A Case Study From Ramannapeta Mandal, Nalgonda, Telangana, India: Fluoride Contamination of Ground Water

The groundwater quality evaluation for uoride element was studied in Ramannapeta Mandal, Nalgonda District, and Telangana State, India. The water samples were collected in pre and post monsoon seasons in the year of 2015-2016 from hand pumps bore wells or dug wells in the villages of Ramannapeta Mandal. The collected water samples were analyzed within a week. The Spatial distributions of uoride maps were prepared with the help of the Remote Sensing Imaginary (RSI) and Geographical Information System (GIS) techniques. The range of uoride in the study area varied from 0.6 to 5.6 ppm whereas the maximum permissible limit in drinking water is 1.5 ppm (As per Bureau of Indian Standard (BIS) guideline-IS: 10500: 1991). The high contamination 4.0-5.5 ppm of uoride in drinking water was observed in Siripuram, Dubbaka villages. During the study, it was found that the most of villages in Ramannapeta Mandal are affected with high uoride content in drinking water in the range of 1.5-3.0 ppm. Nalgonda district including Ramannapeta Mandal is underlain by different rocks such as granites (80%), gneisses, dolerite, dykes (10%), older metamorphic and intrusive (10%). The lock of freshwater exchange due to periodical drought conditions, the granitic rocks and the arid climate of the region are the factors for the higher incidence of uoride in the groundwater resources. The constructions of rain water harvesting structures are proposed to minimize uoride content in drinking water.


Introduction
Groundwater is the major source for drinking in most parts of the world, as it is available cheaply near to door step and free from pathogenic bacteria. Good quality of drinking water is essential for human life. The goal of Government is to provide every person with adequate safe water for drinking, cooking and other domestic uses. The spatio-temporal variations in rainfall, regional distribution in geological formations and geomorphic composition of various units have led to uneven occurrence and distribution of groundwater resources.
There are few chemical contaminations of drinking water that can lead to severe health problems. Especially uoride is a major concern; the recommended concentration of uoride in drinking water is 1.5 mg/l ( WHO;1984). Seawater typically contains about 1 mg/l of F − where rivers and lakes generally exhibit less than 0.5 mg/l. Low or high concentrations of uoride is possible in groundwater, depending on the existence of nature of the rocks and uoride-bearing minerals. The high uoride containing water occurs in large and extensive geographical belts associated with sediments of marine origin in mountainous areas, volcanic rocks, granitic and gneissic rocks.
In India, high groundwater uoride content associated with igneous and metamorphic rocks such as granites and gneisses have been reported. Endemic uorosis is still a challenging and extensively studied national health problem. The most seriously affected areas in India are Telangana, Andhra Pradesh, Punjab, Haryana, Rajasthan, Gujarat, Tamil Nadu, Orissa, Punjab and Uttar Pradesh etc (Kumaran, et al., 1971;Teotiaet al., 1984). The high concentration of uoride in drinking water was reported in 19 states and territories which include 177 districts. The highest concentration observed to date in India is 48 mg/l in Rewari District of Haryana.
Groundwater is the primary source of potable water supply in rural India. It is not possible to estimate the number of people at risk with high uoride in drinking water. This is because of the di culty of sampling groundwater from India's many millions of hand pumps. In these states, 10 to 25% of the rural population has been estimated to be at risk, and approximately 60-70 million people are in uenced by uoride contaminated groundwater. About 60% of land comes under irrigation of groundwater; this is also other main reason of producing high uoride food. The rainfall is the source of recharge of groundwater, geomorphology plays a vital role in controlling distribution of precipitation, runoff, and in ltration contributing to recharge.
Fluorosis is an endemic disease. An endemic disease found in a certain geographic region or in a speci c race of people. The uoride in potable water not exceed to1 mg/L. High F − concentration in drinking water is main concern, because of its negative impact on human health. The uoride arises into the water from the geological crust. The main potential health risks from uoride are considered to be uorosis or bone disease. Based on body tissues in uenced by uoride, uorosis is categorized into Dental, Skeletal and Non-Skeletal uorosis. Irrespective of age and gender, anybody can become victims of Fluorosis. Fluoride content range in drinking water and how it effects on human health is listed in Table 1. The average annual rainfall is 649 mm both by northeast and southwest monsoons. 80% of the people from the study area use bore and dug wells water for drinking, cooking and other domestic uses. The depth of the bore wells varied between 90 and 300 feet. The area around228 sq.km was covered and 36 water samples were collected in cleaned and sterilized glass bottles. All the collected samples were analyzed within week in the laboratory.

