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Hydrogeochemical evaluation of high-fluoridegroundwaters: a case study from Mehsana District,Gujarat, IndiaS. D. DHIMAN a & ASHOK K. KESHARI ba Department of Civil Engineering , Birla Vishvakarma Mahavidyalaya , VallabhVidyanagar, 388 120, Gujarat, India E-mail:b Department of Civil Engineering , Indian Institute of Technology Delhi , Hauz Khas, NewDelhi, 110 016, India E-mail:Published online: 19 Jan 2010.

To cite this article: S. D. DHIMAN & ASHOK K. KESHARI (2006) Hydrogeochemical evaluation of high-fluoridegroundwaters: a case study from Mehsana District, Gujarat, India, Hydrological Sciences Journal, 51:6, 1149-1162

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Hydrological Sciences–Journal–des Sciences Hydrologiques, 51(6) December 2006

Open for discussion until 1 June 2007 Copyright © 2006 IAHS Press

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Hydrogeochemical evaluation of high-fluoride groundwaters: a case study from Mehsana District, Gujarat, India S. D. DHIMAN1 & ASHOK K. KESHARI2

1 Department of Civil Engineering, Birla Vishvakarma Mahavidyalaya, Vallabh Vidyanagar 388 120, Gujarat, India dhimansanjay18@hotmail.com

2 Department of Civil Engineering, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110 016, India akeshari@hotmail.com Abstract Groundwater quality problems have emerged in many geographical areas due to natural environmental processes and human intervention in the geosystems. Hydrogeochemical appraisal of fluoride contaminated groundwater in Mehsana District, Gujarat State, India is carried out by means of groundwater quality investigations together with X-ray diffraction analysis of soil samples in the delineated high fluoride areas. Results show that fluoride has negative relationships with calcium, whereas relationships with sodium, alkalinity and sulphate are positive. Results obtained from aqueous speciation modelling using PHREEQC reveal that the groundwater is undersaturated with fluorite and oversaturated with calcite. The factor analysis indicates that sodium plus potassium bicarbonate ground-water have high factor loading for fluoride, whereas that for calcium chloride and magnesium chloride groundwater is low. The plausible geochemical reactions in the study area are precipitation of calcite and dissolution of dolomite, carbon dioxide and sulphate minerals with ion exchange. Key words aqueous speciation modelling; fluoride; groundwater; Gujarat, India; hydrogeochemistry

Evaluation hydrogéochimique d’eaux souterraines à fortes teneurs en fluorures: une étude de cas de la Région de Mehsana, Gujarat, Inde Résumé Des problèmes de qualité de l’eau souterraine sont apparus dans de nombreuses régions géographiques à cause de processus environnementaux naturels et de l’intervention humaine dans les géosystèmes. L’évaluation hydrogéochimique de l’eau souterraine contaminée par des fluorures de la Région de Mehsana, dans l’Etat Indien de Gujarat, est menée grâce à des observations de qualité de l’eau souterraine et à des analyses par diffraction de rayons X d’échantillons de sol issus des zones qui présentent de fortes teneurs en fluorures. Les résultats montrent que les fluorures ont des relations négatives avec le calcium, et positives avec le sodium, l’alcalinité et les sulfates. Les résultats de la modélisation de la spéciation aqueuse avec PHREEQC révèlent que l’eau souterraine est sous-saturée en fluorures et sur-saturée en calcite. L’analyse factorielle indique que le sodium plus le bicarbonate de potassium de l’eau souterraine ont un facteur de charge important pour les fluorures, mais faible pour les chlorures de calcium et de magnésium. Les réactions géochimiques plausibles de la zone d’étude sont la précipitation de la calcite et la dissolution de la dolomite, du dioxyde de carbone et des minéraux sulfatés avec échanges ioniques. Mots clefs modélisation de spéciation aqueuse; fluorure; eau souterraine; Gujarat, Inde; hydrogéochimie INTRODUCTION Occurrence of fluoride (F-) in groundwater has drawn global attention as ingestion of water with fluoride concentration above 1.5 mg L-1 may result in dental or skeletal fluorosis. The maximum tolerance limit of fluoride in drinking water specified by the World Health Organization (WHO, 1984) is 1.5 mg L-1. High fluoride concentration in the groundwater has been reported in many parts of Indian subcontinent and is becoming a serious concern for the drinking water supply (Jacks et al., 2000, 2005; Keshari & Dhiman, 2001). Studies reveal that infants, children and adults in the study area of Mehsana District are exposed to high doses of fluoride from groundwater (Chinoy et al., 1992; Dhiman & Keshari, 2003). Normally, fluorine, because of its high reactivity, exists in the form of fluoride in natural waters (Leung & Hrudey, 1985). Fluorine occurs mainly as free fluoride ion (F-) in natural waters, though

