129I in the oceans:: origins and applications

The quantity of the long lived (half-life 15.7 million years) radioactive isotope I-129 in the pre-nuclear age ocean was similar to 100 kg. Various nuclear related activities, including weapons testing, nuclear fuel reprocessing, Chernobyl and other authorized or non-authorized dumping of radioactive waste have increased the ocean inventory of I-129 by more than one order of magnitude. The most important of these sources are the direct marine discharges from the commercial reprocessing facilities at La Hague (France) and Sellafield (UK) which have discharged similar to 1640 kg in the English Channel, and similar to 720 kg in the Irish Sea, respectively. We discuss how this I-129 can be used as both a 'pathway' and 'transit time' tracer in the North Atlantic and Arctic oceans, as well as a parameter for distinguishing between reprocessed and non-reprocessed nuclear waste in the ocean, and as a proxy for the transport and dilution of other soluble pollutants input to the North Sea. (C) 1999 Elsevier Science B.V. All rights reserved.