Submitted to: Journal of Environmental Quality
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/30/1998
Publication Date: N/A
Citation: Interpretive Summary: Radionuclide contamination of soils poses serious problems to both human health and agriculture in the U.S. Soils have become contaminated with radionuclides as a result of above ground nuclear testing, accidental release or nuclear energy generation. 137Cs is a long-lived (half-life = 30.2 years) by-product of nuclear fission. Although recent contamination of the environment with 137Cs from the testing of nuclear weapons has been drastically reduced, large areas are still polluted with radiocesium. The projected cost of cleaning up these radionuclide-contaminated soils is very high, in excess of 300 billion dollars. Phytoremediation is emerging as an attractive alternative to energy-intensive, high-cost traditional cleaning methods. This new technology employs the use of higher plants capable of accumulating high levels of contaminants in shoots. Following harvesting, the shoot biomass can be disposed of in a final repository after volume reduction (e.g., ashing). In this field study of a 137Cs contaminated site at the Brookhaven National Laboratory, four different plant species were grown to test their relative ability to extract radiocesium from the soil and accumulate it in the shoot. It was found that there were dramatic differences in radiocesium accumulating ability, with the species Amaranthus retroflexus able to accumulate about 40 times more 137Cs than the other plant species. Based on these findings, it should be possible to use Amaranthus retroflexus to clean up this site from radiocesium contamination within 10-15 years.
Technical Abstract: A field study was conducted to investigate the potential for phytoremediation of a 137Cs-contaminated soil by three species. From the contaminated soil, approximately 40-fold more radiocesium was removed by shoots of red root pigweed (Amaranthus retroflexus L.) compared with those of Indian mustard (Brassica juncea (L.) Czern) and tepary bean (Phaseolus acutifolius A. Gray). The greater potential of Amaranthus for 137Cs extraction was associated with both, ability to concentrate radiocesium in shoots and produce high biomass. Addition of a 0.1 M NH4NO3 solution desorbed approximately 15 % of the radiocesium bound to soil particles. Although NH4NO3 increased 137Cs bioavailability in soil it had no effect on 137Cs accumulation in shoots. Our results suggest that most of the 137Cs released from the soil by NH4NO3 application was lost by leaching. Approximately 3 % of the 137Cs was removed from the upper layer (4 inches) of the soil in shoots of the two-month-old Amaranthus plants grown in NH4NO3-free plots. With 2-3 cropping a year and a sustained rate of extraction, phytoremediation of this 137Cs-contaminated soil with Amaranthus appears feasible.