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PHYTOREMEDIATION
Introduction
Phytoremediation is the use of living green plants forin situ risk reduction andor removal of contaminantsfrom contaminated soil water sediments and air
OVERVIEW
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
Rhizofiltration It is concerned with the remediation of contaminated groundwater
The contaminants are either adsorbed onto the root surface or are
absorbed by the plant roots
Plants used for rhizofiltration are acclimated to the pollutant
1
bull Plants are hydroponically grown in clean water rather than soil until a large root system has developed
2
bull Water supply is substituted for a polluted water supply to acclimatize the plant
3
bull They are planted in the polluted area where the roots uptake the polluted water and the contaminants along with it
4
bull As the roots become saturated they are harvested and disposed of safely
Chernobyl - sunflowers
were grown in radioactively
contaminated pools
Phytostabilisation To immobilize soil and water contaminants from
migration
Mechanisms
Phytochemical complexation in the root zone ndash
precipitation
Transport protein inhibition on the root membrane (B)
Vacuolar storage in the root cells (C)
Pb Cu Zn ndash Agrostis tenuis
Phytodegradation
It is the degradation or breakdownof organic contaminants by internaland external metabolic processesdriven by the plant
Mechanisms
(A) Plant enzymatic activity
oxygenases- hydrocarbons
nitroreductases- explosives
(B) Photosynthetic oxidation
Used in breakdown of ammunitionwastes chlorinated solvents suchas TCE (Trichloroethane)degradation of organic herbicides
Contd
External Process Internal Process
Rhizodegradation It is the breakdown of organic contaminants in the soil by soil dwelling
microbes which is enhanced by the rhizospherelsquos presence
Rhizosphere = soil + root + microbes
Symbiotic relation
Also called
Enhanced rhizosphere biodegradation
Phytostimulation
Plant assisted bioremediation
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 plants vascular system from the roots
to the leaves whereby the
contaminants evaporate
or volatilize into the air surrounding the
plant
Poplar trees volatilize up to 90 of the
TCE they absorb
Selenium and Mercury - Arabidopsis
thaliana L and tobacco
Phytohydraulics
The use of plants to control the migration of
subsurface water through the rapid uptake of
large volumes of water by the plants
Plants - acting as natural hydraulic pumps
A dense root network established near the
water table can transpire up to 300 gallons of
water per day
This fact has been utilized to decrease the
migration of contaminants from surface water
into the groundwater (below the water table)
and drinking water supplies
LEVEL OF POLLUTANT
Sampling
Field sampling quality assurance
Avoiding contamination of
samples
Equipment cleaning
Sample labels
Recent trend
Immunoassay testing and other
technology may be used to provide
on site screening
This work shall only be carried out
by properly trained personnel
Parameter Media Acceptable
Test
Methods
Petroleum
Hydrocarbo
ns
Water amp
soil
Gas
chromatogra
phy
Volatiles
(including
BTEX)
Water amp
soil
Infra-red
based
methods
Semi-
volatiles
(including
PAH)
water EPA
Standards
Analytical methods
Measurement of aquatic biodegradation rates by determining
heterotrophic uptake of radiolabeled pollutants
F K Pfaender and G W Bartholomew
bull The heterotrophic uptake technique was modified to provide a rapid
and simple technique for estimating the rates of biodegradation of
organic pollutants under environmental conditions
bull The methodology is based on an evaluation of uptake into cells and
subsequent respiration of radiolabeled organic substrates in short-
term experiments
bull The resulting data can be used to calculate either turnover times or
if multiple concentrations of substrate are used kinetic parameters
bull The procedure was applied to assess the biodegradation rates of m-
cresol chlorobenzene nitrilotriacetic acid and 124-
trichlorobenzene in fresh brackish and marine water samples from
the coastal areas of North Carolina
bull Saturation kinetics for uptake were obtained with each of the
compounds tested
bull Rates of metabolism were shown to be dependent on sample
location and time of year
Phytoremediation amp Biotechnology
Maximizing potential for phytoremediation
GM approaches can be used to over express the enzymes involved in
the existing plant metabolic pathways or to introduce new pathways
into plants
Richard Meagher and colleagues introduced a new pathway
into Arabidopsis to detoxify methylmercury a common form of
environmental pollutant to elemental mercury which can be volatilised
by the plant
Mer B
Organomercurial Lyase
Methyl Mercury Ionic Mercury
MerA
Mercuric Reductase
Ionic Mercury Elemental Form
The genes originated in gram-negative bacteria
Arabidopsis plants were transformed with either MerA or MerB coupled with aconstitutive promoter
The MerA plants were more tolerant to ionic mercury volatilised elementalmercury and were unaffected in their tolerance of methylmercury
The MerB Plants were significantly more tolerant to methylmercury and otherorganomercurials and could also convert methylmercury to ionic mercury whichis approximately 100 times less toxic to plants
MerA MerB double transgenics were produced in an F2 generation These plantsnot only showed a greater resistance to organic mercury when compared to theMerA MerB and wildtype plants but also capable of volatilizing mercury whensupplied with methylmercury
The same MerAMerB inserts have been used in other plant species includingtobacco(Nicotiana tabacum) yellow poplar(Liriodendron tulipifera)
Wetland species (bulrush and cat-tail) and water tolerant trees (willow and poplar)have also been targetted for transformation
Risk Assessment
Potential for the gene to recombine with other genes possibly
leading to the hyperaccumulation of non-contaminant
compounds
Reportermarker genes may also escape into the environment
The GM plants may revert to a wild type genotype
Advantages of phytoremediation
It is more economically viable using the same tools and
supplies as agriculture
It is less disruptive to the environment
Disposal sites are not needed
Aesthetically pleasing than traditional methods
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
Disadvantages of phytoremediation
Growing conditions required by the plant (ie Climate
geology altitude temperature)
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
Introduction
Phytoremediation is the use of living green plants forin situ risk reduction andor removal of contaminantsfrom contaminated soil water sediments and air
OVERVIEW
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
Rhizofiltration It is concerned with the remediation of contaminated groundwater
The contaminants are either adsorbed onto the root surface or are
absorbed by the plant roots
Plants used for rhizofiltration are acclimated to the pollutant
1
bull Plants are hydroponically grown in clean water rather than soil until a large root system has developed
2
bull Water supply is substituted for a polluted water supply to acclimatize the plant
3
bull They are planted in the polluted area where the roots uptake the polluted water and the contaminants along with it
4
bull As the roots become saturated they are harvested and disposed of safely
Chernobyl - sunflowers
were grown in radioactively
contaminated pools
Phytostabilisation To immobilize soil and water contaminants from
migration
Mechanisms
Phytochemical complexation in the root zone ndash
precipitation
Transport protein inhibition on the root membrane (B)
Vacuolar storage in the root cells (C)
Pb Cu Zn ndash Agrostis tenuis
Phytodegradation
It is the degradation or breakdownof organic contaminants by internaland external metabolic processesdriven by the plant
Mechanisms
(A) Plant enzymatic activity
oxygenases- hydrocarbons
nitroreductases- explosives
(B) Photosynthetic oxidation
Used in breakdown of ammunitionwastes chlorinated solvents suchas TCE (Trichloroethane)degradation of organic herbicides
Contd
External Process Internal Process
Rhizodegradation It is the breakdown of organic contaminants in the soil by soil dwelling
microbes which is enhanced by the rhizospherelsquos presence
Rhizosphere = soil + root + microbes
Symbiotic relation
Also called
Enhanced rhizosphere biodegradation
Phytostimulation
Plant assisted bioremediation
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 plants vascular system from the roots
to the leaves whereby the
contaminants evaporate
or volatilize into the air surrounding the
plant
Poplar trees volatilize up to 90 of the
TCE they absorb
Selenium and Mercury - Arabidopsis
thaliana L and tobacco
Phytohydraulics
The use of plants to control the migration of
subsurface water through the rapid uptake of
large volumes of water by the plants
Plants - acting as natural hydraulic pumps
A dense root network established near the
water table can transpire up to 300 gallons of
water per day
This fact has been utilized to decrease the
migration of contaminants from surface water
into the groundwater (below the water table)
and drinking water supplies
LEVEL OF POLLUTANT
Sampling
Field sampling quality assurance
Avoiding contamination of
samples
Equipment cleaning
Sample labels
Recent trend
Immunoassay testing and other
