In order to examine radioecologically behavior of radionuclides in environment of water supply, levels of radionuclides in the soil, raw water from river and its suspension, river bottom sediment, and water supplied for drinking were quantitatively investigated, and then various aspects on transfer of radionuclides in the land, river, and water works were hydrometeorologically analyzed. On three basins, Agano, Edo, and Yodo River, movements of 106Ru, 137Cs and 144Ce were derived from data of 90Sr. 90Sr was removable compared with other radionuclides in various samples. The following equations were established by the regression analysis between "ratio on each of the radionuclides to 90Sr" in soil (Rd) and that of river bottom sediment (RBS), between Rd and that in river water with suspension (R[W+S]), and between radionuclides concentration in the river water (C ; pCi/100 liter) and weight of the river suspension (S ; gr. of ash/100 liter). [numerical formula] Coefficients a1 and b1 were 8.46-1.35 and 2.35-0.62 for 106Ru, 4.14-0.989 and 2.58-0.31 for 144Ce, and 2.80-0.836 and 3.49-0.879 for 137Cs, respectively. The a2 and b2 for 137Cs were 0.085-0.055 and 0.26-0.19. The a3 and b3 in the Agano River were 0.00229 and 1.49 for 90Sr, and 0.0229 and 0.64 for 137Cs. These data indicated that the degree of deposition to the soil, adsorption, and absorption to the river bottom of 106Ru, 137Cs and 144Ce are higher than those of 90Sr, in the following order : 106Ru>144Ce>137Cs>90Sr. As for the pathway of contamination, part of 90Sr is soluble and most of 106Ru, 137Cs and 144Ce is insoluble in the river, and a part of these radionuclides exists in the river suspension and considerable amounts of 106Ru, 137Cs and 144Ce are precipitated on the river bottom. It was observed on the decontamination rates (DR%) of radionuclides in the water works that the greater the content of the suspension increases, the higher DR become. The correlation of DR and S was shown by the following equation. [numerical formula] The coefficient a4 was 0.0462 for 137Cs in the Niitsu City water works, Agano River basin. During 1962 to 1969, DR in the three water works were observed as 50% for 106Ru, 48% for 144Ce, 31% for 137Cs, and 15% for 90Sr in average value.
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