RADIONUCLIDE MOBILITY AND BIOAVAILABILITY IN NORWEGIAN AND SOVIET SOILS

A sequential extraction procedure has been applied to study the speciation of Chernobyl-derived radionuclides (Cs-137 and Sr-90) in soils from Norway, and from Byelorussia and the Chernobyl region in the USSR. Most Cs-137 (> 80%) was strongly associated with soil components, whereas Sr-90 was more mobile, up to 70% being found in the easily extractable fractions. The Sr-90:Cs-137 ratio decreased with the distance from the reactor, reflecting the higher proportion of hot particles deposited in the regions close to the reactor, and the easily extractable fraction of Sr-90 was significantly lower in the soils collected from the Chernobyl area. The distribution of stable Cs and stable Sr in the extraction fractions was similar for the various sites. Therefore, the location-specific differences in the distribution of Sr-90 and, to a lesser extent, Cs-137 arise because of fallout speciation rather than because of local environmental factors.