Phytoremediation is the technical term used to
describe the treatment
of environmental problems through the use
Phytoremediation uses living plants for in situ
and ex situ remediation of contaminated soil,
sludges, sediments and ground water through
contaminant removal, degradation or
Phytoremediation can be used to remediate
various contaminants including metals,
pesticides, solvents, explosives, petroleum
hydrocarbons, polycyclic aromatic
hydrocarbons and landfill leachates.
Phytoremediation has been used for point
and nonpoint source hazardous waste.
Risk Reduction & Technology
Specially selected or engineered plants are used in the process.
Risk reduction can be through a process of removal,
degradation of, or containment of a contaminant or a
combination of any of these factors.
Green technology that uses plants systems for remediation and
Encompasses microbial degradation in rhizosphere as well as
uptake, accumulation and transformation in the plant.
How does it work?
Plants in conjunction with bacteria and fungi in the
store harmful chemicals.
Root system surface area to absorb substances and efficient
mechanisms to accumulate water, nutrients and minerals.
Selectively take up ions
Developed diversity and adaptivity to tolerate high levels of
metals and other pollutants.
Plants may break down or degrade organic
pollutants, or remove and stabilize metal
contaminants. This may be done through
one of or a combination of the methods.
The methods used to phytoremediate metal
contaminants are slightly different to those
used to remediate sites polluted with
Phytoremediation uses one basic concept:
the plant takes the pollutant through the
The pollutant can be stored in the plant
volatized by the plant (phytovolatization),
metabolized by the plant
Types Of Phytoremediation
1. Phytoextraction (Phytoaccumulation
4. Phytodegradation (Phytotransformation)
7. Hydraulic control of Pollutants
The process where plant roots uptake metal contaminants
from the soil and translocate them to their above soil
This is of particular importance on sites that have been
polluted with more than one type of metal contaminant.
Hyperaccumulator plant species are used on may sites due
to their tolerance of relatively extreme levels of pollution.
Once the plants have grown and absorbed the metal
pollutants they are harvested and disposed of safely.
This process is repeated several times to reduce
contamination to acceptable levels.
Metal compounds that have been successfully
phytoextracted include zinc, copper and nickel.
Rhizofiltration is the remediation of polluted soils.
The contaminants are either adsorbed onto the root
surface or are absorbed by the plant roots.
Plants used for rhizoliltration are not planted directly in
situ but are acclimated to the pollutant first.
Plants are hydroponically grown in clean water rather
than soil, until a large root system has developed.
Once a large root system is in place the water supply is
substituted for a polluted water supply to acclimatise the
Afer the plants become acclimatised they are planted in
the polluted area where the roots uptake the polluted
water and the contaminants along with it.
Phytostabilisation is the use of certain plants to
immobilise soil and water contaminants.
Contaminant are absorbed and accumulated by roots,
adsorbed onto the roots, or precipitated in
This reduces or even prevents the mobility of the
contaminants preventing migration into the groundwater
or air, and also reduces the bioavailibility of the
contaminant thus preventing spread through the food
This technique can also be used to re-establish a plant
community on sites that have been denuded due to the
high levels of metal contamination.
breakdown of organic contaminants by internal and
external metabolic processes driven by the plant.
Plants metabolic processes hydrolyse organic
compounds into smaller units that can be absorbed by the
Some contaminants can be absorbed by the plant and are
then broken down by plant enzymes.
These smaller pollutant molecules may then be used as
metabolites by the plant as it grows, thus becoming
incorporated into the plant tissues.
Plant enzymes have been identified that breakdown
ammunition wastes, chlorinated solvents such as TCE
(Trichloroethane), and others which degrade organic
Breakdown of organic contaminants in the soil by soil
dwelling microbes which is enhanced by the
Certain soil dwelling microbes digest organic pollutants
such as fuels and solvents, producing harmless products.
Plant root exudates such as sugars, alcohols, and organic
acids act as carbohydrate sources for the soil microflora
and enhance microbial growth and activity.
The plant roots also loosen the soil and transport water to
the rhizosphere thus additionaly enhancing microbial
Process where plants uptake contaminaints which are
water soluble and release them into the atmosphere as
they transpire the water.
The contaminant may become modified along the way,
as the water travels along the plant's vascular system
from the roots to the leaves, whereby the contaminants
evaporate or volatilize into the air surrounding the plant.
There are varying degrees of success with plants as
phytovolatilizers with one study showing poplar trees to
volatilize up to 90% of the TCE they absorb.
Phytoremediation is less expensive than the old "pump and
treat" method for the treatment of contaminated water.
Phytoremediation is also much less expensive than digging out
the contaminated site.
Up to 95% of TCE present in water could be removed by
simply planting trees and letting them grow.
Phytoremediation takes no maintenance once instituted.
Since phytoremediation uses plants, it is aesthetically
After plants are introduced, wildlife is able to flourish at the
once uninhabitable site.
Solar energy is used to drive the cleansing activity.
Phytoremediation is limited to sites with lower contaminant
Phytoremediation is restricted to sites with contamination as
deep as the roots of the plants being used.
The food chain could be adversely affected by the degradation
The air could be contaminated by the burning of leaves or
limbs of plants containing dangerous chemicals.
The use of phytoremediation in the field is subject to many
It is unknown what ecological effects hyperaccumulator
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
Exposure of the ecosystem to contaminants is prolonged as
phytoremediation is a relatively slow process
One of the primary roles of fungi in
the ecosystem is decomposition, which is performed
by the mycelium.
The mycelium secretes
extracellular enzymes and acids that break down
lignin and cellulose, the two main building blocks of
These are organic compounds composed of long
chains of carbon and hydrogen, structurally similar to
many organic pollutants.
The key to mycoremediation is determining the right
fungal species to target a specific pollutant.
Fungi have ligninase and cellulase enzymes
that break down woody materials. This allows
fungi to get the needed carbon and energy they
require for growth.
These enzymes are non-specific, meaning they
can act on substrates like environmental
Hyphae allow fungi to expand their surface
area, making it easier to contact the pollutant.
Extracellular enzymes can then go to work.
Organo pollutant degradation
white rot fungi, acts to break down pollutants by
adding an -OH group.
Fungi used in conjunction with the plant to
PCB volatility and xenobiotic extraction method
were factors affecting remediation success.
Wood and litter decaying fungi have been shown
to metabolize TNT.
Mycofiltration is a similar or same process,
using fungal mycelia to filter toxic waste
and microorganisms from water in soil.