EPA/600/R-21/063 | May 2021
www.epa.gov/emergency-response-research
United States
Environmental Protection
Agency
oEPA
Review of Phytoremediation
Technologies for Radiological
Contamination
Office of Research and Development
Homeland Security Research Program

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EPA/600/R-21/063
Review of Phytoremediation Technologies for Radiological
Contamination
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Disc er
U.S. Environmental Protection Agency
The U.S. Environmental Protection Agency (EPA), through its Office of Research and
Development's National Homeland Security Research Center, funded and managed this
evaluation. The document was prepared by Lawrence Livermore National Laboratory under
Interagency Agreement (DW-89-92426601). This document was reviewed in accordance with
EPA policy prior to publication. Note that approval for publication does not signify that the
contents necessarily reflect the views of the Agency. Mention of trade names or commercial
products does not constitute endorsement or recommendation for use of a specific product.
Lawrence Livermore Nation oratory
This document was prepared as an account of work sponsored by an agency of the United States
government. Neither the United States government nor Lawrence Livermore National Security,
LLC, nor any of their employees makes any warranty, expressed or implied, or assumes any
legal liability or responsibility for the accuracy, completeness, or usefulness of any information,
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Livermore National Security, LLC. The views and opinions of authors expressed herein do not
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LLC, for the U.S. Department of Energy, National Nuclear Security Administration under
Contract DE-AC52-07NA27344.
Questions concerning this document, or its application should be addressed to:
Sang Don Lee, Ph.D.
Homeland Security and Materials Management Division
Center for Environmental Solutions and Emergency Response
Office of Research and Development
U.S. Environmental Protection Agency
(919)541-4531
lee.sangdon@epa.gov
If you have difficulty accessing these PDF documents, please contact
McCall.Amelia@epa.gov for assistance.
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Foreword
The U.S. Environmental Protection Agency (EPA) is charged by Congress with protecting the
nation's land, air, and water resources. Under a mandate of national environmental laws, the
Agency strives to formulate and implement actions leading to a compatible balance between
human activities and the ability of natural systems to support and nurture life. To meet this
mandate, EPA's research program is providing data and technical support for solving
environmental problems today and building a science knowledge base necessary to manage our
ecological resources wisely, understand how pollutants affect our health, and prevent or reduce
environmental risks in the future.
The EPA's Center for Environmental Solutions and Emergency Response (CESER) within the
Office of Research and Development (ORD) conducts applied, stakeholder-driven research and
provides responsive technical support to help solve the nation's environmental challenges. The
Center's research focuses on innovative approaches to address environmental challenges
associated with the built environment. We develop technologies and decision-support tools to help
safeguard public water systems and groundwater, guide sustainable materials management,
remediate sites from traditional contamination sources and emerging environmental stressors, and
address potential threats from terrorism and natural disasters. CESER collaborates with both public
and private sector partners to foster technologies that improve the effectiveness and reduce the cost
of compliance, while anticipating emerging problems. We provide technical support to EPA
regions and programs, states, tribal nations, and federal partners, and serve as the interagency
liaison for EPA in homeland security research and technology. The Center is a leader in providing
scientific solutions to protect human health and the environment.
This study report identified key documents in regard to practical experiences in field-deployed
phytoremediation efforts in the U.S., the former Soviet Union and Japan, with considerations to
site preparation and maintenance, remediation effectiveness, and waste management.
Recommendations are provided for candidate plant species based on the literature review, and
technical gaps are identified.
Gregory Sayles, PhD.
Director, Center for Environmental Solutions and Emergency Response
EPA's Office of Research and Development
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Acknowl lents
Research Team
Mark Sutton (Lawrence Livermore National Laboratory)
Sang Don Lee [U.S. EPA Homeland Security & Materials Management Division
(HSMMD), Center for Environmental Solutions & Emergency Response
(CESER])
Technical Reviewers
Paul Lemieux (U.S. EPA HSMMD, CESER)
Terry Stillman (U.S. EPA Region 4)
External Peer-Reviewers
Mike Kaminski (Argonne National Laboratory)
Rick Demmer (Idaho National Laboratory)
Quality Assurance Reviewer
Ramona Sherman (U.S. EPA HSMMD, CESER)
Edit Reviewer
Marti Sinclair
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Executive Summary
Phytoremediation is a set of technologies that use various plants and microbes to degrade,
extract, contain, or immobilize contaminants from soil and water. Phytoremediation is an
integrated approach applied to the cleanup of contaminated soil that combines the disciplines of
plant physiology, soil chemistry, and soil microbiology. It offers a viable method for stabilizing
and removing contamination at significantly less cost than alternatives such as excavation or
pump-and-treat methods. Initially deployed to address organic and heavy metal contamination
of soil and groundwater, the application of phytoremediation has expanded over recent years to
include mitigation of radionuclide contamination. A large volume of literature exists evaluating
the feasibility of plant species to effectively remove actinide (e.g., uranium, plutonium,
neptunium) and fission product radiological contamination in the environment. Key documents
are identified here in regard to practical experiences in field-deployed phytoremediation efforts
in the U.S., the former Soviet Union and Japan, with considerations to site preparation and
maintenance, remediation effectiveness, and waste management. Recommendations are
provided for candidate plant species based on the literature review, and technical gaps in the
current knowledge base are identified.

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Acronyms
Am-241	americium-241
ANOVA	analysis of variance
ANL	Argonne National Laboratory
BAF	bioaccumulation factor
CR	concentration ratio
Cs-134	cesium-134
Cs-137	cesium-137
DHS	U.S. Department of Homeland Security
DOE	U.S. Department of Energy
EPA	U.S. Environmental Protection Agency
H-3	tritium
IAEA	International Atomic Energy Agency
INL	Idaho National Laboratory
ITRC	Interstate Technology & Regulatory Council
JAEA	Japanese Atomic Energy Agency
LLRW	low-level waste
Np-237	neptunium-237
NPP	nuclear power plant
PPE	personal protective equipment
Pu-238	plutonium-238
RDD	radiological dispersal device
Sr-90	strontium-90
SRS	Savannah River Site
U-238	uranium-238
USD A	United States Department of Agriculture
Units
Bq	Becquerel(s) (one disintegration per second, equivalent to 2.7 x 10"11 Curies)
Ci	Curie(s) (equivalent to 3.7 x 1010 Becquerels)
g	gram(s)
ha	Hectare(s) (1 hectare = 2.471 acres)
m	meter(s)
L	liter(s)
Unit Prefixes
c	centi (10"2)
k	kilo (103)
m	milli (10"3)
M	mega(106)
p	pico (10"12)
P	Peta (1015)
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Table of Contents
Disclaimer	
U.S. Environmental Protection Agency	
Lawrence Livermore National Laboratory	
Foreword	
Acknowledgments	
Executive Summary	
Acronyms	
Units	
Unit Prefixes	
Table of Contents	
Figures	
Tables	
1.	Introduction	
1.1 Quality Assurance	
2.	Radionuclide Phytoremediation Literature Survey	
2.1	General Published Guidance on Radionuclide Phytoremediation	
2.2	Literature Review of Radiocesium Phytoremediation	
2.3	Applied Radiological Phytoremediation: Pilot- and Full- Scale Studies	
2.3.1	U.S. DOE Sites	
2.3.2	Post-Chernobyl Applied Phytoremediation	
2.3.3	Post-Fukushima Applied Phytoremediation	
3.	Technical Considerations for Radiological Phytoremediation	
3.1	Plant Selection and Technical Performance	
3.2	Labor, Expertise and Supporting Equipment	
3.3	Generation and Management of Waste	
4.	Recommendations and Gaps in Phytoremediation Use in Wide Area Radiological
Contamination Events	
6. References	
Figures
Schematic figure showing contaminant deposition and migration paths	
Tables
Estimated Cost of Remediation Options for ANL-W Site (DOE 1998)

