Distribution and sources of 129I in rivers of the Baltic region

The concentration of I-129 was measured in 54 river waters discharging into the Baltic Sea from Sweden, Finland, Estonia, Latvia, Lithuania, Poland and Germany. Sample collection was performed during a well-bracketed time interval (June-July 1999), thus allowing comparison of the rivers over a wide latitude range without the effect of long temporal spread. Although there is no direct input of anthropogenic I-129 in the watersheds, the concentration of the isotope is about two to three orders of magnitude higher than the expected pre-nuclear era natural values in the rivers of Finland and northern Sweden, and in the rivers of southern Sweden, Lithuania, Estonia, Latvia, Poland and Germany; the I-129 concentration may reach five orders of magnitude higher. Furthermore, there are significant correlations between the I-129 concentration and latitude and/ or distance from the North Sea and between I-129 and Cl. These findings suggest seawater as a main source of I-129 to the fivers through atmospheric transport. Of the many chemical parameters investigated, the pH may account for some of the variability in I-129 concentrations of the rivers. The contribution from nuclear weapon tests and the Chernobyl accident to the riverine I-129 is insignificant compared to the releases from the nuclear fuel reprocessing facilities. The total flux of I-129 by rivers to the Baltic Sea and related basins represents minor amounts of the isotope pool in these marine waters. External radioactivity hazards from I-129 are considered to be negligible in the Baltic region. However, as the main I-129 intake to the human body is likely through water, due to the large amount of daily water consumption, more concern should be given to internal radioactivity hazard that may be associated with the isotope's localized elevated concentration in the human organs. (c) 2006 Elsevier Ltd. All rights reserved.