239Pu, 240Pu, 241Pu, 241Am, 137Cs, and 210Pb in seafloor sediments in the western North Pacific Ocean and the Sea of Japan: distributions, sources and budgets

Vertical distributions of Pu-239, Pu-240, Pu-241, Am-241, Cs-137, and Pb-210 concentrations, and Pu-240/Pu-239 ratios were determined in seafloor sediments in the western North Pacific Ocean and the Sea of Japan to discuss the behavior of these radionuclides in the ocean and to identify the sources of anthropogenic radionuclides in the seafloor sediments. The excess Pb-210 accumulation rates were greater than the predicted rates from the overlying water column. A significant amount of the Pacific Proving Grounds-derived Pu and Am has been transported by ocean currents and it has been accumulated onto the seafloor sediments by enhanced particle scavenging.

Automated summary

This study investigated the vertical distribution, behavior, and sources of radionuclides in seafloor sediments in the western North Pacific Ocean and the Sea of Japan. The results showed that a significant amount of anthropogenic radionuclides, such as Pu and Am, has been transported by ocean currents and accumulated in the seafloor sediments.