Insights into plutonium in marine biota along the coast of China

Radiation risk through seafood consumption is a big public concern under the discharge of nuclear contaminated water. Plutonium is an important radionuclide in view of radiation risk due to its high radiological and chemical toxicity, as well as consistent presence in the environment. The distribution and level of plutonium isotopes (²³⁹Pu, ²⁴⁰Pu) in marine biota collected along the coast of China in 2022-2023 were investigated. The ^239,240Pu concentrations showing an increasing tendency from fish, shrimp to macroalgae, depending on species and growing environment. The atomic ratios of ²⁴⁰Pu/²³⁹Pu (0.158-0.275) in marine biota in the China Seas indicated other source in addition to the global fallout of Pu. The elevated ²⁴⁰Pu/²³⁹Pu ratios observed in the East and South China Sea in comparison with the Yellow Sea and Bohai Sea were attributed to the intrusion of the Kuroshio Current carrying Pacific Proving Grounds (PPG) sourced plutonium with high ²⁴⁰Pu/²³⁹Pu ratios, accounting for up to 70 % of total plutonium. The annual radiation dose of plutonium through seafood consumption is in a secure level at present by the public. Macroalgae serves as an ideal marine indicator for plutonium isotopes pollution. The PPG-derived dissolved and colloidal plutonium dominates the enrichment of plutonium in Ulva linza.