Current practice in radiometric data analysis seems to have largely ignored using the Compton scattered gamma rays to characterise the very near surface, the soil horizon. The emphasis is upon the line spectra from radioisotope decay and removing or stripping out the scattered radiation from the parent and daughter product line source radiation for geochemical analysis. These radiation lines in the gamma spectrum are the gamma rays that do not interact with the other elements in the soil. Only the scattered radiation provides us with a means to characterise physical properties so the soil. Thus, if we want to infer soil density then we should analyse the scattered gamma radiation from the Compton spectrum as it is done with borehole density tools. With borehole tools a strong and calibrated-known gamma source is used to normalise the Compton gamma count. In the case of airborne radiometric we have robust procedures to calculate the in-situ source radiations strength already in place. Numerical modelling of gamma radiation with GEANT4 to examine the possibility of measuring soil density via radiometrics on an airborne platform indicates it is possible. However, leached soil horizons and very saturated mediums may reduce the density estimate accuracy substantially.

Open-Access Online Publication: May 31, 2023