Uptake of cesium-137 and strontium-90 from contaminated soil by three plant species; application to phytoremediation

A field test was conducted to determine the ability of three plant species to extract Cs-137 and Sr-90 from contaminated soil. Redroot pigweed (Amaranthus refroflexus L.), Indian mustard [Brassica juncea (L.) Czern.], and tepary bean (Phaseolus acutifolius A. Gray) were planted in a series of spatially randomized cells in soil that was contaminated in the 1950s and 1960s. We examined the potential for phytoextraction of Sr-90 and Cs-137 by these three species. Concentration ratios (CR) for Cs-137 for redroot pigweed, Indian mustard, and tepary bean were 2.58, 0.46, and 0.17, respectively. For Sr-90 they were substantially higher: 6.5, 8.2, and 15.2, respectively. The greatest accumulation of both radionuclides was obtained with redroot pigweed, even though its CR for Sr-90 was the lowest, because of its relatively large biomass. There was a linear relationship between the Cs-137 concentration in plants and its concentration in soil only for redroot pigweed. Uptake of Sr-90 exhibits no relationship to Sr-90 concentrations in the soil. Estimates of time required for removal of 50% of the two contaminants, assuming two crops of redroot pigweed per year, are 7 yr for Sr-90 and 18 yr for Cs-137.