United States
Environmental Protection
Agency
Solid Waste and
Emergency Response
(5102G)
EPA 542-N-98-005
May 1998
Issue No. 29
*» rcCH TRENDS
CONTENTS
Biosolids and Fly Ash
Used to Restore the
Bunker Hill
Superfund Site page 1
Long-Term
Phytoremediation
of Organic Soil
Pollutants page 2
Phytoremediation
of Selenium-Laden
Soils page 3
Biodegradation of
De-icing Fluids page 4
New Phytoremediation
Bibliography Now
Available page 4
The Applied Technologies
Newsletter for Superfund
Removals & Remedial
Actions & RCRA
Corrective Action
ABOUT THIS ISSUE
This issue highlights
Phytoremediation and other
biological processes for
hazardous site remediation.
Biosolids and Fly Ash
Used to Restore the
Bunker Hill Superfund
Site
by Sally Brown, Ph.D., U.S.
Department of Agriculture,
Agricultural Research Service
Application of a remediation mixture of
municipal biosolids, wood ash, and log
yard wood waste is proving highly
effective in reducing erosion, correcting
soil pH, and supporting a self-sustaining
vegetative cover at the Bunker Hill, ID,
Superfund site. In addition, levels of
zinc, cadmium, and copper in vegetation
are within normal ranges (less than 300
ppm zinc, 0.5-5 ppm cadmium, and 6-30
ppm copper) for plants growing on the
treated areas. Revegetation of more than
1,000 acres on this site is a problem due
to deficiencies of certain nutrients as well
as toxic levels of other elements. In the
past, these areas were incapable of
supporting any vegetation.
Treated Area in Bunker Hill Site, Idaho
Experts from the U.S. Department of
Agriculture, University of Washington,
University of Idaho, the Northwest
Biosolids Management Association,
Washington Water Power, and EPA are
collaborating in this effort to re-establish
native plant communities and reduce
contaminant levels in this severely
disturbed area. Direct visual comparison
of one of the treated areas with the
project control plot is shown below.
[Additional photographs are shown in
the Internet version of this newsletter.]
The Bunker Hill site, located in the
Coeur d'Alene River Basin, is the second
largest Superfund site in the nation.
Zinc and lead mining/smelting was
conducted in the area for over 60 years,
resulting in soils with extremely high
metal concentrations, low pH levels, high
susceptibility to erosion, low microbial
growth levels, and low water-holding
capacity. Earlier restoration efforts
involving the construction of terraces (on
slopes exceeding 50 percent) and
addition of limestone and fertilizers were
not successful in establishing a vegeta-
tive cover.
Demonstration
and pilot-scale
plots were
installed in the
spring and fall of
1997 in order to
evaluate the
success of
biosolid/fly ash
applications.
Local sources of
the application
materials were
used exclusively.
Biosolids
provided by three
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different municipal areas (Biosolids 1, 2,
and 3) were mixed with a 1:1 (by volume)
blend of wood ash from local power
generators and log yard wood waste from
a nearby railroad company. Biosolids
were mixed and applied at a rate of 25
and 50 dry tons/acre (t/a). Ash was
applied at a constant rate of 100 wet t/a to
provide 22 t/a calcium carbonate equiva-
lent. The log yard wood waste was added
at a fixed volume ratio of 1:5. Prior to
surface application (at a rate of 30
pounds/acre), a seeding mixture of
grasses and legumes was added to the
biosolids/ash amendment mixture. This
mixture formed a highly adhesive product
that could remain on the eroded hillsides,
while simultaneously permitting seedling
emergence and increasing water perme-
ability.
Two months after treatment of two to
three acre test plots, increased levels of
highly diverse microbial populations were
observed in soils directly below the
treated surface. No microbial activity was
detected on control soils. Samples taken
from plants six months after initial
application of each of the three biosolid
mixtures indicate reduced levels of toxic
metals and increased levels of soil
nutrients (as shown in Figure 1). These
data indicate that the amendment re-
establishes normal concentration levels of
these metals, whereby the metals are
neither nutritionally deficient or toxic.
In the fall of 1997, a second phase of the
study was initiated to determine the
effectiveness of different locally available
residual materials, compare ratios of
different amendments, determine the most
effective seeding time, and predict
long-term fate of restoration efforts. Four
different biosolids were used, in addition
to three different wood ashes, two
composts, one type of pulp and paper
sludge, and log yard waste. No
movement of material from the test plots
has occurred, despite several erosive
weather events.
Full germination of grasses and legumes
is expected by this spring. An additional
study, to cover approximately 20 acres, is
slated to be established at Bunker Hill or
a similar site this summer. The study will
focus on development of steep slope
application technology, and will establish
a long-term ecological research station to
monitor the effects of this technology on
native biota. A manual of practice for
these and similar restoration methods
used around the nation will be developed.
For additional information, contact Dr.
Sally Brown (U.S. Department of Agri-
culture, Agricultural Research Service) at
301-504-9230.
