Conference Paper The potential bioavailability of Pu in Japanese rice paddy soils

Ni, Youyi  ,  Men, Wu  ,  Zheng, Jian  ,  Tagami, Keiko  ,  Uchida, Shigeo

Plutonium in the environment has caused public concern due to its toxicity and radioactivity. The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident once more highlighted the necessity to study the transfer of Pu in the biosphere for the purpose of radiological assessment. In this study, we employed available transfer factor (ATF) for the evaluation of bioavailability of Pu in rice paddy soils to rice in Japan. The ATF of Pu is defined as the ratio between Pu concentration in rice and the bioavailable Pu concentration in the corresponding paddy soils. We assumed that the bioavailable fraction of Pu in soil was the sum of water soluble fraction and exchangeable fractions of Pu which were extracted by H2O and 1M NH4OAc, respectively. The Pu in rice paddy soils which is potentially bioavailable ranged from 0.03% to 0.24% and was one order of magnitude lower than the values in upland soils reported previously, indicating the possible influences of soil types and Pu loss from paddy soils during irrigation. The ATF of Pu from paddy soil to rice ranged from 6.65×10-3 to 7.98×10-2, about three orders of magnitude higher than the traditional TF (10-5) due to low bioavailability of Pu. Slight differences were found between ATF values of different sampling sites for rice.

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