Contaminant migration in unsaturated porous media using X-ray computerized tomography (CT)

Abstract

Landfills are usually located in unsaturated zones. Contaminant leaking can easily infiltrate groundwater through these porous media and contribute to groundwater pollution. The main objective of this work is to study the leachate migration in unsaturated porous media using X-ray computerized tomography (CT) and image-processing software. Silica sand and Yamazuna sand (collected from Japan) with different particle sizes are considered. Potassium iodide (KI) solution is used as a contaminant and injected into sand specimens at appropriate rates. The specimens are scanned at each cross section before and after contaminant injection by X-ray CT. Subsequently, all CT images are transformed into mean CT values by Image J software. VGStudio software is then used to reconstruct the subtracted images into three-dimensional images. The results indicate that vertical migration is dominant in uniform sand and horizontal migration is the main behavior in well-graded sand. Meanwhile, it is also confirmed that CT scanning is an effective technology to study contaminant migration in unsaturated porous media with different grain sizes.