are conservative in nature and their ratio is used as the source of salinity in coastal
aquifers. The conservative nature of these elements reduces the biological uptake as
well as sedimentation [35].
Fluoride (F
− )
Fluoride is the highest electronegative element among all the chemical elements. It
has an affinity to form fluoride ion in the solution. It is found in only solid salt and
ion in aqueous solution as it is very reactive [36, 37]. Fluoride is found in almost all
type of water from trace to high concentration. Various factors such as temperature,
pH, and solubility of fluoride bearing minerals impose the impact on the concentration of fluoride in the water. Fluoride contamination in groundwater is a common
problem in semi arid and arid climate having alkaline soil and crystaline igneous
rocks [36, 38]. Geogenic sources mainly from igneous (granite) and metamorphic
(gneisses) rocks are considered as the primary source of fluoride in groundwater
[39]. Fluorite, apatite, mica, amphiboles and some clay are the fluoride wearing
minerals. Moreover anthropogenic sources also contribute fluoride in water such as
chemicals used in agriculture and bricks industries [40].
Both the lower (0.6 mg/l) and upper (1.5 mg/l) limit of fluoride in groundwater
have heath effects. Very low limit of fluoride (<0.6) in drinking water leads to tooth
decay while consumption in higher concentration (>1.5 mg/l) causes dental
fluorosis even more concentration (>3 mg/l) leads to skeletal fluorosis [41]. Due to
high concentration of fluoride in water about 62 million people in India including
6 million children suffers from fluorosis [42].
Chloride
Ion exchange processes, halite dissolution, precipitation, farming overflow,
untreated effluents from industries, sewage wastes etc. are source of chloride in
water resources. Owing to extremely less or insignificant biological uptake of
chloride my cause higher chloride concentration once it released in water. The
dichloromethane present as a byproduct during conventional water chlorination
procedures and other carcinogenic substances by reacting with naturally occurring
compound [43, 44]. High values of Cl in water disgrace the water quality. It also
contributes to the corrosion of many metals, including man-made structures, such as
dams.
Bromide
Naturally, bromide enriched in water as inorganic salt in natural water resources. In
fresh water, bromide concentration may naturally derive from rainfall, but significant level may be caused by the combustion of leaded gasoline containing ethylene
dibromide. The elevated level of bromide caused due to industrial dumping and
agricultural runoff. Bromide is conservative in nature. Due to its conservative
nature, it has been used as an indicator of saltwater intrusion and source of salinity
and contaminant in coastal aquifers [44, 45]. But high concentrations of Br may
cause fatal consequence on aquatic organisms. The impact of high bromide in
plants can cause the stunted growth and poor germination.
Water Pollutants: Sources and Impact on the Environment …
47
aquifers. The conservative nature of these elements reduces the biological uptake as
well as sedimentation [35].
Fluoride (F
− )
Fluoride is the highest electronegative element among all the chemical elements. It
has an affinity to form fluoride ion in the solution. It is found in only solid salt and
ion in aqueous solution as it is very reactive [36, 37]. Fluoride is found in almost all
type of water from trace to high concentration. Various factors such as temperature,
pH, and solubility of fluoride bearing minerals impose the impact on the concentration of fluoride in the water. Fluoride contamination in groundwater is a common
problem in semi arid and arid climate having alkaline soil and crystaline igneous
rocks [36, 38]. Geogenic sources mainly from igneous (granite) and metamorphic
(gneisses) rocks are considered as the primary source of fluoride in groundwater
[39]. Fluorite, apatite, mica, amphiboles and some clay are the fluoride wearing
minerals. Moreover anthropogenic sources also contribute fluoride in water such as
chemicals used in agriculture and bricks industries [40].
Both the lower (0.6 mg/l) and upper (1.5 mg/l) limit of fluoride in groundwater
have heath effects. Very low limit of fluoride (<0.6) in drinking water leads to tooth
decay while consumption in higher concentration (>1.5 mg/l) causes dental
fluorosis even more concentration (>3 mg/l) leads to skeletal fluorosis [41]. Due to
high concentration of fluoride in water about 62 million people in India including
6 million children suffers from fluorosis [42].
Chloride
Ion exchange processes, halite dissolution, precipitation, farming overflow,
untreated effluents from industries, sewage wastes etc. are source of chloride in
water resources. Owing to extremely less or insignificant biological uptake of
chloride my cause higher chloride concentration once it released in water. The
dichloromethane present as a byproduct during conventional water chlorination
procedures and other carcinogenic substances by reacting with naturally occurring
compound [43, 44]. High values of Cl in water disgrace the water quality. It also
contributes to the corrosion of many metals, including man-made structures, such as
dams.
Bromide
Naturally, bromide enriched in water as inorganic salt in natural water resources. In
fresh water, bromide concentration may naturally derive from rainfall, but significant level may be caused by the combustion of leaded gasoline containing ethylene
dibromide. The elevated level of bromide caused due to industrial dumping and
agricultural runoff. Bromide is conservative in nature. Due to its conservative
nature, it has been used as an indicator of saltwater intrusion and source of salinity
and contaminant in coastal aquifers [44, 45]. But high concentrations of Br may
cause fatal consequence on aquatic organisms. The impact of high bromide in
plants can cause the stunted growth and poor germination.
Water Pollutants: Sources and Impact on the Environment …
47