Geochemistry and Health Impact of Fluoride in Groundwater in parts of Anantapur District, Andhra Pradesh

TABLE OF CONTENTS

S.No Title Page Number

List of Tables

List of Figures

ABSTRACT

CHAPTER 1: INTRODUCTION
1.1 Background to the Research
1.2 Research Objectives
1.3 Review of Literature
1.3.1 International Status
1.3.2 National Status

CHAPTER 2: STUDY AREA
2.1 Geomorphology
2.2 Hydrogeology
2.3 Geology

CHAPTER 3: MATERIALS AND METHODS
3.1 Field Work
3.2 Sample Collection
3.3 Experimental Procedures
3.3.1 Determination of Fluoride
3.3.2 Determination of other parameters, methods and instruments

CHAPTER 4: RESULTS AND DISCUSSIONS
4.1 Beneficial effects
4.2 Impact of fluoride on human health
4.2.1 Dental Fluorosis
4.2.2 Skeletal Fluorosis
4.3 Total fluoride ingestion
4.4 Nutritional status
4.5 Dietary factors
4.6 Factors affecting the natural fluoride concentrations
4.6.1 Sources
4.7 Fluoride
4.7.1 Dental Fluorosis
4.7.2 Skeletal Fluorosis
4.7.3 Fluoride Hydrogeochemistry
4.8 Spatial analysis of groundwater quality
4.8.1 Fluoride
4.8.2 pH
4.8.3 Electrical Conductivity
4.8.4 Total Dissolved Solids
4.8.5 Total Hardness
4.8.6 Sodium
4.8.7 Potassium
4.8.8 Calcium
4.8.9 Magnesium
4.8.10 Total Alkalinity (CO3- and HCO3-)
4.8.11 Sulphate
4.8.12 Chloride
4.8.13 Nitrate
4.9 Correlation Analysis
4.10 Chemical Classification
4.11 Classification of groundwater for irrigation purpose
4.11.1 Percent Sodium (%Na)
4.11.2 Residual Sodium Carbonate (RSC)
4.11.3 Sodium Adsorption Ratio (SAR)
4.11.4 Piper Tri-linear Diagram
4.12 Defluoridation Techniques

CHAPTER 5: SUMMARY AND CONCLUSIONS
5.1 Summary
5.2 Conclusions
5.3 Recommendations

REFERENCES

ACKNOWLEDGEMENTS

All glory and honor be to the Almighty God, who showered his generous grace.

I wish to express my sincere gratitude to Dr. V. Sunitha, Assistant Professor, Department of Geology for their untiring involvement, able guidance, thought provoking ideas, constant encouragement at every stage of my research work and brilliant suggestions rendered to me throughout my doctoral research period. I would like to express my thanks to Prof. M. Ramakrishna Reddy, Chairman, BOS, Department of Geology, Yogi Vemana University, Kadapa, for his support and being my moral strength.

I am gratefully thanks to Department of Science and Technology (DST), Government of India; for the financial support for this work.

I would like to express my gratitude to my beloved father Mr. B. Janardhana Reddy; mother Mrs. B. Padmavathi; Brother Mr. B. Jayavardhan Reddy and all my family members for their immense motivation, love and care they have been showering on me all these years.

I would like to express my heart full thanks to my wife, Smt. G.Sravya Sai has been a source of inspiration and encouragement during this publication.

Finally, I would like to thank all who support us and helped us in every aspect for completion of the thesis work.

LIST OF TABLES

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LIST OF FIGURES

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ABSTRACT

Groundwater is an important water resource in India for domestic, irrigation and industrial purposes. Swift unscientific and unsuitable groundwater developments in India suitable to even increasing population, urbanization, industrialization alters. The hydrological and geochemical environment of aquifers leads to groundwater pollution. Groundwater pollution suitable to geogenic and anthropogenic factors causes the groundwater non-potable and utilization of this water lead to health problems. Access of drinking water is measured by the number of people who has a reasonable means of getting an adequate amount of water that is safe for drinking. There is a substantial shortfall in the availability of potable water in less developed countries, primarily arising from contamination and pollution.

Endemic fluorosis is a major health issue occurring due to utilization of fluoride in groundwater is nationally important. Fluoride ion in drinking water is known for both beneficial and detrimental effects on health. It is essential for normal mineralization of bones and formation of dental enamel with presence in small quantity. However, when consumed in higher doses (>1.5mg/l), it leads to dental fluorosis or mottled enamel and excessively high concentration (>3.0mg/l) of fluoride may lead to skeletal fluorosis. Presence of high concentration of fluoride in groundwater is a major problem in many countries as it causes health related problems.

The selected study area is located in Southeastern part of Anantapur District, Andhra Pradesh. The geographical position of the Peninsula renders it, the driest part of the state and hence, agriculture conditions are more often precarious. The study area mainly exposes peninsular gneisses of Archean age consisting of pink granites, schists, composite gneisses of Dharwar age, intruded by a few pegmatite dykes. The major geomorphic units of the study area are mainly divided into Denudational Hills, Dissected pediments, Pediplain, and alluvium. The important rivers in the district are Penna, Chitravathi, Vedavathi and Hagari. The normal rainfall of the district is 553 mm by which it secures least rainfall when compared to Rayalaseema and other parts of Andhra Pradesh. The area experiences a semiarid climate with a moisture index of 33.7% with mean monthly temperatures of 17°C in January to 42°C in May.

