| Budget Amount *help |
¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 1999: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1998: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1997: ¥800,000 (Direct Cost: ¥800,000)
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| Research Abstract |
The boron isotopic composition were measured about coral 28 samples collected on offing the Okinoerabu iland, the Tonaki island, and the Miyako island of the Okinawa southwest islands. The kind of coral used two species of helioporas, 20 species of acroporas, two species of montiporas, and four species of poriteses, respectively. Boron was separated from the about 6g sample by the methyl borate distillation, and the boron isotopic ratios were measure. Moreover, the determination of the element which exists in a sample was carried out by emission spectrochemical analysis. Consequently, Na, K, Li, Mg, Sr, Ba, and B were contained as main coexistence elements. Many Sr, Ns, and Mg were contained in it. As for some coral, the crystal form changed with coexistence of magnesium from the aragonite to the calcite in part. This is guessed from positive correlation being between magnesium concentration, and C / A ratio. There was no correlation between boron concentration or an isotopic ratio, and other chemistry components. Boron concentration was 20-50 ppm, the average was 40.95 ppm, and the standard deviation was ±7.23 ppm. Boron isotopic ratios are 4.107-4.158 (15.8-28.3% as deltaィイD111ィエD1B), the boron isotopic ratios in 26 samples of the others except heliopora are 4.133-4.158, and the average was set to 4.141. The standard deviation at this time was ±0.008, and was the variation in a very narrow sphere. This value showed theoretical calculation and very good coincidence. However, a difference is looked at by a coexistence element, the isotopic ratio, etc. between the coral of heliopora and others, and the boron isotopic ratio in the coral of heliopora showed the in addition to this more low boron isotopic ratio. This is considered to suggest that it may be a certain biologically different isotope effect.
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