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Phytoremediation of Arsenic and other Heavy Metals
Richard C. Bost, Environmental Resources
Management, 15810 Park Ten Place, Houston, Texas 77084,
Tel: 281-600-1218, Email: rick.bost@erm.com
Dr. Martin L. McGregor, Malvaceae Research Center, 4111 E.
Northampton Place, Houston, Texas 77098, Tel:
979-921-0000, Email: mcgregor@pdq.net
Georgia Bost, Malvaceae Research Center, 4111 E. Northampton
Place, Houston, Texas 77098, Tel: 979-921-0000, Email: gbost@vbihibiscus.com
Heavy metals have accumulated in the soils of many industrial
sites as a result of various industrial and commercial
processes and waste disposal activities.
Heavy metals have also accumulated in agricultural
fields in the United States and elsewhere as a result of
the evaporation of irrigation waters and precipitation of
metal salts or the use of herbicides containing arsenic.
The heavy metals of most concern in industrial
sites include what are known in the U.S. as the RCRA heavy
metals. In
agricultural sites, arsenic, selenium and boron are the
primary metals of concern.
Phytoremediation (bioremediation using plants) to remove
heavy metals has been an area of increased research for
the past five years.
This paper presents a summary of the research and
compares the effectiveness of various plant species with
Malvaceae. Native
North American Malvaceae species grow in brackish settings
where heavy metals naturally accumulate.
Georgia Bost recognized their potential application
for phytoremediation and sought funding to assess their
potential. Malvaceae
species native to the United States were tested with the
support of funding from the U.S. Department of
Agriculture, resulting in the issuance of a U.S. patent
(international patenting is in progress).
The initial research found that Malvaceae species
were particularly effective at removing selenium and boron
from soils and irrigation water.
The species were effective in reducing other heavy
metals in soils at a test site. Subsequently, additional
funding from the U.S. Department of Agriculture was
obtained to assess the dosage-uptake relationship in order
to have a better basis for assessing the relative
effectiveness of Malvaceae phytoremediation versus other
options for addressing heavy metals in soils or irrigation
water. Replicate testing with controls was conducted using
irrigation water of differing concentrations of RCRA heavy
metals with different species and patented hybrids.
The research was designed to assess the
dosage-uptake relationship and to identify in what parts
of the plants the metals tended to accumulate.
Soil concentrations were tested periodically
through the studies and compared with controls.
The results provide a basis for estimating the
potential effectiveness of phytoremediation in larger
scale applications.
Brownfield Phytoremediation Using Salix Species and
Herbaceous Plants
Michel Labrecque, Institut de recherche en biologie
végétale, Montreal Botanical Garden, 4101 Sherbrooke
East, Montreal, Quebec, Canada, H1X 2B2. Tel:
514-872-1862, Fax: 514-872-9027, Email: mlabrecque@jbmontreal.net
Traian Ion Teodorescu, Institut de recherche en biologie végétale,
4101 Sherbrooke East, Montreal, Quebec, Canada, H1X 2B2.
Tel: 514-872-9027, Fax: 514-872-9027, Email: teodoret@magellan.umontreal.ca
Phytoremediation can be a
viable option to reduce soil pollutants and rehabilitate
brownfield sites. Field trials were established in a heavy
metal contaminated area of the City of Montreal where soil
analyses showed that Cu (416.8 mg/kg-1), Pb
(857 mg/kg-1), and Zn (899.4 mg/kg-1)
exceeded Canadians limits. In spring 2000, seeds of one
herbaceous species Brassica juncea L.
were sowed and the cuttings of two tree species Salix
miyabeana, Seem.
and S. viminalis L. were planted
using a split plots design. Two treatments were applied:
EDTA (ethylenediaminetetraacetic
acid) treated plots (T1) and untreated plots (T0).
