Evaluation of the origin of sulphate at the groundwater source Kljuc, Serbia

Abstract

The dual-isotope method of measuring both the 34S and 18O values of dissolved sulphate to assess the origin and fate of groundwater sulphate at the Klju groundwater source, Serbia is applied. A sampling campaign was conducted in September 2007 during low-flow conditions, obtaining river water and groundwater from observation wells completed in a shallow aquifer formed in alluvial sandygravelly sediments. In the shallow groundwater, sulphate concentrations ranged from 56.2 to 165.0mg l1. The 34S values of sulphate varied from5.5 to+3.0 parts per thousand and values from+1.4 to+4.2 parts per thousand. Oxidation of pedospheric (organic soil S) and lithogenic sulphur sources (e.g. pyrite) were identified as the main causes for the increasing sulphate concentrations in the analysed groundwater. This study shows that combining hydrological, chemical, and isotopic techniques is a powerful approach to identifying sources and processes that control sulphate in water resources.