Analysis of factors involved in absorption of radioactive caesium for processing tomatoes

In the summer of 2011, we grew processing tomatoes in 14 experimental fields that differed in soil radioactive caesium concentration, and we investigated both the radioactive caesium transfer factor (TF=fruit radioactive caesium concentration, Bq/kg fresh-weight/soil radioactive caesium concentration, Bq/kg dry-weight) for the tomatoes and the soil factors involved in absorption. The TF was different for each field(range, 0.00031 - 0.0072). The radioactive caesium concentration in the fruit correlated positively with the exchangeable radioactive caesium concentration in the soil (r=0.77, p<0.01), and the TF varied inversely with the exchangeable potassium concentration in the soil (ρ=-0.65, p<0.05). Multiple regression analysis showed that 73% of the variation of radioactive caesium concentration in the fruit arose from variations in the exchangeable radioactive caesium and potassium concentrations in the soil. Thus, the soil concentration of both exchangeable radioactive caesium and exchangeable potassium were major factors involved in the absorption of radioactive caesium by tomato plants. In addition, the findings suggest that potassium fertilizers could inhibit the absorption of radioactive caesium where the soil concentration of exchangeable potassium is low. (author)