Oxygen Transfer in a Fluctuating Capillary Fringe

Christina M. Haberer, Massimo Rolle, Olaf A. Cirpka, Peter Grathwohl

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Dynamic fluctuations in water table elevation cause the entrapment of air, which affects the hydraulic properties of the porous medium in the capillary fringe as well as the biogeochemical status of the underlying, potentially O-2-depleted groundwater. In this study, we conducted quasi two-dimensional flow-through experiments at the laboratory bench scale to investigate in detail the mass transfer of O-2 in a fluctuating capillary fringe. We evaluated the effects of different boundary conditions such as single drainage and imbibition events as well as periodic fast and slow water table fluctuations. High-resolution vertical profiles of O-2 concentration, measured at two distances in the horizontal groundwater flow direction, and mass fluxes, determined in the effluent of the flow-through chamber, were used to quantify O-2 transfer under the different boundary conditions applied. The results show that the partitioning between the aqueous and the gaseous phases plays a significant role in the supply of O-2 to groundwater at mediumtime scales. In the case of fast water table fluctuations, the specific yield has to be considered. The experiments with a periodically changing boundary condition demonstrate that highly dynamic fluctuations of the water table enhance the mass transfer of O-2 from the atmosphere into the groundwater when compared with steady-state conditions. Moreover, the characteristics of the water table fluctuations determine a specific dynamic response of the system: we observed an approximately double amount of O-2 transferred to the groundwater when applying slow fluctuations compared with the case of cyclic, abrupt changes in the water table elevation.
Original languageEnglish
JournalVadose Zone Journal
Volume11
Issue number3
ISSN1539-1663
DOIs
Publication statusPublished - 2012
Externally publishedYes

Keywords

  • Soil Science
  • Capillary fringe
  • Different boundary condition
  • Flowthrough
  • Gaseous phasis
  • Groundwater flow directions
  • High resolution
  • Hydraulic properties
  • Oxygen transfer
  • Porous medium
  • Specific yield
  • Steady-state condition
  • Time-scales
  • Vertical profile
  • Water table elevation
  • Water table fluctuations
  • Water tables
  • Boundary conditions
  • Dynamic response
  • Effluents
  • Experiments
  • Groundwater flow
  • Mass transfer
  • Porous materials
  • Groundwater
  • boundary condition
  • capillarity
  • concentration (composition)
  • effluent
  • groundwater flow
  • hydraulic property
  • mass transfer
  • oxygen
  • steady-state equilibrium
  • timescale
  • two-dimensional modeling
  • water table
  • ENVIRONMENTAL
  • SOIL
  • WATER
  • TRAPPED GAS-PHASE
  • VOLATILE ORGANIC-COMPOUNDS
  • WATER-TABLE FLUCTUATION
  • SATURATED POROUS-MEDIA
  • SOLUTE TRANSPORT
  • KINETIC-MODEL
  • GROUNDWATER
  • FLOW
  • SAND
  • DISPERSION

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