fluorescence

Goff

Schaetzl

Chakraborty

et al. 2020

Soil Science Soc of Amer J

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We examined the impact of three different sample preparation methods on bulk soil geochemistry data obtained from a hand‐held, portable X‐ray fluorescence (pXRF) spectrometer. We generated data from a soil core recovered from the surface, downward into unaltered loess, and into a buried soil at a site in eastern Iowa. Samples were scanned (i) directly from field‐moist soil cores; (ii) after drying, grinding, and being loosely massed in plastic cups; and (iii) as pressed‐powder pellets. Data derived using these methods were compared with data obtained from a standard benchtop X‐ray fluorescence (XRF) unit. Generally, the results indicated that data from pressed powder pellets often provide the best correlation to benchtop XRF data, although the results were sometimes element or compound specific. Calcium oxide, Fe2O3, and K2O generally provided the strongest correlations between pXRF‐ and XRF‐reported values; SiO2 data were more problematic. Field‐moist pXRF scans generally underestimated element concentrations, but the correlations between pXRF and benchtop XRF measurements were greatly improved after applying pXRF‐derived calibration standards. In summary, although element/compound data provided by pXRF showed significant relationships to benchtop XRF data, the results are improved with proper sample preparation (i.e., drying, grinding, pressing) and usually by calibrating the pXRF data against known standards.

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“…The pXRF analysis is fast, non-destructive, environmentally friendly, allowing the determination of several elements simultaneously (e.g., from Mg to U) in-situ or ex-situ within the order of seconds. The Soil Science has been greatly benefited from pXRF analysis (Ribeiro et al, 2017;Ribeiro et al, 2018;Santana et al, 2018;Silva et al, 2018;Mancini et al, 2019, Weindorf et al, 2014Stockmann et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Elemental concentration via portable x-ray fluorescence spectrometry: Assessing the impact of water content

et al. 2019

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Portable X-ray fluorescence (pXRF) analysis can be considered one of the main recent advances for chemical characterization of earth materials. The water content of the samples can affect the pXRF performance. As a novelty, we aimed to establish relationships (linear regression) between the effect of water content on pXRF results and atomic number (Z) of the elements. Three certified reference materials (CRM) were investigated: OREAS 100a, OREAS 101a, and OREAS 101b. These materials were saturated (0.68 g g-1) with distilled water and left to air-dry naturally. During the drying, the elemental concentrations (C) were determined at different water contents using a pXRF spectrometer. For each water content, the ratio Cwet/Cdry was determined and plotted against the water content. The attenuation coefficient (σ) was also determined. High σ values mean more influence of water content upon measurement element concentration. The obtained recovery rates allowed a qualitative determination. The concentration for the most elements reduced linearly with increasing water content. A predictable behavior of the water content on pXRF results as function of atomic number was not found. Elements identified by Lα spectral line with highest Z were more impacted by water content than elements identified by Kα line with lowest Z. Ti, Cr and Fe was not significantly influenced by water content, and Sr was the most impacted. Our findings contribute to decision-making before characterization earth materials via pXRF, obliging the use of dry samples for determination of impacted elements or by using moisture-corrected data.

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

Cited by 70 publications

References 37 publications

Using pedological knowledge to improve sediment source apportionment in tropical environments

Using pedological knowledge to improve sediment source apportionment in tropical environments

Impact of sample preparation methods for characterizing the geochemistry of soils and sediments by portable X‐ray fluorescence

Elemental concentration via portable x-ray fluorescence spectrometry: Assessing the impact of water content

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