technology may be used to provide
on site screening
This work shall only be carried out
by properly trained personnel
Parameter Media Acceptable
Test
Methods
Petroleum
Hydrocarbo
ns
Water amp
soil
Gas
chromatogra
phy
Volatiles
(including
BTEX)
Water amp
soil
Infra-red
based
methods
Semi-
volatiles
(including
PAH)
water EPA
Standards
Analytical methods
Measurement of aquatic biodegradation rates by determining
heterotrophic uptake of radiolabeled pollutants
F K Pfaender and G W Bartholomew
bull The heterotrophic uptake technique was modified to provide a rapid
and simple technique for estimating the rates of biodegradation of
organic pollutants under environmental conditions
bull The methodology is based on an evaluation of uptake into cells and
subsequent respiration of radiolabeled organic substrates in short-
term experiments
bull The resulting data can be used to calculate either turnover times or
if multiple concentrations of substrate are used kinetic parameters
bull The procedure was applied to assess the biodegradation rates of m-
cresol chlorobenzene nitrilotriacetic acid and 124-
trichlorobenzene in fresh brackish and marine water samples from
the coastal areas of North Carolina
bull Saturation kinetics for uptake were obtained with each of the
compounds tested
bull Rates of metabolism were shown to be dependent on sample
location and time of year
Phytoremediation amp Biotechnology
Maximizing potential for phytoremediation
GM approaches can be used to over express the enzymes involved in
the existing plant metabolic pathways or to introduce new pathways
into plants
Richard Meagher and colleagues introduced a new pathway
into Arabidopsis to detoxify methylmercury a common form of
environmental pollutant to elemental mercury which can be volatilised
by the plant
Mer B
Organomercurial Lyase
Methyl Mercury Ionic Mercury
MerA
Mercuric Reductase
Ionic Mercury Elemental Form
The genes originated in gram-negative bacteria
Arabidopsis plants were transformed with either MerA or MerB coupled with aconstitutive promoter
The MerA plants were more tolerant to ionic mercury volatilised elementalmercury and were unaffected in their tolerance of methylmercury
The MerB Plants were significantly more tolerant to methylmercury and otherorganomercurials and could also convert methylmercury to ionic mercury whichis approximately 100 times less toxic to plants
MerA MerB double transgenics were produced in an F2 generation These plantsnot only showed a greater resistance to organic mercury when compared to theMerA MerB and wildtype plants but also capable of volatilizing mercury whensupplied with methylmercury
The same MerAMerB inserts have been used in other plant species includingtobacco(Nicotiana tabacum) yellow poplar(Liriodendron tulipifera)
Wetland species (bulrush and cat-tail) and water tolerant trees (willow and poplar)have also been targetted for transformation
Risk Assessment
Potential for the gene to recombine with other genes possibly
leading to the hyperaccumulation of non-contaminant
compounds
Reportermarker genes may also escape into the environment
The GM plants may revert to a wild type genotype
Advantages of phytoremediation
It is more economically viable using the same tools and
supplies as agriculture
It is less disruptive to the environment
Disposal sites are not needed
Aesthetically pleasing than traditional methods
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
Disadvantages of phytoremediation
Growing conditions required by the plant (ie Climate
geology altitude temperature)
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
OVERVIEW
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
Rhizofiltration It is concerned with the remediation of contaminated groundwater
The contaminants are either adsorbed onto the root surface or are
absorbed by the plant roots
Plants used for rhizofiltration are acclimated to the pollutant
1
bull Plants are hydroponically grown in clean water rather than soil until a large root system has developed
2
bull Water supply is substituted for a polluted water supply to acclimatize the plant
3
bull They are planted in the polluted area where the roots uptake the polluted water and the contaminants along with it
4
bull As the roots become saturated they are harvested and disposed of safely
Chernobyl - sunflowers
were grown in radioactively
contaminated pools
Phytostabilisation To immobilize soil and water contaminants from
migration
Mechanisms
Phytochemical complexation in the root zone ndash
precipitation
Transport protein inhibition on the root membrane (B)
Vacuolar storage in the root cells (C)
Pb Cu Zn ndash Agrostis tenuis
Phytodegradation
It is the degradation or breakdownof organic contaminants by internaland external metabolic processesdriven by the plant
Mechanisms
(A) Plant enzymatic activity
oxygenases- hydrocarbons
nitroreductases- explosives
(B) Photosynthetic oxidation
Used in breakdown of ammunitionwastes chlorinated solvents suchas TCE (Trichloroethane)degradation of organic herbicides
Contd
External Process Internal Process
Rhizodegradation It is the breakdown of organic contaminants in the soil by soil dwelling
microbes which is enhanced by the rhizospherelsquos presence
Rhizosphere = soil + root + microbes
Symbiotic relation
Also called
Enhanced rhizosphere biodegradation
Phytostimulation
Plant assisted bioremediation
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 plants vascular system from the roots
to the leaves whereby the
contaminants evaporate
or volatilize into the air surrounding the
plant
Poplar trees volatilize up to 90 of the
TCE they absorb
Selenium and Mercury - Arabidopsis
thaliana L and tobacco
Phytohydraulics
The use of plants to control the migration of
subsurface water through the rapid uptake of
large volumes of water by the plants
Plants - acting as natural hydraulic pumps
A dense root network established near the
water table can transpire up to 300 gallons of
water per day
This fact has been utilized to decrease the
migration of contaminants from surface water
into the groundwater (below the water table)
and drinking water supplies
LEVEL OF POLLUTANT
Sampling
Field sampling quality assurance
Avoiding contamination of
samples
Equipment cleaning
Sample labels
Recent trend
Immunoassay testing and other
technology may be used to provide
on site screening
This work shall only be carried out
by properly trained personnel
Parameter Media Acceptable
Test
Methods
Petroleum
Hydrocarbo
ns
Water amp
soil
Gas
chromatogra
phy
Volatiles
(including
BTEX)
Water amp
soil
Infra-red
based
methods
Semi-
volatiles
(including
PAH)
water EPA
Standards
Analytical methods
Measurement of aquatic biodegradation rates by determining
heterotrophic uptake of radiolabeled pollutants
F K Pfaender and G W Bartholomew
bull The heterotrophic uptake technique was modified to provide a rapid
and simple technique for estimating the rates of biodegradation of
organic pollutants under environmental conditions
bull The methodology is based on an evaluation of uptake into cells and
subsequent respiration of radiolabeled organic substrates in short-
term experiments
bull The resulting data can be used to calculate either turnover times or
if multiple concentrations of substrate are used kinetic parameters
bull The procedure was applied to assess the biodegradation rates of m-
cresol chlorobenzene nitrilotriacetic acid and 124-
trichlorobenzene in fresh brackish and marine water samples from
the coastal areas of North Carolina
bull Saturation kinetics for uptake were obtained with each of the
compounds tested
bull Rates of metabolism were shown to be dependent on sample
location and time of year
Phytoremediation amp Biotechnology
Maximizing potential for phytoremediation
GM approaches can be used to over express the enzymes involved in
the existing plant metabolic pathways or to introduce new pathways
into plants
Richard Meagher and colleagues introduced a new pathway
into Arabidopsis to detoxify methylmercury a common form of
environmental pollutant to elemental mercury which can be volatilised
by the plant
Mer B
Organomercurial Lyase
Methyl Mercury Ionic Mercury
MerA
Mercuric Reductase
Ionic Mercury Elemental Form
The genes originated in gram-negative bacteria
Arabidopsis plants were transformed with either MerA or MerB coupled with aconstitutive promoter
The MerA plants were more tolerant to ionic mercury volatilised elementalmercury and were unaffected in their tolerance of methylmercury
The MerB Plants were significantly more tolerant to methylmercury and otherorganomercurials and could also convert methylmercury to ionic mercury whichis approximately 100 times less toxic to plants
MerA MerB double transgenics were produced in an F2 generation These plantsnot only showed a greater resistance to organic mercury when compared to theMerA MerB and wildtype plants but also capable of volatilizing mercury whensupplied with methylmercury
The same MerAMerB inserts have been used in other plant species includingtobacco(Nicotiana tabacum) yellow poplar(Liriodendron tulipifera)
Wetland species (bulrush and cat-tail) and water tolerant trees (willow and poplar)have also been targetted for transformation
Risk Assessment
Potential for the gene to recombine with other genes possibly
leading to the hyperaccumulation of non-contaminant
compounds
Reportermarker genes may also escape into the environment
