Performance evaluation of equipment used for volumetric water content measurements

Various methods can be used to evaluate in situ volumetric water content; however, when continuous measurements are required, only dielectric methods can be used. For equipment based on these methods, in the mining environment and particularly in environments having high sulfide contents (or acid-generating minerals), the accuracy of measurements can be affected by the chemistry of the solid and liquid phases. To evaluate the real impact of water chemistry and mineralization on volumetric water content measurement, three instruments were tested on five materials with varying sulphur contents and two types of water mineralization. The results of these investigations show that: i) increasing sulfur content of mine tailings increases the response output of the tested probes; ii) the obtained volumetric water contents are systematically higher than the real volumetric water contents obtained gravimetrically; iii), time-domain reflectometry probes are able to provide measurements in materials with high sulphur contents; and iv) 5TM and GS3 probes are not suitable for use in reactive materials with higher sulphur contents.