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fluoride complexes of Al, Be, B and Si are also encountered under specific conditions. Strunz (1970) reported about 150 fluorine-bearing minerals (63 silicates, 34 halides, 22 phosphates and 30 others), but many minerals may contain minor amounts of F- replacing OH- or O2-. The main natural sources of fluoride in soil are fragments of minerals, such as apatite, cryolite, fluorite or fluorspar and topaz (Al silicates containing F), fluormica (phologopite), epidote, phosphorite, tremolite and villuanite. These can be supplemented by anthropogenic input from industrial sources. Industries which use raw materials containing even small amounts of fluorine can release enough gaseous (HF, SiF4) and/or particulate fluorides (AlF3 Na3AlF6, CaF2) to enhance elemental levels in the surrounding areas. Pollutant sources include: manufacturers of bricks, iron-based fertilizers and glass; coal-fired power stations; and aluminium smelters (Handa, 1975; Wedepohl, 1978; Matthes & Harvey, 1982; Deer et al., 1983; Pickering, 1985; Hem, 1986; Handa, 1988; Gaumat et al., 1992; Gaciri & Davies, 1993, Rao, 1997). The occurrence of fluoride has been reported in both igneous and sedimentary rocks. The concentration of F- ranges from 30 to 21000 ppm in amphiboles present in metamorphic rocks, and pegmatite intrusions also cause high fluoride in groundwater (Srikanth et al., 2002). Several minerals, such as sepiolite and palygorskite, also control the fluoride distribution in groundwater in many geographical regions. Geo-chemical reactions, namely precipitation/dissolution, aqueous complexation, sorption, dissolution and exsolution of gases, and changes in groundwater flow pattern signifi-cantly affect the distribution of geochemical species in natural aqueous systems. Wang et al. (1993) proposed a dynamic model that predicts the features of calcrete as a function of any desired climatic changes in temperature, wet/dry relative durations, PCO2 and water table position and slope in the semiarid regions. In the recent past, factor analysis has been used by many investigators for identifying the interrelationships between the chemical constituents (Dawdy & Feth, 1967; Mellout & Collin, 1992; Brown, 1993; Cameron, 1996; Evans et al., 1996; Grande et al., 1996; Subbarao et al., 1996; Gupta et al., 1999, Adams, et al. 2001; Jeong, 2001; Kundu et al,. 2001; Wang et al., 2001; Reghunath et al., 2002; Farnham et al., 2003; Liu et al., 2003; Stuben et al., 2003). In this study, hydrogeochemical evaluation of high-fluoride groundwaters in Mehsana District, Gujarat State, India is carried out (a) to characterize fluoride contamination in the groundwater; and (b) to identify plausible geochemical reactions under the prevailing hydrogeological conditions, as well as their role in mobilizing fluoride concentration. DESCRIPTION OF THE STUDY AREA Mehsana District in Gujarat State (as per administrative boundaries, 1980) is located in the western part of India between 23°02′–24°09′N and 71°26′–72°51′E (Fig. 1). It is primarily an agricultural district with a total cultivable area of 0.75 × 106 ha, which is 83 % of the total reported area. Only about 2% of the area of the district is under forest, which is mainly concentrated in Kheralu and Sami talukas. The net area sown during 1993/94 was 78%. The principal crops under cultivation are millet (bajra), cotton, and tall millet (jowar). The rivers Sabarmati, Saraswati, Rupen and Banas flow through the study area. The normal annual precipitation ranges from 500 mm in the

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India

Mehsana districtGujarat

Fig. 1 Map of Mehsana District, Gujarat State, India.

west to 900 mm towards the east. About 97% of the total annual rainfall occurs during the Southwest Monsoon from June to mid-September. On average, there are 31.3 rainy days, of which 29.4 occur during June–September (Kumar, 1998). The average annual rainfall of the district is 603 mm for the 31-year period (1965–1995) and severe droughts occur with a frequency of 16%. The average temperature is 40°C during summer and 10°C during winter. The mean annual value of potential evapotrans-piration for the study area can be taken as 1677 mm, based on the measurements recorded at Ahmedabad meteorological station. The relative humidity in the region is between 60 and 80%, and the mean wind speed during summer (May–July) is about 18.7 km h-1. The geological setup for the district shows thick alluvium almost throughout the study area, and the Ajabgarh metasedimentary rocks occupy a small area in the northeastern portion (Fig. 2). The latter consist of calc-gneiss and para-gneiss, which have been intruded by basic rocks. The granites occur in the northeastern part and are highly weathered, giving rise to clay formation. Over the granites lie the Himmatnagar formation, comprising sandstone, conglomerate and shale. These formations are also highly weathered. The tertiary rocks are not exposed anywhere in the district as they are overlain by thick soil and alluvium. The geological cross-sections reveal that the average thickness of sandy clay may be 35–40 m at a depth of 125 m below the ground surface. A sandy clay lens of 15 m thickness is also observed at about 50 m below the ground surface in the southeastern part of the study area. The main mineral resources in the district are china clay and fire clay. Occurrence of bentonite beds in the alluvial deposits may be the result of deposition of bentonite, washed from the granitic terrain, towards the east and northeast by winds (Phadtare, 1981). The five main types of soil in the district are: saline-alkali soil, calcareous sandy loams, calcareous sandy soil, non-calcic brown soils and non-calcic red-brown soils (UNDP/CGWB, 1976), as

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Fig. 2 Geology map of Mehsana district.

Fig. 3 Generalized soil map of Mehsana District.

shown in Fig. 3. The unconfined aquifer thickness ranges from 35 to 125 m. The trans-missivity of the unconfined aquifer ranges between 30 and 1000 m2 day-1. The specific capacities of wells are between 23 and 714.1 m2 day-1. The depth of wells ranges from 8 to 18.5 m below ground level (b.g.l.) and depth to water level in open wells varies from 5 to 14 m b.g.l. The yield of wells is in the range 30–120 m3 day-1 (Kumar, 1998). Tube wells, with depths of 60–350 m, and discharges of 1728–5184 m3 day-1, are the main abstraction structures in the district. The uppermost confined aquifer consists of medium- to coarse-grained sands and gravel, locally interstratified with

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Table 1 Hydrochemical parameters (June, 1980).

