Anthropogenic 14C as a tracer in western U.K. coastal waters

14C is a powerful tracer of partitioning and flux within the global carbon cycle. The research described here focuses on characterising and understanding the distribution of 14C in the coastal marine environment of the U.K. where two of the known major sources are:- the BNFL nuclear fuel reprocessing plant at Sellafield in Cumbria, where low-level effluents are discharged under authorization into the Eastern Irish Sea and the Amersham International radiochemical plant in Cardiff where waste from the production of radiotracers is released under licence into Cardiff Bay and ultimately into the Bristol Channel. There are four reservoirs for carbon in the marine environment - the dissolved inorganic and organic (DIC and DOC) and the particulate inorganic and organic (PIC and POC) fractions. The DIC fraction, which is frequently used in tracer studies, has demonstrated the incorporation of 14C from anthropogenic sources in both the Bristol Channel and the eastern Irish Sea, with the measured activities reaching four times and twice the current ambient level respectively. Investigation of the 14C concentrations present in the water column, in conjunction with 137Cs analysis, has indicated a similarity in the distribution pattern of the two nuclides allowing the modification of mathematical models, validated using 137Cs, to describe the environmental transfer of 14C within the marine system. In addition, accelerator mass spectrometry (AMS) has been used to assist in defining the partitioning and exchange of excess 14C between the biogeochemical phases present in the water column. (Author)