Geochemical processes in groundwater chemistry: a case study

Determining the influence of natural processes on the geochemical evolution of groundwater is vital for the sustainable management of groundwater. In this study, the main factors controlling the evolution of groundwater chemistry were identified by hydrogeochemical assessments in the Güneşli plain of Kayseri province (Turkey), where different water types have been identified. Different diagrams, saturation indices were used the identification of the origin of the solutes, the relationships between dissolved species allowed and the processes that generated the observed water compositions in the plain. In general, the HCO3− ion seemed to be predominant in the waters. Groundwater interacts with carbonate rocks of the Güneşli plain, resulting in a generally important increase of concentrations of major ions (Ca2+, Mg2+ and HCO3−), thus indicating that mineral dissolution was not the only process that occurred along this groundwater flow path. More than 87% of the samples showed calcite, dolomite and aragonite minerals saturation, linked to interactions with carbonate rocks. Moreover, increases in Na+ and K+ detected in some samples indicate the presence of clay and evaporite minerals. SO42− and Cl− increases were due to evaporite minerals and volcanic units such as tuff and ignimbrite. It has been determined that the main factor controlling the chemical structure of groundwater in the study area was the water–rock interaction processes. In these processes, it was determined that carbonate weathering is dominant in the alluvial aquifer, while silicate weathering processes were present in the volcanic and evaporite units. Ion exchange processes were also effective in the alluvial aquifer due to clay minerals.