Phytoremediation is the process of using green plants to treat and control wastes in water and soil. This method is an indispensable part of the new field of ecological engineering.
There are plants capable of extracting necessary nutrients, including metals, from their soil and water environments. Some of them can store large amounts of elements such as copper and lead. These plants are called hyperaccumulators. They are utilized in phytoremediation to accumulate contaminants from the soil and water.
Phytoremediation has numerous advantages over traditional soil and water remediation methods. It is considered environmentally friendly, non-intrusive, and cost-effective. Because of its economic, industrial, and commercial benefits, phytoremediation is becoming an increasingly popular way of soil remediation.
The most common types of phytoremediation are phytoextraction, phytostabilization, rhizofiltration, and phytostimulation.
Phytoremediation is a process that uses plants to remove, transfer, stabilize, and destroy contaminants in soil and sediment. Contaminants may be either organic or inorganic.
Hyperaccumulators are plants that extract necessary nutrients, including metals, from their soil and water environments. Some hyper-extracting species have been reported to store large amounts of certain elements such as copper or lead; however, this is only true for those which do not appear in plant functioning requirements but still end up stored within them due to an ability known as “hyperaccumulation.”
Phytoextraction
This process involves using specialized plant species to accumulate contaminants from the soil. These plants are usually hyperaccumulators of specific heavy metals such as nickel, cadmium, zinc, or lead (this list varies depending on region). Once these plants are harvested, the soil is no longer contaminated.
Phytostabilization
This involves using plant species to “tie up” contaminants in the soil so that they are less mobile and more immobile. Plant roots bind contaminants through bioprecipitation of toxic metals in root cells, where they undergo sequestration. This method typically requires the use of hardy invasive plants in order to be cost-effective in already contaminated soils.
Rhizofiltration
This process involves using plants to intercept groundwater pollutants with their root systems before these contaminants reach aquifers. In addition, the plant’s deep root system provides excellent filtration properties that can effectively remove many types of contaminants such as nitrate, perchlorate, and organic chemicals.
Root systems in plants are highly efficient when filtering contaminants, even when compared with synthetic technologies such as reverse osmosis or ion exchange resins (used for water purification). A root system will process and filter thousands of gallons of water in a single growing season, whereas reverse osmosis and ion exchange methods, by comparison, tend to be only able to filter hundreds of gallons in a year.
Phytotransformation
The ability of plants to change the molecular composition is one way they can create a non-toxic molecule from an already toxic one. In most cases, these transformations do not happen overnight but somewhat over time as long exposure and certain conditions are met, such as light patterns or water availability.
Phytostimulation
Phytostimulation is a unique form of remediation that involves increased biodegradation in the soil.
