沖縄島の湧水と河川水の化学的特徴と同位体組成

• 東田 盛善

  沖縄県立八重山商工高等学校

• 佐竹 洋

  富山大学理学部生物圏環境科学科

• 渡久山 章

  琉球大学理学部海洋自然科学科

書誌事項

タイトル別名

• Chemical characteristics and isotopic compositions of spring and river waters in Okinawa Island
• オキナワトウ ノ ユウスイ ト カセンスイ ノ カガクテキ トクチョウ ト ドウイタイ ソセイ

抄録

Spring waters from limestone terrains of the southern area of Okinawa Island have been analysed for chemical and isotopic compositions. The isotopic compositions of river waters from the central and northern areas of the island have also been measured. Spring and river water samples were collected during the following periods: spring waters from April 26th to June 28th, river waters June 1 st and 2nd, and July 20, 21 and 22, 1996, respectively. P_CO2 of spring waters is 10^-2.3 to 10^1.1 atm. These high P_CO2 are probably caused by a large supply and fast decomposition of litter, owing to the climatic characteristics of the island. High concentrations of Ca²⁺ and HCO₃^- in spring waters may be caused by the reaction of limestone with CO₂. High concentrations of SO₄^2-, HCO₃^- and excess Na⁺ (Na⁺ of non sea water origin) are found in spring waters from the southern area. These Ca-SO₄・HCO₃ type spring waters are possibly formed by oxidation of pyrite occurring in the bedrock (Shimajiri Group). Equilibrium relationships among the spring water, feldspar, and clay mineral suggest that spring waters may be equilibrated with kaolinite. The NO₃^--N content of spring waters has been increased by contamination with chemical fertilizers and waste waters from domestic areas. The increment is striking in the central areas, comparing with data of 1987. Values of δD and δ¹⁸O for spring and river waters are -36 to -18‰ and -5.6 to -3.3‰, respectively. These values are almost the same with those of groundwaters in Hateruma and Yonaguni Islands, located about 2° south of Okinawa Island. This is probably due to that the water vapor in these areas are mainly recharged from the sea around the islands. The d-parameter (d=δD-8δ¹⁸O) of spring and river waters ranges from 2.8 to 13.4 with an average of 8.6. This indicates that these waters are mainly recharged with precipitations from the Pacific Ocean airmass in summer.

収録刊行物

• 地球化学

  地球化学 35 (1), 27-41, 2001

  一般社団法人日本地球化学会

キーワード

• spring water
• river water
• chemical composition
• isotopic composition
• limestone area
• nitrate

詳細情報

• CRID: 1390282680717748608
• NII論文ID: 110008680015
• NII論文ID: 10008433041
• NII書誌ID: AN00141280
• DOI: 10.14934/chikyukagaku.35.27
• ISSN: 21885923
• ISSN: 03864073
• NDL書誌ID: 5711955
• Web Site: https://ndlsearch.ndl.go.jp/books/R000000004-I5711955
• 本文言語コード: ja
• データソース種別:
  • JaLC
  • NDL
  • CiNii Articles
  • Crossref
• 抄録ライセンスフラグ: 使用不可