Application of INAA in the characterisation and quantification of Dy-labeled ceramic spheres and their use as inert tracers in soil studies

An inert, activable tracer method, using sized ceramic spheres custom labeled with similar to 15% Dy2O3 during manufacture, has been developed to study soil aggregation. Instrumental neutron activation analysis (INAA) with a Slowpoke reactor, using Dy-165m (T-1/2 = 1.26 min), provides an extremely rapid means with which to characterise the Dy-content of the various size fractions of labeled spheres from different production runs. In contrast, the Dy-content land hence number of spheres) of 5-8 g soil/sphere mixtures is determined using the longer-lived Dy-165 (T-1/2 = 2.33 hrs) following a similar to 30-minute decay period during which the otherwise interfering Al-28 (T-1/2 = 2.24 min) preferentially decays. The method is expected to find many applications.