Some experiments on the decontamination of soils containing strontium 90

The possibility that large areas of the landscape could become contaminated with strontium 90 through fallout or reactor accidents has necessitated studies of means of decontaminating soils containing radio-strontium. In this work three possible methods were investigated: 1) displacement by electrolytes and leaching; 2) physical immobilization using asphalt preparations; and 3) placement at depth.

Of the various electrolytes used, ferric chloride and hydrochloric acid were most effective. The use of the electrolytes followed by leaching with 5 feet of irrigation water displaced up to 90 per cent of the Sr 90 below the surface 6 inches. This, however, was not sufficient decontamination so that the land could be put back into agricultural use. In addition the procedure is very expensive.

By spraying the soil surface with asphalt, it was found that 97 per cent of the Sr 90 could be removed by peeling off the hardened crust. When the crust was cultivated into the soil profile, however, the Sr 90 gradually became available to plants.

In order to investigate the possibility of reducing the uptake of Sr 90 by deep plowing, experiments were conducted in lysimeters in which the isotope was placed in bands at different depths in the soil. When the soil was cropped to barley, a marked reduction of uptake of Sr 90 with depth of placement was observed. In irrigated barley the content of strontium 90 per gram of plant material was reduced tenfold when the depth of placement was increased from 2 inches to 2 feet.