PHYTOTECHNOLOGIES
                                                     FOR SITE  CLEANUP
Fact Sheets on Ecological Revitalization

•   This fact sheet is the fourth in a series of fact
    sheets related to ecological revitalization
    developed by the U.S. Environmental Protection
    Agency (EPA) Technology Innovation and Field
    Services Division (TIFSD).  The information in this
    fact sheet is intended for EPA and state agency
    site managers, consultants, and others interested
    in the ecological revitalization of contaminated
    sites.
•   The first three fact sheets can be found at http://
    cluin.org/ecorevitalization and include: (1)
    "Frequently Asked Questions about Ecological
    Revitalization of Superfund Sites," EPA 542-F-
    06-002; (2) "Revegetation of Landfills and Waste
    Containment Areas," EPA 542-F-06-001; and (3)
    "Ecological Revitalization and Attractive Nuisance
    Issues," EPA 542-F-06-003.
•   Various information sources were used to prepare
    this fact sheet. These and additional information
    resources are listed at the end of the fact sheet.
                                                     Introduction
                                                       Contaminated sites exist throughout the United States and
                                                       elsewhere that require cleanup to protect human health and
                                                       the environment. Phytotechnologies are a set of techniques
                                                       that make use of plants to achieve environmental goals.
                                                       These techniques use plants to extract, degrade, contain, or
                                                       immobilize pollutants in soil, groundwater, surface water,
                                                       and other contaminated media. Phytotechnologies remediate
                                                       contaminants using several different mechanisms dependent
                                                       on the application; Tables 1 and 2 summarize these mecha-
                                                       nisms and applications.
                                                       Some phytotechnology applications could be primary
                                                       methods of cleaning up or stabilizing contamination while
                                                       others will supplement primary remedies. Phytotechnolo-
                                                       gies may potentially (1) clean up moderate to low levels of
                                                       select elemental and organic contaminants over large areas,
                                                       (2) maintain sites by treating residual contamination after
                                                       completion of a cleanup, (3) act as a buffer against potential
                                                       waste releases, (4) aid voluntary cleanup efforts, (5) facili-
                                                       tate nonpoint source pollution control, and (6) offer a more
                                                       active form of monitored natural attenuation (McCutcheon
                                                       and Schnoor 2003).  Table 2 lists potential phytotechnology
                                                       applications and associated mechanisms.
                                                       Phytotechnologies can treat a wide range of contaminants,
                                                       including: organics, such as volatile organic compounds
                                                       (VOC), polycyclic aromatic hydrocarbons (PAH), petro-
                                                       leum hydrocarbons, and munitions constituents; metals;
                                                       and radionuclides—although not all mechanisms are ap-
                                                       plicable to all contaminants or all matrixes.  This fact sheet
^^	    (1) provides information that will help you evaluate whether
phytotechnologies will work at your site, (2) summarizes the applications of phytotechnologies for various contaminants, and
(3) includes links to additional sources of information.

WILL  PHYTOTECHNOLOGIES WORK AT YOUR  SITE?	
As with all remediation strategies, phytotechnologies are site-specific, with applicability and performance that can vary
widely based on parameters such as contamination and soil type, vegetation, and climate. It is best to evaluate a site early in
the cleanup process to determine the possibility of using vegetation to achieve remediation, restoration, and/or  containment
goals. Because high concentrations of some contaminants may be toxic to plants and inhibit their growth, phytotechnologies
are best applied at sites with low to moderate levels of contamination, used in conjunction with other treatment methods, or
used as a final polishing step in site remediation. Finally, phytotechnologies can take significantly longer than other remedial
technologies to achieve site goals because the plants must first establish well-developed roots and biomass to be effective.
Nevertheless, phytotechnologies offer several significant advantages. Table 3 lists some advantages and disadvantages of
applying phytotechnologies.
After reviewing site characteristics to determine if phytotechnologies would be effective at your site, it is important to
select the appropriate phytotechnology mechanism and species. The mechanism and plants must be suitable to  address
contaminants of concern at the site and site characteristics such as soil type and climate.  Ideally, the potential effectiveness
of phytotechnology at a site is tested in a laboratory setting and through pilot field studies before full-scale application.
Laboratory studies can determine if the target contaminant(s) can be removed under ideal conditions.  If  the lab study
Phytotechnologies use plants to extract, degrade,
contain, or immobilize pollutants in soil, groundwater,
surface water, and other contaminated media.

