at the University of Washington
What is phytoremediation?
Phytoremediation is the use of plants to clean up pollution in the
environment, especially at hazardous waste sites. Plants can take up and
accumulate toxic metals in their leaves where they can be disposed of easily.
Organic pollutants can be taken up by plants and degraded by plant metabolic
activities. The action of bacteria associated with plant roots may be useful in
the control of pollutants.
Research into phytoremediation has intensified since the early 1990s. Studies
at the University of Washington have led the way in understanding plant
activities against important toxic compounds such as trichloroethylene (number
one on the Superfund list of prevalent groundwater pollutants) and carbon
tetrachloride. Recently we have begun work in the use of plants to destroy
toxic compounds in munitions wastes. We continue to study the mechanisms that
are responsible for pollutant degradation by plants and to develop ways to
increase the usefulness of plants for phytoremediation.
Phytoremediation has been applied to or proposed for cleanup of many types of
hazardous wastes, including toxic metals and man-made organic compounds.
- Certain plants can take up large amounts of some toxic heavy
metals from the soil. For example, some trees adapted to growth on serpentine
soils in the South Pacific, which are naturally high in nickel, take up the
metal and concentrate it in their tissues, so much that the sap of the trees
is a bright blue.
- This phenomenon has inspired scientists and engineers to propose to
develop plants that can "hyperaccumulate" heavy metals in their
above-ground tissues so that, by harvesting them, the metals can be
economically removed in an ecologically friendly manner.
- The most important and widespread of groundwater pollutants are the
chlorinated hydrocarbons, such as trichloroethylene. Plants can take up
these carcinogens and break them down to harmless products such as chloride and
carbon dioxide. Pioneering work in the UW phytoremediation labs has
demonstrated biochemical pathways for plant transformations of
trichloroethylene and carbon tetrachloride. We are also developing transgenic
plants for the enhanced breakdown of chlorinated hydrocarbons.
- Another class of soluble compounds are some of the chemicals found in
munitions, especially triazines such as RDX. We are also engineering
plants to degrade these dangerous pollutants.
Insoluble Compounds (hydrophobic)
- Less soluble organic pollutants include polyaromatic hydrocarbons
(PAHs) and polychlorinated biphenyls, as well as the munition compound,
TNT. Plants have a limited capability to take up these pollutants, but
bacteria associated with their roots play a role in the degradation of many
of these chemicals.
Research at the UW
Fate of organic pollutants in plants
Transgenic plants for phytoremediation
Plants to degrade halogenated hydrocarbons:
- Carbon tetrachloride
Plants to degrade the energetic compounds in munitions:
Everything needed for cutting-edge research in phytoremediation: Gas
chromatographs, HPLCs and instruments for tracer work in the
instrument room, a tissue culture room with sterile hoods for propagation,
a plant growth room, and unique field test bed facilities.
Doty, Sharon L., et al. Enhanced
Phytoremediation of Volatile Environmental Pollutants With Transgenic
Trees. (2007) PNAS. 104(43) 16816-16821
In the News
Links for more information about Phytoremediation