SPATIO-TEMPORAL VARIATION OF SELECTED HEAVY METALS IN DRINKING WATER SYSTEMS OF CENTRAL HUNZA, GILGIT-BALTISTAN, PAKISTAN

Heavy metals contamination in drinking water due to natural and anthropogenic sources is one of global issue. This study aims to evaluate the variation in drinking water quality of four major water systems (community tapes, open water channels, water storage tanks and traditional wells), in eight different villages of central Hunza, northern Pakistan. The water samples were evaluated for selected physical parameters and heavy metals (Ar, Cd, Cr, Cu, Hg, Fe, Pb and Zn) via Atomic Absorption Spectro-photometer to detect any pollution sources and were compared with permissible limits set by WHO for any possible threats to public health due to contamination. The samplings were carried out during summer and winter season. The results revealed that certain physical parameters of drinking water i.e., turbidity of 44.79% samples, pH of 5.21% and electrical conductivity of 10.97% samples go against the WHO permissible limits and Pakistan EPA standards and on the other hand, Ar (30.25%), Cd (35.94%), Cr (80.85%), Cu (31.25%), Hg (98.56%), Fe (7.27%), Pb (50%) and Zn in 16.67% samples exceed the permissible limits. Kruskal Walis test indicated that most of the investigated parameters were significantly higher in summer seasons (except pH, Pb), varied with locations (except temperature, EC, Ar, Fe, Cr, Hg) and sources (except Cu, Fe, Pb, Cr). Source-wise means concentrations of toxic heavy metals were observed highest during summer season as compared to winter. Therefore, this study suggests that drinking water should be regularly monitored for heavy metals contamination in order to prevent excessive build-up of these elements in the human food chain, causing numerous ailments.