The present plutonium levels in the Pacific Ocean are summarized. The 239,240Pu concentrations in surface seawaters in the early 2000s were in the range of 1.5 to 9.2 mBq·m−3 in the North Pacific and 0.8 to 4.1 mBq·m−3 in the South Pacific. There is no marked difference of surface 239,240Pu distributions between the North and South Pacific subtropical gyres. The vertical profile of 239,240Pu in the South Pacific was the similar pattern to that in the North Pacific, which is controlled by biogeochemical processes.
The 239,240Pu inventories (down to 2300 m) in the North Pacific are generally greater than that in the South Pacific, which reflects
the geographical distribution of global fallout and effect of close-in fallout in the Marshall Islands.