深海堆積物中のラジウムの挙動

概要

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Two deep-sea sediments taken from the wastern North Pacific Ocean were analyzed for ^<232>Th, ^<230>Th and ^<226>Ra. The observed vertical distributions of ^<226>Ra fit pretty well with those having diffusion coefficients of 1-3x1O^<-9>cm^2/sec. The flux of ^<226>Ra out of the sediment are calculated to be 0.022 dpm/cm^2/yr to 0.037 dpm/cm^2/yr from the deficiency of ^<226>Ra relative to ^<230>Th in the sediments. This indicates that ^<226>Ra in sea water is mainly supplied from bottom sediments. The concentration of ^<226>Ra in the layer extremely enriched in Mn was also in large excess relative to its parent ^<230>Th. This fact may be due to its post depositional migration and adsorption on Mn oxide. The deposition rate of ^<226>Ra in the Mn rich layer is estimated to be 0.0065 dpm/cm^2/yr and 0.010 dpm/cm^2/yr from the excess of ^<226>Ra. The rates of migration of heavy metals (e.g. Ni and Co) in the sediments are also discussed by applying the above results on ^<226>Ra.
日本地球化学会の論文
1981-12-30