BZ572 - Phytoremediation
Elizabeth Pilon-Smits
Biology Department
E413 ANAZO
491-4991
epsmits@lamar.colostate.edu
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Please write on piece of paper:
• Degree, major/department, reg./auditing?
• What is your career goal?
• How does phytoremediation fit in?
• Any particular aspects of phytoremediation
you are most interested in?
BZ572 – Course Info
Text:
webct
No book, only papers from course website
Topics:
- Intro to phytoremediation
- Phyto of inorganics*)
- Phyto of organics*)
- 1 Lab expt, 1 trip to a lab, 1 field trip (if interest),
5 guest lectures, in-class exercises, job info
*) mechanisms of uptake, translocation, detoxification,
effects of soil, microbes on remediation, approaches to
enhance phyto efficiency, including genetic engineering
Grading: Conventional, no curving
Exams: 50% of total grade
- 1 midterm + 1 final exam (not comprehensive)
essay questions
Term paper & presentation: 30% of grade
- write web page/proposal/review + present
In-class participation: 20% of grade
- lab report, in-class group assignments,
literature discussions
Introduction to Phytoremediation
• History
• Status
• Uses
• Advantages
• Limitations
• Phytoremediation strategies
History of phytoremediation
• for centuries: wetlands used for
waste treatment in Europe
• last century: metal hyperaccumulator
plants discovered - used as indicators for mining
• 1970s: - clean water act, clean air act
• 1980s:
- superfund act (1986 - 8.5 billion $)
- idea to use hyperaccumulator
plants for metal cleanup (Chaney)
History of phytoremediation (cont.)
• 1994: phytoremediation term coined
(Ilya Raskin)
massive interest from gov. & industry
- DOE phytorem. workshop
- first phytorem. company (Phytotech)
• 1995: first phytorem. conference
phytoremediation takes off
History of phytoremediation (cont.)
•(Raskin)
• 1994: Term phytoremediation first used
• 1995: First phyto conference
Columbia MO
• 2000: EPA phyto conference
• 2000: 1st phyto faculty positions
• 2000: 1st phyto course (this one)
• 2001, 2003: 1st, 2nd phyto call for proposals
•(NSF/EPA/DOE)
• 2000, 2001: 1st, 2nd professors in phyto
•(U Mich, U S-Carolina)
Status of phytoremediation
• U.S. phytoremediation market
(Glass, 1999, 2004 pers. comm.)
1999
2004
$ 30 - 49 million / yr
$ 100-150 million / yr
• World phytoremediation market
1999
$ 34 - 58 million
• Total remediation market
US: $ 6-8 billion/yr
World: $ 25-50 billion/yr
Status of phytoremediation (cont.)
• 9 purely phytorem. companies
• 7 constructed wetland companies
• > 40 consulting/engin. companies
that also do phytoremediation
• ~200 field projects
- funded mostly by EPA, DOD, DOE
- some commercial/joint projects
Uses of phytoremediation
Remediation of different media:
•
•
•
•
air
soils, sediments
groundwater
wastewater streams
- industrial
- agricultural
- municipal, sewage
Uses of phytoremediation (cont.)
Remediation of different pollutants:
• inorganics:
- metals (Pb, Cd, Zn, Cr, Hg)
- metalloids (Se, As)
- “nutrients” (K, P, N, S)
- radionuclides (Cs, U)
• organics:
- PCBs
- PAHs
- TCE
- TNT
- MTBE
- pesticides
- petroleum
hydrocarbons
Etc.
Uses of phytoremediation (cont.)
Remediation using different systems:
• farming polluted soil
• irrigation with polluted groundwater
• letting trees tap into groundwater
• letting plants filter water streams
constructed wetlands, hydroponics
different systems: Hydraulic barrier
different systems:
• Vegetative cap
different systems:
• Constructed wetlands
different systems:
hydroponics with polluted wastewater
Roots of mustard
Extend into effluent
Acting as filters for heavy metals
Uses of phytoremediation (cont.)
Remediation using different plants
Properties of a good phytoremediator:
• high tolerance to the pollutants
• high biomass production, fast growth
• large, deep root system
• good accumulator/degrader of pollutant
• able to compete with other species
• economic value
Uses of phytoremediation (cont.)
Popular plants for phytoremediation
• trees
yellow poplar
various organics
metals
gum
tree
poplar
willow
Uses of phytoremediation (cont.)
Popular plants for phytoremediation (cont.):
Brassicaceae:
• For inorganics
• grasses
Thlaspi
Alyssum
Brassica juncea
Uses of phytoremediation (cont.)
Popular plants for phytoremediation (cont.):
various grasses
for organics
hemp
buffalo grass
red fescue
for inorganics
kenaf
bamboo
Uses of phytoremediation (cont.)
salicornia
Popular plants for phytoremediation
aquatic plants
cattail
parrot feather
halophytes
for inorganics
for organics
poplar, willow
reed
spartina
Phytoremediation
Solar energy
In situ
Fossil fuels for energy
Ex situ
Mechanical/chemical treatment
• Soil washing
• Excavation + reburial
• Chemical cleanup of soil/water
• Combustion
Phytoremediation vs.
