| Titre | An evaluation of methodologies for calibrating Itrax X-ray fluorescence counts with ICP-MS concentration data for discrete sediment samples |
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| Auteur | Gregory, B R B; Patterson, R T; Reinhardt, E G; Galloway, J M ; Roe, H M |
| Source | Chemical Geology vol. 521, 2019 p. 12-27, https://doi.org/10.1016/j.chemgeo.2019.05.008  Accès ouvert |
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| Année | 2019 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20200178 |
| Éditeur | Elsevier Science Bv |
| Document | publication en série |
| Lang. | anglais |
| DOI | https://doi.org/10.1016/j.chemgeo.2019.05.008 |
| Media | papier; en ligne; numérique |
| Formats | pdf |
| Sujets | fluorescence aux rayons x; méthodes de fluorescence aux rayons x; analyse de carottes; sediments; sédimentologie; Sciences et technologie; Nature et environnement; géochimie |
| Illustrations | cartes de localisation; tableaux; graphiques; diagrammes de distribution des éléments |
| Diffusé | 2019 05 11 |
| Résumé | (disponible en anglais seulement)
Core-scanning X-ray Fluorescence (XRF-CS) is a well-established technique for rapid ( < 30 s/interval) analysis of sediment core geochemistry at sub-mm
resolution with substantially less analytical cost compared to methods that rely on physical sub-sampling. Due to issues inherent in analyzing wet sediment of heterogeneous particle size and composition with irregular surface topography using XRF,
XRF-CS results are generally considered semi-quantitative. The result of early efforts to calibrate XRF-CS data with conventional geochemical results (e.g. WD-or ED-XRF, ICP-AES, ICP-MS) showed weak correlations for less abundant or poorly detectable
elements, however, more recent methods have been proposed to improve accuracy. These methods include: 1) converting XRF-CS results to dry mass concentration; 2) normalizing XRF-CS data to conservative elements (Si, Ca), total counts/second, or X-ray
scatter (CIR); and 3) calibration of data using multivariate analysis of elemental logratios (MLC). These approaches are not yet widely employed, and require additional testing on a variety of sediment compositions. Recently developed equipment
enables analysis of discrete sediment samples, providing > 30 replicate analyses for up to 180 samples in a single XRF-CS run. These replicate measurements allow for rigorous testing of precision and accuracy of XRF-CS data. To determine the ideal
method of data transformation to improve XRF-CS calibration to quantitative geochemical concentration, 100 lake sediment-surface samples collected from Harvey Lake, New Brunswick, Canada, were analyzed using Itrax-XRF-CS, and then with ICP-MS
analysis after multi-acid digestion. Normalization using the CIR and correction for water content showed strong correlation coefficients (Kendall's tau) for elements with atomic number > 18 and high concentrations in the sediment. Results for lighter
elements and those with lower concentrations did not perform well using these calibration methods. The MLC provided the most accurate reproduction of observed ICP-MS trends and strong correlations (R) between predicted and actual geochemical
concentrations. Based on these results, CIR-normalized or wet-corrected calibrations are ideal for studies where absolute geochemical values are of lesser importance, and the MLC method is appropriate for studies with large numbers of sediment
samples (n > 100), or those where absolute concentrations of elements are of greater importance. |
| GEOSCAN ID | 326590 |
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