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o
/A newsletter about soil, sediment, and ground-water characterization and remediation technologies
May 2006
Issue 24
This issue o/Technology News and Trends highlights field applications of phytoremediation to
remove, transfer, stabilize, or destroy contaminants in soil, sediment, or ground water. Each
application employs one or more of the primary mechanisms used by plants to remediate sites:
phytoextraction, enhanced rhizosphere biodegradation, hydraulic control, phytodegradation,
and phytovolatilization.
Compacted Clay and ET Landfill Covers Compared in Humid Climate
The U.S. EPA National Risk Management
Research Laboratory (NRMRL) Alternative
Cover Assessment Program (ACAP) collaborated
with the Desert Research Institute (DRI) and
University of Wisconsin-Madison to evaluate
the field performance of two RCRA "final" cover
designs proposed for use on a Superfund landfill
in Albany, GA. The evaluation was conducted at
the Marine Corps Logistics Base (MCLB), where
facility-wide remediation requires installation of
multiple landfill covers for wastes generated by
past military activities.
The EPA, U.S. Navy, and U.S. Marine Corps
partnered in construction and operation of field
pilot-test cells at the MCLB to use in identifying
alternative covers that meet standard
performance criteria while offering potential cost
savings. Two 20- by 30-meter test cells were
constructed immediately adjacent to an existing
landfill, each containing a 10- by 20-meter
lysimeter to monitor water balance during the
evaluation. Each lysimeter was constructed of
a low-density polyethylene liner protected by a
geocomposite drainage layer.
An evapotranspiration cover (ETC) was
proposed as an alternative design to a
compacted-clay conventional cover. ETC
systems use vegetation and one or more soil
layers to retain water until it is either transpired
through vegetation or evaporated from the soil
surface. The technology is based on site water-
balance components such as soil water-storage
capacity, precipitation, surface runoff,
evapotranspiration, and infiltration. Due to the
Albany region's high average monthly rainfall
(2 to 6 inches) and high precipitation-to-
potential evapotranspiration ratio (1.10), the
efficacy of an ETC system in such a climate
was unclear prior to the pilot test.
In the ETC test cell, 2.3 feet of native sandy soil
were placed on a synthetic root barrier
overlaying a 6-inch layer of "interim" cover soil.
Though not typically employed in final-cover
designs, the barrier and interim-cover soil
(Figure 1) helped to ensure proper functioning
of the test lysimeters. An additional 2 feet of
native sandy-clay soil, amended with peanut-
shell-composted biosolids from a local
wastewater treatment plant, were placed on the
non-amended soil. Finally, two-year-old poplar
trees were planted at 30-inch depths with an
understory of grasses. This approach achieved
anETC withathicknessof4.3 feet.
The cover for the second test cell was
constructed of 18 inches of compacted clay
using conventional techniques for RCRA
Subtitle D landfill covers. As in the ETC test
cell, the material was placed on a synthetic
root barrier to separate the cover from 6 inches
of underlying interim-cover soil. The clay then
was topped by a surface layer comprising 6
inches of topsoil seeded with native (Bermuda
and rye) grasses, resulting in a conventional
cover thickness of 2 feet.
A weather station was installed adjacent to the
lysimeters to measure precipitation, temperature,
relative humidity, solar radiation, and wind speed
and direction. All data were collected hourly and
transmitted daily to DRI for analysis.
[continued on page 2]
Contents
Compacted Clay and ET
Landfill Covers Compared
in Humid Climate page 1
Ferns Successfully
Extract Arsenic from
Soil in Mid-Atlantic
Climate page 2
Phytoremediation
Reduces Mechanical
Pumping and Ex-Situ
Treatment of Ground
Water page 4
Phytotechnology
Expedites Removal of
Oil Waste from
Shoreline Sediment page 5
CLU-IN Resources
Phytoremediation is one of 19
focus areas addressed in
CLU-IN's Technology Focus, an
online compilation of information
on remediation technologies.
