16
K. KirupaSree et al.
3 Effects of Heavy Metal Accumulation on the Earth
Environment is polluted by various ways and heavy metals are the main source for
pollution which affects many biological systems in the world as heavy metals does
not undergo biodegradation. According to the Biological functions, these metals
has been classified as: (i) toxic metalloids and metals with undefined biological
functions, (ii) fundamental metals with known biological functions, (iii) non-essential
and nontoxic metal with no biological functions (Pepper et al. 2015). Heavy metals
ions are chemical moieties which would influence its negative effects through diverse
mechanisms such as protein damage, DNA damage and oxidative damage through
the production of reactive oxygen species etc., (Assal et al. 2017). Most of the heavy
metals are toxic to the environment in that Pb, Co, Cd stands in the first line and are
differentiated from other pollutants; those are not biodegraded however these heavy
metals can be accumulated in living organisms resulting in various diseases and
disorders even at lower concentrations (Pehlivan et al. 2009). Soil is the backbone
of agriculture and the worst effects are caused due to the accumulation of heavy
metals in plants. Higher organisms that consume heavy metal accumulated plants
face numerous health issues. This may also have a negative crash on balance of
soil micro flora, plant growth and in the ground cover at the level of ground water
purity (Roy et al. 2005). The toxicity of heavy metal against the plant and plant
associated microbes are described in the table as well as the most of the PGPR which
are involved in the phytoremediation has shown in the Table 1.
3.1 Arsenic
Arsenic is moderately distributed in natural waters which are related with geological
sources. Likewise in various locations of anthropogenic inputs, such as the use of
pesticides, insecticides as well as the combustion of fossil fuels are the enormously
important additional sources. Oxidation states III and V of arsenic occurs in natural
waters, in the form of arsenic acid (H 3 AsO 5 ) and its salts, arsenous acid (H 3 AsO 3 )
and its salts, respectively (Sawyer et al. 2003). Arsenic contamination in groundwater
may create major problem during irrigations. For example, it accumulates in plant
tissues including grains and contaminates food chain (Verma et al. 2016). In recent,
study has been carried out to inspect the molecular mechanisms and physiology of
arsenic accumulation, toxicity, detoxification and tolerance in various plants (Kumar
et al. 2015) some of the plant growth promoting rhizobacteria which is resistant to
the arsenic is shown in the Table 1.
K. KirupaSree et al.
3 Effects of Heavy Metal Accumulation on the Earth
Environment is polluted by various ways and heavy metals are the main source for
pollution which affects many biological systems in the world as heavy metals does
not undergo biodegradation. According to the Biological functions, these metals
has been classified as: (i) toxic metalloids and metals with undefined biological
functions, (ii) fundamental metals with known biological functions, (iii) non-essential
and nontoxic metal with no biological functions (Pepper et al. 2015). Heavy metals
ions are chemical moieties which would influence its negative effects through diverse
mechanisms such as protein damage, DNA damage and oxidative damage through
the production of reactive oxygen species etc., (Assal et al. 2017). Most of the heavy
metals are toxic to the environment in that Pb, Co, Cd stands in the first line and are
differentiated from other pollutants; those are not biodegraded however these heavy
metals can be accumulated in living organisms resulting in various diseases and
disorders even at lower concentrations (Pehlivan et al. 2009). Soil is the backbone
of agriculture and the worst effects are caused due to the accumulation of heavy
metals in plants. Higher organisms that consume heavy metal accumulated plants
face numerous health issues. This may also have a negative crash on balance of
soil micro flora, plant growth and in the ground cover at the level of ground water
purity (Roy et al. 2005). The toxicity of heavy metal against the plant and plant
associated microbes are described in the table as well as the most of the PGPR which
are involved in the phytoremediation has shown in the Table 1.
3.1 Arsenic
Arsenic is moderately distributed in natural waters which are related with geological
sources. Likewise in various locations of anthropogenic inputs, such as the use of
pesticides, insecticides as well as the combustion of fossil fuels are the enormously
important additional sources. Oxidation states III and V of arsenic occurs in natural
waters, in the form of arsenic acid (H 3 AsO 5 ) and its salts, arsenous acid (H 3 AsO 3 )
and its salts, respectively (Sawyer et al. 2003). Arsenic contamination in groundwater
may create major problem during irrigations. For example, it accumulates in plant
tissues including grains and contaminates food chain (Verma et al. 2016). In recent,
study has been carried out to inspect the molecular mechanisms and physiology of
arsenic accumulation, toxicity, detoxification and tolerance in various plants (Kumar
et al. 2015) some of the plant growth promoting rhizobacteria which is resistant to
the arsenic is shown in the Table 1.