|
A Dynamic Feedback Model of Plant-Soil Interactions
Affecting Metal Accumulation
Jennifer K. Saxe, Gradient Corporation, Cambridge, MA
Christopher
A. Impellitteri, U.S. EPA National Risk Management
Research Laboratory, Cincinnati, OH
Herbert E. Allen, University of Delaware, Newark, DE
Phytoremeditaion
of Persistent Organic Pollutants (POPs) in Soil
Jason
C. White, The Connecticut Agricultural Experiment Station,
New Haven, CT
Mary-Jane Incorvia, The Connecticut Agricultural
Experiment Station, New Haven, CT
Laboratory
Measurements of Storm-Water Quality Improvement in
Detention Ponds- Phytoremediation Study
Jeffrey
Weiss, University of Minnesota, Minneapolis, MN
Miki Hondzo, University of Minnesota, Minneapolis, MN
John Gulliver, University of Minnesota, Minneapolis, MN
Michael
Semmens, University of Minnesota, Minneapolis, MN
David Biesboer, University of Minnesota, St Paul, MN
Global
Enzymatic Activies - Potential Tools in Assessment of
Phytostabilization Strategies
Ioana G. Petrisor, University of Southern California, Los
Angeles, CA
J. Michael Kuperberg, Florida State University,
Tallahassee, FL
Ioan I. Lazar,
Institute of Biology of Romanian Academy, Bucharest,
Romania
Monitoring
the Process of Phytoextraction of Zinc and Cadmium by
Indian Mustard Using Reflective Spectrometry
B. B. Maruthi Sridhar, Mississippi
State University, Starkville,
MS
Yi Su, Mississippi State University, Starkville,
MS
David L.
Monts, Mississippi State University, Starkville,
MS
Effects
of Burrowing Earthworms on Phytoremediation of Pb/Zn Mine
Tailings
Ma Ying, Hong Kong Baptist University, Hong Kong
SAR, PR China
Ming H. Wong, Hong Kong Baptist University, Hong Kong SAR,
PR China
Nicholas M. Dickinson, Liverpool John Moores University,
Liverpool, UK
A
Dynamic Feedback Model of Plant-Soil Interactions
Affecting Metal Accumulation
Jennifer
K. Saxe, Gradient Corporation, 238 Main Street, Cambridge,
MA 02142, Tel: 617-395-5000, Fax: 617-395-5001
Christopher A. Impellitteri, U.S. EPA National Risk
Management Research Laboratory, 26 W. Martin Luther King
Drive, MS CHL, Cincinnati, OH 45268, Tel: 513-487-2872,
Fax: 513-569-7879 Herbert E. Allen, University of
Delaware, Department of Civil and Environmental
Engineering, 354 DuPont Hall, Newark, DE 19716, Tel:
302-831-8449, Fax: 302-831-3640
A great
deal of research effort has been expended to develop
predictive models for the determination of phytoavailable
fractions of potentially toxic metals in soils.
Such a model is useful in screening-level
ecological risk assessment and in determining the
feasibility of phytoremediation for a site.
Much of this research has focused on the physico/chemical
aspects of metals' binding and mobility in soil, often as
a function of pH and other soil properties.
"Supply-side" models considering only
metal-soil interactions (including sequential extraction
techniques), neglect to consider the dynamic nature of
root interactions with rhizosphere soil. It is qualitatively well understood that root exudates,
excreted primarily in response to the presence of
macronutrients, significantly alter soil chemistry in the
vicinity of plant roots.
There is overlap in the soil properties that
influence metal solubility and plant root responses (e.g.
pH), but some factors exclusively influence plants (e.g. N) and are typically not measured in supply-side models.
A dynamic feedback-control model of plant roots,
considering soil chemistry, its influence on root
exudations, and the resulting quantitative impact of those
exudations on metal uptake, was developed as a computer
model using Simulink (The MathWorks, Inc.).
The model uses principles of both soil chemistry
and plant physiology, and was calibrated using data from
several plant species grown in field-contaminated soils
with and without nutrient amendments.
A wide range of soils from three continents, some
historically contaminated through biosolids application or
other anthropogenic sources, were used.
