HR: 15:15h
AN: OS43A-06    [Abstracts]
TI: Origin and Transport Mechanism of Iodine-129 to the Japan Sea
AU: * Suzuki, T
EM: suzuki.takashi58@jaeago.jp
AF: Research Group for Environmental Science, Japan Atomic Energy Agency, 4-24 Minato- machi, Mutsu, 0350064, Japan
AU: Kabuto, S
EM: kabuto.shoji@jaea.go.jp
AF: AMS Management Section, Japan Atomic Energy Agency, 4-24 Minato-machi, Mutsu, 0350064, Japan
AU: Amano, H
EM: amano.hikaru@jaea.go.jp
AF: AMS Management Section, Japan Atomic Energy Agency, 4-24 Minato-machi, Mutsu, 0350064, Japan
AU: Togawa, O
EM: togawa.orihiko@jaea.go.jp
AF: Research Group for Environmental Science, Japan Atomic Energy Agency, 4-24 Minato- machi, Mutsu, 0350064, Japan
AB: Iodine-129 is a long-lived radioisotope with a half life of 1.57 „e 107 years and produced naturally (129Inatural) by cosmic ray-induced spallation of xenon and spontaneous fission of uranium. Anthropogenic 129I has two main sources of releases into the environment during the last 60 years: one is nuclear weapons testing (129INWT) and the other is nuclear fuel reprocessing plants (129INFRP). Because of its long half life, anthropogenic 129I has a potential using as a tracer of the migration behavior of iodine for the last several decades. In this presentation, we discuss not only the origin but also the transport mechanism of 129I to the Japan Sea. Seawater samples were collected at the Toyama Bay and a region off Sekine in or near the Japan Sea. The concentrations of 129I in these samples were determined by accelerator mass spectrometry. The observed concentrations exceed the amounts expected from 129Inatural and 129INWT. The total fraction of 129Inatural and 129INWT is only a few percent. The majority of the concentration must come primarily from nuclear fuel reprocessing plants in Europe. This result indicates a rapid distribution of 129I through atmospheric transport on a global scale. A depth profile of 129I in a seawater column at the Toyama Bay shows that the 129I maximum is in a mixed layer and decrease with depth. The inventory of 129I in the Toyama Bay is four times higher than the Gulf of Mexico which has almost the same depth as the Toyama Bay. This higher inventory probably reflects: 1) the seawater rapid sinking in the Japan Sea, 2) the difference of sampling locations associated with a distance from 129I released points and latitudinal distribution and 3) the differences of sampling dates before which integrated emissions from nuclear fuel reprocessing plants differed.
DE: 4243 Marginal and semi-enclosed seas
DE: 4251 Marine pollution (0345, 0478)
DE: 4294 Instruments and techniques
DE: 4808 Chemical tracers
DE: 4875 Trace elements (0489)
SC: Ocean Sciences [OS]
MN: 2007 Joint Assembly