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                                                          TABLE 1
                                         PHYTOTECHNOLOGY MECHANISMS
Mechanism
Phytodegradation
Phytoextraction
Phytohydraulics
Phytosequestration
Phytovolatilization
Rhizodegradation
Description
Ability of plants to take up and break down contaminants within plant
tissues through internal enzymatic activity
Ability of plants to take up contaminants into the plant and sequester
the contaminant within the plant tissue
Ability of plants to take up and transpire water
Ability of plants to sequester certain contaminants into the rhizosphere
through release of phytochemicals, and sequester contaminants on/
into the plant roots and stems through transport proteins and cellular
processes
Ability of plants to take up, translocate, and subsequently volatilize
contaminants in the transpiration stream
Ability of released phytochemicals to enhance microbial biodegrada-
tion of contaminants in the rhizosphere
Cleanup Goal
Remediation by destruc-
tion
Remediation by removal
of plants containing the
contaminant
Containment by control-
ling hydrology
Containment
Remediation by removal
through plants
Remediation by destruc-
tion
Source: Interstate Technical Regulatory Council (ITRC). 2009. Phytotechnology Technical and Regulatory Guidance and Decision Trees, Revised.
                                                         TABLE 2
                                        PHYTOTECHNOLOGY  APPLICATIONS
Application
Constructed Treatment Wetland/
Aquatic Plant Lagoon
Field Crops/ Grass, Forb, Herb, or Fern
Gardens
Landfill Cover
Riparian Buffer
Tree Hydraulic Barrier
Tree/Shrub Plantation
Media
Sediment
Surface Water
Soil
Sediment
Soil
Sediment
Surface Water
Soil
Sediment
Surface Water
Groundwater
Groundwater
Soil
Sediment
Groundwater
Mechanisms
Phytodegradation
Phytoextraction
Phytovolatilization
Rhizodegradation
Phytodegradation
Phytoextraction
Phytovolatilization
Rhizodegradation
Phytoextraction
Phytohydraulics
Phytosequestration
Phytodegradation
Phytoextraction
Phytohydraulics
Phytosequestration
Phytovolatilization
Rhizodegradation
Phytoextraction
Phytohydraulics
Phytosequestration
Phytodegradation
Phytoextraction
Phytovolatilization
Rhizodegradation
Sources: ITRC. 2009. Phytotechnology Technical and Regulatory Guidance and Decision Trees, Revised. McCutcheon, S.C. and J. L. Schnoor. 2003.
Phytoremediation: Transformation and Control of Contaminants. John Wiley & Sons, Inc., Hoboken, New Jersey. ISBN: 0-471-39435-1. 987pp.

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                                                      TABLE 3
                     ADVANTAGES AND DISADVANTAGES FOR PHYTOTECHNOLOGIES
                                                   Advantages
 Substantial cost savings are possible.
 Greater public acceptance may result from use of an environmentally-friendly "green" and low-tech remedial technology.
 Operation and maintenance costs are typically lower than those required for traditional remedies (such as soil vapor extrac-
 tion), because the remedy is generally resilient and self-repairing.
 Vegetation can help to reduce or prevent erosion and fugitive dust emissions.
 Plants can also improve air quality and sequester greenhouse gases.
 Plants can improve site aesthetics (visual appearance and noise).
 Site soil structure and fertility are not negatively impacted (and likely are improved).
 Remedy may be applicable at remote locations.
 Can be used adjacent to and without damage to mature trees and shrubs, and hardscape like decks and slate walkways.
 Phytotechnologies may be used in combination with other restoration or mitigation goals, such as a vegetated cap or creat-
 ing ecological diversity.
 Potential to create new habitat or supplement existing habitat.
 Final stages of a phytotechnology project can provide a land reuse/restoration asset upon completion.
                                                  Disadvantages
 Phytotechnologies may not be appropriate for sites with contamination at significant depths due to the generally shallow
 distribution of plant roots.
 A longer time period than more traditional, intrusive cleanup technologies may be required to achieve remedial goals.
 A large land area may be required for effective treatment in certain situations.
 High initial contaminant concentrations at a site may be phytotoxic and inhibit or prevent plant growth.
 Amendments and cultivation practices might exert unintended effects on contaminant mobility.
 Cultivation of vegetation can be more difficult under the adverse conditions of contaminated soil or groundwater; plant
 growth and associated remediation may not occur during winter season.
 A risk analysis may be necessary before disposal of any contaminated plant material.
 Potential to create new fate and transport pathways that may never have existed at the site prior to applying a particular
 phytotechnology (i.e., due to habitat creation).
 Sampling and analysis of plant and core tissues may be required to verify contaminant transfer issues occurring within the
 plant.
Sources:  ITRC.  2009. Phytotechnology Technical and Regulatory Guidance
and Decision Trees, Revised. EPA. 2001 a. Phytoremediation of Contaminated
Soil and Ground Water at Hazardous Waste Sites, EPA 540-S-01 -500.
February.