This model allows estimation of the concentration
of metals in plant tissues based on soil properties, and
when soil properties are altered.
For example, phosphorus influences both soluble
metal in soil, and plant biochemical pathways.
The model predicts changes to the amount of zinc
accumulated by Indian mustard (Brassica
juncea) for differing phosphorus amendments in soil.
Phytoremediation
of Persistent Organic Pollutants (Pops)
in Soil
Jason
C. White, Department of Soil and Water, The Connecticut
Agricultural Experiment Station, 123 Huntington Street,
New Haven, CT 06504, Tel: 203-974-8523, Fax: 203-974-8502
MaryJane Incorvia Mattina, Department of Analytical
Chemistry, The Connecticut Agricultural Experiment
Station, 123 Huntington Street, New Haven, CT 06504, Tel:
203-974-8449,Fax:
203-974-8502
Persistent
organic pollutants are of environmental concern because of
their toxicity, recalcitrance in natural solids, global
distribution, and resistance to remediation.
There is evidence that certain plants effectively
accumulate these weathered residues from soil, suggesting
phytoremediation as a treatment approach.
Field experiments were conducted to quantify the
uptake and translocation of weathered
p,p’-DDE and chlordane from soil by a range of plant
species. Not
suprisingly, crops of different genera varied considerably
in their ability to extract Pops
from soil. Root:soil
concentration factors, defined as the ratio of contaminant
(ng/g,
dry weight) in the roots to that in the soil, approached
16 for certain species of pumpkin and squash but ranged
from 0.5-4 for species of melon, cucumber, spinach,
lettuce, alfalfa, mustard, vetch, and rye. Somewhat
suprisingly, within single species of squash and pumpkin,
individual cultivars of demonstrated greater than an order
of magnitude variation in the root:soil concentration
factors. Although
root tissues routinely contain the highest contaminant
concentration, this compartment comprises less than 5% of
the plant biomass. Consequently,
in many species tested, more than 85% of the contaminant
is present in the shoot system.
We speculate that the crop observed variability in
contaminant uptake results from species-specific
differences in root exudation.
Low molecular weight organic acids (citric, oxalic,
malic, malonic, tartaric, succinic) known to be root
exudates increase the abiotic desorption of weathered Pops
from soil by up to 50%.
These same organic acids also increase the aqueous
concentration of extracted polyvalent metal ions (Al, Fe,
Mn, Mg, Ca, P) from soil by up to 2 orders of magnitude.
We hypothesize that root exudates such as organic
acids chelate structural metal ions from the soil,
resulting in a partial destruction of the solid matrix and
subsequent increase in the availability of previously
sequestered contaminants
Laboratory
Measurements of Storm-Water Quality Improvement in
Detention Ponds – Phtyoremediation Study
Jeffrey
Weiss, St. Anthony Falls Laboratory, Department of Civil
Engineering, University of Minnesota, Mississippi River at
3rd Ave SE, Minneapolis, MN 55414, Tel:
612-627-4588, Fax: 612-627-4609
Miki Hondzo, St. Anthony Falls Laboratory, Department of
Civil Engineering, University of Minnesota, Mississippi
River at 3rd Ave SE, Minneapolis, MN 55414,
Tel: 612-627-4598, Fax: 612-627-4609
John
Gulliver, Department of Civil Engineering, University of
Minnesota, 500 Pillsbury Drive, Minneapolis, MN 55414 Tel:
612-625-3080, Fax: 612-626-7750
Michael Semmens, Department of Civil Engineering,
University of Minnesota, 500 Pillsbury Drive, Minneapolis,
MN 55414 Tel: 612-625-9857, Fax: 612-626-7750
David Biesboer, Department of Plant Biology, University of
Minnesota, 220 Biological Sciences Center, 1445 Gortner
Ave., St. Paul, MN 55108, Tel: 612-625-1799, Fax:
612-625-1738
Urban
best management practices are traditionally used to
improve water quality in storm-water runoff.
Among the storm-water management practices that
have been studied, the most promising and best understood
are detention ponds and retention ponds.
