SCALE-DEPENDENT DISPERSION OF SOLUTE TRANSPORT IN MULTI-SCALE EXPERIMENTS

Dispersion is one of the most important solute transport processes in porous and fractured media. Due to its scale dependency, dispersion adversely affects simulations of solute transport. Therefore, there has been much attention to better represent dispersion in contaminant transport studies in subsurface systems. This paper presents some of our recent work on estimating scale-dependent dispersivity using multi-scale laboratory experiments. We performed a series of column and tank experiments with length-scale from centimeter to meter. Different types of sediments with different grain sizes were randomly filled into the columns and tanks for tracer tests. The experimental results and tested analytical and numerical models were compared and discussed. We also present our results on how different grain sizes control on the scale-dependent dispersivity as well as the impact of degree of local-scale heterogeneity on dispersion processes. The results from these experiments provide substantial insights on dispersivity selections of solute transport in different scale models.