Location pH Ca Mg Na K F Cl SO4 CO3 HCO3 NO3 EC Bhandu 8.1 2.59 9.21 26.54 1.79 0.03 33.0 1.79 - 4.19 0.74 4150 Bhatson 7.65 3.59 19.09 30.02 6.57 0.12 39.99 8.59 - 8.39 2.67 6870 Bheesal Vasana 8.2 2.19 2.96 14.0 0.20 0.08 8.01 1.20 - 9.39 0.25 1860 Charasanph-2 7.65 5.18 5.02 27.32 0.41 0.01 33.98 0.29 - 3.39 0.45 3920 Charasanphi 7.9 3.39 2.63 17.31 0.28 0.01 17.99 1.79 - 3.6 0.32 2520 Dabhoda 8.3 0.99 0.98 4.22 0 0.1 1.80 15.0 0.8 3 0.25 625 Gadha 7.9 5.98 3.37 13.40 0 0.07 14.80 1.70 - 5.80 0.96 2330 Gilosan 8.2 2.79 4.19 16.01 0.20 0.04 11.0 2.49 - 9.19 0.54 2265 Kamalpura 8.5 1.79 2.63 4.00 0.10 0.03 3.80 0.89 0.8 2.60 0.51 850 Karoda 8.5 0.99 1.97 53.04 0.84 0.05 39.9 4.10 - 10 0.29 6110 Khimiyana 8.15 3.79 3.62 7.52 1.79 0.03 5.61 1.20 - 9 0.38 1630 Lunawa 8.5 1.39 1.56 7.00 0 0.05 2.98 0.72 0.8 4.39 0.32 920 Malekpur 8.75 2.99 6.00 2.30 0 0.09 2.00 0.70 1.6 6.19 0.12 990 Mehsana 8.6 1.99 3.37 16.40 0 0.04 8.91 3.10 0.8 8.19 0.29 2105 Nedra 8.45 0.59 2.22 4.78 0.10 0.05 2.90 0.70 0.8 3.19 0.19 790 Pamol 7.9 0.79 1.56 8.52 0 0.06 2.39 0.41 - 7.4 0.17 1050 Patan 7.65 3.79 6.33 26.02 1.99 0.07 19.80 3.70 - 11.8 3.16 3790 Sariyad 8.05 4.49 2.88 15.01 0.12 0.00 11.59 7.37 - 4.60 0.22 2310 Sipur 7.8 1.59 1.97 15.79 0 0.2 7.81 0.89 - 10 0.40 1845 Titodan 8.6 3.59 4.60 5.22 0.07 0.06 3.41 0.79 1.6 7.60 0.30 1230 Unawa 8.1 7.58 24.03 19.53 1.68 0.03 35.39 4.49 - 9.19 4 5854 Vadnagar 8.05 0.99 2.96 82.07 15.95 0.3 42.39 20.48 - 37.8 0.5 10025 Veerpur 8.25 0.79 1.97 8.79 0 0.09 4.20 1.06 - 5.60 1.29 1200 Veragram 8 2.59 4.77 35.55 0.99 - 30.99 6.10 - 5.4 1.74 4720 Visnagar 8.5 1.39 1.97 18.79 1.09 0.02 10.2 1.99 1.2 10.2 0.96 2280 Wagrod 7.95 7.48 3.53 6.22 1.79 0.00 11.98 1.60 - 5.60 0.32 1935 All concentrations (exc. pH) in meq L-1; EC in mmhos cm-1 at 25°C.

clay lenses and is separated from overlying and underlying aquifers by beds of clay and sandy clays. The confined aquifer is found at a depth of 78–162 m below the ground surface. The groundwater quality parameters of the unconfined aquifer reported by Phadtare (1981) for various locations are given in Table 1. FIELD AND EXPERIMENTAL INVESTIGATIONS Groundwater quality monitoring was carried out for 21 well locations in the study area during June and October 2002. The details of well locations, well type and depth of wells are given in Table 2. The soil samples were also collected for mineralogical investigation. A Global Positioning System (GeoExplorer 3.0; Trimble GPS) was used for locating wells in the study area. Chemical analysis was conducted following the APHA standard methods (APHA, 2000). In situ measurements were taken for pH and temperature using portable meters (Eutech, Singapore). The chemical constituents, namely calcium and total hardness, were determined by EDTA titration method and alkalinity was measured by titrating with sulphuric acid. Fluoride, potassium, sulphate and iron concentrations were measured using a spectrophotometer and an ion-selective electrode was used for the measurement of chloride. The SPADNS method was used for fluoride determination. Regression analysis between sodium and chloride was carried out using the hydrochemical data presented by Phadtare (1981), Krupanidhi et al. (1986) and Kumar (1998). This gave an r2 value of 0.9. Using this relationship

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Table 2 Well location, type and depth of well.

GPS observations Location Latitude, N Longitude, E Altitude

(m a.m.s.l.)

Well type

Depth of well (m b.g.l.)

