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SYER: Symposium Trace species in environmental research

SYER 2: Session II

SYER 2.4: Hauptvortrag

Mittwoch, 12. März 2008, 15:30–16:00, 3C

Iodine-129 in the Environment — •Rolf Michel — Zentrum für Strahlenschutz und Radioökologie, Leibniz Universität Hannover, Germany

The natural environmental abundances of Iodine-129 were globally changed by orders of magnitude due to atmospheric nuclear explosions and by accidental and routine releases from nuclear installations. Today, the environmental I-129/I-127 ratios range from more than 10⁻⁶ to less than 10⁻¹². The situation in Western Europe is reviewed based on investigations of seawater from the English Channel, the Irish Sea, the North Sea, the Baltic Sea and the North-East-Atlantic. In Northern Germany, air-borne species, precipitation, surface and groundwater as well as the complete terrestrial food-chain were investigated. The iodine isotopes are in severe disequilibrium in all the environmental compartments. 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 I-129 fallout until the 1990ties and an ongoing constant input of I-129. 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 I-129 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. In spite of the extreme anthropogenic changes, I-129 is presently not of radiological concern.