Groundwater geochemistry evolution and geogenic contaminants in the Sulaimani-Warmawa Sub-basin, Sulaimani, Kurdistan Region, Iraq

Evolution of groundwater geochemistry in the Sulaimani-Warmawa Sub-basin in the Kurdistan Region of Iraq has been investigated using hydrogeochemical and isotopic methods. This is a semiarid region with seasonal precipitation in winter. Water chemistry generally evolves from Ca-HCO 3 groundwater type close to the basin boundaries towards Ca-Mg-HCO 3 groundwater type close to the Tanjero River along the axis of the basin. Some samples have increased concentrations of Na, Cl, and SO 4 as a consequence of dissolution of halite and gypsum embedded in carbonates. Values of pH are slightly alkaline or alkaline, and redox parameters indicate a moderately reducing environment. Isotopes δ 2 H and δ 18 O indicate recharge from winter precipitation with no evaporation. Values of dissolved 13 C(DIC) correspond to equilibrium with carbonates and C4 plants as the source of CO 2 . Values of 87 Sr/ 86 Sr in groundwater are in a good agreement with carbonate dissolution as a principal process. The principal geogenic contaminant is Ba with concentrations up to 0.383 mg/L. Dissolved concentrations of other geogenic contaminants such as As, F, Mn, and Cr are low or below the detection limit as expected based on their low contents in carbonate rocks. Inverse geochemical modeling on selected profiles calibrated using δ 13 C values provided mass transfer coefficients for possible geochemical reactions. Future work should focus on interactions in the hyporheic zone of the Tanjero River.