Volume 40, May 2005ECORAD 2004
|Page(s)||S269 - S276|
|Published online||17 June 2005|
Long-lived radionuclides in the environment: On the radioecology of Iodine-129
Zentrum für Strahlenschutz und Radioökologie (ZSR), Universität Hannover, Herrenhäuser Str. 2, 30419 Hannover, Germany
2 Paul Scherrer Institut (PSI), c/o Institut für Teilchenphysik, ETH Hönggerberg, 8093 Zürich, Switzerland
3 Labor für Radio- und Umweltchemie, Universität Bern, Switzerland
4 Scottish Universities Environmental Research Centre, Scottish Enterprise Technology Park, East Kilbride G75 0QF, UK
The environmental abundances of 129I and 127I in Lower Saxony, Germany, and their pathways to animals and man were investigated. The iodine isotopes are in severe disequilibrium in the different environmental compartments. Today, the environmental isotope ratios range from 10-6 to 10-10. The highest ratios were found in North Sea water, the lowest in deep soil samples and ground water. A differentiation by about a factor of ten between the iodine isotopes was observed for different air-borne iodine species. Time series for iodine in precipitation show a decade-long increase of 129I fallout until the 1990ties and an ongoing constant input of 129I with deposition densities of ~ 15 mBq m-2 per year. In surface waters, a dilution of the fall-out iodine takes place by stable iodine which is just weakly adsorbed in the soils. The isotope ratios in soils and ground waters demonstrate a high mobility and an accumulation of 129I in the water unsaturated soil zones and an efficient migration into water saturated soil layers and ground water. The transfer into the food chain is ruled by the complex situation in the water-soil system. Given the environmental 129I abundances, the relatively low 129I/127I ratios in human thyroid glands (2 × 10-9 - 3 × 10-8) can only be explained by additional iodine sources with low ratios in the diet.
© EDP Sciences, 2005
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