137Cs, 60Co and 40K uptake by lettuce plants in two distributions of soil contamination.

(137)Cs and (60)Co, two of the radionuclides more representative of discharges from nuclear facilities, are of interest for radiological protections because of their great mobility in biosphere and affinity with biological systems. The aim of the present work is the investigation of the possible influence of the vertical distribution of (137)Cs and (60)Co in soil upon their uptake by lettuce as function of plant's growth. An experiment ad hoc has been carried out in field conditions. The results show that (i) the transfer of (137)Cs and (60)Co from soil to lettuce is independent by their distribution in soil, (ii) the soil-plant transfer factors of (137)Cs and (60)Co show a similar trend vs. growth stage, (iii) the (40)K transfer factor trend is different from those of anthropogenic radionuclides, and (iv) (137)Cs and (60)Co specific activities are about 1Bq/kg, in the mature vegetable with soil activity from 9 to 21kBq/m(2).