Remote Sensing and GIS
The Remote Sensing imagery with its synoptic coverage acts as a tool for nding suitable solution when combined with conventional data. Hydro-geomorphic maps were prepared by integrating the lithology, landforms, and structural fabric and hydrology layers using Remote Sensing and GIS techniques, the scale range of 1:10,000. The satellite data has been used for updating of drainage and surface water bodies. The IRS P6 LISS-IV is a multi-spectral high resolution camera with a spatial resolution of 5.8m at nadir. Satellite image of the study area is shown in Fig. 2 From the satellite imaginary studies, it was observed that 76% of the study area covered by major landforms in granitic rocks which are pediplains. About 14% of the area covered by pediment and Inselberg zone, 4% of the area covered by valley zones and the remaining area covered by highly weathered hills and water bodies.

Drainage & Rainfall
The drainage pattern of the study area is mainly dendritic drainage, all the water streams ow from Southwest to Northeast direction. Nalgonda district has an average rainfall of 649 mm during years of 2004-2015.The most rainfall is received through the Southwest monsoon during the period of June-September.
An average annual temperature of the study area varies from 17°C in winter (December-January) to 45°C in summer (March-May).

Geology of the study area
The study area underlined by the variety of granite and gneisses rocks which are intruded by dolerite dykes/quartz veins. Granite, old and hard rocks, are widely distributed throughout the area. The nature of granite varies in the study area, grey to pink, medium to coarse granite, porphyritic or non-porphyritic and massive. The granitoid rocks are complex which associated with profuse injections of aplite, ne grained quartzo-feldspathic veins and pegmatite, quartz veins and reefs.
From the stratigraphical studies, the study area predominantly exposes rocks of Peninsular Gneissic Complex (PGC) along with enclaves of basic dykes (Proterozoic). The PGC includes mainly two varieties of granitoid rocks i.e. older granite gneiss and younger granite (alkali feldspar). The most of the lineaments/faults identi ed are aligned in the direction of Northeast to Southwest and North-northeast to South-southwest. Generally dolerite dykes appear to be very hard and compact and poorly devoid of fractures, whereas the Pegmatite veins / Quartz reefs are highly fractured.

Hydrogeology
The majority of the area occupies with hard rock like gneissic complex which includes granite/gneisses, dolerite dykes. Very little area covered with other formations. Even though, the absence of primary porosity in hard rock formations, the aquifer system developed because of secondary porosity due to various tectonic disturbances and weathering activity. The deeper aquifer system developed due to major faults, joints, fractures, crevices, shear zones etc. It was observed that the groundwater prospect of the study area is in the range of 100-200 lpm in moderately weathered granite gneiss/granitoid rocks and valleys whereas the range is 50-100 lpm in shallow weathered granite gneiss/granitoid rocks and valleys. The availability of groundwater is in the range of 10-50 lpm and low to poor (0 to 10 lpm) in the pediment zones of granitic rocks and highly dissected hills/plateaus respectively.

Materials And Methods
Groundwater samples were collected in polyethylene bottles from pre-identi ed places of the villages of Ramannapeta Mandal. All the samples were collected in pre and post monsoon season, 2015-2016.The collected samples were analyzed within a week. Fluoride was analyzed using Lovibond PC Spectrophotometer (SN 100537, Germany) following the method of SPANDS colorimetric method. Various other water quality parameters such as pH, electrical conductivity, total dissolved solids, total hardness, total alkalinity, sodium, potassium, calcium, magnesium, carbonate, bicarbonate, chloride, and sulfate concentrations were measured. The techniques and methods followed for the collection, preservation, analysis, and interpretation are those given by (Rainwater and Thatcher  The data is segregated into pre and post monsoon seasons based on date of collection of samples and these results are listed in Table 2 and Table 3 respectively.  . Fluoride in the water ranged from 0.30 to 3.00 mg/Lin the study area with an average of 1.42 mg/L was found. An average value of uoride for all the sources is calculated for each habitation. From the collected data, the uoride distribution maps were prepared using Spatial Analyst Tools (SAT)adopting Inverse Distance Weightage (IDW) method. Based on uoride content in drinking water, the map is divided into three zones. That are Desirable (< 1.00 mg/L), Permissible (1.50-3.00 mg/L) and Non Potable (> 3.00 mg/L). The uoride content in groundwater varied in the study area due to the accessibility of uorine-bearing minerals to the circulating water, the leaching and weathering activities. The uoride concentration is more in shallow or moderately weathered Pediplains, Alkali Feldspar Granite, and Grey Biotite Granite which located in western part and around the mandal. Even, high concentration of uoride was observed at isolated places in granite and dolerite, the west side of the mandal. Fluoride in the exogenic cycle of the uorosis belt is almost contributed by the granitic and pegmatitic rocks. Above discussed uoride bearing minerals of these rocks are the acid soluble minerals such as uorite, uorapatite, hornblende, mica, epidote etc. These minerals are responsible for high concentration of uoride in natural waters, as they release uoride under normal temperature pressure conditions. Furthermore, pH of water increases the releasing of uorides from uoride-bearing minerals during the weathering processes within the aquifers (Saxena and Ahmed 2001).
The uoride minerals are abundant in the granite and gneiss rocks present in the mandal. Hence, the concentration of uoride in groundwater is the highest in those villages present on the northern and southern parts and in isolated patches of the study area. The distribution of uoride in groundwater depends on the amount of uoride in the rocks or soils, the contact time of the water with the rocks, temperature, rainfall, vegetation and oxidation and reduction reactions. The percolating water dissolves the salts from soils, the uoride concentration of groundwater may be higher than that during dry periods. The other factor is the amount of uoride in the water depends on the degree of granitic rock weathering of the area (APSRAC, 1997).

