EXPERIMENTAL INVESTIGATION OF PLANT UPTAKE OF CESIUM FROM SOILS AMENDED WITH CLINOPTILOLITE AND CALCIUM-CARBONATE

Radioactive caesium (Cs-137), from the Chernobyl accident of 1986, has unexpectedly remained in a bioavailable form in upland, sheep-grazing soils of Great Britain. As a potential remedial measure, clinoptiloli te was tested in a greenhouse pot experiment for its effectiveness in selectively taking up Cs from two British soils; a lowland loam (Denbi gh 1 brown earth(1)) and an upland peat (Crowdy 2 series(1)). Rye-gras s, (Lolium perenne, Arno variety) that was grown on 10% (by weight) cl inoptilolite-treated soils containing up to 40 mg kg(-1) added Cs, res ulted in grass leaf tissue Cs concentrations below 30 mg Cs kg(-1) gra ss in all cases. Where no clinoptilolite had been added Cs in grass le af-tissue reached 1860 mg kg(-1) (grown on peat) and 150 mg kg(-1) (gr own on loam) at added Cs levels of 40 mg kg(-1) soil. The addition of calcium carbonate (as ground limestone) to the Cs-treated, clinoptilol ite-free peat soil enhanced the grass concentration of Cs by approxima tely 5 times, but this effect was not observed with the concentration of Cs in grass grown from loam soils with the same treatments. Composi tions of clinoptilolite grains subsequently separated from the experim ental soils ranged from 7.5 to 9.0 mg Cs kg(-1) for the control soils (no added Cs). Soils treated with 40 mg Cs kg(-1) gave Cs concentratio ns in clinoptilolite of 155-170 mg kg(-1) (separated from loam) and 34 7-354 mg kg(-1) (separated from peat).