is successful, the pilot study will demonstrate if the site
conditions are compatible with the selected plants.  These
studies use site soil and/or groundwater samples containing
a range of concentrations of the target contaminants
to  determine remedial effectiveness.  As for  many
remedial approaches, sites undergoing treatment with
phytotechnologies will be monitored to assess performance.
Decision  trees  and other information to support evaluation
of  phytotechnology at a specific site are provided in
Phytotechnology Technical and Regulatory Guidance and
Decision  Trees, Revised (ITRC 2009).
   \
Photograph 1: Collection of gas and water vapor from a poplar tree
at the Oregon Poplar Superfund Site in Clackamas, Oregon.  Native
and hybrid poplar trees were planted on the site in  1998 to remediate
groundwater contaminated with volatile organic compounds.  Source: EPA.
h ftp://www. epa. gov/superfund/accomp/news/phyto. htm


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APPLICATIONS  OF
PHYTOTECHNOLOGIES
The effectiveness and economic viability of a phytotechnol-
ogy depend on climate, elevation, precipitation, soil type
and quality, the  type, age, distribution, and concentration
of contamination, media, and the viability of the plants and
planting system  used for each site.  Results of research,
laboratory studies, and field tests at similar sites can serve
as a guide to determining whether phytotechnologies are
appropriate for  a site.  Successful precedence can help you
identify appropriate plant species for implementation at
your site. If relevant existing local data are not available or
applicable, then site specific studies may be needed. If local
data are used, ensure that site conditions are similar to the
surrounding, undisturbed areas.
This section discusses contaminants that have been suc-
cessfully remediated or contained using phytotechnologies
and contaminants for which applications have  not proven
effective. As phytotechnology is relatively new, methods,
plant selection, and applications are constantly evolving
and improving.  The phytotechnology matrix in Table 4 lists
mechanisms, applications, and levels of testing for contami-
nants that phytotechnologies have effectively removed or
controlled.

Organic  Compounds	
Many organic compounds can be contained or remediated
through  phytodegradation, rhizodegradation,  phytoseques-
tration, and phytovolatilization. In addition, phytohydraulics
can be used to contain or remediate groundwater con-
taminated with organic compounds. Information on how
phytotechnologies apply to organic compounds is included
below.
Chlorinated  Solvents and Volatile Organic
Compounds (VOC)
Poplar trees, whose roots can grow up to 15 feet, have
proven successful at many sites for groundwater control and
contaminant removal through rhizodegradation, phytodeg-
radation, and phytovolatilization of chlorinated solvents
Photograph 2: Trees planted by Argonne National Laboratory in Mur-
dock, Nebraska in 2005. Phytoextraction is one of the technologies used
to remediate groundv/ater contaminated with carbon tetrachloride. Source:
Argonne National Laboratory.
through leaves and bark, as well as sorption of contaminants
to plant tissues (Compton et al. 2003). Phytovolatiliza-
tion can potentially release some contaminants into the
atmosphere. However, high levels of chlorinated solvents
have not been found in the air around the vegetation (EPA
2001 b).
Studies have shown that poplar trees can create a hydraulic
barrier by extracting large amounts of shallow groundwa-
ter (RTDF 2005). For example, at the Aberdeen Proving
Ground site, plantings of poplars reversed groundwater flow
during the summer months (Van Den Bos 2002).  However,
water uptake, as well as contaminant uptake in soil, es-
sentially stops during the winter when plants are dormant.
Rhizodegradation continues but at a reduced rate.  During
project design, it is important to model seasonal variations  in
water uptake by the trees. If the model shows that the plume
will travel beyond the trees by the end of the dormant sea-
son, then a backup system would be needed (ITRC 2009).

Munitions
Phytotechnologies show considerable promise for explosives
remediation, especially for treatment of large volumes of
lightly contaminated soil and groundwater through phyto-
degradation (McCutcheon and Schnoor 2003). The Depart-
ment of Defense has conducted extensive research into using
phytotechnologies for cleanup of ground and surface water
contaminated with explosives, including trinitrotoluene (TNT),
cyclotrimethylenetrinitramine (RDX), and similar compounds.
Most research studies have been conducted using wetland
plants and have shown promising results.  For example, two
engineered wetlands were constructed at the Iowa Army
Ammunition Plant to phytoremediate explosives-contaminat-
ed surface water.  The wetlands successfully remediated RDX
in surface water from approximately 800 parts per billion to
non-detect levels (Kiker et al. 2001).
In addition, research is being conducted on the development
of transgenic plants (see Transgenics Section of this fact
sheet) that are able to phytoremediate RDX-contaminated
soils.  The plants have an enzyme that uses bacteria to break
down RDX and decrease toxicity of the contaminant (Rylott  et
al2006).
Perchlorate is a common munitions constituent. A laboratory
study by the University of Georgia showed that perchlorate-
contaminated water could be remediated through phytodeg-
radation and rhizodegradation under anaerobic conditions.
Laboratory studies for perchlorate-contaminated soil (simu-
lating field conditions) also showed removal of perchlorate
(Willey 2007).
Persistent Organic  Pollutants (POP)
POPs consist of a group of contaminants, mainly pesticides
and polychlorinated biphenyls (PCB), with the following
characteristics:  toxicity, persistence, bioaccumulation, and
long-range transport. Phytotechnologies are generally not
considered to be feasible for stockpiles of PCB-contaminated
soil but can be used as a polishing technology for residual
contamination in soil. While a pilot study using three differ-

