Author
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Entry, James |
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WATRUD, LIDIA - U.S. EPA, CORVALLIS, OR |
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Submitted to: Journal of Water Air and Soil Pollution
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 2/18/1997 Publication Date: N/A Citation: N/A Interpretive Summary: Large areas of land have been contaminated by fission by-products resulting from nuclear bombs, above-ground nuclear testing, nuclear reactor operations and nuclear accidents. Unlike organic pollutants, radionuclides typically are elements which cannot be degraded. Radionuclides, especially **137**Cs and **90**Sr, can accumulate as they move up the food chain. Human exposure may result in detrimental health effects, such as cancers and genetic mutations. The cost to dispose of large liquid volumes of chemicals used to decontaminate soils polluted with radionuclides may be prohibitive; estimates of $200 to $300 billion for radionuclide cleanup in the U.S. alone, are considered conservative. Alamo switchgrass plants were tested for their ability to accumulate **137**Cs and **90**Sr from a contaminated growth medium. Above-ground plant biomass did not differ between plants that were not exposed to these radionuclides (controls) and those that were exposed to growth medium containing **137**Cs or **90**Sr over the course of the experiment. Since Alamos switchgrass accumulated 44% and 36% of the total amount of **90**Sr and **137**Cs, these grass species removed as much as 72% of the **137**Cs and 89% of the **90**Sr. Remediation of radionuclide soils using plants may be a preferable option to presently used methods. Technical Abstract: Cesium-137 (**137Cs) and Strontium-90 (**90Sr) are radionuclides characteristic of nuclear fallout from nuclear weapons testing and nuclear reactor accidents. Alamo switchgrass (Panicum virginatum L.) is a perennial C**4 species native to central North America that produces exceptionally high biomass yields in short periods of time. In three separate experiments, Alamo switchgrass plants were tested for their ability to accumulate **137Cs and **90Sr from a contaminated growth medium. Plants in all three experiments were grown within a greenhouse that was maintained at 22 +/- 2 deg C with a photosynthetic active radiation of 400-700 mu mol m**-2 s**-1 and a 14-16 h photoperiod. Above-ground plant biomass did not differ between plants that were not exposed to these radionuclides (controls) and those that were exposed to growth medium containing **137Cs or **90Sr over the course of the experiment. Plants accumulated 44 and 36% of the total amount of **90Sr and **137Cs added to growth medium after the first 5 harvests. After the first two harvests, the concentration of **137Cs and **90Sr in plant tissue and the amount of **137Cs or **90Sr removed from growth medium declined with each successive harvest. Duration of exposure correlated curvilinearly with accumulation of both **90Sr and **137Cs by plants (r**2 - 0.95 and 0.78, respectively). As concentration of both **137Cs and **90Sr in growth medium increased, plant accumulation of both radionuclides increased and correlated curvilinearly in seedlings (r**2 - 0.83 and 0.89 respectively). |