Ambavada 23°52′66.29″ 72°40′36.92″ 190 TW 151.5 Badarpur 23°49′49.57″ 72°39′34.65″ 179.7 TW 75.75 Dabhoda 23°56′57.65″ 72°41′55.08″ 236.1 DB 36.36 Gathaman 23°53′06.71″ 72°39′40.28″ 176.7 TW 90.9 Gorisana 23°53′30.84″ 72°42′49.37″ 190 TW 56.06 Gunja 23°44′42.92″ 72°35′07.10″ 150 TW 272.7 Hirwani-Moti 23°52′36.01″ 72°32′56.16″ 145.5 DW 15.15 Jaska 23°49′14.6″ 72°32′8.10″ 126.8 DB 18.78 Kahipur 23°44′53.63″ 72°39′53.86″ 148.6 TW 66.6 Karbatia 23°46′16.49″ 72°42′55.34″ 174.3 TW 69.7 Kheralu 23°53′45.5″ 72°37′38.77″ 186 TW 60.6 Malekpur-1 23°46′06″ 72°35′56.7″ 151.8 TW 121.7 Malekpur-2 23°46′11.38″ 72°36′02″ 147.5 DW 10.5 Mandali 23°59′19.58″ 72°29′50.45″ 179.2 TW 90.9 Sipor 23°50′27.58″ 72°39′47.3″ 179.6 TW 75.7 Sundhia 23°50′23.8″ 72°35′13.86″ 163.6 DB 21.2 Umta 23°46′51.25″ 72°33′35.08″ 131.8 TW 75.7 Vadnagar 23°47′37.23″ 72°37′54.8″ 153 DW 19.7 Vaghvadi 23°52′55″ 72°44′39.17″ 191.5 DW 30.3 Varetha 23°58′0.016″ 72°41′11.70″ 212.2 TW 63.6 Vithoda 23°55′ 16″ 72°32′47.12″ 180 DW 16.9 DW: dug well; DB: dug-cum-bored well; TW: tube well. between Na+ and Cl-, the concentrations of Na+ were calculated for the observed data of June 2002 and October 2002 from the Cl- concentrations. The cation–anion balance error of 18 samples collected in June and October 2002 is within the permissible limit of 5% and the remaining three samples with higher ion balance error were not considered in the study. Soil phase analysis The soil samples were collected from Dabhoda, Malekpur, Sipor, Umta, Vadnagar and Vaghwadi villages in the Mehsana District using a hand auger from a depth of 60 cm b.g.l. Mineralogical characterization of soil samples was carried out using a D-8 advanced powder X-ray diffractometer (Bruker, Germany) at the National Physical Laboratory (NPL), New Delhi and PW 1710/00 powder X-ray diffractometer (Philips, Holland) in the Textile Technology Department, Indian Institute of Technology, Delhi. The X-ray diffractometry (XRD) patterns were obtained from the D-8 and PW1710/00 diffractometers using Cu Kα radiation equipped with a diffracted-beam mono-chromator in the range 5–60° 2θ and 10–60° 2θ, respectively. The voltage and current were kept at 40 kV and 30 mA, respectively. The scanning rate was kept at 2° per minute. The qualitative identification of the crystalline phases was carried out by studying the peaks in the diffractograms.

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RESULTS AND INTERPRETATION Fluoride hydrogeochemistry and aqueous speciation modelling Concentrations of various groundwater quality parameters obtained for samples collec-ted in June and October 2002 are shown in Table 3. The water type for each sample is also indicated. It is evident that groundwater is mainly of types Na-HCO3, Ca-HCO3 and Mg-HCO3. The area with high fluoride concentration in the unconfined aquifer was delineated using hydrochemical data of June 1980. The calcium concentration ranges between 12 and 152 mg L-1 and fluoride between 0.14 and 5.6 mg L-1. High fluoride concentration in the groundwater is observed in the northeastern part of

Table 3 Hydrochemical parameters for June and October 2002 (concentrations are in meq L-1).

Location pH Ca Mg Na K F Cl SO4 CO3 HCO3 Water type June 2002: Ambavada 7.5 6.39 7.22 2 0.8 0.10 3.82 3.0 - 9.18 Mg-HCO3 Badarpur 8 1.07 0.32 8.9 0.13 0.09 2.26 1.25 - 10.16 Na- HCO3 Dabhoda 7.8 2.31 3.05 1.97 0.23 0.05 1.53 0.20 - 5.90 Mg- HCO3 Gathaman 8 2.07 2.64 12.5 0.10 0.09 3.08 2.37 - 8.68 Na- HCO3 Gorisana 8.6 5.03 2.81 13.4 0.18 0.09 3.97 8.54 1.6 6.72 Na-SO4 Hirwani-Moti 7.8 2.07 3.25 1.7 0.15 0.11 1.55 0.29 - 4.42 Mg- HCO3 Jaska 7.5 4.92 0.68 1.63 0.13 0.02 2.07 0.83 - 5.08 Ca- HCO3 Kahipur 8 1.55 0.84 8.9 0.13 0.07 2.14 1.04 - 7.27 Na- HCO3 Karbatia 7.8 2.32 1.56 1.97 0.10 0.08 1.6 0.41 - 4.91 Ca- HCO3 Malekpur -1 7.5 3.27 2.32 11.23 0.56 0.09 3.07 6.45 - 13.11 Na- HCO3 Malekpur -2 8 6.79 2.81 1.92 0.15 0.02 3.0 1.45 - 7.14 Ca- HCO3 Mandali 7.8 4.74 7.26 1.78 0.13 0.08 3.35 2.16 - 7.64 Mg- HCO3 Sipor 8.1 1.67 2.53 9.62 0.13 0.09 2.47 1.62 - 9.57 Na- HCO3 Sundhia 8.1 2.79 2.24 1.93 0.15 0.17 1.4 0.13 - 4.52 Ca- HCO3 Umta 7.6 2 2.48 11.9 0.13 0.07 2.9 2.7 - 9.37 Na- HCO3 Vadnagar 9.1 1.20 0.40 9.97 0.18 0.06 2.6 4.5 0.8 4.6 Na- HCO3 Vaghvadi 8 1.59 1.20 9.8 0.13 0.09 2.2 1.12 - 8.85 Na- HCO3 Varetha 8 1.15 3.45 2.25 0.10 0.03 1.9 0.29 - 5.18 Mg- HCO3 October 2002: Ambavada 7.2 6.81 2.79 12.82 0.04 0.2 3.95 6 - 13.44 Na- HCO3 Badarpur 7.7 0.60 15.4 2 0.13 0.18 2.6 1.04 - 15.73 Mg- HCO3 Dabhoda 7.7 2.80 0.76 8.9 0.13 0.08 1.47 0.83 - 7.21 Na- HCO3 Gathaman 7.5 6.49 2.24 11.7 0.13 0.19 3.75 5.21 - 10.82 Na- HCO3 Gorisana 7.2 1.76 0.8 12.5 0.13 0.18 3.25 2.3 - 13.83 Na- HCO3 Hirwani-Moti 8.2 2.40 7.51 1.7 0.15 0.005 2.22 0.83 - 8.72 Mg- HCO3 Jaska 7.8 5.41 0.87 1.7 0.13 0.03 2.21 0.83 - 4.85 Ca- HCO3 Kahipur 7.7 2.60 1.39 9.7 0.13 0.05 1.98 1.04 - 7.21 Na- HCO3 Karbatia 7.6 2.72 2.31 1.5 0.13 0.10 1.47 0.83 - 5.05 Ca- HCO3 Malekpur-1 8.6 0.88 2.15 10.5 0.18 0.08 2.53 1.67 1.6 5.18 Na- HCO3 Malekpur-2 7.9 7.24 0.8 1.9 0.53 0.06 2.95 1.04 - 6.50 Ca- HCO3 Sipor 8 5.21 12.4 10.6 0.13 0.04 3.12 2.3 - 10.1 Na- HCO3 Sundhia 7.1 2.12 1.43 1.62 0.13 0.18 2.52 2.08 - 12.13 Ca- HCO3 Umta 7.7 5.61 2.20 11.3 0.13 0.04 1.92 0.83 - 6.06 Na- HCO3 Vadnagar 7.8 2.40 1.52 11.9 0.13 0.07 3.09 2.5 - 8.85 Na- HCO3 Vaghvadi 7.6 2.72 6.96 9.9 0.15 0.14 3.38 6.67 - 7.54 Na- HCO3 Varetha 7.8 2.00 2.6 1.65 0.15 0.18 2.09 1.25 - 12.20 Mg- HCO3

