A benchmark for multi-rate surface complexation and 1D dual-domain multi-component reactive transport of U(VI)

Research output: Contribution to journalArticle

Authors

Institutes & Expert groups

  • Carl-von-Ossietzky University of Oldenburg
  • NRC - Nuclear Regulatory Commission
  • UBC - The University of British Columbia

Documents & links

DOI

Abstract

Nonequilibrium surface complexation reactions have been found to substantially affect U(VI) transport in natural porous media both in laboratory and field scale experiments. Nonequilibrium sorption behavior occurs on multiple time scales and is a result of diffusion-limited transport in immobile intra-grain and intra-aggregate pore water. Experimental data on U(VI) transport was successfully described with a recently developed reactive transport model that accounted for the nonequilibrium adsorption processes through the formulation of a multi-rate surface complexation model treating surface complexation as kinetic reactions. In the present work, a benchmark problem set has been developed for testing existing or newly developed reactive transport codes on their capability to simulate multi-rate surface complexation and dual-domain multicomponent reactive transport of U(VI). The benchmark problem consists of three individual component problems on the basis of previous studies investigating the desorption of U(VI) from radionuclide-contaminated sediment from the Hanford 300A site, Washington, USA. Starting with a single-domain model considering constant hydrochemical conditions (component problem 1), the complexity of the model was stepwise increased. In the component problem 2 dual-domain first-order mass transfer was added. The principal problem also included dual-domain mass-transfer, but was further extended for changing hydrochemical conditions in the column’s inflow water, which resulted in drastic changes in the U(VI) desorption pattern due to surface complexation reactions. For the three individual component problems, the corresponding simulation results agree very well among four well-known and thoroughly tested independent reactive transport codes, indicating that the proposed benchmark problem set is a suitable test case.

Details

Original languageEnglish
Pages (from-to)585-597
JournalComputational Geosciences
Volume19
Issue number3
DOIs
StatePublished - 1 Jun 2015

Keywords

  • groundwater, uranium reactive transport, nonequilibrium mass-transfer, surface complexation

ID: 875031