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

¹ Institut de Protection et de Sûreté Nucléaire, Laboratoire de Radioécologie Expérimentale, CE Cadarache, BP. 1, 13108 Saint-Paul-lez-Durance cedex, France
² Centre de Pédologie Biologique, UPR 6831 du CNRS associée à l'Université Henri Poincaré-Nancy I, 17 rue Notre-Dame des Pauvres, BP. 5, 54501 Vandœuvre-lès-Nancy cedex, France

Abstract

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 column experiments under close-to-natural conditions, supported by complementary batch experiments. Columns 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 α 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.