PIAHSProceedings of the International Association of Hydrological SciencesPIAHSProc. IAHS2199-899XCopernicus PublicationsGöttingen, Germany10.5194/piahs-379-351-2018Fluoride in groundwater: a case study in Precambrian terranes of Ambaji region, North Gujarat, IndiaFluoride in groundwaterPradhanRudra Mohanrudra.pradhan@iitb.ac.inhttps://orcid.org/0000-0002-9977-9223BiswalTapas KumarDepartment of Earth Sciences, Indian Institute of Technology Bombay, Powai-400076, IndiaRudra Mohan Pradhan (rudra.pradhan@iitb.ac.in)5June201837935135631December201720February201826February2018This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/This article is available from https://piahs.copernicus.org/articles/379/351/2018/piahs-379-351-2018.htmlThe full text article is available as a PDF file from https://piahs.copernicus.org/articles/379/351/2018/piahs-379-351-2018.pdf
Fluoride is one of the critical ions that influence the
groundwater quality. World Health Organization (WHO, 1970) and Bureau of Indian
Standards (BIS, 1991) set an upper limit of 1.5 mg L-1 in F-
concentration for drinking water purpose and above affects teeth and bones of
humans. The presence of fluoride in groundwater is due to an interaction of
groundwater and fluoride bearing rocks. Fluoride rich groundwater is well
known in granitic aquifers in India and elsewhere. Generally, the
concentration of F- in groundwater is controlled by local geological
setting; leaching and weathering of bedrock and climatic condition of an
area. The main objective of the present study is to assess the
hydrogeochemistry of groundwater and to understand the abundance of F-
in groundwater in hard rock terranes of Ambaji region, North Gujarat. A total
of forty-three representative groundwater samples were collected and analyzed
for major cations and anions using ICP-AES, Ion Chromatograph (Metrohm 883
Basic IC Plus) and titration methods. The F- concentration in
groundwater of this study area ranges from 0.17 to 2.7 mg L-1. Among,
twenty groundwater samples have fluoride exceeding the maximum permissible
limit as per the BIS (1.5 mg L-1). It is also noticed that residents
of this region are affected by dental fluorosis. The general order of the
dominance of major cations and anions are
Ca2+ > Mg2+ > Na+ > K+
and HCO3- > Cl- > F-
respectively. Geochemical classification of groundwater shows most of the
samples are the alkaline earth-bicarbonate type. The semi-arid climatic
conditions of the region, the dominance of granitoid-granulite suite rocks
and the fracture network in the disturbed and brittle zone has facilitated
the development of potential aquifers and enrichment in F- concentration
in this area. The concentration of fluoride is due to high evaporation rate,
longer residence time in the aquifer zone, intensive and long term pumping
for irrigation.
Geological map and sample locations of the study area (modified
after Singh et al., 2010).
Introduction
The usefulness of groundwater to human is great extent. Groundwater is
considered to be the major source of drinking water in India. Groundwater
chemistry is largely a function of the mineral composition of the aquifer
through which it flows (Brindha and Elango, 2011). It depends upon physical
and geological factors such as evaporation rate, residence time, aquifer
media, rock–water interaction, recharge capacity, and anthropogenic
activities. Fluoride in groundwater may be of geogenic (natural) or
anthropogenic (Human induced). Fluoride is widely distributed in the
environment and it ranks 13th among other elements in order of abundance in
the earth's crust. Its natural abundance in the earth's crust is 0.06 to
0.09 % and 300 mg kg-1. Generally, fluoride does not exhibit any
colour, taste or smell when dissolved in water and hence, it is difficult to
determine through physical examination. Fluoride is naturally present due to
weathering of rocks rich in fluoride. Groundwater in crystalline rocks,
mainly granites/granite gneisses are particularly vulnerable to fluoride
because they often contain abundant fluoride bearing minerals (fluorite,
apatite, hornblende, and biotite). Fluoride rich groundwater is well-known in
different types of geological terranes and aquifers (Reddy et al., 2010).
Several studies have mentioned an increase in dissolved F-
concentrations with increasing groundwater residence time in the aquifer
systems (Nordstrom and Jenne, 1977; Apambire et al., 1997; Edmunds and
Smedley, 2013). Prolonged rock-water interactions through weathering of
fluoride-rich rocks enrich fluoride concentration in the groundwater systems.
