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A soil profile was sampled in 2002 from a soil in which a depleted uranium (DU) ammunition penetrator was embedded for seven years, since the Bosnian conflict in 1994-1995. The affinity of the uranium for six different geochemical phases within the soil profile was assessed by sequential extraction (based on Tessier et al., 1979). The highest concentrations of uranium were present in the surface layers of the soil, 10.5 ± 0.05 g kg⁻¹ (0-4 cm depth) and 7.3 ± 0.02 g kg⁻¹ (4-10 cm depth), from which the penetrator was removed. Sequential extraction results indicated that the uranium is dominantly extracted by the 'bound to carbonate' extraction, with significant concentrations also recovered using the 'readily exchangeable', 'bound to organic matter' and 'bound to Fe/Mn oxyhydroxides' extraction reagents. The recovered uranium concentrations are considered to be operationally-defined. Isotopic analysis determined that ²³⁸U/²³⁵U ratios ranged from 58-168 compared with a natural value of 138. XPS analysis indicated that uranium at the surface of a DU fragment, sampled from the soil profile, was present in the U(VI) oxidation state, and therefore the weathered DU product at the surface of the fragment is thought to be schoepite.

This thesis describes a study of the distribution and geochemical behaviour of 137Cs, 241Am and 239+24P0u within the floodplain deposits of south west Scotland. These sediments have been contaminated with low level effluent discharged from BNFL's reprocessing plant at Sellafield on the Cumbrian coast. The study establishes that the dominant supply mechanism of anthropogenic radionuclides to the floodplain is via on-shore transfer of contaminated particulate material which has been mathematically modelled. A series of lateral transects across the floodplain has confirmed previous observations of highest concentrations furthest inland, illustrating the relationship between particle size and radionuclide concentration. The inventories observed for 137Cs were of the order of - 106 to 10' Bq m-2 and were somewhat higher than previously published data. The vertical distribution of radionuclides was investigated at Southwick merse and indicated a declining depth of occurrence of maximum radionuclide concentrations with distance inland. The observations from a series of transects, using a variety of sample collection methods permitted the construction of a schematic model of the merse. This model identified three distinct zones within the floodplain and enabled estimation of the total inventory for the coastline of south west Scotland. By these estimates less than 1% of the total environmental inventory of 137Cs discharged from Sellafield has been returned on-shore. Speciation studies on the availability of 13C7 s and 239+240Puin dicate that '37Cs is strongly retained within the residual phase of the sediment and that 239" 240Pu exhibits slightly enhanced availability, being associated with the organics and secondary Fe/Mn mineral phases. Evidence suggests that despite the increased environmental availability of 239+240Pu, both these radionuclides and 131Cs are not generally in a form which is available for plant uptake. Flow desorption studies have indicated that 137Cs is tightly bound to the sediment particles producing a Kp of -105 Ikg-1.