Some Fallout Radionuclides in Deep Waters around Japan

Deep water samples collected in 1963 and 1964 in the adjacent seas of Japan were analyzed radiochemically. Sr-90 and Cs-137 were detected in the deep layers down to 6,000 meters deep and showed approximately uniform vertical distributions below 1,000 meters. Mean concentrations of Sr-90 in deep waters were 0.028 ƒÊƒÊc/l in the Pacific and 0.035ƒÊƒÊc /l in the northern Japan Sea, and those of Cs-137 were 0.034 and 0.075 ƒÊƒÊc/l respectiviely. The mean Cs-137/Sr-90 ratios in deep layers of the Pacific showed uniform distribution and the mean value of 1.4, but in the northern Japan Sea, remarkably higher value of 5.5 due to the Sr-90 depletion was found in 1,000 to 2,600 meters layer. Vertical distribution of Ce-144 suggests strong biological retention within the surface layer, and from the apparently uniform distribution in deep layers, 400 meters per month was estimated as the sinking rate