Visit http://www.cluin.org/
techfocus to learn more about
the basics of phytoremediation,
view site-specific application
summaries, consider upcoming
training opportunities, and
access additional online
resources. Technology Focus
also allows users to review and
download new guidance
materials, such as the
Remediation Technologies
Development Forum's 2005
Evaluation of Phytoremediation
for Management of Chlorinated
Solvents in Soil and Groundwa-
ter.
Recycled/Recyclable
Printed with Soy/Car>ola Ink or paper that
contains at least 50% recycled fiber
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[continued from page 1]
Monthly monitoring of the water balance over
three years indicated that the alternative ETC
system performed better than the
conventional compacted-clay barrier. Four
years after construction, hydraulic
conductivity measurements on the
compacted-clay barrier were conducted in the
field with a sealed double-ring infiltrometer
and two-state borehole permeameters. In
addition, laboratory measurements were
conducted on hand-carved blocks collected
during construction and after four years of
service. Test results indicated that hydraulic
conductivity increased approximately three
orders of magnitude (<10"7to >1O4 cm/s) in
four years.
A dye-tracer test and soil-structure analysis
confirmed that extensive cracking and root
development occurred throughout the entire
depth of the compacted-clay layer of the
conventional cover. Patterns in the response
of drainage to precipitation suggest that
preferential flow paths developed in the
compacted clay soon after construction, likely
in response to irreversible cracking from soil
desiccation.
Final results of the evaluation suggested that
the site's wet/dry cycles and root penetration
caused the clay barrier to begin failing within
the first eight months of service. These findings
are similar to those of other ACAP laboratory
and field studies showing that conventional
clay barriers also degrade quickly in cool/humid
or warm/dry environments and only minimally
reduce percolation.
Feasibility study cost estimates for installing a
full-scale, 17-acre ETC and monitoring over 30
years are approximately one-half ($10.5
million) of those associated with a
conventional cover. Additional details on this
field comparison and the results of other
ACAP projects are available at http//
www.acap.dri.edu.
Contributed by Steven Rock, NRMRL
(rock.steven(q)epa.gov or 513-569-7149),
Bill Albright, DRI (biUaCdidri.edu), and
Craig Benson, University of Wisconsin-
Madison (benson(a)engr.wisc.edu)
Evapotranspiration Alternative Cover
Root barrier
Figure 1. The ET cover system tested at the
MCLB relies on water-storage capacity of the
vegetated soil layer, rather than the low
hydraulic-conductivity materials used in
conventional covers, to serve as a water
Ferns Successfully Extract Arsenic from Soil in Mid-Atlantic Climate
The U.S. Army Corps of Engineers (USAGE)
recently completed the secondyearofafield
verification study on the potential for
phytoremediation to address elevated
arsenic concentrations in soil at the Spring
Valley Formerly Used Definse Site (FUDS)
in Washington, DC. The study began in 2004
at two residential areas and one public-
access area and expanded in 2005 with nine
additional residential areas. Five species of
ferns were selected for their demonstrated
capability to extract and store arsenic in their
fronds. The use of small plants such as ferns
also minimized destruction of existing
neighborhood trees and other sensitive
landscape features during the planting
process.
Spring Valley FUDS encompasses
approximately 661 acres used by the U.S.
Department of Defense during World War I
for production and testing of chemical warfare
agents, some of which contained arsenic.
Investigative soil sampling starting in 2001
indicated arsenic concentrations above the
clean-up goal of 20 mg/kg at a total of 140
sites, primarily in the upper surface soil (< 12-
inch depths). Although a 2003 engineering
evaluation and cost analysis specified
excavation and backfill as the primary clean-
up remedy, efforts were initiated the following
year to evaluate phytoremediation as an
alternative for contaminant hotspots in
sensitive areas. With typical root depths of
12 inches, ferns were deemed capable of
preventing long-term exposure to the elevated
arsenic concentrations.
Based on the results of a 2004 greenhouse
feasibility study on soil collected from Spring
Valley, the first year of the field study
employed three species of ferns: Pteris
vittata, P. cretica, and P. multifida.
Approximately 2,800 plants were planted in
May 2004 at 14 plots covering three property
lots with arsenic concentrations of 16-127
mg/kg. The ferns were planted in an average
density of I/foot2, and maintained through
the summer by routine surface sprinkling.
