Construction of a Forensic Soil Database of the Hokkaido Region in Japan by Synchrotron Radiation X-ray Analysis

The purpose of the present study is to construct a nation-wide forensic soil database, which allows for the identification of soil evidence based on heavy element and heavy mineral signatures determined by two synchrotron radiation (SR) X-ray techniques, i.e., a high-energy synchrotron radiation X-ray fluorescence analysis and a synchrotron-radiation X-ray powder diffraction analysis, respectively. The heavy element and heavy mineral compositions of the stream sediments collected at 3024 points located all over Japan were measured by the two SR X-ray techniques. The present paper focuses on a regional characterization of the sediments collected from the Hokkaido areas. The concentrations of heavy elements and heavy minerals in the Hokkaido areas were visualized as maps that enable us to compare the heavy element and heavy mineral compositions with the geological context of the samples. Based on a hierarchical cluster analysis using the semi-quantitative compositions of the heavy minerals, we could successfully classify the sediments into six groups corresponding to their background geologies. A Bonferroni multiple comparison demonstrated that these six groups also have significant differences in the heavy element composition. From these examinations, we could demonstrate that detailed regional identification of unknown samples is possible by analyzing both heavy element and heavy mineral compositions of each sample.