The study compared metal concentration and content in
aerial parts (leaves, fruits, stems) and roots of each
species at the end of the first growing season and
assessed the effect of EDTA in metal transfer from soil to
plants. During this trial, no symptoms of phytotoxicity
were observed in the plants. The results showed that B.
juncea
transferred more Cu and Pb and less Zn from soil to their
tissues when compared with the two species of willows. In
the herbaceous species, the EDTA treatment resulted in a
positive effect on metal transfer. Generally, S.
viminalis transferred more metals than S.
miyabeana. The metal concentration in leaves was more
important compared to the total aerial parts concentration
(considered 100 %). For B.
juncea these proportions were: Cu=58.5 %, Pb=73.5 %,
Zn=51.5 % and for willows: 58.5 %, 82 % and 85.5 %
respectively. The
distribution of metals between aerial parts and roots was
different for each species. B.
juncea accumulated more metals (Cu, Pb and Zn) in its
aerial parts than in the roots whereas in the willows, Cu
and Pb, principally accumulated in the roots and Zn in the
aerial parts (mostly in the leaves).
At the end of the first growing season, the total
biomass yield of B.
juncea (annual plant) was higher than that of the
willows (perennial plants) and consequently total metal
plant accumulation was also more important. However,
previous studies suggest that over a long term period the
willows will be much more productive than B.
juncea. As biomass production is a determinant factor
of plant metal accumulation (beside metal concentration),
the willows can be successfully utilised in brownfield phytoremediation.
Increase
of Bioavailable Cd and Zn by Rhizosphere Bacteria
Associated with a Cd/Zn Hyperaccumulator, Sedum
alfredii
W.C. Li,
Croucher Institute for Environmental Sciences and
Department of Biology, Hong Kong Baptist University, Hong
Kong SAR, PR China, Email: waichin@gmail.com
Z.H.Ye, State Key Laboratory for Bio-control, School of
Life Sciences, Sun Yat-sen (Zhongshan) University,
Guangzhou 510275, PR China, Email: lsdyzhh@zsu.edu.cn
M.H. Wong, Croucher Institute for Environmental Sciences
and Department of Biology, Hong Kong Baptist University,
Hong Kong SAR, PR China, Email: mhwong@hkbu.edu.hk
(correspondence author)
Sedum
alfredii (Family:
Crassulaceae), a newly reported cadmium (Cd) and zinc (Zn)
hyperaccumulator native to China, can accumulate Cd and Zn
exceeding 1 000 and 10 000 mg kg-1 respectively
in its shoot (dry weight) when growing under metal
contaminated habitats. Several strains of bacteria were
isolated from the rhizosphere of
S. alfredii from different Pb/Zn mines in Hunan
Province and Zhejiang Province, China, which can resist
high levels of heavy metals. Among these strains, Burkholderia
cepacia showed the highest ability in mobilizing Cd
and Zn as well as resisting high concentrations of soluble
Zn (500 mg L-1). The soluble Zn concentration
in the medium increased from 13 to 72 and 99% (p<0.01)
after bacterial inoculation on the MS medium supplemented
with zinc oxide and zinc carbonate respectively and pH was
decreased from 7.00 to 2.93. The Cd concentration was also
increased from 8 to 96% (p<0.01) and pH was decreased to 2.65. Short chain organic acids
were also analyzed and the results indicated that oxalic
acid, tartaric acid and formic acid had a significant
correlation (p<0.01) with the concentrations of metals (Cd and Zn) mobilized
during the assay,
The effects of inoculation
of bacteria on the metal bioavailability, mobility and
leaching potential were also investigated in the soil
column experiment through single chemical extraction,
sequential extraction and in
situ soil solution extraction technique. Bacteria
inoculation significantly increased the water-soluble and
HOAc-soluble Zn and Cd, possibly by dissolution and
desorption from the secretion of proton and various
ligands. It is suggested that the role of bacteria in
increasing the bioavailability of Zn and Cd would be a
great significance for a successful phytoextraction of
metals from metal contaminated sites.
