The Effects of WaterRetention Parameters on Air Entrapment below the Water Table

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The Effects of Water-Retention Parameters on Air
Entrapment below the Water Table

• Petia Tontcheva
• University of Illinois at Chicago
• EMSI REU Summer 2004
• Advisor Dr. Stephen Silliman

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Objectives

• Previous investigations on air and water
  entrapment in the vicinity of the water table
• Research Hypotheses
• Materials and Methods
• Results
• Observations/Conclusions
• Acknowledgments

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Previous Investigations

• The water table
• The region near the water table
• - highly complex
• - a potential region for biological and
  chemical remediation of contaminants

http//groundwater.orst.edu/under/aquifer.htm
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Previous Investigations

• Silliman et al. (2002) first described the
  phenomena of air-entry barriers (AEBs) above the
  water table
• Dunn and Silliman (2003) extended the concept of
  AEBs to include
• the region below the water table
• The significance of AEBs
• - potential for chemical exchange between
  liquid and gas phases
• - affinity of some bacteria for air/water
  interface (Wan and Wilson, 1994)
• Numerical models have been shown to agree with
  the experimental results

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Research Hypotheses

• My research focused on the effects of
  water-retention parameters on AEB below the water
  table
• Water-retention parameters are estimated from
  water-retention curves
• Water-retention curves show the relationship
  between the quantity of water at any given point
  in the soil profile and its equivalent energy
  potential
• - used to characterize soil hydraulic behavior
• van Genuchten equation (van Genuchten, 1980) - a
  widely used equation to predict the
  experimentally determined water-retention data

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Research Hypotheses
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Research Hypotheses
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Research Hypotheses

• 1. An increase in Po of coarse sand lenses
  surrounded by finer sand in the presence of a
  rising water table will result in sands with
  properties similar to the finer sand and will
  have less significant effects on the AEB.
• 2. An increase in ? of coarse sand lenses
  surrounded by finer sand in the presence of a
  rising water table will result in less
  non-uniform sands and will have more significant
  effects on the AEB.

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Materials and Methods

• TOUGH 2 a numerical stimulator for
  multi-dimensional fluid and heat flows of
  multiphase, multicomponent fluid mixtures in
  porous and fractured media
• - applications in nuclear waste
  disposal, environmental assessment and
  remediation, saturated zone hydrology, geothermal
  reservoir engineering
• Created a laboratory tank with two coarse sand
  lenses surrounded by finer sand and simulated a
  rising water table

150 cm
192 cm
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Materials and Methods

• To test HP1 ?0.864 Po1445
• Po
  649
• Po
  400
• To test HP2 Po649 ? 0.7
• 
  ? 0.5
• 
  ? 0.3

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Results for ?
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Results for Po
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Observations/Conclusions

• The results agree with the hypotheses.
• An increase in Po of the coarse sand in the
  presence of a rising water table will result in a
  sand with properties similar to the surrounding
  fine sand and in the entrapment of less air.
• An increase in ? of the coarse sand will result
  in a more uniform sand and the entrapment of more
  air.
• Valuable information in the field to predict
  which field sites are opportune targets for
  chemical and biological remediation of
  contaminants

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Acknowledgments

• Dr. Stephen Silliman
• Andrea Dunn
• Everyone else who has contributed to my research
  experience

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Questions?