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1. Introduction
Radiological contamination stemming from nuclear facility accidents or intentional releases such
as a radiological dispersal device (RDD) can lead to large areas of urban and/or rural land
requiring decontamination. A broad range of expertise and capabilities have been tried and
tested for mitigating the effects of radiological contamination, particularly in the remediation and
recovery phases following nuclear power plant accidents such as Chernobyl and Fukushima, but
also including nuclear material handling and disposal sites where historical contamination
existed. Various techniques and technologies may be employed to remove both surface
deposited and entrained contamination. Decontamination can be non-destructive (e.g., washing)
or destructive (e.g., surface removal and subsequent disposal) to surface, depending on the
contaminant and surface. Contamination events can lead to atmospheric, surface and/or
subsurface contamination, each of which can cause subsequent migration of contaminants into
another medium. A variety of techniques can also be used to bind (or stabilize) contaminants in
place, preventing both resuspension and further increase in impacted areas.
One remediation method that employs both stabilization and subsequent removal
(decontamination) is phytoremediation. Specifically, phytoremediation is a set of technologies
that use various plants and microbes to degrade, extract, contain, or immobilize contaminants
from soil and water. It is an integrated approach applied to the cleanup of contaminated soil that
combines the disciplines of plant physiology, soil chemistry, and soil microbiology (Hossner et
al., 1998). Depending on the nature of the contaminant soil and plant pathways and properties,
there are different approaches to using plants in the remediation of environmental contaminants.
The United States Environmental Protection Agency's (EPA's) Phytoremediation Resource
Guide (U.S. EPA, 1999) provides an overview of the various approaches:
Phytoextraction
Also called phytoaccumulation, phytoextraction refers to the uptake and translocation of
metal contaminants in the soil by plant roots into the aboveground portions of the plants.
Certain plants called hyper accumulators absorb unusually large amounts of metals in
comparison to other plants. One or a combination of these plants is selected and planted
at a site based on the type of metals present and other site conditions. After the plants
have been allowed to grow for several weeks or months, they are harvested and either
incinerated or composted to recycle the collected contaminants such as metals. This
procedure may be repeated as necessary to bring soil contaminant levels down to targeted
limits.
Rhizofiltration
Rhizofiltration is the adsorption or precipitation onto plant roots, or absorption into the
roots, of contaminants that are in solution surrounding the root zone. The plants to be
used for cleanup are raised in greenhouses with their roots in water rather than in soil. To
acclimate the plants once a large root system has been developed, contaminated water is
collected from a waste site and brought to the plants where it is substituted for their water
source. The plants are then planted in the contaminated area where the roots take up the
water and the contaminants along with it. As the roots become saturated with
contaminants, they are harvested and either incinerated or composted to recycle the
contaminants.
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Phytostabilization
Phytostabilization is the use of vegetation to contain soil contaminants in situ, through
modification of the chemical, biological, and physical conditions in the soil. Contaminant
transport in soil, sediments, or sludges can be reduced through absorption and
accumulation by roots; adsorption onto roots; precipitation, complexation, or metal
valence reduction in soil within the root zone; or binding into humic (organic) matter
through the process of humification. This process reduces the mobility of the contaminant
and inhibits migration to the ground water or air, and it reduces bioavailability for entry
into the food chain. This technique can be used to reestablish a vegetative cover at sites
where natural vegetation is lacking due to high metal concentrations in surface soil or
physical disturbances to surficial materials. Metal-tolerant species can be used to restore
vegetation to the sites, thereby decreasing the potential migration of contamination
through wind erosion, transport of exposed surface soil, and leaching of soil
contamination to ground water.
Phytodegradation
Also called phytotransformation, phytodegradation is the breakdown of contaminants
taken up by plants through metabolic processes within the plant, or the breakdown of
contaminants external to the plant through the effect of compounds (such as enzymes)
produced by the plants. Pollutants are degraded, incorporated into the plant tissues, and
used as nutrients.
Rhizodegradation
Also called enhanced rhizosphere biodegradation, phytostimulation, or plant-assisted
bioremediation/degradation, rhizodegradation is the breakdown of contaminants in the
soil through microbial activity that is enhanced by the presence of the rhizosphere and is
a much slower process than phytodegradation. Microorganisms (yeast, fungi, or bacteria)
consume and digest organic substances for nutrition and energy. Certain microorganisms
can digest organic substances such as fuels or solvents that are hazardous to humans and
break them down into harmless products through biodegradation. Natural substances
released by the plant roots—sugars, alcohols, and acids—contain organic carbon that
provides food for soil microorganisms, and the additional nutrients enhance microbial
activity. Biodegradation is also aided by the way plants loosen the soil and transport
water to the contaminated area.
Phytovolatilization
Phytovolatilization is the uptake and transpiration of a contaminant by a plant, with
release of the contaminant or a modified form of the contaminant to the atmosphere from
the plant. Phytovolatilization occurs as growing trees and other plants take up water and
the organic contaminants. Some of these contaminants can pass through the plants to the
leaves and volatilize into the atmosphere at comparatively low concentrations.
Since radionuclide contamination cannot be chemically altered into a less radioactive material,
techniques such as phytodegradation, rhizodegradation and phytovolatilization are not applicable
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to radionuclide remediation. However, phytoextraction, rhizofiltration and phytostabilization are
methods that can be employed to stabilize and subsequently remove contamination from both
soil and ground/surface water.
Once radioactive contamination is deposited on soil, its migration downward is governed by
convective transport by flowing water, dispersion caused by spatial variations of convection
velocities, diffusive movement within the fluid, and physicochemical interactions with the soil
matrix (IAEA, 2010). The former three governing actions can be generally described by
traditional convection and dispersion time-dependent models. The last action can be generally
described by equilibrium processes occurring at the interface of the soil, soil water and plant.
The contaminant must be soluble to interact with soil or sediment. Some contaminants are
considered fixed in the soil strata and subjected to move with soil such as erosion or
resuspension phenomena and to be removed mechanically for remediation. These fixed
contaminants might not be directly treatable by phytoremediation depending on their binding
status in soil. The interaction between contaminant and soil can be described by the equilibrium
distribution (or adsorption) coefficient (Kd), which is dependent on the physical and chemical
properties of the soil, liquid and contaminant, as shown by Equation 1.
Concentration of Contaminant in Soil	_
= 		Eq. 1
Concentration of Contaminant in Soil Water
The subsequent uptake by plant roots embedded in soil must occur through exchange of the
contaminant from soil to water. This relationship is controlled by the selectivity of the plant root
system, represented by the radionuclide plant to soil solution ratio (radionuclide activity, mass or
concentration per kilogram of dry weight plant tissue versus the contaminant activity, mass or
concentration per liter of soil solution), and referred to as the bioaccumulation factor (B AF), as
depicted by Equation 2.
„ . „	Concentration of Contaminant in Plant	_ ^
BAF = 		Eq. 2
Concentration of Contaminant in Soil Water
The reactions between contaminant, soil, water and plant tissue are in competition during
equilibrium, characterized by the concentration ratio (CR) as defined in Equation 3.
rn baf
CR = 		Eq. 3
Kd	H
The reverse process can also occur, with desorption from either soil or plant material to the soil
solution. Thus, in broad terms, phytoremediation effectiveness can be estimated based on known
values for the physicochemical properties of the soil, plant and contaminant. In this work, we
focus mostly on the equilibrium of radioactive contamination between soil, water and plant, with
the equilibrium processes schematically represented in Figure 1.
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Figure 1. Schematic figure showing
contaminant deposition and migration paths
A summary of the current state of radiological phytoremediation, providing general references
and prior literature reviews, pilot- and field- scale studies performed at contaminated sites in the
United States, former Soviet Union, and Japan and review of data relevant to the
phytoremediation of radiocesium (e.g., Cs-134 and Cs-137) is given in Section 2. Similar
datasets exist for plant uptake and phytoremediation of actinides (e.g., uranium, plutonium,
neptunium) and other fission products (strontium, iodine, cerium, niobium, zirconium, etc.). An
assessment of considerations and metrics for comparing available technologies with respect to
cost, application time, labor/expertise and supporting equipment needs, waste generation and
technical performance is given in Section 3, while recommendations and technical gaps in the
knowledge base are presented in Section 4.
1.1 Quality Assurance
The data in the reviews and evaluations met the data quality objectives by collecting them from a
combination of published, peer-reviewed journal articles, government reports (e.g., EPA, DOE,
DOD, UK Government, EU, Japanese Atomic Energy Agency [JAEA], International Atomic
Energy Agency [IAEA]) and industry/vendor information. By nature of their review by peers,
journal articles and some conference abstracts are considered trusted sources of information.
Similarly, reports published by government agencies such as EPA, U.S. Department of Energy
(DOE), U.S. Department of Homeland Security, and the Interstate Technology Regulatory
Council (ITRC) are considered highly trustworthy. International governmental reports were also
utilized, including those from the UK and European Union (EU) as well as the JAEA and IAEA,
particularly the reports relating to the response following the Fukushima and Chernobyl
contamination events.
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2. Radionuclide Ph y to rem cd ia tio n Literature Survey
Laboratory and field studies involving radionuclide uptake in soil and plants have been
performed for many years, beginning with understanding the impacts of nuclear testing on the
environment and food (e.g., Nishita, Steen and Larson, 1958; Middleton, 1959), which included
both actinide and fission product contamination. Plant uptake of radionuclide contamination
gained additional interest after the 1986 Chernobyl nuclear power plant accident, in which
radioactive contamination was spread across parts of the former Soviet Union and Europe. An
IAEA (1991) assessment of radiological consequences and evaluation of protective measures
following the release of radionuclides from the Chernobyl plant provides information on
protective measures and restrictions on food (including plants). In 1994, IAEA published a
handbook on parameters for the prediction of radionuclide transfer to plants, animals, marine
estuaries and food in temperate environments (IAEA, 1994). Similar to previously published
work, the IAEA document includes information on uptake of actinides and fission products, but
there is no mention in the report of the data being used for phytoremediation. It was not until the
mid 1990's that phytoremediation (which had previously been applied to cleanup of heavy metal
and organic solvent spills) was applied to radionuclide remediation.
2.1 General Published Guidance on Radionuclide Phytoremediation
Schnoor (1997) provided a technology evaluation report to the Ground-Water Remediation
Technologies Analysis Center detailing information on the use of innovative technologies to
clean up contaminated groundwater. In the 1997 report, Schnoor describes phytoremediation as
an emerging technology for contaminated sites that is attractive due to its low cost and
versatility, showing tremendous potential for treatment of shallow metal and organic
contaminants. Only two applied examples were given at that time for radionuclide application of
phytoremediation, specifically Cs-137 and Sr-90 pond water cleanup in the Ukraine using
sunflowers resulting in a 90% reduction in two weeks, and a demonstration in Ohio also using
sunflowers resulting in a 95% removal of uranium from waste water in 24 hours. Dushenkov
(PNNL, 1998) further reported that the Ohio study using sunflower-based pilot-scale
rhizofiltration system was successfully used at a former uranium processing facility, lowering
uranium concentrations in the site source water to below the target limit of 20 micrograms per
liter. In these applications, specific isotopes are not processed differently with phytoremediation,
but as long as it is chemically the same (for example, be it Cs-134 or Cs-137), the isotopes are
expected to be extracted with the same efficiency. Additional information on applied
phytoremediation is given in Section 2.3 of this work.
Proceedings from a 1998 international workshop in Ukraine on Chernobyl phytoremediation and
biomass energy conservation were published as a Pacific Northwest National Laboratory report
(PNNL, 1998). The report summarizes that preliminary tests of phytoremediation systems had
been established in highly contaminated areas of the Chernobyl exclusion zone, but that defining
objectives, implementing the technology and evaluating the various options would mean
optimum phytoremediation options would take at least an additional 5 years.
In addition to a significant number of peer-reviewed and published journal articles and early
technology reviews on the subject of radionuclide phytoremediation over the last 20 years,
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several high-quality literature reviews have been performed that capture both the uptake of
contamination in plants, and the state of phytoremediation research.
A prior literature review of phytoaccumulation of chromium, uranium and plutonium in plant
systems was reported in 1998 (Hossner et al.), which summarized the state of phytoremediation
science and provided examples of radioisotope phytoremediation applications. The EPA
published a phytoremediation resource guide (U.S. EPA, 1999) providing references to journal
articles, technical documents and websites that reported phytoremediation information for soil
and ground water. The report largely focused on organic solvent and heavy metal contamination,
with limited resources on radionuclide contamination beyond that of Hossner et al. (1998) and
Broadley and Willey (1997) who focused on cesium uptake in 30 different plants. In 2000, EPA
convened subject matter experts to discuss experimental and applied phytoremediation for
solvents, heavy metals and radionuclides (U.S. EPA, 2001). In 2005, NATO hosted a conference
on advanced science and technology for biological decontamination of sites affected by chemical
and radiological nuclear agents. The proceedings were subsequently published in Marmiroli,
Samotokin, and Marmiroli (2007), which included a paper authored by Soudek (2007) that
discussed cesium, strontium, iodine and radium uptake in plants.
In 2009, the Interstate Technology & Regulatory Council published their third technical and
regulatory guidance document on phytotechnology (ITRC, 2009). In addition to providing
comments and phytoremediation effectiveness for a variety of plants and radionuclides
(including cerium-144, cesium-134/137, cobalt-58, radium-224/226, ruthenium-106, strontium-
90, technetium-99 and uranium-238), the ITRC report also includes valuable information on
applied remediation project structure, site assessment, remediation strategy, plant selection,
design and implementation, operation, maintenance, monitoring, and site closure. While the
ITRC report was published in 2009, tabulated references related to radiological phytoremediation
are limited to those before 1998, presumably since the 2009 third edition combines prior ITRC
phytoremediation documents (ITRC, 1999; ITRC, 2001)1. However, ITRC (2009) remains one
of the most concise and comprehensive sources for phytoremediation planning purposes.
IAEA (2009) supplemented their 1994 handbook with a report on the quantification of
radionuclide transfer in terrestrial and freshwater environment for radiological assessment. With
a much larger dataset, this report represented a significant improvement in peer reviewed
literature data on the plant uptake of radionuclides. Also, in contrast to IAEA (1994), references
cited in IAEA (2009) include those that specifically evaluated radionuclide phytoremediation
(e.g., Vandenhove, Van Hees and Van Winckel, 2001; and Fuhrmann et al., 2002). The 1994
IAEA handbook was subsequently updated (IAEA, 2010) with the purpose of providing a very
extensive dataset, which encompass data from studies evaluating radionuclide uptake in plants
for both radiation protection and phytoremediation studies.
In 2012, IAEA provided guidelines for remediation strategies to reduce the radiological
consequences of environmental contamination. On the subject of phytoremediation, IAEA
(2012) stated that "until now, there has been no small- or large- scale adoption of this method at
existing sites for radionuclides. There are three main reasons why this option has not been
adopted: (i) the total amount of radionuclide removed from the soil is a very small fraction of the
1 ITRC https://www.itrcweb.ore/Guidance/ListDocuments?TopicID=20&SubTopicID=30 (accessed July 15th 2019)
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total radionuclide content present, even for those radionuclides with a comparatively high
transfer from soil to plant; (ii) the process would need to be continued for decades before the soil
became adequately decontaminated to be used for food production; and (iii) the option generates
waste which would then have to be disposed of appropriately, generating additional costs."
IAEA (2012) did not provide additional quantitative information on phytoremediation
effectiveness and plant uptake compared to IAEA (2010), which remains one of the most
comprehensive, quantitative and peer-reviewed broad data sets for radionuclide uptake in plants.
2.2 Literature Review of Radiocesium. Phytoremediation
There are numerous examples of laboratory-scale cesium phytoremediation studies on a wide
variety of plants and soils; several examples (not intended to be an exhaustive list) are provided
in this section. Additional references and observations on cesium phytoremediation can be found
in ITRC (2009). Published works by Entry studied the uptake of Cs-137 and Sr-90 in ponderosa
pine and Monterey pine (Entry, Rygiewicz and Emmingham, 1993, Adriano et al., 1995), as well
as in Alamo switchgrass (Entry and Watrud, 1998). Broadley and Willey (1997) studied Cs-137
uptake in the shoots of 30 plants, noting that there were maximum differences between quinoa
and junegrass of 20-fold in cesium concentration and 100-fold in total cesium accumulated.
In the late 1990's, work was performed at the USDA-ARS [Agricultural Research Service] Plant,
Soil and Nutrition Laboratory (Ithaca, New York) in support of a phytoremediation concept later
to be deployed on contaminated land at the Brookhaven National Laboratory (Upton, New
York). Lasat, Norvell and Kochian (1997) studied Cs-137 uptake on contaminated soil using
Indian mustard, arcadia, a commercial variety of broccoli, cabbage and cauliflower, kochia,
tepary bean, hairy vetch, colonial bentgrass, red fescue and reed canary grass. The results
suggested that phytoremediation of Cs-137 contaminated soil was feasible. Later, Lasat et al.
(1998) also studied uptake in root pigweed and continued studies with Indian mustard and tepary
bean, finding that redroot pigweed is a plant with high potential for extraction of Cs-137 from
contaminated soils. Lasat et al. (1998) also evaluated the impact of ammonium nitrate fertilizer
on the uptake of cesium in Indian mustard, redroot pigweed and tepary bean, finding that the
ammonium ion has the potential to desorb Cs-137 ions from the soil minerals, but did not
enhance Cs-137 bioaccumulation perhaps because of competition for binding sites. Work on
contaminated soil from the Brookhaven National Laboratory continued to include redroot
pigweed (Fuhrmann et al., 2002) and Powell's amaranth (Fuhrmann, 2006).
Sandeep and Manjaiah (2007) evaluated the transfer factors of Cs-134 in mustard, gram, spinach
and wheat crops in semi-arid, tropical climate, finding that transfer factors were highest in
spinach, with mustard and gram much higher than that of wheat. Sadhasivam, Pitchamuthu and
Ayyavu (2010) studied Cs-137 phytoextraction in the presence of ammonium chloride fertilizer
using amaranthus, maize, cowpea and sunflower, finding that amaranthus bioaccumulation was
superior. Djedidi et al. (2014) studied both the uptake of stable cesium in komatsuna, amaranth,
sorghum, common millet and buckwheat, together with the effect of inoculation with Bacillus
and Azospirillum on komatsuna, which resulted in the greatest transfer factors, suggesting that
the addition of bacteria can enhance bioaccumulation. Dan et al. (2015) studied phytoextraction
of stable cesium using Amaranthus mangostanus L., finding that the chlorophyll content in the
amaranth initially increased and then decreased with the increasing cesium content in the soil.
The results suggest overloading (leading to a decrease in uptake) can negatively impact plant
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photosynthesis and hinder plant growth. Fukuda et al. (2014) performed a search of 188 strains
of algae and aquatic plants that could eliminate cesium, strontium and iodine from contaminated
water, finding that the algae Eustigmatophyceae, Florideophyceae and Chlorophyta and the
plant Tracheophyta yielded the greatest ability for removing Cs-137 contamination from
freshwater within 8 days of contact.
The inclusion of fermented bark amendment was found to accelerate cesium uptake in rice plants
(Sun et al., 2019), possibly due to a reduction in the oxidation potential in soil. The addition of
ammonium sulfate fertilizer further increased the bioaccumulation factor in rice straw. Sun notes
that increased cesium availability was due to exchange with ammonium ions within the soil.
Thus, the application of both fermented bark and fertilizer should be considered in
phytoremediation strategies. Statistical approaches have also been used to evaluate
bioaccumulation of contaminants. Willey, Tang and Watt (2005) used analysis of variance
(ANOVA) and residual maximum likelihood to predict inter-taxa differences in Cs-134 and Cs-
137 plant uptake. In general, their findings were that Eudicots, and especially the
Caryophyllales, Asterales, and Brassicales, had high cesium uptake concentrations, while the
Fabales and Magnoliid.v, in particular Poales, had low cesium uptake concentrations, noting that
plant phylogeny and growth strategy might thus be used to predict a significant portion of inter-
taxa differences in cesium plant uptake. Such an approach may be extremely helpful in
determining plant species for phytoremediation studies when considering plants that will both
thrive and behave as radionuclide hyperaccumulators.
2.3 Applied Radiological Phytoremediation: Pilot- and Full- Scale Studies
In the mid 1970's, dredging of the contaminated Interceptor-Canal at the Argonne National
Laboratory (ANL) West (Idaho Falls, Idaho) site resulted in a mound of soil contaminated with
30.53 pCi/g of Cs-137. DOE evaluated 5 options for remediation, including (i) no action, (ii)
limited action, (iii) containment with institutional controls, (iv) excavation/disposal, and (v)
phytoremediation. Subsequently, DOE submitted a proposal to utilize phytoremediation to
reduce Cs-137 contamination in the Canal-Mound. A pilot/field-scale effort began in 1999 with
the goal of reducing Cs-137 contamination to 23.3 pCi/g (U.S. EPA, 1998). Through planting of
Kochia scoparia over 0.61 acres, the project was completed in 2002 after Cs-137 levels fell to
6.54 pCi/g (U.S. EPA, 2005). Irrigation, fertilization, pest control and harvesting were required
during the project duration. Harvested plants were sampled, compacted and shipped for
incineration to reduce waste volume before being sent to a permitted landfill (U.S. EPA, 1998).
In 1998 USD, the phytoremediation cost estimate was $3M, compared to $9.0M for containment,
$6.6M for excavation and INL disposal, and $13.4M for excavation and private facility disposal
(U.S. EPA, 1998).
ANL East (Lemont, Illinois) began full-scale phytoremediation efforts on four acres of their Area
317/319 site in 1999 to treat soil and groundwater contaminated with a mixture of chlorinated
hydrocarbons, heavy metals and tritium (U.S. EPA, 2005) using a combined approach of
hydraulic control, phytoextraction, phytostabilization, rhizodegradation and phytodegradation
with a variety of plants including hybrid poplar, eastern gamagrass, golden weeping willow,
hybrid prairie cascade willow and laurel-leaved willow. The full-scale efforts required
8

