Quantitative analysis of heavy elements and semi‐quantitative evaluation of heavy mineral compositions of sediments in Japan for construction of a forensic soil database using synchrotron radiation X‐ray analyses

Abstract

We have started to construct a nationwide forensic soil sediment database for Japan, based on the heavy mineral and trace heavy element compositions of stream sediments collected at 3024 points across Japan. The data were measured by high‐resolution synchrotron radiation X‐ray powder diffraction (SR‐XRD) and high‐energy SR X‐ray fluorescence analysis (XRF) using the SR source of SPring‐8, the SR radiation facility in Japan. The automated sampling systems allow the measurement of 130 powder diffraction patterns and 100 XRF spectra per day using sediment samples of just a few milligrams, which enabled us to construct a database of a large number of samples. The concentrations of heavy elements such as rare earth elements, Cs and W up to 500 ppm level in soil sediments can be determined by the calibration curve method by using high‐energy SR‐XRF utilizing monochromatic X‐rays of 116 keV. A heavy element concentration map superimposed on a geographical map of Japan was successfully prepared from these analytical data. The heavy mineral compositions were quantitatively evaluated by using the peak intensity of characteristic XRD peaks of the component minerals measured by a Debye–Scherrer camera having a radius of 286.5 mm, recorded with an imaging plate and monochromatic X‐rays (λ = 1.0 Å). This study demonstrates that XRF and XRD data collected from the sediments of Shizuoka Prefecture closely reflect the geological and geographical signature of the sediment samples, which can be used for the provenance determination of soil evidence from a crime scene. Copyright © 2013 John Wiley & Sons, Ltd.