Transfer factor of 137Cs and 90Sr to various crops in semi-arid environment

Abstract

This study focuses on evaluating the transfer factor (Fv) of 137Cs and 90Sr from two basic soil types in the country, i.e. Aridisol and Inceptisol, to 18 common crops belong to six groups, i.e. cereals, leafy, non-leafy vegetables, tubers, leguminous fodder and leguminous vegetables. In addition, the variation of Fvs of 137Cs and 90Sr with crop components, growth stages of plants and the influence of mineral fertilisation were investigated. The experiments were performed in an open field and the results were expressed as geometric means.The data revealed that Fvs of both radionuclides were higher in Aridisol than Inceptisol for all crops by about 1.03–4.86 fold. Fvs of 90Sr were more enhanced than those of 137Cs by one or two orders of magnitude despite plant group and soil type, e.g. Fvs ranged 0.12–5.2 for 90Sr and 0.0035–0.26 for 137Cs in the vegetative portion of the crops.Among the six crop groups investigated, cereals gave the lowest Fvs for both radionuclides, which is compatible with the data reported worldwide. The average Fvs observed in cereal grains reached 0.001 for 137Cs and 0.017 for 90Sr, in Inceptisol. However, Jew-mallow (one of the major leafy vegetables in the country that is consumed throughout the year) reflected the highest Fvs for 137Cs and 90Sr, i.e. 0.11 and 2.44 in Inceptisol, respectively. Comparing Fvs of the radionuclides through the growing stages of the plants indicated enhanced values at the mid-season than harvest as a consequence of the decrease of the physiological activity of the plants towards maturation and dilution made by the increase of plant biomass; e.g. Fvs dropped to about 3.0 fold for 137Cs and 2.2 for 90Sr, in Aridisol. Mineral fertilisation of soil (for four crops, i.e. sorghum, barley, spinach and alfalfa) reduced Fvs for both radionuclides to an extent of 30% probably because of the competing action of their stable nutrient analogues NH4+, K+ or Ca2+ or because of growth dilution.The data presented herein would form a baseline when decision of land-investment or phytoremediation is the preferable countermeasure for the management of 137Cs and 90Sr-contaminated soil in semi-arid environment.