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

Abstract

129I is a very long-lived radionuclide (T1/2 = 15.7 × 106 years) that is present in the environment because of natural and anthropogenic sources. Compared to the pre-nuclear era, large amounts of 129I 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 129I. In this work, 129I 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 129I concentrations and 129I/137Cs ratios. 129I concentrations were found to be in the order of (44–575) × 109 atoms g−1 in seaweed and (5.4–51) × 109 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 129I and 129I/137Cs ratios in the Skagerrak area and their gradually decreasing trend to the Kattegat indicates that the most important contribution to the 129I inventory in those areas comes from Sellafield and La Hague reprocessing plants.