One of the major characteristics of detention ponds
is the ability of the plants that are present to
effectively remove pollutants from the runoff.
In partnership with the Minnesota Department of
Transportation, three wetland grass species native to
Minnesota (Scirpus
validus, Spartina
pectinata, and Glyceria
grandis) were chosen for analysis of their
phytoremediation capabilities. These are long-lived, perennial species that are well adapted
to conditions commonly found along roadsides.
Analysis of urban storm-water runoff in Minnesota
and around the country revealed that zinc, copper,
cadmium, and lead were the pollutants of greatest concern
and had the greatest potential to exceed EPA and Minnesota
Pollution Control Agency guidelines for non-point source
discharges, even after treatment by detention ponds.
The three selected species were grown in hydroponic
nutrient solutions that were spiked with average urban
storm-water runoff concentrations of Zn, Cu, Cd, Pb, to
determine their ability to accumulate these pollutants in
their harvestable biomass.
The ability of the plants to remove phosphorus and
chloride from solution were also analyzed.
Surface waters in Minnesota are particularly
susceptible to phosphorus loadings, and the long winters
result in the application of large amounts of deicing
salts that end up in the runoff.
In addition to the hydroponic reactor study, the
plants were also grown in flow reactors that simulate
detention pond conditions.
Ioana
G. Petrisor, University of Southern California, Department
of Civil and Environmental Engineering, 3620 S. Vermont
Ave., KAP 210 – MC 2531, Los Angeles, CA, 90089-2531,
Tel: 213-740-059,4Fax: 213-744-1426, Email: petrisor@usc.edu
J.
Michael Kuperberg, Institute for International Cooperative
Environmental Research, Florida State University, 226
Morgan Building, 2035 East Paul Dirac Drive , Tallahassee,
FL 32310-3700, Tel: 850-644-5524, Fax: 850-574-6704,
Email: mkupe@mailer.fsu.edu
Ioan
I. Lazar, Institute of Biology of Romanian Academy, Spl.
Independentei 296, CP 56-53, sector 6, 79651 Bucharest,
Romania, Tel: 401 2239072, Fax: 401 2219071, Email:petad@fx.ro
The
complexity of environmental pollution reported nowadays
all over the world increases the demand for innovative,
simple assessment methods in the view of remediation
strategy selection and monitoring. Phytostabilization, an
emerging technology based on the use of plants to reduce
the risk of contaminant migration, relies on the ability
of plant species to develop a healthy vegetative cover
with good stability in time, when grown on contaminated
materials. The success of a field application is rather
hard to predict, even after years of greenhouse tests. Due
to the strong interrelation between plants and
microorganisms, it is expected that any change in the size
and diversity of microbial population from contaminated
material to accurately reflect the material capacity to
support vegetation and the evolution of vegetation in
time. This paper discusses the possibility of using
several global enzymatic activities (dehydrogenase,
phosphatase, urease) from phosphogypsum (PG) tailings in
the selection of best plant species and PG treatments for
a field deployment of phytostabilization. Several plant
species were cultivated on PG with addition of various
amendments in the greenhouse. Global enzymatic activities
from PG were studied periodically and compared with plant
growth intensity and metal uptake. Results over only 6
months of trial showed generally a correlation between
plant development and the studied enzymatic activities
(reflecting microbial population), but sharp differences
between the various species of plants. These results
allowed the selection of plants and treatments to be used
in the field. Such a deployment was carried out and proved
successful in establishment of vegetation on PG stacks,
with a good vegetative growth recorded up to date, after
more than 3 years. However, it was observed that some
plant species with good greenhouse development, but lower
enzymatic activities recorded in their rhizosphere area,
were not stable in time and perished after 1 year in the
field. This work suggests the potential of using global
enzymatic activities in assessment and monitoring of
phytostabilization strategies.
B.
B. Maruthi Sridhar, Diagnostic Instrumentation
& Analysis Laboratory (DIAL), Mississippi State
University, 205 Research Blvd, Starkville,
MS 39759, Tel:
601-325-9044, Fax: 662-325-8465
Yi Su, Diagnostic Instrumentation & Analysis
Laboratory (DIAL), Mississippi State University, 205
Research Blvd, Starkville,
MS
39759, Tel:
601-325-3286, Fax: 662-325-8465
David L.
