Phytoremediation
Phytoremediation is the usage of higher plants for the cost-effective and environmentally friendly remediation of toxic metals and chemical molecules contaminated soil and groundwater.
It is an eco-friendly approach that mitigates &revegetate heavy metal-polluted medium in a cost-effective way.
It is a promising approach that relies on the usage of hyper-accumulator plant species that can withstand high levels of harmful Heavy Metals in the environment.
Phytoremediation of soil
Metals contaminated soil degrades the plants growth as well as effecting the surroundings.
When employing plants to extract metals from contaminated soils, natural metal hyperaccumulator trait is far more essential than high-yield capabilities.
Soil contaminated with Lead (Pb) and Chromium (Cr6+) may be inactivated in the soil by plants and soil amendments (phytostabilization).
a. Phytostabilization involves the reduction of the mobility of heavy metals in soil.
Species of genera Haumaniastrum, Eragrostis, Ascolepis, Gladiolus and Alyssum are examples of plants cultivated for this purpose.
Arabidopsis and yeast uptake Iron (Fe), Cadmium (Cd) and Zinc (Zn).
b. Phytodegradation (Phytotransformation): Contaminants, organic or inorganic, are incorporated into the lignin of the cell wall of roots cells or into humus.
Populus species and Myriophyllium spicatum are examples of plants that have these enzymatic systems.
c. Phytovolatilization: This method is based on plants' ability to absorb and volatilize particular metals/metalloids.
Astragalus bisulcatus and Stanleya pinnata for Selenium (se) or transgenic plants (with bacterial genes) of Arabidopsis thaliana, Nicotiana tabacum, Liriodendron tulipifera or Brassica napus for Mercury (Hg) are major plants for phytovolatization.
d. Phytoextraction; This involves pollutants being absorbed by roots, then being translocated and accumulated in the aerial sections.
It is most commonly employed with metals (Cd, Ni, Cu, Zn, Pb), but it can also be used with other elements (Se, As), as well as organic molecules.
Elsholtzia splendens, Alyssum bertolonii, Thlaspi caerulescens and Pteris vittata are known examples of hyperaccumulator plants for Cu, Ni, Zn/Cd and As, respectively.
e. Phytofiltration: Through their root system or other submerged organs, plants absorb, concentrate, and/or precipitate pollutants, notably heavy metals or radioactive materials, from an aquatic medium.
Examples include Helianthus annus, Brassica juncea, Phragmites australis, Fontinalis antipyretica and several species of Salix, Populus, Lemna & Callitriche.
f. Rhizodegradation: In this method, growing roots promote the proliferation of degrading rhizosphere microorganisms which utilize exudates and metabolites of plants as a source of carbon and energy.
g. Constructed wetlands: It is the treatment systems that use natural processes involving wetland vegetation, soils, and their associated microbial assemblages to improve water quality.
It is frequently used to treat home, agricultural, and industrial waste water, but it has also proven to be effective in the treatment of acid mine drainage.
h. Phytodesalination: It is the method to enhance the productivity of soil and vegetation cover, salt-resistant plants are grown on salt-affected soil.
Example Suaeda maritima and Sesuvium portulacastrum in removal and accumulation of NaCl, from highly saline soils.
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