At the end of the growing season
(November), ferns were harvested and
biomass (plant matter above the roots) was
collected for laboratory analysis. Plants were
harvested by mowing at a height of one to
two inches above the crown in order to
preserve the plant root systems and enhance
possibilities for regrowth the following
season.
[continued on page 3]
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[continued from page 2]
Plant analyses yielded arsenic
concentrations of up to 1,500 mg/kg in plant
biomass due to direct absorption by the
roots. In addition, soil analyses indicated a
reduction in soil arsenic concentrations to
below the target level of 20 mg/kg in two of
the 14 plots. The average decrease in soil
arsenic concentrations across all plots was
9 mg/kg. Following laboratory use, the
harvested biomass was disposed offsite as
hazardous waste.
In 2005, field activities were expanded to
include nine additional property lots,
different site conditions, and additional fern
species (P. mayii, P. nervosa, and P.
parkerii). Approximately 10,000 ferns were
introduced under existing trees and shrubs
at 33 plots across 11 property lots (Figure 2).
At 13 of the 14 plots studied in 2004, the
planting areas were expanded to address
elevated soil arsenic remaining at the edge
of their former boundaries, and maintenance
and data collection continued.
Results in 2005 showed that phyto-
remediation was conducted with limited
disruption to existing trees and perennial
vegetation and was effective in decreasing
soil arsenic concentrations (Table 1).
Seventeen of the 33 test plots (sampling
grids) planted in 2005 required no further
action at the conclusion of the growing
season.
Species performance comparison indicated
that P. vittata produced the highest average
biomass yields, averaging 35% greater than
the other tested species and reaching an
average dry-weight biomass of 2,743 kg/Ha.
P. vittata 's higher biomass yields and
tendency to accumulate higher
concentrations of arsenic in fronds (up to
2,200 mg/kg in 2005) makes this species the
most promising candidate for expanded
Table 1. Concentrations of arsenic in
Figure 2. To minimize
disturbance of
residential property
owners, only turf grass
was removed during
fern planting at
Spring Valley.
phytoremediation at Spring Valley. In contrast,
frond tissues of P. parkerii grown in soil with
lower arsenic concentrations achieved arsenic
concentrations that were only slightly higher
than soil concentrations.
Analytical data from biomass and soil samples
were used to determine each plant's arsenic
bioconcentration factor, which is the ratio of
arsenic concentration in harvested plants to
the concentration in soil. These factors
provided an indirect measure of the extent to
which plants were taking up and storing
arsenic. For all test plots, the average plant
bioconcentration factor was 12;
bioconcentration factors greater than 10 are
considered high.
Application of surface mulch at the end of the
growing season enhanced the over-wintering
of ferns, which could reduce project costs
associated with subsequent replanting at plots
requiring more than one year of treatment. To
date, the estimated study cost is approximately
$475,000, including $75,000 for greenhouse
testing, $150,000 for 2004 field work and
materials, and $250,000 for 2005 activities.
Based on these successful results, the
USAGE will continue the study in May 2006
to include additional properties and
additional fern species. The USAGE also
plans to formally propose phytoremediation
as an alternative to excavation and backfilling
for arsenic remediation at Spring Valley
properties where this approach would be
more acceptable to property owners. As in
previous years of the study, however, the
presence of arsenic concentrations above
20 mg/kg at soil depths greater than 24
inches will preclude phytoremediation at a
particular site.
Contributed by Ed Hughes, USAGE
(edward. t. hughes (q)nab O2.usace. army, mil
or 410-962-6784) and Michael Blaylock,
Ph.D., Edenspace Systems Corporation
(blaylock(a),edenspace. com or 703-961-
8700)
of 9 mg/kg after one season of fern
growth in 2005.
