phytoremediation- wiki notes
introduction
phytoremediation- using plants to take care of contamination
to “contain, remove, or render harmless“ contaminants
Cost-effective, BUT- not been shown to have significant change
uses plant’s ability to “concentrate elements and compounds” and “detoxify various compounds“
comes from hyperaccumulators which bioaccumulate chemicals
background
phytoremediation can be used on polluted soil or water
used for soils with:
cadmium
lead
aluminium
arsenic
antimony
such metals cause oxidative stress, break down cell membrane, cause many other negative effects etc.
SUCCESSFUL:
abandoned mines- polychlorinated biphenyl dumpings- contaminated soil, water, and air
metal, peticides, solvents, explosives, crude oil
toxic waste mitigated: mustard plants, alpine pennycress, hemp, pigweed
Limitations
limited by how extensive plant root systems are
even with phytoremediation- groundwater can still be contaminated
plants may, of course, die
some metals are stuck to soil- plant can’t extract
Processes
phytoextraction
takes contaminants- better for the plant- makes for a healthier plant- becomes a part of the plant
hyperaccumulators
can also be done with plants that have a low amt of pollutant capacity- but grow very fast- still remove a lot of pollutants
must be done with many different harvest cycles to ensure a fully clean area
Hyperaccumulators are metallophytes- plants that can withstand lots of heavy metals
list of toxins and plants that can accumulate
arsenic- sunflower, chinese brake fern
cadmium- willow ( additionally- willow was good at cadmium, zinc, copper, and can transport large amt, large biomass production, can also be used for BIO ENERGY in biomass power plants
cadmium and zinc- alpine pennycress, can accumulate a large amt, copper slows growth
chromium- tomatoes (some promise)
lead- indian mustard, ragweed, hemp dogbane, poplar
sodium chloride (for fields flooded with seawater)- barley, sugar beets
caesium-137, strontium-90,, sunflowers after chernobyl
mercury, selenium, PCBs- TRANSGENIC PLANTS- WITH GENES FOR BACTERIAL ENZYMES
phytostabilization
“reduces mobility of substances in environment- less leakage or leaching
fortifies “long-term stabilization”
binds pollutants to soil-less available for organism uptake
isolates toxins near roots but not in tissues- pollutants less available- reduces exposure
plants can secrete subtance- triggers chem reaction, makes metal less toxic
example:
vegetative cap- mine tailings
can increase or decrease radio source mobility- specific grass used makes the difference
phytodegradation
plants degrade organic pollutants in soil or in plant
using enzymes secreted from roots, take in the polutants and transpire them
best with herbicides, trichloroethylene, methyl tert-butyl ether
Chemical modification of environmental substances due to plant metabolism
inactivation, degradation, or immobillization
orgtanic. pollutants- Cannas plant’s metabolism detoxifiys them
plant roots+microorganisms - metabolize
cant break down into basic molecules(water, co2 etc)
structural change - not full breakdown
phytodegradation- metabolism
Phase 1
uptake in xenobiotics
increase polarity of xenobiotics- by adding hydtoxyl groups
enzymes used: peroxidases, phenoloxidases, esterases, nitroreductases
phase 2
biomolecules (glucose, amino acids), added to polarized xenobiotics- makes even more polar
(increasing polarity- decreaseds toxicity)
phase 3
xenobiotics create a structure “sequestered” - polymerize like a lignin
stored within the plant
can be toxic to animals that eat them
xenobiotic= foreign substance
phytostimulation
making soil microbes better to degrade xenobiotics
uses roots mainly
happens in rhizosphere- soil layer that surrounds roots
plants release carbs and acids that create microbe activity- biodegrades- microoranisms can digest toxins
effective in hydrocarbons, PCB, PAH
can use aquatic plants- atrazine, hornwort
Phytovolatilization- turns into vapor
removing substances from soil and water- release into air
can be phytodegradation that resulted in less harmgul substances
xenobiotics takes up and transpirated, gets evaporated in atmosphere
volatilization happens at stem and leaves
indirect volatilization- volatilized at roots
Se and Hg--- good phytovolatilization from soil qith poplar trees (high transpiration rate)
rhizofiltration
water filtered through roots to remove xenobiotics
substances remain in roots
used to cleangroundwater- planting directly in site- or removedd and treated in a diff location
biological hydraulic containment
when plants draw water from soil into roots and out of plant
decreases downward mov ement of contaminants into water
phytodesalination
halophytes (plants that can withstand salty soil)
used to remove salt from soil and improve quality for other plants
GENETICS!!!!!!
breeding and GENETIC ENGINEERING are “powerful tools“ for phytoremediation
genes can come from a microorganism or from another plant thats better suited for cleanup
EG::: genes for nitroreductase from bacteria- put into tobacco- faster TNT removal- better resistance to TNT
new discovery- mechanism in plants that lets them grow even when soil is toxic.
