Single photon emission computed tomography (SPECT) is an imaging technique widely used in medical diagnosis.  This technique has never been applied to soils.  The objective of this study was to investigate the capabilities of SPECT scanning for visualizing preferential flow in soil.  This paper describes the principle of SPECT scanning and its application to tracer breakthroughs in four large undisturbed soil columns (800 mm x 77 mm diameter).  This new approach allows real-time analysis of flow patterns of radioactive tracers in 2-D, using planar imaging, and in 3-D, with the tomographic capabilities of the SPECT scanner. 

 Not only does SPECT scanning provide qualitative data, but it also allows for quantification of the tracer’s spatial distribution.  Our results characterized preferential flow very clearly in soil columns.  SPECT scanning opens new avenues for 2-D and 3-D tracer studies in porous media such as soil.  (Click here for more info)