Effect of soil potassium and calcium on caesium and strontium uptake by plant roots

Caesium-134 and 85Sr root uptake was studied in lettuce plants growing in two contaminated soils with contrasting properties: sandy-loam versus sandy texture, each with 1.5 and 0.1 cmol kg−1 of K exchangeable forms, and 9.1 and 1.6 cmolkg−1 of Ca exchangeable forms, respectively. The soil was contaminated by aerosols representative of a nuclear power plant accidental release at far-field conditions. The percentage of the total deposition absorbed by mature plants was always very low: 0.04% and 0.28% for 134Cs and, 1.33% and 5.17% for 85Sr in sandy-loam and sandy soil, respectively. In plants, 134Cs and 85Sr radionuclide activity concentrations decreased over time. The transfer factors were higher in the sandy soil. Greater K selectivity than 134Cs was always observed, although the selectivity of K was higher in the sandy soil which had a lower K concentration. In the sandy-loam soil which had a higher Ca concentration, selectivity of 85Sr was higher than that of Ca. These results suggest that radionuclide uptake by roots depended on the availability in the soil of the radionuclides and root uptake selectivity, which were both related to the nutrient concentration in the soil solution.