Ecosystem uptake and transfer of Sellafield-derived radiocarbon (14C). Part 1. The Irish Sea

Ecosystem uptake and transfer processes of Sellafield-derived radiocarbon (14C) within the Irish Sea were examined. Highly variable activities in sediment, seawater and biota indicate complex14C dispersal and uptake dynamics. All east basin biota exhibited14C enrichments above ambient background while most west basin biota had14C activities close to background, although four organisms including two slow-moving species were significantly enriched. The western Irish Sea gyre is a suggested pathway for transfer of14C to the west basin and retention therein. Despite ongoing Sellafield14C discharges, organic sediments near Sellafield were significantly less enriched than associated benthic organisms. Rapid scavenging of labile,14C-enriched organic material by organisms and mixing to depth of14C-enriched detritus arriving at the sediment/water interface are proposed mechanisms to explain this. All commercially important fish, crustaceans and molluscs showed14C enrichments above background; however, the radiation dose from their consumption is extremely low and radiologically insignificant