Plant
Spacing for Optimal Arsenic Phytoremediation using Pteris
cretica
Student
Presenter
Joshua
Goldowitz, Environmental Management & Safety
Department, Rochester Institute of Technology, 78 Lomb
Memorial Drive, Rochester, NY 14623-5604, Tel: 585
475-7018 Fax 585-475-7560, Email: jxgctp@rit.edu
Sean O’Neil, Environmental Management &
Safety Department, Rochester Institute of Technology, 78
Lomb Memorial Drive, Rochester, NY 14623-5604, Tel: 585
314-1175 Fax 585-475-7560, Email: swo1834@rit.edu
The brake ferns Pteris vittata and Pteris cretica have been
suggested for phytoremediation of arsenic contaminated
soil. Edenspace Systems Corporation has demonstrated the
practical application in an ongoing remediation project in
the Spring Valley area of Washington DC. where Pteris
species were grown on one foot centers. In that Pteris are
tropical to subtropical (USDA plant hardiness zone 7-10),
use in colder climates will be problematic. The plants
inability to over winter will require annual replanting,
and the radius of single-season root spread will determine
minimum planting density to ensure root coverage of the
remediation area. In 2004 researchers at Rochester
Institute of Technology’s Environmental Management
department determined the single season radial root spread
of P. cretica in a lab study using four soil types.
Three replicates of four soil types were prepared
in cubic 1 ft3 planting containers. Seedlings
of 4-6 fronds in 40 cm3 seed starting media
were planted centrally and grown under light with abundant
water. Plants were misted and fertilized and grown for
seven months to simulate one growing season. Soil was then
sectioned and excavated to determine root density Vs.
depth and distance from the plant. Root density was
determined using the standard measurement of dry root
mass/soil volume and using a novel GIS pixel-based
measurement of root length/soil volume. Preliminary
results indicate significant root growth beyond the
original starting media, but exponential decline in
density with distance from the planting center. This
indicates that most soil beyond .3 foot from the plant
crown will not be within a root rhisosphere and will
remain unremediated. An arsenic contaminated site planted
with P. cretica on 1 ft centers likely contains nodes of
remediated soil surrounded by unremediated soil after one
growing season.
Use of Conventional Crop Plants for the Removal of Heavy
Metals from a Severely Contaminated Industrial Site
John
Pichtel, Professor, Ball State University, Natural
Resources and Environmental Management, Muncie, IN
47306-0495, Tel: 765-285-2182, Fax: 765-285-2606, Email:
jpichtel@bsu.edu
The ability of commercial crop plants to extract lead (Pb),
cadmium (Cd), and zinc (Zn) from a metalliferous waste
disposal site in Western Europe was studied in the
greenhouse and in the field.
In the greenhouse, spinach (Spinacea
oleracea); cabbage (Brassica
oleracea); broad bean (Vicia
faba); and a grass mixture (red fescue, Festuca
rubra; ryegrass, Lolium
perenne; and spreading bluegrass, Poa
pratensis); were
grown on blast furnace slag or baghouse dust amended with
composted peat. Soil
Pb ranged from 12 to 5120 mg/kg, Cd from 1.0 to 275.2
mg/kg and Zn from 550 to169,900 mg/kg. In most cases the
majority of soil Pb, Cd and Zn occurred in the
organic-bound, carbonate-bound, and sulfide/residual
forms; relatively low percentages occurred in soluble and
exchangeable forms. Several species were capable of
accumulating and distributing soil metals to upper plant
parts. No plants were capable of growth on non-amended
soil material. Metal uptake was partly a function of the
chemical forms occurring in soil.
For example, tissue metals correlated with soluble
and exchangeable soil metal concentrations. Field
plots established at the waste site were treated with
composted peat or cattle manure, or a mixed NPK
fertilizer. Plots were seeded with spinach, cabbage, and a
grass mixture. Soil Pb, Cd and Zn tended to accumulate in
roots with variable translocation to upper plant parts.
