Page 9 - OSMERT-2 Module 6 (inside pages) final
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PHYTOREMEDIATION

               Although the application of microbe biotechnology has been successful with petroleum-based
               constituents, microbial digestion has met limited success for widespread residual organic and
               metals pollutants. Vegetation-  based remediation shows potential for accumulating,
               immobilizing, and transforming a low level of persistent contaminants. In natural ecosystems,
               plants act as filters and metabolize substances  generated by nature. Phytoremediation is an
               emerging technology that uses plants to remove contaminants from soil and water. The term
               “phytoremediation” is relatively new,  coined in 1991. Its potential  for encouraging the
               biodegradation of organic contaminants requires further research, although it may be a
               promising area for the future. We can find five types of phytoremediation techniques, classified
               based on the contaminant fate. These are: phytoextraction, phytotransformation,
               phytostabilization, phytodegradation and rhizofiltration, even a combination  of  these can be
               found in nature.

               Phytoextraction  or  phytoaccumulationis the process used by the plants to accumulate
               contaminants into the roots and aboveground shoots or leaves. This technique saves
               tremendous remediation cost by accumulating low levels of contaminants from a widespread
               area. Unlike the  degradation mechanisms, this process produces a mass of plants and
               contaminants (usually metals) that can be transported for disposal or recycling.

               Phytotransformationrefers to the uptake of organic contaminants from soil, sediments, or water
               and, subsequently, their transformation to more stable, less toxic, or less mobile form. Metal
               chromium can be reduced from hexavalent to trivalent chromium, which is a less mobile
               andnoncarcinogenic form.

               Phytostabilization  is a technique in which plants reduce the  mobility and migration  of
               contaminated soil. Leachable constituents are adsorbed and bound into the plant structure so
               that they form a stable mass of plant from which the contaminants will not  reenter the
               environment.

               Phytodegradationor  rhizodegradation  is the breakdown of contaminants through the activity
               existing in the rhizosphere. This activity is due to the presence  of proteins and enzymes
               produced by the plants or by soil organisms such as bacteria, yeast, and fungi. Rhizodegradation
               is a symbiotic  relationship that has evolved between plants and microbes. Plants provide
               nutrients necessary  for  the  microbes  to thrive, while microbes provide a healthier soil
               environment.

               Rhizofiltration is a water remediation technique that involves the uptake of contaminants by plant
               roots. Rhizofiltration is used to reduce contamination in natural wetlands and estuary areas.

               Phytoremediation is well suited for use at very large field sites where  other methods of
               remediation are not cost effective or practicable;  at sites with a low concentration  of
               contaminants where only polish treatment is required over long periods of time; and in











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