Mean residence time of plutonium isotope in the North Pacific Ocean

Abstract

The ^239+240Pu concentrations in seawater from the North Pacific Ocean were determined to estimate its Pu mean residence time. In the western North Pacific, the ^239+240Pu concentration increased with depth; a subsurface maximum was identified at 500 m depth and then decreased with depth. Its water column inventory was was 1.6 times more ^239+240Pu in the entire water column than would be expected from atmospheric global fallout. The decreasing rate and mean residence time were estimated from water column inventory between surface and 1000 m depth.