Plutonium in Southern Hemisphere ocean Waters

Plutonium in seawater collected by the BEAGLE2003 cruise was determined using ICP- SF-MS and alpha spectrometry after Fe co-precipitation and radiochemical purification. Levels and distributions of dissolved plutonium activity concentrations in Southern Hemisphere ocean waters are summarized here, including historical data. Pu-239 concentrations in surface water----of the central South Pacific (32.5 °S) in 2003 were around 1 mBq/m3. The 239Pu concentrations in the Indian Ocean surface waters (20°S) were similar to that in the South Pacific, whereas the 239Pu concentrations in the South Atlantic surface waters (30°S) were markedly lower than those in the South Pacific and Indian Oceans. The 239Pu vertical profile pattern was similar to that in the North Pacific subtropical gyre, although 239Pu concentrations in the deep South Pacific were significantly lower than those in the North Pacific. One of the dominant factors controlling plutonium distributions in the Southern Hemisphere oceans is biogeochemical processes including particle scavenging.