Impact of Physical Heterogeneity and Transport Conditions on Effective Reaction Rates in Dissolution

Abstract A continuous-time random walk (CTRW) reactive transport model is used to study the impact of physical heterogeneity on effective reaction rates in porous media a sample length 15 cm over timescales up 10 $$^8$$ 8 s (3 years). The has previously been validated using nuclear magnetic resonance (NMR) measurements during dissolution limestone. assumes first-order reaction. We construct three domains with increasing and at four Péclet numbers, Pe = 0.0542, 0.542, 5.42 54.2. characterize signatures velocity distributions show how these imprint particle displacement, namely propagator distributions. In addition, we demonstrate ability our CTRW capture longitudinal dispersion coefficient several orders magnitude space time. Reactive simulations that depend (i) initial (ii) conditions. For all heterogeneities , late-time rate exhibits time dependence $$t^{-a}$$ t - a $$a \ne 0.5$$ ? 0.5 indicates persistence incomplete mixing. higher heterogeneity, lower rate. decrease promotes mixing by diffusion advection, resulting rates. post-dissolution propagators indicate an increase degree non-Fickian transport. Overall, establish framework quantify media.