Anthropogenic Radiocarbon in the Eastern Irish Sea and Scottish Coastal Waters

Abstract

14C is produced as an activation product in nuclear reactors, and may be discharged to both the atmosphere and the marine environment during nuclear fuel reprocessing. In the UK, 14C is discharged, under license, into the Eastern Irish Sea by the British Nuclear Fuels plc (BNFL) reprocessing plant at Sellafield, Cumbria, northwest England, and is then transported into Scottish coastal waters. We analyzed intertidal biota samples to determine the effect of these discharges. The specific activities of 14C found in these samples indicate that the uptake and bioaccumulation of 14C is dependent on the type of organism and its feeding behavior. Measured 14C concentrations in mussels (Mytilus edulis) were higher than those in winkles (Littorina littorea), which were greater than those found in seaweed (Fucus spp.); maximum observed activities were ca. 7, 5 and 3.5 times the accepted current ambient level of 260 Bq kg−1 C, respectively. Annual Nori (Porphyra umbilicalis) samples were analyzed for their 137Cs, 241Am and 14C contents; both the 137Cs and 241Am results correlated well with published Sellafield discharge data (r = 0.877 and 0.918, respectively), whereas there was no significant correlation between measured 14C activities and the discharge record, indicating increased complexity in the chemical and biological behavior of 14C or some discrepancy in the estimated discharge records.