A recent article in The Guardian analyzes the potential of a method to mitigate pollution called phytoremediation - using plants to eliminate and contain contaminants from the soil, air and water supply. Phytoremediation is a form of bioremediation, the name for processes that use microorganisms and their enzymes to fight pollution.
Technically, phytoremediation is not a new method, since human beings have used plants to purify water sources for over 3000 years. Recently, however, phytoremediation is gaining popularity as an effective and ecological way to remove pesticides and heavy metals from soil, runoff water, and waste water.
How Phytoremediation Works
The basic principal of phytoremediation involves using the microorganisms of many different types of plants, including grass, reeds, bamboo, irises, maize, sorghum, willow, and poplar, to contain or break down pollution. In practice, phytoremediation is a broad term for several different processes, which can roughly be divided into two groups: active and passive. Forms of passive phytoremediation include:
- Phytorecultivation and phytostabilization--planting vegetation that will sequester pollutants in the plants' roots and prevent the spread of contaminants in the ecosystem; examples include planting a thick layer of ground vegetation to prevent leaching and reduce the risk of pollutants being released into the atmosphere.
- Phytoregeneration--creating soil that is rich is microorganisms and organic matter so as to neutralize pollutants and promote healthy vegetation that will further strengthen the ecosystem and counteract pollutants.
Active phytoremediation solutions include:
- phytoextraction--in which contaminants are broken down and removed from the soil by microorganisms in the plants' roots. The plants absorb contaminants in their root systems and either store them there or transport them to the stem and leaves. The plants, known as hyperaccumulators, are then harvested and disposed of.
- rhizofiltration--water is filtered through a plant's root system to remove pollutants, which remain absorbed in the roots.
Advantages and Disadvantages of Phytoremediation
Although phytoremediation is not yet being implemented on a wide scale, it is being seen as an increasingly viable method of removing pollutants. Thierry Jacquet, CEO of the French company Phytostore--France's market leader in phytoremediation, says that " [Plants] represent an economically competitive solution," Indeed, phytoremediation is considerably less expensive and less invasive, as well as more aesthetically pleasing, than other forms of pollution extraction, because it requires the same supplies and tools used in agriculture. Moreover, phytoremediation can be used to treat sites contaminated by several different pollutants.
Jacquet admits, however, that phytoremediation has not been fully embraced by French industries, which may be due in part to the drawbacks and limitations of the process. Phytoremediation is far more time consuming than other methods, and largely dependent upon the growing conditions for the plants involved. Furthermore, plants used to remove pollutants may be harmful to animals if ingested, causing pollutants to spread throughout the food chain. However, despite its imperfections, phytoremediation is an innovative approach to fighting pollution that is likely to become both more widespread and more refined as the biotech field develops.
Sadie Nachtigal - Sadie Nachtigal is a Paris-based teacher and writer. She graduated with High Honors from Oberlin College, where she studied Comparative ...
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