The Uptake and Translocation of 99Tc, 133Cs, 237Np, and 238U Into Andropogon Virginicus With Consideration of Plant Life Stage

Abstract

Hydroponic uptake studies were conducted to evaluate the uptake and translocation of ⁹⁹Tc, ¹³³Cs (stable analog for ¹³⁷Cs), ²³⁷Np, and ²³⁸U into established and seedling Andropogon virginicus specimens under controlled laboratory conditions. Plant specimens were grown in analyte-spiked Hoagland nutrient solution for 24 h, 3 d, and 5 d. Translocation to shoots was greatest for ⁹⁹Tc and ¹³³Cs, likely due to their analogous nature to plant nutrients, while ²³⁸U (and ²³⁷Np to a lesser extent) predominantly partitioned to root tissue with less extensive translocation to the shoots. Plant age contributed significantly to differences in concentration ratios for all nuclides in shoot tissues (p ≤ 0.024), with higher concentration ratios for seedling specimens. Additionally, duration of exposure was associated with significant differences in concentration ratios of ¹³³Cs and ⁹⁹Tc for seedlings (p = 0.007 and p = 0.030, respectively) while plant part (root or shoot) was associated with significant differences in concentration ratios of established plants (p < 0.001 for both nuclides). Statistically significant increases in radionuclide uptake in seedling specimens relative to established plants under controlled conditions suggests that, in addition to geochemical factors, plant life stage of wild grasses may also be an important factor influencing radionuclide transport in the natural environment.