Dry matter production was greatest for the
composted peat treatment and lowest for the control (no
soil amendments) treatment. Ground cover was most
extensive on the peat treatment, followed by the cattle
manure and NPK fertilizer. No significant leaching of Pb,
Cd, or Zn occurred in any treatment.
Phytoextraction
and Phytovolatilization of Arsenic From As-contaminated
Soils by Pteris
Vittata
Masayuki
Sakakibara, Ehime
University, 2-5 Bunkyo-cho, Matusyama 790-8577, Japan,
Tel: 81-89-927-9649, Fax: 81-89-927-9630, Email: sakakiba@sci.ehime-u.ac.jp
Aya
Watanabe, Ehime University, 2-5 Bunkyo-cho, Matusyama
790-8577, Japan, Tel: 81-89-927-9649, Fax: 81-89-927-9630,
Email: aya@sci.ehime-u.ac.jp
Sakae
Sano, Ehime University, 3 Bunkyo-cho, Matusyama 790-8577,
Japan, Tel: 81-89-927-9443, Fax: 81-89-927-9396, Email: sano@ed.ehime-u.ac.jp
Masahiro
Inoue, Ehime University, 2-5 Bunkyo-cho, Matusyama
790-8577, Japan, Tel: 81-89-927-9634, Fax: 81-89-927-9630,
Email: inouhe@sci.ehime-u.ac.jp
Toshikazu Kaise, Tokyo
University of Pharmacy and Life Science, 1432-1 Horinouchi,
Hachioji 192-0392, Japan, Tel:
81-426-76-6770, Fax: 81-426-76-5084, Email: kaise@ls.toyaku.ac.jp
Phytoremediation
of metal contaminated soil and water offers a lower cost
method for remediation and some extracted metals may be
recycled for value. Both use of the phytoextraction and phytovolatilization of
metals by plants offer realistic remediation on commercial
project. Arsenic
is of great environmental concern due to its extensive
contamination and toxicity. Ma et
al. (2001) has recently discovered the first known and
extremely efficient,
arsenic hyperaccumulating plant, Pteris
vittata. If we can use phytovolatilization for As-contaminated soils,
it minimizes the production of As-laden plant material and
the duration of remediation.
Material
balance of As between uptake by Pteris
vittata and
reduction from As-polluted soils has not been kept based
on our results of many greenhouse experiments.
Vapor sample were collected to determine
volatilization of arsenic compounds from leaves of Pteris
vittata grew in
As-polluted soil to the atmosphere.
A low-density polyethylene bottle was completely
placed over each stem and sealed on the open bottleneck
with sealant and tape to produce a tight seal around the
stem and chambers during 2-7days.
The bottles were fixed in the same location during
sample collection. Concentration
of arsenic in trap samples was measured by ICP-MS and
speciation of arsenic was analyzed HPLC/ICP-MS system.
Concentrations
in collected water samples (ca. 3-10ml) reached 10.68-30.8
mg-As/L (2-7 days). Percentages
of arsenic components in one sample are 37 % for arsenite
and 63 % for arsenate.
The results of our experiments suggest that Pteris
vittata is a plant species that has shown to be particularly
effective at volatilizing As; it removed about 90% of the
total uptake of As from As-contaminated soils in
greenhouse, like the subtoropics. However,
the
problem of whether volatile arsenic from Pteris vittata is still
toxic or not still remains
unknown.
