The uptake and transfer of caesium-137, strontium-90 and zinc-65 from soil to food crops in tropical environment

The soil to plant transfer factors (TF) of 137Cs, 90Sr and 65Zn were determined for two crops, pearlmillet (Pennisetum typhoides) and sorghum (Sorghum vulgare) under irrigated conditions in greenhouse and in natural conditions of rain in field. The accumulation of 137Cs was almost doubled when the soil contamination level was doubled. Under the field conditions, 137Cs concentration in both pearlmillet and sorghum grains as well as straw was nearly four times more at a higher level of soil contamination (148 kBq/kg soil) compared to that at a lower level of 74 kBq/kg soil. 90Sr absorption by both the crops was nearly 50 to 100 times more compared to 137Cs under identical conditions of crop growth and soil contamination. 65Zn concentration was higher in pearlmillet grains than in straw portions, whereas in sorghum it was otherwise. The TF values for 137Cs decreased nearly ten fold in the second year both under field and pot culture conditions, while those for 90Sr reduced by half and for 65Zn by about five times. Under irrigated conditions in field the transfer factors for 137Cs were nearly four times larger both for pearlmillet and sorghum (1996 experiment) and for 90Sr more than two times, compared to those under rain fed conditions obtained in 1994. (author)