Long-Term
Phytoremediation of
Organic Soil Pollutants
by John S. Fletcher, Ph.D.,
University of Oklahoma, and Sunil
I. Shah, Union Carbide Corp.
Research at a former industrial sludge
lagoon is underway to evaluate
phytoremediation of recalcitrant organic
compounds on a time scale that is realistic
for slow natural processes. University of
Figure 1. Average Elemental Concentrations in Plants
Control Plot
Biosolid 1
Riosolid 2
Biosolid 3
Zinc
(mg/kg)
215
150
108
59
Cadmium
(mg/kg)
0.4
2.3
0.6
0.9
Copper
(mg/kg)
3.9
11.4
9.9
13.8
Phosphorus
(g/tg)
590
3,800
6,830
6,110
Potassium
(gfcg)
10
38
26
25
Oklahoma researchers are working with
Union Carbide at a Texas site to
determine how a mixture of contaminants
has influenced ecological events over
time and, in turn, how an evolving plant-
microbe community has influenced the
fate (degradation and/or immobilization)
of the contaminants. Results indicate that
chemicals in the study area, in
combination with natural environmental
stresses (i.e., periodic drought) over a 15-
year period have screened for plant
species capable of growing under the
combined influence of both chemical and
natural environmental stresses.
The study area comprises one acre that
was taken out of use as an industrial
sludge lagoon and drained approximately
20 years ago, leaving high levels of
polyaromatic hydrocarbons (PAHs) (as
high as 20,000 ppm, total) and BTEX
compounds (benzene, toluene,
ethylbenzene, and xylenes) in the sludge.
Since then, the entire site has been
revegetated as a result of natural pro-
cesses starting with seed dispersal from
mature vegetation growing in the vicinity
of the basin. A healthy, biodiverse
community of 51 different plant species is
growing on the site now [as shown in the
photograph provided in the Internet
version of this newsletter].
Researchers compared the density of
seed-donor plants growing within a
1,200-meter radius of the sludge basin
with vegetation in the basin, finding the
composition of the basin plant community
does not reflect nearby seed-donor
populations (Figure 2). Most notable is
the prominence of mulberry and the
absence of Chinese tallow and willow in
the basin. These differences are attributed
to natural screening processes whereby
the current plant populations have proved
to be more capable of growth in the
existing chemical and environmental
conditions of the basin. In earlier
laboratory screening studies on rhizo-
sphere enhancement of microbial degra-
dation, mulberry was identified as the
potentially most influential species among
the 17 plants tested under similar condi-
tions.
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Figure 2. Comparison of Dominant Vegetation
MoniK rubra (mulberry tree)
Cvndon dactvion (Bermuda grass)
Heiianthus annum (sunflower)
Celtis laevigata (sugarberrv tree)
Salix nigra (wilbw tree)
Baccharis kalimifolia (Baccliaris bush)
Sapium sebiferum (Chinese tallow free)
Total percent
In Sludge Basin*
36.2
18.9
9.4
2.8
0
1.9
0
85.3
Radius of Basin*
5.0
9.0
2.0
7.0
2.0
25.0
27.0
97.8
* Percent relative coverage/abundance
Field data collected at the sludge basin
indicate that the concentration of PAHs in
the top two feet of material beneath
mature mulberry trees is only 10-20% of
the concentration originally deposited in
the sludge. The concentration of
contaminants in the lower root zone (2-4
feet) of mulberry averages about 50% of
that present in sludge beneath the root
zone. PAH-degrading bacteria have been
isolated from the rhizosphere, but not
from the non-rooted sludge material at 6-
foot depths. These data indicate that
mulberry seems to have the capacity for
sustained growth in PAH/BETX-
contaminated sludge under natural
conditions, and that its root zone fosters
the degradation of industrial contaminants
presumably by substrate release and
increased soil aeration during root
turnover.
Additional field and laboratory tests are
underway to evaluate mulberry's
phytoremediation potential and to develop
ecologically sound and safe
phytoremediation strategies for sustained,
long-term (15-20 years) degradation of
recalcitrant pollutants at hazardous waste
sites. Contact Dr. John Fletcher (Univer-
sity of Oklahoma, Department of Botany
and Microbiology) at 405-325-3174 or
Sunil I Shah (Union Carbide Corporation)
at 304-747-5234 for more information.
Phytoremediation of
Selenium-Laden Soils
by Gary Banuelos, Ph.D., U.S.
Department of Agriculture,
Agricultural Research Service
The U.S. Department of Agriculture
(USDA) is conducting two large-scale
field studies in areas of central California
where intense agricultural use of the land
has resulted in potentially toxic levels of
naturally-occurring selenium in soils.
USDA study results indicate that Brassica
species (such as mustard and canola) can
be used to hyperaccumulate and volatilize
soluble selenium in soil. Field data also
show that phytoremediation may provide
a practical and economically viable
method for reducing the selenium load
discharge into effluent in irrigated regions
of central California. Other western states
with extensive shale deposits, where
increased irrigation of agricultural lands
is increasing selenium solubilization, may
benefit from this approach.
