著者

網田 和宏 大沢 信二 西村 光史 山田 誠 三島 壮智 風早 康平 森川 徳敏 平島 崇男

出版者

日本水文科学会

雑誌

日本水文科学会誌 (ISSN:13429612)

巻号頁・発行日

vol.44, no.1, pp.17-38, 2014-02-28 (Released:2014-05-28)

参考文献数

45

被引用文献数

2 3

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温泉起源流体としての変成流体を探索するために,西南日本の前弧域の中央構造線沿いに湧出する高塩分温泉において,温泉水や付随ガスを採取し化学・同位体分析を行った。その結果,和歌山と四国地域で採取した温泉水試料から,現海水や浅層地下水に比べて水素・酸素安定同位体組成の大きく異なる温泉を見出した。四国地域の温泉起源流体は,Li-B-Cl相対組成やHe同位体システマティクスから,続成流体の一つであることが確認された。一方,和歌山地域の温泉起源流体は,続成脱水流体とは異なるLi-B-Cl相対組成を示し,また高い3He/4He比を有していることから,大分平野で得られたものと同様,その起源が変成脱水流体にあると判断された。和歌山,大分の温泉起源流体と四国,宮崎のそれでは,付随ガスの化学組成において前者がCO2に富むのに対して後者はCH4に富むという明瞭な違いが認められ,また,和歌山と大分の付随ガスに含まれるCO2の大半が,沈み込み帯の火山ガスと同様に,海成炭酸塩に由来するものであることが示された。さらにこれら起源流体のLi-B-Cl相対組成は,続成脱水流体と火山性熱水流体のそれの中間的な値を示した。これらの結果は全て,和歌山と大分の温泉起源流体が,沈み込むフィリピン海プレートより脱水してきた変成脱水流体であることを示唆しているものと考えられた。

著者

大沢 信二 三島 壮智

出版者

特定非営利活動法人日本火山学会

雑誌

火山 (ISSN:04534360)

巻号頁・発行日

vol.62, no.1, pp.31-36, 2017-03-31 (Released:2017-03-28)

参考文献数

15

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Free CO2 gas of deep (mantle+subducting slab) origin has been discharging accompanied by cold spring water of Hyoshimizu Hot Spring located at the eastern coast of Himeshima island, which is a Pleistocene volcanic island located northeast of Kyushu, Japan. On the western side of this island, it can be also observed free gas upwelling off the coast of Nishiura village. Therefore, we sampled upwelling bubble gas for the first time and report chemical and isotopic compositions of the sample gas. The major chemical component of the bubble gas from the Nishiura submarine gas discharge (Nishiura SGD) is CO2 as in the gas associated with the Hyoshimizu Hot Spring. The He-Ar-N2 relative composition and the 3He/4He-4He/20Ne relation of the Nishiura SGD gas are common with those of the free gas of Hyoshimizu Hot Spring and indicate that the Nishiura SGD gas will be of deep origin. However, the Nishiura SGD gas is rich in CH4 while its concentration in the free gas in Hyoshimizu Hot Spring is negligibly small. The carbon isotope composition (δ13C) of CH4 in the Nishiura SGD gas suggests that it should be of abiogenic origin. Since we found gases released on the eastern and western coasts of Himeshima island are both derived from deep, it is expected that such deep-originated gas seeps out to the atmosphere from ground inland of Himeshima island.

著者

三島 壮智 大沢 信二 山田 誠 北岡 豪一

出版者

日本水文科学会

雑誌

日本水文科学会誌 (ISSN:13429612)

巻号頁・発行日

vol.38, no.4, pp.157-168, 2009 (Released:2011-03-25)

参考文献数

8

被引用文献数

2

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A spectrophotometric method using bromocresol green (BCG) is proposed for determination of bicarbonate ion (HCO3-) in a small amount of environmental water samples. This method is based on variation of absorption spectrum of BCG accompanied with neutralization of an acid solution by HCO3- : H++HCO3- → H2CO3. Relation between HCO3- concentration and absorbance ratio at two wavelengths of 445 nm and 616 nm (A616⁄A445) in a concentration-defined HCl solution with BCG can be theoretically expressed by the equation derived from combining of the Lambert-Beer's law and the Henderson-Hasselbalch equation. The serious dissolution of atmospheric CO2 into pure water and standard solutions for the calibration curve can be evaded by a theoretical correction using pH and water temperature measured in laboratory, and then HCO3- from several mg⁄L to ca. 500mg⁄L in sample water of less than 0.3 mL can be rapidly determined. Comparing the new method to the conventional titration method using some environmental waters, mean analytical values obtained by this method are close to those from the titration method and the coefficient of variation of this method is shown to be about 2 times that of the titration method. An application of this new method to drip waters in a limestone cave, whose outflow rates were extremely low (several mL⁄min.), offers the possibility that this method is especially useful when sample water volumes are restricted.