Experimental investigation of plant uptake of caesium 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, clinoptilolite was tested in a greenhouse pot experiment for its effectiveness in selectively taking up Cs from two British soils; a lowland loam (Denbigh 1 brown earth(1)) and an upland peat (Crowdy 2 series(1)). Rye-grass, (Lolium perenne, Arno variety) that was grown on 10% (by weight) clinoptilolite-treated soils containing up to 40 mg kg(-1) added Cs, resulted in grass leaf tissue Cs concentrations below 30 mg Cs kg(-1) grass in all cases. Where no clinoptilolite had been added Cs in grass leaf-tissue reached 1860 mg kg(-1) (grown on peat) and 150 mg kg(-1) (grown on loam) at added Cs levels of 40 mg kg(-1) soil. The addition of calcium carbonate (as ground limestone) to the Cs-treated, clinoptilolite-free peat soil enhanced the grass concentration of Cs by approximately 5 times, but this effect was not observed with the concentration of Cs in grass grown from loam soils with the same treatments. Compositions of clinoptilolite grains subsequently separated from the experimental 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 concentrations in clinoptilolite of 155-170 mg kg(-1) (separated from loam) and 347-354 mg kg(-1) (separated from peat).