phytoremediation kust
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Presented By Jehanzeb khan PhD 1st Semester Department of Botany KUSTjehan8botany@gmail.com
Course AdvisorDr Aziz UllahAssistant Professor Department of BotanyKUST
SYNTHETIC POLLUTANTS
PHYTOREMEDIATION
OVERVIEW Introduction of Phytoremediation1. Application2. Various phytoremediation processes3. Role of genetics4. Hyperaccumulators 5. Phytoscreening6. Advantages and limitations
PHYTOREMEDIATION
The use of plants which lessen the environmental problem without the need to dig up the contaminant material and dispose of it elsewhere.
phyto = plantremedium = restoring balance
Application Phytoremediation may be applied
wherever the soil or stagnant water environment has become polluted or is suffering ongoing constant pollution.
Examples where phytoremediation has been used successfully include the restoration of abandoned metal-mine workings, reducing the impact of contaminants in soils, water, or air.
How does Phytoremediation work? First process is Phytodegradation, which is when a plant
takes in TCE(Trichloroethylene) and degrades it into CO2 and chlorine before released into the atmosphere.
Another process is phytovolatilization which is when some chemicals are taken in through the xylem and converted into a gas through the stomata of the plant.
When plants go through these processes they leave chemicals in stem for easy collection.
Process
Various phytoremediation processes
A range of processes mediated by plants or algae are useful in treating environmental problems:
1. Phytoextraction2. Phytostabilization3. Phytotransformation4. Phytostimulation 5. Phytovolatilization 6. Rhizofiltration
Phytoextraction Plant roots uptake metal contaminants
from the soil and translocate them to their above soil tissues
Once the plants have grown and absorbed the metal pollutants they are harvested and disposed off safely
This process is repeated several times to reduce contamination to acceptable levels
Hyper accumulator plant species are used on many sites due to their tolerance of relatively extreme levels of pollution
Avena sp. , Brassica sp.Contaminants removed: Metal compounds that have been
successfully phytoextracted include zinc, copper, and nickel
Phytostabilisation
Vegetation holds contaminated soils in place Root system and low growing vegetation
prevent mechanical transportation of pollutants
from wind and erosion. Trees transpire large quantities of water
(more than 15 gal/day) so pumping action
prevents contaminants from migration into the
water table (leaching).
Phytotransformation chemical modification of environmental substances as a
result of plant metabolism resulting in their inactivation, degradation (phytodegradation), or immobilization (phytostabilization).
Trichloroethylene (TCE), a widespread ground
water contaminant, transformed to less toxic
metabolites by using hybrid poplar tree. Air Force facility in Texas using cottonwoods to
treat a large ground water cloud of TCE. EPA research lab using parrot feather (a
common aquatic weed) for TNT treatment.
Phytostimulation
Phytostimulation is the process where root released compounds enhance microbial activity in the rhizosphere.
Rhizosphere = soil + root + microbes Symbiotic relation
Enhanced rhizosphere biodegradation Phytostimulation Plant assisted bioremediation
Continued…..
Sugars, alcohols, and organic acids act as carbohydrate sources for the soil microflora and enhance microbial growth and activity.
Act as chemotactic signals for certain microbes. The roots also loosen the soil and transport water to the
rhizosphere thus enhancing microbial activity Digest organic pollutants such as fuels and solvents,
producing harmless products
Phytovolatilization Plants uptake contaminants 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 into the air surrounding the plant
Poplar trees volatilize up to 90% of the TCE they absorb
Rhizofiltration
filtering water through a mass of roots to remove toxic substances or excess
The contaminants are either adsorbed onto the root surface or are absorbed by the plant roots
1995, Sunflowers were used in a pond near Chernobyl
Plants used for
Chernobyl -sunflowers were grown in radioactively contaminated pools
Role of genetics Genetic engineering is a powerful method for
enhancing natural Phytoremediation
capabilities, or for introducing new capabilities
into plants. Example, genes encoding a
nitroreductase from a bacterium were inserted
into tobacco and showed faster removal of TNT
and enhanced resistance to the toxic effects of
TNT
Hyperaccumulators
A plant that absorbs toxins, such as heavy metals, to a greater concentration than that in the soil in which it is growing
A number of interactions may be affected by metal hyperaccumulation:
mutualism (including mycorrhizae)
Phytoscreening
Plants are able to translocate and accumulate particular types of contaminants:
plants can be used as biosensors of subsurface contamination
Phytoscreening may lead to more optimized site investigations and reduce contaminated site cleanup costs
Advantages
Cost effective when compared to other more
conventional methods. “natural” method, more aesthetically pleasing. minimal land disturbance. reduces potential for transport of
contaminants by wind, reduces soil erosion hyper-accumulators of contaminants mean a
much smaller volume of toxic waste. multiple contaminants can be removed with the
same plant.
Disadvantages Slow rate and difficult to achieve acceptable
levels of decontamination. Possibility of contaminated plants entering
the food chain. Possible spread of contaminant through
falling leaves. Trees and plants require care. Contaminant might kill the tree. Degradation product could be worse than
original contaminant. Only surface soil (root zone) can be treated
Cleanup takes several years
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.
Questions & Answers
Thank you
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