A high-resolution non-invasive approach to quantify oxygen transport across the capillary fringe and within the underlying groundwater

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

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Oxygen transport across the capillary fringe is relevant for many biogeochemical processes. We present a non-invasive technique, based on optode technology, to measure high-resolution concentration profiles of oxygen across the unsaturated/saturated interface. By conducting a series of quasi two-dimensional flow-through laboratory experiments, we show that vertical hydrodynamic dispersion in the water-saturated part of the capillary fringe is the process limiting the mass transfer of oxygen. A number of experimental conditions were tested in order to investigate the influence of grain size and horizontal flow velocity on transverse vertical dispersion in the capillary fringe. In the same setup, analogous experiments were simultaneously carried out in the fully water-saturated zone, therefore allowing a direct comparison with oxygen transfer across the capillary fringe. The outcomes of the experiments under various conditions show that oxygen transport in the two zones of interest (i.e., the unsaturated/saturated interface and the saturated zone) is characterized by very similar transverse dispersion coefficients. An influence of the capillary fringe morphology on oxygen transport has not been observed. These results may be explained by the narrow grain size distribution used in the experiments, leading to a steep decline in water saturation at the unsaturated/saturated interface and to the absence of trapped gas in this transition zone. We also modeled flow (applying the van Genuchten and the Brooks-Corey relationships) and two-dimensional transport across the capillary fringe, obtaining simulated profiles of equivalent aqueous oxygen concentration that were in good agreement with the observations. (C) 2010 Elsevier B.V. All rights reserved.
Original languageEnglish
JournalJournal of Contaminant Hydrology
Volume122
Issue number1-4
Pages (from-to)26-39
Number of pages14
ISSN0169-7722
DOIs
Publication statusPublished - 2011
Externally publishedYes

Keywords

  • Water Science and Technology
  • Environmental Chemistry
  • 2-D experiments
  • Capillary fringe
  • Fiber-optical sensor technique
  • Hydrodynamic dispersion
  • Oxygen transport
  • Experiments
  • Fluid dynamics
  • Grain size and shape
  • Groundwater
  • Hydrodynamics
  • Optical sensors
  • Oxygen
  • Phase interfaces
  • Two dimensional
  • Dispersions
  • ground water
  • biogeochemistry
  • capillary fringe
  • concentration (composition)
  • experimental study
  • flow velocity
  • grain size
  • laboratory method
  • mass transfer
  • oxygen
  • phreatic zone
  • quantitative analysis
  • transport process
  • two-dimensional flow
  • article
  • controlled study
  • dispersion
  • flow rate
  • hydrodynamics
  • mathematical model
  • non invasive measurement
  • optical biosensor
  • oxidation reduction reaction
  • oxygen concentration
  • oxygen saturation
  • oxygen transport
  • particle size
  • photochemical quenching
  • porosity
  • priority journal
  • quasi experimental study
  • surface property
  • Environmental Monitoring
  • Models, Theoretical
  • Porosity
  • Soil
  • Water Movements
  • Water Supply
  • ENVIRONMENTAL
  • GEOSCIENCES,
  • WATER
  • UNSATURATED POROUS-MEDIA
  • TRAPPED GAS-PHASE
  • TRANSVERSE DISPERSION
  • SOLUTE TRANSPORT
  • MASS-TRANSFER
  • HYDRODYNAMIC DISPERSION
  • MISCIBLE DISPLACEMENT
  • WATER SATURATION
  • DISSOLVED-OXYGEN
  • SANDY SOIL
  • groundwater sample
  • high-resolution non-invasive approach
  • oxygen transport quantification
  • water saturation
  • 04500, Mathematical biology and statistical methods
  • 07502, Ecology: environmental biology - General and methods
  • 10515, Biophysics - Biocybernetics
  • Computational Biology
  • Ecology, Environmental Sciences
  • Genuchten/Brooks-Corey relationship-based modeling mathematical and computer techniques
  • quasi two-dimensional flow-through laboratory experiment laboratory techniques
  • Groundwater Ecology
  • Models and Simulations
  • S88TT14065 Oxygen

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