Evaluation of groundwater quality and heavy metal pollution indices in Bazman basin, southeastern Iran

Abstract

Bazman watershed and groundwater basin system is one of the major water sources which supplies water to Dalgan, Iranshahr and Bazman cities in Sistan and Baluchestan province of Iran. Due to the importance of groundwater quality in the basin, this research work centers on integrated approaches for characterizing hydrochemistry and suitability of groundwater quality based on heavy metal concentrations and physicochemical parameters in the study area. This work has also highlighted the importance of an integrated approach combining pollution evaluation indices and multivariate statistical methods in pollution studies of groundwater to examine the groundwater quality and to identify the pollution sources. In the study area, assessment and measurement of groundwater hydrochemical parameters such as pH, total dissolved solids (TDS), electrical conductivity (EC), temperature (T), oxidation-reduction (Eh) and dissolved oxygen (DO), major cations (K+, Na+, Ca2+ and Mg2+) and major anions (Cl−, HCO3−, SO42− and NO3−) were performed. Evaporation was concluded to be the mechanism controlling groundwater chemistry mainly due to arid climate of the region and also in part due to anthropogenic activities. In the present study three major hydrochemical facies of water were identified in the water samples: Na- Cl, Na- HCO3 and Ca- Cl. Also, four pollution indices were selected to evaluate the extent of heavy metal pollution, heavy metal pollution index (HPI), heavy metal evaluation index (HEI), contamination index (Cd), and modified-heavy metal pollution new index (m-HPI) for nine heavy metals (As, Ba, Cr, Cu, Fe, Mn, Ni, Se and Zn) in the study area. The indices showed that most of the water samples are low and moderately contaminated and overall contamination levels are not dangerous. The principal component (PCA) and correlation analyses demonstrated that anthropogenic (i.e. surface runoff and agriculture fertilizers) sources and natural/geogenic processes (i.e. rock– water interactions) are responsible for variation of physicochemical parameters in groundwater aquifer. The results of the present study provide information useful for the water resource management in areas similar to Bazman that are particularly undergoing anthropogenic activities.