In 1986 anthropogenic radionuclides were released into the atmosphere as a direct result of the nuclear reactor accident at Chernobyl. Radiocaesium deposited on the U.K has undergone a considerable amount of recycling with areas of high plant concentrations being found above soils of high organic matter content. This was contrary to the expected behaviour of radiocaesium as it was expected to fix rapidly to mineral soils and to leach rapidly from organic soils and thus be unavailable to plants and animals. This thesis examines the mobility of radiocaesium in organic rich and mineral soils from selected sites in Scotland using gamma spectroscopy and 210Pb dating in an attempt to correlate the observed behaviour with the soils properties and local topography. Laboratory methods such as adsorption/desorption isotherms are used to examine the sorption of caesium and lead in a selected range of fully characterised soils and clays in order to understand further the environmental behaviour of the radionuclides. As the behaviour of radiocaesium and other radionuclides is of interest this thesis takes both a qualitative and quantitative view of the binding of a range of metal ions to soil humic acid using techniques such as infra-red spectroscopy and potentioraetric titrations. In addition, the influence of clay/humic acid interactions upon caesium sorption are examined. The main findings of this thesis support the observed long term availability of radiocaesium in soils of high organic matter content. Radiocaesium appears to undergo lateral movement in peatlands resulting in the enrichment of layers fed by surface water run-off. Little evidence was found to support the downwards diffusion of radiocaesium in peats. The presence of humic acid in clay/humic acid systems depressed the sorption of caesium and enhanced the desorption of caesium from bentonite and kaolinite. For both sorption and desorption, the presence of humic acid resulted in lower values thus causing caesium to be more mobile