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fertilization, replanting and significant health and safety aspects (due to hazardous and
radioactive material concerns) increased cost and difficulty in application.
A phytoremediation investigation at DOE's Savannah River Site (SRS) published by Murphy
and Tuckfield (1994) describes a study of transuranic (americium, neptunium and plutonium)
contaminant uptake in native loblolly pine, sweet gum, and willow oak planted above the unlined
Low-Level Burial Ground in 1978 with a goal of returning the site to general public access. The
study, which evaluated contaminant uptake in the tree seedlings, grown trees, leaves and needles
over the subsequent years, found that there was more Pu-238 uptake by pine tree seedlings
compared to sweet gum and willow oak. Additionally, the study found that transuranic uptake in
grown pine trees occurred to a greater extent than in seedlings, and that transuranic uptake in
pines was higher on the Low-Level Burial Ground compared to a control plot. The study
therefore indirectly demonstrated the feasibility of native plants as phytoremediation
accumulators, with uptake activities of 0.088 Bq/kg for Am-241 (transport of 320 Bq/ha/year),
0.48 Bq/kg for Np-237 (transport of 1,900 Bq/ha/year), 0.79 Bq/kg for Pu-238 (transport of
2,800 Bq/ha/year), and 0.09 Bq/kg for Pu-239 and Pu-240 (transport of 240 Bq/ha/year).
Murphy and Tuckfield (1994) also projected transuranic uptake in food grown in soil after 100
years of phytoremediation using barley, pea, bean, soybean, wheat and tomato.
In 2000, full-scale phytoremediation efforts began at the SRS Radioactive Waste Burial Ground
Complex with tritium contaminated groundwater at approximately 500 pCi/mL. Naturally
forested areas of sweet gum, loblolly pine, slash pine and laurel oak were utilized approximately
25 acres with a combination of hydraulic control and enhanced evapotranspiration. Blount et al.
(2003) describes the process as one that dilutes tritium concentrations while absorbing
approximately 60% of tritium (H-3) in biomass, exchanging the remaining approximately 40% in
hydrogen atoms in water molecules, and evaporation of tritium-containing water in the plant
system to the atmosphere. In addition, a dam was constructed to contain surface discharge of the
tritium contaminated groundwater. Blount's calculations predicted a maximum fixed activity of
30 pCi/g occurs in less than 10 years, with fixed activity reaching the federal Primary Drinking
Water Standard of 20 pCi/mL if the tree is harvested 15 years after irrigation began. As of 2004,
approximately 133 million liters of irrigation has prevented 1,800 Ci H-3 from entering a nearby
river, with levels between 2004 and 2014 typically below 100 pCi/mL (Hitchcock et al., 2005).
No cost information was available.
In 2006, laboratory-, greenhouse- and pilot-scale phytoremediation studies were initiated to
address groundwater at DOE's Hanford site (Benton County, Washington) with approximately
3,000 Ci Sr-90. Groundwater contamination of approximately 8 pCi/mL in the 100-N Area and
along the 100-N Area Columbia River shoreline originated from two liquid waste disposal
facilities operated from 1963 to 1991. This effort used native coyote willow stems that were
subsequently harvested by cutting at 10 to 20 cm above the ground twice a year and monitoring
was performed on a monthly basis. The studies indicate that coyote willow could function as a
successful phytoextractant of Sr-90 (Ainsworth, 2006; Fellows, Fruchter and Driver, 2009; and
Fellows et al., 2010). Fellows et al. (2010) estimated that a total of 7.7 metric tons of biomass
would yield a removal rate of about 16 mCi of Sr-90 per year, with an initial specific activity of
2,100 pCi/g of biomass. The initial project costs were estimated at $433,000 (Ainsworth, 2006).
9

