Applying Digital Image Processing to SEM-EDX and BSE Images to Determine and Quantify Porosity and Salts with Depth in Porous Media

Digital image processing is applied to X-ray element maps and back-scattered electron (BSE) images obtained with scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDX), to quantify and identify salts and porosity with depth in porous media. Until now, only salt chemical composition with depth has been characterised and salt mineral composition inferred, so that no salt quantification was possible. The method we present can be used stand-alone or integrated with other techniques to fill certain gaps in our knowledge. It can be used to quantify texture and porosity of clay minerals, with implications in petroleum research. Also, salts may be identified and quantified with depth in porous media; this is important when selecting among salt extraction procedures in order to conserve cultural heritage. Finally, the method can help in interpreting salt weathering processes and links between stone decay forms at different scales, with consequences for geomorphology.