Influence of releases of (129)I and (137)Cs from European reprocessing facilities in Fucus vesiculosus and seawater from the Kattegat and Skagerrak areas.

(129)I is a very long-lived radionuclide (T1/2=15.7×10(6) years) that is present in the environment because of natural and anthropogenic sources. Compared to the pre-nuclear era, large amounts of (129)I have been released to the marine environment, especially as liquid and gaseous discharges from two European reprocessing facilities located at Sellafield (England) and La Hague (France). The marine environment, i.e., the oceans, is the major source of iodine. Brown seaweed accumulates iodine at high levels up to 1.0% of dry weigh, and therefore they are ideal bioindicators for studying levels of (129)I. In this work, (129)I concentrations have been determined in seaweed Fucus vesiculosus and seawater collected in the Kattegat and Skagerrak areas in July 2007. The resulting data were evaluated in terms of (129)I concentrations and (129)I/(137)Cs ratios. (129)I concentrations were found to be in the order of (44-575)×10(9) atoms g(-1) in seaweed and (5.4-51)×10(9) atoms g(-1) in seawater, with an enhancement in the Skagerrak area in comparison to the Kattegat area. Iodine-129 concentrations in both seaweed and seawater were used to determine the concentration factor of iodine in brown seaweed F. vesiculosus. The high levels of (129)I and (129)I/(137)Cs ratios in the Skagerrak area and their gradually decreasing trend to the Kattegat indicates that the most important contribution to the (129)I inventory in those areas comes from Sellafield and La Hague reprocessing plants.