Iodine-129 time series in Danish, Norwegian and northwest Greenland coast and the Baltic Sea by seaweed

The concentrations of I-129 and I-127 were determined in archived time seri es 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 the I-129 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. The I- 129/Tc-99 ratio is applied to estimate the origin of and transit times of I -129. Transit times of I-129 are estimated to be 1-2 years from La Hague to Klint and Utsira and 9-14 years to NW Greenland. Transfer factors of I-129 are calculated to be 54 yr m(-3) from La Hague to Klint, 60 yr m(-3) to Ut sira and 1.2 yr m(-3) to NW Greenland. Based on the estimated transit times , transfer factors and annual discharge data of radionuclides from the repr ocessing facilities, the variations of I-129 concentrations and I-129/Tc-99 and I-129/Cs-137 ratios are modelled. Except I-129/Cs-137, others are in a good agreement between the modelled and measured values. (C) 2000 Academic Press.