Hydrogen Ion Concentration (pH)
pH is a measure of the relative acidity or alkalinity of a sample. It is equal to the negative logarithm of the hydrogen ion activity in moles per liter (-log aH+). The study area groundwater samples have EC in the range 600 to 5700 with an average of 2348 µS/cm. The maximum limit of EC in drinking water is prescribed as 1,500 µs/cm as per WHO standard. About half of the samples collected showed EC values more than permissible limit. EC distribution is found to be similar to that of Cl-, SO42-, HCO3-and K + distribution patterns, indicating it is positively correlated with these ions.

Total dissolved Solids (TDS)
TDS refers to the total dissolved solids present in the water. Measurement of conductivity is often used as an indirect method of estimating the dissolved solids content of a solution. (Chapra, 1997) reports a relationship between total dissolved solids and conductivity.
As per the (BIS, 2003) speci cation for drinking water, 500 mg/l is treated as desired limit and 2000 mg/l of TDS is treated as maximum permissible limit. Higher concentrations of TDS decrease the palatability and may cause gastro-intestinal irritation in human and may also have laxative effect particularly upon transits. It is a well-known fact that the recharging water during its downward movement through the zone of aeration dissolves mineral matter thus enriching itself in total dissolved solids. This dissolution continues even in the zone of saturation due to rock-water interaction during the residence time of groundwater in the host rock. The enrichment of TDS is also governed by evaporation of water. In this study area all the samples have TDS between 384 and 3648 mg/l with an average value of 1503 mg/l.

Permeability Index (PI)
The Permeability Index (PI) values also depicts suitability of groundwater for irrigation purposes, since long-term use of irrigation water can affect the soil permeability, in uenced by the Na + , Ca 2+ , Mg 2+  US salinity Laboratory diagram: The US Salinity Laboratory Staff, 1954) proposed a diagram for studying the suitability of groundwater for irrigation purposes by using the SAR values on vertical axis and electrical conductivity on horizontal axis.
The diagram is divided into four distinct classi cations both horizontally and vertically. On horizontal axis the salinity hazard classi cation is divided into low salinity (C1), medium salinity (C2), high salinity (C3) and very high salinity (C4). Likewise on vertical axis sodium hazard classi cation is divided into low sodium water (S1), medium sodium water (S2), high sodium water (S3) and very high sodium water (S4). Figure 7 shows Richards Diagrams classi cation of irrigation water during pre and post monsoon period respectively.
It is clear from the Fig. 7 that the groundwater samples of the study area out of 36samples fall under Majority of samples are fall in the S1C3 and S2C4 category in pre and post-monsoon periods.

Recommendations & observations
It is important to educate every citizen about the uoride toxicity and the necessity of avoiding uoride consumption. The intake of uoride above the permissible limit in drinking water is the major reason for uorosis disease in some parts of the study area. It is encouraged that Taking safe drinking water with su cient dietary food in order to avoid uorosis disease. It should be identi ed the uoride affected areas with the help of scienti c mapping and watersheds are proposed in the area. It is important to look for holistic and people-centred approaches for water management.
The occurrence groundwater in the study area is completely controlled by rainfall and canal whereas the quality of the water controlled by the terrain features like landforms, lithology, soil, drainage, topography, etc. The information provided in the groundwater prospect zones helps in identifying the areas suitable for arti cial recharge. Tremendous pressure on groundwater for domestic, agriculture and industrial uses results in pollution of groundwater resources. In the future, the limited resources will not be able to meet out the water demand qualitatively and quantitatively for next generation. With scienti c guidelines, watersheds to be constructed on Fast Track basis. Groundwater management and arti cial recharge structures will be helpful for recharging of groundwater to make the existing bore wells and dug wells sustainable. Based on uoride content in groundwater the map is divided into three zones. The high uoride content in the groundwater is correlated with the uoride bearing rocks of the study area.It was observed that uoride contamination in the water is more in high yielding Hydrogeomorphic units as compared to low yielding Hydrogeomorphic units. The periodical drought and arid climate of the region increases incidence of uoride in the groundwater resources. The constructions of rain water harvesting structures are proposed to minimize uoride content in drinking water.  Figure 1 The location map of the present study area   Spatial distribution of uoride during pre-monsoon season. Piper classi cation of the study area US salinity Laboratory diagram