The study area has been the focus of the occurrence of dental/skeletal fluorosis among the population in the study area provided the motivation to investigate occurrence of fluoride in groundwater. The present thesis addresses main objectives of the study are (1) To study the sources, distribution of fluoride and its associated chemical parameters in the groundwater of Mudigubba, Nallamada, Kadiri Revenue Mandals of Anantapur district, Andhra Pradesh, through periodical monitoring for two seasons (2) Delineate fluoride zones and preparation of fluoride distribution maps (3) To study the geochemical behavior of fluoride with other parameters (4) To study the fluoride levels in groundwater and to highlight probable causes of contamination (5) To suggest defluoridation techniques.

The study is carried out utilizing topographic maps, Garmin GPS MAP 76, Arc GIS 9.3 and investigations in the field. The field work included water level measurements and collection of water samples from bore wells, tube wells, open wells and the study of geological and geomorphological features of the area in general. Fifty water samples are collected in pre monsoon during April 2009-April 2014 and in the post monsoon fifty water samples are collected during September 2009 - September 2014. The samples are collected in pre-cleaned polyethylene bottles of two litre capacity. The groundwater samples are analyzed as described by American Public Health Association (APHA, 1995) procedure, and suggested precautions are taken to avoid contamination. The various parameters pH and EC are determined by pH meter, conductivity meter, TDS are determined by indirect 2- - -method (Raghunath, 2003), Total Hardness, Ca2+, Mg2+, CO3, HCO3 and Cl are determined by titrimetry, whereas Na+ and K+ are determined by flame photometry (Systronic Model No.128), SO42- and NO3- are determined by spectrophotometric method.F- is determined by using ion selective electrode (Orion 4 star ion meter, Model: pH/ISE). All the experiments are carried out in triplicate and the results are found reproducible within a ±3% error limit.

The analysis results shows that the concentration of fluoride in 40 samples out of 50 exceed the limit for fluoride (1.5 mg/L) in drinking water set by the W.H.O in both pre monsoon and post monsoon seasons during 2009-2014. Assessment of prevalence of dental mottling in the community is the most convenient biomarker of chronic exposure to excess fluoride. Dental fluorosis among children is significantly correlated with the level of fluoride in drinking water in the study area. Few cases of skeletal fluorosis are also noticed with both the legs are affected and have become crippled from Ralla Anantapuram village of Mudigubba Mandal, Bapanakunta village of Nallamada Mandal.

The fluoride concentration in the groundwater samples of the study area is in higher in pre monsoon when compared to post monsoon. The fluoride is dissolved in groundwater mainly from geological sources. Rock-water interaction is the main process in which fluoride-rich minerals are decomposed/dissociated from the source rock and fluoride is dissolved in the groundwater by dissolution. The approximate depth of the sources of the samples show a positive correlation with the fluoride concentration, which indicates the source of fluoride to be fluorite or apatite minerals present in the Precambrian granite or granitic gneiss of the underground basement.

The chemical composition of the water samples reveal slight seasonal variations. The groundwater in the study area is of alkaline in nature. All the other parameters analyzed such as pH, electrical conductivity, total dissolved solids, total alkalinity, total hardness, calcium, magnesium, nitrate, sulphate, phosphate, sodium and potassium are above the desirable limits of WHO and Indian Standards for drinking water. The spatial highs showed a maximum spread in September 2009 - September 2014 whereas isolated patches of highs are distributed in the area during April 2009 - April 2014 in the study area indicated that many of the samples collected are not satisfying the drinking water quality standards prescribed by the WHO. The positive correlation of pH with fluoride indicates that alkaline groundwater is likely to have a higher concentration of fluoride and the alkali metal ions, viz. Na+, K+ showed positive correlation with fluoride content and the alkaline earth metal ions viz. Mg2+ and Ca2+ showed negative correlation with fluoride content. The calcium concentrations are lower than the sodium concentration, which indicates the higher fluoride concentration in the ground water of the study area.

The suitability of water for irrigation can be determined by Percent Sodium (%Na), Sodium Adsorption Ratio (SAR) and Residual Sodium Carbonate (RSC) shows that most of groundwater samples of the study area fall under excellent class suitable for irrigation. There is no significant change in the hydro-chemical facies noticed during the study period (pre and post monsoon), which indicates that most of the major ions are natural in origin.

The literature survey and the laboratory experiments have indicated that plant leaves can remove fluoride under specified conditions. One of the defluoridation techniques developed to control fluoride content in water is Mint leaves (Pudina) as adsorbents. The sorption data for the removal of fluoride ions have been correlated with Freundlich and Langmuir models. Results show that these low-cost bioadsorbents could be fruitfully used for the removal of fluoride over a wide range of concentrations. The percentage of fluoride removal is found to be a function of adsorbent dose and time at a given initial solute concentration. Successful application of the adsorption technique demands innovation of cheap, nontoxic, easily and locally available material bioadsorbents meet these requirements.

