Sorption-desorption behaviour of caesium in some Western Australian soils

Abstract

Soil caesium-137 derived from past atmospheric nuclear tests is increasingly being used as an indicator of soil erosion and deposition on the basis that fallout 137Cs has been retained by soils, although this assumption has not been thoroughly tested for different soils. The sorption behaviour of some Western Australian soils indicates that Cs is differentially sorbed as a consequence of differences in clay mineralogy. Kaolinitic sandy soils of low exchange capacity sorb Cs in preference to Ca and Na, with the specificity for Cs being higher at lower concentrations of Cs in solution. lllitic and smectitic soils sorbed more Cs than kaolinitic soils and retained more than 50% of sorbed Cs after a series of extractions with salt solutions. Retention by kaolinitic soils was less but, for the concentrations of Cs likely to occur in soils, it seems that most Cs is retained so that it is probable that the 137Cs technique can be used with confidence for the measurement of soil erosion and deposition for many Western Australian soils.