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ent types of plants (zucchini, sedge, and fescue) showed in-
sight for future studies, none of the species in this study were
likely to provide a cost-effective alternative to traditional
treatment methods. Soil samples after one growing season
revealed  no detectable decrease in soil PCB concentrations,
and the study reported that it could take several growing
cycles before a decrease in soil PCB concentration  might be
observed (Whitfield Aslund et al. 2006).
POPs have been treated using phytostabilization and phyto-
hydraulics. Laboratory research has shown the potential for
rhizodegradation and phytoextraction of PCBs. Preliminary
research  has identified plant species that effectively accumu-
late highly weathered pesticide and PCB residues from the
soil.  Research from the Ukraine and Kazakhstan has shown
that bean plants can accumulate and even decompose the
pesticide dichlorodiphenyltrichloroethane (DDT) (EPA 2006).
Pesticides such as dichlorodiphenyldichloroethylene (DDE)
have been detected in the roots of a variety of vegetables,
but translocation of these contaminants from the roots to the
shoots has been found only in zucchini and pumpkin (Wil-
ley 2007). For example, a pilot study  was conducted that
compares the ability of closely related  species (zucchini and
squash) to take up DDE from  contaminated soil as well as
from hydroponic solutions. Results from the study show that
zucchini roots and stems extracted 12  times more DDE than
squash tissue.  In addition, in hydroponic solutions, squash
was significantly more sensitive to DDE exposure than zuc-
chini (Chhikara, S. and others 2010).
Petroleum Products
Petroleum products that have impacted soil, surface water,
or groundwater have been successfully remediated, gener-
ally through rhizodegradation.  Most commonly, studies
on rhizodegradation of petroleum products used grasses;
but other species, such as hybrid poplars, willows,  and
legumes, were also used.  However, the presence of mixtures
of contaminants at a site poses greater difficulty for design-
ing and selecting a successful phytoremediation approach.
Moreover, high molecular weight PAHs and aged petroleum
products  are less bioavailable and not successfully  remedi-
ated by phytotechnologies (Van Epps 2006).
Laboratory and field studies have shown that lower weight
PAHs can be remediated using various combinations of
grasses through rhizodegradation and phytovolatilization.
Native grasses, perennial ryegrass (Lolium perenne), intro-
duced cool-season and warm-season grasses, and legumes
have been used (EPA 2001 a).

Metals  and Other Inorganics
Metals and other inorganics cannot be degraded through
phytotechnology mechanisms. Generally, phytotechnologies
have had limited success in efforts to extract metals. An
alternative is to stabilize the metals and ecologically restore
the site using soil amendments. "The Use of Soil Amend-
ments for Remediation, Revitalization and Reuse" (EPA
542-R-07-013) provides additional information on this topic
(EPA 2007) and is available at:  http://www.clu-in.org/
download/remed/epa-542-R-07-013.pdf.  "Chelators" can
be added to soil to enhance the plant-availability of con-
taminants, but some types of amendments may also increase
the bioavailability and mobility of these chemicals, and may
cause leaching of the chelated pollutants into groundwater
(Chaneyetal. 2007).
Some metals and metal-complexes in soils can be remedi-
ated by phytoextraction and phytosequestration. Phytovola-
tilization  can occur with some metals (specifically, mercury
and selenium). Phytohydraulics can also be used to contain
and treat groundwater contaminated with certain metals.
High-biomass plants extract low levels of metals as essential
nutrients, while hyperaccumulators can take up and con-
centrate a particular contaminant up  to 100 or 1,000 times
greater than the concentration in soil; this higher concentra-
tion of metals in the leaves may discourage animal consump-
tion of the plants (Pollard and Baker 1997) or provide an
advantage to plants  in colonizing harsh soils.  Phytotechnol-
ogy applications for a variety of metals are discussed below.
Arsenic
Arsenic contaminated soil and groundwater have been suc-
cessfully remediated through phytoextraction.  Some ferns,
such as Pteris vittata, have been shown to hyperaccumulate
arsenic effectively (Ma et al. 2001). These ferns grow in
areas with mild climates and have roots that extend about
12 inches into the soil, depending on soil texture and arsenic
concentration in the soil (Liao et al. 2004). Therefore, ap-
propriate sites for this application are limited to those in mild
climates with relatively shallow contamination. Phytoextrac-
tion of arsenic is applicable for small or large sites.
At appropriate sites, hyperaccumulating ferns, such as Pteris
vittata and Pityrogramma calomelanos, can  accumulate over
2 percent arsenic in  their biomass (Gonzaga et al. 2006);
Edenfern™ can accumulate arsenic in its fronds at levels up
to 100 times the underlying soil concentration (Edenspace
2010). While Pteris vittata is considered a hyperaccumula-
tor for arsenic, the plant converts arsenate to arsenite (a
highly toxic form of arsenic), so caution is required if using
these plants (Peer 2005).  At a contaminated site, fronds
can be harvested for recycling or landfill disposal.  Where
recycling is feasible, arsenic in the fronds can be recovered
at rates greater than 70 percent through fluid extraction;
recovered arsenic can be  reused in industrial applications.
Cadmium
Phytoextraction of cadmium contaminated soil has been
shown to be very slow because of the low biomass and
slow growth rate of cadmium-specific hyperaccumulators.
However, research studies show that the process can be
enhanced by using two-phase planting of the hyperaccu-
mulator Cress (Rorippa globosa).  In two-phase cultivation,
the plants are transplanted into contaminated soils twice in
one year by harvesting the plants when they are flowering.
Research results are  promising, but literature reviewed for
this fact sheet does not document field applications (Wei and
Zhou 2006).
i
;


