LAUSR

Chemistry of surface water and groundwater can be conditioned by geology, anthropic influence, and exchange of flow between them. The Pampean Plain located in Argentina has gaining streams and mainly rural activities. An increase in the concentration of chemical values of surface waters with respect to groundwater can be attributed to the anthropogenic contribution. The aim of this work was to identify the natural and/or anthropic processes that determine the chemistry of surface water and groundwater in a sector of the Pampean Plain of Argentina through the analysis of major and trace elements, 18O and 2H isotopes, and statistical tools. A surface water and groundwater sampling network was designed, where physicochemical parameters were measured, and samples were taken to determine major and trace elements and stable isotopes of water. The results indicate that dissolution, cation exchange, and evaporation are the main processes that determine the chemistry of the major elements associated with natural processes without showing evidence of anthropic involvement. Some trace elements that are statistically associated with major ions evidence water‐sediment interaction within the aquifer. On the other hand, trace elements, as heavy metals, present a higher concentration in surface water compared to groundwater. This fact, evidences an anthropogenic contribution attributable to anthropic activities. The multivariate statistical analysis allowed discriminating between those trace elements associated with natural processes from those influenced by anthropic activity, even when these elements' concentration was very low.