Consequently, fluoride is leached out and dissolves in groundwater and
thermal gases (Deshmukh et al., 1995). Fluorite, apatite, mica (biotite) and
hornblende are the minerals, which have the most effect on the geochemistry
of F- in groundwater (Dar et al., 2011) when they are interacted with
groundwater and dissolved, leads to increasing F- in groundwater (Rao,
2017). Groundwater interacting with crystalline rocks, mainly (alkaline)
granites/granite gneisses (deficient in calcium) and hydrothermal solutions
are probably to have reasonably high fluoride concentrations (Brunt et al.,
2004). Ayenew (2008) studied that the higher concentration of F- is due
to low concentration of Ca2+ under an alkaline environment in Ethiopian
groundwater. In different parts of China, Li et al. (2014, 2017) found that
the high F- was controlled by hydrogeological conditions, but also
man-made activities and mixing of different recharge waters were also key
reasons. High fluoride groundwater has been recorded as one of the most
critical natural groundwater quality problems associated with hard rock areas
in India (Handa, 1975; Reddy et al., 2010; Raj and Shaji, 2017;
Shekhar et al., 2017). More than 200 million people from different nations
suffer health problems due to high fluoride in groundwater (Ayoob and Gupta,
2006; Wu and Sun, 2016). In India, there has been an increase in the
incidence of dental and skeletal fluorosis due to high fluoride concentration
in drinking water. Dental fluorosis is common in 17 states of India with most
pronounced in the states of Andhra Pradesh, Gujarat, Madhya Pradesh, Bihar,
Punjab, Rajasthan, Tamil Nadu, Telangana, Uttar Pradesh and West Bengal
(CGWB, 2015). World Health Organization (WHO, 1970) and Bureau of Indian Standards
(BIS, 1991) set an upper limit of 1.5 mg L-1 in F- concentration for
drinking water purpose and above affects teeth and bones of humans. In the
literature, early researchers (Handa, 1988; Gupta, 1991; Sharma et al., 2005;
Chinoy et al., 2005; Brindha and Elango, 2011; Raj and Shaji, 2017)
discussed that fluoride and fluorosis were correlated with high concentration
of fluoride ion in drinking water in different parts of India. In this paper,
the data pertaining to fluoride in groundwater of Ambaji region of North
Gujarat, India has been presented and discussed.
Materials and methodsStudy area
The present area of study covers a part of Ambaji region
(Ambaji-Amirgard-Dhanpura-Kanpura) situated in Banaskantha District of
Gujarat state, India (Fig. 1). On the South, it is bounded by Mehsana
district where high Fluoride in groundwater is reported. The area belongs to
the Survey of India toposheet no. 45D/11, 45D/12 and 45D/15 (scale
1 : 50 000). The area has a diverse landscape and characterized by hilly
upland with intermountain valleys, followed by piedmont zone with alluvium
and residual hills and gently sloping vast alluvial plain. The area falls
under semi-arid climate. Extreme temperatures (hot summer and dryness in the
non-rainy seasons), erratic rainfall and high evaporation are the typical
characteristic features of this type of climate. The annual rainfall of this
region is 578.8 mm and is mostly received during the south-west monsoon
season from June to September. Since it falls in a semi-arid type of climate,
the rivers flowing through it are of ephemeral nature i.e. have water during
monsoon only and dry up after monsoon period. The drainage network is
constituted mainly by the Banas River and their tributaries (Balaram River).
Geologically, the area belongs to the Meso-proterozoic South Delhi Terrane
(1100–900 Ma), Aravalli craton. The rocks are pelitic-, calcareous-,
calcareous and basic-granulites; these are intruded by three phases of Ambaji
granites (G1, G2, G3). The rocks are extremely fractured along large-scale
faults and shear zones (Singh et al., 2010).
