Formation process of the natural derived arsenic contaminated Alluvial in the arsenic ground water problem.

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This research makes the purpose of natural derived arsenic behavior in the Alluvium to solve the arsenic ground water problem. The investigated area is mainly the Niigata Plain and the Hetau Plain, Inner Mongolia, China as well. The quantities of arsenic in deposits were measured by the method of the atomic absorption spectrometry, the X-ray fluorescence analysis(XRF), and the inductively coupled plasma spectrometry(ICP).In the research of first year, arsenic concentrations highly range from approximately 50 to 100ppm in the peaty deposits in Lake Sakata. The lake is closed by sand dunes without factories and influx rivers around there. After the next year the primary factor of arsenic concentration in lake deposits was mainly examined. The arsenic concentration in the surface deposits of Lake Sakata changed through one year with two peaks of June(Early Summer) and September(Early Autumn) ranged from 40 to 70ppm. The influence of the agricultural chemical, trade name "Arsenic-Lead", was examined but lead concentrations was normal of 10 to 26ppm. Li the drilling cores in the areas of eastern Sakata(5m depth), the Hayagata (50m), and the Uwasekigata(10m), buried lake or lagoon deposits were. Arsenic concentrated on peaty to organic deposits of 20 to 190ppm, 10 to 50m below the surface.In the Hetau Plain, China, arsenic concentrations range from 10 to 24ppm in peaty to muddy-organic, deposits, as well. The arsenic concentrations of the river water in the Huanghe(Yellow River) and tributary rivers to the Hetau Plain range from 14 to 17ppm and 17 to 22ppm each. This means that soils highly concentrated arsenic in the backland flowed out and in flood deposited in the plain.These evidence lead to the conclusions that the arsenic in the Alluvium derived from organic soils and the mechanism of the concentration of arsenic in the closed lake is considered due to biological action, e.g. Bioaccumulation.