Division of Marine Radioecology

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Information on ecological behavior of radionuclides in the marine environment is indispensable for evaluating the effects of radioactive substances originating from uses of nuclear energy.

Research work in the Division is comprised of radioisotope tracer experiments in the laboratory and field surveys on concentrations of radioactive and stable isotopes in marine environmental samples.

Accumulation of Radionuclides by Marine Organisms

Concentration factors of radionuclides by marine organisms are derived from the accumulation and excretion rates of radioisotopes as observed in aquarium experiments.

Accumulation through the food chain of other factors, such as chemical forms of nuclides, temperature, and sizes of the organisms, affecting the concentration factor values are also examined in experiments.

Characterization of Elements in Marine Environmental Samples

Characterization of stable isotopes in marine environmental samples, such as organisms, seawater, and sediments are carried out to determine the ecological behavior of radionuclides. Elemental concentrations in samples are measured by AAS, ICP-AES, ICP-MS and PIXE. Elemental distributions in tissues of marine organisms are examined by electron microscopy. Chemical forms (oxidation state, coordination number and local structure for a specific element) are determined by X-ray diffraction and XAFS techniques.

[Influences of intake pathways] Influences of intake pathways and food habits on distribution of radionuclides among tissues and organs of aquatic organismus.
A: herbivorous, B: carnivorous
S: shell, M: muscle, L: liver, O: other parts
large size image is here. (25 kbyte)




Field Survey on Long-lived Radionuclides and Natural Radionuclides

   Distributions of fission products or transuranium nuclides in coastal and deep ocean waters are surveyed continuously to obtain basic information for estimating the behavior of radioactive substances when released into these waters from nuclear facilities.

   Naturally occurring radionuclides are studied as well in seawater, suspended matter and sediments so as to predict the circulation of these elements in marginal seas and oceans.
The resultant information is applied to formulation of radiological models to evaluate the transfer of long-lived radionuclides to seafoods.


[Sediment trap experiments]
Sediment trap experiments: Sediment traps have been used to collect settling particles in a time-series and to investigate the vertical and lateral transport of radioactive nucldes in the ocean.




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Major Publications


    

  1. Hirano, S., Matsuba, M. and Kamada, H.: The Determination of 99Tc in Marine Algae. RADIOISOTOPES, 38. 186-189, 1989.

  2. Nakamura, K. and Nagaya, Y.: Distribution of 137Cs and 239,240Pu in the Sediment of the Seto Inland Sea. J. Radioanal. Nucl. Chem Articles, 138, 153-164, 1990.

  3. Ueda, T., Ishii, T., Nakahara, M., Nakamura, R., Suzuki, Y. and Shimizu, C.: Element in Gonad of the Sea Urchin Strongylocentrotus nudus. Nippon Suisan Gakkaishi, 57, 1095-1102, 1992.

  4. Nagaya, Y. and Nakamura, K.: 239,240Pu and 137Cs in the East China and the  Yellow Seas. Journal of Oceanography, 48, 23-35, 1992.

  5. Ishii, T., Nakahara, M., Matsuba, M., and Ishikawa, M.: Determination of 238U in Marine Organisms by Inductively Coupled Plasma Mass Spectrometry. Nippon Suisan Gakkaishi., 57, 779-787, 1991.

  6. Ishikawa, M., Nakamura, K.,  Ishii, T., Bassari, A., Okoshi, K. and Kitao, K.: Elements in Tissues and Organs of an Antarctic Fish, Champsocephalus gunnari. Nucl. Instr. & Methods in physics Research, B75 204-208, 1993.

  7. Suzuki, Y. Nakamura, K., Nakamura, R., Nakahara, M., Ishii, T., Matsuba, M. and Ngaya, Y.: Radioecological Studies in the Marine Environment. Proceedings of International Conference on Radiation Effects and Protection, 484-491, 1992.

  8. Ishii, T., Nakai, I., Numako, C., Okoshi, K. and Otake, T.,: Discover of a New Vanadium Accumulator, the Fan Worm Pseudopotamilla occelata. Naturwissenschaften, 80, 268-270, 1993.

  9. Nakahara, M.: Concentration of Radionuclides by Marine Organisms and their Food Chain. (in Japanese) Proceedings of The Twentieth National Institute of Radiological Sciences Seminar on Environmental Research, 13-22, 1993.

  10. Hirano, S. and Matsuba, M.: Concentrations of Technetium-99 in Marine Algae and Seawater. Radiochimica Acta, 63, 79-82, 1993.


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