2.1 Fluoride
There are around 12 million tons of fluoride stores in the ground in India of the
estimated 85 million tons present in the world [104]. The fluoride is highly scattered
in our environment accounting for 0.3 g/kg of the earth’s crust, resulting thirteenth
in abundance. When fluorine reacts with other elements and forms ionic compounds
like hydrogen fluoride and sodium fluoride in water and after dissociation it results
into negatively charged fluoride ion [4]. Fluoride’s chief natural source in soil is its
parent rock itself [118]. In granitic rocks, fluoride, the only principal mineral of
fluorine occurs chiefly as an extra mineral which contain sits concentrations of 20–
3600 ppm [107, 112]. Apatite, amphiboles, biotite, hornblende, micas, muscovite,
pegmatite, certain types of clays apart from villiaumite also contain fluorine [13, 34,
39]. There are other sources of fluoride into environment such as aluminum
smelters, glass, enamel, textile dyeing, brick and tile works, plastics factories,
phosphate fertilizer plants, industrial plants manufacturing hydrofluoric acid, along
with the thermal power plants which consume high sulphur non-coking coal. At
present high-tech industries like those involved in manufacturing semiconductors
and integrated circuits generate large quantities of industrial effluents that contain
fluoride [23, 25, 69, 73]. Though Fluoride with a very precise amount is an
indispensable component for the normal mineralization of bones and development
of teeth enamel, but its unnecessary intake could result into fluorosis [7, 59]. Low
calcium and high bicarbonate alkalinity has been observed to favor high fluoride
content in groundwater [15]. The water with high fluoride is normally soft, having
high pH and high quantity of silica. In groundwater the amount of fluoride depends
on various factors like aquifer’s geological, chemical and physical characteristics,
texture of soil and rocks, temperature, the action of other chemicals and the depth of
wells [59]. The maximum limits of fluoride in drinking water as per WHO
guidelines must not exceed 1.5 mg/L [116].
2.2 Nitrate
Nitrogen in the form of NO 3
− , NO 2
− , NH 3
+ and organic nitrogen could be
groundwater’s one of most common contaminants [66]. Besides, nitrate is also
found naturally in very small concentrations in groundwater [28]. The nitrate
exposure could occur from various environmental sources even as the drinking
water remains the chief source. Though the ground and surface water normally have
low concentrations of nitrates but because of issues like run off and leaching from
agricultural lands, it could increase to high values [67]. In environments like
oxygen-rich nitrate is generally a stable compound. It is highly water soluble and is
easily leached from soils which have negative charges or with moderate to high pH,
without being influenced by adsorption and precipitation reactions. For decades, the
nitrate compound has the ability to remain in groundwater and get accumulated to
24
A. Ahamad et al.
There are around 12 million tons of fluoride stores in the ground in India of the
estimated 85 million tons present in the world [104]. The fluoride is highly scattered
in our environment accounting for 0.3 g/kg of the earth’s crust, resulting thirteenth
in abundance. When fluorine reacts with other elements and forms ionic compounds
like hydrogen fluoride and sodium fluoride in water and after dissociation it results
into negatively charged fluoride ion [4]. Fluoride’s chief natural source in soil is its
parent rock itself [118]. In granitic rocks, fluoride, the only principal mineral of
fluorine occurs chiefly as an extra mineral which contain sits concentrations of 20–
3600 ppm [107, 112]. Apatite, amphiboles, biotite, hornblende, micas, muscovite,
pegmatite, certain types of clays apart from villiaumite also contain fluorine [13, 34,
39]. There are other sources of fluoride into environment such as aluminum
smelters, glass, enamel, textile dyeing, brick and tile works, plastics factories,
phosphate fertilizer plants, industrial plants manufacturing hydrofluoric acid, along
with the thermal power plants which consume high sulphur non-coking coal. At
present high-tech industries like those involved in manufacturing semiconductors
and integrated circuits generate large quantities of industrial effluents that contain
fluoride [23, 25, 69, 73]. Though Fluoride with a very precise amount is an
indispensable component for the normal mineralization of bones and development
of teeth enamel, but its unnecessary intake could result into fluorosis [7, 59]. Low
calcium and high bicarbonate alkalinity has been observed to favor high fluoride
content in groundwater [15]. The water with high fluoride is normally soft, having
high pH and high quantity of silica. In groundwater the amount of fluoride depends
on various factors like aquifer’s geological, chemical and physical characteristics,
texture of soil and rocks, temperature, the action of other chemicals and the depth of
wells [59]. The maximum limits of fluoride in drinking water as per WHO
guidelines must not exceed 1.5 mg/L [116].
2.2 Nitrate
Nitrogen in the form of NO 3
− , NO 2
− , NH 3
+ and organic nitrogen could be
groundwater’s one of most common contaminants [66]. Besides, nitrate is also
found naturally in very small concentrations in groundwater [28]. The nitrate
exposure could occur from various environmental sources even as the drinking
water remains the chief source. Though the ground and surface water normally have
low concentrations of nitrates but because of issues like run off and leaching from
agricultural lands, it could increase to high values [67]. In environments like
oxygen-rich nitrate is generally a stable compound. It is highly water soluble and is
easily leached from soils which have negative charges or with moderate to high pH,
without being influenced by adsorption and precipitation reactions. For decades, the
nitrate compound has the ability to remain in groundwater and get accumulated to
24
A. Ahamad et al.