Developing semianalytical solutions for multispecies transport coupled with a sequential first-order reaction network under variable flow velocities and dispersion coefficients

Abstract

This paper presents a semianalytical method to solve the multispecies reactive solute transport equation coupled with a sequential first-order reaction network under spatially or temporally varying flow velocities and dispersion coefficients. This method employs the generalized integral transform technique and general linear transformation method by Clement (2001) to transform the set of coupled multispecies reactive transport equations into a set of independent uncoupled equations and to solve these independent equations for spatially or temporally varying flow velocities and dispersion coefficients, as well as for a temporally varying inlet concentration. The proposed semianalytical solution is compared against previously published analytical solutions of Srinivasan and Clement (2008b) and van Genuchten (1985). An example is used to show application of the solution to a hypothetical multilayered medium. The solution of proposed approach is also compared with a numerical solution using the 2DFATMIC (Two-Dimensional Subsurface Flow, Fate and Transport of Microbes and Chemicals Model). Three scenarios are illustrated to show the capabilities of the proposed semianalytical method to deal with aquifer heterogeneity and transient situations. We also show a practical implementation of the solution to an actual field, single-well push-pull test example designed to obtain the concentration distribution of reactants consumed and products formed at the end of the injection phase. ©2013. American Geophysical Union. All Rights Reserved.