Materials And Methods

Water samples in duplicate from various potable sources comprising bore wells and open wells in 55 villages in the study area were collected during the postmonsoon period. In addition, premonsoon water samples collected from selected locations were used to study the temporal variations of different parameters. In addition, water samples from the hot spring were also collected in the pre-and postmonsoon periods. One set of samples was filtered and acidified with 2 ml of 35% HNO3 and stored in air-tight polyethylene bottles for use in the determination of pertinent cations; the unfiltered and nonacidified ones were used to determine the concentrations of anions, pH, electrical conductivity (EC), and total dissolved solids (TDS).

Water samples collected from the hot spring and potable sources were analyzed for fluoride, chloride, EC, and pH by Orion ion selective electrode model 1260. The instrument was calibrated using E-MERCK buffers of pH 4, 7, and 9, respectively. For fluoride measurement, the instrument was calibrated using 0.1 M standard sodium fluoride (NaF) solution; for chloride, 1 M chloride solution was used. Blank solutions made up from MILLI-Q water (resistivity: 10 to 15 MQcm; conductivity: <0.2 |s/cm; TOC: <30 ppb) were also analyzed. To each 50-ml sample, including the blank before analysis for fluoride, 2 ml of total ionic strength adjustment buffer (TISAB IV) was added. Similarly, 2 ml of ionic strength adjuster (ISA) was added to 50 ml of each sample and the blank, during chloride measurement. The buffer solutions helped in minimizing complex formation and buffered the solution pH to 5.2. The samples were continuously stirred using a magnetic stirrer during measurement.

The concentrations of Na, Ca, K, Mg, Al, and Fe were determined by analyzing the acidified water samples employing the Perkin-Elmer Model 3300 inductively coupled plasma optical emission spectroscopy (ICP-OES) at the Department of Earth Sciences, University of Western Ontario, Canada. Standard wet chemical methods [25] were employed in the determination of carbonate and bicarbonate concentrations in water samples. Sulphate and silica were determined by CINTRA-5 UV-VIS spectrophotometer. Results of analyses are presented in Table 7.1.

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