13.1 Introduction
Recent year with the growing industrialization and urbanization lead to the growing
population and their growing demands causes heavy environmental degradation on a
very large scale. These deforestation causes soil erosion and heavy use of pesticides
causes degradation of soil and the quality of water. Use of pesticides in agricultural
field causes risk of heavy metal contamination. These metals are elements with
metallic properties and an atomic number > 20. The most common heavy metal
contaminants are Cd, Cr, Cu, Hg, Pb, and Zn. Metals are natural components present
in soil. Some of these metals are micronutrients necessary for plant growth such as
Zn, Cu, Mn, Ni, and Co, while others have unknown biological function such as Cd,
Pb, and Hg. Metal pollution has harmful effect on biological systems and does not
undergo biodegradation. Toxic heavy metals such as Pb, Co, Cd can be
differentiated from other pollutants. They cannot be biodegraded but can be
accumulated in living organisms and causes various diseases and disorders even in
relatively lower concentrations. Heavy metals with soil residence times of thousands
of years, pose numerous health effects to higher organisms. They are also known to
have effect on plant growth, ground cover and have a negative impact on soil
microflora. It is well known that heavy metals cannot be chemically degraded and
need to be physically removed or be transformed into nontoxic compounds.
Environmental cleanup includes removal of heavy metals and other toxic
contaminants from the environment and the process is called remediation. Hence,
it is necessary to remove heavy metals from the soil, water, and wastewater. Several
methods have been adopted for removal of metals, but most of them are costly and
difficult to get optimum results. There is need of some immediate solution which is
environment friendly and cost-effective because modern/ synthetic technologies are
not so much effective to the remedies of contaminated soil and water. Therefore, in
recent year, phytoremediation and nanoremediation techniques were used as environment friendly and cost-effective techniques to treat the pollutants that are present
in soil and water even in nano size.
13.1.1 Phytoremediation
Phytoremediation is a modern technology which means removal of toxic metals
using plants. It exploits the ability of some plants to remove, absorb, accumulate,
metabolize, volatilize, or stabilize and concentrate pollutants like organic and inorganic that is present in soil, sludge, industrial streams, and sediments. These
compounds represent a threat to living beings so a series of methods have been
developed to amend the impact caused. Conventional methods are usually expensive
and can irreversibly affect the properties of soil, water, and the living beings
(Padmavathiamma and Li 2007). The increase in costs and the limited effectiveness
of physico-chemical treatments have stimulated the development of new
technologies. Therefore, phytoremediation represents a sustainable and low-cost
alternative and effective for the rehabilitation of environments affected by natural
282
P. Kumar et al.
Recent year with the growing industrialization and urbanization lead to the growing
population and their growing demands causes heavy environmental degradation on a
very large scale. These deforestation causes soil erosion and heavy use of pesticides
causes degradation of soil and the quality of water. Use of pesticides in agricultural
field causes risk of heavy metal contamination. These metals are elements with
metallic properties and an atomic number > 20. The most common heavy metal
contaminants are Cd, Cr, Cu, Hg, Pb, and Zn. Metals are natural components present
in soil. Some of these metals are micronutrients necessary for plant growth such as
Zn, Cu, Mn, Ni, and Co, while others have unknown biological function such as Cd,
Pb, and Hg. Metal pollution has harmful effect on biological systems and does not
undergo biodegradation. Toxic heavy metals such as Pb, Co, Cd can be
differentiated from other pollutants. They cannot be biodegraded but can be
accumulated in living organisms and causes various diseases and disorders even in
relatively lower concentrations. Heavy metals with soil residence times of thousands
of years, pose numerous health effects to higher organisms. They are also known to
have effect on plant growth, ground cover and have a negative impact on soil
microflora. It is well known that heavy metals cannot be chemically degraded and
need to be physically removed or be transformed into nontoxic compounds.
Environmental cleanup includes removal of heavy metals and other toxic
contaminants from the environment and the process is called remediation. Hence,
it is necessary to remove heavy metals from the soil, water, and wastewater. Several
methods have been adopted for removal of metals, but most of them are costly and
difficult to get optimum results. There is need of some immediate solution which is
environment friendly and cost-effective because modern/ synthetic technologies are
not so much effective to the remedies of contaminated soil and water. Therefore, in
recent year, phytoremediation and nanoremediation techniques were used as environment friendly and cost-effective techniques to treat the pollutants that are present
in soil and water even in nano size.
13.1.1 Phytoremediation
Phytoremediation is a modern technology which means removal of toxic metals
using plants. It exploits the ability of some plants to remove, absorb, accumulate,
metabolize, volatilize, or stabilize and concentrate pollutants like organic and inorganic that is present in soil, sludge, industrial streams, and sediments. These
compounds represent a threat to living beings so a series of methods have been
developed to amend the impact caused. Conventional methods are usually expensive
and can irreversibly affect the properties of soil, water, and the living beings
(Padmavathiamma and Li 2007). The increase in costs and the limited effectiveness
of physico-chemical treatments have stimulated the development of new
technologies. Therefore, phytoremediation represents a sustainable and low-cost
alternative and effective for the rehabilitation of environments affected by natural
282
P. Kumar et al.