[en] Technetium-99 is a long-lived radionuclide (T = 2.1 10⁵ years), and as pertechnetate (Tc O₄^-), this element is very mobile in aerated soils. Plants take up Tc as Tc O₄^- and accumulate it in their aerial parts. This work was undertaken to study the evolution of Tc O₄^- into the shoots of a cereal in order to assess the risk associated with the contamination of soils by radionuclides and its consequence on Tc content of man-consumed parts. Winter wheat was grown on a silty loam contaminated at four different rates of ⁹⁹Tc (0, 2.5, 25 and 250 kBq/kg). Wheat growth was measured; the number of suckers per plant and the date of earring were recorded. At grain maturity, the different parts of the plant were collected, dried, mineralized and their Tc content was determined. Results showed that the higher concentration of Tc in the soil (250 kBq/kg) reduced significantly plant growth, caused delay in earring and a significant decrease in grain yield. Total uptake of Tc by the crop represented 37 to 47 pc of the initial amount applied in the soil and the fraction of Tc in leaves reached more than 90 pc of the total Tc taken up by the plant. Tc transfer factors (i.e. concentration ratios) were high and maximal in leaves (285 to 363). They ranged from 8 to 28 in roots, stems and husks but they were lower than 1 for the grain. These results showed that Tc was not accumulated in the edible part of wheat and that the fraction stored in leaves could be a new supply of Tc to future crops if crop residues are incorporated back to the soil

[en] A dual isotope method has been used to study the transfer of ¹³⁷Cs, ^239/240Pu and ²⁴¹Am to sheep following ingestion of contaminated soil. Two soils were used; an alluvial gley contaminated by Sellafield discharges, and an organic soil, artificially contaminated in a lysimeter. Values of the true absorption coefficient of radiocaesium of 0.19 +/- 0.03 and 0.03 +/- 0.01 respectively were obtained for these soils. This implies an availability factor for soil-associated radiocaesium of up to about 20 pc compared to radiocaesium ingested in soluble form. The absorption of plutonium and americium was not significantly different for the two soils tested. Absorption of both plutonium and americium was in the range 10^-5 - 10^-4, with mean values of 7 x 10^-5 and 4 x 10^-5 obtained respectively. These values imply availability factors of around 10 pc, compared to the value of 5 x 10^-4 recommended by ICRP for plutonium ingested in a comparatively available form. These results are compared with estimates of availability made using an in-vitro approach

No abstract available

[en] Two papers (edited on CD-Rom) have been selected (radionuclide kinetics and tracer techniques) for INIS in this conference which three main themes are: biogeochemistry of trace elements (speciation, mobilization and physico-chemical and biological processes, transfer and transport), impacts and pathways of exposure (terrestrial and aquatic ecosystems, transfer to man via the food chain or by direct ingestion and inhalation), evaluation and management of risks (sources, cycles and balances, methods for evaluation of risk, comparing the basis for regulation, choice of objectives and feasibility of treatment)