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2.3.2	Post-Chernobyl Applied Phytoremediation
The Chernobyl nuclear power plant (NPP) accident in the Ukraine released radionuclides with a
total activity estimated at 1,900 PBq (50 million Curies), including approximately 19 PBq Cs-
134 and 38 PBq Cs-137 (IAEA, 1991) in 1986. Several phytoremediation studies have been
performed, ranging from the contaminated exclusion zone to other countries that experienced
land contamination as a result of the plume. Sorochinsky (PNNL, 1998) reported results from
laboratory and field studies performed in 1995 and 1996 using sunflower, Indian mustard and
pea plants within the Chernobyl exclusion zone, finding that all three plants were successful in
rhizofiltration studies to remove both Cs-137 and Sr-90. Sorochinsky also suggested that the
technology of short-rotation forestry may be successfully introduced in the Chernobyl exclusion
zone, for example fast-growth clones of poplar and willow, which typically have a rotation every
6 to 7 years and have a high density of 1,000 plants/ha, producing between 10,000 to 20,000 kg
of dry biomass/ha/year. Dushenkov et al. (1999) studied phytoremediation of Cs-137 in 20 plant
species installed on a loam/sand soil experimental plot of heavily contaminated land at the
northwest boarder of Chernobyl, finding that several species of amaranth possessed promising
bioaccumulation coefficients, with bioaccumulation coefficients ranging from 0.53 to 2.03.
Victorova et al. (2000) performed Cs-137 and Sr-90 phytoremediation studies on the west bank
of the river Pripyat and in Yanov (Ukraine), in sandy contaminated soil using natural willow,
resulting in radiocesium transfer factors ranged from 10 4 and 10 3 m2/kg. Highest uptake was
observed in plants that were 7 to 8 years old as compared to younger 1 to 2-year-old plants.
IAEA (2012) noted that until recently, no small- or large-scale adoption of phytoremediation had
been successful at existing contaminated sites in the former Soviet Union. IAEA cited three
reasons for a lack of phytoremediation adoption to address contaminated land, including the
relatively small fraction of total radionuclides removed from soil in comparison to the high
values in soil, the long-term nature of phytoremediation given the scale of contaminated land,
and the biomass disposal options and costs. Paramonova et al. (2015) studied the root uptake of
spring barley, maize, summer rape, galega, potatoes and amaranth in ecosystems of dry and wet
meadows in the Tula region, Russia. The findings showed that galega and amaranth could be
considered for phytoremediation, since 87-93% of Cs-137 inventory is located in shoots.
However, meadow grasses and cereals appeared to not be feasible phytoremediation species due
to 86-97% of the contamination being associated with roots remaining in soil after removal of
shoots.
2.3.3	Post-Fukushima Applied Phytoremediation
The March 2011 Fukushima Daiichi NPP accident resulted in radionuclide releases on the order
of 10,000 PBq (270 MCi), with between 8 and 50 PBq (-200 kCi to 1,300 kCi) of Cs-134 and 7
to 20 PBq (-190 kCi to 540 kCi) of Cs-137 (IAEA 2015). For two seasons in 2011 and 2012,
Terashima, Shiyomi and Fukuda (2014) examined Cs-134 and Cs-137 levels in grassland 32 km
northwest of the Fukushima Daiichi NPP, including timothy, orchard grass, perennial ryegrass
and clovers as well as soil. The results showed that the level of radiocesium in the biomass
increased over the two years, with 97% of the contamination present in the top 5 cm of soil, but
that concentration ratios were lower in 2012 compared to the initial spike in 2011. Yamashita et
al. (2014) estimated the soil-to-plant transfer factors of radiocesium in 99 wild plant species
grown in contaminated arable lands in the Fukushima Prefecture one year after the Fukushima
NPP accident. Some species (e.g., Athyriumyokoscense, Dryopteris tokyoensis, and Cyperus
brevifolius) exhibited relatively high concentration ratios, while others (e.g., Salix miyabeana,
10

