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PHYTOREMEDIATION

Submitted by: Gurpreet Singh Roll no:601101006 M.Tech (EST)

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Phytoremediation

• Phytoremediation is a process that uses plants to remove, transfer, stabilize and destroy contaminants in soil ,water and sediment. Contaminants may be either organic or inorganic. It is also called vegetation- enhanced bioremediation

• Phytoremediation consists in mitigating pollutant in

contaminated soils , water ,or air, with plants able to contain degrade, or eliminate metals, pesticides, solvents, explosives crude oil and its derivatives and various other contaminants from the media that contain them.

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Phytoremediation Overview

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History of Phytoremediation

• Raskin coined the term in a 1991 proposal funded by U.S. EPA Superfund Program on metals accumulation

• Cunningham and Berti (1993) first used the term in the open literature

• Schnoor et al. (1995) first expanded the term in the open literature to include transformation of organics

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Phytohydraulics

Illustration of remediation of deeper wells in-situ

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Phytodegradation

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Phytodegradation of pesticides by a notorious pest plant

The potential of water hyacinth (Eichhornia crassipes) to remove a phosphorus pesticide ethion were investigated. The disappearance rate constants of ethion . . . implied that plant uptake and phytodegradation contributed 69% and that of microbial degradation took up 12% to the removal of the applied ethion. The accumulated ethion in live water hyacinth plant decreased by 55-91% in shoots and 74-81% in roots after the plant growing 1 week in ethion free culture solutions, suggesting that plant uptake and phytodegradation might be the dominant process for ethion removal by the plant. This plant might be utilized as an efficient, economical and ecological alternative to accelerate the removal and degradation of agro-industrial wastewater polluted with ethion.

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Phytodegradation of TCE, other chlorinated hydrocarbons by hybrid and/or transgenic poplar

A MASS BALANCE FIELD TRIAL OF CARBON TETRACHLORIDE PHYTOREMEDIATION USING POPLAR: PHYTODEGRADATION IS THE LIKELY

FATE Michael Dossett1, and Xiaoping Wang2, and Stuart E. Strand3

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Rhizodegradation

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Phytoextraction

Uptake of Metals (Nickel) by Phytoextraction

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Arsenic contamination: removed by phytoextraction

“The Chinese Ladder fern Pteris vittata, also known as the brake fern, is a highly efficient accumulator of arsenic. P. vittata grows rapidly and can absorb up to 2% of its weight in arsenic. . . When grown on soil with 100 ppm not only did it absorb more arsenic, but it grew 40% larger than normal.” Lena Q. Ma, 2001

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Phytostabilization

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Phytostabilization of mercury by willow roots

Yaodong Wang, 2004

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Rhizofiltration

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Rhizofiltration: sunflowers after Chernobyl disaster

Plants on rafts in pondwater: removed radionuclides ofstrontium, cesium, etc.

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Phytovolatalization

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Role of genetics

• Genes for phytoremediation may originate from a micro-organism or may be transferred from one plant to another variety better adapted to the environmental conditions at the cleanup site.

• Some natural, biodegradable compounds, such as exogenous polyamines, allow the plants to tolerate concentrations of pollutants 500 times higher than untreated plants, and to absorb more pollutants.

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Advantages of phytoremediation compared to classical remediation

• It is more economically viable using the same tools and supplies as agriculture

• It is less disruptive to the environment and does not involve waiting for new plant communities to recolonise the site

• Disposal sites are not needed• It is more likely to be accepted by the public as it is more

aesthetically pleasing then traditional methods• It avoids excavation and transport of polluted media thus reducing

the risk of spreading the contamination• It has the potential to treat sites polluted with more than one type

of pollutant

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Disadvantages of phytoremediation compared to classical remediation

• It is dependant on the growing conditions required by the plant (i.e climate, geology, altitude, temperature)

• Large scale operations require access to agricultural equipment and knowledge

• Success is dependant on the tolerance of the plant to the pollutant• Contaminants collected in senescing tissues may be released back

into the environment in autumn• Contaminants may be collected in woody tissues used as fuel• Time taken to remediate sites far exceeds that of other technologies• Contaminant solubility may be increased leading to greater

environmental damage and the possibility of leaching

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Risk Assessment

The use of phytoremediation in the field is subject to many environmental concerns, especially in the light of the recent public hysteria about the release of GM crops into the environment. Even if non GM strains of plants are used there are still many concerns:

• It is unknown what ecological effects hyper accumulator plants may have if ingested by animals

• Fallout from senescing tissues in autumn may also re-enter the food chain

• Do volatilized contaminants remain at 'safe' levels in the atmosphere

• Exposure of the ecosystem to contaminants is prolonged as phytoremediation is a relatively slow process

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Where has Phytoremediation Been Used?

Location Application Pollutant Medium plant(s)

Ogden, UTPhytoextraction & Rhizodegradation

Petroleum & Hydrocarbons

Soil & Groundwater

Alfalfa, poplar, juniper, fescue

Anderson, ST Phytostabilisation Heavy Metals Soil Hybrid poplar,

grasses

Ashtabula, OH Rhizofiltration Radionuclides Groundwater Sunflowers

Upton, NY Phytoextraction Radionuclides Soil Indian mustard,

cabbage

Milan, TN Phytodegradation

Expolsives waste Groundwater Duckweed,

parrotfeather

Amana, IARiparian corridor, phytodegradation

Nitrates Groundwater Hybrid poplar

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The important phytoremediation technologies applied are rhizofiltration, phytostabilization, phytovolatilization, and phytoextraction. The term phytoremediation ("phyto" meaning plant, and the Latin suffix "remedium" meaning to clean or restore) actually refers to a diverse collection of plant-based technologies that use either naturally occurring or genetically engineered plants for cleaning contaminated environments.

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Remediation of saline soils

Salicornia (pickleweed) accumulates salt in vacuole.A form of table salt can then be extracted from plant.

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Conclusion

• Although much remains to be studied, phytoremediation will clearly play some role in the stabilization and remediation of many contaminated sites. The main factor driving the implementation of phytoremediation projects are low costs with significant improvements in site aesthetics and the potential for ecosystem restoration.