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| Last Updated:: 12/10/2017

Phytoremediation - Use of Green Plants to Remove Pollutants

Climate Change
Source:http://rydberg.biology.colostate.edu/Phytoremediation/2008%20websites/
BZ572_Radionuclides%20website_Tom%20Grant/UGA_phyto_fig.jpg
Phytoremediation is defined as the use of green plants to remove pollutants from the environment or render them harmless. This cost-effective plant-based approach to remediation takes advantage of the remarkable ability of plants to concentrate elements and compounds from the environment and to metabolize various molecules in their tissues. Toxic heavy metals and organic pollutants are the major targets for phytoremediation. Phyto-(or green-plant based-) remediation is not a new concept. About 300 years ago, plants were proposed for use in the treatment of wastewater. Thlaspi caerulescens and Viola calaminaria were the first plant species documented to accumulate high levels of metals in leaves.
Phytoremediation can be divided into the following areas:
Climate Change
  • Phytoextraction: In this process, pollutant-accumulating plants are used to remove metals or organics from soils by concentrating them in the harvestable parts.
  • Phytodegradation: This  is  the  use  of  plats  and  associated  microorganisms  to  degrade  organic  pollutants, including  ammunition  wastes (e.g.  TNT  and  GTN),  polychlorinated  phenols  (PCBs),  and  tricholoethylene (TCE). Successful phytodegradation requires organic contaminants to be biologically available for absorption to, or uptake and metabolism by, plant or plant-associated microbial systems. Bioavailability depends on the relative lipophilcity of the compound, the soil type, and the age of the contaminant.
  • Rhizofilteration: This is the use  of  plant  roots  to absorb and adsorb pollutants, mainly metals, from water and aqueous  waste  streams.  An  ideal plant for rhizofilteration should have rapidly growing roots with the ability to remove toxic metals from solution over extended  periods of  time. A  number of  plants  such  as Indian mustard (Brassica juncea), rye, corn, sunflower have an intrinsic  ability  to  absorb  and  precipitate  having  metals from solution.
  • Phytostabilization: This  is  the  use  of  plants  to  reduce  the  bioavailability of pollutants  in  the environment. Heavy metal polluted soils usually lack established vegetation cover due to the toxic effects of pollutants. Barren soils are more prone to erosion and leaching which spread pollutants in the environment.
  • Phytovolatilization: This is the use of  plants  to  volatilize  pollutants. Phytovolatilization  of  metals  may have unique advantages over phytoextraction, because it bypasses harvesting and disposal of metal rich biomass.
Advantages of Phytoremediation:
Plants are solar-driven pumping and filtering systems that have measurable loading, degrading and fouling capacities. Similarly, root may be described as exploratory, liquid-phase extractors that can find, alter and/or translocate elements and compounds against large chemical gradients. Therefore, plants can also be a cost-effective alternative to physical remediation systems.
Limits of Phytoremediation:
As plants are alive, their root require oxygen, water and nutrients, soil texture, pH, salinity, pollutants concentrations and the presence of other toxins must be within the limits of plant tolerance. Contaminants that are highly water soluble may leach outside the root zone and require containment. Phytoremediation is also frequently slower than physio-chemical process, may need to be considered as long-term remediation process.
List of some plants used in phytoremediation

Plant

Metal

Method of Phytoremediation

Brassica juncea

Lead

Chelate-assisted phytoextraction

Thlaspi caerulescens

Cadmium

Continuous phytoextraction

Silense vulgaris

Zinc

Continuous phytoextraction

Brassica oleracea

Zinc

Continuous phytoextraction

Raphanus sativus

Cadmium

Continuous phytoextraction

Thlaspi caerulescens

Nickel

Continuous phytoextraction

Alyssum lesbiacum

Copper

Continuous phytoextraction

Alyssum murale

Lead

Continuous phytoextraction

Arabidopsis thaliana

Chromium

Continuous phytoextraction

Brassica juncea

Selenium

Continuous phytoextraction

Ipomea alpine

Copper

Continuous phytoextraction

Haumaniastrum robertii

Cobalt

Continuous phytoextraction

Sebertia acuminate

Nickel

Continuous phytoextraction

Agrotis tenuis

Lead

Phytostabilization

Festuca arundinacea

Boron

Phytovolatilization

Hibiscus cannibus

Boron

Phytovolatilization

Lotus corniculatus

Boron

Phytovolatilization

Astragalus racemosus

Selenium

Phytovolatilization

Helianthus annus

Uranium

Rhizofiltration

Source:http://www.biotecharticles.com/Environmental-Biotechnology-Article/Phytoremediation-Use-of-green-plants-to-remove-pollutants-704.html