Assessment of Water Quality with respect to the Physicochemical Parameters and Trace Metals Contamination from Tarbela Dam, Pakistan

Abstract

Present study is based on the investigation of physicochemical parameters and trace metal concentrations in the surface water of Tarbela Dam, Pakistan in order to study their distribution, correlation, source apportionment and health risk assessment. The concentrations of trace metals in water samples were determined by flame atomic absorption spectrophotometry whereas physicochemical parameters were estimated as per standard methodology. The data were subjected to various statistical analyses to found the plausible correlations among the metals and various physicochemical parameters. Source apportionment of the metal data in the water samples was also carried out using principle component analysis and cluster analysis. Among the physicochemical parameters, pH of the water samples was found close to neutrality and strong associations were observed among most of the physicochemical parameters. Among the metals, higher concentration was observed for Ca, K, Mg and Na while least concentration was noted for Li. The selected metals showed following decreasing order; Mg > Ca > Na > K > Pb > Co > Fe > Mn > Sr > Cu > Ag > Cr > Cd > Zn > Li. The metal levels in water samples were also compared with the guideline values proposed by various organizations such as WHO, USEPA and Pak-EPA. Mean levels of all the physicochemical parameters were within the guideline values while average concentrations of Cd, Co, Cr, Mn and Pb were found to be higher than the standard limits. Significant strong clusters were observed among Ag-Cr, Fe-Mn, Co-Li-Cu, Pb-Sr, Cd-Zn, Ca-Na and K-Mg. The major pollution sources identified by multivariate PCA and CA were agriculture runoff, domestic wastes, lithogenic sources, soil erosion, automobile emission or transportation and natural weathering processes. Health risk assessment was calculated in terms of exposure of metals through ingestion and dermal absorption. Among the metals, Cd, Co, Cr and Pb exceeded the safe limit of hazard quotient so they can pose non-carcinogenic health risk through ingestion of water from Tarbela Dam, while levels of these metals were within the safe limit when measuring exposure through dermal contact. Among trace metals, significant carcinogenic risk was associated with Pb, Cr and Cd as these metals exceeded the safe limit, suggesting lifetime carcinogenic risk through ingestion of the water from the study area.