The GM plants may revert to a wild type genotype
Advantages of phytoremediation
It is more economically viable using the same tools and
supplies as agriculture
It is less disruptive to the environment
Disposal sites are not needed
Aesthetically pleasing than traditional methods
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
Disadvantages of phytoremediation
Growing conditions required by the plant (ie Climate
geology altitude temperature)
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
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
Rhizofiltration It is concerned with the remediation of contaminated groundwater
The contaminants are either adsorbed onto the root surface or are
absorbed by the plant roots
Plants used for rhizofiltration are acclimated to the pollutant
1
bull Plants are hydroponically grown in clean water rather than soil until a large root system has developed
2
bull Water supply is substituted for a polluted water supply to acclimatize the plant
3
bull They are planted in the polluted area where the roots uptake the polluted water and the contaminants along with it
4
bull As the roots become saturated they are harvested and disposed of safely
Chernobyl - sunflowers
were grown in radioactively
contaminated pools
Phytostabilisation To immobilize soil and water contaminants from
migration
Mechanisms
Phytochemical complexation in the root zone ndash
precipitation
Transport protein inhibition on the root membrane (B)
Vacuolar storage in the root cells (C)
Pb Cu Zn ndash Agrostis tenuis
Phytodegradation
It is the degradation or breakdownof organic contaminants by internaland external metabolic processesdriven by the plant
Mechanisms
(A) Plant enzymatic activity
oxygenases- hydrocarbons
nitroreductases- explosives
(B) Photosynthetic oxidation
Used in breakdown of ammunitionwastes chlorinated solvents suchas TCE (Trichloroethane)degradation of organic herbicides
Contd
External Process Internal Process
Rhizodegradation It is the breakdown of organic contaminants in the soil by soil dwelling
microbes which is enhanced by the rhizospherelsquos presence
Rhizosphere = soil + root + microbes
Symbiotic relation
Also called
Enhanced rhizosphere biodegradation
Phytostimulation
Plant assisted bioremediation
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 plants vascular system from the roots
to the leaves whereby the
contaminants evaporate
or volatilize into the air surrounding the
plant
Poplar trees volatilize up to 90 of the
TCE they absorb
Selenium and Mercury - Arabidopsis
thaliana L and tobacco
Phytohydraulics
The use of plants to control the migration of
subsurface water through the rapid uptake of
large volumes of water by the plants
Plants - acting as natural hydraulic pumps
A dense root network established near the
water table can transpire up to 300 gallons of
water per day
This fact has been utilized to decrease the
migration of contaminants from surface water
into the groundwater (below the water table)
and drinking water supplies
LEVEL OF POLLUTANT
Sampling
Field sampling quality assurance
Avoiding contamination of
samples
Equipment cleaning
Sample labels
Recent trend
Immunoassay testing and other
technology may be used to provide
on site screening
This work shall only be carried out
by properly trained personnel
Parameter Media Acceptable
Test
Methods
Petroleum
Hydrocarbo
ns
Water amp
soil
Gas
chromatogra
phy
Volatiles
(including
BTEX)
Water amp
soil
Infra-red
based
methods
Semi-
volatiles
(including
PAH)
water EPA
Standards
Analytical methods
Measurement of aquatic biodegradation rates by determining
heterotrophic uptake of radiolabeled pollutants
F K Pfaender and G W Bartholomew
bull The heterotrophic uptake technique was modified to provide a rapid
and simple technique for estimating the rates of biodegradation of
organic pollutants under environmental conditions
bull The methodology is based on an evaluation of uptake into cells and
subsequent respiration of radiolabeled organic substrates in short-
term experiments
bull The resulting data can be used to calculate either turnover times or
if multiple concentrations of substrate are used kinetic parameters
bull The procedure was applied to assess the biodegradation rates of m-
cresol chlorobenzene nitrilotriacetic acid and 124-
trichlorobenzene in fresh brackish and marine water samples from
the coastal areas of North Carolina
bull Saturation kinetics for uptake were obtained with each of the
compounds tested
bull Rates of metabolism were shown to be dependent on sample
location and time of year
Phytoremediation amp Biotechnology
Maximizing potential for phytoremediation
GM approaches can be used to over express the enzymes involved in
the existing plant metabolic pathways or to introduce new pathways
into plants
Richard Meagher and colleagues introduced a new pathway
into Arabidopsis to detoxify methylmercury a common form of
environmental pollutant to elemental mercury which can be volatilised
by the plant
Mer B
Organomercurial Lyase
Methyl Mercury Ionic Mercury
MerA
Mercuric Reductase
Ionic Mercury Elemental Form
The genes originated in gram-negative bacteria
Arabidopsis plants were transformed with either MerA or MerB coupled with aconstitutive promoter
The MerA plants were more tolerant to ionic mercury volatilised elementalmercury and were unaffected in their tolerance of methylmercury
The MerB Plants were significantly more tolerant to methylmercury and otherorganomercurials and could also convert methylmercury to ionic mercury whichis approximately 100 times less toxic to plants
MerA MerB double transgenics were produced in an F2 generation These plantsnot only showed a greater resistance to organic mercury when compared to theMerA MerB and wildtype plants but also capable of volatilizing mercury whensupplied with methylmercury
The same MerAMerB inserts have been used in other plant species includingtobacco(Nicotiana tabacum) yellow poplar(Liriodendron tulipifera)
Wetland species (bulrush and cat-tail) and water tolerant trees (willow and poplar)have also been targetted for transformation
Risk Assessment
Potential for the gene to recombine with other genes possibly
leading to the hyperaccumulation of non-contaminant
compounds
Reportermarker genes may also escape into the environment
The GM plants may revert to a wild type genotype
Advantages of phytoremediation
It is more economically viable using the same tools and
supplies as agriculture
It is less disruptive to the environment
Disposal sites are not needed
Aesthetically pleasing than traditional methods
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
Disadvantages of phytoremediation
Growing conditions required by the plant (ie Climate
geology altitude temperature)
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
Rhizofiltration It is concerned with the remediation of contaminated groundwater
The contaminants are either adsorbed onto the root surface or are
absorbed by the plant roots
Plants used for rhizofiltration are acclimated to the pollutant
1
bull Plants are hydroponically grown in clean water rather than soil until a large root system has developed
2
bull Water supply is substituted for a polluted water supply to acclimatize the plant
3
bull They are planted in the polluted area where the roots uptake the polluted water and the contaminants along with it
4
bull As the roots become saturated they are harvested and disposed of safely
Chernobyl - sunflowers
were grown in radioactively
contaminated pools
Phytostabilisation To immobilize soil and water contaminants from
migration
Mechanisms
Phytochemical complexation in the root zone ndash
precipitation
Transport protein inhibition on the root membrane (B)
Vacuolar storage in the root cells (C)
Pb Cu Zn ndash Agrostis tenuis
Phytodegradation
It is the degradation or breakdownof organic contaminants by internaland external metabolic processesdriven by the plant
Mechanisms
(A) Plant enzymatic activity
oxygenases- hydrocarbons
nitroreductases- explosives
(B) Photosynthetic oxidation
Used in breakdown of ammunitionwastes chlorinated solvents suchas TCE (Trichloroethane)degradation of organic herbicides
Contd
External Process Internal Process
Rhizodegradation It is the breakdown of organic contaminants in the soil by soil dwelling
microbes which is enhanced by the rhizospherelsquos presence
Rhizosphere = soil + root + microbes
Symbiotic relation
Also called
Enhanced rhizosphere biodegradation
Phytostimulation
Plant assisted bioremediation
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 plants vascular system from the roots
to the leaves whereby the
contaminants evaporate
or volatilize into the air surrounding the
plant
Poplar trees volatilize up to 90 of the
TCE they absorb
Selenium and Mercury - Arabidopsis
thaliana L and tobacco
Phytohydraulics
The use of plants to control the migration of
subsurface water through the rapid uptake of
large volumes of water by the plants
Plants - acting as natural hydraulic pumps
A dense root network established near the
water table can transpire up to 300 gallons of
water per day
This fact has been utilized to decrease the
migration of contaminants from surface water
into the groundwater (below the water table)
and drinking water supplies
LEVEL OF POLLUTANT
Sampling
Field sampling quality assurance
Avoiding contamination of
samples
Equipment cleaning
Sample labels