natural biodegradable compounds, eg. exogenous polyamines, lets plants withstand 500x higher amt of pollutants
hyperaccumulators and biotic interactions
hyperaccumulator- concentrate toxins greater than or equal to set amount (amount varies by pollutant)
eg. >100mg/kg for nickel, >10,000mg/kg for zinc
ability to accumulate- hypertolerance (just thru evolution and adaptations)
phytoscreening
biosensors of subsurface contamination- toxins can be dealt with quickly
extract part of plant to see if contaminated
can grow in high conc of metals
can absorb metal through roots
can store high amts of metal in tissues
ability to hyperaccumulate due to different GENE EXPRESSION AND REGULATION of genes found in said species and related ones
in normal plants- more metal in roots than shoots
in HAs (hyperaccumulator) plants- more metal in leaves--- metals are brought to shoots to protect roots from toxins
lack of knowledge on tolerance::::::::::
tolerance and accumulation are separate and moderated by genetics and physiological things
species spec characgterists
alpine pennycress accumulates more zinc but when there is a low supply
active accumulation
low concentration
passive accumulation
very high concentration
HA (hyperaccumulator) geenes foiund in 450+ species
ability to hyperaccumulate if::::envifronmental expostre and expressiioin of ZIP gene framily
envtion exposure- only plants that are exposed to such metals have the opportunity to absorb such metal
but comes down to genes
can b inheritied
ZIP family- encodes Cd, Mn, Fe, and Zn transporters, supplying ZN to metalloproteins
ZTP and ZNT families- zinc transproters
zinc transporters cant discrinimtate agaisnt speciici metal ions- can accumulate a wide variety of metals
hyperaccumulation happens with an overexpressed Zn transport system- plants cant differentiate between different kinds of metals
another important trait: good translocation of metal to shoot.
usually tolerated by plants that are native to metalliferous soils
ways plants can tolerate
exclusion:
resist metal (bad)
absorbtion and sequestratioin (good for remediaton)- pass metal thru shoot and accumulate it
hyperaccumulators need this ^ and the ability to absorb 100x more metal than others
metallophyte
plant that can tolerate high amounts of heavy metals
Obligate metallophytes- can only survive with these metals
facultative metallophytes- can tolerate them, but arent bound to them
introduction
phytoremediation- using plants to take care of contamination
to “contain, remove, or render harmless“ contaminants
Cost-effective, BUT- not been shown to have significant change
uses plant’s ability to “concentrate elements and compounds” and “detoxify various compounds“
comes from hyperaccumulators which bioaccumulate chemicals
background
phytoremediation can be used on polluted soil or water
used for soils with:
cadmium
lead
aluminium
arsenic
antimony
such metals cause oxidative stress, break down cell membrane, cause many other negative effects etc.
SUCCESSFUL:
abandoned mines- polychlorinated biphenyl dumpings- contaminated soil, water, and air
metal, peticides, solvents, explosives, crude oil
toxic waste mitigated: mustard plants, alpine pennycress, hemp, pigweed
Limitations
limited by how extensive plant root systems are
even with phytoremediation- groundwater can still be contaminated
plants may, of course, die
some metals are stuck to soil- plant can’t extract
Processes
phytoextraction
takes contaminants- better for the plant- makes for a healthier plant- becomes a part of the plant
hyperaccumulators
can also be done with plants that have a low amt of pollutant capacity- but grow very fast- still remove a lot of pollutants
must be done with many different harvest cycles to ensure a fully clean area
Hyperaccumulators are metallophytes- plants that can withstand lots of heavy metals
list of toxins and plants that can accumulate
arsenic- sunflower, chinese brake fern
cadmium- willow ( additionally- willow was good at cadmium, zinc, copper, and can transport large amt, large biomass production, can also be used for BIO ENERGY in biomass power plants
cadmium and zinc- alpine pennycress, can accumulate a large amt, copper slows growth
chromium- tomatoes (some promise)
lead- indian mustard, ragweed, hemp dogbane, poplar
sodium chloride (for fields flooded with seawater)- barley, sugar beets
caesium-137, strontium-90,, sunflowers after chernobyl
mercury, selenium, PCBs- TRANSGENIC PLANTS- WITH GENES FOR BACTERIAL ENZYMES
phytostabilization
“reduces mobility of substances in environment- less leakage or leaching
fortifies “long-term stabilization”
binds pollutants to soil-less available for organism uptake
isolates toxins near roots but not in tissues- pollutants less available- reduces exposure
plants can secrete subtance- triggers chem reaction, makes metal less toxic
example:
vegetative cap- mine tailings
can increase or decrease radio source mobility- specific grass used makes the difference
phytodegradation
