南西諸島第四紀石灰岩中のカドミウム含量

概要

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Cadmium contents of limestone samles were determined by flame atomic absorption spectrometry combined with ammonium pyrrolidinedithiocarbamate (APDC)-4-methyl-2-pentanone (MIBK) solvent extraction system. The Cd contents of Quaternary limestones occurring in the Nansei Islands are independent of the amount of impurities such as silicates or oxides, the fact suggesting that Cd^<2+> may be directly incorporated into calcite by replacing Ca^<2+> in the lattice. The geometric mean and the median of Cd in the present samples (n =94) are both 0.07_1ppm, which is quite similar to Mason and Moore's value (0.09ppm) of this element in carbonate rocks. The Cd contents of Quaternary limestones may be largely controlled by the concentration of this element in aragonite, high-Mg calcite and low-Mg calcite in unconsolidated carbonate sediments which are the precursor of these limestones. During the formation of pure Quaternary limestones, Cd seems to behave together with Zn. However, the observed enrichment of Cd relative to Zn in these limestones might be caused through the above replacement mechanism.
日本地球化学会の論文
1992-09-24