A review on source identification of dissolved sulfate in groundwater: Advances, problems and development trends

Effective identification of the sources and biogeochemical processes of dissolved sulfate in groundwater is an important prerequisite for ensuring drinking water safety and aquatic ecological security and is of significance to manage and protect groundwater resources. In this review, the sources of groundwater sulfate and the typical range of δ34S and δ18O isotope from different sulfate sources are summarized by reviewing the literature; the identification of sulfate sources and S biogeochemical cycles by δ34S and δ18O isotope in sulfate is reviewed, and the existing problems and development trends are proposed. The source apportionment of groundwater sulfate sources has gone through the processes of hydrochemistry analysis→δ34S isotope→dual isotope→qualitative identification of multiple isotopes and tracers→quantitative evaluation. Due to the differences in sulfur and oxygen isotopes and the biogeochemical transformation processes in a specific region, there is still a larger uncertainty in the determination of groundwater sulfate sources.It is proposed to arrange the sampling points for collecting pollution sources and groundwater samples on the framework of groundwater flow systems and land use distributions and to analyze the hydrochemical components and the sulfur and oxygen isotope values of sulfate and other complementary tracer isotope values and/or concentrations in a specific area. The sources and their contributions of groundwater sulfate are analyzed using multidisciplinary and multi-methods based on the full integration of hydrogeochemistry, seepage field, land use and other information in a study area for the scientific implementation of groundwater resource protection and pollution prevention.