Field characterization of vertical bromide transport in a fractured glacial till

William G. Harrar, Lawrence C. Murdoch, Bertel Nilsson, Knud Erik S. Klint

Research output: Contribution to journalArticleResearchpeer-review

29 Citations (Scopus)

Abstract

A study of the fracture distribution, hydraulic properties, groundwater levels and the transport of bromide was conducted to characterize vertical transport in the oxidized and reduced zones of a fractured glacial till. Detailed vertical profiles of groundwater levels and solute concentrations were obtained over a 4.5-year period. Vertical migration occurred at several time scales, as a low concentration front was rapidly transported at rates of 100-500 m/year ahead of a slower moving main plume, which advanced at rates of 0.2-0.8 m/year. Concentrations in the leading edge of the plume displayed a high degree of spatial variability over short vertical distances through day 1,000. Late in the test, the influence of matrix diffusion became apparent as concentration patterns developed from being irregular to more uniform distributions. Calculations show that the mass within the low concentration plume front accounts for less than 1% of the total solute mass. Simulation of the breakthrough curves using a simple one-dimensional advection-dispersion model of transport in porous media indicates that vertical transport is dominated by advection. Furthermore, the results indicate that vertical transport of solutes in oxidized and reduced zones of the till can be adequately simulated using an equivalent porous media.

Original languageEnglish
Pages (from-to)1473-1488
Number of pages16
JournalHydrogeology Journal
Volume15
Issue number8
DOIs
Publication statusPublished - Dec 2007

Keywords

  • Fractured confining unit
  • Glacial till
  • Mass flux
  • Tracer test
  • Travel times

Programme Area

  • Programme Area 2: Water Resources

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