Phytoremediation

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Phytoremediation

• Or, using plants to clean up human messes

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Types of phytoremediation

• Phytoextraction - uptake of substances from the
  environment, with storage in the plant (usually
  involves hyperaccumulation).
• 2. Phytostabilization - reducing the movement or
  transfer of substances in the environment, for
  example, limiting the leaching of soil
  contaminants.
• 3. Phytostimulation - enhancement of microbial
  activity for the degradation of contaminants,
  typically around plant roots.
• 4. Phytotransformation - uptake of substances
  from the environment, with degradation occurring
  within the plant (phytodegradation).
• 5. Phytovolatilization - removal of substances
  from the soil or water with release into the air,
  possibly after degradation.
• 6. Rhizofiltration - the removal of toxic
  materials from groundwater through root
  activity.

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Phytoextraction of excess nutrients Pig slurry
cleanup
Using duckweed (Lemna)
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Heavy metal hyperaccumulators
Thlaspi montanum var. montanum, a
Ni-hyperaccumulator plant that grows on
Serpentine soils, research of Martha Palamino,
IB graduate student (UC Berkeley).
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Arsenic contamination removed by phytoextraction

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

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Arabidopsis engineered tohyperaccumulatearsenic
Engineering tolerance and hyperaccumulation of
arsenic in plants by combining arsenate reductase
and -glutamylcysteine synthetase expression. Om
Parkash Dhankher, Yujing Li, Barry P. Rosen, Jin
Shi, David Salt, Julie F. Senecoff, Nupur A.
Sashti  Richard B. Meagher
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Phytostabilization of mercury by willow roots
Yaodong Wang, 2004
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Phytodetoxification of mercuric compounds
Bizily, S., Rugh, C., Meagher, R. (2000)
 Phytodetoxification of hazardous
organomercurials by genetically engineered
plants.  Nature Biotechnology.  18213-217.    
 Methylmercury is found in wetlands and aquatic
sediments worldwide.  Both ionic mercury and
methylmercury are absorbed in the
gastrointestinal tract of animals, but
methylmercury is retained much longer in the body
and is, therefore, is carried up through the food
chain more efficiently.  Plants engineered with
both the merA and merB genes should be able to
extract methylmercury from contaminated
environments and transpire Hg(0) into the
atmosphere.       Because Hg(0) resides in the
atmosphere for approximately two years,
transpired Hg(0) will be diluted to much lower
concentrations before being redeposited into
terrestrial waters and sediments rather than
being concentrated in one area.  Additionally the
amount of Hg(0) emitted from sites undergoing
phytovolitalization can be regulated and will
most likely be small in comparison to the
concentrations of Hg(0) already in the
atmosphere.
merB       merA/merB      merA       control    
   
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Rhizofiltration sunflowers after Chernobyl
disaster

Plants on rafts in pondwater removed
radionuclides of strontium, cesium, etc.
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Phytodegradation of pesticides by a notorious
pest plant

• The potential of water hyacinth (Eichhornia
  crassipes) to remove a phosphorus pesticide
  ethion were investigated. The disappearance rate
  constants of ethion . . . implied that plant
  uptake and phytodegradation contributed 69 and
  that of microbial degradation took up 12 to the
  removal of the applied ethion. The accumulated
  ethion in live water hyacinth plant decreased by
  55-91 in shoots and 74-81 in roots after the
  plant growing 1 week in ethion free culture
  solutions, suggesting that plant uptake and
  phytodegradation might be the dominant process
  for ethion removal by the plant. This plant might
  be utilized as an efficient, economical and
  ecological alternative to accelerate the removal
  and degradation of agro-industrial wastewater
  polluted with ethion.Xia H, Ma X. 2006

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

• A MASS BALANCE FIELD TRIAL OF CARBON
  TETRACHLORIDE PHYTOREMEDIATION USING POPLAR
  PHYTODEGRADATION IS THE LIKELY FATE
• Michael Dossett1, and Xiaoping Wang2, and Stuart
  E. Strand3

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Uptake and metabolic use of cyanide by willows
Transport and metabolism of free cyanide and iron
cyanide complexes by willow S. EBBS1, J. BUSHEY2,
S. POSTON1, D. KOSMA1, M. SAMIOTAKIS1 D. DZOMBAK
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Remediation of saline soils
Salicornia (pickleweed) accumulates salt in
vacuole. A form of table salt can then be
extracted from plant.
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The most important single act of phytoremediation?

• 6 CO2 6 H2O C6H12O6 6 O2