Chemical and Isotopic Composition of the Organic Matter Sources in the Gulf of Gdansk (Southern Baltic Sea)

The concentrations of129I and127I were determined in archived time series seaweed samples from Klint in the Kattegat, Bornholm in the Baltic Sea, Roskilde Fjord in Zealand of Denmark, Utsira in the western Norwegian coast and NW Greenland by neutron activation analysis. The results indicate that the129I levels in all locations investigated are one to three orders of magnitude higher than the fall-out background and strongly dominated by the discharges from reprocessing facilities at La Hague and Sellafield. The129I/99Tc ratio is applied to estimate the origin of and transit times of129I. Transit times of129I are estimated to be 1-2 years from La Hague to Klint and Utsira and 9-14 years to NW Greenland. Transfer factors of129I are calculated to be 54 yr m-3from La Hague to Klint, 60 yr m-3to Utsira and 1·2 yr m-3to NW Greenland. Based on the estimated transit times, transfer factors and annual discharge data of radionulides from the reprocessing facilities, the variations of129I concentrations and129I/99Tc and129I/137Cs ratios are modelled. Except129I/137Cs, others are in a good agreement between the modelled and measured values.