Arsenic in Soil
Before Planting1
(mg/kg)
>50
20-50
10-20
<10
Number of
Sampling
Grids
10
8
10
9
Arsenic in Soil
After Harvesting2
(average, mg/kg)
62
22
11
7
Arsenic
Concentration2
Change
(average, mg/kg)
-30
-5
-3
0
Arsenic
Concentration2
in Plants
(average, mg/kg)
589
247
101
101
1 These arsenic concentration ranges were set to yield a comparable number of sampling
grids per range.
Performance reflects all fern species planted.
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Phytoremediation Reduces Mechanical Pumping and Ex-Situ Treatment of Ground Water
A ground-water phytoremediation system
comprising a 0.8-acre stand of willows was
installed in 1999 at the Solvents Recovery
Service of New England (SRSNE) Superfund
site in Southington, CT. The system is
designed to pump and treat contaminated
ground water, thereby seasonally reducing
the extent of mechanical pumping and
treatment. Thermal dissipation probes (TDPs)
were used to estimate sap velocity for subsets
of trees within the stand for several growing
seasons. The total basal area of the stand
was measured annually for use with mean
sap-velocity data to estimate the rate of
transpirational water use by the entire stand
(VT). During the 2004 growing season, VT for
the phytoremediation system appeared to
reduce the volume of ground water needing
ex-situ treatment by approximately 40%.
From 1955 to 1991, SRSNE reclaimed spent
industrial solvents. Chemical releases resulted
in contaminant source areas within former
lagoons, drum and tank areas, and a
processing area. The ground water contains
volatile organic compounds (VOCs) existing
as dense non-aqueous phase liquid in the
overburden and bedrock and as light non-
aqueous phase liquid in the overburden. The
primary VOCs of concern in the ground water
are trichloroethene, tetrachloroethene, 1,1-
dichloroethane, frr/w.s-l,2-dichloroethene, cis-
1,2-dichloroethene, 1,1,1 -trichloroethane,
ethylbenzene, toluene, and sec-butanol.
Concentrations of individual VOCs of concern
in the dissolved-phase plume range from 10
to40mg/L.
In 1995, a 700-foot-long, sheet-pile, barrier wall
and 12 overburden ground-water recovery
wells were installed as a non-time critical
removal action (NTCRA) to control migration
of the most highly contaminated ground
water. Recovered ground water was routed at
an average rate of 19 gallons per minute (gpm)
to an ultraviolet-oxidation treatment facility
that removed approximately 850 kg of VOCs
per year, at an annual operation and
maintenance cost of approximately $500,000
($0.05/gal of water treated). Ground water
within the 1.2-acre containment area is four to
five feet below ground surface and meets the
NTCRA compliance criterion requiring
maintenance of an inward hydraulic gradient
across the barrier wall.
An assessment of ground-water contaminant
phytotoxicity was conducted in a greenhouse
prior to planting trees onsite. A VOC mixture
mimicking the dissolved-phase plume (170 mg
VOCs/L) was tested using a system with hybrid
poplar tree saplings (Populusdeltoidesxnigrd)
planted in 50-gallon barrels packed with
alternating layers of pea gravel and sandy loam
soil. The trees were watered using a system
that automatically mixed neat (pure organic)
VOCs with water and dispensed the cocktail
into the bottom layer of gravel. Based on
measured physiological parameters such as
stomatal conductance, shoot elongation, and
biomass production, no phytotoxic effects were
observed.
Full-scale installation of the system at SRSNE
began in late May 1998. Within the containment
area, 10-12 four- to five-foot deep trenches were
dug, deeply planted with approximately 1,000
bare-root hybrid poplar saplings, and backfilled
with a sand/compost mixture. Only 60% of the
saplings survived, likely due to the late planting
and rapid onset of hot weather. The dead
poplars were replaced the following spring with
400 (Salix alba) willow cuttings. Boreholes were
drilled to the bottom of each backfilled trench,
long hardwood willow cuttings were deeply
planted, and the holes were backfilled with
sand/compost. The willows thrived in a
random distribution across the site and
attained maturity (canopy closure) during the
2005 growing season, becoming a 370-tree
stand spanning 0.8 acres. Due to a canker
infestation (Cryptodiaporthe populed),
however, all of the hybrid poplar trees were
removed from the site inMay 2002.
