Phytoremediation

In News

• Scientists have planned to use hyperaccumulator plants to remove toxic metals from soil using the phytoremediation process.
  • Toxic heavy metals are absorbed by plants from where they make their way into our food chain thus affecting human life along with ecology.

What is Phytoremediation?

• About:
  • Phytoremediation is a bioremediation process that uses living organisms like plants, microalgae and seaweeds to remove toxic heavy metals from the soil.
  • It is a sustainable and eco-friendly technology compared to other technologies used in removing toxicity from the soil.
  • The process can be used for faster removal of toxicity using hyperaccumulator plants that absorb these substances from the soil in greater amounts. 
• Hyperaccumulator plants:
  • Hyperaccumulator plants are those that have an unusual ability to absorb hundreds or thousands of times greater amounts of toxic substances from the soil compared to other plants.
  • They can remove metals like silver, cadmium, cobalt, chromium, copper, mercury, manganese, molybdenum, nickel, lead and zinc; metalloids such as arsenic and selenium; some radionuclides; and non-metallic components such as boron. 
  • However, they cannot remove organic pollutants from the ground due to metabolic breakdown.
  • These hyperaccumulator species naturally occur in many parts of the world including the Mediterranean region, tropical South America.

Advantages of phytoremediation with hyperaccumulators

• It is cost-effective compared with other remediation methods. 
• The method is simple and doesn’t require any new kinds of specialised technology. 
• No external energy source is required.
• It enriches the soil with organic substances and microorganisms.
• Protect the soil from erosion due to wind and water.

Disadvantages of phytoremediation with hyperaccumulators

• It is a very slow and time-consuming process.  
• Large economic cost due to the inability to grow crops on the remediation land.
• Hyperaccumulator plants chosen to conduct the rehabilitation could act as invasive species, growing out of control and disturbing the fragile ecological balance.

Different types of Phytoremediation Processes

• Rhizosphere biodegradation: The process includes plants releasing natural substances through their roots, supplying nutrients to microorganisms in the soil. The microorganisms enhance biological degradation.
• Phyto-stabilization: In this process, chemical compounds produced by the plant immobilise contaminants, rather than degrade them.
• Phyto-extraction: In this process, plant roots absorb the contaminants along with other nutrients and water. The contaminant mass is not destroyed but ends up in the plant shoots and leaves. 
• Rhizofiltration: The process is similar to phyto-accumulation but the plants used for cleanup are raised in greenhouses with their roots in water. Phyto-volatilization: In this process, plants take up water containing organic contaminants and release the contaminants into the air through their leaves.
• Phyto-degradation: In this process, plants actually metabolize and destroy contaminants within plant tissues.
• Hydraulic Control: Plant indirectly remediate by controlling groundwater movement. They act like natural pumps wherein their roots establish a dense root mass that takes up large quantities of water.  

Source: IE