Transfer factor of Sr-90 and Cs-137 to lettuce and winter wheat at different growth stage applications

摘要

The effect of clay soil contamination time on the transfer factors (F(v)s) of Cs-137 and Sr-90 was investigated in four different growth stages of winter wheat and lettuce crops. The experiment was performed in an open field using lysimeters. The F(v)s were the ratio of the activity concentrations of the radionuclides in crops to those in soil, both as dry weight (Bq kg(-1)). Significant difference of log-F(v)s was evaluated using one-way Analysis of Variance (ANOVA). Basically, F(v)s of Sr-90 were higher than those of Cs-137, despite of the application stage or crop' variety. Higher F(v)s for both radionuclides were observed for lettuce in comparison to winter wheat. Fvs of Sr-90 showed comparable trends for both crops with enhanced F(v)s obtained when contamination occurred in early stages, i.e. 1.20 for lettuce and 0.88 and 0.02 for winter wheat, straw and grains, respectively. Despite the fluctuation noted in the pattern of F(v)s for Cs-137, soil contaminated at the second stage gave the highest F(v)s for lettuce and grains, with geometric means of 0.21 and 0.01, respectively. However, wheat-straw showed remarkable increase in F-v for the latest contamination (ripening stage), about 0.06. It could be concluded that soil contamination at early growth stages would represent high radiological risk for the scenarios studied with an exception to Cs-137 in winter wheat-straw which reflected greater hazard at the latest application. (C) 2015 Elsevier Ltd. All rights reserved.