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 a
1 and b
1 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 a
2 and b
2 for
137Cs were 0.085-0.055 and 0.26-0.19. The a
3 and b
3 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 a
4 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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