THE USE OF SAPROPELS AS AMENDMENTS IN RADIOCESIUM AND RADIOSTRONTIUM CONTAMINATED SOILS

Two issues are addressed in this paper: the solid/liquid distribution behaviour of radiocaesium (Cs-137 and Cs-134) and radiostrontium (Sr-9 0) in sapropels, and the potential effectiveness of sapropels as amend ments to remediate soils contaminated with these radionuclides. It is shown that the solid:liquid partitioning of radiocaesium and radiostro ntium in sapropels is governed by the same processes as in soils. Expe rimental K-D values measured in a representative solution vary between 300 and 5000 dm(3) kg-l for radiocaesium and between 15 and 50 dm(3) kg(-1) for radiostrontium. These K-D values can be interpreted quantit atively on the basis of the main factors which govern the solid/liquid partitioning of these radionuclides. This quantitative approach also allows predictions to be made on the potential effectiveness of saprop el amendments in contaminated soils. These predictions agree very well with experimental results from simple laboratory experiments aimed at investigating the amendment effect. Addition of 1-4 wt.% doses of 2 s apropel samples with different radiocaesium retention characteristics had no significant effect on the radiocaesium distribution coefficient in sandy soils. It is therefore expected that the addition of such sa propels will not result in a decrease of the radiocaesium soil-to-plan t transfer, at least not from the point of view of the increase of the radiocaesium retention in the amended soil. Addition of 1-4 wt.% dose s of a high CEC sapropel to low CEC sandy soils increased the radiostr ontium distribution coefficient up to 3.5 times. It can thus be expect ed that addition of such high CEC sapropel will increase the radiostro ntium retention in the amended soil, and thus decrease the radiostront ium soil-to-plant transfer. (C) 1998 Elsevier Science Ltd. All rights reserved.