LECTURE 13
MONITORED NATURAL
ATTENUATION
Monitored Natural Attenuation
As defined by U.S. EPA:
reliance on natural processes to achieve
site-specific remedial objectives
Source: Pope, D. F., and J. N. Jones, 1999. Monitored Natural Attenuation of Chlorinated Solvents. U.S. EPA Remedial Technology Fact Sheet.
Report Number EPA/600/F-98/022. Office of Research and Development, U.S. Environmental Protection Agency, Washington, D.C. May 1999.
(http://www.epa.gov/ada/download/fact/chl-solv.pdf).
Biodegradation
Sorption
Processes of
NATURAL
ATTENUATION
of Petroleum
Hydrocarbons
Dispersion
and Dilution
Volatilization
(Evaporation)
Chemical Reactions
Historical development of MNA
Historical development
• 1985 – Always a remedial alternative: EPA says it was used in Superfund as early as 1985
• 1988 – Guidance on Remedial Actions for Contaminated Ground Water at Superfund Sites discusses
natural attenuation, but mostly as a comparison standard for active remediation. Natural attenuation
is not encouraged
• Began to be more commonplace with recognition of intractability of DNAPL cleanups and inadequacy
of pump and treat technology
• Simultaneously, there was increasing recognition that in situ processes were containing or cleaning
up contamination
• 1993-94 – Two key studies by National Research Council:
• In Situ Bioremediation – When does it work? – 1993
study discusses intrinsic bioremediation
• Alternatives for Ground Water Cleanup – 1994
• 1995 – Technical Protocol for Implementing Intrinsic Remediation with Long-Term Monitoring for
Natural Attenuation of Fuel Contamination Dissolved in Groundwater
• Prepared by Air Force Center for Environmental Excellence working with U.S. EPA research
laboratory
• Defines procedure to show intrinsic remediation is occurring
• September 1996 – EPA Symposium on Natural Attenuation of Chlorinated Organics in Ground Water
• November 1996 – Draft Technical Protocol for Evaluating Natural Attenuation of Chlorinated Solvents
in Groundwater (Final in Sept. 1998)
• December 1997 – OSWER Policy Directive: Use of Monitored Natural Attenuation at Superfund,
RCRA Corrective Action, and Underground Storage Tank Sites
• Sept.-Dec. 1998 – EPA Seminars on Monitored Natural Attenuation in nine cities around the US
1988 Guidance on Ground Water
1993 and 1994 – NRC Studies
"In Situ Bioremediation. When does it work?"
National Research Council.
"Alternatives for Ground Water Cleanup." National
Research Council.
1995 – AFCEE
Technical
Protocol
Technical Protocol for Implementing Intrinsic
Remediation with Long-Term Monitoring for Natural Attenuation
of Fuel Contamination Dissolved in Groundwater
Volume 1
By
Todd Wiedemeier
Parsons Engineering Science, Inc.
Denver, Colorado
John T. Wilson and Donald H. Kampbell
U.S. Environmental Protection Agency
Robert S. Kerr Laboratory
Ada, Oklahoma
Ross N. Miller and Jerry E. Hansen
Air Force Center for Environmental Excellence
Technology Transfer Division
Brooks AFB, San Antonio, Texas
Air Force Center for Environmental Excellence
Technology Transfer Division
Brooks AFB, San Antonio, Texas
1996 – EPA
Symposium on
Natural
Attenuation
1996 – Draft Technical Protocol
Nov. 1996 – Draft
Sept. 1998 - Final
1997 – MNA
Policy
Directive
1998 – MNA
Seminars
Definition of MNA (continued)
May be physical, chemical or biological
Act without human intervention to reduce the mass,
toxicity, mobility, volume, or concentration of
contaminants in soil or ground water
Processes include:
biodegradation
dispersion
dilution
sorption
volatilization
chemical or biological stabilization, transformation, or
destruction
Source: Pope, D. F., and J. N. Jones, 1999. Monitored Natural Attenuation of Chlorinated Solvents. U.S. EPA Remedial Technology Fact Sheet.
