放射性核種およびmolecular markerによる東京湾の堆積過程の解明

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To estimate the sedimentation rate and to understand the sedimentation processes in Tokyo Bay, vertical distributions of ^<210>Pb and ^<137>Cs were determined for two sediment cores (F-2 and F-5) from Tokyo Bay and one from the moat of Imperial Palace for the Tokyo. Molecular stratigraphy was applied to one of the Tokyo Bay sediment cores using polychlorinated biphenyls (PCBs) and linear and tetrapropylene-based alkylbenzenes (LABs and TABs). ^<210>Pb showed exponential downcore decrease with substantial fluctuation. In the sediment core of the bay (F-2), radiocesium maximum, corresponding to the atmospheric deposition maximum at 1963, was observed. Good agreement between the deposition date estimated using radionuclides (^<137>Cs and ^<210>Pb) and the vertical distributions of PCBs, LABs and TABs, suggests the utility of multiple markers approach for sediment stratigraphy. In the Tokyo Bay sediments, only slight or negligible decrease in ^<137>Cs activity was observed toward the surface layer where significant amounts of ^<137>Cs was detected, whereas a sharp peak of ^<137>Cs were observed for the Moat which has no inflowing rivers. PCBs and TABs, whose productions and usage ceased by early 1970s, decreased gradually to the sediment-water interface in the Tokyo Bay and were found significantly in the surficial sediments. All these markers suggest that riverine and estuarine sediments play a role of a reservoir of the pollutants, that is, particle-reactive pollutants are temporally deposited and stored in riverine and estuarine sediments which are intermittently supplied to Tokyo Bay during flood events with resuspension.
日本地球化学会の論文
1999-06-01

放射性核種およびmolecular markerによる東京湾の堆積過程の解明

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