Experimental Support for a Simplified Approach to CTRW Transport Models and Exploration of Parameter Interpretation

We empirically test our earlier theoretical arguments about simplification of continuous-time random walk (CTRW) solute transport models, namely that without loss generality the velocity-like term, v?, may be set to mean groundwater velocity, dispersion-like D?, defined by a classical, velocity-independent dispersivity, and so-called time constant, ?, unity. also argue for small-scale heterogeneous advection (HA) mobile-immobile mass transfer (MIMT) CTRW transition distributions, ?(t), are unaffected flow velocity. To experimentally these claims, we re-analyze two bench-scale experiments—one HA, one MIMT—each performed at multiple rates in otherwise identical conditions, show it is possible simultaneously explain all breakthrough curves each, subject above constraints. compare calibrations with efforts same data sets. In HA calibration identify ?(t) functional form as previous authors, which yielded predictions essentially theirs, but greatly differing parameters. This illustrates how values individual parameters not map one-to-one onto underlying physics. recommend reporting complete model descriptions, discuss simplified approach assists this other considerations.