Redox conditions and groundwater quality issues of selected alluvial aquifers in Serbia

Redox conditions are an important regulator of aqueous biogeochemistry and knowledge about them is crucial for an understanding of the fate and occurrence of nitrates, emerging substances, and organic compounds in shallow groundwater. The aim of this paper is to determine redox categories, along with prevailing redox processes, and the differences in groundwater quality between shallow alluvial aquifers of Serbia's major rivers. The research was conducted on public water-supply wells in the alluvial plain of the Velika Morava River, the Danube River, the Tisa River and the alluvial aquifer of the Sava River. The study period is 2010-2014 and the number of collected and analysed samples 243. The redox categories and processes are characterised by concentrations of aqueous redox species (dissolved oxygen, nitrate, dissolved iron, manganese, and sulphate and sulphide concentrations). Parameters such as Eh, total organic carbon, HCO3-, pH, total iron concentrations, temperature and specific conductivity were also analysed. Different geological and hydrogeological settings, groundwater abstraction, distances between the wells and the river, well depths, and anthropogenic impacts result in diverse redox conditions. Groundwater in selected alluvial aquifers is mostly defined as anoxic, with one predominant process, or mixed anoxic, with various redox processes occurring simultaneously.