Phytoremediation of Organic Polluted Soil
The increasingly anthropogenic release of toxic contaminants has led to the contamination of organic chemicals, such as phthalic esters (PAEs), Polycyclic Aromatic Hydrocarbons (PAHs), Polybrominated Diphenyl Ethers (PBDEs), Polychlorobiphenyls (PCBs), Petroleum Hydrocarbons (PHC), pesticides, etc. Remediation of organic polluted soils is becoming an increasing challenge worldwide. Phytoremediation is an emerging technology that utilizes plants to clean up organic pollutants and toxic metals in water, sediments, or soils. Phytoremediation has been accepted and utilized widely because it is a cost-effective and environmental friendly green technology with permanently removing the pollutants.
A large number of plant species have been found to be promising candidates for the phytoremediation of organic pollutants. In general there are two approaches for the phytoremediation of organic-polluted soils based on the difference in remediative mechanism. First, organic pollutants can be taken up directly by plants, resulting in the sequestration or degradation of pollutants inside of plants, which is called phytoextraction. Second, organic pollutants can be degraded by plant-secreted enzymes or plant-modified microbial community in rhizosphere, which is called plant-assisted rhizoremediation.
Plant-assisted rhizoremediation refers to the strategy of phytoremediation ex planta. Plant roots not only secrete enzymes degrading organic pollutants, but also improve the degrading ability of microorganisms in rhizosphere. Plant enzymes with the role of degrading organic pollutants have been well reviewed by Gerhardt and Nwoko, respectively. These enzymes include laccase, nitrilase, dehalogenase, nitroreductase, etc. Although many microorganisms are capable of degrading organic compounds, microbial bioremediation approaches suffer a number of limitations for their widespread application. Plants are able to improve the efficiency of microbial bioremediation of organic-polluted soils.
Phytoremediation is emerging as a potential approach for remediating organic-polluted soils. More field application of phytoremediation is much needed. First, the identification of plant species with the ability of hyper accumulating specific organic pollutants will be desired. Second, the understanding of the detailed mechanisms for the degradation of organic pollutants in plants and rhizosphere is essential for improving the efficiency of phytoremedation and avoiding the secondary contamination of the possibly toxic metabolites from the degradation of parent organic pollutants. Third, more quantitative experimental data analyses about the effect of intercropping or plant-microbe interaction on the efficiency of organic phytoremediation are useful for constructing models for the usage of plants in remediating organic-polluted soils. Finally, regulatory requirements, site assessment, and risk evaluation are indispensable for the field application of phytoremediation for organic pollutants.
Journal of Bioremediation & Biodegradation
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