Citizen's Guide
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What Is Phytoremediation?
Phytoremediation uses plants to clean up contaminated
environments. Plants can help clean up many types of
contaminants including metals, pesticides, explosives,
and oil. However, they work best where contaminant
levels are low because high concentrations may limit
plant growth and take too long to clean up. Plants
also help prevent wind, rain, and groundwater flow
from carrying contaminants away from the site to
surrounding areas or deeper underground.
How Does It Work?
Certain plants are able to remove or break down
harmful chemicals from the ground when their roots
take in water and nutrients from the contaminated soil,
sediment, or groundwater. Plants can help clean up
contaminants as deep as their roots can reach using
natural processes to:
• Store the contaminants in the roots, stems, or
leaves.
• Convert them to less harmful chemicals within
the plant or, more commonly, the root zone.
• Convert them to vapors, which are released into
the air.
• Sorb (stick) contaminants onto their roots where
very small organisms called "microbes" (such
vapors
tree roots take
in water and
contamination
from the ground
contaminated
soil
water
table
water enters tree
where contamination
is cleaned up
as bacteria) that live in the soil break down the
sorbed contaminants to less harmful chemicals.
(See A Citizen's Guide to Bioremediation [EPA
542-F-12-003].)
Phytoremediation often is used to slow the movement
of contaminated groundwater. Trees act like a pump,
drawing the groundwater up through their roots to keep
it from moving. This method of phytoremediation is
called "hydraulic control." It reduces the movement of
contaminated groundwater toward clean areas offsite.
Constructed wetlands are another form of
phytoremediation. A wetland may be created at a site to
treat acid mine drainage that flows through it or as a final
treatment step for water discharged from other treatment
systems. Water treated with constructed wetlands
generally has very low concentrations of contaminants
that need to be removed before it may be discharged
into a lake or stream. The construction of wetlands may
involve some excavation or regrading of soil at the site
in order for water to flow through it without pumping.
The area is planted with grasses and other vegetation
typical of naturally occurring wetlands in the area.
Certain plants are better at removing contaminants
than others. Plants used for phytoremediation must
be able to tolerate the types and concentrations
of contaminants present. They also must be able
to grow and survive in the local climate. Depth of
contamination is another factor. Small plants like ferns
and grasses have been used where contamination
is shallow. Because tree roots grow deeper, trees
such as poplars and willows are used for hydraulic
control or to clean up deeper soil contamination and
contaminated groundwater.
How Long Will It Take?
Phytoremediation may take several years to clean up
a site. The cleanup time will depend on several factors.
For example, phytoremediation will take longer where:
• Contaminant concentrations are high.
• The contaminated area is large or deep.
• Plants that have a long growing time are used.
• The growing season is short.
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These factors vary from site to site. Plants may have to be replaced if they are
damaged by extreme weather, pests, or animals. This also will add time to the
cleanup.
Is Phytoremediation Safe?
Phytoremediation is a low-risk and attractive cleanup method. Fences and
other barriers are constructed to keep wildlife from feeding on contaminated
plants. In certain instances, plants may release chemical vapors into the air
in a process called "phytovolatilization." When this occurs, workers sample
the air to make sure the plants are not releasing harmful amounts of vapors.
How Might It Affect Me?
Phytoremediation cleanups cause little disruption to the site or surrounding
community. Initial work may involve grading ortilling of the soil with earth-moving
equipment, and backhoes may be needed to plant trees and large shrubs.
Residents and businesses near the site may hear equipment noise or detect
an odor if fertilizer is added to the soil. Any airborne dust can be minimized by
watering down the soil.
Plants used for phytoremediation can make a site more attractive. The use
of native plants is encouraged since they are better adapted to the area's
conditions and less likely to attract nuisance animals or pests.
Why Use Phytoremediation?
EPA uses phytoremediation for many reasons. It takes advantage of natural plant
processes and requires less equipment and labor than other methods since
plants do most of the work. Also, the site can be cleaned up without digging
up and hauling soil or pumping groundwater, which saves energy. Trees
and smaller plants used
in phytoremediation help
control soil erosion, make
a site more attractive,
reduce noise, and improve
surrounding air quality.
Phytoremediation has
been successfully used
at many sites, including
at least 10 Superfund
sites across the country.
Poplar trees at a phytoremediation site.
Example
Phytoremediation is being
used to clean up contami-
nated groundwater near a
former disposal area at the
Aberdeen Proving Ground
in Maryland. This area was
used for disposal and burning
of industrial and warfare
chemicals from 1940 through
the 1970s. Chemicals used
as industrial degreasers and
solvents were found to be
a particular problem in the
groundwater.
In the spring of 1996, 183
poplar trees were planted
in a one-acre area. The
trees draw in contaminated
groundwater and break down
contaminants in the root zone.
The groundwater levels near
the trees show that they are
keeping the plume of contami-
nants from moving to clean
areas. EPA estimates that
within 30 years of the start
of cleanup, the contaminants
in groundwater at the site
may be reduced by up to 85
percent.
For More Information
For more information on this
and other technologies in the
Citizen's Guide Series, contact:
U.S. EPA
Technology Innovation &
Field Services Division
Technology Assessment Branch
(703)603-9910
Or visit:
www.cluin.org/phyto
NOTE: This fact sheet is intended solely as general information to the public. It is not intended, nor can it be relied upon, to create any
rights enforceable by any party in litigation with the United States, or to endorse the use of products or services provided by specific
vendors. The Agency also reserves the right to change this fact sheet at any time without public notice.
United States
Environmental Protection
Agency
Office of Solid Waste and
Emergency Response
(5102G)
EPA 542-F-12-016
September 2012
www.epa.gov/superfund/sites
www.cluin.org
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