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No.23 (1977/03) >

Title :南大東島および北大東島の池沼ならびに地下水の水質
Title alternative :Geochemical Studies of Underground and Lake Waters on both Minami and Kita Daito Jima
Authors :兼島, 清
平良, 初男
渡久山, 章
大森, 保
西浜, 完治
Authors alternative :Kaneshima, Kiyoshi
Taira, Hatsuo
Tokuyama, Akira
Oomori, Tamotsu
Nishihama, Kanji
Issue Date :Mar-1977
Abstract :The waters on both Minami and Kita Daito Jima have been collected, to discuss the geochemical natures on the islands, during last March 10th to 17th on 1976. The chemical analysis resulted in the following: Most of the lake waters on Minami Daito Jima fall in the average chlorinity of 0.26‰ , whereas the other waters collected from caves and wells present higher average chlorinity of 1.16‰. The chlorinities on Kita Daito Jima are also relatively high of 0.77‰ on the average. The study of correlation coefficients among chemical components, particularly the straightfoward positive correlation between sodium and chlorinity as in the same for sea water, strongly suggests the major influence of sea water on these islands. The other components such as K^+ and SO_4^=, also display nearly the same trend with those in sea water, but few samples give the evidence of contaminations which would be resulted from the human activities. The higher magnesium contents, however, may be concluded from the other cource of inputs besides the influences of sea water and human activities. The excess contents of magnesium in the ratio of Mg/Cl with respect to that in sea water may be resulted from the dissolution of dolomite which is one of the major carbonates in Daito Islands. Geochemical considerations of these excess magnesium and calcium are discussed in detail in this paper. The influence of the human activities on waters have also been studied for chemical components such as NH_<3^->N, O_2 and PO_<4^->,-P. And the vertical variations of the concentrations with depth and source of input in lakes on the islands have been verified. With the considerations of the data mentioned above, the present paper also estimated the main roots of incomming sea water from the open ocean toward to many lakes and marshes in Daito Islands.
Type Local :紀要論文
Publisher :琉球大学理工学部
URI :http://hdl.handle.net/20.500.12000/24475
Citation :琉球大学理工学部紀要. 理学編 = Bulletin of Science & Engineering Division, University of Ryukyus. Mathematics & natural sciences no.23 p.13 -41
Appears in Collections:No.23 (1977/03)

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