Impact of water-rocks interaction on groundwater geochemistry of southern mor range, balochistan, pakistan and its appraisal for drinking water quality

Major and trace element geochemistry of groundwater of southern Mor Range, Balochistan was made to insight the impact of igneous and sedimentary rock on the composition of groundwater. The median values of ions display Na+> Mg2+ >Ca2+>K+ and HCO3 ->SO4 -2>Cl->CO3 -2 trend in the distribution of cations and anions respectively. The plots on Piper diagram indicated Ca- Na-Cl-type water (40.84%) as dominant water facies, followed by Ca-Cl-type (18.36%), Ca-Na- HCO3-Cl-type (16.33%), Ca-HCO3-Cl-type (12.24%), Na-Cl is (10.20%). The plots on Gibbs'diagrams delineate rock weathering combined with evaporation process for regulating the ionic composition. Molar ratio of Ca2++Mg2+ vs. HCO3 -+SO4 2- and Ca2+/Na+ vs. Mg2+/Na+ demonstrated that the groundwater of the study area has genetic association with the igneous rocks of Bela Ophiolite and sedimentary rocks of Ferozabad Group. Strong correlation matrix and PCA diagram also witnessed genetic affiliation with the rocks of the study area. The ionic composition revealed, nearly 50% samples faced process of ion exchange. Estimation of selected trace elements (Fe, Zn, V, Mn, Cu, Pb, Cr, Ni, As and Co) was also done to evaluate the drinking water quality and their possible health implications. Majority of them was found within permissible limits; however, in some of the samples, Fe, V and Pb exceed the WHO specifications. (author)