Phytoremediation of Toxic Metals in Soils and Wetlands: Concepts and Applications

Abstract

Over centuries, industrial, mining and military activities, agriculture, farming, and waste practices have contaminated soils and wetlands in many countries with high concentrations of toxic metals. In addition to their negative effects on ecosystems and other natural resources, toxic metals pose a great danger to human health. Unlike organic compounds, metals cannot be degraded, and clean-up usually requires their removal. Most of the conventional remedial methods have lost economic favor and public acceptance because they are expensive and cause degradation of soil fertility that subsequently results in adverse impacts on the ecosystem. Conventional methods of environmental remediation do not solve the problem; rather they merely transfer it to future generation. Obviously, there is an urgent need for alternative, cheap, and efficient methods to clean-up sites contaminated with toxic metals.Phytoremediation, a plant-based green technology, is cost effective, environmental friendly, aesthetically pleasing approach for the remediation of toxic metals. Due to its elegance and the extent of contaminated areas, phytoremediation approaches have already received significant scientific and commercial attention. Two approaches have been proposed for the phytoremediation of toxic metals

Microbial and Plant-Assisted Bioremediation of Heavy Metal Polluted Environments: A Review

“…Phytofiltration could be in any of the three forms of rhizofiltration (the use of plant roots), blastofiltration (the use of seedlings) and caulofiltration (the use of excised plant shoots) [ 3 , 123 , 124 ]. It is the cleanup of polluted environments using plant roots or seedlings from aqueous wastes.…”

Case studies and evidence-based approaches to addressing urban soil lead contamination

“…Phytoremediation covers a range of plant-based technologies for use in the remediation of contaminated soils and water (Rahman et al, 2015). Of particular relevance to Pb-contaminated soils are phytoextraction (use of plants to absorb and translocate lead to above ground tissues which are harvested and removed) and phytostabilization (use of plants to stabilize and safely manage Pb in-situ so as to reduce the risk to human health and the environment).…”

“…Phytoextraction utilises standard agricultural approaches to grow 'crops' of plants that are harvested to remove the metals from the soil. For phytoextraction to be effective, a number of criteria need to be met including a combination of high accumulation of Pb in above ground tissues and high biomass to ensure adequate Pb removal from the soil and fast plant growth to reduce the overall remediation time (Rahman et al, 2015;Blaylock, 2000). In most circumstances, multiple crop rotations are required to remove enough metal from the soil to reach acceptable concentrations, therefore phytoextraction can take years to be completed (e.g.…”

“…Nanoparticles are severely limited due to potential toxicity and cost; phytoextraction is questionable because currently there are no known plants that both hyperaccumulate Pb and simultaneously produces large enough amounts biomass to extract lead from soils (Rahman et al, 2016). Maintaining soil moisture in areas contaminated with high soil Pb levels during dry seasons may assist in reducing exposures associated with seasonal soil resuspension, but is limited by water shortages.…”

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“…It is useful factor to chose the proper plant for the purpose of phytoremediation of the contaminated soils. [22,23]. Among the heavy metal ions, Zn is more mobile and available for plant uptake [24], and based on their physiological activities, Fe, Cu, and Zn are essential heavy metals which are micronutrients necessary for physiological and biochemical functions of plant growth, while Cr is non-essential metal which is non-essential for plant growth [25,7].…”