Correlating Gas Phase Correlating Gas Phase Dispersion In Unsaturated Dispersion In Unsaturated
SoilsSoils
Darryl Cann, Darryl Cann, M.ScM.Sc. Eng Candidate. Eng CandidateWarren H. Warren H. StiverStiver, Ph.D., , Ph.D., P.EngP.Eng., Professor., ProfessorRichard G. ZytnerRichard G. Zytner, Ph.D., Ph.D., P.EngP.Eng., Professor., Professor
University Of University Of GuelphGuelph, School of Engineering, School of Engineering
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OutlineOutline
ØØ IntroductionIntroductionØØ Research GoalsResearch GoalsØØ Experimental ApproachExperimental ApproachØØ ResultsResultsØØ Future WorkFuture Work
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IntroductionIntroduction
ØØ 10% of 10% of USTsUSTs in USA and Canada are in USA and Canada are currently leakingcurrently leaking
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Introduction Introduction –– cont.cont.
ØØ Superfund Remedial Actions (EPA, Superfund Remedial Actions (EPA, 2004): 2004):
•• 35.3% SVE35.3% SVE•• 17.6% Bioremediation/Bioventing17.6% Bioremediation/Bioventing
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Bioventing and SVE ModelingBioventing and SVE Modeling
ØØ AdvectionAdvection--dispersion equationdispersion equation
ØØ Longitudinal Dispersion CoefficientLongitudinal Dispersion Coefficient
DiffL DD += αν
iL rxc
xc
Dtc
∑±∂∂
−∂∂
=∂∂
ν2
2
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SVE and BioventingSVE and Bioventing
ØØ Rule of Thumb DesignRule of Thumb Design
ØØ ModelsModels•• Performance estimatesPerformance estimates•• Lack of reliable coefficientsLack of reliable coefficients
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DispersionDispersion
ØØ Gradual spreading and mixing of Gradual spreading and mixing of solute with advective flowsolute with advective flow
•• Velocity GradientsVelocity Gradients•• Concentration GradientsConcentration Gradients
to t2t1to
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Dispersion MechanismsDispersion Mechanisms
ØØ Path TortuosityPath Tortuosity
ØØ Friction in Pore Friction in Pore
ØØ Pore SizePore Size
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Dispersion MechanismsDispersion Mechanisms
ØØ Path TortuosityPath Tortuosity
ØØ Friction in Pore Friction in Pore
ØØ Pore SizePore Size
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Research Goals Research Goals -- OverallOverall
Soils Research GroupSoils Research Group
MTC DispersionBiological
Degradation
SVE and BV Models
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Research Goals Research Goals -- DispersionDispersion
ØØ Phase IPhase I•• Develop experimental apparatusDevelop experimental apparatus•• Develop correlationsDevelop correlations•• Disturbed soilsDisturbed soils
ØØ Phase IIPhase II•• Test correlations on field core samplesTest correlations on field core samples•• Modify correlations for field predictionsModify correlations for field predictions
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MethodologyMethodology
ØØ 11--D NonD Non--Reactive Tracer experimentsReactive Tracer experiments
ØØ Open Vessel Boundary ConditionsOpen Vessel Boundary Conditions
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Methodology Methodology –– cont.cont.
ØØ Soil and ColumnsSoil and Columns
ØØ Water Content Water Content •• Air Dry (~5%) to Field CapacityAir Dry (~5%) to Field Capacity
Soil Properties OS SLS ESL BC
% Sand (by weight) 98.8 69.4 34.0 21.0% Silt (by weight) 1.2 24.4 50.1 35.1% Clay (by weight) 0 6.2 15.9 43.9• OS – Ottawa Sand
• SLS – Simcoe Loamy Sand
• ESL – Elora Silt Loam
• BC – Brookston Clay
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Methodology Methodology –– cont.cont.
ØØ Tracer InjectionTracer Injection•• Solenoid ValveSolenoid Valve•• Tracer Tracer -- HeliumHelium•• Carrier Carrier -- Nitrogen Nitrogen
ØØ Two sampling Two sampling locationslocations
Sampling Probe Configuration
Soil Column
Probe
To TCD
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Methodology Methodology –– cont.cont.
ØØ Thermal Conductivity Detector (TCD)Thermal Conductivity Detector (TCD)
ØØ RealReal--Time Data CollectionTime Data Collection•• NI DAC NI DAC •• LabVIEWLabVIEW
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Experiment SchematicExperiment Schematic
He N2
Main Flow
Control
Mass Flow Meter
Solenoid Valve
Soil Column
Data Collection
TCD
ExhaustFlow
Meters
Exhaust
Water Bath
Heat Exchanger/Humidifier
Vacuum pump
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Heat Exchanger/ Humidifier
Soil Column
Flow MeterTCD
Vacuum Pumps
Solenoid Valve
Probes
Flow Valve
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Data Analysis Data Analysis
ØØ Residence Time DistributionResidence Time Distribution•• Variance, Mean residence time, DispersionVariance, Mean residence time, Dispersion
-0.05
0.00
0.05
0.10
0.15
0.20
0.25
0 10 20 30 40
Time (s)
TC
D r
esponse
(mV
) Channel 1Channel 2
s 21
s 22
t1 t2
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ResultsResults
ØØ New, working apparatusNew, working apparatus•• Disturbed Disturbed •• UndisturbedUndisturbed
-0.05
0.00
0.05
0.10
0.15
0.20
0.25
0 10 20 30 40
Time (s)
TC
D re
sponse
(mV) Channel 1
Channel 2
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Results Results –– contcont’’dd
ØØ Preliminary Air Dry Ottawa SandPreliminary Air Dry Ottawa Sand•• Dispersivity (Dispersivity (aa ) = 0.042 cm ) = 0.042 cm
ØØ GiddaGidda et al. (2004)et al. (2004)Soil Type Moisture Content Observed Dispersivity (cm)
Ottawa Sand Air Dry 0.63% 1.2
Delhi Loamy Sand Air Dry 1.220% 2.6
Elora Silt Loam Air Dry 1.620% 1.130% 1.9
Brooksten Clay Air Dry 1.340% 2.4
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DiscussionDiscussion
ØØ Reliable dispersivity valuesReliable dispersivity valuesØØ SVE and BVSVE and BV
•• Improved closure predictionsImproved closure predictions
•• Improved system designsImproved system designs
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Future WorkFuture Work
ØØ Disturbed soil are ongoing Disturbed soil are ongoing
ØØ Collect field core samplesCollect field core samples
ØØ Compare results with correlations Compare results with correlations
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AcknowledgementsAcknowledgements
ØØ NSERC Strategic NSERC Strategic Grant Grant
ØØ Dr. Dr. TejwantTejwant GiddaGiddaØØ Jon BrookerJon BrookerØØ EyadEyad BarakatBarakat
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Thank YouThank You
Questions / Comments ?Questions / Comments ?
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