Geochemical Characterization Of Groundwater In Tehsil Takht-E-Nasrati, Karak, Pakistan

Abstract

This study provides a comprehensive insight into the geochemical characterization of groundwater in the tehsil Takht-e-Nasrati of district Karak, Pakistan. The study aims to evaluate the major and trace elements in groundwater and to find the potential source of contamination by assessing the soil and rocks geochemistry of the study area. Standard physiochemical parameters (Potential of Hydrogen (pH), Electrical Conductivity (EC), Total Dissolved Solids (TDS), & Salinity) and laboratory-geochemical analysis of groundwater, soil and rock samples have been carried out to evaluate the major and trace elements for the water quality assessment and potential source of contamination. The pH of groundwater samples ranges from 6.8-8.19 within the permissible limit, while other field parameters EC, TDS, and salinity above the WHO permissible limit in some locations with the range of 270- 4960, 191-3520, and 128-3330 uS/cm, respectively. In major parameters, nitrate (0.3-14 mg/L) and sulphate (0.12-140 mg/L) are within the acceptable drinking limit while other parameters including calcium, magnesium, sodium, chloride, sodium chloride, total hardness and alkalinity ranges from 30.4-620, 138-894, 11.55-1587, 17.75-2450, 29.25-4037, 230- 1450, and 60-260 mg/L, respectively, are above the permissible limit in few locations. The trace elements in the rocks geochemistry following the concentration trend of Mn>Cr>Zn>Co>Ni>Pb>Cu>Cd. In the soil sediments, Mn range from 114-228 mg/L is higher from all the other trace elements and makes a quantification trend of Mn>Zn>Cr>Co>Ni>As>Pb>Cu>Cd. In groundwater samples, Zn (0.01-0.45 mg/L) is within the acceptable range whereas, Mn, Cr, and Pb range from 0.2-0.65, 0.07-0.3, and 0.11-0.95 mg/L, respectively, are above the permissible. In some locations, Cu, Co, Ni, Cd and As values are above the permissible limit having range of 0.76-2.54, 0.02-0.06, 0.01- 0.24, 0.006-0.08, and 0.03-0.31 mg/L, respectively. Trace elements showed the groundwater contamination trend of Mn>Cr>Pb>As>Cd>Co>Cu>Ni>Zn. The statistical approaches demonstrate that main possible source of groundwater contamination is the natural geogenic rocks of Siwalik Group. Cu-bearing rocks are the possible reason of Cu contamination distributed through the groundwater recharge by River Kurram. In the anthropogenic sources, the excessive fertilization in farming, poor piping network for irrigation and domestic purposes might have contributed the trace elements into groundwater.