A survey of applications of non-radioactive but neutron activatable groundwater tracers

For the last 20 years the authors and their students have been conducting research in the use of non-radioactive but environmentally acceptable tracers which can be detected by means of neutron activation analysis. Potential tracers evaluated include the halogen ions (bromide, chloride, and iodide); certain other inorganic ions frequently found in the soil; and chelated rare earths. These tracers have undergone laboratory tests using soil column and slurry tests, and the most promising ones have been field tested. Where possible, the resulting breakthrough curves have been compared with those produced by a tritiated water tracer used under the same test conditions. The authors have used this technique in solving a variety of different types of water movement problems, including determining the interconnection between sink holes and springs and between surface water and groundwater sources; determining the amount of recirculation of water pumped from wells and mines; and identifying sources of water pollution such as acid mine drainage. The technique has also been used to measure hydrogeological parameters of soil systems, using it in one- and two-well pump tests. It was also the basis for the recent development of techniques for parameter determination by modelling and mathematical unfolding of breakthrough curves. For those countries which have their own research reactor(s), this technique could be a valuable tool for conducting hydrology studies in remote or populated areas. (author). 17 refs, 4 figs