Inter-technique comparison of PIXE and XRF for lake sediments

Abstract

In this paper we describe a validation procedure for the chemical analysis of major elements and some minor elements such as Sr, Cr, Ni, Zn and Zr in heterogeneous geological sediments. The procedure applies two distinct techniques (PIXE and XRF) for the analysis of sediments. In this work an inter-technique comparison of heterogeneous lacustrine sediments from Amik Lake in the vicinity of the Roman city of Antioch (SE, Turkey) was carried out. Dried raw samples and samples with linking powder added were analyzed using PIXE performed at the “Arkeo” beamline of the University of Liège AVF cyclotron and XRF (University of Liège). The aim of this work was to compare PIXE and XRF analysis with set-ups routinely in use in the two laboratories. The purpose was also to determine the best combination of techniques and sample preparation protocols to be applied for heterogeneous sediments and the main elements of interest for each specific technique. The results are in agreement among the two techniques, with discrepancies concerning lighter and minor elements. These differences are mainly related to the texture of the sediments and the intrinsic features of the XRF and PIXE techniques. Major and selected minor elements are sensitive to the grain size and porosity of the samples. However, the accuracy of both XRF and PIXE requires the reduction of the grain size or addition of a linking powder to the sediments to fill the voids in order to increase the intensities of both lighter and minor elements. The results demonstrate the critical importance of sample treatment prior to analysis as well as the necessity of several measurement points and replicates to ensure the accuracy of PIXE results.