Report Number EPA/600/F-98/022. Office of Research and Development, U.S. Environmental Protection Agency, Washington, D.C. May 1999.
(http://www.epa.gov/ada/download/fact/chl-solv.pdf).
Elements of Natural Attenuation
MNA is not:
No-action alternative
Presumptive or default remedy
MNA must be:
Evaluated along with other alternatives
Selected only is it meets remediation objectives
Work in reasonable time frame (30 years)
Used very cautiously as sole remedy
Components of MNA
Required components of MNA:
Source control
Performance monitoring
Prerequisite for MNA:
Site-specific characterization data and
analysis
Demonstrating efficacy of MNA
1. Historical chemical data showing clear trend
of decreasing mass or concentration.
2. Hydrogeologic or geochemical data that
indirectly demonstrate natural attenuation
processes
3. Field or microcosm studies that directly
demonstrate natural attenuation processes
Aerobic biodegradation of fuel
hydrocarbons
Oxygen used as electron acceptor
2C6H6 + 15O2 → 12CO2 + 6H2O
Indicators of biodegradation:
Reduction in dissolved oxygen
(3 mg DO needed to metabolize 1 mg of benzene)
Reduction in hydrocarbon concentration
Biodegradation sequence
Order of aerobic biodegradation:
Ethyl benzene
Toluene
Benzene
Xylene
Denitrification
Nitrate is electron acceptor
6NO3– + 6H+ + C6H6 → 6CO2↑ + 6H2O + 3N2 ↑
Actually occurs in multiple steps mediated by
different bacteria:
NO3 – → NO2– → NO → N2O → NH4+ → N2
Denitrification
Indicators of biodegradation:
Reduction in nitrate
Reduction in hydrocarbon concentration
Presence of denitrifying bacteria
Reducing conditions (dissolved oxygen < 1 mg/L)
Iron reduction
Insoluble iron(III) (ferric iron) is electron
acceptor
Reduced to soluble iron(II) (ferrous iron)
60H+ + 30Fe(OH)3 + C6H6 →
6CO2 + 30Fe2+ + 78H2O
Iron reduction
Indicators of iron biodegradation:
Increase in dissolved iron
Reduction in hydrocarbon concentration
Low or no dissolved oxygen
Sulfate reduction
Sulfate is electron acceptor
Sulfate reduction to sulfide
30H+ + 15SO42- + 4C6H6 →
24CO2 + 15H2S + 12H2O
Methanogenesis (Methane fermentation)
Not a redox reaction – fermentation reaction
Occurs only in highly anaerobic conditions
4C6H6 + 18H2O → 9CO2 + 15CH4
Methanogenesis
Indicators of methanogenesis:
Increase in methane and carbon dioxide
Reduction in hydrocarbon concentration
Very low or no dissolved oxygen
Presence of methanogenic bacteria
Carbon dioxide neutralization
All hydrocarbon degradation processes create
CO2
CO2 + H2O → H2CO3
(carbonic acid)
H2CO3 + CaCO3 → Ca2+ + 2HCO3CO2 neutralization increases alkalinity
8 mg alk produced per mg benzene degraded
Analytical protocol
Ground water:
Total hydrocarbons – confirm HC decrease
Aromatic hydrocarbons – confirm BTEX decrease
Oxygen – confirm utilization, redox state
Nitrate – confirm utilization
Iron(II) – confirm production
Sulfate – confirm utilization
Methane – confirm methanogenesis
Analytical protocol
Ground water:
Alkalinity – confirm CO2 production and
neutralization
Oxidation-reduction potential – confirm geochemical
environment
pH, temperature, conductivity, chloride –
confirmation of single ground-water system
Analytical protocol
Biological:
Field dehydrogenase test – confirm presence of
aerobic bacteria
Volatile fatty acids – biodegradation byproduct of
complex organic compounds
Microcosm studies – confirm biodegradation is
occurring
Average Relative Contribution of BTEX
Biodegradation Processes in Site
Ground Water at 42 sites
Methanogenesis
16%
Aerobic Oxidation
Nitrate Reduction
3%
3%
Iron (III) Reduction
4%
Sulfate Reduction
74%
Source: http://www.afcee.brooks.af.mil/er/ert/download/natattenfuels.ppt
Average Relative Contribution of BTEX
Biodegradation Processes in Site
Ground Water at 42 sites
(Excluding five sites with >200 mg/L Sulfate Reduction Capacity)
Aerobic Oxidation
8%
Methanogenesis
45%
Denitrification
7%
Iron (III) Reduction
12%
Sulfate Reduction
28%
Treatability Study Results (continued)
BTEX assimilative capacity averaged 64 mg/L
Field-scale biodegradation half-lives:
Range = 9 days to 9.5 years
Mean = 1 year.
