Lingering radioactivity at the Bikini and Enewetak Atolls

Decades after nuclear testing, Bikini and Enewetak Atolls remain significant sources of plutonium (Pu) and cesium-137 (Cs) to the North Pacific, though at rates far lower than initial fallout. Research reveals that Pu levels in lagoon seawater and sediments are orders of magnitude higher than global averages, with the Runit Dome—an underground nuclear waste repository—contributing roughly half of the Pu detected in Enewetak’s lagoon water column. Submarine groundwater discharge (SGD) plays a minor role in transporting these radionuclides, suggesting that seafloor sediments are the primary long-term repository and source. While Cs levels are elevated in brackish groundwater, its presence in lagoon waters is only slightly higher than in the broader North Pacific. The study employed radium isotopes to estimate SGD for the first time in this context, providing critical insights into radionuclide fluxes.

Buesseler, K. O., Charette, M. A., Pike, S. M., Henderson, P. B., & Kipp, L. E. (2018). Lingering radioactivity at the Bikini and Enewetak Atolls. Science of the Total Environment, 621, 1185–1198. https://doi.org/10.1016/j.scitotenv.2017.10.109