Environmental isotope and chemical characterization of groundwater in Islamabad

52 groundwater samples were collected from tube-wells and hand-pumps installed in the jurisdiction of Islamabad city. Samples were analyzed for various pollution parameters such as the physiochemical parameters (E.C., redox, pH, dissolved oxygen), stable isotope parameters (/sup 13/C/sub TDIC/ and /sup 18/O, /sup 2/H of water), as well as major cation and anion (HCO/sub 3//sup -2/. SO/sub 4//sup -2/. Cl/sup -/, Na/sup +l/, K/sup +1/, Ca/sup +2/, and Mg/sup +1/. Electrical conductivity of a majority of these samples was found to lie in the range of 429- 950 micro S/cm. Most of the groundwater samples have nearly neutral pH values. Concentration of anions and cation in shallow groundwater lies in range of HCO/sub 3/ (259-345 ppm), SO/sub 4/ (8-26 ppm), Cl (16-43 ppm), Na (19-33 ppm), K (0.3-2.1 ppm), Ca (65-93 ppm) and Mg (14-22 ppm) respectively. For deep groundwater samples, these values are in range HCO/sub 3/(218-356 ppm), SO/sub 4/ (9-41 ppm), Cl (13-58 ppm), Na (9-58 ppm), K (0.8-6.1 ppm), Ca (62-102 ppm), and Mg (10-26 ppm) respectively. The delta /sup 13/C values lie in the range of -6.2 to -2.0 % V- SMOW for deep groundwater and -5.3 to -3.6 % V- SMOW for shallow groundwater. The delta /sup 13/C values of Total dissolved Inorganic Carbon (TDIC) lie in the range of -8.2 to- 1.18 % PDB for tube well samples and -7.3 to -1.8 % PDB for shallow wells. Depleted values of delta sup 13/C indicate domestic waste input in groundwater. Delta /sup 13/C values in the range of -3 plus minus 2 % PDB represent limestone dissolution as the main source of dissolved inorganic carbon. In view of the neutral pH range (pH=7 plus minus 0.5) of water samples collected in the Islamabad area, bicarbonate is the main dissolved inorganic carbon (DIC) specie in groundwater with delta /sup 13/C values up to -8.3 % PDB. In general most of the water samples are suitable for drinking with respect to physiochemical and major cation and anion. (author)