HR: 0800h
AN: OS11B-0512    [Abstracts]
TI: ¹³⁷Cs inventory in semi-isolated basins of the western South Pacific
AU: * Yamada, M
EM: m_yamada@nirs.go.jp
AF: Nakaminato Laboratory for Marine Radioecology, National Institute of Radiological Sciences, Isozaki 3609, Hitachinaka, Ibaraki, 311-1202, Japan
AU: Wang, Z
EM: wangzhongliang@vip.skleg.cn
AF: State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guanshui Road 46, Guiyang, Guizhou, 550002, China
AB: The main introduction routes of ¹³⁷Cs into the Pacific Ocean are worldwide global fallout from atmospheric nuclear weapons testing and close-in fallout from U. S. tests conducted on the Bikini and Enewetak Atolls. The objectives of this study are to measure the ¹³⁷Cs activities in water columns of the western South Pacific Ocean and to discuss the processes controlling the ¹³⁷Cs inventory. The ¹³⁷Cs activities were determined for seawater samples from the East Caroline, Coral Sea, New Hebrides, South Fiji and Tasman Sea Basins of the western South Pacific Ocean. The ¹³⁷Cs activities in surface waters ranged from 1.7 Bq m^{- 3} in the Tasman Sea Basin to 2.3 Bq m^-3 in the East Caroline Basin. The latitudinal ¹³⁷Cs distributions in surface waters showed the opposite trend to the expected deposition density from global fallout. The distribution profiles of ¹³⁷Cs activity at these six western South Pacific Ocean stations did not differ from each other significantly. The total ¹³⁷Cs inventories in the western South Pacific Ocean ranged from 850 Bq m^-2 in the Coral Sea Basin to 1270 Bq m^-2 in the South Fiji Basin. Higher ¹³⁷Cs inventories were observed at middle latitude stations in the subtropical gyre than at low latitude stations. The ¹³⁷Cs inventories were 1.9 - 4.5 times higher than that of the expected deposition density of atmospheric global fallout at the same latitude. The possible sources of excess ¹³⁷Cs inventories in the western South Pacific Ocean might be attributable to both the inter-hemisphere dispersion of the atmospheric nuclear weapons testing ¹³⁷Cs from the northern stratosphere to the southern one and its subsequent deposition, and water- bearing transport of ¹³⁷Cs from the North Pacific Ocean to the South Pacific.
DE: 4243 Marginal and semi-enclosed seas
DE: 4808 Chemical tracers
DE: 4860 Radioactivity and radioisotopes
SC: Ocean Sciences [OS]
MN: 2007 Fall Meeting