BIOSCREEN
Microsoft Excel
Worksheet
BIOSCREEN
BIOSCREEN Natural
Natural Attenuation
Attenuation Decision
Decision Support
Support System
System
Hill
Hill AFB
AFB
Air
Air Force
Force Center
Center for
for Environmental
Environmental Excellence
Excellence
Version
Version 1.3
1.3
UST
UST Site
Site 870
870
Run
Run Name
Name
1.
1. HYDROGEOLOGY
HYDROGEOLOGY
Seepage
Seepage Velocity*
Velocity*
or
or
Hydraulic
Hydraulic Conductivity
Conductivity
Hydraulic
Hydraulic Gradient
Gradient
Porosity
Porosity
5.
5. GENERAL
GENERAL
Modeled
Modeled Area
Area Length*
Length*
Modeled
Modeled Area
Area Width*
Width*
Simulation
Simulation Time*
Time*
2.
2. DISPERSION
DISPERSION
Longitudinal
Longitudinal Dispersivity*
Dispersivity*
Transverse
Transverse Dispersivity*
Dispersivity*
Vertical
Vertical Dispersivity*
Dispersivity*
or
or
Estimated
Estimated Plume
Plume Length
Length
3.
3. ADSORPTION
ADSORPTION
Retardation
Retardation Factor*
Factor*
or
or
Soil
Soil Bulk
Bulk Density
Density
Partition
Partition Coefficient
Coefficient
FractionOrganicCarbon
FractionOrganicCarbon
Vs
Vs
1609.1
1609.1 (ft/yr)
(ft/yr)
KK
ii
nn
8.1E-03
(cm/sec)
8.1E-03 (cm/sec)
0.048
0.048 (ft/ft)
(ft/ft)
0.25
0.25 (-)
(-)
or
or
alpha
alpha xx
alpha
alpha yy
alpha
alpha zz
28.5
28.5
2.9
2.9
0.0
0.0
Lp
Lp
1450
1450
(ft)
(ft)
1.2
1.2
(-)
(-)
(ft)
(ft)
(ft)
(ft)
(ft)
(ft)
or
or
R
R
or
or
or
or
rho
rho
Koc
Koc
foc
foc
4.
4. BIODEGRADATION
BIODEGRADATION
lambda
1st
lambda
1st Order
Order Decay
Decay Coeff*
Coeff*
or
or
Solute
t-half
Solute Half-Life
Half-Life
t-half
or
or Instantaneous
Instantaneous Reaction
Reaction Model
Model
Delta
DO
Delta Oxygen*
Oxygen*
DO
Delta
NO3
Delta Nitrate*
Nitrate*
NO3
Observed
Fe2+
Observed Ferrous
Ferrous Iron*
Iron*
Fe2+
Delta
SO4
Delta Sulfate*
Sulfate*
SO4
Observed
CH4
Observed Methane*
Methane*
CH4
1.7
(kg/l)
1.7
(kg/l)
38
(L/kg)
38
(L/kg)
8.00E-04
8.00E-04 (-)
(-)
1450
1450
320
320
55
6.
