128
S. Lakshmana Prabu et al.
3. Detoxification of the metals.
Phytostimulation
Phytostimulation is also named as rhizodegradation. It is a plant assisted degradation
process; pollutants are degraded through microbial activity by rhizosphere which
is present in the plant roots surrounded by soil. Microorganisms (yeast bacteria
and fungai) break down the organic pollutants, certain toxic compounds, fuels and
solvents into harmless simpler compounds and for their nutrition and energy. Root
of the plant release some compounds which are utilized as food and nutrition by
microorganism and contribute for their growth (Ismail 2012; https://www.unep.or.
jp/Ietc/Publications/Freshwater/FMS2/2.asp; Materac et al. 2015; Sri Lakshmi et al.
2017).
Phytovolatilization
In phytovolatilization, pollutants are absorbed by the plant roots from the soil,
transferred to the plant aerial parts, then finally to the leaves. In leaves, through
metabolic activities theses pollutants are converted into gaseous form (volatile) and
then transpired to the atmosphere.
Phytovolatilisation take place in growing trees. Metals like Se and Hg can be are
removed by this phytovolatilisation. The main disadvantage of this process is elimination of metals as volatile compounds into the environment or atmosphere is safe or
not (Ismail 2012; https://www.unep.or.jp/Ietc/Publications/Freshwater/FMS2/2.asp;
Materac et al. 2015; Sri Lakshmi et al. 2017).
Phytofiltration
Phytofiltration is named based on the plant roots (rhizofilteration) or seedlings
(blastofilteration) (Raskin et al. 1997). In Rhizofiltration (rhizo means “root”), plant
roots absorb the pollutants (metals) from the water adjacent to the root zone. This
method is used to remove the contaminants from water rather than soil. In this method,
either contaminated water is collect from the waste site or growing plants hydroponically and relocating into the contaminated water area, where plant roots adsorb the
contaminants from the water. Over a period of time, the roots will be saturated with
the contaminants, then whole plant or roots are collected for disposal. Metal such as
Pb, Cr and Zn can be removed by this method. Factors like metal being removed and
plant metabolism are the two factors affects the phytofiltration (Ismail 2012; https://
www.unep.or.jp/Ietc/Publications/Freshwater/FMS2/2.asp; Materac et al. 2015; Sri
Lakshmi et al. 2017).
Phytostabilization
Phytostabilization is also named as phytorestoration. In this technique contaminants
are immobilized/stabilized either physically by sorption in root surface or chemically
by chemical fixation in the roots of the plant. In addition preventing the vertical
migration of contaminants to the ground water, which reduces food chain process
entry and dispersion through wind or water.
S. Lakshmana Prabu et al.
3. Detoxification of the metals.
Phytostimulation
Phytostimulation is also named as rhizodegradation. It is a plant assisted degradation
process; pollutants are degraded through microbial activity by rhizosphere which
is present in the plant roots surrounded by soil. Microorganisms (yeast bacteria
and fungai) break down the organic pollutants, certain toxic compounds, fuels and
solvents into harmless simpler compounds and for their nutrition and energy. Root
of the plant release some compounds which are utilized as food and nutrition by
microorganism and contribute for their growth (Ismail 2012; https://www.unep.or.
jp/Ietc/Publications/Freshwater/FMS2/2.asp; Materac et al. 2015; Sri Lakshmi et al.
2017).
Phytovolatilization
In phytovolatilization, pollutants are absorbed by the plant roots from the soil,
transferred to the plant aerial parts, then finally to the leaves. In leaves, through
metabolic activities theses pollutants are converted into gaseous form (volatile) and
then transpired to the atmosphere.
Phytovolatilisation take place in growing trees. Metals like Se and Hg can be are
removed by this phytovolatilisation. The main disadvantage of this process is elimination of metals as volatile compounds into the environment or atmosphere is safe or
not (Ismail 2012; https://www.unep.or.jp/Ietc/Publications/Freshwater/FMS2/2.asp;
Materac et al. 2015; Sri Lakshmi et al. 2017).
Phytofiltration
Phytofiltration is named based on the plant roots (rhizofilteration) or seedlings
(blastofilteration) (Raskin et al. 1997). In Rhizofiltration (rhizo means “root”), plant
roots absorb the pollutants (metals) from the water adjacent to the root zone. This
method is used to remove the contaminants from water rather than soil. In this method,
either contaminated water is collect from the waste site or growing plants hydroponically and relocating into the contaminated water area, where plant roots adsorb the
contaminants from the water. Over a period of time, the roots will be saturated with
the contaminants, then whole plant or roots are collected for disposal. Metal such as
Pb, Cr and Zn can be removed by this method. Factors like metal being removed and
plant metabolism are the two factors affects the phytofiltration (Ismail 2012; https://
www.unep.or.jp/Ietc/Publications/Freshwater/FMS2/2.asp; Materac et al. 2015; Sri
Lakshmi et al. 2017).
Phytostabilization
Phytostabilization is also named as phytorestoration. In this technique contaminants
are immobilized/stabilized either physically by sorption in root surface or chemically
by chemical fixation in the roots of the plant. In addition preventing the vertical
migration of contaminants to the ground water, which reduces food chain process
entry and dispersion through wind or water.