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                                                                                                           TABLE 4
                                                                                              PHYTOTECHNOLOGY MATRIX

Contaminant
Phytotechnology
Mechanism
ytosequestration
Q_
lizodegradation
&.
_u
~5
D
J.
1
Q_
ytoextraction
Q_
ytodegradation
Q_
ytovolatilization
Q_
Applications
Constructed Treatment
Wetland/Aquatic Plant Lagoon

"c
D
CL
£
c
O
"5-
£
Hyper-accumulation
Scale
Greenhouse
Laboratory
"D
0
u_
Jo
al
Full-scale
Additional Comments
Reference
Organic Compounds
BTEX
Chlorinated Solvents
PCBs
Munitions
PAHs
Pesticides
Petroleum Products


S


S

S
V
V
S
S

•/
S
S
S


S



•/




^
^

^


•/
•/
S




•/
^
S

S


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Chromium
While a chromium-specific hyperaccumulator has not been
identified, recent studies indicate that certain plant spe-
cies can be applied to address chromium contamination
in soil, surface water, or groundwater by removal through
phytoextraction and phytostabilization.  For example,
willow (Salix spp.) and birch (Betula spp.) trees are able to
take up chromium and could be used to  treat chromium-
contaminated groundwater; however, chromium stays mainly
within the roots (Pulford et al. 2001). In  addition, chromium
in estuaries (specifically, high saline coastal waters) can be
absorbed by agricultural waste material, or bagasse (fiber
remaining after juice is removed from sugarcane) (Krishnani
et al. 2004). Finally, tumbleweed or Russian thistle (So/so/o
kali) has  been shown to accumulate chromium, specifi-
cally chromium(VI); this indicates that this plant might be
considered for phytoextraction of chromium in soil (Gardea-
Torresdey et al. 2005).
Copper
No known hyperaccumulator has been identified for phy-
toextraction of copper. Initial studies using a greenhouse
hydroponic system (i.e., plants grown in  a  media nutrient
solution)  have shown that black willow (So//x nigra) accumu-
lates more copper than other willow species, but field studies
are necessary to  determine the feasibility of this species for
phytoextraction of copper (Kuzovkina et  al. 2004).  In addi-
tion, soil  amendments, such as phosphate,  can  increase cop-
per uptake as shown in initial studies using Indian mustard
(Brassica juncea) plants, and could be further researched for
phytotechnology  applications (Wu et al.  2004).

Lead
The use of soil amendments and planted  systems to stabilize
lead in soil is quite effective (EPA 2007). However, because
lead is only sparingly bioavailable in soil, phytoextraction
is ineffective.  Significant research has gone into the use of
soil chelators to enhance bioavailability of  lead, but these
amendments can cause the indiscriminate increase of lead
mobility,  and leaching of the chelated lead into surface and
groundwater while not being very effective for increasing
lead uptake by plants (Chaney et al. 2007).

Nickel
Mine sites with nickel impacted soils have been successfully
remediated by phytoextraction using the hyperaccumulators
Alyssum sp., which include plants in the  mustard family.  In
addition, Alyssum hybrids have been developed to allow
phytomining (that is, extracting nickel from the plants by
drying and combusting the plants) (Chaney et al. 2007).
Selenium
Selenium impacted soil, sediment, and surface water have
been successfully remediated through phytoextraction,
phytosequestration, and phytovolatilization, depending on
the plants used.  For example, the aquatic  plants duckweed
(Lemnaoideae) and water hyacinth (Eichhornia spp.) can
effectively remediate selenium using constructed treatment
wetlands (EPA 2001 a).  In addition, Indian mustard (Bras-
sica juncea) and canola (Brassica napus) have been used in
phytovolatilization of selenium; in this application, selenate
is converted to a less-toxic dimethyl selenite gas and re-
leased to the atmosphere (EPA 2000).
Zinc
Pilot studies to date have shown that phytoextraction is likely
not effective for removing zinc from soil. Many plant species
are not able to accumulate significant amounts of zinc.
Those that do effectively remove zinc are slow growing, or
do not have much biomass.  Moreover, although a few plant
species can accumulate zinc (for example,  Thlaspi caerulen-
scens), the presence of other contaminants  commonly found
with zinc, such as copper, can limit the growth of these
plants and their uptake of zinc (Lombi et al. 2001).