6. SOURCE
SOURCE DATA
DATA
Source
Source Thickness
Thickness in
in Sat.Zone*
Sat.Zone*
Source
Source Zones:
Zones:
Width*
Width* (ft)
(ft) Conc.
Conc. (mg/L)*
(mg/L)*
50
0.07
50
0.07
11 11
25
2.8
25
2.8
22
100
99
100
33
25
2.8
25
2.8
44
50
0.07
50
0.07
55
Source
(see Help):
Help):
Source Decay
Decay (see
SourceHalflife*
Infinite
SourceHalflife*
Infinite (yr)
(yr)
Soluble
Soluble Mass
Mass
In
In NAPL,
NAPL, Soil
Soil
LL
(ft)
(ft)
(ft)
W
(ft) W
(yr)
(yr)
10
10 (ft)
(ft)
Data
Data Input
Input Instructions:
Instructions:
115
1.
115
1. Enter
Enter value
value directly....or
directly....or
2.
or
2. Calculate
Calculate by
by filling
filling in
in grey
grey
or
cells
0.02
cells below.
below. (To
(To restore
restore
0.02
formulas,
formulas, hit
hit button
button below).
below).
Variable*
Data
Variable*
in model.
model.
Data used
used directly
directly in
20
Value
20
model.
Value calculated
calculated by
by model.
(Don't
(Don't enter
enter any
any data).
data).
Vertical
Vertical Plane
Plane Source:
Source: Look
Look at
at Plume
Plume Cross-Section
Cross-Section
and
and Input
Input Concentrations
Concentrations && Widths
Widths
for
for Zones
Zones 1,
1, 2,
2, and
and 33
View
View of
of Plume
Plume Looking
Looking Down
Down
or
or
Infinite
Infinite
(Kg)
(Kg)
Observed
Observed Centerline
Centerline Concentrations
Concentrations at
at Monitoring
Monitoring Wells
Wells
IfIf No
No Data
Data Leave
Leave Blank
Blank or
or Enter
Enter "0"
"0"
7.
7. FIELD
FIELD DATA
DATA FOR
FOR COMPARISON
COMPARISON
Concentration
9.0
Concentration (mg/L)
(mg/L)
9.0
Dist.
00
145
Dist. from
from Source
Source (ft)
(ft)
145
8.0
290
290
1.0
1.0
435
435
580
580
725
725
870
870
.02
.02
.005
.005
1015
1015 1160
1160 1305
1305 1450
1450
6.9E+0
6.9E+0 (per
(per yr)
yr)
8.
8. CHOOSE
CHOOSE TYPE
TYPE OF
OF OUTPUT
OUTPUT TO
TO SEE:
SEE:
or
or
0.10
0.10
(year)
(year)
5.78
5.78
17
17
11.3
11.3
100
100
0.414
0.414
(mg/L)
(mg/L)
(mg/L)
(mg/L)
(mg/L)
(mg/L)
(mg/L)
(mg/L)
(mg/L)
(mg/L)
RUN
RUN
CENTERLINE
CENTERLINE
RUN
RUN ARRAY
ARRAY
View
View Output
Output
View
View Output
Output
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Recalculate
Recalculate This
This
Sheet
Sheet
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Example Dataset
Dataset
Restore
Restore Formulas
Formulas for
for Vs,
Vs,
Dispersivities,
Dispersivities, R,
R, lambda,
lambda, other
other
Anaerobic transformation of
carbon tetrachloride
CCl4 → CHCl3 → CH2Cl2 → CH3Cl
↓
CO2 + H2O + Cl–
Redox conditions:
Denitrification CCl4 → CHCl3
Sulfate reduction CCl4 → CO2 + H2O + Cl–
Abiotic degradation of TCA
CH3CCl3 → CH2CCl2 + CH3COOH → CO2 + H2O + Cl–
1,1,1-TCA → 1,1-DCE + Acetic acid → mineralization
Redox conditions:
All redox conditions
Anaerobic dechlorination of TCA
CH3CCl3 → CH3CHCl2 → CH3CH2Cl → CO2 + H2O + Cl–
1,1,1-TCA → 1,1-DCA → Chloroethane → mineralization
Redox conditions:
Sulfate reduction 1,1,1-TCA → 1,1-DCA
Methanogenesis 1,1,1-TCA → mineralization
Anaerobic degradation of PCE & TCE
CCl2=CCl2 → CHCl=CCl2 → CHCl=CHCl →
CH2=CHCl → CH2CH2 → CH3CH3
PCE
→
TCE
→ cis-1,2-DCE →
vinyl chloride → ethene → ethane?
