Modeling Fallout of Anthropogenic 129I

Despite the relatively well-recognized emission rates of the anthropogenic 129I, there is little knowledge about the temporal fallout patterns and magnitude of fluxes since the start of the atomic era at the early 1940s. We here present measurements of annual 129I concentrations in sediment archives from Sweden and Finland covering the period 1942−2006. The results revealed impression of 129I emissions from the nuclear reprocessing facility at Sellafield and La Hague and a clear Chernobyl fallout enhancement during 1986. In order to estimate relative contributions from the different sources, a numerical model approach was used taking into account the emission rates/estimated fallout, transport pathways, and the sediment system. The model outcomes suggest a relatively dominating marine source of 129I to north Europe compared to direct gaseous releases. A transfer rate of 129I from sea to atmosphere is derived for pertinent sea areas (English Channel, Irish Sea, and North Sea), which is estimated at 0.04 to 0.21 y−1.