Sampling and instrumentation
The area has been subjected to a high degree of deformation, which gives rise
to fracture networks and this can be traced surficially and through remote
sensing and GIS study. These intersecting fracture networks suggest that the
water-yielding zones for phreatic and deeper aquifers are interconnected in
hydraulic continuity. A total of forty-three ground water samples (Tube
well/Bore well/Dug well) from different aquifers (Fig. 1) were collected in
the month of May and June 2017 (Table 1) for the present study. In this area
the depth of dug well ranges from 10 to 20 m b.g.l. with a diameter of 3 to
5 m and water level ranges from 3 to 15 m b.g.l. The depths of tube well
are ranging from 60 to 90 m with 20 to 25 cm in diameter. Water samples
were collected in HDPE bottles of 500 mL capacity. Samples collected in the
field were filtered using 0.45 µm Millipore filter paper and
Alkalinity of groundwater samples measured through titration methods. Water
samples were brought to the laboratory for geochemical analysis. Groundwater
field parameters (pH, EC, TDS, Temperature) were measured in the field using
portable HANNA pH meter. Major cations and anions of water samples were
determined using ICP-AES and Ion chromatograph (Metrohm 883 Basic IC Plus)
with appropriate standards.
Physical and chemical analysis of groundwater of Ambaji region,
North Gujarat, India.
Fluoride is one of the important ions that influence the groundwater quality.
Fluorite (CaF2) is the only principal fluorine mineral, mostly present
as an accessory mineral in granites. The results of hydrogeochemical
parameters of groundwater samples including fluoride concentration are
presented in Table 1. Fluoride concentration in groundwater
of Ambaji regions varied between 0.17 mg L-1 (Bhyla village) to
2.7 mg L-1 (Padni village). It was revealed that twenty groundwater
samples have fluoride exceeding the maximum permissible limit as per the BIS
(1.5 mg L-1) and twenty-three groundwater samples are within the
permissible limit (Table 2). Fluoride concentration in seven villages is very
alarming in this region. The maximum concentration of fluoride was recorded
in Padni (2.7 mg L-1), Kengora (2.3 mg L-1), Padliya
(2.2 mg L-1), Kothiavas (1.8 mg L-1),Virampur (2 and
1.6 mg L-1), Khemrajya (1.9 mg L-1), Kanpura (1.5
(mg L-1), Ajapur Mota (2 mg L-1) and Dhanpura
(1.8 mg L-1). Wide variation of fluoride concentration is probably due
to variation in chemical strata of different rocks.
Comparison of fluoride content with drinking water standards (BIS,
1991 and WHO, 1970).
BIS standard WHO standard ParameterHighest Maximum Highest Maximum Number of samples% of sampledesirablepermissibledesirablepermissibleexceedingexceeding(mg L-1)(mg L-1)(mg L-1)(mg L-1)permissible limitpermissible limitFluoride0.6–1.21.50.51.52046
Minimum, Maximum and Statistical values of water parameters.
Spatial distribution of fluoride in groundwater of Ambaji region.
Figure 2 shows the spatial distribution of fluoride concentration in
different aquifers in Ambaji region. It was also found that high fluoride
groundwater is concentrated mostly in the discharge areas than in the
recharge areas with a trend of fluoride enrichment along the direction of
flow. Other physico-chemical parameters such as pH, TDS, EC, major cations
and anions of groundwater were analysed. Minimum, maximum and statistical
values of water parameters are given in Table 3. The pH (H+ ion in the
solution) value is ranging from 6.44 to 7.45 in the study area and most of
the groundwater samples found to be within the permissible limit. In the
study area, Electrical conductivity (EC) ranged between 400 µScm-1 (Dhanpura) to 2170 µScm-1 (Padni) except TW-39
(Dhanpura) which is 4370 µScm-1. The high EC values of
samples may be due to the primary minerals of earth's crust dissolved in
water samples. All natural water contains different concentrations of Total
Dissolved Salts (TDS) as a result of the dissolution of minerals within the
rocks and soils. The essential ions that contribute TDS are carbonate,
bicarbonate, sodium, potassium, calcium, magnesium, fluoride, chloride,
nitrates and sulphates. TDS values varied from 200 to 1085 mg L-1
(Padni) except Dhanpura village (2185 mg L-1) which is much higher
than the permissible limit. The occurrence of other ions, mainly bicarbonate
(HCO3-) and calcium (Ca2+) ions also affects the concentration
of fluoride in groundwater. Most of the samples are collected from aquifers
of weathered and fractured zones occurring in the unconfined/semi unconfined
conditions. Jacks (1990) studied that chemical weathering of minerals results
in the formation of Ca- and Mg-carbonates which helps as good sinks for
fluoride ions. But, it is the leachable state of fluoride ions that determine
the water fluoride levels which is mainly due to (i) pH of the draining
solutions and (ii) dissolved carbon dioxide in the soil. Dissolved fluoride
in groundwater is possible only under favorable physico-chemical environments
and with enough residence time (Handa, 1975).
