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)−269−Synthesiology - English edition Vol.3 No.4 (2011) No detailed or comprehensive investigation has yet been performed for the entire country of Japan. In this study, the distribution of 53 elements and their background concentrations including toxic trace elements (As, Be, Cd, Hg, Mo, Sb, etc.) in the land and sea of Japan were obtained through production of a geochemical map. We also investigated the geochemical behavior of elements and the origin of elements in the environment[2][3]. The geochemical map shows the nationwide distribution of elements and provides basic data to clarify the origin and the circulation mechanism of elements. It also offers basic data for the evaluation of the anthropogenic pollution in the environment, for the prevention of the spread of contamination, and for remediation planning.3 Flow of geochemical mappingFigure 2 depicts the scheme of the geochemical map. There are four steps that must be taken to produce the geochemical map: sample collection, sample treatment, chemical analysis to measure the concentrations of the elements, and map drawing using a geographic information system (GIS). First, the sampling position was determined by reference to existing geographical, geological, and soil maps in the laboratory. Then the samples were collected at selected points in the field. Samples were stream sediments, marine sediments, and soils collected from all over the country. After bringing the samples back to the laboratory, they were dried and sieved in the laboratory. If necessary, the magnetic minerals were separated or powdered. Then, the samples were decomposed with the mixed acids, and the concentrations of elements were measured using the ICP–AES, ICP–MS, and atomic absorption spectrometry. The geochemical map was drawn using GIS from the obtained elemental concentrations of respective samples.Photographs of sampling, the collected samples, the sample treatment, and the geochemical map for the stream sediments and the marine sediments are also portrayed in the figure. Regarding stream sediments, sampling was easy: one could go to the river and collect the samples. However, sample preparation required separation of the magnetic minerals after sieving and drying. For the collection of marine sediments, use of a ship was necessary. Samples were obtained by dropping the sampler to the sea floor. Collected samples were dried and powdered. Chemical analyses and map drawing were conducted similarly for all samples.4 Development of research of geochemical mappingThe geochemical map was made to explore the mineral deposits to find local high concentration anomalies of heavy metals on the surface. However, in developed countries, few undiscovered deposits exist. The geochemical map is now of great interest from another perspective, as an illustration of environmental problems, because the map shows where and how toxic elements are distributed. In this respect, the British group of Webb in Imperial College formed a nationwide geochemical map for the first time in the world[4]. They produced a nationwide geochemical map by collecting about 50,000 samples gathered throughout the United Kingdom (about 151,000 km2). It was designated as a Geochemical Atlas. At present, the geochemical map has been extended to encompass all European countries[5]. Please refer to references cited herein for more information about foreign and domestic geochemical maps[6]-[9].4.1 Research scenarios at the National Institute of Advanced Industrial Science and Technology (AIST)Figure 3 depicts the scenario for making and opening to Fig. 1 Factors of elemental distributions in the geochemical map and an example of its practical useThe sum of the natural background and pollution of industrial activities and the city environment yields an element distribution. A geochemical map is used as basic geochemical information related to a country and for the evaluation of environmental pollution.What do you know from the elemental distribution?Geochemical basic information on a country ・Chemical composition of the Japanese Islands Clarke number of the Japanese Islands ・Estimation of natural radiation dose Estimation of natural background when measuring neutrinosEvaluation of environmental pollution ・Evaluation of environmental pollution Pollution of soil and sea ・Evaluation of amount of radiation exposure Presumption of amount of natural radiation exposurePurpose and example of practical useSum of pollution from natural background,city environment, industrial activityGeochemical map - Elemental distributionHow to determine the elemental distributionNatural backgroundCity environmentIndustrial activity

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