Redox conditions:
Sulfate reduction PCE → DCE, TCE → DCE
Methanogenesis PCE → ethene, TCE → ethene
Analytical protocol
Ground water:
Same as for hydrocarbons, plus:
Methane – to confirm methanogenesis
Chlorinated VOCs – materials degraded and
degradation products
Distinguish cis-1,2-DCE and trans-1,2-DCE
Degradation byproducts: CO2, ethane, ethene,
chloride
Analytical protocols
Ground water:
Dissolved hydrogen – distinguishes strength of
dechlorination and redox state:
Electron acceptor
Denitrification
Iron reduction
Sulfate reduction
Reductive dechlorination
H2 concentration (ng/L)
< 0.1
0.2 to 0.8
1 to 4
>1
Methanogenesis
5 to 20
Extent of Chlorinated Solvents and
BTEX
BTEX and Electron Acceptors
Total BTEX
4,000 - 6,000 µg/L
2,000 - 4,000 µg/L
0 - 2,000 µg/L
Nitrate
Dissolved Oxygen
5 - 10 mg/L
1 - 5 mg/L
< 1 mg/L
Sulfate
2 - 4 mg/L
0.05 - 2 mg/L
< 0.05 mg/L
10 - 20 mg/L
0.05 - 10 mg/L
< 0.05 mg/L
BTEX and Metabolic Byproducts
Total BTEX
4,000 - 6,000 µg/L
2,000 - 4,000 µg/L
0 - 2,000 µg/L
Iron (II)
10 - 11 mg/L
5 - 10 mg/L
0.05 - 5 mg/L
pe
Methane
4-7
2-4
<2
>0.5 mg/L
0.3 - 0.5 mg/L
0 - 0.3 mg/L
00
1,800
1,800
Fee
Fee
tt
Chlorinated Solvents and Byproducts
Total BTEX
Trichloroethene
4,000
4,000 -- 6,000
6,000 µg/L
µg/L
2,000
2,000 -- 4,000
4,000 µg/L
µg/L
00 -- 2,000
2,000 µg/L
µg/L
Vinyl Chloride
>> 1,000
1,000 µg/L
µg/L
500
500 -- 1,000
1,000 µg/L
µg/L
ND
ND -- 500
500 µg/L
µg/L
Dichloroethene
5,000 µg/L
µg/L
>> 5,000
1,000 -- 5,000
5,000 µg/L
µg/L
1,000
1,000 µg/L
µg/L
00 -- 1,000
>> 10,000
10,000 µg/L
µg/L
1,000
1,000 -- 10,000
10,000 µg/L
µg/L
00 -- 1,000
1,000 µg/L
µg/L
Ethene
Chloride
>> 500
500 µg/L
µg/L
100
100 -- 500
500 µg/L
µg/L
ND
ND -- 100
100 µg/L
µg/L
>> 100
100 mg/L
mg/L
50
50 -- 100
100 mg/L
mg/L
ND
ND -- 50
50 mg/L
mg/L
Plot of TCE, DCE, VC, and Ethene versus
Distance Downgradient
Plume Classification
A
LNAPL
Plume
B
N
C
D
E
F
A
Primary Monitoring Well
Dissolved BTEX-CAH
Plume (1996)
0
500 1000 1500 2000
Adapted from: Carey, G. R., P. J. V. Geel, T. H. Wiedemeier, and E. A. McBean. "A Modified Radial Diagram Approach
for Evaluating Natural Attenuation Trends for Chlorinated Solvents and Inorganic Redox Indicators."