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Table 4 Correlation coefficients matrix for June 1980 hydrochemical data.

Ca Mg Na K F Cl HCO3 SO4 NO3 EC pH Ca 1 Mg 0.53 1 Na –0.13 0.12 1 K –0.06 0.22 0.78 1 F –0.36 –0.04 0.50 0.70 1 Cl 0.25 0.54 0.82 0.58 0.17 1 HCO3 –0.16 0.02 0.77 0.88 0.75 0.42 1 SO4 –0.15 0.10 0.63 0.75 0.58 0.43 0.64 1 NO3 0.41 0.80 0.18 0.18 –0.02 0.48 0.09 0.13 1 EC 0.13 0.48 0.92 0.80 0.42 0.94 0.7 0.62 0.45 1 pH –0.40 –0.27 –0.26 –0.25 –0.13 –0.45 –0.10 –0.14 –0.40 –0.37 1 Mehsana District and decreases in the southwestern part. Dissolved fluoride is less than 1 mg L-1 in the southwestern part where clay content is high. Moreover, calcium concen-tration in the groundwater is less in the northeastern part of the district and increases in the southwestern part. The correlation coefficients among various groundwater quality parameters were obtained to investigate their interdependence. The correlation matrix for the hydrochemical data of June 1980 is shown in Table 4. This shows that fluoride has a negative relationship with calcium, magnesium, nitrate and pH, while the relationship with sodium, potassium, bicarbonate alkalinity, sulphate, chloride and EC is positive. High fluoride concentration occurs in sodium-bicarbonate waters. The upper limits of the point distribution for observed fluoride and calcium concentrations (combined hydrochemical data of June 1980, June 2002 and October 2002) form a hyperbolic curve that suggests solubility of calcium- and fluoride- containing minerals controls the fluoride concentration (Fig. 4). High fluoride with very low calcium and magnesium in water may be due to prior precipitation of CaCO3 from water and only limited incorporation of fluoride in the calcite structure, so that there is always a net balance of fluoride in the solution, as suggested by Rao et al. (1993). The calcite content in the soils of Mehsana District ranges from 0.1 to 10.28%. The pH of these soils varies from 7 to 9. The hydraulic conductivity of the soil ranges from zero for saline and alkali soils in the western part to more than 7 cm h-1 for calcareous sandy soils towards north and west. The results of XRD analysis for the soil samples were as follows: the crystalline phases identified in the soil samples of Dabhoda and

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Fig. 4 Relationship between calcium and fluoride concentration.

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-6-5-4-3-2-10

0 2 4 6 8Calcium meq L-1

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Fig. 5 Plot of saturation indices of fluorite vs calcium concentration.

Umta are quartz (α-SiO2) and calcite (CaCO3). The soil sample of Malekpur is highly crystalline material and contains quartz as the main crystalline phase with calcite and sodium calcium aluminium silicate anorthite—(Na, Ca) (SiAl)4O8 as the phases. The soil samples of Sipor, Vaghwadi and Vadnagar are also highly crystalline material and contain quartz as the main crystalline phase with calcite and sodium aluminium silicate albite (NaAlSi3O8) as the next phases. Aqueous speciation modelling was carried out using PHREEQC (Parkhurst & Appelo, 1999) geochemical code. The saturation indices of fluorite were computed for all three sets of temporal data, sampled as well as earlier hydrochemical data. Figure 5 shows the plot of these saturation indices vs calcium con-centrations. It shows that the groundwater is oversaturated with calcite, having a saturation index of 0.06–1.74 with equilibrium state at Umta. The groundwater is undersaturated with fluorite, having a saturation index of 0.03 to –4.87. Multivariate analysis The factor analysis was carried out using the hydrochemical data of June 1980 for the unconfined aquifer of the study area. These data constitute a larger data set as compared to the sampled data of June and October 2002, and were considered for the multivariate analysis without combining with the sampled data to make the homogeneous data set with reference to dynamic changes in hydraulic stresses, land-use characteristics and pollutant sources. The chemical constituents considered for factor analysis for the uncon-fined aquifer were calcium, magnesium, sodium, potassium, bicarbonate alkalinity, sulphate, chloride, fluoride, nitrate, pH and electrical conductivity (EC). The carbonate alkalinity concentration was not considered for factor analysis. The principal component analysis was carried out using SPSS (Statistical Package for Social Services) software. The two-factor model results reveal that the first two eigenvalues extracted from the matrix account for more than 72% of total variance, which shows that the hydrochemical data are well posed. A varimax rotated component matrix with Kaiser (1958) normalization was used for principal component analysis. The interpretation of factors was made in terms of the square of the coefficients of that factor. The distributions of factor scores for Factor 1 and Factor 2 for the geographical locations are shown in Fig. 6(a) and (b), respectively. The rotated component matrix for the geochemical data is given in Table 5. There is almost identical loading for sodium, potassium and bicarbonate. Therefore, the variance in the chemical composition of the hydrochemical

