EVALUATING THE UTILITY OF FIELD-PORTABLE X-RAY FLUORESCENCE (PXRF) FOR THE RAPID MEASUREMENT OF LANDSCAPE CHANGE PROXIES

X-Ray fluorescence (XRF) spectrometry has long been used to measure elemental geochemistry in sediments, and recently, field-portable XRF units (pXRF) have produced elemental concentrations that are as accurate as traditional analytical methods for some elements in specific applications. In this study, we assessed pXRF data quality for use with aquatic sediments, including the precision of replicate pXRF measurements, repeatability among multiple pXRF analyzers, and accuracy of pXRF elemental concentrations as compared to certified reference materials (CRMs). Precision was assessed using relative standard deviation (RSD) of replicate measurements, repeatability was assessed using Pearson's product-moment correlation coefficient (r²) and Spearman's rank-order correlation (r_s) among multiple pXRF analyzers using identical samples, and accuracy was assessed using r² and r_s values between CRM certified values and pXRF measured values. The data quality of elemental pXRF measurements was not identical when assessed for precision, repeatability, and accuracy: for our suite of aquatic sediment samples and CRMs, pXRF measurements were both precise and repeatable for Fe, Ti, Mn, K, Rb, Zn, Zr, V, Pb, As, and S; and pXRF measurements were precise, repeatable, and accurate for Fe, Ti, K, Rb, Zn, As, and S. Portable XRF has many advantages, including portability, wide availability, low cost, non-destructive analysis, and short sample analysis time. Our data suggest that pXRF can provide a high level of data quality for elemental geochemistry when applied to aquatic sediments. Many of the elements that demonstrated a high level of data quality are frequently used as indicators of landscape change; use of pXRF in these studies may enable investigators to measure samples at a higher resolution or to include more cores in their analyses.