Assessment of a UV Excited Fluorescent Dye Technique for Estimating Solute Dispersion in Porous Media

Abstract

Dyes are important tracers to investigate subsurface water movement and solute transport processes. Laboratory tracer experiments with a fluorescent dye, Brilliant Sulfaflavine, are carried out in a two-dimensional water flow tank uniformly packed with glass beads over a wide range of steady state water flow rates. Under ultraviolet (UV) illumination conditions the fluorescent dye emits visible light and is imaged by a digital camera. An imaging processing technique based on UV excited spatial distributions of the fluorescent dye tracer allows to link with a spatial moment approach to identify the longitudinal and transverse microdispersivities. The experimental results show that the mean values of longitudinal and transverse microdispersivities range from 0.095 cm to 0.40 cm and from 0.027 cm to 0.061 cm, respectively. Laboratory study is extended by a random walk particle tracking approach to reconstruct the estimated microdispersivity transitions, demonstrating a good agreement between the experimental and numerical results in homogeneous porous formations of concern. The methodology applied herein represents a potentially valuable tool in the assessment of microdispersion phenomena in porous media.