Cs-137 and Sr-90 root uptake prediction under close-to-real controlled conditions

Radionuclide soil-to-crop transfer was analysed in large undisturbed soil m onoliths installed in lysimeters under controlled climatic conditions. The soils were representative of large agricultural areas in the European Union : Loamy-sand Orthic Podzol from Belgium, Loamy-sand Fluvisol from France, L oamy Calcic Luvisol from Spain, Silty-loam Orthic Luvisol from Germany, and Sandy-loam Eutric Fluvisol from the UK. On the lysimeters, winter barley w as sown for two consecutive years on artificially contaminated soils simula ting a post-accidental situation, 1 and 2 years after radionuclide depositi on. The amount (Bq m(-2)) of Cs-137 and Sr-90 that accumulated in the crop was higher in the loamy-sand soils, regardless of the total radionuclides ( MBq m(-2)) or available fraction content in the soil. The Orthic Podzol pro duced the highest Cs-137 crop accumulation, and the Loamy-sand Fluvisol the highest Sr-90 accumulation. Concentration ratios (CR) showed similar resul ts, but with higher Sr-90 transfer for the Podzol than for the Loamy-sand F luvisol. The activity concentration of radionuclides in the plants was nega tively correlated with crop yield, indicating that high crop productivity p roduced a general dilution effect in radionuclide concentration activity in plants. The relative radionuclide crop accumulation expressed in Bq m(-2) was predicted from the soil availability parameters, that is the available Cs-137 fraction divided by the distribution coefficient (K-D) and by the K concentration in soil solution, and the available Sr-90 divided by the cati onic exchange capacity (CEC). These predictions could not be obtained when using the CR, as this does not fully account for the crop growing condition s which influence radionuclide uptake by the crop. (C) 1999 Elsevier Scienc e Ltd. All rights reserved.