Hydrochemical and environmental isotopes characteristic of groundwater and controlling factors for waters’ chemical composition in the iron–copper mine area of Elazığ, SE Turkey

Abstract

Environmental context Predicting the hydrodynamic structure of water resources based on water chemistry and isotope results is important for understanding their transport and effects on the hydrogeological system. According to the results of this study, hydrogeological characteristics of ground and surface water resources in the Zeryan Stream sub-basin in the iron–copper mining area and their geochemical evolution are mainly controlled by the weathering of silicate and carbonate minerals, and ion exchange. Rationale and hypothesis Groundwater is generally the most important water resource in mine areas, and its circulation processes need to be studied in detail for rational resource exploitation. This work tested the hypothesis that the evolution of groundwater chemistry and recharge by using hydrogeochemical indicators and isotope tracers together are affected by the hydrogeochemical processes that may have taken place during the water-rock interactions in the Zeryan Stream Sub-basin, where the Iron-Copper mine is located. Methodology It used approaches such as hydrochemistry, Piper diagrams, saturation index, ionic ratios, and environmental isotopes to analyze groundwater origin and hydrochemical processes affecting water chemistry. Fifty-seven water samples were collected from 19 points during wet and dry periods. Results Results indicated that the dominance of cations and anions in the mine water follows the trend Mg2+ > Ca2+ > Na+ > K+ and SO42− > HCO3− > Cl−,  and most of the water samples are Mg-Ca-HCO3-SO4, Mg-Ca-SO4-HCO3, and Ca-HCO3. Discussion Evaluation of analyzed groundwater chemical data showed that dissolution or precipitation of silicate minerals dominated in the hydrochemical evolution of groundwater, dissolution of carbonate minerals was a secondary process and to a lesser extent, ion exchange processes played a role.  The δD and δ18O isotopic contents indicated that the water samples were controlled by local atmospheric precipitation, and affected by secondary evaporation during the recharge process. Tritium levels indicated some well waters are recharged from older groundwater resources from water-rock interaction and residence time. Findings The findings of this study were provided to decision-makers in order to design sustainable implications for groundwater utilization based on the sub-basin.