PHYTOREMEDIATION OF A RADIOCESIUM-CONTAMINATED SOIL - EVALUATION OF CESIUM-137 BIOACCUMULATION IN THE SHOOTS OF 3 PLANT-SPECIES

A field study was conducted to investigate the potential of three plan t species for phytoremediation of a Cs-137-contaminated site. Approxim ately 40-fold more Cs-137 was removed from the contaminated soil in sh oots of red root pigweed (Amaranthus retroflexus L.) than in those of Indian mustard [Brassica juncea (L.) Czern] and tepary bean (Phaseolus acutifolius A. Gray), The greater potential for Cs-137 removal from t he soil by A. retroflexus was associated with both high concentration of Cs-137 in shoots and high shoot biomass production. Approximately 3 % of the total Cs-137 was removed from the top 15 cm of the soil (whic h contained most of the soil radiocesium) in shoots of 3-mo-old A, ret roflexus plants. Soil leaching tests conducted with 0.1 and 0.5 M NH4N O3 solutions eluted as much as 15 and 19%, respectively, of the soil C s-137, Addition of NH4NO3 to the soil, however, had no positive effect on Cs-137 accumulation in shoots in any of the species investigated. It is proposed that either NH4NO3 solution quickly percolated through the soil before interacting at specific Cs-137 binding sites or radioc esium mobilized by NH?NO, application moved below the rhizosphere, bec oming unavailable for root uptake. Further research is required to opt imize the phytotransfer of the NH4NO3-mobilized Cs-137. With two cropp ings of A. retroflexus per year and a sustained rate of extraction, ph ytoremediation of this Cs-137-contaminated soil appears feasible in <1 5 yr.