Variability in distribution coefficient (kd) of thorium due to size distribution of a given population of soil

Eventual fate of metals and radionuclides released in aquatic environments can be understood by (studying the distribution coefficients (kd). For some radionuclides, kd varies within a range of more than two orders of magnitude. This variation can be explained on the basis of some physical and chemical aspects of the interactions between the dissolved and the particulate phases. During this work impact of soil particle size on the kd value of thorium was studied by carrying out the laboratory based experiment. Soil sample was fractionated in the size range of 25-500 μm by using g control sieve shaker. Various fractions were spiked with Th solution of 10-4 M at pH 4.0. kd values were determined by collecting water samples and measuring the thorium activity separately in both the dissolved (filtered) and the particulate-bound phases. Determination of thorium was done using ICP-OES by measuring the emission lines at different wavelength (401.913 and 283.232 nm)