A
Full-Scale Phytoremediation Approach at a Former MGP:
Objectives, Concept, Design and Implementation
Carl E. Tammi,
PWS, ENSR, 2 Technology Park Drive, Westford, MA, 01886,
Tel: 978-589-3065, Fax: 978-589-3100, Email: ctammi@ensr.aecom.com
Paul Exner, P.E. Bay State Gas/Nisource, 300
Friberg Parkway, Westborough, MA, 01581, Tel:
508-836-7256, Fax: 508-836-7072, Email: pexner@nisource.com
Robert Cleary, Bay State Gas/Nisource, 300
Friberg Parkway, Westborough, MA, 01581, Tel:
508-836-7275, Fax: 508-836-7072, Email: rcleary@nisource.com
David Macone, P.E, ENSR, 2 Technology Park
Drive, Westford, MA 01886, Tel: 978-589-3000, Fax:
508-589-3100, Email: dmacone@ensr.aecom.com
ENSR developed an
innovative Phytoremediation approach for a former MGP Site
in New Hampshire with the objectives to a) provide
hydraulic control to slow and reduce groundwater migration
off-site, b) provide the potential for passive aerobic
microbial rhizospheric degradation of residual BTEX in
groundwater, and c) provide an attractive greenspace at
the site in the form of a robust, mixed deciduous and
coniferous forest. A
concept was developed to promote the establishment of
deeply rooted phreatophytic live cuttings to tap the
capillary fringe of the groundwater table to promote the
natural “pump and treat” process of evapotranspiration,
thereby reducing the hydraulic gradient on-site, and
slowing the migration of residual MGP by-products in the
groundwater. Groundwater
Flux simulations were modeled for existing and proposed
conditions with assumptions for the successful
interception of the groundwater table to establish some
baseline goals and to support the rationale.
Integral to the concept is getting the trees to
send their roots deep into the soil (capillary fringe 3-10
ft bgs) to use this water and not just water infiltrating
from precipitation. ENSR’s design approach integrated
the installation of densely planted live cuttings of trees
deep into the soil (2-3 ft bgs) along with traditional
bare root installations (1-2 ft bgs), all over 1 acre in a
sandy loam upland adjacent to two streams.
Over 1,000 trees were installed.
To further promote the roots to penetrate the
capillary fringe, a low-tech irrigation system consisting
of 3-4 ft (2 inch diameter PVC) irrigation tubes were
placed with each tree and set below the bottom of the
planting. ENSR designed and constructed the system in 2005
and continued irrigation in 2006.
To date the system has experienced 92% survival of
the plantings and early indications are that roots are
extending downward toward the capillary fringe.
This poster presents the concepts, objectives,
design and construction.
Enhancing the Phytoremediation of RDX with Mycorrhizal Fungi
Phillip Thompson, Seattle University, Dept. of
Civil & Environmental Engineering, 900 Broadway- 524
ENGR, Seattle, WA 98122, Tel: 206-296-5521, Fax:
206-296-2173, Email: thompson@seattleu.edu
Previous studies have shown that the phytoremediation of RDX
can lead to its bioaccumulation in leaf tissues. Bioaccumulation has many undesirable ecological effects, such
as the potential for food-chain contamination or increased
transport via leaf litter.
The principle objective of this research was to
decrease the bioaccumulation of RDX in hybrid poplar trees
(Populus deltoides
´
nigra, DN34) and
switchgrass (Panicum
virgatum) by exploiting the naturally occurring
symbiotic relationship between these plants and
mycorrhizal fungi. Mycorrhizal
fungi usually perform the function of providing nutrients
to the plant that may be scarce within the soil such as
phosphorus or nutritional metals such as zinc.
To date, the vast majority of phytoremediation
research has neglected the potential benefits of these
fungi. This
is especially surprising given the fact that other
basidiomycetes such as the white rot fungus (Phanerochaete
chrysosporium)
have been proven to mineralize RDX.
Prior to dosing with [U-14C]RDX,
plants were grown in a greenhouse for periods ranging from
one to four months in order to establish the plant-fungi
symbiosis. The
results from this research have indicated that the
presence of mycorrhizal fungi does not significantly (p
< 0.05) decrease the concentration of RDX in leaf
tissues relative to controls for experimental periods
ranging from 7 to 30 days.
Results also indicated that a volatile organic
compound was emitted by both plant species. This is the first evidence that a plant can facilitate the
transformation of a non-volatile anthropogenic chemical to
a volatile organic chemical.
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