Influence of intensive agricultural activities in the hydrogeochemistry of a phreatic aquifer in a sector of the upper basin of Samborombón river (Buenos Aires Province, Argentina)

Abstract

The Samborombón river basin, located in the northeast of Buenos Aires province, is a rural area with extensive livestock farming as dominant activity but with intensive feedlots established and developing in recent years. Feedlots generate a large amount of excreta that represent point-source water pollution. In sectors where the water for consumption is supplied by exploitation of groundwater, these sources of pollution may reduce its potability. The goal of this work was to evaluate the influence of a feedlot in the hydrochemistry of the groundwater aquifer in the upper zone of the Samborombón river basin, and to analyze the social vulnerability and water-related risk in the area. For this purpose, water samples were taken to determine major ions, trace elements and phosphorus in the laboratory. Additionally, pH and electrical conductivity were measured in situ. The results indicate that intensive animal farming tends to deteriorate the quality of groundwater through incorporation of Cl-, SO42- and NO3-. Immobile or poorly soluble elements, such as phosphates, would tend to be retained in the soil and in the unsaturated zone, not affecting the chemical properties of the aquifer. On the other hand, levels of trace elements do not show changes with respect to the chemical baseline for the area. In some wells, the pollution of the aquifer caused by nitrates exceeds the limit suggested by the World Health Organization and affects the local inhabitants. Likewise, we detected socioeconomic vulnerability due to lack of access to basic services, such as potable water and an adequate sewer system.