TOTAL CESIUM-FIXING POTENTIALS OF ACID ORGANIC SOILS

The persistent absence of immobilisation (fixation) of Chernobyl-deriv ed radioactive caesium in soils of the upland areas of Britain has bee n attributed to their peaty nature and assumed lack of Cs-fixing clay minerals. In the present study of a number of the affected soils the C s-fixing clay mineral illite was found to be present in all cases. How ever, the amount of illite, and passible the total clay fraction, was reduced by hydrogen peroxide pretreatments, which are required to remo ve organic matter prior to mineralogical analysis, unless they were bu ffered at a value close to the natural pH of the soil. Determination o f the total number of potential Cs-fixing sites, using a batch-equilib rium sorption method, was not possible for these acid organic soils, d ue to tire occurrence of edge-interlayer trapping. To overcome this a new sequential sorption method was devised. Tire total number of poten tial Cs-fixing sites in the soils studied was found to exceed those pr esent in lowland mineral soils. This may be due to a greater proportio n of clay interlayer regions being in the expanded slate in rite organ ic soils compared to the mineral soils. It is noted, however, that alt hough a soil may have the potential to fix Cs ions, conditions necessa ry for the realisation of this potential may not occur in the field.