Phytoremediation technologies

1. Maylowen C. Pescador

2. Phytoremediation
 Refers to the use of plants and associated microbes to
reduce the concentrations or toxic effects of
contaminants in the environment.
 Widely accepted as a cost-effective environmental
restoration technology.
 Contaminants
 Organic: petroleum hydrocarbons, gas condensates,
crude oil, chlorinated compounds, pesticides, and
explosive s
 Inorganic: metals, metalloids, radioactive materials

3. Phytoremediation Technologies
 Phytostabilization
 Phytodegradation
 Phytovolatilization
 Phytoextraction

4. Phytostabilization
 Aims to immobilize contaminants in the soil and
prevent further dispersal.
 Revegetation in mine tailings using metal tolerant
grasses such as Festuca rubra, Agrostis tenius

5. Mechanisms of Phytostabilization:
1. Phytochemical complexation in the rhizosphere
 Natural chelates (ex. Amino acids) of roots can
form complex with metals

6. 2. Transport protein inhibition on the root membrane -
adsorption
3. Storage in the root cells - absorption

8. Site Contaminants Plants Performance
1 acre test plot
Abandoned
smelter,
Barren land
Pb, Zn, Cd
(at 20,000 ppm)
Poplars 50% survival after 3
years; site successfully
revegetated
1 acre test plot
Mine wastes
As, Cd Poplars 5% survival; inclement
weather, toxicity
caused die-off

9. Limitations
 Phytostabilization is useful at sites with shallow
contamination and where contamination is relatively
low. Plants that accumulate heavy metals in the roots
and in the root zone typically are effective at depths of
up to 24 inches. Metals that are readily translocated to
leaves in plants may limit the applicability of
phytostabilization due to potential affects to the food
chain.

10. Phytodegradation
 Refers to the uptake of
contaminants with the
subsequent breakdown,
mineralization, or
metabolization by the plant
itself through various
internal enzymatic reactions
and metabolic processes.
 Remediate some organic
contaminants, such as
chlorinated solvents,
herbicides, and munitions

11. Plant Enzymes
 Oxygenases have been identified in plants that are able
to address hydrocarbons such as aliphatic and
aromatic compounds.
 Nitroreductases are produced in some plants that can
reduce and breakdown compounds such as the
explosives TNT, RDX and HMX.
 Other enzymes include dehalogenase, peroxidase,
laccase, and nitrilase

12. Contaminants
 Ethylene dibromide (EDB)
 Additive to leaded gasoline
 Metabolized by Leuceana leucocephala
 Benzotriazoles
 Used in photographic emulsions, as anti-tarnish
 Metabolized by Helianthus annuuss
 Trinitrotoluene (TNT)
 One of the world’s most dangerous explosives
 Metabolized by vetiver grass

13. Trinitrotoluene (TNT)
 Entereo cloaca can utilize ester explosive as its source of
nitrogen
 It can produce enzymes pentaerythritol tetranitrate
(PETN) reductase and nitroreductase
 The genes expressing the production of these enzymes
are introduced in tobacco plant (Nicotiana tabacum)

14. Biodegradation of TNT by the enzyme reductase

17. Phytovolatilization
 This involves the use of plants to take up contaminants
from the soil, transforming them into volatile forms
and transpiring them into the atmosphere
 Uptake of organic contaminant such as
Trichloroethylene (TCE) by poplar trees

18. v Tobacco carries the bacterial detoxification genes
merB and merA
 merB encodes for organomercurial lyase that catalyzes
mercury bond (Hg-C bond), removing the organic
ligand and releasing Hg(II)
 merA encodes for mercuric ion reductase that reduces
ionic mercury Hg(II) to Hg(0) using NADPH

19. Phytoextraction
 use plants to absorb, translocate and store toxic
contaminants from a soil matrix into their root and
shoot tissue.
 Involves repeated harvesting of the biomass
 Uses metal hyperaccumulating plants or fast growing
plants such as T. caerulescens

20.  Mechanism of Metal
Accumulation

21. Summary
Technology Action in
Contaminants
Main Type of
Contaminants
Vegetation
Phytostabilization Retained in situ Organics and
metals
Cover maintained
Phytodegradation Attenuated in situ Organics Cover maintained
Phytovolatilization Removed Organics and
metals
Cover maintained
Phytoextraction Removed Metals Harvested
repeatedly

22. Plant Chemicals
Arabidopsis Mercury
Bladder campion Zinc, Cupper
Brassica family (Mustard & Broccoli) Selenium, Sulfur, Lead, Chromium,
Nickel, Zinc, Copper, Cesium,
Strontium
Compositae family Cesium, Strontium
Euphorbiaceae Nickel
Tomato Lead, Zinc, Copper
Poplar trees Pesticides, Atrazine, Tricholoethylen
(TCE), Carbon tetrachloride,
Nitrogen compounds, TNT, RDX
Sunflower Cesium, Strontium, Uranium

23. Aberdeen Proving Ground, Maryland