Ground-water pumping efficiency of the
phytoremediation system is demonstrated
by the calculated VT (Figure 3). The system's
treatment component likely includes various
processes. Earlier studies show that the fate
of chlorinated aliphatic compounds in
ground-water phytoremediation systems
involves plant uptake and release into the
atmosphere (phytovolatilization), followed
by photo-oxidation. A competing treatment
process, particularly for BTEX compounds,
is mineralization by bacteria residing in the
rhizosphere around plant roots (rhizo-
degradation).
During each growing season (May through
September) from 2000 to 2003, five to seven
trees were instrumented with TDPs. TDP data
analysis employed the mathematical product
of sap velocity (cm/h) and the cross sectional
area of the stem (cm2) at the point of TDP
insertion yielding sap flow (cm3/h). The
measured mean sap velocity was 26.7 cm/h,
and by 2003, the mean rate of sap flow for the
instrumented trees was 72 L/d.
[continued on page 5]
30-
25-
20-
15 -
10
5 -
0
Summertime Pumping/Transpiration
Total Treatment Rate
FigureS. Increased
transpiration rates
generated by trees
planted at the SRSNE
site in 1998-1999
significantly reduce
the need for
mechanical pumping
and treatment of
contaminated ground
Year
-------
[continued from page 4]
Measurement of each willowtree's basal area
was taken to determine the basal area for the
entire stand, which increased from 1.4 m2 in
2001 to 6.8m2 in 2004. These data were used
with the mean TDP sap-velocity data to
estimate Vr Between 2001 and 2004, the
mean VT increased from 2.1 gpm to 8 gpm.
Data suggested that VT at stand maturity,
which was reached in 2005, was 9 gpm.
Chlorinated solvents, which are readily
released into the atmosphere primarily from
tree stems, were detected in xylem core
samples obtained from multiple trees at the
site. Based on the volume of ground water
pumped by the trees in 2004 and on the VOC
concentrations in ground water, it is estimated
that approximately 340 kg of VOCs may have
been removed in that growing season by
processes such as phytovolatilization and
rhizodegradation. Both the mechanical pump-
and-treat system and the phytoremediation
system will continue to operate indefinitely. The
potential life-span of the planted willows is 80-
100 years.
The total cost of the phytoremediation system
is estimated at $281,900, including $ 15,500 for
design, $40,400 for greenhouse studies,
$ 115,300 for installation, $40,700 for replanting,
and $70,000 for maintenance and monitoring.
During the 2005 growing season alone, the
achieved 1.9 million-gallon VT avoided
equivalent use of the mechanical pump-and-
treat system, resulting in a savings of $97,000.
The "break even" point for project costs
should occur in 2006, and a net cost savings
of $470,000 is anticipated by 2010.
Contributed by Art M. Ferro, ENSR
(aferro(a)ensr.aecom.com or 919-872-
6600), Karen Lumino, U.S. EPA Region 1
(lumino. karen(q)epa. gov or 617-918-
1348), and Bruce Thompson, de maximis,
inc.
Phytotechnology Expedites Removal of Oil Waste from Shoreline Sediment
The U. S. EPANRMRL recently completed
a three-year series of treatability studies on
the use of phytotechnology to remediate
sediment deposited on the shoreline of the
Indiana Harbors Canal in Gary, IN. The canal
shoreline comprises 15-35% oil, which
greatly exceeds the 8% commonly considered
to be the upper limit for effective
bioremediation or phytoremediation. Trees,
grasses, and tuberous plants were
investigated for their ability to grow along
the canal shoreline and degrade or contain
the oil. The study also examined various
planting techniques for addressing high
contaminant concentrations in sandy soil.
The canal is located in an industrial area
where past releases of oil refinery waste left
hydrocarbons, most notably polyaromatic
hydrocarbons (PAH), that constitute
approximately 25% of the upper foot of
riparian soil. The presence of recalcitrant
hydrocarbons causes the soil to exhibit a
heavily oiled appearance, texture, and odor
in widespread areas devoid of vegetation.
Occasional oil sheens threaten aquatic wildlife
in the canal and reduce the quality of surface
and ground water flowing into Lake
Michigan.
