Radionuclides, analysis adsorption

Despite these caveats, many analyses are done on land either because the sample can be stored without changing the concentrations of the analytes it contains or because the apparatus required for the analysis cannot be operated on board a ship. For instance, some radionuclides are measured on land for both reasons. Samples analyzed on land can be spiked immediately with another (artificial) isotope of the same element to fill the adsorption sites on container walls and to serve as an internal standard. The mass spectrometers required for isotope ratio analyses are often too sensitive to vibration and motion for shipboard use. Analytes present at greater than trace levels, or which can be stabilized with some pretreatment, may also be analyzed successfully on shore. 

Hayes, K.E et al.. Application of surface complexation models for radionuclide adsorption Sensitivity analysis of model input parameters, NUREG/CR-5547, US Nuclear Regulatory Commission, Washington DC, 1990, cited after Prikryl, J.D. et al.. Uranium sorption on a alumina Effects of pH and surface area/solution volume ratio, Radiochim. Acta, 66/67, 291, 1994. 

Evaporation is a method for preconcentration used in the analysis of water samples. The enrichment factor is between 10 and 10 This approach however may lead to losses of certain elements due to adsorption on the walls of the vessels. That is why evaporation nowadays is practically used in the preconcentrations of radionuclides from waters since the carriers prevent adsorption (Das et al., 1983 Mizuike, 1983 Toelgyessy and Kyrs, 1989). 

We examine the problem of diffusion in a porous medium using a homogenization analysis (HA). Diffusion problems have important applications in environmental geosciences. We clarily the mechanism of diffusion, convective transport and adsorption in porous media at both the microscale and macroscale levels. Attention is particularly focused on diffusion processes in bentonite, which is an engineered geological barrier to be used to buffer the transport of radionuclides from deep geologic repositories. 

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