Recent trend
Immunoassay testing and other
technology may be used to provide
on site screening
This work shall only be carried out
by properly trained personnel
Parameter Media Acceptable
Test
Methods
Petroleum
Hydrocarbo
ns
Water amp
soil
Gas
chromatogra
phy
Volatiles
(including
BTEX)
Water amp
soil
Infra-red
based
methods
Semi-
volatiles
(including
PAH)
water EPA
Standards
Analytical methods
Measurement of aquatic biodegradation rates by determining
heterotrophic uptake of radiolabeled pollutants
F K Pfaender and G W Bartholomew
bull The heterotrophic uptake technique was modified to provide a rapid
and simple technique for estimating the rates of biodegradation of
organic pollutants under environmental conditions
bull The methodology is based on an evaluation of uptake into cells and
subsequent respiration of radiolabeled organic substrates in short-
term experiments
bull The resulting data can be used to calculate either turnover times or
if multiple concentrations of substrate are used kinetic parameters
bull The procedure was applied to assess the biodegradation rates of m-
cresol chlorobenzene nitrilotriacetic acid and 124-
trichlorobenzene in fresh brackish and marine water samples from
the coastal areas of North Carolina
bull Saturation kinetics for uptake were obtained with each of the
compounds tested
bull Rates of metabolism were shown to be dependent on sample
location and time of year
Phytoremediation amp Biotechnology
Maximizing potential for phytoremediation
GM approaches can be used to over express the enzymes involved in
the existing plant metabolic pathways or to introduce new pathways
into plants
Richard Meagher and colleagues introduced a new pathway
into Arabidopsis to detoxify methylmercury a common form of
environmental pollutant to elemental mercury which can be volatilised
by the plant
Mer B
Organomercurial Lyase
Methyl Mercury Ionic Mercury
MerA
Mercuric Reductase
Ionic Mercury Elemental Form
The genes originated in gram-negative bacteria
Arabidopsis plants were transformed with either MerA or MerB coupled with aconstitutive promoter
The MerA plants were more tolerant to ionic mercury volatilised elementalmercury and were unaffected in their tolerance of methylmercury
The MerB Plants were significantly more tolerant to methylmercury and otherorganomercurials and could also convert methylmercury to ionic mercury whichis approximately 100 times less toxic to plants
MerA MerB double transgenics were produced in an F2 generation These plantsnot only showed a greater resistance to organic mercury when compared to theMerA MerB and wildtype plants but also capable of volatilizing mercury whensupplied with methylmercury
The same MerAMerB inserts have been used in other plant species includingtobacco(Nicotiana tabacum) yellow poplar(Liriodendron tulipifera)
Wetland species (bulrush and cat-tail) and water tolerant trees (willow and poplar)have also been targetted for transformation
Risk Assessment
Potential for the gene to recombine with other genes possibly
leading to the hyperaccumulation of non-contaminant
compounds
Reportermarker genes may also escape into the environment
The GM plants may revert to a wild type genotype
Advantages of phytoremediation
It is more economically viable using the same tools and
supplies as agriculture
It is less disruptive to the environment
Disposal sites are not needed
Aesthetically pleasing than traditional methods
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
Disadvantages of phytoremediation
Growing conditions required by the plant (ie Climate
geology altitude temperature)
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
Phytostabilisation To immobilize soil and water contaminants from
migration
Mechanisms
Phytochemical complexation in the root zone ndash
precipitation
Transport protein inhibition on the root membrane (B)
Vacuolar storage in the root cells (C)
Pb Cu Zn ndash Agrostis tenuis
Phytodegradation
It is the degradation or breakdownof organic contaminants by internaland external metabolic processesdriven by the plant
Mechanisms
(A) Plant enzymatic activity
oxygenases- hydrocarbons
nitroreductases- explosives
(B) Photosynthetic oxidation
Used in breakdown of ammunitionwastes chlorinated solvents suchas TCE (Trichloroethane)degradation of organic herbicides
Contd
External Process Internal Process
Rhizodegradation It is the breakdown of organic contaminants in the soil by soil dwelling
microbes which is enhanced by the rhizospherelsquos presence
Rhizosphere = soil + root + microbes
Symbiotic relation
Also called
Enhanced rhizosphere biodegradation
Phytostimulation
Plant assisted bioremediation
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 plants vascular system from the roots
to the leaves whereby the
contaminants evaporate
or volatilize into the air surrounding the
plant
Poplar trees volatilize up to 90 of the
TCE they absorb
Selenium and Mercury - Arabidopsis
thaliana L and tobacco
Phytohydraulics
The use of plants to control the migration of
subsurface water through the rapid uptake of
large volumes of water by the plants
Plants - acting as natural hydraulic pumps
A dense root network established near the
water table can transpire up to 300 gallons of
water per day
This fact has been utilized to decrease the
migration of contaminants from surface water
into the groundwater (below the water table)
and drinking water supplies
LEVEL OF POLLUTANT
Sampling
Field sampling quality assurance
Avoiding contamination of
samples
Equipment cleaning
Sample labels
Recent trend
Immunoassay testing and other
technology may be used to provide
on site screening
This work shall only be carried out
by properly trained personnel
Parameter Media Acceptable
Test
Methods
Petroleum
Hydrocarbo
ns
Water amp
soil
Gas
chromatogra
phy
Volatiles
(including
BTEX)
Water amp
soil
Infra-red
based
methods
Semi-
volatiles
(including
PAH)
water EPA
Standards
Analytical methods
Measurement of aquatic biodegradation rates by determining
heterotrophic uptake of radiolabeled pollutants
F K Pfaender and G W Bartholomew
bull The heterotrophic uptake technique was modified to provide a rapid
and simple technique for estimating the rates of biodegradation of
organic pollutants under environmental conditions
bull The methodology is based on an evaluation of uptake into cells and
subsequent respiration of radiolabeled organic substrates in short-
term experiments
bull The resulting data can be used to calculate either turnover times or
if multiple concentrations of substrate are used kinetic parameters
bull The procedure was applied to assess the biodegradation rates of m-
cresol chlorobenzene nitrilotriacetic acid and 124-
trichlorobenzene in fresh brackish and marine water samples from
the coastal areas of North Carolina
bull Saturation kinetics for uptake were obtained with each of the
compounds tested
bull Rates of metabolism were shown to be dependent on sample
location and time of year
Phytoremediation amp Biotechnology
Maximizing potential for phytoremediation
GM approaches can be used to over express the enzymes involved in
the existing plant metabolic pathways or to introduce new pathways
into plants
Richard Meagher and colleagues introduced a new pathway
into Arabidopsis to detoxify methylmercury a common form of
environmental pollutant to elemental mercury which can be volatilised
by the plant
Mer B
Organomercurial Lyase
Methyl Mercury Ionic Mercury
MerA
Mercuric Reductase
Ionic Mercury Elemental Form
The genes originated in gram-negative bacteria
Arabidopsis plants were transformed with either MerA or MerB coupled with aconstitutive promoter
The MerA plants were more tolerant to ionic mercury volatilised elementalmercury and were unaffected in their tolerance of methylmercury
The MerB Plants were significantly more tolerant to methylmercury and otherorganomercurials and could also convert methylmercury to ionic mercury whichis approximately 100 times less toxic to plants
MerA MerB double transgenics were produced in an F2 generation These plantsnot only showed a greater resistance to organic mercury when compared to theMerA MerB and wildtype plants but also capable of volatilizing mercury whensupplied with methylmercury
The same MerAMerB inserts have been used in other plant species includingtobacco(Nicotiana tabacum) yellow poplar(Liriodendron tulipifera)
Wetland species (bulrush and cat-tail) and water tolerant trees (willow and poplar)have also been targetted for transformation
Risk Assessment
Potential for the gene to recombine with other genes possibly
leading to the hyperaccumulation of non-contaminant
compounds
Reportermarker genes may also escape into the environment
The GM plants may revert to a wild type genotype
Advantages of phytoremediation
It is more economically viable using the same tools and
supplies as agriculture
It is less disruptive to the environment
Disposal sites are not needed
Aesthetically pleasing than traditional methods
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
Disadvantages of phytoremediation
Growing conditions required by the plant (ie Climate
geology altitude temperature)
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
Phytodegradation
It is the degradation or breakdownof organic contaminants by internaland external metabolic processesdriven by the plant
Mechanisms
(A) Plant enzymatic activity
oxygenases- hydrocarbons
