Variability of 222 Rn in the sandy aquifer of Buenos Aires coast

摘要

Rn-222 is widely used as a tracer to detect and calculate submarine groundwater discharge in coastal zones, rivers and lakes. Relatively few investigations, however, have used this element for other applications in hydrogeology. We analyze the relationship between Rn-222 activity in groundwater and variations in the water cycle in the sandy aquifer of Buenos Aires coast, Argentina. Groundwater levels, electrical conductivity and Rn-222 activity were measured in situ in wells in March 2016 and November 2018, representing two different hydrological conditions. Groundwater flow maps were drawn, hydrological gradients and flux velocities were calculated. An inverse correlation between Rn-222 activity and recharge conditions was found. Lower water surplus shows higher Rn-222 activity and vice versa, potentially due to dilution of high Rn-222 activity water with 'newer' lower activity recent recharge. A variability in Rn-222 spatial distribution was identified along the sand dune barrier. A correlation between Rn-222 and groundwater electrical conductivity was not observed.