北海道豊富温泉の地球化学的特徴と有機成分の起源生物. (Japanese)

Geochemical Characteristics of Toyotomi Hot Spring in Hokkaido, Japan and the Source Organisms of Organic Components. (English)

We studied major chemical components and organic components in Toyotomi hot spring to elucidate their geochemical characteristics and the sources of organic components in hot spring waters, suspended solids, Yunohana (hot spring deposit) and oil samples. Major chemical components were Na⁺, Cl^- and HCO3-, and composed of NaCl and NaHCO3. Dissolved salts in fossil seawater and bicarbonate ion originated from decomposition of organic components formed these salt composition. Ca²⁺ and Mg²⁺ were partly deposited under weak alkaline conditions. SO4^2- was reduced into H2S under reductive conditions and removed from water bodies. A series of n-alkanes were completely disappeared probably due to microbial decomposition of hydrocarbons. Sterane composition showed that major sources of hydrocarbons are vascular plants with some influences of diatoms. Oils are mainly derived from the Haboro Formation formed in flubio-deltaic environments containing coal, and are considerably influenced by Koitoi Formation formed in marine environment composed of diatomaceous soft mudstone. Fatty acids and sterols are, however, derived from mainly microorganisms, such as microalgae as well as small amounts of eubacteria and vascular plants in the hot spring environments. Epimerization of triterpanes attained near thermal equilibrium state, but no steranes reached equilibrium state, and thus were moderately influenced by thermal stress in sedimentary environments. [ABSTRACT FROM AUTHOR]

本研究では豊富温泉の主要化学成分と有機成分の地球化学的特徴を明らかにし, 有機成分の 起源を解明するために, 温泉水, 懸濁物, 湯の花および油分の分析を行った．主要化学成分は ナトリウムイオン, 塩化物イオンおよび炭酸水素イオンからなり, 食塩と重曹から構成される． 化石海水が主要な塩分であるが, 有機成分の分解による二酸化炭素から炭酸水素イオンが加 わったと考えられる．カルシウムイオンとマグネシウムイオンは弱アルカリ性で一部が沈殿除 去, 硫酸イオンは堆積環境で硫化水素に還元され除去された．炭化水素は一連のn-アルカン が全く見られず, かなりの程度で微生物分解を受けていると判断される．有機成分の起源は, 油分についてはステラン組成より維管束植物の寄与が最も大きく, 珪藻の寄与がかなりあり, それ以外の藻類の寄与は極めて小さい．油分は新生代古第三紀の石炭を含む羽幌層（三角州堆 積物）が主要な起源で, 新第三紀の珪質岩の影響がある．堆積環境は三角州堆積物から海底堆 積物であると考えられる．その他の有機成分は脂肪酸組成およびステロールから現世の藻類成 分が卓越し, 少量の真正細菌および維管束植物の影響があるとみることができる． トリテルパンのエピ化はほぼ平衡に達しているが, ステランのエピ化は平衡に達しておら ず, オイルの熟成度は中程度である．豊富温泉にはオイル中のタール成分（タール療法）がアト ピー性皮膚炎と尋常性乾癬に対する有効性が認められており, 今後の継続研究が重要である. [ABSTRACT FROM AUTHOR]

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