CHAPTER - 1 INTRODUCTION

1.1. Background to the Research:

Groundwater, due to its relative purity is well known as the potable water source the world over since time immemorial. The other merits of groundwater over surface water are little or no need of treatment to safeguard its quality, the immense storage potential of aquifers, annual replenishment by rainfall and decentralized facility of taping close to demand centres saving the cost of long transmission. Water is known for its high dissolving capacity and is known as the universal solvent. The most obvious medium in which to assess, monitor and control metal pollution is water (Ulrich Forstner, 1983). Groundwater is an important medium for assessment of pollution and also plays a very important role in almost all the food chains. Groundwater comprises an important component of the total water systems for human consumption. The quality of groundwater is the result of all processes and reactions that have acted on the water from the moment it condensed in the atmosphere to the time it is discharged by a well or spring. Therefore, the quality of groundwater varied with depth of the water table, seasonal changes and the range and composition of dissolved solids. The kind and concentration of dissolved solids depend on the source of salts and subsurface environment. The groundwater quality is very significant for mankind as it is directly associated with human welfare. It is now generally recognized that the quality of groundwater available in an area is as important as the quantity. Groundwater quality data provides an evidence to the geological history of the rocks, groundwater recharge, discharge, movement and storage (Walton, 1970). Groundwater is an important water resource in India for domestic, irrigation and industrial purposes. Hasty, unscientific and unsustainable groundwater development and management in the country due to ever increasing population, urbanization, industrialization demands for food security is altering the hydrological and geochemical environment of aquifers causing groundwater pollution. Groundwater pollution due to geogenic and anthropogenic factors makes the groundwater non-potable and utilization of this water leads to health problems. Endemic fluorosis is a major health issue occurring due to utilization of groundwater containing fluoride (Fawell et al., 2006; Johnson et al., 2008, UNICEF, 2008). Fluorosis in the country is commonly connected with aridity, rural areas, granitic, gneissic country rocks (Raghava Rao, 1974; Handa, 1988; Teotia et al., 2004; Fawell et al., 2006; Bhattacharyya, 2007, Johnson et al., 2008; Subba Rao, 2009).

1.2. Research Objectives:

The main objectives of the present study area are

- To study the sources, distribution of fluoride and its associated chemical parameters in the groundwater of Mudigubba, Nallamada, Kadiri Revenue Mandals of Anantapur district, Andhra Pradesh, through periodical monitoring for two seasons.
- Delineate fluoride zones and preparation of fluoride distribution maps.
- To study the geochemical behavior of fluoride with other parameters.
- To study the fluoride levels in groundwater and to highlight probable causes of contamination.
- To suggest defluoridation techniques.

1.3. Review of Literature:

1.3.1. International Status:

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Table 1: Comprehensive reviews of the Researchers in International level evaluating the impact of fluoride in groundwater on the environment

1.3.2. National Status:

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Table 2: Comprehensive reviews of the Researchers in National level evaluating the impact of fluoride in groundwater on the environment

CHAPTER - 2 STUDY AREA

The study area lies between longitudes 770 15’0” - 780 50’0” East and latitudes 140 0’0” -140 35’0” North and falls in the Survey of India Toposheet Nos: 57 F/14, F/15, F/16, J/3, J/4. Mudigubba, Nallamada, Kadiri revenue mandals of Anantapur District are situated in the Southeastern part of Andhra Pradesh, India. The important rivers in the district are Penna, Chitravathi, Vedavathi and Hagari. Maize, groundnut and cotton are mostly grown in the area of study. Paddy is also grown where there are some irrigation wells. The climate is hot and dry for the most part of the year. The area receives an average rainfall of 20 cm per year and the vegetation is, in general, sparse. The Archeans including Dharwars are traversed by numerous basic dykes which occur as elongated, narrow and intrusive bodies. These dyke rocks known, as dolerites are dark green to black in color and are very hard and compact.

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Figure 1: Location map of the study area (B.Muralidhara Reddy, Ph.D Thesis, 2015)

2.1. Geomorphology:

The major geomorphology of the study area depends on the geomorphic expression; relief, slope and top surface with soil or vegetation. The major geomorphic units of the study area are Denudational Hills, Dissected pediments, Pediplain, Alluvium.

Denudational Hills:

The geomorphic expression of the denudational hills is largely controlled by the lithological variations. The denudational hills are mainly formed by closepet granites. The structure of the hills consists of joints, factures/lineaments. The denudational hills constitute about 20 percent of the total geographical area. In the study area, the denudational hills occur in granites and gneisses. In the Northern part, denudational hills in schistose formation made up of low-grade metamorphic rocks mainly composed of amphibolite-hornblende schist and ferruginous quartzite of the Dharwar Super Group. The hill slopes are gentle to moderate and are characterized by low resistance to erosion.

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Figure 2: Denudational hills at (a) Mangalamadaka village of Mudigubba Mandal (b) Yerravankapalli village of Nallamada Mandal, Anantapur district (B.Muralidhara Reddy, Ph.D Thesis, 2015)

Denudational Hills in Sedimentary Rocks:

The denudational hills of these groups are made up of quartzite, cherty dolomite, shale, limestone and the associated basic intrusive of lower Cuddapah and Kurnool group of Precambrian age. These denudational hills in sedimentary formations occur in the N-E boundary of the study area as strike ridges of quartzite trending in NE-SW with a length of about 70 km with gentle dip slope towards the northeast.

Denudational Hills in Schistose Formations:

In the study area, the denudational hills are made up of low-grade metamorphic rocks mainly composed of amphibolite-hornblende schist, and ferruginous quartzite of the Dharwar Super Group.

Pediplain:

The zone of weathering is moderate to deep in many parts of the Pediplain. Pediplain refers to the flat or gently sloping surface, which is the end product of coalescence of several pediments at the foot of the hill slopes. In the study area, the pediplain is represented by a flat country with a gentle slope toward east and underlain by granite, gneiss, schists and sedimentary formations. Pediplains occupy nearly one-third of the study area and pertaining to a low-lying topography with less than 5 slopes and spreads over the weathered gneiss, schist, granites and sedimentary rocks. Pediplains covered with brown to black-colored coarse gravelly to sandy, clayey soils vary in thickness from 20 cm to 60 cm and in few places it extends up to 2 to 3 meters.

