Reactive dispersive contaminant transport in coastal aquifers: Numerical simulation of a reactive Henry problem

H. M. Nick, A. Raoof, F. Centler, M. Thullner, P. Regnier

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

The reactive mixing between seawater and terrestrial water in coastal aquifers influences the water quality of submarine groundwater discharge. While these waters come into contact at the seawater groundwater interface by density driven flow, their chemical components dilute and react through dispersion. A larger interface and wider mixing zone may provide favorable conditions for the natural attenuation of contaminant plumes. It has been claimed that the extent of this mixing is controlled by both, porous media properties and flow conditions. In this study, the interplay between dispersion and reactive processes in coastal aquifers is investigated by means of numerical experiments. Particularly, the impact of dispersion coefficients, the velocity field induced by density driven flow and chemical component reactivities on reactive transport in such aquifers is studied. To do this, a hybrid finite-element finite-volume method and a reactive simulator are coupled, and model accuracy and applicability are assessed. A simple redox reaction is considered to describe the degradation of a contaminant which requires mixing of the contaminated groundwater and the seawater containing the terminal electron acceptor. The resulting degradation is observed for different scenarios considering different magnitudes of dispersion and chemical reactivity. Three reactive transport regimes are found: reaction controlled, reaction-dispersion controlled and dispersion controlled. Computational results suggest that the chemical components' reactivity as well as dispersion coefficients play a significant role on controlling reactive mixing zones and extent of contaminant removal in coastal aquifers. Further, our results confirm that the dilution index is a better alternative to the second central spatial moment of a plume to describe the mixing of reactive solutes in coastal aquifers. (C) 2012 Elsevier B.V. All rights reserved.
Original languageEnglish
JournalJournal of Contaminant Hydrology
Volume145
Pages (from-to)90-104
Number of pages15
ISSN0169-7722
DOIs
Publication statusPublished - 2013
Externally publishedYes

Keywords

  • Density driven flow
  • Reactive transport
  • Dispersion
  • Submarine groundwater discharge
  • Node-centered finite-volume–finite-element method
  • Dilution index

Fingerprint Dive into the research topics of 'Reactive dispersive contaminant transport in coastal aquifers: Numerical simulation of a reactive Henry problem'. Together they form a unique fingerprint.

Cite this