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Research paper : Investigation of the distribution of elements of the whole of Japan and their applications (N. Imai)−272−Synthesiology - English edition Vol.3 No.4 (2011) such costs and staff should be estimated as necessary from a realistic viewpoint to compile such a nationwide geochemical map. At that time, the sample collection density of 1 km mesh was thought to be primarily important, and a coarser density was not meaningful. However, if the coarser mesh were adopted, then a possible plan could be formulated in terms of cost, the number of workers, and the period needed for the project. The period of the plan of the project was set as five years, and the number of samples was suppressed to about 3000 by setting the mesh to 10 km. Consequently, the nationwide geochemical map plan became a feasible one by adoption of the sample number and mesh. At the first step, the geochemical map was to cover the whole country first, even with coarse sampling density. Thereafter, as necessary, the density was expected to be raised separately for specific areas of interest. In this way, both demands of covering the whole country and scientific significance would eventually be fulfilled. The budget was obtained from the Environment Agency, and the project was begun in 1999. The first geochemical map of the whole country of Japan was therefore completed in 2004[2]. Several features of elemental distribution in the Japanese archipelago were clarified for the first time in spite of the coarse mesh of 10 km that was chosen. Results show that it is not necessary to worry about the overly coarse sample collection density to understand anything. Fortunately, the nationwide geochemical map of Japan has attracted much social and scientific interest because of its ease of visual comprehension. It has been used in various fields. The project team won the “Environmental Prize” in 2005[15].4.1.3 Geochemical map of the sea (Progress to the next stage)Several ideas of how to advance the research of geochemical map to the next step were then raised. Another possible project was the elemental distribution for land extending into the sea. Geochemical mapping of sea areas off the coast of Hokuriku to Akita had been done before. The GSJ has studied the sea around Japan for many years, and many previously collected sea bottom sediments have been analyzed. For the geochemical map of the sea of the whole country, we can use those prior collected samples accumulated by GSJ. In our project, the bottom sea sediments were newly collected in the sea where no samples had existed before (about 30 percent of the whole country). Consequently, all marine sediments in the sea of the whole country could be collected. The total old and new samples were 4905. The geochemical map of the land and sea of the whole country was completed using these samples in 2010[3]. The nationwide geochemical map of both land and sea was the first of its kind in the world. The elemental distributions between land and sea were thus connected, which enabled us to elucidate the movement of elements from land to sea. A soil geochemical map of the whole country is being made at present as development of further study by collecting about 3000 soil samples throughout the country.5 Factors of technology to produce a geochemical map (Development of technologies for objectives)Factors of technology that are useful for producing a geochemical map include sample collection, chemical analysis, and map drawing. To achieve the objectives, the actual techniques to produce geochemical map are described to notify users of differences from the conventional method. For a detailed description of the procedures, refer to the past reports of the literature[2][3]. The important considerations are the automation of handling vastly numerous samples and the standardization of processes for all samples using a single technique. Because the geochemical maps had been made using different techniques in various regions, it was difficult to compare them quickly. However, by adopting standardized techniques, data of the whole country can now be analyzed systematically in a unified manner.5.1 Sample collection5.1.1 Geochemical map of the northern Kanto region[11]In making the geochemical map of a large area, how we collect numerous samples is the most important consideration. The initial method used for collection of stream sediments in this study was how to reduce the sample processing time after sampling. Therefore, we tried to finish the necessary work such as sieving to the greatest degree possible in the field. Actually, one researcher and 2–3 assistants (students) constituted one team, which moved to the sampling position by car in checking 1/25,000 or 1/50,000 geographical maps. It was necessary to move to small rivers for sampling in cases of the geochemical map of 1 km mesh. If unable to reach it by car, it was necessary to walk to the sampling area. The sampling position was determined principally as the end of the branch of a river (the most downstream reaches of the watershed). The sampling point was determined beforehand in the laboratory, and how we could reach the area quickly was important.After arriving at the sites, the teams separated stream sediments finer than 80 mesh (about 0.17 mm) by sieving. Stream sediments were put on the sieve of 80 mesh, and the sand and mud of 80 mesh or less which passed through the sieve were separated using filter paper by pouring the river water. However, some samples took a very long time for filtration because the filter paper became clogged, or it took much time in searching the sands of minute grains because we were sometimes unable to find them where the flow of the river was fast. If the required amount of the sample was not taken, then the filtration was repeated, which took much more time. After that painstaking process, often only several samples were collected in a day. The samples were brought

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