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Humulus scandens, and Elymus tsukushiensis) exhibited almost negligible values. Yamashita
concluded that the weed community is not a practical candidate for phytoremediation techniques.
Sugiura et al. (2016) evaluated Cs-134 and Cs-137 in new leaves of wild plants two years after
the Fukushima Daiichi NPP accident. The results showed that woody plants exhibited high
concentration ratios resulting from deposited Cs-137 on above-ground portions of plants
transferred to new plant tissue. Additionally, Sugiura found that concentration ratios in 2012
decreased compared to those measured in 2011, with concentration ratios ranging from 1.3 to 54
for herbaceous species and 3.6 to 30 for woody species during the first year. Interestingly,
Sugiura also notes that species previously identified in other studies as being cesium
hyperaccumulators in this case showed no clean Cs-137 accumulation ability. Rather, the
perennial plant Houttuynia cordata (chameleon plant) and deciduous trees Chengiopanax
sciadophylloides and Acer crataegifolium displayed high concentration ratio (CR) values, which
may be considered better options for phytoremediation. In laboratory experiments, Tamaoki et
al. (2016) evaluated amaranthus, chamomile, cherry sage, cockscomb, hollyhock, ice plant,
Indian spinach, kochia, okra, reed, rumex, salvia, scarlet rose mallow, sunchoke, sunflower and
tomato cultivated in soil removed from contaminated land as a result of the Fukushima Daiichi
NPP accident. The results showed that the plant biomass is a significant contributor to the
uptake of Cs-137 and that kochia showed the most favorable results for phytoremediation
applications.
Fifty-six local Japanese cultivars of field mustard, Indian mustard and rapeseed were assessed by
Djedidi et al. (2016) for variability in growth and Cs-137 uptake and accumulation in association
with a Bacilluspumilus strain, applying research from Djedidi et al. (2014) to field studies on
contaminated farmland in Nihonmatsu city, in Fukushima prefecture. B. pumilus induced a
significant increase in shoot dry weight in 12 cultivars that reached up to 40% in one field
mustard and three Indian mustard cultivars. Soil to plant Cs-137 transfer ratios varied by a factor
of 5 depending on species and inoculation. Aung et al. (2016) measured Cs-137 uptake plants
and soils from contaminated areas in Japan, also showing that inoculation with Bacillus pumilus
led to an increase in root volume and a subsequent increase in the transfer of Cs-137 from soil to
plant.
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3. Technical Considerations for Radiological Pliyto remediation
The use of phytoremediation in the removal of radiological contamination requires consideration
from subject matter experts and stakeholders at each stage, from species selection, planting and
ground preparation to maintenance, removal and waste disposal. Dushenkov (PNNL, 1998)
identified the key factors determining the effectiveness of phytoextraction:
•	Plant characteristics
•	Planting density
•	Fertilizer and amendment effectiveness
•	Soil characteristics including type, pH, electrical conductivity and mineralogy
•	Climate
•	Total soil radionuclide concentration
•	Metal solubility and species distribution
For rhizofiltration, Dushenkov (PNNL, 1998) suggests the factors determining effectiveness are:
•	Root production
•	Metal concentration in solution
•	pH
•	Temperature
•	Root density and plant age
Soil characteristics and rhizosphere chemistry will impact the diffusion of contamination through
the soil and the interaction between the contaminant and the soil. Clay soils are more likely to
show a higher tendency to bind cesium compared to sandy or loam soil due to a high affinity for
cesium in clay mica layers, in which the reaction is almost irreversible and making
phytoremediation difficult even for hyperaccumulators. Similarly, the chemical environment
imparted by the soil on the contaminant can (in most cases) change its behavior. The pH and
chemical composition of rhizosphere water, which is governed by the soil chemistry, fertilizer
and amendments. In the case of amphoteric ions of elements such as uranium and plutonium
whose chemical speciation, ionic charge and solubility changes drastically depending on local
chemical conditions and causes significant differences in bioaccumulation. In the case of cesium
contamination, local changes in pH or soil chemistry impact the soil's ability to bind
contamination, and the plant biochemistry far more than the chemistry of cesium itself. As
already discussed, the application of potassium fertilizers can enhance plant health and growth
but can also compete with cesium for binding sites within the plant, lowering cesium
bioaccumulation.
Regarding the limitations of phytoremediation, Schnoor (1997) notes difficulty accessing
contaminants deeper than 3 meters, uptake of contaminants into leaves, inability to meet
decontamination action levels in a short period of time, safety implications for accessing
contaminated areas and vegetation at the site, and possible migration of contaminants off-site.
Schnoor (1997) suggests that phytoremediation may serve as a final "polishing step" to close
sites after other clean-up technologies have been used to treat the hot spots, and that winter
operations may pose problems for phytoremediation when deciduous vegetation loses its leaves,
transformation and uptake cease, and soil water is no longer transpired.
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3.1 Plant Selection and Technical Performance
The most important factor in phytoremediation is the selection of the plant species. However, as
highlighted in this work, the ability of a given plant to extract contaminants from contaminated
soil or water is not the only factor in plant selection. Biomass health and production is also an
important factor in plant selection. According to Soudek et al. (2007), the most critical plant
property for remediation of radionuclide contamination is a high growth rate and the ability to
generate large amounts of biomass in a given environment. Additionally, Soudek notes that for
soil cleaning purposes, the solubility of the contaminant and its mobility in soil are the most
limiting factors along with the extent of the soil volume exploited by the roots of the remediating
plant species.
Substantial data exist (IAEA, 2010) on Kd values for radionuclide/soil interaction, migration
rates for Cs-137 and Sr-90 for a variety of case studies, and soil-to-plant transfer factors for a
significant number of elements and plant groups divided between soil types. The information
can be used to calculate the contaminant transfer vertically from surface deposition to soil
interaction and subsequent plant uptake, ultimately providing an estimate of bioaccumulation and
thus the viability of phytoremediation for broad plant species in a range of soils for elements and
radionuclides of interest to this work. The purpose of the IAEA report was to provide data for
use in the radiological assessment of routine discharges of radionuclides to the environment and
primarily for the use in risk assessment. However, the broad grouping of soil types and plant
species in IAEA (2010) prove of limited use when considering phytoremediation plant selection.
For example, when considering cesium binding in clay and loam soil, IAEA (2010) provides a
mean Kd value of 3.7 x 102 with a range that differs by 4 orders of magnitude. Similarly, for
cesium in sandy soil, a mean Kd value of 5.3 x 102 is provided with a range of values that differ
by more than 3 orders of magnitude. Soil-to-plant transfer factors are also given in IAEA
(2010). For cesium uptake in the grain of cereals, transfer factors of 1.1 x 10"2 and 3.9 x 10"2 are
provided for clay and sandy soil, respectively, together with a range that differs by 2 orders of
magnitude. It is important to note that IAEA (2010) information is extremely useful for risk
assessment and offers boundary conditions for phytoremediation, but plant screening and
selection needs to include published literature studies and values, particularly since soil
conditions, chemistry, experimental duration and field versus laboratory conditions vary from
study to study.
When selecting plant species for phytoremediation, the plant's ability to grow and survive in the
environment and climate in which the contamination is present is important. Plants that do not
typically grow or flourish in non-native environments will create a challenge for
phytoremediation applications without amendments such as fertilization and irrigation. ITRC
(2009) provides the following five options in regard to plant selection during the initial planning
stages of phytoremediation applications, assuming the site has been first characterized:
1.	species found in phytotechnology databases and growing at the site
2.	species found in phytotechnology databases and suitable to the region, but not currently
growing on the site
3.	hybrid or species related to a plant identified as a candidate in above bullets
4.	species not found in the databases but currently growing at the site or in the region
5.	genetically modified organism species designed specifically to conduct the desired
phytotechnology
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Furthermore, ITRC (2009) suggests that general operability factors such as growth rate, habit
(perennial, annual, biennial, deciduous, evergreen), form (grass, herbaceous, shrub, tree, etc.),
ability to reach desired depths, water usage, disease/pest resistances, and tolerances should also
be considered when selecting phytoremediation species. ITRC recommends generating a list of
native plants or obtaining input from local agricultural specialists. Hybrid plants offer additional
benefits over already in-situ plant species, such as increased biomass production, disease-, pest-
and climate-resistance. For these reasons, ITRC (2009) states hybrids such as from poplar and
willow have been extensively and successfully used in phytoremediation applications. Several
decision-trees on phytoremediation application are provided by ITRC (2009), allowing the
determination of techniques best suited to both the contaminant and contaminated media. While
seasonal variations should be considered when selecting plant species, ITRC (2009) notes that a
mix of warm and cool seasons can be considered in the initial phytoremediation planning, if
phytoremediation will span multiple seasons.
When phytoremediation plant species are not already present at the contaminated site, or not
enough plant mass is present, new or additional plants must be added. This represents challenges
to cost, application time and safety, which not only depend on the number of plants needed, but
the area to be cultivated and whether plants are added as seed or rooted plant stock. For seed
application, ITRC (2009) notes that advantages include lower cost of stock, easy installation by
general labor and simple storage and transport, while disadvantages include lower success of
establishing root and coverage at the site, and the risk of predatory removal from the site.
Similarly, for root stock, ITRC (2009) notes advantages of higher survivability, quicker
remediation effects, while having higher installation cost, time and labor, requiring more
complex storage, transport and planting expertise. Comparatively, ITRC (2009) notes that the
cost of bare root stock is generally less than that of potted stock by approximately 25%, but that
both are more costly than seed.
3.2 Labor, Expertise and Supporting Equipment
In the event of wide area contamination and the need for phytoremediation, labor, expertise and
supporting equipment will come from a variety of sources, including local, state and federal
governments, industry, academic and community volunteers at each stage of the process, from
planning and land preparation, to maintenance, harvesting and waste management. Guidance in
ITRC (2009) suggests creating a project team to plan and implement phytoremediation, generally
including the following positions:
•	Project Manager
•	Radiochemist
•	Soil Scientist/Agronomist
•	Hydrologist/Geologist
•	Plant Biologist/Botanist
•	Environmental Scientist
•	Risk Assessor/Toxicologist
•	Regulatory Specialist
•	Environmental Engineer
•	Field Manager/Health, Safety and Environmental Officer
•	Cost Engineer/Analyst
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For radiological phytoremediation, substantial emphasis should be placed on hydrology and
environmental science to prevent the migration of contamination, on health physics to maintain
worker safety, and on waste strategies to minimize environmental and financial impacts of
resultant waste. Staffing levels will depend on the scale of the radiological phytoremediation
efforts, as well as the desired schedule to complete preparation, planting, removal and waste
management.
Contamination covering a wide area will require a substantial amount of planting if
phytoremediation is to be used effectively in removing radionuclides. Land may need to be tilled
before planting occurs, and contaminated vegetation will need to be removed after
phytoremediation has been completed or after a plant die-off In these cases, given the scale of
phytoremediation likely necessary in a wide area event, mechanical methods will be preferred.
Traditional farming equipment to till land can be utilized. Resources could be provided by local
farmers, machine rental or supply companies or manufacturers. Farming equipment will require
decontamination after working in radiologically contaminated environments. In the
phytoremediation pilot study at ANL-W, $10,000 of farming equipment was purchased and
procedures were considered both labor and irrigation intensive (U.S. EPA, 2001). Planting
mechanisms for phytoremediation purposes will depend on type and maturity of species,
topography and area to be covered. Some plant species would be more amenable to mechanical
planting, with others may require hand-planting. Similarly, plant maturity will dramatically
impact the planting method, with seeds being easier to mechanically disperse and plant compared
to already-established plants with existing root structures. Topography will also impact the
ability to use mechanical methods for planting, with relatively flat surfaces easier than hillside,
depending on gradient. Similarly, mechanical removal of vegetation at the end of the
phytoremediation lifespan of plants will be dependent on type and maturity of species,
topography and land area covered.
Schnoor (1997) states that planting density depends on the specific application, providing
specific information on poplar trees, hardwood trees and grasses. Poplar hybrids can be
accommodated at 1000 to 2000 trees per acre and are typically planted with a conventional tree
planter at 12 to 18 inches depth or in trenched rows one to six feet deep. Hardwood trees and
evergreens may require a lower planting density initially. A high initial planting density assures a
significant amount of evapotranspiration in the first year, which is normally desirable. Grasses
are usually drilled or broadcast for planting at waste sites. Biomass densities (above ground) of
200 to 600 g/m2 are achieved by the second crop, with 1 to 3 crops per year depending on
climate and water availability. The initial planting density of aquatic species in a created or
natural wetland is normally three plants to a pod, located on three-foot centers. Schnoor (1997)
also recommends the inclusion of replanting and maintenance costs in the estimated budget, with
at least 30 percent of the plants potentially needing to be replanted in the second or third year, as
a contingency. A general rule of thumb for a preliminary phytoremediation design, according to
ITRC (2009), should include a planting density of 75 square feet per tree, staggered with an
average of 10 feet on-center with a 5-foot radius of fill to create a full canopy with adjacent trees.
In some cases, irrigation may be needed to maintain plant growth and health, particularly in the
case of non-native plants, or heavy planting of native plants on the contaminated site. Schnoor
(1997) states that for terrestrial phytoremediation applications, it is often desirable to include
irrigation costs in the design, on the order of 10 to 20 inches of water per year, noting that
15