In the present study, the general order of the dominance of major cations and
anions are
Ca2+ > Mg2+ > Na+ > K+
and HCO3- > Cl- > F-
respectively. Geochemical classification of groundwater shows most of the
samples are of alkaline earth-bicarbonate type. These waters had temporary
hardness because the concentration of Ca2+ and Mg2+ ions exceeds
over Na+ and K+ ions. Simultaneously, values of CO32- and
HCO3- ions together were high as compared to SO42- and
Cl- ions together. The groundwater samples are classified into
Ca2+-Mg2+-HCO3-, Ca-Cl and Na-Cl hydrogeochemical facies
which are due to lithology. The possible reason for the presence of
fluoride-rich groundwater in the granitic area is due to release of fluoride
from the fluoride-bearing minerals in the rocks. The alkaline water depleted
in calcium is mainly responsible for the high concentration of F- (Shaji
et al., 2007). The long residence time of water in the aquifer system, caused
by a high rate of evapotranspiration and a weathered zone of low hydraulic
conductivity, are the additional factors that trigger to the dissolution of
fluorine-bearing minerals for further increase of F- content in
groundwater. Geochemical behavior of groundwater from the study suggests that
high fluoride groundwater contain low levels of Calcium and high alkalinity.
High pH and HCO3-/Ca2+ suggest favorable chemical conditions for
fluoride dissolution process.
Generally, the concentration of F- in groundwater is controlled by local
geological setting, leaching, and weathering of bedrock and climatic
condition of an area. As the area falls under semi-arid climatic conditions,
the dominance of granitoid-granulite suite rocks and the fracture network in
the disturbed and brittle zone has facilitated the development of potential
aquifers and enrichment in F- concentration. Also, it is noticed that
the concentration of fluoride is due to high evaporation rate, longer
residence time and comparatively low rainfall in the aquifer zone, intensive
and long term pumping for irrigation.
Therefore, to maintain the quality of ground water, it is recommended for
continuous monitoring of physico-chemical parameters of water and can be
used for drinking and other uses only after prior treatment.
The data presented here are part of Rudra Mohan Pradhan's
doctoral thesis work and yet, Ph.D. is not completed. However, individual
data are available from the author(s) on request. Those interested in using
this data may contact the corresponding author.
The authors declare that they have no conflict of
interest.
This article is part of the special issue “Innovative water
resources management – understanding and balancing interactions between
humankind and nature”. It is a result of the 8th International Water
Resources Management Conference of ICWRS, Beijing, China, 13–15 June 2018.
Acknowledgements
Authors are acknowledges to Ministry of Earth Sciences (MoES), Govt. of India
and Department of Earth Sciences, Indian Institute of Technology Bombay for
financial assistance. Rudra Mohan Pradhan thankful to Bhuban Mohan Behera and
Abdul Rajik Khan for their help during field work. Thanks are due to the two
anonymous reviewers for their valuable comments that improved the quality of
this manuscript. Edited by: Wenchao
Sun Reviewed by: two anonymous referees
References
Apambire, W. B., Boyle, D. R., and Michel, F. A.: Geochemistry, genesis, and
health implications of fluoriferous groundwaters in the upper regions of
Ghana, Environ. Geol., 33, 13–24, 1997.
Ayenew, T.: The distribution and hydrogeological controls of fluoride in the
groundwater of central Ethiopian rift and adjacent highlands, Environ. Geol.,
54, 1313–1324, 2008.
Ayoob, S. and Gupta, A. K.: Fluoride in drinking water: a review on the
status and stress effects, Crit. Rev. Env. Sci. Tech., 36, 433–487, 2006.
BIS: 10500: Specification for Drinking Water, Indian Standard Institution
(Indian Bureau of Standard), New Delhi, 1–4, 1991.
Brindha, K. and Elango, L.: Fluoride in Groundwater: Causes, Implications and
Mitigation Measures, in: Fluoride Properties, Applications and Environmental
Management, edited by: Monroy, S. D., 111–136, 2011.
Brunt, R., Vasak, L., and Griffioen, J.: Fluoride in groundwater: probability
of occurrence of excessive concentration on global scale, Igrac:
International Groundwater Resources Assessment Centre, Report nr. SP 2004-2,
1–12, 2004.