Radionuclides	
Phytoextraction has been considered for remediation of
soil and water contaminated with radionuclides.  Some
studies show that the potential of phytoextraction  could be
greater for addressing technetium (Tc) than other  radionu-
clides. While Tc appears to be less bioavailable in terres-
trial ecosystems, aquatic plants have a strong potential to
accumulate and retain Tc. Regarding other radionuclides,
sunflower plants effectively remove uranium, cesium, and
strontium from hydroponic solutions.  In addition, plants
such as redroot pigweed take up cesium and strontium from
contaminated soil (EPA 2004).
Soil amendments can increase plant uptake of radionuclides.
One study showed that Johnson grass (Sorhgum halpense)
planted in soil amended with poultry litter accumulated
greater amounts of cesium and strontium than did other
plant species in soil amended with poultry  litter or other soil
amendments.

Transgenics	
No full-scale applications of transgenic, or genetically
altered, plants for site remediation are known. A few
laboratory and  pilot studies have shown promising results in
using  transgenic plants for phytoextraction of contaminants
(for cases where effective natural plants have not been
identified).  Transgenic research on a variety of applications
is occurring for constructed treatment wetlands, field crops,
and tree plantations for several contaminants. Much of the
current transgenic research is focused on understanding the
genomics behind the ability of some plants and bacteria
to modify or remove pollutants (Doty 2008).  This sec-
tion includes some examples  of transgenic  research being
conducted.

  Permits from U.S. Department of Agriculture and or
  state agencies may be needed prior to testing or using
  transgenic plants. For additional information on USDA
  permits for studies and other applications involving
  transgenic plants, see:  http://www.aphis.usda.gov/
  permits/brs_epermits.shtml.

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Phytotechnology Success Stories on Superfund Sites

•  Aberdeen Proving Grounds, J-Fields, Maryland: Hybrid poplar trees were used to remove TCE and
   tetrachloroethylene (PCE) contamination from the groundwater. http://www.epa.gov/reg3hscd/super/sites/
   MD2210020036/index.htm

•  Combustion, Inc., Louisiana: Poplars, native willows, and eucalyptus were used to remediate PCB
   contamination in groundwater. http://www.epa.gov/region6/6sf/pdffiles/0600472.pdf

•  Tibbetts Road, New Hampshire: A wooded phytoremediation area was planted to treat soil and
   groundwater contaminated with chlorinated and non-chlorinated solvents, http://www.wildlifehc.org/
   ewebeditpro/items/O57F3072.pdf

•  Aberdeen Pesticide Dumps, North Carolina:  Trees were planted to remediate groundwater contaminated
   with VOCs, pesticides, semi-volatile organic compounds (SVOC), and metals,  http://www.epa.gov/region04/
   waste/npl/nplnc/aberdnnc.htm

•  Fort Wainwright, Alaska: Willows were planted to remediate soil and groundwater contaminated with
   pesticides. http://www.clu-in.org/products/phyto/search/phyto_details.cfm?ProjectlD=44

•  Bay Road, California: Eucalyptus and tamarisk were planted for hydraulic control of groundwater
   contaminated with arsenic within a slurry wall.  http://www.clu-in.org/products/phyto/search/phyto_details.
   cfm?ProjectlD=64

•  McCormick and Baxter Superfund site, Oregon: Hybrid poplars and perennial rye grasses were used
   to remediate shallow soil contaminated with PAHs and pentachlorophenol (PCP). http://www.deq.state.or.us/lq/
   cu/nwr/McCormickBaxter/

•  Hanford 100-N Area, Washington:  Phytoremediation was selected as a polishing step for groundwater
   contaminated with strontium 90.  http://www.hanford.gov/docs/gpp/science/em21 /phyto%20work%20plan.pdf

•  Naples Truck Stop, Utah: Poplars were used to remediate groundwater contaminated with petroleum
   products. http://www.clu-in.org/products/phyto/search/phyto_details.cfm?ProjectlD=190

•  Palmerton Zinc Pile Superfund Site, Pennsylvania:  Grasses were used for hydraulic control and
   stabilization of soil, sediment, and groundwater contaminated with metals, http://www.epa.gov/reg3hscd/super/
   sites/PAD002395887/index.htm

