Influence d'acides organiques sur la désorption de l'américium 241 et du neptunium 237 à partird'un sol cultivé acide

Abstract

Effect of organic acids on 241 americium and 237 neptunium desorption from an acidic cultivated soil.Naturally occurring organic substances have been recognised as one important factor affecting the behaviour in the environment of transuranic actinides. This experimental study aims at evaluating if some naturally occurring carboxylic acids (vanillic, citric, lactic, oxalic) would affect ²⁴¹Am or²³⁷Np availability in an acidic agricultural soil. Data show that these acids enhance the desorptionof americium and neptunium from the soil, with a noticeable effect of citric acid. The fraction desorbedis multiplied by more than 10 for 0.1 M citric acid, and by 3 or 4 with other acids, in relation withthe complexation of radionuclides with these acids. The desorption increases with molar concentration ofthe acids because of the decrease of pH in acidified soils, except for oxalic acid. The soil moistureconditions seem to affect the desorption results: the percentage desorbed is approximately 10 times lowerfor batch experiments (saturated conditions) than for centrifugation corresponding to unsaturated soilconditions. These preliminary data are mainly qualitative, but they show that it could be interesting totake into account more realistic physico-chemical conditions when measuring desorption ratios forcultivated soils.