Potential for phytoremediation of a soil contaminated with radiocesium
was investigated in three phases: (1) hydroponic screening for plant
species capable of accumulating elevated levels of cesium in shoots, (
2) investigation of several amendments for their potential to increase
the bioavailability of Cs-137 in the contaminated soil, and (3) bioac
cumulation of radiocesium in shoots of plants grown in Cs-137-contamin
ated soil. The bioaccumulation ratio for Cs in shoots of hydroponicall
y grown plants ranged between 38 and 165. From solution, dicot species
accumulated 2- to 4-fold more cesium in shoots than grasses. In studi
es investigating the bioavailability of Cs-137 in aged contaminated so
il, ammonium salts were found to be the most effective desorbing agent
s, releasing approximately 25% of the Cs-137. The extent of Cs-137 des
orption from the soil increased with ammonium concentration up to 0.2
M. In a pot study conducted in a greenhouse, there was significant spe
cies-dependent variability in the ability to accumulate Cs-137 in the
shoot from contaminated soil. The ability to accumulate Cs-137 from th
e soil increased in the order: reed canarygrass (Phalaris arundinacea)
< Indian mustard (Brassica juncea) < tepary bean (Phaseolus acutifoli
us) < cabbage (B. oleracea var. capitata). It was also found that addi
tion of NH4NO3 solution to the soil elicited a two-to twelve-fold incr
ease in Cs-137 accumulation in the shoot. The greatest amount of Cs-13
7 (40 Bq g(-1) dw) was removed in shoots of cabbage grown in contamina
ted soil amended with 80 mmols NH4NO3 kg(-1) soil. Bioaccumulation rat
ios of 2-3 were obtained with the best performing plant species. These
values are significantly greater than those previously reported in th
e literature (usually < 0.1) for plants grown on aged contaminated soi
l. These results indicate that careful species selection along with am
endments that increase the bioavailability of Cs-137 in the soil could
greatly enhance the prospects for the use of plants to remediate Cs-1
37-contaminated soils.