Analysing spatio-temporal patterns of archaeological soils and sediments by comparing pXRF and different ICP-OES extraction methods

In this paper we compare six different multi-element sediment analyses for archaeological purposes. Two different sets of samples from archaeological excavations in Germany and Turkey representing feature, mixed-debris and offsite samples are extracted with HNO3, HCl, Aqua Regia (AR), DTPA and NH4NO3, and measured using ICP-OES techniques. The results are compared to each other and the total elemental content obtained by a portable X-ray fluorescence spectrometer (pXRF). DTPA and NH4NO3 extraction were found not to be suitable for multi-element analysis in the archaeological context, as they displayed poor correlations with all other methods. NH4NO3 showed values not reflecting the known settlement activities. AR, HNO3, HCL and pXRF results do reflect the settlement history and are highly correlated. A separation into different sample categories (feature, mixed-debris and offsite) was achieved for all those methods by using multivariate statistics (PCA). pXRF is a cheap and quick procedure which can be easily performed at an excavation site and can thus eliminate cumbersome sample transport. We provide evidence that pXRF is highly suitable for multi-element analysis in the archaeological context.