Radiocaesium and radiostrontium uptake by turnips and broad beans via leafand root absorption

One of the immediate consequences of massive radioisotope release into the atmosphere is contamination of the biosphere. This contamination can affect plants either by direct deposition onto the leaves, or by contaminating th e soil followed by absorption by the roots. Knowledge of the efficacy of th e two routes of radionuclide incorporation into the food chain is fundament al to understanding the mechanisms by which radioactive contamination reach es man. The present work analyzes the incorporation of Cs-134 and Sr-85 via root and leaf uptake into the parts consumed by man, for two very differen t crops: turnip (Brassica napus) and broad bean (Vicia faba). The root upta ke studies consider the available soil fraction for these two radionuclides , and indicate greater availability for Sr-85 than for Cs-134 which is fixe d rapidly in the soil. For the study of leaf uptake, leaves were contaminat ed at three different stages of plant growth; the results indicate an inver se dependence of the transfer coefficients on the time elapsed from the mom ent of the contamination to harvesting of the edible parts. (C) 1999 Elsevi er Science Ltd. All rights reserved.