No long-term variation of Pu/Pu atom ratio in liver of Japanese common squid (Todarodes pacificus) collected from seven sea areas around Japan during 2003-2018.

The Pu concentrations and Pu/Pu atom ratios were determined to trace the temporal variability in concentration and atom ratio in liver of the Japanese common squid during 2003-2018. The differences in their concentrations and atom ratios and the dependency on the collection areas and migratory history were compared. The organ affinity of Pu in mantle, limb, liver, and internal organs except liver was also investigated. The average Pu concentrations were the highest in liver followed in order by internal organs except liver, limb, and mantle. The Pu accumulation in liver could be explained by a mechanism for foreign substance processing. A significant difference in the average Pu concentrations in liver was found among the sea areas for specimen collection during 2003-2018. In spite of a noticeable difference in the average Pu concentrations, the Pu/Pu atom ratios showed no significant temporal variability around Japan; thus, they were continuously uniform during 2003-2018.