Modeling bimolecular reactions and transport in porous media

We quantitatively account for the measured concentration profile from a laboratory experiment of bimolecular (A + B -> C) reactive transport in a porous medium with a particle tracking (PT) model. The PT results are in contrast to the analytical solution of the continuum scale advection-dispersion-reaction equation, which results in an excess quantity of reaction product (C). The approaches differ in the treatment of the mixing zone, the fluctuations due to the low reactant concentrations, and the localized nature of the reaction. The PT can accommodate a range of transport modes with different temporal distributions. An exponential temporal distribution is equivalent to Fickian transport, which we use for the comparison to the laboratory data; a truncated power-law (TPL) temporal distribution yields a non-Fickian transport characteristic of heterogeneous media. We study the influence of disorder on the mixing zone and the product concentration profiles via these contrasting transport modes. Citation: Edery, Y., H. Scher, and B. Berkowitz (2009), Modeling bimolecular reactions and transport in porous media, Geophys. Res. Lett., 36, L02407, doi: 10.1029/2008GL036381.