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

Abstract

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.

Disentangling Sedimentary Pathways for the Pleniglacial Lower Danube Loess Based on Geochemical Signatures

“…Due to its complex formation, loess represents a geological and lithological mixture of its source areas. The different mineralogical components of loess deposits are prone to a multitude of methodological issues and sensible to, e.g., instrumentation or pretreatment of samples (Goff et al, 2020). Differences between different geochemical analysis techniques, such as inductively coupled plasma mass spectrometry (ICP-MS) and x-ray fluorescence analyses (XRF) can account to up to 10% of the measured contents (Miyazaki et al, 2016).…”

pXRF method development for elemental analysis of archaeological soil

“…Removing moisture and amending the calibrations accounts for spectral interference in these situations (Goff et al . 2020; Ravansari et al . 2020).…”

“…2017; Luo and Bathurst 2017; Goff et al . 2020). These results showed that whilst homogenizing soil is required to increase the concentrations detected, there is no artificial impact on the relative distributions of all elements of interest.…”

“…There is a range of practices encapsulated within ex‐situ methods, such as milling, pressing and fusing powders (Lemière 2018; Goff et al . 2020). The ex‐situ method used in this research involves manual grinding without pelleting because this does not require access to additional instrumentation.…”

“…2016; Goff et al . 2020). This paper investigates the key influential factors for enhancing pXRF analysis of soil through a systematic, controlled and experimental approach to produce a protocol ready for application to archaeological case studies.…”