Mechanical/chemical treatment
Advantages of phytoremediation
• Cheaper ~10 - 100x
Excavation & reburial: up to $1 million/acre
Revegetation: ~$20,000/acre
Phytoremediation vs.
Mechanical/chemical treatment
Advantages of phytoremediation (cont.)
• Less intrusive
• Can be more permanent solution
• Better public acceptance
Phytoremediation vs.
Mechanical/chemical treatment (cont.)
Limitations of phytoremediation
• Can be slower
Limited by rate of biological processes
-Accumulation in plant tissue: slow
e.g. metals: average 15 yrs to clean up site
- Filter action by plants: fast (days)
- Metabolic breakdown (organics): fairly fast
(< 1yr)
Phytoremediation vs.
Mechanical/chemical treatment (cont.)
Limitations of phytoremediation (cont.)
• Limited root depth
Trees > prairie grasses > forbs, other grasses
Max depth ~5 m
Can be increased
up to 20m with
“deep planting”
Phytoremediation vs.
Mechanical/chemical treatment (cont.)
Limitations of phytoremediation (cont.)
• Plant tolerance to pollutant/conditions
- Bigger problem with metals than organics
- Can be alleviated using amendments, or
treating hot spots by other method
• Bioavailability of contaminant
- Bioavailability can be enhanced by amendments
So, when choose phytoremediation?
• Sufficient time available
• Pollution shallow enough
• Pollutant concentrations not phytotoxic
• $$ limited
Note: Phyto
may be used in conjunction with
other remediation methods
For very large quantities of mildly
contaminated substrate:
phytoremediation only cost-effective option
Phytoremediation processes
Phytoremediation processes
phytostabilization
• Phytostabilization:
pollutant immobilized in soil
- Metals
- Non-bioavailable organics
1. Plants reduce leaching, erosion, runoff
 pollutant stays in place
2. Plants + microbes may transform pollutant
to less bioavailable form
(e.g. metal precipitation on roots)
Phytoremediation processes
phytostimulation
• Phytostimulation: plant roots stimulate
degradation of pollutant
by rhizosphere microbes
Organics
e.g. PCBs, PAHs
bacteria, fungi
Phytoremediation processes
phytodegradation
• Phytodegradation:
plants degrade pollutant,
with/without uptake, translocation
Via enzymes,
e.g. oxygenases
nitroreductase
Certain organics
e.g. TCE, TNT, atrazine
in tissues or
in root exudate
Phytoremediation processes
phytoextraction
accumulation
• Phytoextraction: pollutant accumulated
in harvestable plant tissues
mainly inorganics:
metals
metalloids
radionuclides
Plant biomass may be used
(e.g. to mine metals, or non-food industrial use)
or disposed after minimizing volume
(incineration, composting)
Phytoremediation processes
phytovolatilization
• Phytovolatilization: pollutant released
in volatile form into the air
some metal(loid)s: Se, As, Hg
some volatile organics: TCE, MTBE
Phytoremediation applications may involve
multiple processes at once
accumulation
volatilization
stabilization
degradation
Rhizofiltration
water
• Rhizofiltration: pollutant removed from
water by plant roots in hydroponic system
for inorganics
metals
metalloids
radionuclides
Plant roots & shoots harvestable
(may be used to mine metals)
or disposed after minimizing volume
• Hydroponics for metal remediation:
75% of metals removed from mine drainage
Rhizofiltration
Involves:
• phytoextraction
• phytostabilization
• Constructed wetland for Se remediation:
75% of Se removed from ag drainage water
Involves:
•phytoextraction
• phytovolatilization
• phytostabilization
• (rhizofiltration)
• (phytostimulation)
• Natural attenuation: polluted site left alone
but monitored
• Vegetative cap: polluted site revegetated,
then left alone, monitored
with/without
adding
clean topsoil
Hydraulic barrier
Water flow redirected
Pollutants intercepted
H2O
Phytoremediation project (1996-)
(Phytokinetics inc.)
Oregon site
Soil polluted with PAHs
Planted with grass (Lolium perenne)
Results:
bare soil: some PAH removal
vegetated soil: increased PAH removal (~4x)
Process? Phytostimulation/phytodegradation
Phytoremediation project (1995-1998)
(Phytotech inc.)
New Jersey site
Soil polluted with lead (Pb)
Planted with Indian mustard (Brassica juncea)
Results (after 3 growing seasons):
bare soil: 6% reduction in Pb
vegetated soil: 29% reduction in Pb
Process?
Phytoextraction
Phytoremediation project (1997)
(COE)
Mississippi site
Groundwater polluted with TNT
pumped through constructed wetland
Results:
95% reduction in TNT
endogenous plant enzymes found to
degrade TNT
Process?
Phytodegradation
Some light reading:
Print from Course Website
•EPA: Citizen’s guide to Phytoremediation
•EPA: Citizen’s guide to Natural Attenuation
•Pilon-Smits, 2005
Phytoremediation (review)
Ann Rev Plant Biology