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Fig. 6 Distribution of scores of (a) Factor 1 and (b) Factor 2 in the geographical area.

system is controlled by sources of sodium and bicarbonate. For Factor 1, the sum of squares of sodium and potassium (1.62) approximates that of bicarbonate, sulphate and chloride (1.8). Thus, the combined relationship suggests that there is more than one component or more than one solid phase that adds or removes sodium, potassium, bicarbonate, sulphate and chloride into the groundwater. The presence of negative correlations indicates that some components are controlled by equilibrium with the minerals in the aquifers. Thus, there is a reaction path by which one set of chemical products replaces another set. Factor 2 shows that the sum of squares of calcium and magnesium (1.29) approximates that of nitrate and chloride (1.13). The combined relationship suggests that there is more than one component or more than one solid phase that adds or removes calcium, magnesium, chloride and nitrate. For Factor 2, there is no replacement mechanism as there is lack of mutually exclusive components. The origin of nitrate may be from the use of urea fertilizer. Factor 2 shows calcium chloride and magnesium chloride waters. Moreover, it is observed that there is negative correlation between calcium and fluoride for both the factors. For

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Table 5 Rotated component matrix.

Component Parameter 1 2

Ca –0.28 0.74 Mg 4.7 × 10-2 0.86 Na 0.89 0.23 K 0.91 0.17 F 0.78 –0.22 Cl 0.59 0.67 SO4 0.80 4.2 × 10-2 HCO3 0.91 –2.7 × 10-2 pH –0.18 –0.58 NO3 7.9 × 10-2 0.83 EC 0.80 0.54 Factor 1, probably there is dissolution of fluorite and precipitation of calcite, whereas for Factor 2, the decrease in fluoride may be due to adsorption on clay surfaces. Thus, these results obtained from factor analysis help in understanding the possible grouping of chemical constituents in the groundwater. Geochemical reactions The actual changes in concentrations of chemical species as a function of sulphate con-centration help in obtaining the information on the possible geochemical reactions that may be occurring in the study area. To investigate this, analysis was carried out using the hydrochemical data of June 1980, June 2002 and October 2002. The increase in calcium and magnesium as sulphate increases, and the increase in sulphate and decrease in pH are shown in Fig. 7(a)–(c). The groundwater in the study area is saturated with calcite and dolomite, and dissolution of anhydrite adds calcium to the groundwater, causing precipitation of calcite. Calcite precipitation causes the pH to decrease due to release of H+ ions from bicarbonate during incorporation of carbonate in calcite. The decrease in the CO2 in the solution leads to dissolution of dolomite and CO2 dissolution, thereby increasing the magnesium concentration in the solution. The mass of the anhydrite and dolomite dissolved in the process exceeds the mass of calcite precipitated, resulting in a net increase in the dissolved calcium as shown in Fig. 7(a). The geochemical equations for possible reactions in the aquifer are as follows:

CaSO4 → Ca+2 + SO-24 (1)

HCO-3 → H+ + CO-2

3 (2) Ca+2 + CO-2

3 → CaCO3 (3) CaMg(CO3)2 → Ca+2 + Mg+2 + 2CO-2

3 (4) CO2(g) → CO2(aq) (5) NaCl → Na+ + Cl- (6) KCl → K+ + Cl- (7)

where (g) in (5) refers to the gaseous phase and (aq) to the aqueous phase.

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ion exchange

dedolomitization

Fig. 7 Plot of calcium, magnesium, pH and bicarbonate alkalinity as a function of sulphate.

Although the trends in calcium, magnesium and pH with sulphate are evident in the groundwater of the northeastern part of Mehsana District, there is variation in the temperature and other reactions in addition to dedolomitization or dissolution of carbonates. Dedolomitization is a specific geochemical process and has been reported by Plummer et al. (1990) and Kloss & Goebelbecker (1992). The plot of bicarbonate alkalinity as a function of dissolved sulphate concentration (Fig. 7(d)) shows that bi-carbonate alkalinity is decreasing with increase in sulphate, and is possibly indicative of dedolomitization or carbonate dissolution. Cation exchange with calcium and magnesium cations could contribute to additional bicarbonate on the flow path with uptake of calcium and magnesium and release of sodium from exchange sites on clay minerals causing dissolution of carbonate minerals. The molal concentrations of sodium plus potassium are slightly more than the concentration of chloride. This is indicative of presence of evaporites. These waters have high bicarbonate concentra-tion. Thus, there is a tendency to form sodium-bicarbonate waters. For the groundwater in the study area of Mehsana District, the sodium bicarbonate water is derived from the dissolution of carbonate minerals. Further investigations using scanning electron microscope (SEM) and microprobe analysis for soil samples, although not carried out in the present study, may ascertain the dedolomitization process. CONCLUSIONS High fluoride concentration in groundwater, ranging in between 1.5 and 5.6 mg L-1, is observed in large parts of the Mehsana District, Gujarat, India, and is a matter of concern for drinking water supply since it exceeds the maximum permissible fluoride concentration of 1.5 mg L-1 for public water supply systems. Dissolved fluoride is usually less than 1 mg L-1 in the southwestern part of the district, whereas the

