In Karachi city presence of elevated concentration of various pollutants from natural and anthropogenic sources has caused the acute shortage of safe drinking water. The physicochemical data of different aquifers of Karachi were examined to elucidate the geochemistry and identify natural and anthropogenic processes controlling the quality of groundwater. Twenty four groundwater samples were collected from different localities of SITE area of Karachi. Physical and chemical characteristics of groundwater were determined using standards methods. Minor and trace metals (Fe, Zn, Co, Cu, Ni, Cr) were also determined to know the geochemical conditions of aquifers. Data was interpreted using multivariate statistical analysis. Groundwater of the area is mainly saline and 80 % water samples contain TDS above 500 ppm. Aquifers are dominated by HCO3 and Ca-Cl hydrofacies, which shows impact of seawater intrusion. Lateral distribution of groundwater pollution was investigated using Inverse Distance Weighting (IDW) technique using ArcMap, which indicates displacement of freshwater with seawater. In addition calcite and gypsum dissolution were also played a vital role to increase the salinity of the water. At few places mixing of sewage water and leaching through surface solid waste were also evident. Zinc concentration was high in 88% water samples. Lateral distribution of physicochemical parameters shows great heterogeneity, which indicates influence of local geology and land use pattern.

Aneeq Mahmood Abbasi, Sanober Rafi, Sadaf Naseem and Yusra Rehman