BZ572 - Phytoremediation

transcript

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

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.

• 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

• 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

• trees

Popular plants for phytoremediation

various organicsmetals

poplar

willow

gum treeyellow poplar

• For inorganics

• grasses

(cont.):

Brassica junceaAlyssum

Thlaspi

Brassicaceae:

Popular plants for phytoremediation(cont.):

kenafbamboo

various grasses

red fescuebuffalo grass

for organics

for inorganics

parrot feather

poplar, willow spartina

halophytes

salicornia

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.)

• 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.)

• 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

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

• Phytostimulation: plant roots stimulate degradation of pollutant by rhizosphere microbes

Organics e.g. PCBs, PAHs

bacteria, fungi

phytodegradation

• 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

• 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)

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

• 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

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

BZ572 - Phytoremediation

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