2003). This technology has cumulated increased scientific and commercial interest
as it is environmentally compatible and less expensive contaminated site remediation
method in comparison to other engineering-based methods such as excavation, soil
washing, or soil incineration (Clayton 2007). Below are described the various
phytoremediation technologies.
6.1 Phytodegradation
Phytodegradation or phyto-transformation is a process of reduction of contaminants
through metabolic processes occurring in the plant or effect of compounds called
enzymes released by the plants. In this the complex organic pollutants are
disintegrated into simpler molecules and are incorporated into the plant tissues to
aid in faster plant growth (Fig. 11.8). The enzymes present in plants catalyze and
accelerate the chemical reactions, with some involved in conversion of ammunition
wastes, few in degradation chlorinated solvents such as trichloroethylene (TCE), and
others causing herbicide degradation.
6.2 Phytoextraction
This process relies on the plants that accumulate metals and transport them into the
harvestable aboveground shoots (Salt et al. 1998; Vassil et al. 1998). The plant
material finds subsequent use as nonfood (e.g., wood, cardboard) or ash, followed by
landfill disposal or recycled in case of valuable metals called phytomining (Chaney
et al. 1997). The species mainly used for phytoextraction are Indian mustard and
sunflower as they grow faster with high biomass, high salt tolerance, and accumulation of metals (Blaylock and Huang 2000; Salt et al. 1995). It is considered a low
impact technology and beneficial for environment. Furthermore, there is reduction in
leaching and erosion as plants cover the soil. The amount of contaminants can be
reduced in soil with successive cropping and harvesting (Vandenhove et al. 2001).
6.3 Phytostabilization
Phytostabilization, also imputed as in-place inactivation, is basically used to remediate soil, sediment, and sludge (United States Environmental Protection Agency
2000). In this method plant roots reduce the mobility of contaminant and its
bioavailability in the soil. It focuses mainly to (1) decrease the water percolation
through the soil matrix that otherwise may form hazardous leachate, (2) act as a
barrier to avoid direct contact with the contaminated soil, and (3) check soil erosion
and the toxic metal distribution to other nearby areas (Raskin and Ensley 2000). The
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as it is environmentally compatible and less expensive contaminated site remediation
method in comparison to other engineering-based methods such as excavation, soil
washing, or soil incineration (Clayton 2007). Below are described the various
phytoremediation technologies.
6.1 Phytodegradation
Phytodegradation or phyto-transformation is a process of reduction of contaminants
through metabolic processes occurring in the plant or effect of compounds called
enzymes released by the plants. In this the complex organic pollutants are
disintegrated into simpler molecules and are incorporated into the plant tissues to
aid in faster plant growth (Fig. 11.8). The enzymes present in plants catalyze and
accelerate the chemical reactions, with some involved in conversion of ammunition
wastes, few in degradation chlorinated solvents such as trichloroethylene (TCE), and
others causing herbicide degradation.
6.2 Phytoextraction
This process relies on the plants that accumulate metals and transport them into the
harvestable aboveground shoots (Salt et al. 1998; Vassil et al. 1998). The plant
material finds subsequent use as nonfood (e.g., wood, cardboard) or ash, followed by
landfill disposal or recycled in case of valuable metals called phytomining (Chaney
et al. 1997). The species mainly used for phytoextraction are Indian mustard and
sunflower as they grow faster with high biomass, high salt tolerance, and accumulation of metals (Blaylock and Huang 2000; Salt et al. 1995). It is considered a low
impact technology and beneficial for environment. Furthermore, there is reduction in
leaching and erosion as plants cover the soil. The amount of contaminants can be
reduced in soil with successive cropping and harvesting (Vandenhove et al. 2001).
6.3 Phytostabilization
Phytostabilization, also imputed as in-place inactivation, is basically used to remediate soil, sediment, and sludge (United States Environmental Protection Agency
2000). In this method plant roots reduce the mobility of contaminant and its
bioavailability in the soil. It focuses mainly to (1) decrease the water percolation
through the soil matrix that otherwise may form hazardous leachate, (2) act as a
barrier to avoid direct contact with the contaminated soil, and (3) check soil erosion
and the toxic metal distribution to other nearby areas (Raskin and Ensley 2000). The
276
M. Rastogi and M. Nandal