Vol.3 No.4 2011

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Research paper : Investigation of the distribution of elements of the whole of Japan and their applications (N. Imai)−275−Synthesiology - English edition Vol.3 No.4 (2011) Peninsula, in addition to anthropogenic influences from the large cities nearby.7 Disclosing data to the public (Providing information to society as a public good)A geochemical map homepage was made, presenting data of the geochemical map which had been accumulated. It was then made available to the public for easy access and reference on the web. Figure 6 shows the geochemical map homepage. The geochemical map of land and sea of the whole country is visible here, as are the regional geochemical maps and detailed information of each elemental concentration for all 3024 stream sediments and 4905 marine sediments. All of that information can be accessed easily on the network. Moreover, a photograph of the sampling point and the sample are displayed for all stream sediments. Photographs of the samples are available for some bottom sea sediments. Especially, a photograph of stream sediment can be enlarged by clicking, and the kind of rock and sediment distributed in the region can be investigated. In addition, the elemental concentration and the latitude and longitude of all the samples, the geochemical map of the whole country and regional map (the raster map / GIS shape file), and related information are downloadable from the website.8 Practical use of a geochemical map (Various uses of the basic information of the nation)The geochemical map presents the elemental distribution on the surface of the earth’s crust for land and sea areas. The data are important as basic information of the entire nation. In addition, because stream sediments were collected from throughout the country and because the individual stream sediments represent their local watersheds, the average concentration of all the samples can be considered as an average chemical composition of Japan. The average chemical composition of Japan (Clarke number of the Japanese archipelago)[21], as calculated from a distribution ratio and the composition of typical 166 rock samples distributed in Japan is desired. This is considered to be a theoretical value, although the mean value of 3024 stream sediments in the geochemical map is a value that was actually measured in the field. It was clarified in this study that both values agree very well.A geochemical map can also be used for evaluation of natural radiation doses, as determined by the sum of the natural radiations from surrounding rocks and sediments and the cosmic rays. The former is calculable roughly from the contents of potassium, uranium, and thorium in rocks and sediments obtained from the geochemical map. For instance, the natural radiation dose is known to be large in west Japan, where granite that contains much potassium, uranium, and thorium is widely distributed. The contamination levels of radioactivity from nuclear facilities in various regions can be evaluated through comparison with the natural background level.For social purposes, the geochemical map is used as basic data for the evaluation of soil pollution. The concentration of elements is readily apparent from the map in the Fig. 6 Homepage of geochemical mapThe homepage of the geochemical map (http://riodb02.ibase.aist.go.jp/geochemmap/index.htm) and detailed information of individual stream and marine sediments are shown. Photographs of sampling points and samples of stream sediment and marine sediment, the elemental concentration and the latitude and longitude of all the samples are shown.http://riodb02.ibase.aist.go.jp/geochemmap/index.htmHomepageStream sedimentMarine sediment

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