What is phytoremediation?

Phytoremediation is the in situ use of plants and their associated microorganisms to decontaminate a polluted site. In other words, phytoremediation is human influence on natural environmental processes. Contamination of soil or groundwater/effluent can be remediated using plants.

The processes of phytoremediation can be varied depending on the pollutant. Plants react to different contaminates with different mechanisms. The processes for the phytoremediation of organic pollutants, petroleum hydrocarbons in particular, are primarily phytodegradation and phytostimulation. Phytovolatilization and phytostabilization may also be involved.

Phytodegradation:

A Citizen's Guide to Phytoremediation, 1998.
The pollutant is metabolized, or broken down by the plant into products that are generally less toxic and less persistent in the environment. The plant then incorporates these products into new tissue.
 
Phytostimulation:

A Citizen's Guide to Bioremediation, 1996.
The plant provides root exudates, of carbon, sugars, enzymes, and nutrients, into the rhizosphere which in turn support a large number of microbes. The microbes then degrade the pollutant into carbon dioxide and water. This plant enhanced degradation by the microbes is known as the rhizosphere effect. (See How does phytoremediation work?)
 

Phytovolatilization is a process similar to phytodegradation. The contaminant is broken down into products which are then volatilized through the leaf tissue into the air. There may be some concern, depending on pollutant, what effects these degradation products may have on the environment. Extensive studies should be conducted to determine the degradation products which will be volatilized and their effect on humans and wildlife before undertaking a phytovolatilization project.

Phytostabilization uses plants to stabilize the soil and the contaminant. The pollutant is sorbed to the root tissue and therefore unable to move through the soil or into the groundwater.

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