Isotopic and chemical characterization of groundwater of Mailsi district Vehari (T-1306) (MFN 4275)

Abstract

The present work is aimed at assessing the ground water quality of tehsil Mailsi for the very first time. Twenty seven (27) ground water samples were collected for physico chemical (pH, electrical conductivity, total dissolved solids and dissolved oxygen), chemical (CO3, HCO3 -1 , Cl-1, NO3 -1, SO4 -2, Na+, Mg+, K+ and Ca+), heavy metal (Zn, Cd, Pb, Cu, Ni, Cr and Co) and stable isotopic (������������O����and ����D)����analysis. Physico chemical analyses were performed in-situ by the help of portable meter. CO3, HCO3 -1and Cl-1 were carried out by titration. Nitrates and sulphates were measured by Ion Selective electrode and UV Spectrometer respectively. Heavy metal analysis was carried out by polarograph 797 Computrace by VA-83 using Hanging Mercury Dropping Electrode (HMDE). The stable isotope analyses were performed using a modified Varian Mat GD-150 Mass Spectrometer. pH, EC,TDS and DO of groundwater samples were found in the range of 7.30-8.12, 526 - 2410 μS/cm, 272 - 1667mg/L and 2.5 - 3.5 mg/L respectively. Concentration of Cl-1, NO3 -1, SO4 -2, and HCO3 -1 were in the range of 19.3 - 287.12 mg/L, 1.0 - 114.57 mg/L, 0.2 - 37.13 mg/L and 304.39 - 778.36 mg/L respectively. However, due to dominance of limestone in the area CO3 were absent in the groundwater of Mailsi. Hydro chemical analysis by Piper diagram showed the ground water of Mailsi is Na-HCO3 type and has less impact of sulfate and chloride. Whereas 18.5% zinc, 25.9% lead and 14.8% copper were found higher than permissible limit. The overall results shows that the total dissolved solids and nitrates are very high in Mailsi ground water samples and can have adverse effects on individuals. The water quality index (WQi) calculation based on four parameters (pH, TDS, DO and NO3 -1) of the groundwater of Mailsi was carried out. The results indicate a dominance of poor water quality and harmful for drinking purposes. The ����18O values of groundwater ranges from -8.4 to -4.1 with the average of -7.3 and the ����D range from -57.5 to -2.1 with the average of -50.5. Isotopic data for Mailsi groundwater lie on Local Metroic Waterline (LMWL) and Global Metroic Waterline (GMWL) which reflects that aquifer system is recharged by precipitation and river. In most part of study area the ‘d-excess’ values in groundwater samples are less than 10 indicating high evaporation rate. Relationship between ����18O and the d-excess in t