BZ572 - Phytoremediation
Elizabeth Pilon-SmitsBiology Department
E413 ANAZO491-4991
Let’s hear from you
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: 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
webct
Exams: 50% of total grade- 1 midterm + 1 final exam (not comprehensive)
Grading: Conventional, no curving
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
• Phytoremediation strategies
• Advantages
• Limitations
History of phytoremediation• for centuries: wetlands used for
waste treatment in Europe
• last century: metal hyperaccumulatorplants discovered - used as indicators for mining
• 1980s: - superfund act (1986 - 8.5 billion $)- idea to use hyperaccumulator plants for metal cleanup (Chaney)
• 1970s: - clean water act, clean air act
History of phytoremediation (cont.)
• 1995: first phytorem. conference
phytoremediation takes off
• 1994: phytoremediation term coined (Ilya Raskin)
massive interest from gov. & industry- DOE phytorem. workshop - first phytorem. company (Phytotech)
History of phytoremediation (cont.)
• 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)
• 1995: First phyto conference Columbia MO
• 1994: Term phytoremediation first used•(Raskin)
• U.S. phytoremediation market
1999 $ 30 - 49 million / yr
2004 $ 100-150 million / yr
• World phytoremediation market
1999 $ 34 - 58 million
Status of phytoremediation
(Glass, 1999, 2004 pers. comm.)
• Total remediation marketUS: $ 6-8 billion/yrWorld: $ 25-50 billion/yr
• ~200 field projects - funded mostly by EPA, DOD, DOE- some commercial/joint projects
• 9 purely phytorem. companies• 7 constructed wetland companies
• > 40 consulting/engin. companies that also do phytoremediation
Status of phytoremediation (cont.)
Uses of phytoremediation
• air• soils, sediments• groundwater• wastewater streams
- industrial - agricultural- municipal, sewage
Remediation of different media:
Uses of phytoremediation (cont.)
• inorganics:- metals (Pb, Cd, Zn, Cr, Hg)- metalloids (Se, As)- “nutrients” (K, P, N, S)- radionuclides (Cs, U)
Remediation of different pollutants:
• organics: - PCBs- PAHs- TCE- TNT- MTBE- pesticides- petroleum hydrocarbonsEtc.
Uses of phytoremediation (cont.)
• farming polluted soil
• irrigation with polluted groundwater
• letting trees tap into groundwater
• letting plants filter water streamsconstructed wetlands, hydroponics
Remediation using different systems:
Hydraulic barrierdifferent systems:
• Vegetative capdifferent systems:
• Constructed wetlands
different systems:
different systems: hydroponics with polluted wastewater
Roots of mustardExtend into effluentActing as filters for heavy metals
Uses of phytoremediation (cont.)
• 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
Properties of a good phytoremediator:
Remediation using different plants
Uses of phytoremediation (cont.)
• trees
Popular plants for phytoremediation
various organicsmetals
poplar
willow
gum treeyellow poplar
Uses of phytoremediation (cont.)
• For inorganics
Popular plants for phytoremediation
• grasses
(cont.):
Brassica junceaAlyssum
Thlaspi
Brassicaceae:
Uses of phytoremediation (cont.)
Popular plants for phytoremediation(cont.):
hemp
kenafbamboo
various grasses
red fescuebuffalo grass
for organics
for inorganics
Uses of phytoremediation (cont.)
Popular plants for phytoremediation
parrot feather
poplar, willow spartina
halophytes
salicornia
reed
aquatic plantscattail
for organics
for inorganics
Phytoremediation
Mechanical/chemical treatment• Soil washing• Excavation + reburial• Chemical cleanup of soil/water• Combustion
In situ
Ex situFossil fuels for energy
Solar energy
Phytoremediation vs. Mechanical/chemical treatment
• Cheaper
Advantages of phytoremediation
~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
Limitations of phytoremediation
Phytoremediation vs. Mechanical/chemical treatment (cont.)
• Can be slower
Limited by rate of biological processes
- Metabolic breakdown (organics): fairly fast- Filter action by plants: fast (days)
-Accumulation in plant tissue: slow e.g. metals: average 15 yrs to clean up site
(< 1yr)
Limitations of phytoremediation (cont.)
Phytoremediation vs. Mechanical/chemical treatment (cont.)
• Limited root depthTrees > prairie grasses > forbs, other grasses
Max depth ~5 m
Can be increased up to 20m with “deep planting”
Limitations of phytoremediation (cont.)
Phytoremediation vs. Mechanical/chemical treatment (cont.)
• Plant tolerance to pollutant/conditions
• Bioavailability of contaminant
- Bigger problem with metals than organics- Can be alleviated using amendments, or
treating hot spots by other method
- Bioavailability can be enhanced by amendments
So, when choose phytoremediation?
• Sufficient time available • Pollution shallow enough• Pollutant concentrations not phytotoxic
For very large quantities of mildly contaminated substrate: phytoremediation only cost-effective option
Note: Phyto may be used in conjunction with other remediation methods
• $$ limited
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)
phytostimulation
Phytoremediation processes
• Phytostimulation: plant roots stimulate degradation of pollutant by rhizosphere microbes
Organics e.g. PCBs, PAHs
bacteria, fungi
phytodegradation
Phytoremediation processes
• Phytodegradation: plants degrade pollutant, with/without uptake, translocation
Certain organicse.g. TCE, TNT, atrazine
Via enzymes, e.g. oxygenases nitroreductase
in tissues or in root exudate
accumulation
phytoextraction
Phytoremediation processes
• Phytoextraction: pollutant accumulated in harvestable plant tissues
mainly inorganics:metalsmetalloidsradionuclides
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, Hgsome volatile organics: TCE, MTBE
stabilization degradation
volatilization
accumulation
Phytoremediation applications may involve
multiple processes at once
Rhizofiltration
water
• Rhizofiltration: pollutant removed from water by plant roots in hydroponic system
for inorganics
Plant roots & shoots harvestable (may be used to mine metals)
or disposed after minimizing volume
metalsmetalloidsradionuclides
Rhizofiltration
• Hydroponics for metal remediation:75% of metals removed from mine drainage
Involves: • phytoextraction• phytostabilization
• Constructed wetland for Se remediation:
Involves: •phytoextraction• phytovolatilization• phytostabilization• (rhizofiltration)• (phytostimulation)
75% of Se removed from ag drainage water
• Natural attenuation: polluted site left alone but monitored
• Vegetative cap: polluted site revegetated, then left alone, monitored
with/without adding clean topsoil
Hydraulic barrier
H2O
Water flow redirectedPollutants intercepted
Phytoremediation project (1996-)(Phytokinetics inc.)
Oregon siteSoil polluted with PAHsPlanted with grass (Lolium perenne)
Results: bare soil: some PAH removalvegetated soil: increased PAH removal (~4x)
Process? Phytostimulation/phytodegradation
Phytoremediation project (1995-1998)(Phytotech inc.)
New Jersey siteSoil polluted with lead (Pb)Planted with Indian mustard (Brassica juncea)
Results (after 3 growing seasons): bare soil: 6% reduction in Pbvegetated soil: 29% reduction in Pb
Process? Phytoextraction
Phytoremediation project (1997)(COE)
Mississippi siteGroundwater polluted with TNTpumped through constructed wetland
Results:95% reduction in TNTendogenous plant enzymes found todegrade 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, 2005Phytoremediation (review)Ann Rev Plant Biology