nitroreductases- explosives
(B) Photosynthetic oxidation
Used in breakdown of ammunitionwastes chlorinated solvents suchas TCE (Trichloroethane)degradation of organic herbicides
Contd
External Process Internal Process
Rhizodegradation It is the breakdown of organic contaminants in the soil by soil dwelling
microbes which is enhanced by the rhizospherelsquos presence
Rhizosphere = soil + root + microbes
Symbiotic relation
Also called
Enhanced rhizosphere biodegradation
Phytostimulation
Plant assisted bioremediation
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 plants vascular system from the roots
to the leaves whereby the
contaminants evaporate
or volatilize into the air surrounding the
plant
Poplar trees volatilize up to 90 of the
TCE they absorb
Selenium and Mercury - Arabidopsis
thaliana L and tobacco
Phytohydraulics
The use of plants to control the migration of
subsurface water through the rapid uptake of
large volumes of water by the plants
Plants - acting as natural hydraulic pumps
A dense root network established near the
water table can transpire up to 300 gallons of
water per day
This fact has been utilized to decrease the
migration of contaminants from surface water
into the groundwater (below the water table)
and drinking water supplies
LEVEL OF POLLUTANT
Sampling
Field sampling quality assurance
Avoiding contamination of
samples
Equipment cleaning
Sample labels
Recent trend
Immunoassay testing and other
technology may be used to provide
on site screening
This work shall only be carried out
by properly trained personnel
Parameter Media Acceptable
Test
Methods
Petroleum
Hydrocarbo
ns
Water amp
soil
Gas
chromatogra
phy
Volatiles
(including
BTEX)
Water amp
soil
Infra-red
based
methods
Semi-
volatiles
(including
PAH)
water EPA
Standards
Analytical methods
Measurement of aquatic biodegradation rates by determining
heterotrophic uptake of radiolabeled pollutants
F K Pfaender and G W Bartholomew
bull The heterotrophic uptake technique was modified to provide a rapid
and simple technique for estimating the rates of biodegradation of
organic pollutants under environmental conditions
bull The methodology is based on an evaluation of uptake into cells and
subsequent respiration of radiolabeled organic substrates in short-
term experiments
bull The resulting data can be used to calculate either turnover times or
if multiple concentrations of substrate are used kinetic parameters
bull The procedure was applied to assess the biodegradation rates of m-
cresol chlorobenzene nitrilotriacetic acid and 124-
trichlorobenzene in fresh brackish and marine water samples from
the coastal areas of North Carolina
bull Saturation kinetics for uptake were obtained with each of the
compounds tested
bull Rates of metabolism were shown to be dependent on sample
location and time of year
Phytoremediation amp Biotechnology
Maximizing potential for phytoremediation
GM approaches can be used to over express the enzymes involved in
the existing plant metabolic pathways or to introduce new pathways
into plants
Richard Meagher and colleagues introduced a new pathway
into Arabidopsis to detoxify methylmercury a common form of
environmental pollutant to elemental mercury which can be volatilised
by the plant
Mer B
Organomercurial Lyase
Methyl Mercury Ionic Mercury
MerA
Mercuric Reductase
Ionic Mercury Elemental Form
The genes originated in gram-negative bacteria
Arabidopsis plants were transformed with either MerA or MerB coupled with aconstitutive promoter
The MerA plants were more tolerant to ionic mercury volatilised elementalmercury and were unaffected in their tolerance of methylmercury
The MerB Plants were significantly more tolerant to methylmercury and otherorganomercurials and could also convert methylmercury to ionic mercury whichis approximately 100 times less toxic to plants
MerA MerB double transgenics were produced in an F2 generation These plantsnot only showed a greater resistance to organic mercury when compared to theMerA MerB and wildtype plants but also capable of volatilizing mercury whensupplied with methylmercury
The same MerAMerB inserts have been used in other plant species includingtobacco(Nicotiana tabacum) yellow poplar(Liriodendron tulipifera)
Wetland species (bulrush and cat-tail) and water tolerant trees (willow and poplar)have also been targetted for transformation
Risk Assessment
Potential for the gene to recombine with other genes possibly
leading to the hyperaccumulation of non-contaminant
compounds
Reportermarker genes may also escape into the environment
The GM plants may revert to a wild type genotype
Advantages of phytoremediation
It is more economically viable using the same tools and
supplies as agriculture
It is less disruptive to the environment
Disposal sites are not needed
Aesthetically pleasing than traditional methods
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
Disadvantages of phytoremediation
Growing conditions required by the plant (ie Climate
geology altitude temperature)
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
Contd
External Process Internal Process
Rhizodegradation It is the breakdown of organic contaminants in the soil by soil dwelling
microbes which is enhanced by the rhizospherelsquos presence
Rhizosphere = soil + root + microbes
Symbiotic relation
Also called
Enhanced rhizosphere biodegradation
Phytostimulation
Plant assisted bioremediation
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 plants vascular system from the roots
to the leaves whereby the
contaminants evaporate
or volatilize into the air surrounding the
plant
Poplar trees volatilize up to 90 of the
TCE they absorb
Selenium and Mercury - Arabidopsis
thaliana L and tobacco
Phytohydraulics
The use of plants to control the migration of
subsurface water through the rapid uptake of
large volumes of water by the plants
Plants - acting as natural hydraulic pumps
A dense root network established near the
water table can transpire up to 300 gallons of
water per day
This fact has been utilized to decrease the
migration of contaminants from surface water
into the groundwater (below the water table)
and drinking water supplies
LEVEL OF POLLUTANT
Sampling
Field sampling quality assurance
Avoiding contamination of
samples
Equipment cleaning
Sample labels
Recent trend
Immunoassay testing and other
technology may be used to provide
on site screening
This work shall only be carried out
by properly trained personnel
Parameter Media Acceptable
Test
Methods
Petroleum
Hydrocarbo
ns
Water amp
soil
Gas
chromatogra
phy
Volatiles
(including
BTEX)
Water amp
soil
Infra-red
based
methods
Semi-
volatiles
(including
PAH)
water EPA
Standards
Analytical methods
Measurement of aquatic biodegradation rates by determining
heterotrophic uptake of radiolabeled pollutants
F K Pfaender and G W Bartholomew
bull The heterotrophic uptake technique was modified to provide a rapid
and simple technique for estimating the rates of biodegradation of
organic pollutants under environmental conditions
bull The methodology is based on an evaluation of uptake into cells and
subsequent respiration of radiolabeled organic substrates in short-
term experiments
bull The resulting data can be used to calculate either turnover times or
if multiple concentrations of substrate are used kinetic parameters
bull The procedure was applied to assess the biodegradation rates of m-
cresol chlorobenzene nitrilotriacetic acid and 124-
trichlorobenzene in fresh brackish and marine water samples from
the coastal areas of North Carolina
bull Saturation kinetics for uptake were obtained with each of the
compounds tested
bull Rates of metabolism were shown to be dependent on sample
location and time of year
Phytoremediation amp Biotechnology
Maximizing potential for phytoremediation
GM approaches can be used to over express the enzymes involved in
the existing plant metabolic pathways or to introduce new pathways
into plants
Richard Meagher and colleagues introduced a new pathway
into Arabidopsis to detoxify methylmercury a common form of
environmental pollutant to elemental mercury which can be volatilised
by the plant
Mer B
Organomercurial Lyase
Methyl Mercury Ionic Mercury
MerA
Mercuric Reductase
Ionic Mercury Elemental Form
The genes originated in gram-negative bacteria
Arabidopsis plants were transformed with either MerA or MerB coupled with aconstitutive promoter
The MerA plants were more tolerant to ionic mercury volatilised elementalmercury and were unaffected in their tolerance of methylmercury
The MerB Plants were significantly more tolerant to methylmercury and otherorganomercurials and could also convert methylmercury to ionic mercury whichis approximately 100 times less toxic to plants
MerA MerB double transgenics were produced in an F2 generation These plantsnot only showed a greater resistance to organic mercury when compared to theMerA MerB and wildtype plants but also capable of volatilizing mercury whensupplied with methylmercury
The same MerAMerB inserts have been used in other plant species includingtobacco(Nicotiana tabacum) yellow poplar(Liriodendron tulipifera)
Wetland species (bulrush and cat-tail) and water tolerant trees (willow and poplar)have also been targetted for transformation
Risk Assessment
Potential for the gene to recombine with other genes possibly
leading to the hyperaccumulation of non-contaminant
compounds
Reportermarker genes may also escape into the environment