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Figure 3: Pediplain at Ralla Anantapur village of Mudigubba Mandal (B.Muralidhara Reddy, Ph.D Thesis, 2015)

Alluvium:

Alluvium is the fertile material deposited by different fluvial agents. In the study area of North of Pennar River, flood plain deposits are observed the major streams of pulletivanka and peddavanka. The material in these areas consists of sand and silty clays with an admixture of gravels towards the southern part of the area.

Climate:

The study area lies off the coast, does not enjoy the full benefit of the northeast monsoon and is being cutoff the by the high Western Ghats; the rainfall from the southwest, monsoon is also prevented.

Temperature:

Anantapur has a semi-arid climate with hot and dry conditions for most of the year. Monsoon begins in September and lasts until November with 250 mm of precipitation. The average high temperature is around 370C. Total annual rainfall is 60 mm. The period from February to May is the driest part of the year. The relative humidity is 50-60 percent in the mornings and 20-30 percent in the afternoons. It goes up during the southwest monsoon and retreats in monsoon seasons.

Soils:

The soils of the study area are predominantly of the black and red types. It is observed that 80% of the area is of black soil. Prominent study area is bound by brown loamy soil which is a weathered product of the underlying granites. The soils of the area are derived from granitic and its associated rocks and are generally alkaline (with a soil pH of about 9). The semi arid combined with the development of surface and underground run-off, low precipitation and scarce vegetation, high evaporation and heavy winds, is the principal factor that controls the physics and chemistry of the soils.

Maize, groundnut, cotton are commonly cultivated in this study area. Paddy is also grown where there are some irrigation wells.

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Figure 4: Black soils at (a) Pandulakunta village of Kadiri Mandal (b) Red soils at Sankepalli village of Mudigubba Mandal (B.Muralidhara Reddy, Ph.D Thesis, 2015)

2.2. Hydrogeology:

Groundwater in Achaean crystalline rocks like granites, gneisses and Dharwarian schists occurs in weathered and fractured zones. These rocks have developed secondary porosity. The degree of weathering in these formations is less than 20m and this zone is tapped extensively by the dug well and dug cum bore wells. The depth of open wells varies from 6.0 to 25.0 m below ground level (bgl) and depth to water level varies from 1.5 to 23 m bgl. The yield of dug wells varies from 10- 200 L/day for a pumping period of 3 to 6 hrs a day (CGWB 2012).

A drainage map based on the SOI toposheet (1:50,000 scale) and satellite imagery was prepared using Arc GIS-module. The number of streams present in the area is demarcated as shown in the adjacent map Figure 5. The study area is drained by Chitravathi river and its tributaries. Chitravathi river is a fifth order of streams with dendritic drainage pattern and flows from South to North. The main tributaries are Jilledubanda and Madduleru which are also seasonal and following the same pattern of river. The tanks/reservoirs are in more number in between the streams as runoff is highly variable and their distribution shows that they are structurally controlled.

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Figure 5: Drainage map of the study area (B.Muralidhara Reddy, Ph.D Thesis, 2015)

2.3. Geology:

Description of the various formations:

The lithology of the study area consists of pink granites, composite gneisses and Dharwars intruded by a few pegmatite dykes and numerous dolerite dykes.

Pink Granites:

The pink granites mainly consist of potash feldspars, plagioclase and relatively small amounts of quartz, biotite and hornblende. The rock is leucocratic, medium grained and non-foliated. Lineation can be traced on megascopic observation of the rock from the elongated grains of hornblende in a particular direction. In some places basic enclaves containing mafic minerals are present. Pink granites are more prominent in Lattavaram area.

Composite Gneisses:

Composite gneisses consist of a mixture of granites, grano-diorites with alternating bands of felsic and mafic minerals and often contain some mica, hornblende and some minor accessories. They are the result of granitisation in most parts of the area. The gneisses are also traversed by numerous white or bluish grey quartz vein lets.

Dharwars:

The Dharwars of this area consist of amphibolites and schistose formations and occur as a series of long and narrow highly folded strips. The amphibolites are composed of fine-grained hornblende, plagioclase and pyroxene as dominant constituents. They are fine grained, dark rocks in which shistocity is much less prominent than in gneisses. The schistose formations vary in composition from place to place, but mostly contain quartz and mica with accessory minerals like hornblende, orthoclase, and magnetite etc. The Dharwars are the oldest rocks formations and were subjected to different grades of metamorphism. The exposure of these rock types can be seen on the southern side of Hotur village.

Pegmatites and Aplites:

In many parts of the gneissic complex region, veins of the pegmatite and aplite are common. In the present area and their extent is very small and occur as dykes and veins and are observed on the north side of study area. They contain grains of quartz and feldspar. Aplites are fine-grained variety of pegmatites with grains of smaller size.

Quartz veins:

Quartz veins are common in granitic region and their length varies from a few feet to 2-3 km or more. Quartz veins exist trending NW-SE over a length of 4 km beyond the road joining at Mudigubba.

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Figure 6: Road cutting showing quartz veins near to Mudigubba village (B.Muralidhara Reddy, Ph.D Thesis, 2015)

Dolerite dykes:

The area under investigation contains numerous dolerite dykes and most of them are striking in E-W direction and a few in NE-SW and NW-SE directions. The dolerite dykes are characterized by the typical spheroidal weathering. They are fine grained, melanocratic and have high specific gravity than granites. They mostly contain mafic minerals like hornblende, enstatite, augite and the accessory minerals like magnetite etc.

