Statistical and Geospatial Assessment of Groundwater Quality in the Megacity of Karachi

摘要

Inserting Groundwater quality variability and sources potentially contributing to aquifer recharge was evaluated in metropolitan Karachi. Selected sampling sites were characterized by large waste dumping sites, industrial zones, and the presence of open streams receiving heavy loads of industrial and domestic wastes. Levels of pH, electrical conductivity (EC), fluoride (F~-), chloride (Cl~-), bromide (Br~-), nitrate-N (NO_3~--N), sulfate (SO_4~(2-) ), sodium (Na~+), potassium (K~+), calcium (Ca~(2+)), magnesium (Mg~(2+)), and ammonium (NH_4~+) were determined and compared with the WHO permissible limits. Concentrations of the measured ions were in the order of Cl~- > Na~+ > SO_4~(2-) > Mg~(2+) > Ca~(2+) > NO_3~--N > K~+ > F~- > Br~-. EC values were above the WHO guidelines, representing the presence of high ionic concentration in the groundwater. The health risk index (HRI) for NO_3~--N indicated that inhabitants of Karachi are at risk of high NO_3~--N exposure. Ingestion of high concentrations of NO_3~--N in water can cause methemoglobinemia and birth defects. Results of multivariate statistical analysis, principal component analysis (PCA), cluster analysis (CA), and geographic information system (GIS) map analysis revealed that human activities are leading to adverse effects on the existing groundwater quality in Karachi.