Soil to rice transfer factors for 226Ra, 228Ra, 210Pb, 40K and 137Cs: a study on rice grown in India

Abstract

India is the second largest producer of rice (Oryza sativa L.) in the world and rice is an essential component of the diet for a majority of the population in India. However, detailed studies aimed at the evaluation of radionuclide transfer factors (Fv) for the rice grown in India are almost non-existent. This paper presents the soil to rice transfer factors for natural (226Ra, 228Ra, 40K, and 210Pb) and artificial (137Cs) radionuclides for rice grown in natural field conditions on the West Coast of India. A rice field was developed very close to the Kaiga nuclear power plant and the water required for this field was drawn from the cooling water discharge canal of the power plant. For a comparative study of the radionuclide transfer factors, rice samples were also collected from the rice fields of nearby villages. The study showed that the 226Ra and 228Ra activity concentrations were below detection levels in different organs of the rice plant. The soil to un-hulled rice grain 40K transfer factor varied in the range of 6.5 × 10−1 to 2.9 with a mean of 0.15 × 101, and of 210Pb varied in the range of <1.2 × 10−2 to 8.1 × 10−1 with a mean of 1.4 × 10−1, and of 137Cs varied in the range of 6.6 × 10−2 to 3.4 × 10−1 with a mean of 2.1 × 10−1. The mean values of un-hulled grain to white rice processing retention factors (Fr) were 0.12 for 40K, 0.03 for 210Pb, and 0.14 for 137Cs. Using these processing retention factors, the soil to white rice transfer factors were estimated and these were found to have mean values of 1.8 × 10−1, 4.2 × 10−3, and 3.0 × 10−2 for 40K, 210Pb, and 137Cs, respectively. The study has shown that the transfer of 40K was higher for above the ground organs than for the root, but 210Pb and 137Cs were retained in the root and their transfer to above the ground organs of the rice plant is significantly lower.