Abstract
AbstractX‐ray fluorescence (XRF) scanning of marine sediment has the potential to yield near‐continuous and high‐resolution records of elemental abundances, which are often interpreted as proxies for paleoceanographic processes over different time scales. However, many other variables also affect scanning XRF measurements and convolute the quantitative calibrations of element abundances and comparisons of data from different labs. Extensive interlab comparisons of XRF scanning results and calibrations are essential to resolve ambiguities and to understand the best way to interpret the data produced. For this study, we sent a set of seven marine sediment sections (1.5 m each) to be scanned by seven XRF facilities around the world to compare the outcomes amidst a myriad of factors influencing the results. Results of raw element counts per second (cps) were different between labs, but element ratios were more comparable. Four of the labs also scanned a set of homogenized sediment pellets with compositions determined by inductively coupled plasma‐optical emission spectrometry (ICP‐OES) and ICP‐mass spectrometry (MS) to convert the raw XRF element cps to concentrations in two ways: a linear calibration and a log‐ratio calibration. Although both calibration curves are well fit, the results show that the log‐ratio calibrated data are significantly more comparable between labs than the linearly calibrated data. Smaller‐scale (higher‐resolution) features are often not reproducible between the different scans and should be interpreted with caution. Along with guidance on practical calibrations, our study recommends best practices to increase the quality of information that can be derived from scanning XRF to benefit the field of paleoceanography.
Highlights
The invention of nondestructive X‐ray fluorescence (XRF) spectrometric scanning of split sediment cores revolutionized the field of paleoceanography (e.g., Croudace et al, 2006; Jansen et al, 1998; Rothwell & Croudace, 2015)
Four of the labs scanned a set of homogenized sediment pellets with compositions determined by inductively coupled plasma‐optical emission spectrometry (ICP‐OES) and ICP‐mass spectrometry (MS) to convert the raw XRF element cps to concentrations in two ways: a linear calibration and a log‐ratio calibration
We focus on one representative sediment section (Section U1425C‐2H3) and the elements Fe and Ca, which highlight some of the key complexities in comparing XRF scans from different labs
Summary
The invention of nondestructive X‐ray fluorescence (XRF) spectrometric scanning of split sediment cores revolutionized the field of paleoceanography (e.g., Croudace et al, 2006; Jansen et al, 1998; Rothwell & Croudace, 2015). High‐energy X‐rays irradiate elements in the sediment core, exciting electrons that release surplus energy in a characteristic spectral pattern. Detector systems measure this fluorescing energy spectrum and mathematical deconvolutions of the spectrum estimate the individual element intensities, which are estimates of each element's abundance in the sediment.
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