Gamma ray attenuation for determining soil density: laboratory experiments for Environmental Physics and Engineering courses

Abstract

In this paper, we present in details a method for determining the soil density of disturbed samples. The mass attenuation coefficient was also evaluated by using the relation between the number of photon counts and the path length (soil density \texttimes thickness). A typical student laboratory setup (PASCO) was utilized in the measurements. A gamma ray source of ${}^{\text{137}}\text{Cs}$ and soils with four different textural classes were employed. The experimental apparatus here proposed, that uses an educational gamma ray attenuation system, permitted measuring, with very good agreement with the traditional method, the density of soil samples. The experiment can be somehow extended by proposing the investigation of soil bulk variations due, for instance, to soil compaction, a subject of interest for engineering and environmental physics students.

Keywords:
¹³⁷Cs gamma ray photons; Soil mass attenuation coefficient; XCOM; Soil chemical composition