EFFECT OF SOIL POTASSIUM AND CALCIUM ON CESIUM AND STRONTIUM UPTAKE BY PLANT-ROOTS

Caesium-134 and Sr-85 root uptake was studied in lettuce plants growin g in two contaminated soils with contrasting properties. sandy-loam ve rsus sandy texture, each with 1.5 and 0.1 cmol kg(-1) of K exchangeabl e forms, and 9.1 and 1.6 cmol kg(-1) of Ca exchangeable forms, respect ively. The soil was contaminated by aerosols representative of a nucle ar power plant accidental release at far-field conditions. The percent age of the total deposition absorbed by mature plants was always very low. 0.04% and 0.28% for Cs-134 and, 1.33% and 5.17% for Sr-85 in sand y-loam and sandy soil, respectively. In plants, Cs-134 and Sr-85, radi onuclide activity concentrations decreased over time. The transfer fac tors were higher in the sandy soil. Greater K selectivity than Cs-134 was always observed, although the selectivity of K was higher in the s andy soil which had a lower K concentration. In the sandy-loam soil wh ich had a higher Ca concentration , selectivity of Sr-85 was higher th an that of Ca. These results suggest that radionuclide uptake by roots depended on the availability in the soil of the radionuclides and roo t uptake selectivity, which were both related to the nutrient concentr ation in the soil solution.