Online ISSN : 1880-5973
Print ISSN : 0016-7002
ISSN-L : 0016-7002
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Distribution and supply mechanisms of high uranium concentration in the rivers of Okinawa Island, Japan
Akihito MochizukiKo HosodaMasahito Sugiyama
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2015 Volume 49 Issue 4 Pages e9-e14


Uranium concentrations in the rivers of Okinawa Island, Japan were determined in this study. Most rivers in the southwestern area of the island showed high U concentrations, the highest of which was 87 and 11 times the average U levels in Japanese rivers and worldwide, respectively. The U concentration in two rivers exceeded the Japanese guideline for public waters. Thermodynamic calculations revealed that the predominant U species in the rivers was Ca2UO2(CO3)30 (aq) because of high concentrations of calcium and carbonate ions. However, the U concentrations were not explained by either the congruent dissolution of limestone or the input of seawater and/or sea salt aerosols. Therefore, selective dissolution of U from limestone as well as from other rocks and soils via the formation of calcium-uranyl-carbonate complexes may be a possible mechanism for the high riverine U concentrations.

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© 2015 by The Geochemical Society of Japan
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