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northeastern region is the most affected area, having fluoride concentrations of more than 2 mg L-1 in some areas. It is observed that fluoride has a negative correlation with calcium, magnesium, nitrate and pH, while a positive correlation is observed with sodium, potassium, bicarbonate alkalinity, sulphate, chloride and EC. Factor analysis revealed that sodium bicarbonate waters have high fluoride, whereas calcium chloride and magnesium chloride waters have low factor loading for fluoride. Results obtained from aqueous speciation modelling reveal that the groundwater is oversaturated with calcite, indicating precipitation of calcite, and undersaturated with fluorite, possibly indicative of its dissolution. The results of X-ray diffraction analysis of soil samples show the presence of quartz, calcite, albite and anorthite as the main crystalline phases. The geochemical reactions in the study area indicate precipitation of calcite and dissolution of dolomite, carbon dioxide and sulphate-bearing minerals with ion exchange. Acknowledgements The authors are grateful to the reviewers for their constructive and thoughtful comments and suggestions, which have helped in improving the quality of the paper significantly. REFERENCES Adams, S., Titus, R., Pietersen, K., Tredoux, G. & Harris, C. (2001) Hydrochemical characteristics of aquifers near

Sutherland in the Western Karoo, South Africa. J. Hydrol. 241(1&2), 91–103. APHA (2000) Standard Methods for the Examination of Water and Wastewater, 20th edn. American Public Health

Association, Washington DC, USA. Brown, C. E. (1993) Use of principal-component, correlation, and step wise multiple regression analyses to investigate

selected physical and hydraulic properties of carbonate-rock aquifers. J. Hydrol. 147, 169–195. Cameron, E. M. (1996) Hydrogeochemistry of Fraser River, British Columbia: seasonal variation in major and minor

components. J. Hydrol. 182, 209–225. Chinoy, N. J., Narayana, M. V., Sequeria, E., Joshi, S. M., Barot, J. M., Purohit, R. M., Parikh, D. J. & Ghodasara, N. B.

(1992) Studies on effects of fluoride in 36 Villages of Mehsana District, North Gujarat. Fluoride 25(3), 101–110. Dawdy, D. R. & Feth, J. H. (1967) Applications of factor analysis in study of chemistry of groundwater quality, Mojave

River Valley, California. Water Resour. Res. 3, 505–510. Deer, W. A., Howie, R. A. & Zussman, J. Z. (1983) An Introduction to Rock Forming Minerals, The English Language

Book Society and Longman. Dhiman, S. D. & Keshari, A. K. (2003) Quantifying uncertainties using fuzzy logic for groundwater driven contaminant

exposure assessment. In: Groundwater Quality Modeling and Management under Uncertainty (ed. by S. Mishra) (Proc. World Water and Environmental Resources Congress, 23–26 June 2003, Philadelphia, USA), 236–247. EWRI-ASCE Publication, Philadelphia, USA.

Evans, C. D., Davies, T. D., Wigington, P. J., Tranter, M. & Kretser, W. A. (1996) Use of factor analysis to investigate processes controlling chemical composition of four streams in the Adirondack mountains, New York. J. Hydrol. 185, 297–316.

Farnham, I. M., Johannesson, K. H., Singh, A. K., Hodge, V. F. & Stetzenbach, K. J. (2003) Factor analytical approaches for evaluating groundwater trace element chemistry data, Analytica Chimica Acta 490(1&2), 123–138.

Gaciri, S. J. & Davies, T. C. (1993) The occurrence and geochemistry of fluoride in some natural waters of Kenya. J. Hydrol. 143, 395–412.

Gaumat, M. M., Rastogi, R. & Misra, M. M. (1992) Fluoride level in shallow groundwater in central part of Uttar Pradesh. Bhu-Jal News 7(2&3), 17–19.

Grande, J. A., Gonzalez, A., Beltran, R. & Sanchez-Rodas, D. (1996) Application of factor analysis to the study of contamination in the aquifer system of Ayamonte-Huelva (Spain) Groundwater 34(1), 155–161.

Gupta, M. K., Singh, V., Rajwanshi, P., Agrawal, M., Rai, K., Srivastava, S., Shrivatava, R. & Dass, S. (1999) Groundwater quality assessment of Tehsil Kheragarh, Agra (India) with special reference to fluoride. Environ. Monitoring Assess. 59(3), 275–285.

Handa, B. K. (1975) Geochemistry and genesis of fluoride containing groundwater in India. Ground Water 13, 275–281. Handa, B. K. (1988) Fluoride occurrence in natural waters in India and its significance. Bhu-Jal News 3(2), 31–37. Hem, J. D. (1986) Study and interpretation of the chemical characteristics of natural water US Geol. Survey Water Supply

Paper 2254.

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Jacks, G., Bhattacharya, P. & Singh, K. P. (2000) High fluoride groundwaters in India. In: Proc. Int. Conf. on Groundwater Research (Copenhagen, Denmark) (ed. by P. L. Bjerg, P. Engesgaard & T. D. Krom), 193–194. A. A. Balkema, Rotterdam, The Netherlands.

Jacks, G., Bhattacharya, P., Chaudhary, V. & Singh, K. P. (2005) Controls on the genesis of some high-fluoride groundwaters in India. Appl. Geochem. 20, 221–228.