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irrigation of the plants ensures a vigorous start to the system even in a drought. However,
irrigation can lead to potential for migration of contaminants from the original site, requiring
hydrologic modeling to maintain the source-term boundary. Schnoor (1997) recommends
withdrawal of irrigation from the site over time provided local precipitation is sufficient to
maintain plant health and growth.
In addition to sunk costs such as site assessment, literature review and feasibility studies, ITRC
(2009) provides optional cost items specific to phytotechnologies including capital, engineering
and design, labor and operation, and maintenance considerations for both groundcover and tree
systems. Capital costs include earthwork, soil amendments, seed or root stock, site and plant
protection systems, and irrigation systems, among others. Engineering and design costs should
include those related to site planning, planting density and irrigation systems. Labor costs (in
addition to planting) should also consider plant litter collection, spot reseeding or replanting, and
expertise in determining plant health. Operating and maintenance costs should include irrigation
water and electrical supply if needed, fertilizers and other amendments, invasive plant or pest
control, local meteorological station, soil, plant and water sampling supplies and subsequent
analysis, and transportation and disposal costs. Clearly, the cost of each item is very much site-
specific.
Radiological contamination of soil, plants and equipment must be considered in all phases of the
process, from land preparation, planting and irrigation, to vegetation removal, transport, and
disposal. Workers will need to be trained and/or qualified on mechanical operations. At a
minimum, training on the properties of radiological contamination and personal protection
equipment (PPE) should be provided. Radiological field technicians can provide support for
monitoring personal contamination. In reality, labor and expertise might be provided by both
those experienced in farming and those with professional radiological worker qualifications.
This will likely increase costs relative to other types of contamination, and potentially slow the
process of evaluating and removing contamination. Additionally, mechanical equipment will
likely require decontamination, generating additional waste. According to EPA (U.S. EPA,
2019), technologies and methods that are employed in other situations/applications (e.g., U.S.
DOD, USD A) should serve as a starting point, and important insights can be gained by
examining technologies and procedures developed by USD A to clean non-radiological
contaminated farm vehicles and by DOD to decontaminate military vehicles/planes, in addition
to recent experiences in Japan.
Schnoor (1997) provides 3 examples from other authors regarding remediation cost, showing
that the 5-year cost for phytoremediation using hybrid poplar trees ($250k) compared favorably
to that using pump and treat methods ($660k). In another example, while phytoextraction
requires a longer duration compared to fixation, landfill or soil extraction/leaching methods
demonstrated for metal contaminants, the costs are approximately $15 to $40 per cubic meter of
soil, an order of magnitude less compared to other techniques.
A detailed cost estimate for phytoremediation of DOE's Argonne West site (Idaho) was
presented in EPA (U.S. EPA, 1998), summarized below. The assessment shows significant cost
savings through the utilization of phytoremediation, mostly in the management, construction and
operation/maintenance costs.
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Estimated Cost of Remediation Options for ANL-W Site (I c EPA, 1998)

('oiiiaiiimcnl
l-'.\ca\alion wiili on-
site disposal
Plnloremeriialion
Management
$l,527k
$l,232k
$528k
costs



Documentation
$126k
$128k
$98k
package



Construction
$4,963k
$4,438k to $4,593k
$l,623k
Operation and
$2,347k
$780k
$780k
maintenance



Total
$8,963k
$6,578k to $6,733k
$3,029k
3.3 Generation and Management of Waste
Management of wastes resulting from a disaster or incident (including those from NPP accidents
and RDD releases) is a significant part of EPA's Emergency Support Functions responsibilities
as outlined in the National Response Framework (U.S. DHS, 2016). The workshop
(Jablonowski et al., 2011) sought stakeholder input on their questions and concerns regarding
waste management following a hypothetical wide area RDD release, with broad reoccurring
areas or themes (all of which apply to the management and final disposition of waste generated
from phytoremediation activities, including:
•	Regulatory restrictions/agreements/exceptions
Are necessary agreements in place to expedite waste handling?
Can disposal in non-radiological waste facilities be considered?
What is the response framework?
Who is in charge and what do they expect from the private sector?
Are potential waste accepting facilities willing to accept the wastes if permission
can be granted by the relevant regulatory agency(ies)?
•	Scientific/technological
What is an acceptable cleanup level for free release of sites or material?
How will appropriate decontamination technologies be deployed?
What is an acceptable level of contamination for alternate disposal in solid or
hazardous waste landfills?
Waste disposition jurisdiction
How will regional low-level waste compacts be involved?
Can DOE disposal sites be considered?
What agency is ultimately responsible for decision-making and paying for
disposal?
Is it feasible to build a landfill using RCRA Subtitle C technological
specifications, potentially on government-owned land, for managing waste
specifically from the incident?
•	Ultimate disposition capacity
Is there sufficient disposal capacity to manage a large radiological incident?
What is necessary to provide adequate temporary storage or staging?
Is there local disposal capacity for the low activity waste so that only the waste
with the higher activities would need to be sent to the low-level radioactive waste
(LLRW) repositories?
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•	Communications
How can the public's concerns regarding storage, transportation, and disposal be
addressed?
The results of the 2011 workshop (U.S. EPA, 2012) found that landfill operators that expressed
unwillingness to accept incident-related waste in their own facilities might be willing to operate a
government-owned landfill. In regard to waste generated from phytoremediation throughout the
lifetime of the project, the following stages will generate waste:
•	Test beds to select plants and methods
•	Land preparation
•	Planting
•	Irrigation and maintenance
•	Vegetation removal
Waste generation and associated costs for laboratory scoping studies are well established by
routine experiments performed at universities, government agencies, national laboratories and
remediation contractors. In these cases, waste generally can be categorized as LLRW. Some
segregation into municipal waste can be performed to reduce the volume of LLRW generated.
Similarly, PPE generated at all stages of the process may be segregated into municipal and
LLRW. However, the waste generated from wide-area contamination (and subsequent large-area
phytoremediation efforts) will be on a scale far greater than that experienced by industry,
academia or government agencies, as demonstrated by efforts following both the Chernobyl NPP
and Fukushima Daiichi NPP releases.
Waste generated from planting of vegetation for radionuclide phytoremediation will depend on
the method of planting, either mechanical or manual. In both cases, contaminated PPE will be
generated. For mechanical planting, equipment will need to be surveyed to determine the extent
of contamination and whether disposal of contaminated equipment will occur or whether
decontamination will result in additional waste. By far the largest fraction of waste generated
outside the Fukushima NPP fence-line in Japan is from contaminated soil and vegetation (U.S.
EPA, 2016), where the top six inches of soil was removed, and vegetation was trimmed to
remove contamination deposited on plant surfaces such as leaves and branches. Selective
vegetation removal was performed by hand in Japan, but larger-scale complete removal was also
performed using mechanical methods such as excavators. Manual removal did not require
expensive tools or skilled labor. Larger-scale removal required personnel experienced in
mechanical operations and also resulted in soil removal as well as vegetation, creating larger
waste volume. Vegetation may be washed, or a suppression spray may be used, to prevent
airborne resuspension of contaminants (U.S. EPA, 2013).
Contaminated vegetation may undergo three different general paths for disposal. The most basic
path is to bury untreated contaminated vegetation in large underground pits. Pits should be lined
with impermeable material to prevent water ingress and subsequent migration of contamination
outside of the pit boundary. This option results in a large volume of waste relative to other paths,
in which costs associated with excavation, pit lining, waste containerization, transport and pit
maintenance are highest. Shredding and compaction will help reduce volume of vegetation
slightly. The remaining two paths involve treatment to minimize waste volume by separating the
contaminant from the plant material by either chemical or physical means. Leaching of
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radioactive contamination from vegetation can reduce the volume of vegetation destined for solid
LLRW disposal. However, this leaching requires the use of chemicals that can add additional
waste streams including liquid waste and potentially mixed hazard waste, which are both
problematic and expensive to manage.
According to Efremenkov (1989) and EPA (U.S. EPA, 2014), incineration has become a largely
effective and efficient process at nuclear power plants for waste streams that have a combustible
component, but further improvements are needed such as control of ultra-fine particles.
Incineration can allow 50-80% or more of a solid radioactive waste to be burned efficiently,
greatly reducing the volume of waste. Incineration of biomass also significantly reduces waste
volume but must be administered carefully to prevent further atmospheric release and spread of
contamination.
Remediation efforts in Dushenkov (PNNL, 1998) suggest that compared to excavation of 10
acres of contaminated land (resulting in 30,000 tons of waste), phytoremediation would produce
approximately 1,200 tons of biomass that could be further reduced to around 120 tons of ash
after incineration. Kalb and Grebenkov (PNNL, 1998) reported that in excess of 100,000 tons of
ash (including soil and vegetation) with an activity up to 50 kBq/kg had been accumulated in the
two years following the Chernobyl NPP accident, reporting that the safe collection, treatment
and disposal of contaminated hearth ash is therefore a serious health issue in Belarus. According
to Marmiroli, Samotokin, and Marmiroli (2007), a reasonable cost estimate to site incineration is
about $28 per metric ton for large sites of several hundred to several thousand tons of waste
generated.
In collaboration with DOE, Kalb and Grebenkov (PNNL, 1998) reported the feasibility of
reduction in the volume of radioactively contaminated ash and the use of thermoplastic
encapsulation technologies to stabilize contaminated ash. Waste loadings of 40-50 wt% were
demonstrated without reaching maximum processing limits, and a pilot-scale feasibility test
using low-density polyethylene encapsulation demonstrated waste loadings up to 70 wt%.
By 2015, an estimated 7.8 million cubic meters of combustible waste (mostly in the form of
vegetation) had been generated following the Fukushima Daiichi NPP accident (Osako, 2015).
A review of remediation technologies is presented by EPA (U.S. EPA, 2016) and includes a
variety of incineration technologies that have been demonstrated in Japan. These include
advanced off-gas treatment, transportable carbonization, superheated steam carbonization,
mobile air-cooled furnace, and low temperature incineration. An approximate volume reduction
rate of 95% was achieved by incineration and thermal decomposition. In Japan, fly ash with an
activity less than 100 kBq/kg resulting from incineration was sent to a controlled landfill site
monitored by the government. Ash greater than 100 kBq/kg is stored in the interim storage
facility before being moved to a long-term permanent disposal facility (U.S. EPA, 2016).
Emissions of particulate-bound radioactive isotopes such as Cs-137 from combustion systems
can be undesirable (Parajuli et al., 2013). The resulting fly ash from incineration can undergo
subsequent treatment to further separate radionuclide contamination from the ash or stabilize the
cesium to prevent volatilization during the incineration process. Such treatments have also been
demonstrated in Japan (U.S. EPA, 2016), including the use of Prussian blue to bind cesium,
magnetic nanoparticle coated absorbent, solidification, washing and absorption on resin, and
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melting of slag. A study by EPA (U.S. EPA, 2018) highlighted the potential for cesium
vaporization during incineration and the use of kaolinite sorbent to enhance cesium capture,
successfully increasing particulate diameters into the super-micron (non-respirable) range,
achieving capture efficiency of 91%, and making the sorbent-bound cesium much easier to catch
in particulate control devices.
In the case of wide area radiological contamination, waste generation costs are likely to be the
largest fraction of the response and remediation phases. However, when adequately planned and
correctly executed, phytoremediation offers the flexibility to mitigate soil and water
contamination, while providing options for waste minimization.
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4. Recommendations and Gaps In Pliytoremedlatlon Use In Wide Area
Radiological Contamination Events
Phytoremediation offers a viable method for stabilizing and removing contamination with
significantly less cost than alternatives such as excavation or pump-and-treat methods. Selection
of appropriate plant species requires understanding of local soil and climate conditions and
assessment of hyperaccumulator feasibility in the local environment. Subject matter experts
should be convened early in the planning process, in conjunction with stakeholder input to
determine the holistic approach to phytoremediation, from site preparation and plant selection
through waste generation and disposal. The extent to which plant uptake has been researched for
a wide variety of radionuclides (and stable isotopes) is significant, largely performed to better
understand the effects of contamination on the environment, on the food chain and in relation to
human health risk assessment. Significant experience has been gained through the application of
phytoremediation technologies applied to wide areas in the former Soviet Union and Japan
following nuclear power plant accidents. This experience has driven both scientific data and
technical innovations to improve phytoremediation understanding and minimize waste
generation. Plant species such as amaranthus, Indian mustard, kochia and hybrid varieties of
poplar and willow have been shown repeatedly in published literature to serve as
hyperaccumulators, but this should be considered together with soil type and contaminant
geochemistry. However, according to Schnoor (1997), "Phytoremediation systems are like any
other treatment scheme; one cannot simply walk away from them and expect success. There are
events that can cause failure that should be realistically assessed at the outset. These include
killing frosts, wind, storms, animals, disease or infestation, and latent toxicity."
Nevertheless, technical gaps in our knowledge base still exist, particularly when
phytoremediation is applied to soils with a high clay content. In such cases, the use of
amendments and the addition of bacteria have shown to be somewhat beneficial in increasing
bioaccumulation effectiveness. However, research in this area is still lacking. Recent work by
Varazi et al. (2015) screened plant species, bacterial strains, and natural sorbent materials (e.g.,
native clays and rock formations) to create enhanced bioaccumulation systems. Work by Djedidi
et al. (2014 and 2016) and Aung (2016) have also demonstrated the enhancements achieved
when microbial strains are added to a phytoremediation regimen. More experience can be
learned from continued management of vegetation waste in Japan.
The next step will be to identify under what conditions phytoremediation methods would be
beneficial compared to other remediation options and which of the methods would be most
applicable. The comparison should be comprehensive to include factors such as radiation
reduction, cost, difficulty, time, labor, stakeholder perception, etc. The beneficial
phytoremediation methods should be further developed with their operating procedures to
prepare for responses to the potential contamination scenarios.
6. References
Ainsworth, C.C. (2006) "Project Work Plan 100-N Area Strontium-90 Treatability
Demonstration Project: Phytoremediation Along the 100-N Columbia River Riparian Zone."
Richland, Washington: Pacific Northwest National Laboratory (PNNL), report PNNL-SA-
49953 (April 2006).
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-------
Aung, H.P., Mensah, A.D., Aye, Y.S., Djedidi, S., Oikawa, Y., Yokoyama, T., Suzuki, S. and
Bellingrath-Kimura, S.D. (2016) "Transfer of Radiocesium from Rhizosphere Soil to Four
Cruciferous Vegetables in association with a bacilluspumilus Strain and Root Exudation."
Journal of Environmental Radioactivity 164:209-219.
Blount, G.C., Caldwell, C.C., Cardoso- Neto, J.E., Conner, K.R., Jannik, G.T., Murphy Jr., C.E.,
Noffsinger, D.C. and Ross, J. A. (2003) "The Use of Natural Systems to Remediate Groundwater:
Department of Energy Experience at the Savannah River Site." Federal Facilities Environmental
Journal, Spring 2003, 14(l):55-73.
Broadley, M.R. and Willey, N.J. (1997) "Differences in Root Uptake of Radiocaesium by 30
Plant Tax." Environmental Pollution 97(1-2): 11-15.
Dan, W., Xiaoxue, Z., Xuegang, L., and Yunlai, T. (2015) "Phytoextraction Ability of
Amaranthus mangostanus L. from Contaminated Soils with Cs or Sr." Journal of Bioremediation
& Biodegradation 6:277. doi:10.4172/2155-6199.1000277.
Djedidi, S., Kojima, K., Yamaya, H. and Ohkama-Ohtsu, N. (2014) "Stable Cesium Uptake and
Accumulation Capacities of Five Plant Species as Influenced by Bacterial Inoculation and
Cesium Distribution in the Soil." Journal of Plant Research 127(5):585-597.
Djedidi, S., Kojima, K., Ohkama-Ohtsu, N., Bellingrath-Kimura, S-D. and Yokoyama, T. (2016)
"Growth and 137Cs Uptake And Accumulation Among 56 Japanese Cultivars of Brassica rapa,
Brassica juncea and Brassica napus Grown in a Contaminated Field in Fukushima: Effect of
Inoculation with & Bacillus pumilus Strain." Journal of Environmental Radioactivity 157:27-37.
Dushenkov, S., Mikheev, A., Prokhnevsky, A., Ruchko, M and Sorochinsky, B. (1999)
"Phytoremediation of Radiocesium-Contaminated Soil in the Vicinity of Chernobyl, Ukraine."
Environmental Science and Technology 33(3):469-475.
Efremenkov, V.M. (1989) "Radioactive waste management at nuclear power plants." (IAEA
Bulletin, 4/1989)."
https://www.iaea.org/sites/default/files/publications/magazines/bulletin/bull31-
4/31404683742.pdf
Entry, J.A., Rygiewicz, P.T. and Emmingham, W.H. (1993) "Accumulation of Cesium-137 and
Strontium-90 in Ponderosa Pine and Monterey Pine Seedlings." Journal of Environmental
Quality 22(4):742-746.
Entry, J.A., Vance, N.C., Hamilton, M.A., Zabowski, D., Watrud, L.S. and Adriano, D.C. (1995)
"Phytoremediation of Soil Contaminated with Low Concentrations of Radionuclides." Water,
Air, and Soil Pollution 88(1-2): 167-176.
Entry, J.A. and Watrud, L.S. (1998) "Potential Remediation of 137Cs and 90Sr Contaminated Soil
by Accumulation in Alamo Switchgrass " Water, Air, and Soil Pollution 104:339-352.
22