Ground Water Monitoring & Remediation 23, no. 4 (Fall 2003): 75-84.
Nitrate (NO3)
Manganese (Mn(II))
0.0
10
1
0.1
1
1
Oxygen (O2)
10
0.1
10
8
6
4
2
0
1
0.1
Methane (CH4)
0.0
1
10 0
100
10
1
0.1
Iron (Fe(II))
10
20
30
40
50
Sulfate (SO4)
NO3
Mn(II)
Fe(II)
O2
CH4
SO4
Aerobic
Methanogenic
Nitrate-Reducing
Sulfate-Reducing
Aerobic Background Concentrations
Manganogenic
Ferrogenic
Anaerobic Plume Concentrations
BIOCHLOR
Microsoft Excel
Worksheet
Cape
Data Input
Input Instructions:
Instructions:
Cape Canaveral
Canaveral Data
115
1.
Fire
Training
Area
115
1. Enter
Enter value
value directly....or
directly....or
Fire Training Area
BIOCHLOR
BIOCHLOR Natural
Natural Attenuation
Attenuation Decision
Decision Support
Support System
System
TYPE
TYPE OF
OF CHLORINATED
CHLORINATED SOLVENT:
SOLVENT:
Ethenes
Ethenes
Ethanes
Ethanes
Version
Version 1.1
1.1
for
for Excel
Excel 7.0/
7.0/ '95
'95
5.
5. GENERAL
GENERAL
Simulation
Simulation Time*
Time*
Modeled
Modeled Area
Area Width*
Width*
(ft/yr)
Modeled
(ft/yr)
Modeled Area
Area Length*
Length*
Zone
Zone 11 Length*
Length*
(cm/sec)
(cm/sec) Zone
Zone 22 Length*
Length*
1.
1. ADVECTION
ADVECTION
Seepage
Vs
111.7
Seepage Velocity*
Velocity*
Vs
111.7
or
or
or
or
KK
1.8E-02
Hydraulic
1.8E-02
Hydraulic Conductivity
Conductivity
Hydraulic
ii
0.0012
(ft/ft)
Hydraulic Gradient
Gradient
0.0012 (ft/ft)
Effective
nn
0.2
(-)
Effective Porosity
Porosity
0.2
(-)
2.
2. DISPERSION
DISPERSION
Alpha
40
Alpha xx Calc.
Calc. Method
Method
40 (ft)
(ft)
Change
Change Alpha
Alpha xx
(Alpha
0.1
(Alpha y)
y) // (Alpha
(Alpha x)
x)
0.1 (-)
(-)
Calc.
Method
Calc. Method
(Alpha
1.E-99
(Alpha z)
z) // (Alpha
(Alpha x)
x)
1.E-99 (-)
(-)
3.
