Publication Abstract

Incorporation of tritium (³H) by aquatic organisms and sediment in the Severn estuary/Bristol Channel (UK)

D. McCubbin, K.S. Leonard, T.A. Bailey and P. Tossell

Discharges of tritium (³H) into the Severn estuary/Bristol Channel (UK) arise from the authorised release of wastes from nuclear power plants at Hinkley Point and Berkley/Oldbury, and from the Nycomed-Amersham radiopharmaceutical plant, via the sewer system, at Cardiff. ³H concentrations in demersal fish and other benthic organisms in the vicinity of the Cardiff Eastern sewer outfall are significantly elevated compared to those observed around other UK nuclear establishments. Concentrations in filtered seawater were approximately 10 Bq/kg whilst levels in surface sediment, seaweed (Fucus Vesiculosis) and mussels (Mytilus edulis)/flounder (Platichthys flesus) were in the order of 6 x 10² Bq/kg, 2 x 10³ Bq/kg, and 10⁵ Bq/kg (dry weight), respectively. Almost all the ³H found in sediment and biota was organically bound tritium (OBT). The relatively high bioaccumulation is due to the presence of bioavailable organic ³H labelled compounds in the radiopharmaceutical waste. It is suggested that bioaccumulation of ³H by benthic organisms and demersal fish occurs via a pathway of bacterial transformation of dissolved ³H labeled organic compounds into particulate organic matter, and up a web of sediment dwelling microbes and meiofauna. Variations in ³H accumulation between individual organisms have been interpreted in terms of their different feeding behaviour. Relatively low concentrations were observed in the herbivorous winkle (Littorina littorea) and the pelagic Sprat (Spratus spratus) compared with other benthic organisms and demersal fish. The elevated ³H concentrations in seafood, due to bioaccumulation of OBT, have low radiological significance.

Reference:

D. McCubbin, K.S. Leonard, T.A. Bailey and P. Tossell, 2001. Incorporation of tritium (³H) by aquatic organisms and sediment in the Severn estuary/Bristol Channel (UK). Marine Pollution Bulletin, 42(10): 852-863