mechanisms for a cleaner and healthier environment. It details the chemical and
biological remediation of arsenic highlighting the advantages of biological
approaches.
Keywords Pollution · Arsenic contamination · Methylation · Bioremediation ·
Phytoextraction
8.1 Introduction
The delicate environmental balance has been upset due to excess load of numerous
inorganics including heavy metals generated through mining, rapid industrialisation,
and urbanisation. Amongst the heavy metals, environmental pollution caused due to
arsenic contamination is considered as vital for its severe toxicity and potential
associated health risks. Arsenic could generate multiple adverse health effects
because of its many (inorganic and organic) chemical forms, the most common
inorganic trivalent arsenic forms being arsenic trioxide, sodium arsenite, and arsenic
trichloride (Adeniji 2004). The acute symptoms of arsenic poisoning, as a consequence of consuming it above the maximum tolerable limit of 0.05 mg/l, are skin
discoloration, skin thickening and ultimately skin cancer (Khan et al. 2000; Dey
et al. 2017; Banerjee et al. 2011). Arsenic is a metalloid (considered a heavy metal)
under group ‘V’ element of the periodic table (Satyapal et al. 2016). It is found in
four different oxidation states, i.e., +5, +3, 0, and À 3 in nature. Of these, the
pentavalent (As
V ; Arsenate) and trivalent (As
III ; Arsenite) exist mostly in inorganic
forms (Satyapal et al. 2018). Although both pentavalent and trivalent forms are
poisonous but As
III due to its high mobility is 1000-fold more toxic than its
counterpart (Satyapal et al. 2018; Dey et al. 2016). Organic arsenicals derived
from pesticides, herbicides and preservatives are also encountered in the environment (Satyapal et al. 2018).
Heavy metals like lead, arsenic, nickel, mercury, and cadmium are not at all
beneficial to plants, affecting the plant wellbeing negatively through reduced photosynthesis, nutrient uptake and certain enzymatic malfunctioning (Lim et al. 2014).
Low concentration of heavy metals leads to cytotoxicity and higher concentration to
cancer (Tak et al. 2013). It occurs due to contamination in food chain at a point and
bioaccumulation inside the living organisms (Tak et al. 2013). The cellular damage
happens due to the reactive oxygen species ROS, mainly oxygen radicals, damaging
the DNA (Chibuike and Obiora 2014). The sources of arsenic contamination, both
natural and anthropogenic, have resulted in wide arsenic contamination of the soil,
water, air and crops (Satyapal et al. 2016). In certain geographical regions, the
animals and humans are constantly exposed to high arsenic concentrations through
contaminated drinking water and food crops (Satyapal et al. 2018; Dey et al. 2016).
As per World Health Organisation (WHO), the maximum permissible limit for
arsenic contaminant in drinking water is 0.01 mg/l (WHO 2011; Aksornchu et al.
2008).
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P. K. Parhi et al.
biological remediation of arsenic highlighting the advantages of biological
approaches.
Keywords Pollution · Arsenic contamination · Methylation · Bioremediation ·
Phytoextraction
8.1 Introduction
The delicate environmental balance has been upset due to excess load of numerous
inorganics including heavy metals generated through mining, rapid industrialisation,
and urbanisation. Amongst the heavy metals, environmental pollution caused due to
arsenic contamination is considered as vital for its severe toxicity and potential
associated health risks. Arsenic could generate multiple adverse health effects
because of its many (inorganic and organic) chemical forms, the most common
inorganic trivalent arsenic forms being arsenic trioxide, sodium arsenite, and arsenic
trichloride (Adeniji 2004). The acute symptoms of arsenic poisoning, as a consequence of consuming it above the maximum tolerable limit of 0.05 mg/l, are skin
discoloration, skin thickening and ultimately skin cancer (Khan et al. 2000; Dey
et al. 2017; Banerjee et al. 2011). Arsenic is a metalloid (considered a heavy metal)
under group ‘V’ element of the periodic table (Satyapal et al. 2016). It is found in
four different oxidation states, i.e., +5, +3, 0, and À 3 in nature. Of these, the
pentavalent (As
V ; Arsenate) and trivalent (As
III ; Arsenite) exist mostly in inorganic
forms (Satyapal et al. 2018). Although both pentavalent and trivalent forms are
poisonous but As
III due to its high mobility is 1000-fold more toxic than its
counterpart (Satyapal et al. 2018; Dey et al. 2016). Organic arsenicals derived
from pesticides, herbicides and preservatives are also encountered in the environment (Satyapal et al. 2018).
Heavy metals like lead, arsenic, nickel, mercury, and cadmium are not at all
beneficial to plants, affecting the plant wellbeing negatively through reduced photosynthesis, nutrient uptake and certain enzymatic malfunctioning (Lim et al. 2014).
Low concentration of heavy metals leads to cytotoxicity and higher concentration to
cancer (Tak et al. 2013). It occurs due to contamination in food chain at a point and
bioaccumulation inside the living organisms (Tak et al. 2013). The cellular damage
happens due to the reactive oxygen species ROS, mainly oxygen radicals, damaging
the DNA (Chibuike and Obiora 2014). The sources of arsenic contamination, both
natural and anthropogenic, have resulted in wide arsenic contamination of the soil,
water, air and crops (Satyapal et al. 2016). In certain geographical regions, the
animals and humans are constantly exposed to high arsenic concentrations through
contaminated drinking water and food crops (Satyapal et al. 2018; Dey et al. 2016).
As per World Health Organisation (WHO), the maximum permissible limit for
arsenic contaminant in drinking water is 0.01 mg/l (WHO 2011; Aksornchu et al.
2008).
220
P. K. Parhi et al.