The GM plants may revert to a wild type genotype
Advantages of phytoremediation
It is more economically viable using the same tools and
supplies as agriculture
It is less disruptive to the environment
Disposal sites are not needed
Aesthetically pleasing than traditional methods
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
Disadvantages of phytoremediation
Growing conditions required by the plant (ie Climate
geology altitude temperature)
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
Rhizodegradation It is the breakdown of organic contaminants in the soil by soil dwelling
microbes which is enhanced by the rhizospherelsquos presence
Rhizosphere = soil + root + microbes
Symbiotic relation
Also called
Enhanced rhizosphere biodegradation
Phytostimulation
Plant assisted bioremediation
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 plants vascular system from the roots
to the leaves whereby the
contaminants evaporate
or volatilize into the air surrounding the
plant
Poplar trees volatilize up to 90 of the
TCE they absorb
Selenium and Mercury - Arabidopsis
thaliana L and tobacco
Phytohydraulics
The use of plants to control the migration of
subsurface water through the rapid uptake of
large volumes of water by the plants
Plants - acting as natural hydraulic pumps
A dense root network established near the
water table can transpire up to 300 gallons of
water per day
This fact has been utilized to decrease the
migration of contaminants from surface water
into the groundwater (below the water table)
and drinking water supplies
LEVEL OF POLLUTANT
Sampling
Field sampling quality assurance
Avoiding contamination of
samples
Equipment cleaning
Sample labels
Recent trend
Immunoassay testing and other
technology may be used to provide
on site screening
This work shall only be carried out
by properly trained personnel
Parameter Media Acceptable
Test
Methods
Petroleum
Hydrocarbo
ns
Water amp
soil
Gas
chromatogra
phy
Volatiles
(including
BTEX)
Water amp
soil
Infra-red
based
methods
Semi-
volatiles
(including
PAH)
water EPA
Standards
Analytical methods
Measurement of aquatic biodegradation rates by determining
heterotrophic uptake of radiolabeled pollutants
F K Pfaender and G W Bartholomew
bull The heterotrophic uptake technique was modified to provide a rapid
and simple technique for estimating the rates of biodegradation of
organic pollutants under environmental conditions
bull The methodology is based on an evaluation of uptake into cells and
subsequent respiration of radiolabeled organic substrates in short-
term experiments
bull The resulting data can be used to calculate either turnover times or
if multiple concentrations of substrate are used kinetic parameters
bull The procedure was applied to assess the biodegradation rates of m-
cresol chlorobenzene nitrilotriacetic acid and 124-
trichlorobenzene in fresh brackish and marine water samples from
the coastal areas of North Carolina
bull Saturation kinetics for uptake were obtained with each of the
compounds tested
bull Rates of metabolism were shown to be dependent on sample
location and time of year
Phytoremediation amp Biotechnology
Maximizing potential for phytoremediation
GM approaches can be used to over express the enzymes involved in
the existing plant metabolic pathways or to introduce new pathways
into plants
Richard Meagher and colleagues introduced a new pathway
into Arabidopsis to detoxify methylmercury a common form of
environmental pollutant to elemental mercury which can be volatilised
by the plant
Mer B
Organomercurial Lyase
Methyl Mercury Ionic Mercury
MerA
Mercuric Reductase
Ionic Mercury Elemental Form
The genes originated in gram-negative bacteria
Arabidopsis plants were transformed with either MerA or MerB coupled with aconstitutive promoter
The MerA plants were more tolerant to ionic mercury volatilised elementalmercury and were unaffected in their tolerance of methylmercury
The MerB Plants were significantly more tolerant to methylmercury and otherorganomercurials and could also convert methylmercury to ionic mercury whichis approximately 100 times less toxic to plants
MerA MerB double transgenics were produced in an F2 generation These plantsnot only showed a greater resistance to organic mercury when compared to theMerA MerB and wildtype plants but also capable of volatilizing mercury whensupplied with methylmercury
The same MerAMerB inserts have been used in other plant species includingtobacco(Nicotiana tabacum) yellow poplar(Liriodendron tulipifera)
Wetland species (bulrush and cat-tail) and water tolerant trees (willow and poplar)have also been targetted for transformation
Risk Assessment
Potential for the gene to recombine with other genes possibly
leading to the hyperaccumulation of non-contaminant
compounds
Reportermarker genes may also escape into the environment
The GM plants may revert to a wild type genotype
Advantages of phytoremediation
It is more economically viable using the same tools and
supplies as agriculture
It is less disruptive to the environment
Disposal sites are not needed
Aesthetically pleasing than traditional methods
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
Disadvantages of phytoremediation
Growing conditions required by the plant (ie Climate
geology altitude temperature)
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
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 plants vascular system from the roots
to the leaves whereby the
contaminants evaporate
or volatilize into the air surrounding the
plant
Poplar trees volatilize up to 90 of the
TCE they absorb
Selenium and Mercury - Arabidopsis
thaliana L and tobacco
Phytohydraulics
The use of plants to control the migration of
subsurface water through the rapid uptake of
large volumes of water by the plants
Plants - acting as natural hydraulic pumps
A dense root network established near the
water table can transpire up to 300 gallons of
water per day
This fact has been utilized to decrease the
migration of contaminants from surface water
into the groundwater (below the water table)
and drinking water supplies
LEVEL OF POLLUTANT
Sampling
Field sampling quality assurance
Avoiding contamination of
samples
Equipment cleaning
Sample labels
Recent trend
Immunoassay testing and other
technology may be used to provide
on site screening
This work shall only be carried out
by properly trained personnel
Parameter Media Acceptable
Test
Methods
Petroleum
Hydrocarbo
ns
Water amp
soil
Gas
chromatogra
phy
Volatiles
(including
BTEX)
Water amp
soil
Infra-red
based
methods
Semi-
volatiles
(including
PAH)
water EPA
Standards
Analytical methods
Measurement of aquatic biodegradation rates by determining
heterotrophic uptake of radiolabeled pollutants
F K Pfaender and G W Bartholomew
bull The heterotrophic uptake technique was modified to provide a rapid
and simple technique for estimating the rates of biodegradation of
organic pollutants under environmental conditions
bull The methodology is based on an evaluation of uptake into cells and
subsequent respiration of radiolabeled organic substrates in short-
term experiments
bull The resulting data can be used to calculate either turnover times or
if multiple concentrations of substrate are used kinetic parameters
bull The procedure was applied to assess the biodegradation rates of m-
cresol chlorobenzene nitrilotriacetic acid and 124-
trichlorobenzene in fresh brackish and marine water samples from
the coastal areas of North Carolina
bull Saturation kinetics for uptake were obtained with each of the
compounds tested
bull Rates of metabolism were shown to be dependent on sample
location and time of year
Phytoremediation amp Biotechnology
Maximizing potential for phytoremediation
GM approaches can be used to over express the enzymes involved in
the existing plant metabolic pathways or to introduce new pathways
into plants
Richard Meagher and colleagues introduced a new pathway
into Arabidopsis to detoxify methylmercury a common form of
environmental pollutant to elemental mercury which can be volatilised
by the plant
Mer B
Organomercurial Lyase
Methyl Mercury Ionic Mercury
MerA
Mercuric Reductase
Ionic Mercury Elemental Form
The genes originated in gram-negative bacteria
Arabidopsis plants were transformed with either MerA or MerB coupled with aconstitutive promoter
The MerA plants were more tolerant to ionic mercury volatilised elementalmercury and were unaffected in their tolerance of methylmercury
The MerB Plants were significantly more tolerant to methylmercury and otherorganomercurials and could also convert methylmercury to ionic mercury whichis approximately 100 times less toxic to plants
MerA MerB double transgenics were produced in an F2 generation These plantsnot only showed a greater resistance to organic mercury when compared to theMerA MerB and wildtype plants but also capable of volatilizing mercury whensupplied with methylmercury
The same MerAMerB inserts have been used in other plant species includingtobacco(Nicotiana tabacum) yellow poplar(Liriodendron tulipifera)
Wetland species (bulrush and cat-tail) and water tolerant trees (willow and poplar)have also been targetted for transformation
Risk Assessment
Potential for the gene to recombine with other genes possibly
leading to the hyperaccumulation of non-contaminant
compounds
Reportermarker genes may also escape into the environment