Monts,
Diagnostic Instrumentation & Analysis Laboratory
(DIAL), Mississippi State University, 205 Research Blvd, Starkville,
MS
39759, Tel:
601-325-7389, Fax: 662-325-8465
The long-term objective of this research is to monitor surface and
subsurface contamination by way of remote sensing of plant physiological
status growing in metal-contaminated environments.
The focus of the current research is to seek
spectral signatures that indicate the impact and content
of heavy metals in the leaves and canopies of the living
plants. Potted plants of Indian
Mustard (Brassica
juncea) were grown for five weeks before getting
subjected to the heavy metal treatment.
The heavy metals Zn and Cd were
applied to the plants at medium and high level
concentrations and in combination of medium Zn
and Cd concentration.
The reflectance spectra (from 350nm to 2500nm)
of
the plant canopy were collected daily using a portable spectroradiometer with both solar irradiation in the field and
artificial illumination inside a laboratory. Chemical analysis of harvested plant shoots showed significant
amount of metal accumulation. Spectral analysis revealed that the reflectance spectra in the near IR region (from
780nm to 1350nm) are closely correlated to metal
accumulation in plant shoots.
Further in-depth spectral analysis shows that the band ratio of the
spectral reflectance at 1110 nm and 810 nm might be used
as an indicator for metal accumulation in plant shoots.
This study suggests that
NIR reflectance spectra might be used as a reliable, non-intrusive, non-contact
monitor for
the
metal phytoextraction processes.
Effects
of Burrowing Earthworms on Phytoremediation of Pb/Zn Mine
Tailings
Ma
Ying, Biology Department, Hong Kong Baptist University,
Hong Kong SAR, PR China, Tel: +852-233-97050, Fax:
+852-233-95995
Ming H. Wong, Institute for Natural Resources and
Environmental Management, Hong Kong Baptist University,
Hong Kong SAR, PR China, Tel: +852-233-97050, Fax:
+852-233-95995
Nicholas M. Dickinson, School of Biological and Earth
Sciences, Liverpool John Moores University, Byrom Street,
Liverpool, L3 3AF, UK, Tel: +44-151-231-2190, Fax:
+44-151-207-3224
Difficulties
with reclamation of metalliferous mine tailings to soft
end-uses are associated with inadequate and extreme soil
conditions for plant and animal colonisation, and the risk
of dispersion of metals to the wider environment.
Establishing trees on these spoils potentially provides an
effective, low-cost, low-risk and long-term
phytoremediation option.
To be confident this is a satisfactory form of
reclamation, we need to know whether a developing stand of
trees and associated ecological processes either (i)
removes mobile pools of metals from contaminated soils or
(ii) immobilise these pools, rendering them harmless.
One associated process in particular concerns the
colonisation of developing soils by earthworms and the
effects of their burrowing activities. Earthworms
contribute to the development of soil from spoil and, in
normal soils, are beneficial to plant growth.
Potentially, however, earthworms may change the
bioavailability of heavy metals and subsequent ecosystem
dispersion. Our
project studied the effects of a common tropical burrowing
earthworm, Pheretima
guillelmi, on remediation of Pb/Zn mine tailings by
planting an N-fixing woody shrub, Leucaena
leucocephala. The
results showed that L. leucocephala could grow successfully on tailings with 25% (w/w)
soil amendment. P. guillelmi could survive and actively burrow in soils added with
as much as 50% tailings, and they significantly increased
root:shoot ratio and nutrient (N/P) uptake by L.
leucocephala, stimulated plant growth and increased
dry weight yields. However,
P. guillelmi
increased bioavailable metal concentrations in soil
accompanying with a direct increase of metal uptake in
plant tissues. This
had most effect on establishment of younger plants, but
there was evidence that acclimation of L. leucocephala to Pb/Zn mine tailings was improved by earthworm
inoculation. This
evidence shows that modeling the effects of soil animals
on metal mobility is a vital component of the remediation
process.
Top
|
