Quality of groundwater resources in Fariman- Torbat-e-Jam plain

In order to assess the quality of Fariman-Torbat-e-Jam groundwater resources and investigate the factors affecting the quality of groundwater, 26 groundwater samples (depth of tube wells between 70 and 260 m) were collected and analyzed for major ios, nitrate, and potentially toxic elements. pH and electrical conductivity were measured at the field. The type and facies of the samples changed from Na-HCO3 in the recharge zone to Na-Cl in the middle of the plain, and finally to Na-SO4 in the discharge zone. The results indicated the water equilibrium with carbonate minerals (calcite, dolomite, and aragonite); evaporation, dissolution and reverse ion exchange are the natural factors affecting the chemical composition of the samples. The study samples are classified as intermediate to high saline waters (class III, EC between 1300-3000 µs/cm) and are suitable for irrigation crops which can tolerate saline waters. The calculation of water quality index (WQI) revealed that the groundwater of the recharge zone (exposure of limestone rock units) is suitable for drinking usage, whereas the quality samples collected from the discharge zone (exposure of shale and evaporate rock units) is too weak. Calculation of Langelier Index indicated that the samples are not suitable for industrial applications. The Torbat-e-Jam aquifer is polluted with As, Pb (>10 µg/l), and Cd (>3 µs/cm) mainly because of natural (exposure of shales and volcanic rocks) and anthropogenic factors (agricultural practices and discharge of residential wastewaters.