CONICET | Buscador de Institutos y Recursos Humanos

The activity of ²²²Rn of the groundwater was measured in different wells in the Pampeano aquifer in southeastern Buenos Aires to assess how the hydrogeological characteristics of the study area, which involves type and depth of the bedrock, aquifer mineralogy and residence time along flowpaths, influences on ²²²Rn contents. Water samples, as well as sediment samples, were collected in multilevel piezometers in different sites of the Buenos Aires province for the determination of stable isotopes, ²²²Rn concentrations and mineralogical analyses. The identification of uranium-bearing minerals in the loess sediments of the Pampeano aquifer was carried out with a scanning electron microscope allowing identifying zircon and monazite. The ²²²Rn was determined with a RAD7 detector, showing a range of activities from 3.1 to 14.9 Bq/L. The results showed a relation between the ²²²Rn activity, the depth of the wells, and the proximity of the Precambrian basement. The activity of ²²²Rn increases linearly with increasing depth at a rate of 0.09 Bq·L⁻¹·m⁻¹. However, at the same depth the concentration of ²²²Rn in wells near the Precambrian basement showed to be three times higher than the concentrations in the wells that have a Paleozoic bedrock, clearly showing that the proximity of granitoids rocks results in higher concentrations of radon.