Investigation of Groundwater Flow in a Deep Aquifer by the Activable Tracer Method

In order to select most suitable activable tracers for investigation of groundwater flow (70°C) in an aquifer, loss of indium and dysprosium compounds (nitrate and chelate) by adsorption on rock, sampled from an underground aquifer at a depth of about 1000 m, was first examined by both batch and column methods. Next, the groundwater flow in an aquifer was investigated by injecting 1 kg of Dy-chelating complex salt (Dy-DTPA) and In-DTPA as activable tracers into a reducing well at a distance of 112 m from a producing well. Dy-DTPA and In-DTPA of 0.9μg/l and 0.4μg/l at maximum concentrations, respectively, were detected in the groundwater when 11000m3 and 21000m3 waters were pumped up from the producing well. Dy-DTPA has proved to be a useful tracer for the investigation because of relatively small loss whereas a considerable fraction of In-DTPA appears to be lost by adsorption or chemical decomposition.