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Figure 7: Geological map of the study area (GSI District Resource Map, Anantapur District, 1994)

CHAPTER - 3 MATERIALS AND METHODS

The study is carried out utilizing topographic maps, Garmin GPS MAP 76, Arc GIS 9.3 and investigations in the field. The Survey of India toposheets are used to prepare the basemap, drainage map and to understand the general nature of the study area. GPS is used to map the location of each sampling well and finally the results are taken to the GIS for further analysis. The field work included water level measurements and collection of water samples from bore wells, tube wells, open wells and the study of geological and geomorphological features of the area in general. Fifty water samples are collected in pre monsoon during April 2009- April 2014 and in the post monsoon fifty water samples are collected during September 2009 - September 2014. The samples are collected in pre-cleaned polyethylene bottles of two litre capacity. The water is left to run from the source for about 4 min to stabilize the electrical conductivity (Khaiwal and Garg, 2006). The groundwater samples are analyzed as described by American Public Health Association (APHA, 1995) procedure, and suggested precautions are taken to avoid contamination. The various parameters determined are pH, electrical conductivity, total dissolved solids, total hardness, calcium, magnesium, total alkalinity, carbonate, bicarbonate, chloride, sulfate, sodium, potassium, nitrate and fluoride. pH and EC are determined by pH meter, conductivity meter, TDS are determined by indirect method (Raghunath, 2003), Total Hardness, Ca2+, Mg2+, CO32-, HCO3- and Cl- are determined by titrimetry, whereas Na+ and K+ are determined by flame photometry (Systronic Model No.128), SO42- and NO3- are determined by spectrophotometric method. F- is determined by using ion selective electrode (Orion 4 star ion meter, Model: pH/ISE). All the experiments are carried out in triplicate and the results are found reproducible within a ±3% error limit.

The site of every well is taken the results of every parameter analyzed are added to the concerned wells. Extended module of Arc GIS is used to discover the spatio-temporal behavior of the fluoride parameters. The area covering Mudigubba, Nallamada, Kadiri revenue mandals of Anantapur District is situated in the Southwestern part of Andhra Pradesh. The latitude and longitude of the study area are given in Table 3, 4 and 5.

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Table 3: Location of study areas in Mudigubba Mandal of Anantapur District

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Table 4: Location of study areas in Nallamada Mandal of Anantapur District

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Table 5: Location of study areas in Kadiri Mandal of Anantapur District

3.1. Field work:

The field work is conducted in post monsoon groundwater samples are collected during September 2009 - September 2014 and in pre monsoon, the groundwater samples are collected during April 2009 - April 2014. Some parameters are measured in the field itself and water samples collected are brought back for analysis at Geochemical Laboratory, Yogi Vemana University, Kadapa.

3.2. Sample Collection:

A total of 50 samples are collected in pre monsoon during 2009 - 2014 and 50 samples in post monsoon during 2009 - 2014 from different sites of Mudigubba, Nallamada, Kadiri revenue mandals of Anantapur District. Sample location map of the study area is shown in Figure 8.

Samples collected from Mudigubba Mandal area: Peddachigullarevu, Timmanayanipalem, Gandlavandlapalle, Malakavemula, Budanampalle, Thappetavaripalle, Mukthapuram, Kondavanllapalli, Nagireddipalle, Brahmadevaramarri, Ellareddipalle, Bandlapalli, Marthadu, Sankepalli Brahmanapalli, Dorigallu, Kondagattupalle, Sankepalle, Chagapuram, Jonnalakothapalle, Mangalamadaka, Devaragudipalle, Uppalapadu, Ralla Anantapuram, Mallepalle, Chinnakotla, Gunjepalle, Nakkalaguttapalle villages. Samples collected from Nallamada Mandal area: Pulagampalle, T Sautakuntapalle, Reddipalle, Nallamada, Kurumala, Donnikota, Vellamaddi, Gopepalle, Charupalle, Vankarakunta, Sanevaripalli, Bapanakunta villages. Samples collected from Kadiri Mandal area: Chippalamadugu, Kadirikuntlapalli, Mutyalacheruvu, Kalasamudram, Eguvapalle, Motukupalle- Kadiri, Kondamanayanipalem, Erradoddi, Alampuru, Saidapuram, Kavulepalli, Battulapalli, Kuttagulla, Kadiri, Patnam, Kadiri Brahmanapalli, Chelamkuntlapalli, Pandulakunta villages.

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Figure 8: Sample location map of the study area (B.Muralidhara Reddy, Ph.D Thesis, 2015)

3.3. Experimental Procedures:

3.3.1. Determination of Fluoride:

Ion-selective electrode (ISE) is a one of the widely used electrode for the testing of the fluoride that rely on the unique role of electrochemistry which plays as an interface between chemical systems and electronic devices that display and record data. The key to using this interface has been the development of electrodes that are selective sensitive to the kinds of chemicals of interest. These electrodes are called ion-selective electrodes because of their ability to respond to certain specific ions while ignoring others. Ion-selective electrode systems are composed of a sensing electrode, a reference electrode and a meter. Reference electrode used for ISEs are the sleeve-type electrodes. In the “single junction” reference electrode, the inner filling solution is silver chloride (AgCl), and in the “double junction” reference electrode the filling solution has an ion react with the ion analyzed.

The fluoride concentration in groundwater is determined electrochemically, using the ion selective electrode method. The electrode used is an Orion fluoride electrode, coupled to an Orion electrometer. Standards fluoride solutions (0.1-10 mg/L) are prepared from a stock solution of sodium fluoride (100 mg/L). To estimate the concentration, the water samples are diluted with equal volumes of total ionic strength adjustment buffer (TISAB) of pH 5.2 before fluoride estimation. The composition of TISAB solution was as follows: 58 g NaCl, 4 g of CDTA (Cyclohexylene diamine tetra acetic acid) and 57 mL of glacial acetic acid per litre (Khaiwal and Garg, 2006).

