The investigation of hydrogeochemical characteristics of the Kelkit and Köse district centers drinking waters and their relationship between the surrounding rocks

The study areas are located of Kelkit and Köse District centers in the south of Gümüşhane (NE Turkey) and their surroundings. In this study, hydrogeochemical features and metal elements of drinking waters in Kelkit and Köse district centers were examined. In addition, the lithologies in which the water passes through were determined and the relationships between the source of drinking water and the side rock were examined. Water samples were generally collected from water reservoirs and sources on Alluvium, Kelkit Formation, Berdiga Formation and Köse Granite. The pH, conductivity and hardness values of the samples vary between 7.50-8.09, 166.9-1386 µS/cm and 8.4-70.8 °F, respectively. According to the classification of the continental surface water resources, these data indicate that the waters are of I, II and III quality and indicate a basic character rather than an acidic environment. In addition, the hardness results showed that the water samples in Kelkit area were soft, medium hard and hard water, while the water samples in Köse area were hard, medium hard and very hard water. The physical parameters of water for all samples are suitable in terms of color, turbidity, taste and odor values. The waters in the study area are generally classified as carbonated (Ca+Mg > Na+K) and sulfated waters and generally, their weak acid roots are more than strong acid roots (HCO3¯ > SO42+Cl¯). The lines that combine the meq/l values of the ions of all the samples coincide or pass in parallel, indicating that the source of water supply is the same and is not affected by seasonal changes. In addition, Ca, Mg, Na, K, Fe, Mn and Al values of the studied samples are generally within the permissible range and comply with TS-266 and World Health Organization (WHO) standards. These values also show similar distribution with the drinking water values of Gümüşhane Province. The distribution of dissolved metals (Zn, Cu, Co, Ni, Pb) in the samples is directly related to the rock types and mineralizations in the study area and its vicinity. Except for a few, other samples were distributed within acceptable limits. The chemical composition of waters seems to be controlled by water-rock interactions, such as the dissolution of carbonates (limestone and dolomite), weathering of gypsum, as well as ion exchange processes (Mg+2, Ca+2, Cl¯ and HCO3¯) which explain the observed variability. In addition, it was found that SiO2 in the samples passed into the waters as a result of albite decomposition. As a result, it was determined that most of the samples were in the category of good class waters in terms of drinking water.