Groundwater quality assessment for drinking purpose: a case study from Sindh Industrial Trading Estate, Karachi, Pakistan

Drinking water quality assessment is an essential tool to address suitability of drinking water and condition of aquifer environment. This study is aimed to assess the groundwater quality in the Sindh Industrial and Trading Estate (SITE) area of Karachi. We have collected groundwater samples from 24 boring wells, at different depth ranging between 100 and 150 ft., and tested for various physicochemical parameters. We have analyzed the spatially distributed groundwater samples in the under study area by following multi-field assessment (statistical estimation, spatial mapping, and hydrofacies distribution). Water quality is evaluated through physical parameters (pH, electrical conductivity, total dissolved solids, total hardness, turbidity) and chemical parameters, including major ions (sodium, potassium, calcium, magnesium, chloride, sulfate, bicarbonate, nitrate), minor elements (iron, manganese), and trace elements (zinc, nickel, cobalt, chromium, and copper). The concentration of parameters is varying with following range: pH (6.95-7.84), EC (4050-35,600 mu S/cm), TDS (2020-17,800 mg/L), TH (890-8100 mg/L), Na (123-930 mg/L), K (10-68 mg/L), Ca (340-8260 mg/L), Mg (176.17-1725.9 mg/L), Cl (1028.05-15,420.75 mg/L), SO4 (122-960 mg/L), HCO3 (1900-5025 mg/L), NO3 (35.52-227.08 mg/L), Fe (41-79 ppb), and Zn (32-1638 ppb). The results of physiochemical parameters were subsequently compared with national and WHO standards. All the sample results were found above the prescribed standards, except the pH level. These parameters were interpolated through ArcMap tools, which showcase the spatial distribution of water quality in the study area and helped us to identify the anomalous water quality parameters. The Piper diagram used to model the ionic relationship and relative concentration of the major cations and anions dissolved in the groundwater samples. The data show the variability among six hydrochemical facies; Ca-HCO3 type (n = 7), Ca-Cl (n = 7), Na-HCO3 (n = 5), Na-Cl (n = 2), Ca-SO4 type (n = 2), and Mg-Cl (n = 1). This baseline study will signify in monitoring groundwater quality of SITE area and provide footnotes to investigate the variability of hydrofacies and diffusion of industrial discharge in hydrological environment of shallow aquifer in the study area.