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Figure 9: Ion selective electrode (Orion 4 star ion meter, Model: pH/ISE) (V.Sunitha et al, 2014)

3.3.2. Determination of other parameters, methods and instruments:

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Table 6: Analytical methods adopted for physicochemical analysis

As mentioned in the Table 4 the methods and instruments used for the determination of the various parameters as follows: pH and EC are determined by pH meter, conductivity meter, TDS are determined by indirect method (Raghunath, 2- - - 2003), Total Hardness, Ca2+, Mg2+, CO3 , HCO3 and Cl are determined by titrimetry, whereas Na+ and K+ by flame photometry (Systronic Model No.128), SO42- and NO3- are determined by spectrophotometric method. Fˉ is determined by using ion selective electrode (Orion 4 star ion meter, Model: pH/ISE).

CHAPTER - 4 RESULTS AND DISCUSSIONS

Fluorine is the most reactive and electronegative of all known elements. It is the thirteenth most abundant element available in the earth’s crust. Its abundance in the continental crust is about 626 μg/g. It rarely occurs free in nature, therefore in minerals, fluorine is generally found as the fluoride ion (Fˉ). Fluoride has strong affinity to combine with other elements to produce compounds known as Fluoride. The problem of fluorosis has been known in India for a long time. The disease earlier called “mottled enamel” was first reported by Viswanathan (1935) to be prevalent in human beings in Madras Presidency in 1933. Mahajan (1934) reported a similar disease in cattle in certain parts of old Hyderabad state. However, Shortt (1937) was the first to identify the disease as “fluorosis” in human beings in Nellore district of Andhra Pradesh.

Fluorine occurs mainly free fluoride ion in natural waters, though fluoride complexes of Al, Be, B and Si are also encountered under specific conditions. The assimilation of fluoride into the human body through potable water at the level of 1 mg/L enhances bone development and prevents dental caries. The maximum tolerance limit of fluoride in drinking water specified by the World Health Organization (W.H.O, 1984) is 1.5 mg/L.

4.1. Beneficial effects:

Fluoride ingestion at moderate levels can reduce the incidence of dental caries and, under certain conditions, promote the development of strong bones (Kaminsky et al., 1990; Heller et al., 1997; Yiming et al., 2001; Rao, 2003; Harrison, 2005; Edmunds and Smedley, 2005; Doull et al., 2006). Hydroxyapatite (Ca10(PO4)6(OH)2) is the mineral deposited in and around the collagen fibrils of skeletal tissues to form bone. When fluoride is present, it replaces hydroxyl ion in the hydroxyapatite structure to form fluorapatite (Ca10(PO4)6F2 or Ca10(PO4)6OH,F). This substitution causes a reduction in crystal volume, an increase in structural stability, and a decrease in mineral solubility (Aoba, 1997). Ever since the beneficial effect of fluoride was recognized during the 1930s, researchers have attempted to identify an optimal fluoride concentration in drinking water so as to reduce dental caries. This optimal level is obviously dependent upon the amount of water consumed on a daily basis and any additional sources of fluoride in the diet.

4.2. Impact of fluoride on human health:

Increasing population in developing countries and industrialization of the advanced countries are creating environmental problems of enormous dimensions. Fluoride contamination of drinking water is one of such problems worldwide. More than 23 countries in the world, including India, have problems with Fˉ in the drinking water (Susheela, 1993). The problems are most pronounced in the states of Andhra Pradesh, Bihar, Gujarat, Madhya Pradesh, Punjab, Rajasthan, Tamil Nadu and Uttar Pradesh (Sherlin and Verma, 2000). In India, about 62 million people are at the risk of developing fluorosis from drinking groundwater with high fluoride content (Andezhath et al., 1999). Dental and skeletal fluorosis has been reported in many countries of the world, notably in African countries (Manji et al., 1989); Ghana (Apambire et al., 1997); South Africa (Cube et al., 2005), India, (Susheela et al., 1993; Mukherjee et al., 1995; Gupta et al., 2005; Rajashree et al., 2007); China (Ren and Shugin, 1988; Yong and Hua, 1991); Japan (Hamamoto, 1957), Iran (Zohouri et al., 2000); Canada (Boyle and Chagnon, 1995). In these countries fluoride levels in the range of 10-60 mg/L in groundwater have been reported.

In India fluorides are widely distributed in waters of different geographical regions having diverse hydrogeological settings. Incidence of fluoride is reported to occur partially in all types of rock formations, namely the crystalline rocks of the peninsular shield, igneous and metamorphic rocks of Rajasthan, volcanic rocks of west central India and even unconsolidated quaternary alluvium overlying the older formations in many places (Raghava Rao, 1974). In Tamil Nadu, 3,555 habitations have been identified as fluoride affected settlements spreading over Vellore, Dharmapuri, Trichy, Karur, Salem (Jayaprakash et al., 2002). The highest fluoride concentration of 28 mg/L has been found in sub-surface water in Andhra Pradesh (Chari, 1976). In Rajasthan, high concentrations of the toxic ion in waters is reported and a maximum of 20 mg/L is recorded. Several well waters in Gujarath contain fluoride ranging from 0.1-11 mg/L (Viswanadham, 1976). A maximum content of 14 mg/L is reported in Punjab in Bathinda District (Singh et al., 1962). In Karnataka several groundwaters in Dharwar and Raichur district have fluoride content in the range of 0-7 mg/L (Ziauddin, 1974). Surface waters are reported to have fluoride mostly below 1 mg/L, except in some areas of Andhra Pradesh and Rajasthan. In these states, a few rivers and streams are found to contain higher concentrations. Some of the thermal springs in India contain fluoride ranging from 10 to 17 mg/L (Bose et al., 1974, Mahendra, 1975). Most of these springs occur along the Himalayan orogenic belt, in east-west tectonic lineaments in the Precambrian of Bihar, West Bengal, and along the West Coast. It is pertinent to note that no systematic investigations have been conducted to clearly delineate various geochemical factors related to high incidence of the toxic ion in waters. In western part of Ghaziabad district of Uttar Pradesh and northern part of Faridabad district of Haryana, high concentrations of fluoride are found (Shadab et al., 2004).

