Am-241 remobilization in a calcareous soil under simplified rhizospheric conditions studied by column experiments

The effects of simplified rhizospheric conditions on the leaching of 241Am from a calcareous soil, freshly contaminated, were investigated in batch and column experiments. Glucose and/or citrate were used as artificial exudate solutions at concentrations ranging from 10−4 to 10−2 mol dm−3. Am desorption, expressed in terms of distribution coefficients, varied from Kd > 104 dm3 kg−1 corresponding to a majority of experimental conditions, to Kd ≤ 102 dm3 kg−1 when citrate combined or not with glucose was used at ≥10−2 mol dm−3. Soil columns revealed successive steady states coupled with transitory episodes, the latter represented up to 90% of the total Am release. 241Am fractions with different behaviours were thus highlighted in columns whereas batch only accounted for highest Am mobile fractions. The implications of the different processes are discussed in terms of modelling approach and risk assessment.