Hydrochemistry and contamination of groundwater resources in the Behbahan plain, SW Iran

The Behbahan plain with an area of 1320 km² is located in an arid to semi-arid zone. Since it has restricted water resources, the preservation of groundwater quality is of great importance. In order to investigate the contamination possibility which could be resulted from geogenic and anthropogenic sources, 30 wells were sampled during August 2014. The water samples were analyzed for heavy elements As, Cd, Fe, Mn, Zn, Sr, Pb, Se, Co, B and Cr, anions Cl⁻, SO₄ ²⁻, HCO₃ ⁻, CO₃ ⁻, NO₃ ⁻, cations Ca²⁺, K⁺, Mg²⁺ and Na⁺, and important quality parameters including pH, EC and TDS, using ICP-OES, FAES, OAS, titration, conductometry and drying methods. The concentration of major ions in most of the samples exceeds the allowed levels of WHO standard for drinking water. Geochemical data show that the water chemistry is influenced dominantly by weathering and dissolution of carbonate and evaporitic minerals, ion-exchange processes, and human activities. Groundwater in the Behbahan plain is mainly of calcium-sulfate facies, according to Piper diagram. The concentrations of nitrate and K show little correlation with that of major ions, suggesting unnatural sources for them. These components originated possibly from dissolution of nitrate- and K-bearing fertilizers used in farming. Geochemical maps indicate that concentration of toxic trace elements such as Pb, Cd, Cr, B, As and those of SO₄ ²⁻, NO₃ ⁻, Cl⁻ and Na⁺ ions have incremental trends. These high concentrations are caused probably by domestic and industrial waste waters leaked into the groundwater aquifer. The heavy metal pollution index (HPI) in 29 samples is greater than 100, indicating that groundwater in the study area is highly polluted with heavy elements.