4.2.1. Dental Fluorosis:

Generally ingestion of water having a fluoride concentration above 1.5-2.0 mg/L may lead to dental mottling, an early sign of dental fluorosis which is characterized by opaque white patches on teeth. In advanced stages of dental fluorosis, teeth display brown to black staining followed by pitting of tooth surfaces. Dental fluorosis produced considerable (tooth deterioration) and significant physiological stress for the affected population. Dental fluorosis is endemic in 14 states and 1,50,000 villages in India. The problems are mostly pronounced in the states of A.P., Bihar, Gujarat, M.P., Punjab, Rajasthan, Tamil Nadu and Uttar Pradesh (Pillai and Stanley, 2002). Types of mottling are shown in Figure 10.

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Figure 10: Types of Mottling (V.Sunitha et al, 2008)

4.2.2. Skeletal Fluorosis:

Skeletal fluorosis may occur when fluoride concentrations in drinking water exceed 4-8 mg/L, which leads to increase in bone density, calcification of ligaments rheumatic or arthritic pain in joints and muscles along with stiffness and rigidity of the joints, bending of the vertebral column and excessive bone formation or osteosclerosis, a basic symptom of skeletal fluorosis (Teotia and Teotia, 1992); while excess Fˉ may include hypocalcaemia (Sherlin and Verma, 2000; Teotia and Teotia, 1994; Pius et al., 1999; Ekambaram and Vanaja, 2001). Crippling skeletal fluorosis occurs when a water supply contains more than 10 mg/L (W.H.O, 1984; Boyle and Chagnon, 1995).

Figure 11: Extent of Skeletal Fluorosis (V.Sunitha et al, 2008)

4.3. Total fluoride Ingestion:

It is generally agreed that chronic fluoride toxicity depends upon the total amount of the fluoride ingested. Fluoride ingested through foods appears to be relatively small and constant, and variations in the total amount of fluoride ingested depend largely upon (a) the concentration of fluoride in drinking water, and (b) the total amount of water ingested. The amount of water ingested is itself dependent upon a number of variables like body size, food habits, environmental temperature and extent of physical activity. Factors which promote increased ingestion of water obviously increases the total fluoride ingested.

In our country, most urban areas are provided with protected drinking water, and the fluoride content of such water has been found to be well below 1 mg/L. In most parts of rural India, populations depend exclusively on well water for drinking purposes. These rural populations are predominantly agriculture labourers. It is primarily in these populations that endemic skeletal fluorosis is a problem. Rural populations work in the fields and are engaged in heavy manual labour, sweat profusely and therefore consume large quantities of water. It has been estimated that, during the hot summer season, agricultural labourers drink as much as 6 to 8 litres of water a day. Even during the non summer months, consumption of water by such population groups has been found to be between 3 and 4 litres a day.

In addition to the ingestion of water directly, habitual Indian dietaries contain high amount of water, particularly when all the staples are cooked in water. Many of the food items that are eaten along with the staple are either liquid or semi liquid in consistency, containing a considerable amount of water.

4.4. Nutritional Status:

Epidemiological observations have suggested that nutritional status may influence chronic fluoride toxicity. Results of diet surveys have indicated that low levels of calcium and vitamin C in the diet may be related to the severity of endemic fluorosis. Controlled studies carried out at the National Institute of Nutrition, using monkeys have, in fact, provided experimental proof that low amounts of calcium and low amounts of vitamin C in the diets predispose to the development of experimental skeletal fluorosis. The precise mechanism is, however, not known.

In addition to the role of these specific nutrients, body size is an important factor in determining the safe level of fluoride. Fluoride is known to be a bone- seeking element. For a person with a small stature with a consequent small skeleton, the amount of total fluoride that would be toxic may be expected to be less than that for a person with a big stature with a relatively big skeleton. The average weight of a well nourished western adult is around 70 kg., while the mean body weight of an agricultural labourer in our country, who is exposed to the risk of skeletal fluorosis rarely exceeds 55 kg.

4.5. Dietary Factors:

The fluoride of food items depends upon the fluoride contents of the soil and water used for irrigation, therefore the fluoride content of the food items may vary from place to place. It has been observed that the common foodstuffs have the following contents of fluorine (expressed in ppm)

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Table 7: Contents of fluorine (expressed in ppm)

4.6. Factors affecting the natural fluoride concentrations

The concentration of fluoride ions in natural water depends upon several factors like

- The accessibility of circulating water to these minerals.
- Distribution of easily weathered fluoride bearing minerals.
- The extent of fresh water exchange in an aquifer.
- Evaporation and Evapotranspiration.
- Formation of ion pairs such as CaSO4 , CaHCO3 etc.
- Complexing of fluoride ion with aluminum, beryllium, ferric iron and series of mixed fluoride hydroxide complex with Boron (Hem, 1991).

