Radionuclides in the marine environment near the Farallon Islands

Isolated sediment areas containing plutonium and cesium radionuclide concentrations exceeding Pacific Ocean global radionuclide fallout levels have been reported in the Farallon Islands radioactive waste disposal area, west of San Francisco. We find the total 239+240Pu and 137Cs inventory of Farallon water columns to be within global fallout levels. The quantity of these radionuclides from nonfallout sources contaminating the sedimentary environment is unknown, but their contribution to the total water column inventory is insignificant compared with present fallout levels. Fish and invertebrates from the disposal region contain body burdens of 239+240Pu and 137Cs no greater than similar species exposed to global fallout. Within deep (2000 m) Farallon sediments, we do find that 238Pu concentrations exceeding anticipated fallout levels are being remobilized to bottom waters. Fallout plutonium appears to be displaced laterally from the continental shelf down the slope into deeper offshore waters. Remobilized waste from the disposal site probably is displaced in the same manner