•  Fort Drum Gasoline Alley, New York: Willows were used to remediate surface water contaminated with
   benzene, toluene, ethylbenzene, and xylenes (BTEX).  http://www.clu-in.org/products/phyto/search/phyto_
   details.cfm?ProjectlD=229

•  East Multnomah County Groundwater Contamination, Cascade Corporation Site (OU 2),
   Oregon: Poplars were used to remediate groundwater contaminated with TCE.  http://www.deq.state.or.us/lq/
   ECSI/ecsidetail.asp?seqnbr=635

•  Edward Sears Poplar Site, New Jersey:  Hybrid Poplars were used to remediate groundwater
   contaminated with volatile organic compounds. http://costperformance.org/profile.cfm?ID=62&CaselD=62

•  Kauffman and Minteer Site, New Jersey: Native black willows and hybrid poplars were planted  in this
   pilot study to remediate soil and groundwater contaminated with chlorinated solvents,  http://cluin.org/download/
   techfocus/phyto/RemediationJ-13-3-21 .pdf (p. 31)

•  Oregon Poplar Site, Oregon:  Native and hybrid poplar trees were planted on the site in 1998 to remediate
   groundwater contaminated with volatile organic compounds, http://www.epa.gov/superfund/accomp/news/
   phyto.htm

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The transgenic plants Arabidopsis thaliana L and tobacco
[Nicotiana tobacum) can transform  methyl-mercury into
elemental mercury before releasing it into the atmosphere.
From a regulatory perspective, however, such mercury
releases are not acceptable; therefore, these genetically
altered plants are not recommended for phytovolatilization
of mercury. A research team at the University of Georgia
successfully developed  a transgenic yellow poplar (Liri-
odendron tulipifera) that is fast growing, pest resistant, and
effective at absorbing mercury.  This transgenic poplar trans-
formed ionic mercury to a much less toxic and less volatile
metallic mercury (Meagher  1999; Dhankher and Meagher
2003). Additional research is focusing on (1) increasing
plant tolerance to mercury and arsenic, (2) transforming the
toxic elements to promote transport from roots to shoots, (3)
transforming these toxic elements to promote storage in the
aboveground plant parts, (4) enhancing the plants' ability to
trap toxicants aboveground, and (5) enhancing transporters
for uptake and storage (Meagher 2007).
In 2007, researchers at the  University of Washington
published promising results  regarding the development of a
transgenic poplar for phytoremediation of trichloroethylene
(TCE), vinyl chloride, carbon tetrachloride, benzene, and
chloroform in water and air (Doty and others 2007).
Field studies completed using transgenic Indian mustard
plants to phytoremediate soil contaminated with selenium
and boron show promise. The transgenic plants accumu-
lated much more selenium in their leaves and tolerated the
contaminated soil better than natural Indian mustard plants
(growing much more successfully in contaminated soil)
(Banuelos 2005).
Additional examples of phytotechnology research, including
the use of transgenic plants  and endophytes, or bacteria that
reside within plant tissue, can be found in Doty's "Enhanc-
ing  phytoremediation through the use of transgenics and
endophytes" (2008).

Resources Used  for this Fact
Sheet	
Banuelos, Gary and others. 2005.  "Field Trial of Trans-
genic Indian Mustard Plants Shows Enhanced Phytoremedia-
tion of Selenium-Contaminated Sediment."  Environmental
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phyto3.pdf
Chaney, Rufus L., Minnie Malik, Yin M. Li, Sally L. Brown,
Eric P. Brewer, J. Scott Angle, and Alan J. M. Baker. 1997.
"Phytoremediation of soil metals." Environmental Biotech-
nology.  Vol. 8, pp. 279-284.
Chaney, Rufus L., J. Scott Angle, C.  Leigh Broadhurst,
Carinne A.  Peters, Ryan V Tappero, and Donald L. Sparks.
2007.  "Improved Understanding of Hyperaccumulation
Yields Commercial Phytoextraction and Phytomining Tech-
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1429-1443.
Chhikara, Sudesh, Bibin Paulose, Jason C. White, and Om
Parkash Dhankher.  2010.  Understanding the Physiological
and Molecular Mechanism of Persistent Organic Pollutant
Uptake and Detoxification in Cucurbit Species (Zucchini and
Squash). Environ. Sci. Technol.  Accepted April 21, 2010.
Compton, Harry R., George R. Prince,  Scott C. Fredericks,
and Christopher D. Gussman. 2003.  "Phytoremediation
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Dhankher, Om Parkash and Richard B. Meagher.  2003.
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and Arsenic Pollution.
Doty, Sharon L. and others.  2007. "Enhanced Phytoreme-
diation of Volatile Environmental Pollutants with Transgenic
Trees." Proceedings of the National Academy of Sciences of
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Gardea-Torresdey JL,  G. de la Rosa, J.R.  Peralta-Video, M.
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&pid=S0103-90162006000100015
Interstate Technical Regulatory Council  (ITRC). 2009. Phyto-
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Kiker, Jackson H., Steve Larson, Donald D. Moses, and
Randy Sellers.  2001.  "Use of Engineered Wetlands to
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at the Iowa Army Ammunition Plant, Middletown, Iowa."
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fication of chromium(VI) in coastal water  using lignocellu-
losic agricultural waste." Water SA. Vol. 30, pp. 541 -545.
Kuzovkina, Y.A.,  M. Knee, and M.F. Quigley. 2004.
"Cadmium and copper uptake and translocation  in five wil-
                                                     10