4.6.1. Sources:

Fluorine occurs abundantly in the earth’s crust as component of rocks and minerals as in high calcium granite (520 mg/L), in low calcium granite (850 mg/L), in Alkali rocks (1200-8500 mg/L), in shales (720 mg/L) and (270 mg/L) in sandstones (Karunakaran, 1974). The main sources of fluoride in natural waters are fluorite (CaF2), fluorapatite (Ca10(PO4)6F2,), cryolite (Na3AlF6), magnesium fluoride (MgF2) and as replacement of ions of crystal lattice of micas, and many other minerals. Fluorine with its abundance at 1600 (in relation to Si at 106) in the cosmos is indicative of its widespread occurrence when one studies its distribution, which has been estimated as follows:

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Table 8: D i stribution of fluorine in different rock types (after Karunakaran, 1974)

The main contribution of fluorine in igneous rocks is from fluorite and fluorapatite apart from topaz, amphibole and micas. In sedimentary rocks it is related to fluorapatite while some amount is absorbed by the clay minerals. Its enrichment from 12 mg/L in Dunite to 1200 mg/L in alkali rocks is related to its progressive concentration in acidic rocks and the fluid phase. Solubility studies have indicated that transport of fluorine in aqueous solutions is dependent on the solubility of CaF2. Further the quantity of fluorite dissolved or precipitated is also dependant on the presence of other electrolytes in aqueous solutions which are partially ionised. In experiments connected with possible conditions related to hydrothermal solutions, the ratio of the concentration of calcium to that of fluoride ions in solution appears to be important.

Studies on the fixation of fluorine in sedimentary rocks have indicated that 40% of fluorine is expelled during diagenesis and lithification but nothing is known about what happens to the expelled fluorine. The relative abundance of fluorine in deep sea clays and carbonates is also interesting. Remobilisation is naturally associated with the metamorphic, palingenetic and anatectic processes with the fluid phase resulting in concentration of fluorine rich minerals. In this regard it is particularly interesting to point out that the association of barite-calcite- fluorite, association of boron with fluorine minerals indicate a volcanogenic association apart from its association with lithium and tin indicating late stage hydrothermal products. An important source of fluorine pertains to the rock phosphates which are increasingly being used as fertiliser in the efforts to achieve a green revolution all over the world. It is pertinent that the minerals fluorapatite and francolite in rock phosphates carrying the fluorine are also generally associated with pyrite often with Uranium, Vanadium (such as Korgai, Nigalidhar of Himachal Pradesh) indicating geochemical affinities. It has also been noticed that the oxides of Uranium, Thorium, Cerium and Calcium, fluoride has face centered cubic lattice with a cell size of 5-50 A0 and as such tend to occur in the same geological environment. This is also an important practical aspect in looking for fluorine bearing minerals in radioactive mineral prospects.

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4.7. Fluoride:

Table 9: Some Fluorine bearing minerals

Fluoride concentrations in the study area varied between 0.5 to 5.51 mg/L in 2009 during the pre monsoon and from 0.5 to 5.5 mg/L during post monsoon. In 2010, Fluoride content in the study ranges from 0.5 to 5.53 mg/L in pre monsoon and from 0.5 to 5.51 mg/L during post monsoon. In 2011, the fluoride content ranges from 0.6 to 5.55 mg/L during pre monsoon and from 0.5 to 5.52 mg/L during post monsoon. In 2012, the fluoride content in the study area ranges from 0.7 to 5.58 mg/L during pre monsoon and from 0.6 to 5.56 mg/L during post monsoon. In 2013, the fluoride content in the study area ranges from 0.8 to 5.6 mg/L and from 0.7 to 5.58 mg/L during the post monsoon season. In 2014, the fluoride content in the study area ranges from 0.9 to 5.7 mg/L during pre monsoon and from 0.8 to 5.6 mg/L during the post monsoon season.

In the study area high fluoride (Fˉ) concentration within the desirable limit <1.5 mg/L is observed in Bandlapalli, Marthadu, Bramhadevaramarri, Dorigallu, Ellareddipalli, Sankepalli, Sankepalli Brahmanapalli, Mudigubba, Chagapuram, Kondagattupalli villages. Fluoride concentration (1.5-3.0 mg/L) is observed in Budanampalli, Peddachigullarevu, Gandlavandlapalli, Kondavandlapalli, Jonnalakothapalli, Mukthapuram, Gunjepalli, Mangalamadaka, Malakavemula, Nagireddipalli, Tappetavaripalli, Timmanayanipalem villages. Fluoride concentration >3.0 mg/L is observed from Uppalapadu, Ralla Ananthapuram, Chinnakotla, Mallepalle, Sanevaripalli, Nakkalaguttapalle, Devaragudipalle villages.

4.7.1. Dental Fluorosis:

The groundwater in free from colour and odour and taste in slightly saline. The fluoride content in groundwater varied greatly in different villages. Fluoride concentrations (mean ± standard deviation) of more than 1.5 mg/L and its relationship with the severity of dental fluorosis among with school children in the villages are given in the tables 10-12. Selected mandals i.e. Mudigubba, Nallamada and Kadiri lie in southeastern part of Anantapur District. Groundwater is the only source of drinking in these villages. The rate and extent of fluorosis in southeastern part of Anantapur District increases with increase of fluoride level in drinking water and age. High concentration of fluoride in groundwater is common in the fractured hard rock zone with pegmatite veins (Ramesam and Rajagopalan, 1985). High fluoride level in drinking water causes dental decay and physiological deformations. Manifestation of dental fluorosis in Bapanakunta village of Anantapur District is shown in Figure 14.

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