Abstract
The plutonium content of the water sampled from ten main rivers in Japan was determined. The average content of total plutonium is 0.37 fCi 1-1 in which 0.09 fCi 1-1 is associated with suspended matter. Considering that 27% of the total plutonium is derived directly from rain drops on the river surface, the amount of leaching from drainage is estimated to be only 0.03% of the accumulated plutonium on land (1.2 mCi km-2). This suggests that plutonium is adsorbed on the soil surface firmly and it is difficult to be leached out to river water.
