عنوان مقاله [English]
The hydrogeochemical methods are used to determine of the dominant natural processes governing the groundwater hydrogeochemistry and the effects of the hydrocarbon pollution on groundwater quality in Kuhdasht aquifer. Groundwater samples were collected in four periods in 2014 (16 and 25 water wells in three and one periods, respectively) to measure the electrical conductivity, major ions concentrations, trace ion and pollution indices concentrations (I, Fe, Zn, Ba, dissolved oxygen, chemical and biochemical oxygen demand (COD and BOD), and pH), and hydrocarbons. After review of the geology and hydrogeology of the study area, hydrogeochemistry of the aquifer was studied as determination of hydrochemical types of waters, interpretation of hydrochemical maps and composition diagrams with emphasis on the natural changes in groundwater hydrochemistry and abnormal changes as a results of the hydrocarbon contamination. The results show that the geochemical evolution of groundwater in Kuhdasht plain changes from HCO3-Ca(Mg) to HCO3(SO4)-Mg water types together a gradual increase of the concentrations of dissolved ions, with the anomalous Na-Cl water types in the hydrocarbon contaminated groundwater in southwest parts of the plain. The main hydrochemical characteristic of the groundwater in the areas affected by oil brines in the south west Kuhdasht are the highly reducing environment with high concentration of BOD, and COD and low concentrations of DO and NO3, and high concentrations of TDS, Na, Cl, B.