An Analysis of the Chemical Compositions of Groundwaters Utilizing a Leaching Technique. An Application to the Rokko Mountains and Their Surroundings

• Published in: Bulletin of the Chemical Society of Japan Vol. 55; no. 12; pp. 3760 - 3765
• Main Authors: Tamari, Yuzo, Inoue, Yukiharu, Tsuji, Haruo, Kusaka, Yuzuru
• Format: Journal Article
• Language: English
• Published: Tokyo The Chemical Society of Japan 01.12.1982; Chemical Society of Japan
• ISSN: 0009-2673; 1348-0634
• DOI: 10.1246/bcsj.55.3760

The chemical composition of groundwaters from granitic alluvial plains is different from that from the clayey “Kobe-group” strata surrounding the Rokko mountains. The former groundwaters are dominantly rich in Ca and HCO3, while the latter are rich in Na and HCO3. In order to investigate the difference in the groundwater compositions, a chemical leaching technique was applied to samples of soils, well-sediments, and rocks collected from the Rokko mountains and their surroundings. Three leaching solutions used were as follows. CO2− saturated water to investigate the effect of chemical weathering; a 0.1 M HNO3 solution to remove hydroxide, sulfide, and colloidal matters; and a 1 M CH3COONH4 solution to leach exchangeable ions from the samples. In the leaching, leachable amounts of Na, K, Ca, and Mg as the major species and Fe and Mn as the minor species in groundwaters were determined. From the results of leaching and adsorption experiments for cations, and from a comparison of the analytical values of the cations in groundwaters with the data of the leaching experiments on the key diagram, the association of the chemical species dissolved in groundwaters with the geological characters was analysed.