Jeong, C. H. (2001) Effect of land use and urbanization on hydrochemistry and contamination of groundwater from Taejon area, Korea. J. Hydrol. 253(1/4), 194–210.

Kaiser, H. F. (1958) The varimax criterion for analytic rotation in factor analysis. Psychometrika 23, 187–200. Keshari, A. K. & Dhiman, S. D. (2001) Genesis of fluoride contamination in the Western Indian Aquifers. In: Future

Groundwater Resources at Risk (FGR’01) (ed. by L. Ribeiro) (Proc. Third Int. Conf., Lisbon, Portugal, 25–27 June 2001), Theme 3: Point and non-point source pollution, 1–8.

Kloss, W. S. & Goebelbecker, J (1992) Dedolomitization and salt formation in a semi-arid environment. In: Progress in Hydrogeochemistry (ed. by G. Matthess, F. Frimmel, P. Hirsch, H. D. Schulz, H.-E. Usdowski), 184–189. Springer-Verlag, New York., USA.

Krupanidhi, K. V. J. R., Srivastava, M. L., Doshi, S. K., Dhiman, S. C. & Goel, R. K. (1986) Water level and chemical data of national hydrograph network stations in Gujarat for the year 1978–84. Central Ground Water Board/Ministry of Water Resources/Government of India, Western Region, Jaipur, India.

Kumar, A. (1998) Hydrogeological framework and ground water resources of Mehsana district, Gujarat. Report, Central Ground Water Board, Government of India.

Kundu, N., Panigrahi, M. K., Tripathy, S., Munshi, S., Powell, M. A. & Hart, B. R. (2001) Geochemical appraisal of fluoride contamination of groundwater in the Nayagarh District of Orissa, India. Environ. Geol. 41, 451–460.

Leung, D. C. W. & Hrudey, S. F. (1985) Removal of fluorides from water supplies. Alberta Environmental Standard and Approval Division., July 1985, 107.

Liu, C. W., Lin, K. H & Kuo, Y. M. (2003) Application of factor analysis in the assessment of groundwater quality in a blackfoot disease area in Taiwan. Sci. Total Environ. 313(1&3), 77–89.

Matthes, G. & Harvey, J. C. (1982) The Properties of Water, John Wiley & Sons Inc., New York., USA. Mellout, A. & Collin, M. (1992) The principal component statistical method as a complimentary approach to geochemical

methods in water quality factor identification; application to the coastal plain aquifer of Israel. J. Hydrol. 140, 49–73. Parkhurst, D. L. & Appelo, C. A. J. (1999) User’s guide to PHREEQC (Version 2)—A computer program for speciation,

batch reaction, one dimensional transport and inverse geochemical calculations: US Geol. Survey WRI-99-4259, US Geol. Surv., Denver, Colorado, USA.

Phadtare, P. N. (1981) Groundwater resources and development potential of Mehsana district, Gujarat. Report, Central Ground Water Board, Government of India.

Pickering, W. F. (1985) The mobility of soluble fluorides in soils. Environ. Pollut. Ser. B 9, 281–308. Plummer, L. N., Busby, J. F., Lee, R. W. & Hanshaw, B. B. (1990) Geochemical modelling of Madison Aquifer in parts of

Montana, Wyoming, and South Dakota. Water Resour. Res. 26(9), 1981–2014. Rao, N. S. (1997) The occurrence and behaviour of fluoride in the groundwater of the Lower Vamsadhara River basin,

India. Hydrol. Sci. J. 42(6), 877–892. Rao, N. V. R., Rao, N., Rao, S. P. K. & Schuling. R. D. (1993) Fluorine distribution in waters of Nalgonda district Andhra

Pradesh, India. Environ. Geol. 21, 84–89. Reghunath, R., Sreedhara Murthy, T. R. & Raghavan, B. R (2002) The utility of multivariate statistical techniques in

hydrogeochemical studies: an example from Karnataka, India. Water Res. 36(10), 2437–2442. Srikanth, R., Viswanatham, K. S., Ahsai, F. F., Fishahatsion, A. & Asmellash, M. (2002) Fluoride in groundwater in

selected villages in Eritrea (North East Africa), Environ. Monitoring Assess. 75, 160–177. Strunz, H. (1970) Mineralogische Tabellen, 5. Aufl. Geest und Portig, Leipzig, Germany. Stuben, D., Zsolt B., Chandrasekharam, D & Karmakar, J (2003) Arsenic enrichment in groundwater of West Bengal,

India: geochemical evidence for mobilization of As under reducing conditions. Appl. Geochem. 18(9), 1417–1434. Subbarao, C., Subbarao, N. V. & Chandu, S. N. (1996) Characterization of groundwater contamination using factor

analysis. Environ. Geol. 28(4), 175–180. UNDP/CGWB (United Nations Development Programme/Central Ground Water Board) (1976) Groundwater surveys in

Rajasthan and Gujarat, India, Tech. Report, United Nations. Wang, Y., Nahon, D., and Merino, E. (1993) Geochemistry and dynamics of calcrete genesis in semi-arid regions Chem.

Geol. 107, 349–351. Wang, Y., Ma, T. & Luo, Z. (2001) Geostatistical and geochemical analysis of surface water leakage into groundwater on

a regional scale: a case study in the Liulin karst system, northwestern China. J. Hydrol. 246(1/4), 223–234. Wedepohl, K. H. (1978) Handbook of Geochemistry, II-1, Section 9, Fluorine. Springer-Verlag, Berlin, Germany. WHO (1984) Guidelines for Drinking Water Quality, vol. 2, Health criteria and other supporting information. World

Health Organization, Geneva, Switzerland. Received 22 August 2003 accepted 26 June 2006

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