Particle Density of Volcanic Soils as Measured with a Gas Pycnometer

Abstract

AbstractIn the absence of actual data, the particle density of soil is often assumed to be 2.65 Mg/m3. In this study, we will discuss whether this hypothesis applies with reasonable accuracy to various types of soils from Martinique. Thirty‐nine samples taken from seven different subgroups of soils derived from volcanic materials were considered: Andeptic Troporthent, Typic Hydrandept, Typic Dystrandept, Andic Humitropept, Typic and Oxic Dystropept, and Entic Pellustert. Particle density was measured in triplicate on undisturbed, oven‐dried samples by means of a gas pycnometer. The measurements were performed using air and He. Values found in He pycnometry ranged from 2.38 to 2.72 Mg/m3. The organic‐matter content was a major factor in explaining low particle densities, but other soil constituents may be significantly involved also. Reproductibility of He pycnometry was found to be good. Air‐pycnometry measurements revealed strongly distorted values for many soil materials when compared with He‐pycnometry results. This was assigned to a gas adsorption phenomenon and found to be linearly related to the surface area of the soil samples as measured by ethylene glycol monoethyl ether.