Towards a more comprehensive modelling of the behaviour of transuranic elements in agricultural soils: Experimental procedure for the study of the sorption/desorption parameters and speciation of transuranic actinides in the rhizosphere.

T. Perrier, A. Martin-Garin, C. Leyval and C. Mustin Actes du congrès ECORAD, 3-7 sept 2001, Aix en Provence, France Radioprotection - Colloques, volume 37, C1-303 / C1-308.

The present paper describes the experimental on-going program on the biogeochemical behaviour of americium and neptunium in the rhizosphere of agricultural soils. Investigation is made by columms experiments under close-to-natural conditions, supported by complementary batch experiments. Columms filled with 2mm-sieved soil, contaminated with 241Am or 237Np, are leached by soil solutions of varying compositions including citric acid and/or glucose. The outlet solution is analyzed (pH, Eh, conductivity, major ions, low molecular weight organic acids, radionuclides) and ultrafiltration is used to determine the relation between particle size and alpha activity. The objective of the study is to ascertain quantitative information on the effects of root exudates, of the physico-chemical parameters of the soil solution as well as the potential role of microorganisms, on the sorption/desorption processes and the speciation in solution 241Am and 237Np.