Natural and anthropogenic 14C in the UK coastal marine environment

Prior to this study, almost no up-to-date information was available on the ‘background’ level of 14C present in the water and biota of the UK coastal marine environment. The weighted mean 14C activity derived from the lowest activities of dissolved inorganic carbon (DIC) and biota for sites which are remote from potential sources is 247•6±1•0 Bq kg-1 carbon. This is proposed as the best estimate of the natural/weapons testing ‘background’ for 1995 and should be subtracted from the activity derived for any sample to establish the excess due to UK anthropogenic inputs. 14C activities in the DIC component of seawater and a range of marine biota are significantly enhanced above the expected ‘background’ value in the environment around the British Nuclear Fuels plc reprocessing plant at Sellafield, Cumbria, NW England and Amersham International plc, Cardiff, Wales. The enrichments around Sellafield are largely confined to the NE Irish Sea while those at Cardiff are confined to the Severn Estuary. The dose from 14C to the Sellafield seafood-consuming critical group (<4 μSv) for this study, derived using the best estimate baseline 14C values, is in good agreement with other works which produced a value of 3 μSv, also for 1995. There is either variability in the kinetics of response of the biota to changes in discharge or significant differences in the pools from which the biota derive their carbon. Investigation of these factors is of fundamental importance if this area of research is to proceed towards deriving changes in dose due to changes in discharge.