Keywords Hyperaccumulators, Phytoremediation, Plants, Soil remediation
1 Introduction
1.1 Environmental Toxins and Contaminants
For a functional and a balanced ecosystem, the protection of the environment is a
chief factor. Huge number of environmental toxins and pollutants can lead to highlevel degradation impact on the ecosystem, especially soil [1]. About 25% of the
global soil is reported to be highly degraded and 44% to be significantly degraded.
Various anthropogenic and natural causes lead to degradation of the soil quality by
both the organic and inorganic pollutants [2]. Human activities in metalliferous
mining, smelting, sewage sludge treatment, agricultural fertilizers, military training
and warfare, landfills, electronic industries, electroplating, energy and fuel production [3], etc. lead to an ineluctable release of the pollutants (metals, organic compounds, etc.) to the ecosystem causing a threat to human health [4]. Therefore, the
land and water availability, where these pollutants are expected to be localized, is
minimalized for agricultural activity or human habitat [5].
1.2 Contaminants in the Soil and Its Risks
Soil is mainly contaminated by metals such as arsenic, lead, and cadmium and
organic pollutants such as polychlorinated biphenyls (PCB) and polycyclic aromatic
hydrocarbons (PAH) and pharmaceuticals. The soil quality deteriorates by the
presence of heavy metals and adversely affects the normal metabolism, prevents
the vegetation, and interferes the functioning of both the soil and plant biota [6]. The
mobility and the toxicity of such metals and organic pollutants in soil depend on
many factors like pH; total concentration; soil composition or chemical properties of
the soil; soil texture like sand, clay, and silt; soil structure which refers to the
arrangement of particles; permeability; specific chemical form of the pollutants;
binding state; properties of the pollutant; soil salinity; etc. [7].
Heavy metals are highly persistent which makes the remediation of heavy metalcontaminated soil complex. The inception of soil-borne heavy metals to the ecosystem food chain is dependent on the source and the amount of the metal input, rate and
magnitude of uptake, properties of the soil, and the extent of absorption level by the
animals [1]. The most common metals found in the soil are chromium, iron, arsenic,
lead, nickel, zinc, copper, cadmium, and mercury. The accumulation of heavy metals
is found in various forms of its geochemical property, e.g., bound in carbonate
phase, sulfides, Fe/Mn oxides, or residual forms [8]. The exposure of heavy metals to
human may occur through inhalation of air or by ingestion of food and water. It may
lead to chronic accumulation of metals in human kidneys and liver
(bioaccumulation). Such contaminants have been observed to affect the biochemical
46
S. Sophia and V. Shetty Kodialbail
1 Introduction
1.1 Environmental Toxins and Contaminants
For a functional and a balanced ecosystem, the protection of the environment is a
chief factor. Huge number of environmental toxins and pollutants can lead to highlevel degradation impact on the ecosystem, especially soil [1]. About 25% of the
global soil is reported to be highly degraded and 44% to be significantly degraded.
Various anthropogenic and natural causes lead to degradation of the soil quality by
both the organic and inorganic pollutants [2]. Human activities in metalliferous
mining, smelting, sewage sludge treatment, agricultural fertilizers, military training
and warfare, landfills, electronic industries, electroplating, energy and fuel production [3], etc. lead to an ineluctable release of the pollutants (metals, organic compounds, etc.) to the ecosystem causing a threat to human health [4]. Therefore, the
land and water availability, where these pollutants are expected to be localized, is
minimalized for agricultural activity or human habitat [5].
1.2 Contaminants in the Soil and Its Risks
Soil is mainly contaminated by metals such as arsenic, lead, and cadmium and
organic pollutants such as polychlorinated biphenyls (PCB) and polycyclic aromatic
hydrocarbons (PAH) and pharmaceuticals. The soil quality deteriorates by the
presence of heavy metals and adversely affects the normal metabolism, prevents
the vegetation, and interferes the functioning of both the soil and plant biota [6]. The
mobility and the toxicity of such metals and organic pollutants in soil depend on
many factors like pH; total concentration; soil composition or chemical properties of
the soil; soil texture like sand, clay, and silt; soil structure which refers to the
arrangement of particles; permeability; specific chemical form of the pollutants;
binding state; properties of the pollutant; soil salinity; etc. [7].
Heavy metals are highly persistent which makes the remediation of heavy metalcontaminated soil complex. The inception of soil-borne heavy metals to the ecosystem food chain is dependent on the source and the amount of the metal input, rate and
magnitude of uptake, properties of the soil, and the extent of absorption level by the
animals [1]. The most common metals found in the soil are chromium, iron, arsenic,
lead, nickel, zinc, copper, cadmium, and mercury. The accumulation of heavy metals
is found in various forms of its geochemical property, e.g., bound in carbonate
phase, sulfides, Fe/Mn oxides, or residual forms [8]. The exposure of heavy metals to
human may occur through inhalation of air or by ingestion of food and water. It may
lead to chronic accumulation of metals in human kidneys and liver
(bioaccumulation). Such contaminants have been observed to affect the biochemical
46
S. Sophia and V. Shetty Kodialbail