3. ADSORPTION
ADSORPTION
Retardation
R
Retardation Factor*
Factor*
R
or
or
Soil
1.6
(kg/L)
Soil Bulk
Bulk Density,
Density, rho
rho
1.6
(kg/L)
1.8E-3
(-)
FractionOrganicCarbon,
1.8E-3
(-)
FractionOrganicCarbon, foc
foc
Partition
Koc
Partition Coefficient
Coefficient
Koc
426
7.1
(-)
PCE
426 (L/kg)
(L/kg)
7.1
(-)
PCE
130
(L/kg)
2.9
(-)
TCE
130
(L/kg)
2.9
(-)
TCE
125
2.8
(-)
DCE
125 (L/kg)
(L/kg)
2.8
(-)
DCE
30
(L/kg)
1.4
(-)
VC
30
(L/kg)
1.4
(-)
VC
302
5.3
(-)
ETH
302 (L/kg)
(L/kg)
5.3
(-)
ETH
2.9
Common
(used in
in model)*
model)* ==
2.9
Common R
R (used
-1st
4.
-1st Order
Order Decay
DecayCoef*
Coef*
4. BIOTRANSFORMATION
BIOTRANSFORMATION
λ
(1/yr)
Zone
1
half-life
λ
(1/yr)
Zone 1
half-life (yrs)
(yrs) Yield*
Yield*
PCE
TCE
2.00
0.79
PCE
TCE
2.00
0.79
0.74
TCE
DCE
1.00
0.74
TCE
DCE
1.00
0.64
DCE
VC
0.70
0.64
DCE
VC
0.70
VC
ETH
0.40
0.45
VC
ETH
0.40
0.45
λλ (1/yr)
Zone
half-life
(1/yr)
Zone 22
half-life (yrs)
(yrs)
PCE
TCE
0.00
PCE
TCE
0.00
TCE
DCE
0.00
TCE
DCE
0.00
DCE
VC
0.00
DCE
VC
0.00
VC
ETH
0.00
VC
ETH
0.00
ETH
Ethane
ETH
Ethane
6.
6. SOURCE
SOURCE DATA
DATA
Source
Source Options
Options
Run
RunName
Name
33
33
700
700
1085
1085
1085
1085
00
Conc.
Conc. (mg/L)*
(mg/L)*
PCE
PCE
TCE
TCE
DCE
DCE
VC
VC
ETH
ETH
LL
(yr)
(yr)
(ft)
(ft) W
W
(ft)
(ft)
(ft)
(ft)
Zone 2=
2=
(ft)
(ft) Zone
LL -- Zone
Zone 11
56
56
2.
2. Calculate
Calculate by
by filling
filling in
in gray
gray
Variable*
Data
Variable*
Data used
used directly
directly in
in model.
model.
Test
Test ifif
Natural
Natural Attenuation
Attenuation
Biotransformation
Biotransformation
Screening
Protocol
Screening
Protocol
is
Occurring
is Occurring
Vertical
Vertical Plane
Plane Source:
Source: Determine
Determine Source
Source Well
Well
Location
Location and
and Input
Input Solvent
Solvent Concentrations
Concentrations
TYPE:
TYPE: Single
Single Planar
Planar
Source
Source Thickness
Thickness in
in Sat.
Sat. Zone*
Zone*
Width*
(ft)
Width* (ft)
or
or
cells.
0.02
cells. Press
Press Enter,
Enter, then
then C
0.02
C
(To
(To restore
restore formulas,
formulas, hit
hit "Restore
"Restore Formulas"
Formulas" button
button ))
(ft)
(ft)
105
105
C1
C1
.056
.056
15.8
15.8
98.5
98.5
3.08
3.08
.03
.03
View
View of
of Plume
Plume Looking
Looking Down
Down
Observed
Observed Centerline
Centerline Conc.
Conc. at
at Monitoring
Monitoring Wells
Wells
7.
7. FIELD
FIELD DATA
DATA FOR
FOR COMPARISON
COMPARISON
PCE
.056
PCE Conc.
Conc. (mg/L)
(mg/L)
.056
TCE
15.8
.22
TCE Conc.
Conc. (mg/L)
(mg/L)
15.8
.22
DCE
98.5
DCE Conc.
Conc. (mg/L)
(mg/L)
98.5 3.48
3.48
VC
3.08
VC Conc.