NRMRL, Purdue University, North Carolina
State, and Ohio State University collaborated
in greenhouse and field studies to
characterize the soil microbial population and
plant viability within the study area. At
NRMRL's Cincinnati facility, initial
experiments also were conducted in a growth
chamber using contaminated soil from the
canal. From the most viable cuttings, varieties
of poplars and willows, sedges, and other
native plants were planted along the canal in
2002. Additional cuttings were added in an
adjacent plot the following year.
The study's mixed planting approach worked
to treat oil at multiple ground-water/surface
water interfaces: the top foot of soil with
grasses, the deeper soil and ground water with
trees, and the water's edge with tuberous
plants. Plants introduced during the study
were found to trap floating debris as canal
waters rose and fell, catch windblown dust
and seeds, catch vegetative litter, and pro vide
anchorage for local opportunistic plants.
Plantings also established a root mass that
formed a mat in the oily shore material. This
biologically active layer helps control erosion,
prevent sheen from entering surface water in
the canal, and provide the habitat and
nutrients needed for direct microbial
degradation of the oil.
By 2004, there was a visual decrease in the
sheen on the canal's surface water. Many of
the plants now growing at the study site are
opportunistic volunteers such as common
reeds (Phragmites australis), cattails (Typha
latifo\\a), and arrowhead (Saittara
latifolia). These non-planted species also
have extensive roots systems that can
penetrate the oily sand more vigorously
than the planted trees. Though they
generally do not offer high aesthetic value
[continued on page 6]
Contact Us
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Technology News and Trends
welcomes readers' comments
and contributions. Address
correspondence to:
John Quander
Office of Superfund Remediation
and Technology Innovation
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1200 Pennsylvania Ave, NW
Washington, DC 20460
Phone:703-603-7198
Fax: 703-603-9135
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Solid Waste and
Emergency Response
(5102G)
EPA 542-N-06-003
May 2006
Issue No. 24
United States
Environmental Protection Agency
National Service Center for Environmental Publications
P.O. Box 42419
Cincinnati, OH 45242
Presorted Standard
Postage and Fees Paid
EPA
Permit No. G-35
Official Business
Penalty for Private Use $300
[continued from page 5]
or wildlife habitat, these species possess
high survival rates.
Disturbance of the site during planting
activities, including breakage of an
asphaltene layer and application of fertilizers,
appeared to accelerate colonization of reeds
and cattails significantly. Approximately 75%
of the planted poplars and willows suffer
from beaver damage. This damage, followed
by water inundation caused by 1 - to 2-foot
canal level fluctuations and subsequent oily
coating of young leaves, has resulted in
difficulty employing tree species at this site.
Microbial activity in the soil increased 2-5
orders of magnitude by 2005. Analysis of
soil samples collected within and outside
the study area in 2003 and 2004 indicated
that areas dominated by common reeds in
both planted and implanted areas contain
the lowest concentrations of high-molecular-
weight material. Areas dominated by cattails
have the highest concentration of high-
molecular-weight material and lowest
concentration of low-molecular-weight
material. Greenhouse tests on contaminated
soil taken from the study area show more PAH
degradation in planted plots than in implanted
plots (Figure 4). Though remediation of the
canal is not complete or imminent, the use of
phytotechnology is expected to accelerate
natural degradation of the oil-based
contaminants and ultimate ecorestoration
of the canal.
Contributed by Ann Whelan, U.S. EPA
Region 5 (whelm. ann(a),epa.gov or 312-
886-7258) and Steven Rock, NRMRL
(rock.steven(q),epa.gov or 513-569-7149)
TPAH (42 PAHs) in Soil: Three Years After Plantings
Plant-Specific Plots
Figure 4.
Cattails
apparently
degraded the
largest amount
of total
polyaromatic
hydrocarbons
(TPAH) in soil
at the Indiana
Harbors Canal
study plots.
EPA is publishing this newsletter as a means of disseminating useful information regarding innovative and alternative treatment techniques and
technologies. The Agency does not endorse specific technology vendors.
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