-------
Fellows, R.J., Fruchter, J.S. and Driver, C.J. (2009) 100-N Area Strontium-90 Treatability
Demonstration Project: Food Chain Transfer Studies for Phytoremediation Along the 100-N
Columbia River Riparian Zone. Richland, Washington: Pacific Northwest National Laboratory
(PNNL), report PNNL-18294, April 2009.
Fellows, R.J., Fruchter, J.S., Driver, C.J. and Ainsworth, C.C. (2010) 100-N Area Strontium-90
Treatability Demonstration Project: Phytoextraction Along the 100-N Columbia River Riparian
Zone - Field Treatability Study. Richland, Washington: Pacific Northwest National Laboratory
(PNNL), report PNNL-19120, January 2010.
Fuhrmann, M., Lasat, M.M., Ebbs, S.D., Kochian, L.V. and Cornish, J. (2002) "Uptake of
Cesium-137 and Strontium-90 from Contaminated Soil by Three Plant Species; Application to
Phytoremediation." Journal of Environmental Quality 31(3): 904-909.
Fuhrman, M. (2006) "Plant Uptake and Release of Cesium-137: Application to
Phytoremediation." The 18th World Congress of Soil Science (July 9-15, 2006).
Fukuda, S.-Y., Iwamoto, K., Atsumi, M., Yokoyama, A., Nakayama, T., Ishida, K-I., Inouye, I
and Shiraiwa, Y. (2014) "Global Searches for Microalgae and Aquatic Plants that can Eliminate
Radioactive Cesium, Iodine and Strontium from the Radio-polluted Aquatic Environment: A
Bioremediation Strategy." Journal of Plant Research 127(l):79-89.
Hitchcock, D.R., Barton, C.D., Rebel, K.T., Singer, J., Seaman, J.C., Strawbridge, J.D., Riha,
S.J. and Blake, J.I. (2005) "A Containment and Disposition Strategy for Tritium-Contaminated
Groundwater at the Savannah River Site, South Carolina, United States." Environmental
Geosciences 12(1): 17-28.
Hossner, L.R., Loeppert, R.H., Newton, R. J., Szaniszlo, P.J. and Attrep, M. (1998) Literature
Review: Phytoaccumulation of Chromium, Uranium, and Plutonium in Plant Systems. Amarillo,
TX: Amarillo National Resource Center for Plutonium (ANRCP), ANRCP report -1998-3, May
1998.
IAEA (International Atomic Energy Agency ) (1991) The International Chernobyl Project
Technical Report: Assessment of Radiological Consequences and Evaluation of Protective
Measures. Vienna, Austria: International Atomic Energy Agency (IAEA), 1991 ISBN 92-0-
129191-4.
IAEA (1994) Handbook of Parameter Values for the Prediction of Radionuclide Transfer in
Temperate Environments. Vienna, Austria: International Atomic Energy Agency (IAEA), IAEA
Technical Report Series 364, 1994.
IAEA (2009) Quantification of Radionuclide Transfer in Terrestrial and Freshwater
Environments for Radiological Assessments. Vienna, Austria: International Atomic Energy
Agency (IAEA), IAEA Technical Document (TECDOC) 1616, May 2009.
23