Conc. (mg/L)
(mg/L)
3.08 3.08
3.08
ETH
.03
.188
ETH Conc.
Conc. (mg/L)
(mg/L)
.03
.188
Dist.
00
560
Dist. from
from Source
Source (ft)
(ft)
560
.017
.017
.776
.776
.797
.797
650
650
.024
.024
1.2
1.2
2.52
2.52
.107
.107
930
930
.019
.019
.556
.556
5.024
5.024
.15
.15
1085
1085
8.
8. CHOOSE
CHOOSE TYPE
TYPE OF
OF OUTPUT
OUTPUT TO
TO SEE:
SEE:
RUN
RUN CENTERLINE
CENTERLINE
RUN
RUN ARRAY
ARRAY
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Diffusive disappearance
Parker, B. L., R. W. Gillham and J. A. Cherry, 1994.
"Diffusive Disappearance of Immiscible-Phase
Organic Liquids in Fractured Geologic Media."
Ground Water, Vol. 32, No. 5, Pp. 805-820.
September/October 1994.
See Figure 1 of:
Parker, B. L., R. W. Gillham and J. A. Cherry, 1994. "Diffusive
Disappearance of Immiscible-Phase Organic Liquids in
Fractured Geologic Media." Ground Water, Vol. 32, No. 5, Pp.
805-820. September/October 1994.
FRACTURE APERTURE
2b
NAPL
JD = -nDe
MATRIX
¶C
¶x
POROSITY, n
EFFECTIVE DIFFUSION, De
z
1.0
Relative
Concentration
x
Distance (x-)
t4
t3
y
Distance (x+)
t2
t1
Dissolved
Sorbed
∂C
JD = −nDe
∂x
∂C D e ∂ 2C
=
R ∂x 2
∂t
Assume C(x = 0, t ) = S w
and C(x, t = 0 ) = 0
⎛ RD e ⎞
⎟⎟
JD (0, t) = −nS W ⎜⎜
⎝ πt ⎠
1/2
Integrate over time to get mass leaving fracture :
M t = nS w
(
)
4
1/2
RD e t
π
Equivalent Fx Aperture (m m)
1,000
100
10
Type Clay
f = 35%
R = 5.2
Type Shale
f = 10%
R = 3.2
Type Granite
f = 0.6%
R = 1.0
1
0.1
1
10
100
1,000
10,000
Time (days)
Comparison of TCE mass loss rates for three geologic media expressed in terms of equivalent immiscible-phase
fracture aperture and time for NAPL disappearance: type-clay R= 5.2, type-sandstone/shale R = 3.2, and
type-granite R= 1. Parameter values provided in the next slide.
Image adapted from: Parker, B. L., R. W. Gillhamand J. A. Cherry, 1994. "Diffusive Disappearance of Immiscible-Phase
Organic Liquids in Fractured Geologic Media." Ground Water, Vol. 32, No. 5. Pp. 805-820. September/October 1994.
Geologic media parameters for three type-fractured geologic media used for comparison of TCE mass loss rates
due to diffusion and sorption to matrix solids presented in figure: type-clay, type-shale/sandstone,
and type-granite.
Parameter
Porosity: f
Bulk density: r b (g/cm3)
Fraction organic carbon: foc
Apparent tortuosity: t
Clay
0.35
1.6
0.01
0.33
Type-geologic media Shale/sandstone
0.10
2.4
0.002
0.10
Granite
0.006
2.63
0
0.06
Combined parameters:
TCE & geologic media
Effective diffusion coefficient: De (cm2/s)
Retardation factor: R
3.3E-06
5.2
1.0E-06
3.2
6.0E-06
1
Image adapted from: Parker, B. L., R. W. Gillhamand J. A. Cherry, 1994. "Diffusive Disappearance of Immiscible-Phase
Organic Liquids in Fractured Geologic Media." Ground Water, Vol. 32, No. 5. Pp. 805-820. September/October 1994.