**5.6 Dental survey**

A questionnaire pre-format prescribed by Rajiv Gandhi Drinking Water Mission [18] and earlier described by Dahyia et al. [19] was used to score the incidence and degree of manifestation of dental fluorosis. Clinical dental examination was executed rendering to the requirements defined by the World Health Organization Formational Oral Health Surveys [20] by taking 10 minutes as an orientation period spell for the basic examination of a child. The test area was prepared with the required hygiene and safety measures, using previously sterilized instruments and having easy access to sterilization procedures, and using a plane mirror and a periodontal probe. Community fluorosis index (CFI) was calculated based on equation [1] as

$$\text{CFI} = \frac{\text{Number of people} \times \text{Deans numerical weight}}{\text{Total number of people}} \tag{1}$$

The symptoms of dental fluorosis among the communities were recorded using, randomized sampling method. The results were classified into seven categories based on the Dean's classification viz., normal, questionable, very mild, mild, moderate, moderately severe, and severe. The classifications were given a numerical weights of 0.0, 0.5, 1.0, 1.5, 2.0, 3.0, and 4.0, respectively, in order of increasing severity [21–24].

#### **5.7 Urine sample collection and analysis**

A total of 50 urine samples (one sample from each location where the groundwater samples were collected) were collected from the children of same age group (10–12 years age group). The samples were further classified into high (>1.5 mg/L), intermediate (0.6–1.5 mg/L), and low F (<0.6 mg/L) based on groundwater F content. Pre-labeled 500-ml plastic-capped disposable bottles (prewashed and dried containing 0.2 g of ethylene diamine tetra-acetic acid, EDTA) were distributed to the selected persons in the villages of the study area and brought to the laboratory in an ice box and stored at 4°C in a refrigerator. EDTA (0.2 g) was added to check and minimize the interference from complexation of F by cations such as calcium. The samples were analyzed for F content using the 2-(parasulfophenylazo)-1,8-dihydroxy-3,6-naphthalene-disulfonate SPADNS method. The individuals were also explained the importance of the program and were motivated to cooperate in this study. An informed consent was obtained from the participants. Information on the drinking water sources, dietary practice, period of living in a particular location, and other related data were collected through an open-ended questionnaire.

### **6. Results and discussion**

#### **6.1 Hydrogeochemical evolution**

A trilinear diagram is widely used in understanding the hydrogeochemical evolution of groundwater [17]. The diagram consists of two triangles and one diamond-shaped field. The left side triangle is for plotting of cations (Ca2+, Mg2+ and Na+ + K+ ) and the right side triangle for plotting of anions (HCO3 − + CO3 2−, Cl− , and SO4 2−) expressed in

**Figure 3.** *Hydrogeochemical facies during pre-and post-monsoon periods.*



*Fluoride Geochemistry and Health Hazards: A Case Study DOI: http://dx.doi.org/10.5772/intechopen.105156*

percentage. The diamond-shaped field (consisting of the total cations and anions), which is the upper side of these two triangles is used for representing the overall chemical quality of groundwater. The Zone-5 represents carbonate hardness (Ca2+ : HCO3 − type), zone 6 non-carbonate hardness (Ca2+: Cl− type), the zone-7 noncarbonate alkali (Na+ : Cl− type), the zone-8 carbonate alkali (Na<sup>+</sup> : HCO3 − type), and the zone 9 mixed types. The chemical data of the groundwater samples are plotted in the Piper's diagram (**Figure 3**). Most groundwater samples fall in the center as well as in the right lower corner of the cation triangle in both the seasons. It indicates the high concentration of Na<sup>+</sup> in the groundwater.

Most of the anions in pre-and post-monsoon groundwater samples fell in center of the triangle representing HCO3 − type. Therefore, the groundwater is dominated by Na<sup>+</sup> -HCO3 − facies in general, which is further supported by hydrogechemical facies (**Table 3**). In the centrally located diamond-shaped field, the groundwater samples fall in zones 5–9. It suggests that the fresh water (zone 5) moves towards saline water (zone 7) through the zones of 6–8, following the flow path. That means the initial water quality is controlled by water-rock interaction and is subsequently modified by anthropogenic sources. Because of this, the concentrations of Na<sup>+</sup> and Cl<sup>−</sup> increase, which enhance the TDS content, are including the F content in the groundwater.

#### **6.2 Mechanisms controlling groundwater chemistry**

To understand the groundwater interaction with precipitation (rainfall), rock, and evaporation as mechanisms controlling the water chemistry [25], the ratios for major cations (Na<sup>+</sup> + K<sup>+</sup> : Na<sup>+</sup> + K<sup>+</sup> + Ca2+) and for major anions (Cl− : Cl<sup>−</sup> + HCO3 − ) computed from the ionic concentration of groundwater of the study area are plotted against TDS (**Figure 4**).

Most groundwater samples fall in the rock domain in both the seasons, where the TDS is between 100 and 1000 mg/L (**Figure 4**). The remaining groundwater samples

#### **Figure 4.** *Mechanisms controlling groundwater chemistry (after Gibbs [25]).*

are observed from the evaporation domain, where the TDS is more than 1000 mg/L. Falling off the groundwater samples in the rock domain indicates the water-rock interaction. The average values of TDS, Na+ , HCO3 − , and Cl− vary from 844 to 981, 107.8 to 94.5, 271 to 284.75, and 95.4 to 88.5 mg/L from pre- to post-monsoon, where the TDS is less than 1000 mg/L, while they are from 1402 to 1583, 306.68 to 380.54, 408.2 to 430.17, and 239.2 to 278.85 mg/L in the respective seasons, where the TDS is more than 1000 mg/L (**Table 4**). The increase of Na+ and Cl− from TDS less than 1000 mg/L to TDS more than 1000 mg/L concentrations are mainly caused by anthropogenic pollution. Because of this reason, the groundwater samples move towards the evaporation domain from the rock domain, as also reported by Wang et al. [26], Mamatha and Rao [27], Li et al. [28], and Narasimha and Sudarshan [29] in other regions (**Figure 4**).

Since the groundwater quality is dominated by Na+ and HCO3 − ions due to rockwater interaction, this factor appears as governing process for the release of F from the country rocks. As a result, the groundwater shows the higher F content. Similar conditions have been reported by Li et al. [30] in China. On the other hand, the evaporation and/or anthropogenic activity increases the Na<sup>+</sup> and Cl− contents, which make the higher TDS.