plants degrade organic pollutants in soil or in plant
using enzymes secreted from roots, take in the polutants and transpire them
best with herbicides, trichloroethylene, methyl tert-butyl ether
Chemical modification of environmental substances due to plant metabolism
inactivation, degradation, or immobillization
orgtanic. pollutants- Cannas plant’s metabolism detoxifiys them
plant roots+microorganisms - metabolize
cant break down into basic molecules(water, co2 etc)
structural change - not full breakdown
phytodegradation- metabolism
Phase 1
uptake in xenobiotics
increase polarity of xenobiotics- by adding hydtoxyl groups
enzymes used: peroxidases, phenoloxidases, esterases, nitroreductases
phase 2
biomolecules (glucose, amino acids), added to polarized xenobiotics- makes even more polar
(increasing polarity- decreaseds toxicity)
phase 3
xenobiotics create a structure “sequestered” - polymerize like a lignin
stored within the plant
can be toxic to animals that eat them
xenobiotic= foreign substance
phytostimulation
making soil microbes better to degrade xenobiotics
uses roots mainly
happens in rhizosphere- soil layer that surrounds roots
plants release carbs and acids that create microbe activity- biodegrades- microoranisms can digest toxins
effective in hydrocarbons, PCB, PAH
can use aquatic plants- atrazine, hornwort
Phytovolatilization- turns into vapor
removing substances from soil and water- release into air
can be phytodegradation that resulted in less harmgul substances
xenobiotics takes up and transpirated, gets evaporated in atmosphere
volatilization happens at stem and leaves
indirect volatilization- volatilized at roots
Se and Hg--- good phytovolatilization from soil qith poplar trees (high transpiration rate)
rhizofiltration
water filtered through roots to remove xenobiotics
substances remain in roots
used to cleangroundwater- planting directly in site- or removedd and treated in a diff location
biological hydraulic containment
when plants draw water from soil into roots and out of plant
decreases downward mov ement of contaminants into water
phytodesalination
halophytes (plants that can withstand salty soil)
used to remove salt from soil and improve quality for other plants
GENETICS!!!!!!
breeding and GENETIC ENGINEERING are “powerful tools“ for phytoremediation
genes can come from a microorganism or from another plant thats better suited for cleanup
EG::: genes for nitroreductase from bacteria- put into tobacco- faster TNT removal- better resistance to TNT
new discovery- mechanism in plants that lets them grow even when soil is toxic.
natural biodegradable compounds, eg. exogenous polyamines, lets plants withstand 500x higher amt of pollutants
hyperaccumulators and biotic interactions
hyperaccumulator- concentrate toxins greater than or equal to set amount (amount varies by pollutant)
eg. >100mg/kg for nickel, >10,000mg/kg for zinc
ability to accumulate- hypertolerance (just thru evolution and adaptations)
phytoscreening
biosensors of subsurface contamination- toxins can be dealt with quickly
extract part of plant to see if contaminated
can grow in high conc of metals
can absorb metal through roots
can store high amts of metal in tissues
ability to hyperaccumulate due to different GENE EXPRESSION AND REGULATION of genes found in said species and related ones
in normal plants- more metal in roots than shoots
in HAs (hyperaccumulator) plants- more metal in leaves--- metals are brought to shoots to protect roots from toxins
lack of knowledge on tolerance::::::::::
tolerance and accumulation are separate and moderated by genetics and physiological things
species spec characgterists
alpine pennycress accumulates more zinc but when there is a low supply
active accumulation
low concentration
passive accumulation
very high concentration
HA (hyperaccumulator) geenes foiund in 450+ species
ability to hyperaccumulate if::::envifronmental expostre and expressiioin of ZIP gene framily
envtion exposure- only plants that are exposed to such metals have the opportunity to absorb such metal
but comes down to genes
can b inheritied
ZIP family- encodes Cd, Mn, Fe, and Zn transporters, supplying ZN to metalloproteins
ZTP and ZNT families- zinc transproters
zinc transporters cant discrinimtate agaisnt speciici metal ions- can accumulate a wide variety of metals
hyperaccumulation happens with an overexpressed Zn transport system- plants cant differentiate between different kinds of metals
another important trait: good translocation of metal to shoot.
usually tolerated by plants that are native to metalliferous soils
ways plants can tolerate
exclusion:
resist metal (bad)
absorbtion and sequestratioin (good for remediaton)- pass metal thru shoot and accumulate it
hyperaccumulators need this ^ and the ability to absorb 100x more metal than others
metallophyte
plant that can tolerate high amounts of heavy metals
Obligate metallophytes- can only survive with these metals
facultative metallophytes- can tolerate them, but arent bound to them