Initial Strontium-90 concentrations in ocean sediment from the northern Marshall Islands

The United States detonated 67 nuclear weapons in the Marshall Islands from 1946 to 1958. While there has been significant study of the aftereffects of these explosions over the decades that followed, few values of strontium-90 (90Sr) contamination have been reported. Sediment cores from the Bravo test crater in Bikini Atoll and Lacrosse crater near Runit Island (Enewetak Atoll) were assessed for 90Sr and cesium-137 (137Cs) concentrations, which were found to be measurable in all cores. 90Sr values were found to be roughly consistent across the tested cores. Ratios of 90Sr/137Cs are elevated compared to values measured previously at other sites of weapons testing and nuclear accidents. These findings suggest the need to further investigate 90Sr concentrations in the northern Marshall Islands to assess the safety of current residents in light of the potential for 90Sr conveyance and to provide input regarding resettlement of currently unoccupied islands and atolls.