-------
IAEA (2010) Handbook of Parameter Values for the Prediction of Radionuclide Transfer in
Terrestrial and Freshwater Environments. Vienna, Austria: International Atomic Energy Agency
(IAEA), IAEA Technical Report Series 472, January 2010.
IAEA (2012) Guidelines for Remediation Strategies to Reduce the Radiological Consequences
of Environmental Contamination. Vienna, Austria: International Atomic Energy Agency (IAEA),
IAEA Technical Report Series 475, November 2012.
IAEA (2015) The Fukushima Daiichi Accident, Technical Volume 4/5, Radiological
Consequences. Vienna, Austria: International Atomic Energy Agency (IAEA), IAEA report
STI/PUB/1710, August 2015.
ITRC (Interstate Technology & Regulatory Council) (1999) Phytoremediation Decision Tree.
Interstate Technology & Regulatory Council (ITRC), ITRC report PHYTO-1, December 1999
(no longer available, refer to ITRC 2009).
ITRC (2001) Phytotechnology Technical and Regulatory Guidance Document. Interstate
Technology & Regulatory Council (ITRC), ITRC report PHYTO-2, April 2001 (no longer
available, refer to ITRC 2009).
ITRC (2009) Phytotechnology Technical and Regulatory Guidance and Decision Trees, Revised.
Interstate Technology & Regulatory Council (ITRC), ITRC report PHYTO-3, February 2009.
Jablonowski, E., Kudarauskas, P., Lemieux, P., Michael, J., Parrish, C., Pike, J. and Schultheisz,
D. (2011) "Report on Waste Disposal Workshops for a Radiological Dispersal Device (RDD)
Attack in an Urban Area - 11543." Waste Management 2011 Conference, February 27-March 3,
2011, Phoenix, AZ.
Lasat, M.M., Norvell, W.A. and Kochian, L.V. (1997) "Potential for Phytoextraction of 137Cs
from a Contaminated Soil." Plant and Soil 195:99-106.
Lasat, M.M., Fuhrmann, M., Ebbs, S.D., Cornish, J.E. and Kochian, L.V. (1998)
"Phytoremediation of a Radiocesium-Contaminated Soil: Evaluation of Cesium-137
Bioaccumulation in the Shoots of Three Plant Species." Journal of Environmental Quality
27(1): 165-169.
Marmiroli, N., Samotokin, B., and Marmiroli, M. (eds.) (2007) Advanced Science and
Technology for Biological Decontamination of Sites Affected by Chemical and Radiological
Nuclear Agents. Dordrecht, Netherlands: Springer, North Atlantic Treaty Organization (NATO)
Science Series, IV. Earth and Environmental Sciences NAIV, Vol 75, 2007.
Middleton, L.J. (1959) "Radioactive Strontium and Cesium in the Edible Parts of Crops After
Foliar Contamination." International Journal of Radiation Biology l(4):387-402.
Murphy, C.E. and Tuckfield, R.C. (1994) "Transuranic Element Uptake and Cycling in a Forest
Over an Old Burial Ground." Science of the Total Environment 157:115-124.
24

-------
Nishita, H., Steen, A.J. and Larson, K.H. (1958) "Release of Sr90 and Csl37 from Vina Loam
upon Prolonged Cropping." Soil Science 86(4): 195-201.
Osako, M. (2015) "Appropriate Management Technologies for Radioactively Contaminated Soil
and Waste." Presentation at International Symposium on Radiological Issues for Fukushima's
Revitalized Future, May 30-31, 2015, Fukushima City, Japan.
Parajuli, D., Tanaka, H., Hakuta, Y., Minami, K., Fukuda, S., Umeoka, K., Kamimura, R.,
Hayashi, Y., Ouchi, M., and Kawamoto, T. (2013) "Dealing with the Aftermath of Fukushima
Daiichi Nuclear Accident: Decontamination of Radioactive Cesium Enriched Ash."
Environmental Science and Technology 47(8):3800-3806.
Paramonova, T., Shamshurina, E., Komissarova, O. and Belyaev, V. (2015) "Caesium-137 Root
Uptake by Agricultural and Wild Crops in Post-Chernobyl Landscape: The Possibilities for
Phytoremediation?" Geophysical Research Abstracts Vol. 17, EGU2015-83, 2015.
PNNL (1998) Proceedings of the Chornobyl Phytoremediation and Biomass Energy Conversion
Workshop, February 23-25, 1998, Slavutych, Ukraine. Richland, Washington: Pacific Northwest
National Laboratory (PNNL), report PNNL-SA-29991, June 1998.
Sadhasivam, M., Pitchamuthu, S. and Ayyavu, V. (2010) Chemically Induced Phytoextraction of
Caesium-137. 19th World Congress of Soil Science, Soil Solutions for a Changing World, 1-6
August 2010, Brisbane, Australia.
Sandeep, S. and Manjaiah, K.M. (2007) "Transfer Factors of 134Cs to Crops from Typic
Haplustept under Tropical Region as Influenced by Potassium Application." Journal of
Environmental Radioactivity 99(2):349-358.
Schnoor, J.L. (1997) "Phytoremediation." Ground-Water Remediation Technologies Analysis
Center (GWRTAC) Technical Evaluation Report TE-98-01.
Soudek, P., Valenova, S., Benesova, D. and Vanek, T. (2007) "From Laboratory Experiments to
Large Scale Application - An Example of the Phytoremediation of Radionuclides." In:
Marmiroli, N., Samotokin, B., Marmiroli, M. (eds) Advanced Science and Technology for
Biological Decontamination of Sites Affected by Chemical and Radiological Nuclear Agents,
NATO Science Series: IV: Earth and Environmental Sciences, vol 75, 139-158. Dordrecht,
Netherlands: Springer.
Sugiura, Y., Shibata, M., Ogata, Y., Ozawa, H., Kanasashi, T. and Takenaka, C. (2016)
"Evaluation of Radiocesium Concentrations in New Leaves of Wild Plants During 2011 and
2012 Following the Fukushima Dai-ichi Nuclear Power Plant Accident." Journal of
Environmental Radioactivity 160:8-24.
Sun, X., Kobayashi, S., Tokue, A., Itabashi, H., Mori, M. (2019) "Enhanced Radiocesium
Uptake by Rice with Fermented Bark and Ammonium Salt Amendments." Journal of
Environmental Radioactivity 202:59-65.
25

-------
Tamaoki, M., Yabe, T., Furukawa, J., Watanabe, M., Ikeda, K., Yasutani, I. and Nishizawa, T.
(2016) "Comparison of Potentials of Higher Plants for Phytoremediation of Radioactive Cesium
from Contaminated Soil." Environmental Control Biology 54(l):65-69.
Terashima, I., Shiyomi, M. and Fukuda, H. (2014) "134Cs and 137Cs Levels in a Grassland, 32 km
Northwest of the Fukushima 1 Nuclear Power Plant, Measured for Two Seasons After the
Fallout." Journal of Plant Research 127:23-50.
U.S. DHS (U.S. Department of Homeland Security) (2016) National Response Framework, third
edition. United States Department of Homeland Security (DHS), June 2016.
U.S EPA (U.S. Environmental Protection Agency) (1998) EPA Superfund Record of Decision:
Idaho National Engineering Lab (US DOE) (ANL-W) OU 9-04 Idaho Falls, ID. United States
Environmental Protection Agency (US EPA) report EPA 541/R98/061, October 1998.
U.S. EPA (1999) Phytoremediation Resource Guide. United States Environmental Protection
Agency (US EPA) report EPA/542/B-99/003, June 1999. Washington DC: US EPA.
U.S. EPA (2001) Summary of the Phytoremediation State of the Science Conference, Boston
Massachusetts, May 1-2, 2000. United States Environmental Protection Agency (US EPA) report
EPA/625/R01/01 la (November 2001). Washington DC: US EPA.
U.S. EPA (2005) Use of Field-Scale Phytotechnology for Chlorinated Solvents, Metals,
Explosives and Propellants, and Pesticides. United States Environmental Protection Agency (US
EPA) report EPA/542/R-05/002, April 2005.
U.S. EPA (2012) Report on the 2011 Workshop on Chemical-Biological-Radiological Disposal
in Landfills. United States Environmental Protection Agency (US EPA) report EPA/600/R-
11/218, February 2012.
U.S. EPA (2013) Technologies to Improve Efficiency of Waste Management and Cleanup After
a Radiological Dispersal Device Incident, Standard Operational Guideline. United States
Environmental Protection Agency (US EPA) report EPA/600/R-13/124, October 2013.
Washington DC: US EPA.
U.S. EPA (2014) Results of Literature Review and Technology Survey of Source Reduction and
Waste Minimization Techniques Applied to a Wide Area Radiological Incident. United States
Environmental Protection Agency (US EPA) report EPA/600/R-14/209, August 2014.
Washington DC: US EPA.
U.S. EPA (2016) Current and Emerging Post-Fukushima Technologies, and Techniques, and
Practices for Wide Area Radiological Survey, Remediation, and Waste Management. United
States Environmental Protection Agency (US EPA) report EPA/600/R-16/140, July 2016.
Washington DC: US EPA.
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-------
U.S. EPA (2018) The Use of Combustion Process Modification to Capture Cesium from
Combustion of Contaminated Biomass. United States Environmental Protection Agency (US
EPA) report EPA/600/B-18/240, September 2018. Washington DC: US EPA.
U.S. EPA (2019) Management and Disposal of Vehicles Following a Wide Area Incident:
Literature Review and Stakeholder Workshop. United States Environmental Protection Agency
(US EPA) report EPA/600/R-19/068, January 2019. Washington DC: US EPA.
Vandenhove, H., Van Hees, M. and Van Winckel, S. (2001) "Feasibility of Phytoextraction to
Clean Up Low-Level Uranium-Contaminated Soil." International Journal of Phytoremediation
3(3):301-320.
Varazi, T., Kurashvili, M., Pruidze, M., Khatisashvili, G., Gagelidze, N., Adamia, G.,
Zaalishvili, G., Gordeziani, M. and Sutton, M. (2015) "A New Approach and Tools for
Perfecting Phytoremediation Technology." American Journal of Environmental Protection 4(3-
1): 143-147.
Victorova, N., Voitesekhovitch, O., Sorochinsky, B., Vandenhove, H., Konoplev, A. and
Konopleva, I. (2000) "Phytoremediation of Chernobyl Contaminated Land." Radiation
Protection Dosimetry 92(1-3): 59-64.
Willey, N.J., Tang, S. and Watt, N.R. (2005) "Predicting Inter-Taxa Differences in Plant Uptake
of Cesium-134/137." Journal of Environmental Quality 34(5): 1478-1489.
Yamashita, J., Enomoto, T., Yamada, M., Ono, T., Hanafusa, T., Nagamatsu, T., Sonoda, S. and
Yamamoto, Y. (2014) "Estimation of Soil-to-Plant Transfer Factors of Radiocesium in 99 Wild
Plant Species Grown in Arable Lands 1 Year After the Fukushima 1 Nuclear Power Plant
Accident." Journal of Plant Research 127(1): 11-22.
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