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low (Salix L.) species."  Int J Phytoremediation. Vol. 6, pp.
269-287.
Liao, X.-Y., T.-B. Chen, M. Lei, Z.-C. Huang, X.-Y. Xiao, and
Z.-Z. An. 2004.  "Root distributions and elemental accumu-
lations of Chinese brake (Pteris vittata) from As-contaminated
soils." Plant and Soil. Vol. 261, No. 1 -2, pp. 109-116.
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2001. "Phytoremediation of Heavy Metal-Contaminated
Soils : Natural Hyperaccumulation versus Chemically
Enhanced Phytoextraction." J. Environ. Qual. Vol. 30, pp.
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Ma, L. Q., K.M. Komar, C. Tu, W.H. Zhang, Y. Cai, and E.D.
Kennelley. (2001).  "A fern that hyperaccumulates arsenic:
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from contaminated soils." Nature. Vol. 409, p. 579.
McCutcheon, S.C.  and J. L. Schnoor.  2003.  Phytoremedia-
tion: Transformation and Control of Contaminants. John
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39435-1. 987pp.
Meagher, Richard B. 1999.  Phytoremediation of Ionic and
Methyl Mercury Pollution. DOE-EMSP 6/14/1999. http://
www.osti.gov/em52/1999projsum/54837.pdf
Meagher, R.B. (2007). Multigene strategies for engineering
the phytoremediation of mercury and arsenic. In: Bio-
technology and Sustainable Agriculture 2006 and Beyond:
Proceeding of the 11 th IAPTC&B Congress, Z. Xu, J. Li, Y.
Xue, and W. Yang, eds (Beijing, China: Springer), 49-
60. http://ersdprojects.science.doe.gov/workshop_pdfs/
new_orleans_2003/first_session/Dhanker.pdf
Peer, Wendy Ann and others. 2005.  Phytoremediation and
Hypeaccumulator Plants.
Pollard, A. Joseph and Alan J. M. Baker.  1997. "Deter-
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Poynton,  CY, J.W. Huang, MJ. Blaylock, L.V  Kochian, and
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Pulford, I. D., C. Watson, and S.D. McGregor. 2001.
"Uptake of chromium by trees: prospects for phytoremedia-
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U.S. Environmental  Protection Agency (U.S. EPA).  2000.
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U.S. EPA. 2001 a.  Phytoremediation of Contaminated
Soil and Ground Water at Hazardous Waste Sites, EPA
540-S-01 -500. February, http://www.epa.gov/nrmrl/
pubs/540s01500/epa_540_s01 _500.pdf
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U.S. EPA.  2005. Evaluation of Phytoremediation for
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of Organics Action Team, Chlorinated Solvents Workgroup.
January.
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Wei, S.H. and Q.Z. Zhou. 2006. "Phytoremediation of
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"Phytoremediation: A Plant-Microbe-Based Remediation    A
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                                                       n

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Additional  EPA  Resources
• Clu-in Technical Focus on Phytoremediation:  http://www.cluin.org/techfocus/default.focus/sec/
  Phytotechnologies/cat/Overview


• Phytotechnology Project Profiles: http://www.cluin.org/products/phyto
Additional  Information Resources	
• Phytotechnology Technical and Regulatory Guidance and Decision Trees, Revised.
  Interstate Technology and Regulatory Council (ITRC) Phytotechnologies Team.  2009.
  PHYTO-3, 187pp. http://www.itrcweb.org/Documents/PHYTO-3.pdf
  International Journal of Phytoremediation: http://www.tandf.co.uk/journals/titles/15226514.asp
  International Society of Phytotechnologies:  http://www.phytosociety.org
  U.S. Department of Agriculture Plants Database:  http://plants.usda.gov
  Phytoremediation Electronic Newsgroup Network: http://www.dsa.unipr.it/phytonet
WHO  CAN I CONTACT  FOR MORE INFORMATION?
If you have any questions or comments on this fact sheet, please contact:
Steven Rock, EPA
rock.steven@epa.gov
 Office of Superfund Remediation
 and Technology Innovation
 (5203P)
           Linda Fiedler, EPA
           fiedler.linda@epa.gov
EPA 542-F-10-009
September 2010
www.epa.gov
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