Phytoremediation Technology for Heavy Metal Removal from the Environment

Abstract

Anthropogenic activities, industrialization, and urbanization have contributed extensively to the enhanced pollution levels in the
environment. Along with soil and water pollution, air pollution is also escalating and contamination with heavy metals (HMs) is
dangerous for the environment since it has negative impacts on people, animals, plants, and the ecosystem. HMs derive their origin from natural and anthropogenic sources. Commercial activities like processing of metals, mining, automobiles, geothermal energy plants, manufacturing industries, tanning, dyeing and plating are the sources of HM contamination. The non biodegradable, permanent inorganic chemical components recognized as HMs are typically harmful at small doses even in humans. HM toxicity leads to carcinogenic effects, developmental and reproductive damage, cardiovascular ailments, haematological, respiratory and nervous system disorders, inflammation and gastrointestinal troubles etc. The absorption and accretion of these metals cause oxidative stress and molecular damage, cytotoxic and mutagenic effects, growth reduction and physiological disorder in plants. Therefore considering their toxic effects, various mechanical as well as physio-chemical technologies are employed for metal removal from the air, water and soil but these techniques have their own limitations and environmental consequences. Hence, phytoremediation is considered an innovative, potentially promising technology employing majorly green plants. The various phytoremediation techniques involve phytoextraction, phytostabilization, phytodegradation, phytotransformation, phytovolitization, and rhizofiltration. Employing these techniques, plants can remove contaminants through a variety of processes, including adsorption, absorption, transport and translocation, hyper-accumulation, transformation, and mineralization. While phytoremediation of air pollutants is still an emerging technology, assimilation properties of plants to convert a toxicant into non-toxic forms have been used extensively for phytoremediation of air. Plants like Morus alba and Eucalyptus globulus can efficiently remove metallic pollutants from air. Moreover, aquatic macrophytes like Eichhornia crassipes,
Spirodela polyrhiza, Pistia stratiotes, Azolla, Lemna minor, and Salvinia herzogii are potentially used for cleanup of the HMs in water, while Brassica juncea, Thlaspi caerulescens, Jatropha curcas, Pteris vittata, Vetiveria zizanioides, Gentiana pennelliana, Ambrossia artemisifolia etc. display tremendous well known phytoremediation activity in soil. Phytoremediation is an innovative, aesthetically pleasing, nonintrusive, sustainable and cost-effective technology. Furthermore, due to the disadvantages like high maintenance cost, extensive labor requirement and risks involved in existing conventional technologies associated with pollution abatement, phytoremediation technique can act as a potential, cost-effective and efficient method for water, soil as well as air pollution control.