Evaluating Hydrogeochemical Processes Regulating Groundwater Quality in an Unconfined Aquifer

Abstract

Hydrogeochemistry of groundwater was investigated to understand groundwater quality for drinking and irrigation purposes in an unconfined aquifer located in Jangal plain, NE Iran. Groundwater samples were collected and analyzed for determining physicochemical parameters (TDS, EC and pH) and concentration of major ions (Na+, K+, Ca2+, Mg2 +, Cl−, HCO3 −, SO 4 2 − and CO 3 2 − ). Water quality assessment parameters including SAR, Na%, RSC, TH and SI were also calculated. TDS, EC, Na+, K+, Cl− and SO 4 2 − levels in all samples were greater than the maximum permissible limit, while pH, Ca2 +, Mg2 + and HCO 3 − levels in most samples were within the standard range. Based on the Piper diagram, most groundwater samples were classified into Na-Cl as dominant water type. The saline water intrusion, evapotranspiration, ion exchange reactions and dissolution of carbonate minerals were found as the main processes controlling the chemistry of groundwater. According to the calculated parameters and the Wilcox and USSL diagrams, high salinity and alkalinity of the groundwater resources pose a major problem for irrigation use. It is obvious that the groundwater unsuitability threatens sustainable crop production and soil quality. Hence, urgent management of groundwater resources is suggested to avoid harmful effects on inhabitants.