Distribution, Sources and Environmental Pathways of Radioactive 129I in Fresh and Saline Water in the Baltic Region
Sammanfattning: This thesis deals with distribution, sources and pathways of radioactive 129I (T1/2=15.6 My) in 54 rivers covering the Baltic region, precipitation (rain and snow) from southern, central and northern Sweden, and saline water from three depth profiles in the Baltic Sea and a surface water transect from the Baltic to the Kattegat. Iodine was chemically extracted from the water samples and the 129I concentrations were measured with Accelerator Mass Spectrometry (AMS). The results show that: 1) 129I concentrations are 2 to 5 orders of magnitude higher than pre-nuclear era natural level in all the studied waters, 2) 129I concentrations in the rivers and precipitation as well as in saline waters generally decrease with increasing latitude and distance from the North Sea, 3) 129I concentrations in the Baltic Sea increase with depth in the water column, and 4) saline water inflow from the Skagerrak-Kattegat basin represents the main source of 129I to the Baltic Sea. The main pathway of 129I to the Baltic region is via both the atmosphere (precipitation) and the marine currents that have been contaminated by discharges (marine and atmospheric) from the nuclear fuel reprocessing facilities at Sellafield (UK) and La Hague (France). The estimates of the 129I-fluxes suggest that only a minor fraction of the amounts from the precipitation is transported by the rivers to the sea and that the watershed retains at least temporarily, most of the isotope concentration. The results of this study also show that, 129I does not represent a source of radiation hazards at present concentration levels. The isotope can, however, be used as a valuable environmental tracer.
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