I like phytoremediation because it can both help reduce contaminants and also add great beauty to a site.
Phytoremediation refers to the use of plants and other associated soil microbes to reduce the toxic effects of contaminants in the environment. Thus, it can greatly improve the functionality of contaminated soil and reduce the concentrations of harmful toxic elements.
Additionally, phytoremediation is a cost-effective bioremediation process that uses different types of plants to stabilize, transfer, remove, or destroy the contaminants in the groundwater or soil. It consists of several different strategies, out of which four main mechanisms are considered. They are phytoextraction, phytostabilization, phytodegradation and phytovolatilization.
Different Techniques of Phytoremediation
Phytoextraction: This process is also known as phytoaccumulation. In this process, the roots of the plants absorb contaminants, along with water and other nutrients. Therefore, the contaminants end up in the plant shoots and leaves. This process involves repeated harvesting of the biomass so as to lower the concentration of toxic elements in the soil.
Through research, it has been found that phytoextraction helps in effective removal of contaminants, mainly metals. Phytoextraction is either an induced process (the use of chemicals to increase the bioavailability of metals) or a continuous process (the use of fast-growing plants or metal hyperaccumulating plants).
Phytostabilization: This is the process where the plants produce certain kinds of chemicals to immobilize the contaminants, instead of degrading them. In other words, phytostabilization retain contaminants in the soil and restrict its further dispersal. Contaminants can be stabilized within the rhizosphere or in the roots. Through phytostabilization, the action on contaminants has been found to be retained in situ, and this process is mainly used for contaminants like organics and metals.
Phytodegradation: Phytodegradation is the process of releasing enzymes from the plant roots so as to degrade the organic contaminants directly. Degradation is also done through metabolic activities within plants' tissues. In this process, the plants metabolize the organic contaminants in their tissues and convert them to less toxic substances. It is found that this process works extremely well in cases of hydrophobic organic contaminants. Through phytodegradation, the action on contaminants has been found to be attenuated in situ, and this process is mainly used for organic contaminants.
Rhizodegradation is another process where organic contaminants are attenuated into less toxic substances through biodegradation of soil microbes. The plant roots release root exudates and enzymes into the rhizosphere, which stimulates the functional and the structural diversity of microbial communities in the rhizosphere.
Phytovolatilization: Some plants are capable of transforming contaminants into volatile compounds. This process is known as phytovolatilization, where plants take up water containing organic contaminants that are then released into the air through their leaves.
First, the contaminants are taken up by the plant roots, converted into gaseous form and finally released into the atmosphere. This process is driven by evapotranspiration of plants. For this reason, the plants that have high rates of evapotranspiration are usually selected for phytovolatilization. This process helps in removing contaminants like organics and metals.
The 5 Best Plants for Phytoremediation
Here is a list of five of the best plants that can be used for phytoremediation.
- Indian mustard: Brassicaceae species are known for their ability to accumulate certain metals while also producing high quantities of biomass. Indian mustard is considered to be one of the best plants of this group, which can remove several metallic contaminants from the soil. It has been found to effectively reduce the concentrations of Cd, Pb, Se, Zn, Hg, and Cu. Many are unaware of the fact that Indian mustard has also removed radioactive Cs 137 from Chernobyl in the 1980s as well.
- Willow: In addition to beautifying landscapes, these water-loving plants are used for phytoremediation processes as well. Their roots are capable of accumulating lower levels of heavy metals like Cd, Ni, Pb, etc. and work even in mixed heavy metals like diesel fuel polluted areas.
- Poplar tree: The effectiveness of these trees in reducing contaminants has been widely studied. It has been found that poplar trees greatly reduce organic pollutants, mostly chlorinated solvents. Their secret lies in the well-designed root system, which takes up large quantities of water.
- Indian grass: Native to the Midwestern U.S., these plants benefit the soil and ground water around them. They help in detoxifying agro-chemical residues such as herbicides and pesticides. Indian grass belongs to the Gramineae family, which also includes other grasses like common buffalo grass, western wheatgrass, etc. They help to remediate petroleum hydrocarbons as well.
- Sunflower: Experiments have revealed that sunflowers can accumulate a varied range of contaminants. It is also revealed that sunflowers reduce different PAH levels from soil in an effective way.
Advantages and Disadvantages of Phytoremediation
Phytoremediation is a cost-effective process, as it does not involve the use of huge equipments. Also, planting trees in the remediation sites is appealing to the eyes and can add to a beautiful aesthetic. Plus, growing plants does not require much effort and can be monitored easily.
But the process has some limitations as well. The contaminating material should always be present within the root zone of the plants to make it accessible to the roots. Also, phytoremediation is a slow process and a contaminated site needs to be large enough to grow enough plants.
References and Recommended Reading
- Greipsson, S. (2011) Phytoremediation. Nature Education Knowledge 3(10):7
- Phytoremediation: A Promising Approach for Revegetation of Heavy Metal-Polluted Land
- 2012 Plant Talk 15 Plants for Phytoremediation
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.
Ankita B (author) on August 27, 2020:
Thank you so much Vandna. Your kind comments are appreciated always.
thoughtsprocess from Navsari (India) on August 27, 2020:
Thank you so much for sharing this informative article with us.
Ankita B (author) on August 22, 2020:
Thank you so much Bambe for your kind comments. Yes we should all be aware of this wonderful process. I am delighted that you liked reading this.
Bambe from Philippines on August 22, 2020:
This is a wonderful article. This will give awareness especially today's generation. Natural ways are still the best. Thumbs up for this.
Ankita B (author) on August 22, 2020:
Thank you so much FlourishAnyway for reading and commenting. Yes it is indeed impressive. I appreciate your lovely comments.
FlourishAnyway from USA on August 22, 2020:
It’s impressive how plants can help heal the earth. I love willows and sunflowers. To know that they are capable of this makes me love them more.
Ankita B (author) on August 21, 2020:
iPhone from New York, USA on August 21, 2020:
Ankita B (author) on August 21, 2020:
Thank you Danny for your kind comments. I am glad you enjoyed reading this article.
Danny from India on August 21, 2020:
Very nice article Ankita, very well explained. I love mangrove habitats. The place I stay is close to one such groove.