47・7豪雨による西三河山腹崩壊地域の天然水の水質 [in Japanese] The chemical compositions of stream waters in an earth flow area (Nishimikawa, Aichi Prefecture) [in Japanese]
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An earth flow occurred on 12th to 13th of July, 1972, in more than 3,000 locations in Obara-mura (area: 75km<sup>2</sup>), Nishimikawa of Aichi Prefecture. Water samples were taken from the earth flow area and analyzed for Na<sup>+</sup>, Ca<sup>2+</sup>, Mg<sup>2+</sup>, Cl<sup>-</sup>, HCO<sub>3</sub><sup>-</sup>, SO<sub>4</sub><sup>2-</sup> and soluble SiO<sub>2</sub>. The concentrations of Ca<sup>2+</sup>+Mg<sup>2+</sup> and HCO<sub>3</sub><sup>-</sup> were varied greatly from location to location, indicating the difference of the dissolution of Ca<sup>2+</sup>+Mg<sup>2+</sup> in waters from clay, sand and rock materials in the different areas. The chemical compositions of the waters indicate that the earth flow occurred only owing to a very heavy rain, and that in some locations a chemical weathering is progressing rather actively to form clay materials under the ground through the interaction of carbonated water with rock materials.
Chikyukagaku 6(1), 21-27, 1973
The Geochemical Society of Japan