BZ572 - Phytoremediation

Elizabeth Pilon-SmitsBiology Department

E413 ANAZO491-4991

epsmits@lamar.colostate.edu

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