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Phytoremediation of Radionuclides
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Phytoremediation of Contaminated Soils
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Home
Overview of Radionuclides
Traditional Methods
Plant Species
Soil Phyto-remediation
Rhizofiltration
Disposal
References
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Soil Phytoremediation
Soil-adsorbed radionuclides are usually more difficult to treat than contaminated
surface water or groundwater. The complexity of the soil medium and redistribution
of contaminates within the soil over time have created significant challenges
for effective phytoremediation of radionuclides. For example, cesium-137
adsorbs strongly to clay minerals and this can make the phytoremediation
of fine textured soils more difficult and less successful (Negri and Hinchman
2000). Successful phytoremediation of radionuclides requires knowledge of
how the soil’s physical, chemical and biological characteristics will
affect uptake by plants. Soil texture, nutrient content (especially Ca,
Mg, K and P), and organic matter are important factors in the uptake of
cesium (Negri and Hinchman 2000), although the mechanisms are not well understood. |
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http://www.frtr.gov/matrix2/section4/D01-4-33.gif |
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Phytoremediation of soils contaminated with radioactive
substances can be accomplished by several different methods, depending upon
whether the goal is to extract (phytoextraction), volatize (phytovolatization),
or stabilize (phytostabilization) the pollutants. Physically, radionuclides
are similar to inorganic metals and they are not known to be used for structural
components (i.e. DNA or proteins) or as nutrients by plants. In order for
phytoremediation of radioactive materials to be efficient, plants need the
appropriate transporter proteins to uptake the materials and move them through
the apoplastic and symplastic tissues, where they can be stored or volatized
into the atmosphere. If phytoextraction of radionuclides is implemented,
it is necessary to know where the majority of pollutants accumulate in the
plants (i.e. leaves, stems, roots) and determine a method to harvest the
biomass and dispose of it appropriately. Incineration of biomass and disposal
of ash in a licensed hazardous waste facility is a realistic method to properly
remediate a contaminated site. Phytovolatization depends upon the specific
nature of a radionuclide, since it may not be possible to volatize the element
and potentially hazardous by-products could be created. Currently, tritium
(3-H) is treatable using phytovolatization, since it is reduces the possibility
of bioaccumulation by humans and is 33% less expensive to build the facilities
and 40% cheaper to maintain than traditional methods (Dushenkov 2003). Phytostabilization
attempts to isolate hazardous waste by capping the material and attempting
to intercept water before it can percolate through the soil and leach the
contaminates. A dense cover of vegetation is necessary and grasses are usually
utilized due to their dense, shallow and fibrous root systems. This method
may not be appropriate for most radioactive sites due to the long half-lives
of most radionuclides and the potential for secondary contamination. |
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