Transfer of 238U, 226Ra and 210Pb from slag-contaminated soils to vegetables under field conditions

The uptake of 238U, 226Ra and 210Pb by beans dwarf bean Modus., kohlrabi brassica oleracea ¨ar. gongylodes., mangold beta ¨ulgaris ¨ar. macrorhiza., lettuce American gathering brown., carrots Rotin, Sperlings’s., celery, and radish from a control soil and from soilrslag mixtures was investigated in field experiments. The observed concentration ratios CR. suggest that 226Ra in the slagrsoil mixtures is less available for root uptake than 226Ra in the control soil. This is especially evident for beans, mangold and carrots, and less conspicuous for lettuce. A similar behaviour was observed for the uptake of 238U by celery and radish, but not in the case of lettuce. In this latter case, the CR was even higher when this vegetable was grown on a coal slag contaminated soil when compared to the pure control soil. It is shown that the root uptake of a natural radionuclide from a slag contaminated soil in excess to that from an uncontaminated soil can be characterized best by defining a fractional concentration ratio CRfr .. In this way, all above results are quantified with respect to the root uptake of the radionuclides from the slag fraction in the soils. Because CRfr is not affected by atmospheric contributions to the plant activity, this quantity can be also used to obtain the root uptake of 210Pb by vegetation which results only from the slag fraction in the soil. By comparing the CRfr-values observed for different radionuclides, it is shown that e.g. the amount of 210Pb root-uptake by lettuce from the slags is similar to that of 238U and 226Ra.