Under greenhouse conditions, researchers
found that selenium concentrations fell by
nearly 50% after a period of 3-4 months,
with tissue concentrations of selenium
reaching levels as high as 600 ppm in dry
plant material. After four years of crop
rotations at one of the California study
sites with Brassica species, kenaf, and tall
fescue, total soil concentrations of
selenium fell by 25% from levels of 1.5-
2.0 ppm. Concentrations of soluble
boron, which is often found in
conjunction with selenium and also
potentially toxic to plants in high
concentrations, fell by nearly 20% from
levels of 5 -15 ppm. New eucalyptus
trees subsequently were replanted at this
site and intercropped with tall fescue,
which continues to manage the level of
selenium to a safe level predominantly
through plant volatilization.
On the second study site, poor-quality
ground water with high salinity, boron,
and selenium is used as irrigation water
on Brassica species planted for
phytoremediation. Following two years
of research, Brassica species now are
used in crop rotation with other agro-
nomic crops, such as sugar beets and
wheat, to maintain low selenium levels
whenever poor quality water is used for
irrigation. Additionally, minimizing the
buildup of soil selenium allows for
effective leaching of salts such as boron
out of the soil profile. The planting of
Brassica, itself, provides opportunities for
the production of oil as an agronomic
crop and for animal forage (pending
regulatory approval).
This approach to phytoremediation relies
upon combination of Brassica with other
plants, such as alfalfa or grasses, that
primarily volatilize selenium. In general,
USDA recommends consideration of
certain factors before implementing
phytoremediation, including: (1) soil
salinity and high concentrations of toxic
elements; (2) the presence of competitive
ions affecting chemical uptake; (3)
adverse climatic conditions; (4) water
management strategies that produce little
effluent; (S)unwanted plant consumption
by wildlife and insects; (6) plant destruc-
tion/utilization; and (7) stakeholder
acceptance.
These studies were precipitated, in part,
by the bioconcentration and apparent
toxicity of selenium found in the wetland
food chain at Kesterson National Wildlife
Refuge in central California. Researchers
identified high rates of embryo deformi-
ties and mortalities in aquatic birds
resulting from agricultural drainage to the
refuge. The USDA estimates that more
than 500,000 acres of soil in central
-------
California possibly are susceptible to
producing selenium-laden effluent. For
more information, contact Gary Banuelos
(USDA, Agricultural Research Service)
at 209-453-3100.
Biodegradation of
De-Icing Fluids
by Charles A. Bleckmann, Ph.D.,
Air Force Institute of Technology
Investigations conducted by the U.S. Air
Force Institute of Technology (AFIT),
Wright-Patterson Air Force Base, OH,
have shown that a component of aircraft
de-icing fluids—propylene glycol—
readily degrades in both high clay and
sandy soil systems. As the primary
components of commercial aircraft de-
icing fluids, both propylene glycol and
ethylene glycol commonly are detected in
streams receiving runoff from airports.
Their degradation creates a high oxygen
demand capable of disrupting receiving
streams. Collection and subsequent
treatment of spent fluids by land applica-
tion may be considered a remediation
technique.
In soil test systems, AFIT researchers
measured oxygen consumption and
carbon dioxide production (the process of
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respirometry) involved in propylene
glycol degradation. Respirometry served
as a sensitive measure of biological
activity in the laboratory environment,
and was used to compare the activity of
experimental controls. Propylene glycol
concentrations of 3,800-11,400 mg/kg
degraded (at 30°C) in 28 days by 20-28%
in clay soils, and by 2-6% in sandy soils,
without the addition of nutrients. De-
icing agent additives such as the corrosion
inhibitor tolyltriazole showed little
degradation.
Contact Capt. Laura Johnson or Lt.
AnnMarie Halterman-O'Malley (AFIT) at
937-255-3636 for more information on
these studies, or Dr. Charles Bleckmann
(AFIT) at 937-255-3636 (phone) or
cbleckma@afit.af.mil (e-mail) on other
site remediation research conducted by
the AFIT Department of Engineering and
Environmental Management.
New Phytoremediation
Bibliography Now
Available
The Phytoremediation Bibliography,
recently developed by the EPA
Phytoremediation Handbook Team in
conjunction with the Remediation
Technology Development Forum's
Phytoremediation Action Team, is a
comprehensive reference list containing
available abstracts and over 1,100
citations on phytoremediation or closely
related subjects. The bibliography will be
updated quarterly to include additional
abstracts and references for peer-reviewed
journal articles, conference presentations
and posters, book excerpts, and newspa-
per or magazine articles. Bibliography
searches may be conducted on-line from
the RTDF Internet site www.rtdf.org/
phytodoc.htm.
United States
Environmental Protection
Agency
Solid Waste and
Emergency Response
(5102G)
EPA 542-N-98-005
May 1998
Issue No. 29
-EPA TECH TRENDS
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