Physicochemical Characterization of Groundwater in Urban Areas of Lahore, Pakistan, with Special Reference to Arsenic

Abstract

The current quality status of groundwater from Lahore was investigated using standard analytical methodologies. The physicochemical parameters included in the study were pH, alkalinity, electrical conductivity, TDS, hardness, bicarbonate, nitrate, chloride, fluoride, sulphate, phosphate and turbidity. The metals included in the study were Na, K, Ca, Mg, Fe, Pb and As. The waters ranged in pH from 7.50 to 8.20 and in conductance from 329 to 1090 µS/cm. The alkalinity and TDS of the groundwater vary from 2.80 to 8.20 m.mol/L and 198 to 762 mg/L, respectively. Most of the water samples were found to be genuinely hard (100 to 300 mg/L hardness) and have rather low chloride and fluoride concentrations. The bicarbonate and nitrate ranged from 140 to 410 mg/L and 0.70 to 2.00 mg/L, respectively. The average metal concentrations followed the order; Na > Ca > Mg > K > Fe > As > Pb. For As, the concentration ranged from 24.6 to 71.6 µg/L, with the mean concentration of 36.0 µg/L, thus exceeding the upper permissible safe limit of As (10 µg/L) laid down by WHO and USEPA. The correlation study showed significant relationships among various physicochemical parameters and selected metal pairs. Multivariate cluster analysis was used for the apportionment of the measured variables and it revealed both natural and anthropogenic intrusion in the groundwater.