CGWB: Groundwater quality scenario in India, Central Ground Water Board,
Government of India, New Delhi, 2015.
Chinoy, N. J., Sequeira, E., Narayana, M. V., Mathews, M., Barot, V. V.,
Kandoi, P. R., and Jhala, D. D.: A survey of fluoride in 90 endemic villages
of Mehsana and Banaskantha districts of North Gujarat, India, Fluoride, 38.3,
224, 2005.
Dar, M. A., Sankar, K., and Dar, I. A.: Fluorine contamination in
groundwater: a major challenge, Environ. Monit. Assess., 173, 955–968, 2011.
Deshmukh, A. N., Wadaskar, P. M., and Malpe, D. B.: Fluorine in environment:
A review, Gondwana Geol. Mag., 9, 1–20, 1995.
Edmunds, W. M. and Smedley, P. L.: Fluoride in natural waters, in: Essentials
of medical geology, 311–336, Springer, Dordrecht, 2013.
Gupta, S. C.: Chemical character of groundwater in Nagaur district,
Rajasthan, Ind. J. Environ. Hlth., 33, 341–349, 1991.
Handa, B. K.: Geochemistry and genesis of Fluoride-Containing ground waters
in India, Groundwater, 13, 275–281, 1975.
Handa, B. K.: Fluoride occurrences in natural water in India and its
significance, BHU-Jal News, 3, 21–24, 1988.Jacks, G.: Mineral weathering studies in Scandinavia, in: The Surface Waters
Acidification Programme, 215–222, Cambridge University Press, 1990.
Li, P., Qian, H., Wu, J., Chen, J., Zhang, Y., and Zhang, H.:
Occurrence and hydrogeochemistry of fluoride in alluvial aquifer
of Weihe River, China, Environ. Earth Sci., 71, 3133–3145, 2014.
Li, P., Tian, R., Xue, C., and Wu, J.: Progress, opportunities, and key
fields for groundwater quality research under the impacts of human activities
in China with a special focus on western China, Environ. Sci. Pollut. R., 24,
3224–13234, 2017.
Nordstrom, D. K. and Jenne, E. A.: Fluorite solubility equilibria in selected
geothermal waters, Geochim. Cosmochim. Ac., 41, 175–188, 1977.
Raj, D. and Shaji, E.: Fluoride contamination in groundwater resources of
Alleppey, southern India, Geosci. Front., 8, 117–124, 2017.
Rao, N. S.: Controlling factors of fluoride in groundwater in a part of South
India, Arab. J. Geosci., 10, p. 524, 2017.
Reddy, D. V., Nagabhushanam, P., Sukhija, B. S., Reddy, A. G. S., and
Smedley, P. L.: Fluoride dynamics in the granitic aquifer of the Wailapally
watershed, Nalgonda District, India, Chem. Geol., 269, 278–289, 2010.
Shaji, E., Viju, J., and Thambi, D. S.: High fluoride in groundwater of
Palghat District, Kerala, Current Science, 240–245, 2007.
Sharma, J. D., Parul, J., and Deepika, S.: Geological study of fluoride in
groundwater of Sanganer tehsil of Jaipur district, Rajasthan, India,
Fluoride, 38, p. 249, 2005.
Shekhar, S., Ghosh, M., Pandey, A. C., and Tirkey, A. S.: Impact of geology
and geomorphology on fluoride contaminated groundwater in hard rock terrain
of India using geoinformatics approach, Applied Water Science, 7, 2943–2956,
2017.
Singh, Y. K., De Waele, B., Karmakar, S., Sarkar, S., and Biswal, T. K.:
Tectonic setting of the Balaram-Kui-Surpagla-Kengora granulites of the South
Delhi Terrane of the Aravalli Mobile Belt, NW India and its implication on
correlation with the East African Orogen in the Gondwana assembly,
Precambrian Res., 183, 669–688, 2010.
World Health Organization (WHO): Fluoride and human health, WHO monograph series
no. 59, 1970.
Wu, J. and Sun, Z.: Evaluation of shallow groundwater contamination and
associated human health risk in an alluvial plain impacted by agricultural
and industrial activities, mid-west China, Expos. Health, 8, 311–329, 2016.