The GM plants may revert to a wild type genotype
Advantages of phytoremediation
It is more economically viable using the same tools and
supplies as agriculture
It is less disruptive to the environment
Disposal sites are not needed
Aesthetically pleasing than traditional methods
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
Disadvantages of phytoremediation
Growing conditions required by the plant (ie Climate
geology altitude temperature)
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
Phytohydraulics
The use of plants to control the migration of
subsurface water through the rapid uptake of
large volumes of water by the plants
Plants - acting as natural hydraulic pumps
A dense root network established near the
water table can transpire up to 300 gallons of
water per day
This fact has been utilized to decrease the
migration of contaminants from surface water
into the groundwater (below the water table)
and drinking water supplies
LEVEL OF POLLUTANT
Sampling
Field sampling quality assurance
Avoiding contamination of
samples
Equipment cleaning
Sample labels
Recent trend
Immunoassay testing and other
technology may be used to provide
on site screening
This work shall only be carried out
by properly trained personnel
Parameter Media Acceptable
Test
Methods
Petroleum
Hydrocarbo
ns
Water amp
soil
Gas
chromatogra
phy
Volatiles
(including
BTEX)
Water amp
soil
Infra-red
based
methods
Semi-
volatiles
(including
PAH)
water EPA
Standards
Analytical methods
Measurement of aquatic biodegradation rates by determining
heterotrophic uptake of radiolabeled pollutants
F K Pfaender and G W Bartholomew
bull The heterotrophic uptake technique was modified to provide a rapid
and simple technique for estimating the rates of biodegradation of
organic pollutants under environmental conditions
bull The methodology is based on an evaluation of uptake into cells and
subsequent respiration of radiolabeled organic substrates in short-
term experiments
bull The resulting data can be used to calculate either turnover times or
if multiple concentrations of substrate are used kinetic parameters
bull The procedure was applied to assess the biodegradation rates of m-
cresol chlorobenzene nitrilotriacetic acid and 124-
trichlorobenzene in fresh brackish and marine water samples from
the coastal areas of North Carolina
bull Saturation kinetics for uptake were obtained with each of the
compounds tested
bull Rates of metabolism were shown to be dependent on sample
location and time of year
Phytoremediation amp Biotechnology
Maximizing potential for phytoremediation
GM approaches can be used to over express the enzymes involved in
the existing plant metabolic pathways or to introduce new pathways
into plants
Richard Meagher and colleagues introduced a new pathway
into Arabidopsis to detoxify methylmercury a common form of
environmental pollutant to elemental mercury which can be volatilised
by the plant
Mer B
Organomercurial Lyase
Methyl Mercury Ionic Mercury
MerA
Mercuric Reductase
Ionic Mercury Elemental Form
The genes originated in gram-negative bacteria
Arabidopsis plants were transformed with either MerA or MerB coupled with aconstitutive promoter
The MerA plants were more tolerant to ionic mercury volatilised elementalmercury and were unaffected in their tolerance of methylmercury
The MerB Plants were significantly more tolerant to methylmercury and otherorganomercurials and could also convert methylmercury to ionic mercury whichis approximately 100 times less toxic to plants
MerA MerB double transgenics were produced in an F2 generation These plantsnot only showed a greater resistance to organic mercury when compared to theMerA MerB and wildtype plants but also capable of volatilizing mercury whensupplied with methylmercury
The same MerAMerB inserts have been used in other plant species includingtobacco(Nicotiana tabacum) yellow poplar(Liriodendron tulipifera)
Wetland species (bulrush and cat-tail) and water tolerant trees (willow and poplar)have also been targetted for transformation
Risk Assessment
Potential for the gene to recombine with other genes possibly
leading to the hyperaccumulation of non-contaminant
compounds
Reportermarker genes may also escape into the environment
The GM plants may revert to a wild type genotype
Advantages of phytoremediation
It is more economically viable using the same tools and
supplies as agriculture
It is less disruptive to the environment
Disposal sites are not needed
Aesthetically pleasing than traditional methods
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
Disadvantages of phytoremediation
Growing conditions required by the plant (ie Climate
geology altitude temperature)
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
LEVEL OF POLLUTANT
Sampling
Field sampling quality assurance
Avoiding contamination of
samples
Equipment cleaning
Sample labels
Recent trend
Immunoassay testing and other
technology may be used to provide
on site screening
This work shall only be carried out
by properly trained personnel
Parameter Media Acceptable
Test
Methods
Petroleum
Hydrocarbo
ns
Water amp
soil
Gas
chromatogra
phy
Volatiles
(including
BTEX)
Water amp
soil
Infra-red
based
methods
Semi-
volatiles
(including
PAH)
water EPA
Standards
Analytical methods
Measurement of aquatic biodegradation rates by determining
heterotrophic uptake of radiolabeled pollutants
F K Pfaender and G W Bartholomew
bull The heterotrophic uptake technique was modified to provide a rapid
and simple technique for estimating the rates of biodegradation of
organic pollutants under environmental conditions
bull The methodology is based on an evaluation of uptake into cells and
subsequent respiration of radiolabeled organic substrates in short-
term experiments
bull The resulting data can be used to calculate either turnover times or
if multiple concentrations of substrate are used kinetic parameters
bull The procedure was applied to assess the biodegradation rates of m-
cresol chlorobenzene nitrilotriacetic acid and 124-
trichlorobenzene in fresh brackish and marine water samples from
the coastal areas of North Carolina
bull Saturation kinetics for uptake were obtained with each of the
compounds tested
bull Rates of metabolism were shown to be dependent on sample
location and time of year
Phytoremediation amp Biotechnology
Maximizing potential for phytoremediation
GM approaches can be used to over express the enzymes involved in
the existing plant metabolic pathways or to introduce new pathways
into plants
Richard Meagher and colleagues introduced a new pathway
into Arabidopsis to detoxify methylmercury a common form of
environmental pollutant to elemental mercury which can be volatilised
by the plant
Mer B
Organomercurial Lyase
Methyl Mercury Ionic Mercury
MerA
Mercuric Reductase
Ionic Mercury Elemental Form
The genes originated in gram-negative bacteria
Arabidopsis plants were transformed with either MerA or MerB coupled with aconstitutive promoter
The MerA plants were more tolerant to ionic mercury volatilised elementalmercury and were unaffected in their tolerance of methylmercury
The MerB Plants were significantly more tolerant to methylmercury and otherorganomercurials and could also convert methylmercury to ionic mercury whichis approximately 100 times less toxic to plants
MerA MerB double transgenics were produced in an F2 generation These plantsnot only showed a greater resistance to organic mercury when compared to theMerA MerB and wildtype plants but also capable of volatilizing mercury whensupplied with methylmercury
The same MerAMerB inserts have been used in other plant species includingtobacco(Nicotiana tabacum) yellow poplar(Liriodendron tulipifera)
Wetland species (bulrush and cat-tail) and water tolerant trees (willow and poplar)have also been targetted for transformation
Risk Assessment
Potential for the gene to recombine with other genes possibly
leading to the hyperaccumulation of non-contaminant
compounds
Reportermarker genes may also escape into the environment
The GM plants may revert to a wild type genotype
Advantages of phytoremediation
It is more economically viable using the same tools and
supplies as agriculture
It is less disruptive to the environment
Disposal sites are not needed
Aesthetically pleasing than traditional methods
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
Disadvantages of phytoremediation
Growing conditions required by the plant (ie Climate
geology altitude temperature)
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
Measurement of aquatic biodegradation rates by determining
heterotrophic uptake of radiolabeled pollutants
F K Pfaender and G W Bartholomew
bull The heterotrophic uptake technique was modified to provide a rapid
and simple technique for estimating the rates of biodegradation of
organic pollutants under environmental conditions
bull The methodology is based on an evaluation of uptake into cells and
subsequent respiration of radiolabeled organic substrates in short-
term experiments
bull The resulting data can be used to calculate either turnover times or
if multiple concentrations of substrate are used kinetic parameters
bull The procedure was applied to assess the biodegradation rates of m-
cresol chlorobenzene nitrilotriacetic acid and 124-
trichlorobenzene in fresh brackish and marine water samples from
the coastal areas of North Carolina
