Hydrochemical study of Khanmirza plain aquifer in relation to geological formations (Chaharmahal and Bakhtiari Province)

Khanmirza aquifer is located in Khanmirza plain, south of Lordegan in Chaharmahal and Bakhtiari province. The study area is part of fold Zagrous and is located in south of Dena fault. Field and petrographic studies indicate various geological formations (limestone, dolomite, clay, gypsum, salt, sandstone and igneous rocks) from the Precambrian (Hormoz Formations) to the now. The 16 wells during 3 periods were analysis in 2016-2017, and also datas of periods 15 years to were studied. All data indicate to decreas water quality of the central and east part of the plain. Spatial zoning of hydrochemical parameters indicat geochemical evolution process of Khanmirza aquifer groundwater from calcium bicarbonate type (magnesium) with salinity low concentration in northwestern and southeastern and chloro-sodium type in the central part of the plain. The ion ratios of Khanmirza plain show the dissolution of gypsum and the saline water infiltration in around of the fault and the plain central. Results of heavy element analysis indicat to high concentration As = 0.08 - 0.11, Co = 0.52 - 0.46, Cd = 0.51 - 0.43, Fe = 17.17 - 60.57, Pb= 1.43 - 0.96 up several times the world standard. Tectonic setting and stratigraphic unites of the khanmirza are the most important factor of the groundwater heavy elements pollution. The evaporative formations of Hormoz in the east, and the clay formations and water persistence in the central part of the basin have caused salinity and accumulation of heavy metal in Khanmirza plain.