Influences of Marine Sediment on the Accumulation of Radionuclides by Green Alga (Ulva pertusa)

Distributions of radionuclides (60Co, 137Cs, 95Zr-95Nb and 106Ru-106Rh) among green alga (Ulva pertusa), sea water and marine sediment were examined by radioisotope tracer experiment in order to estimate the influence of sediment on the accumulation of radionuclides by the alga. By the application of the compartment model to the experimental results. exponential formulas of distributions were obtained. Through comparison of the transfer coefficients of radionuclides calculated from the exponential formulas, the influence of the sediment on the accumulation of the radionuclides by the green alga was determined to be the largest for 60Co, followed by 95Zr-95Nb, 106Ru-106Rh and 137Cs in this order. The activity ratios of 95Zr-95Nb and 106Ru-106Rh calculated from the transfer coefficients are larger for the alga than for the sediment, inversely those of 60Co and 137Cs show higher values for the sediment than for the alga. Especially, in the case of 60Co, the activity ratio for the sediment is approximately 20 times greater than that for the alga. Biological half lives in green alga estimated from the transfer coefficients were 10 days for 60Co, 7 days for 137Cs, 26 days for 95Zr-95Nb and 24 days for 106Ru-106Rh.