bull Saturation kinetics for uptake were obtained with each of the
compounds tested
bull Rates of metabolism were shown to be dependent on sample
location and time of year
Phytoremediation amp Biotechnology
Maximizing potential for phytoremediation
GM approaches can be used to over express the enzymes involved in
the existing plant metabolic pathways or to introduce new pathways
into plants
Richard Meagher and colleagues introduced a new pathway
into Arabidopsis to detoxify methylmercury a common form of
environmental pollutant to elemental mercury which can be volatilised
by the plant
Mer B
Organomercurial Lyase
Methyl Mercury Ionic Mercury
MerA
Mercuric Reductase
Ionic Mercury Elemental Form
The genes originated in gram-negative bacteria
Arabidopsis plants were transformed with either MerA or MerB coupled with aconstitutive promoter
The MerA plants were more tolerant to ionic mercury volatilised elementalmercury and were unaffected in their tolerance of methylmercury
The MerB Plants were significantly more tolerant to methylmercury and otherorganomercurials and could also convert methylmercury to ionic mercury whichis approximately 100 times less toxic to plants
MerA MerB double transgenics were produced in an F2 generation These plantsnot only showed a greater resistance to organic mercury when compared to theMerA MerB and wildtype plants but also capable of volatilizing mercury whensupplied with methylmercury
The same MerAMerB inserts have been used in other plant species includingtobacco(Nicotiana tabacum) yellow poplar(Liriodendron tulipifera)
Wetland species (bulrush and cat-tail) and water tolerant trees (willow and poplar)have also been targetted for transformation
Risk Assessment
Potential for the gene to recombine with other genes possibly
leading to the hyperaccumulation of non-contaminant
compounds
Reportermarker genes may also escape into the environment
The GM plants may revert to a wild type genotype
Advantages of phytoremediation
It is more economically viable using the same tools and
supplies as agriculture
It is less disruptive to the environment
Disposal sites are not needed
Aesthetically pleasing than traditional methods
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
Disadvantages of phytoremediation
Growing conditions required by the plant (ie Climate
geology altitude temperature)
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
Phytoremediation amp Biotechnology
Maximizing potential for phytoremediation
GM approaches can be used to over express the enzymes involved in
the existing plant metabolic pathways or to introduce new pathways
into plants
Richard Meagher and colleagues introduced a new pathway
into Arabidopsis to detoxify methylmercury a common form of
environmental pollutant to elemental mercury which can be volatilised
by the plant
Mer B
Organomercurial Lyase
Methyl Mercury Ionic Mercury
MerA
Mercuric Reductase
Ionic Mercury Elemental Form
The genes originated in gram-negative bacteria
Arabidopsis plants were transformed with either MerA or MerB coupled with aconstitutive promoter
The MerA plants were more tolerant to ionic mercury volatilised elementalmercury and were unaffected in their tolerance of methylmercury
The MerB Plants were significantly more tolerant to methylmercury and otherorganomercurials and could also convert methylmercury to ionic mercury whichis approximately 100 times less toxic to plants
MerA MerB double transgenics were produced in an F2 generation These plantsnot only showed a greater resistance to organic mercury when compared to theMerA MerB and wildtype plants but also capable of volatilizing mercury whensupplied with methylmercury
The same MerAMerB inserts have been used in other plant species includingtobacco(Nicotiana tabacum) yellow poplar(Liriodendron tulipifera)
Wetland species (bulrush and cat-tail) and water tolerant trees (willow and poplar)have also been targetted for transformation
Risk Assessment
Potential for the gene to recombine with other genes possibly
leading to the hyperaccumulation of non-contaminant
compounds
Reportermarker genes may also escape into the environment
The GM plants may revert to a wild type genotype
Advantages of phytoremediation
It is more economically viable using the same tools and
supplies as agriculture
It is less disruptive to the environment
Disposal sites are not needed
Aesthetically pleasing than traditional methods
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
Disadvantages of phytoremediation
Growing conditions required by the plant (ie Climate
geology altitude temperature)
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
Mer B
Organomercurial Lyase
Methyl Mercury Ionic Mercury
MerA
Mercuric Reductase
Ionic Mercury Elemental Form
The genes originated in gram-negative bacteria
Arabidopsis plants were transformed with either MerA or MerB coupled with aconstitutive promoter
The MerA plants were more tolerant to ionic mercury volatilised elementalmercury and were unaffected in their tolerance of methylmercury
The MerB Plants were significantly more tolerant to methylmercury and otherorganomercurials and could also convert methylmercury to ionic mercury whichis approximately 100 times less toxic to plants
MerA MerB double transgenics were produced in an F2 generation These plantsnot only showed a greater resistance to organic mercury when compared to theMerA MerB and wildtype plants but also capable of volatilizing mercury whensupplied with methylmercury
The same MerAMerB inserts have been used in other plant species includingtobacco(Nicotiana tabacum) yellow poplar(Liriodendron tulipifera)
Wetland species (bulrush and cat-tail) and water tolerant trees (willow and poplar)have also been targetted for transformation
Risk Assessment
Potential for the gene to recombine with other genes possibly
leading to the hyperaccumulation of non-contaminant
compounds
Reportermarker genes may also escape into the environment
The GM plants may revert to a wild type genotype
Advantages of phytoremediation
It is more economically viable using the same tools and
supplies as agriculture
It is less disruptive to the environment
Disposal sites are not needed
Aesthetically pleasing than traditional methods
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
Disadvantages of phytoremediation
Growing conditions required by the plant (ie Climate
geology altitude temperature)
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
Arabidopsis plants were transformed with either MerA or MerB coupled with aconstitutive promoter
The MerA plants were more tolerant to ionic mercury volatilised elementalmercury and were unaffected in their tolerance of methylmercury
The MerB Plants were significantly more tolerant to methylmercury and otherorganomercurials and could also convert methylmercury to ionic mercury whichis approximately 100 times less toxic to plants
MerA MerB double transgenics were produced in an F2 generation These plantsnot only showed a greater resistance to organic mercury when compared to theMerA MerB and wildtype plants but also capable of volatilizing mercury whensupplied with methylmercury
The same MerAMerB inserts have been used in other plant species includingtobacco(Nicotiana tabacum) yellow poplar(Liriodendron tulipifera)
Wetland species (bulrush and cat-tail) and water tolerant trees (willow and poplar)have also been targetted for transformation
Risk Assessment
Potential for the gene to recombine with other genes possibly
leading to the hyperaccumulation of non-contaminant
compounds
Reportermarker genes may also escape into the environment
The GM plants may revert to a wild type genotype
Advantages of phytoremediation
It is more economically viable using the same tools and
supplies as agriculture
It is less disruptive to the environment
Disposal sites are not needed
Aesthetically pleasing than traditional methods
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
Disadvantages of phytoremediation
Growing conditions required by the plant (ie Climate
geology altitude temperature)
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
Risk Assessment
Potential for the gene to recombine with other genes possibly
leading to the hyperaccumulation of non-contaminant
compounds
Reportermarker genes may also escape into the environment
The GM plants may revert to a wild type genotype
Advantages of phytoremediation
It is more economically viable using the same tools and
supplies as agriculture
It is less disruptive to the environment
Disposal sites are not needed
Aesthetically pleasing than traditional methods
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
Disadvantages of phytoremediation
Growing conditions required by the plant (ie Climate
geology altitude temperature)
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
Advantages of phytoremediation
It is more economically viable using the same tools and
supplies as agriculture
It is less disruptive to the environment
Disposal sites are not needed
Aesthetically pleasing than traditional methods
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
Disadvantages of phytoremediation
Growing conditions required by the plant (ie Climate
geology altitude temperature)
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
Disadvantages of phytoremediation
Growing conditions required by the plant (ie Climate
geology altitude temperature)
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