Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Otosaka, Shigeyoshi; Togawa, Orihiko; Tanaka, Takayuki; Amano, Hikaru; Minakawa, Masayuki*
no journal, ,
In order to understand biogeochemical cycles of particulate materials in the deep part of the Japan Sea, we assessed processes and a time scale of transport of particulate materials by measurements of particulate lead-210 (210Pb) and organic radiocarbon (14C) in settling particles collected in three regions of the Japan Sea; the western Japan Basin (WJB), the eastern Japan Basin (EJB) and the Yamato Basin (YB). Values of delta-14C in settling particles collected at 1 km depth ranged -13
22 per mill, and there were little differences in delta-14C between sampling stations. In the YB, delta-14C values of settling particles collected in the bottom layer (about 200 m above the bottom) were similar to those in 1 km depth. On the other hand, the delta-14C values in bottom layer in the WJB and EJB were about 55 per mill smaller than those at shallower layers. These results in indicated that the deep part of the Japan Basin had a larger time scale of POC cycle than the Yamato Basin. By a comparison of mass balance of 210Pb between the WJB and EJB, it was estimated that about 60% of particulate 210Pb supplied to the WJB exported horizontally to the EJB.
Kobayashi, Takuya; Otosaka, Shigeyoshi; Togawa, Orihiko
no journal, ,
A spent nuclear fuel reprocessing plant would release artificial radionuclides from a discharge pipe to the marine environment. These readionuclides spread by advection and diffusion of ocean currents, but their migration processes are different due to physical and chemical forms of radionuclides. We have developed a numerical simulation model system that consists of an ocean current model and a particle random-walk model to describe the radionuclide migration behavior in a shallow water region. The ocean current model is the modified Princeton Ocean Model (POM). The POM calculates tidal currents by giving tide levels at the open boundary. The particle random-walk model, SEA-GEARN, calculates the radionuclides migration in the ocean. Radionuclides that exist in the ocean are modeled in three phases, such as dissolved in seawater, adsorbed with suspended solids and adsorbed with active bottom sediment. The adsorption and desorption processes between the dissolved and solid phases are solved with the kinetic transfer coefficients by the stochastic method. Deposition of suspended solids and resuspension of bottom sediment are also considered. The system has been applied to simulate the long-term dispersion of 
Cs and 
Pu in the Irish Sea where these radionuclides are actually released from a spent nuclear fuel reprocessing plant. The calculation results and observations have been compared at several points in order to validate the developed models.