persistent groundwater contaminant plumes: processes, characterization… · 2014-02-21 ·...
TRANSCRIPT
Persistent Groundwater Contaminant Plumes: Processes, Characterization,
and Case Studies
UA-SRP & USEPA Seminar Series- Webinar February 24, 2014
Mark L. Brusseau
School of Earth & Environmental Sciences University of Arizona
1
Constrained Mass Removal & Plume Persistence
“significant limitations with currently available remedial technologies persist that make achievement of MCLs throughout the aquifer unlikely at most complex groundwater sites in a time frame of 50-100 years.”*
“Complex” groundwater sites are defined as those that have DNAPL present (e.g., chlorinated solvents) and that have substantial subsurface heterogeneity, including the presence of extensive lower-permeability units or fractured media.
• Why does this situation exist?
• What options are available?
*National Research Council (NRC). 2013. Alternatives for Managing the Nation's Complex Contaminated Groundwater Sites. Wash., DC 2
Outline
• Chlorinated-solvent sites- prevalence and issues
• Constrained mass removal and plume persistence: Impact of DNAPL source zones
• Constrained mass removal and plume persistence: Impact of mass storage in lower-K zones & hydraulic factors
• Constrained mass removal and plume persistence: Impact of sorbed mass
• Summary
3
~1600 SUPERFUND Sites
~80% have Chlorinated-Solvent Contaminants
4
Arizona Sites
Chlorinated-Solvents Presence:
State: 31/35
Federal: 13/15
5
Groundwater Contamination Sites in Tucson
Chlorinated-Solvent Contaminants are Primary Concern 6
at all 9 Sites
Groundwater Remediation Standard Method = Pump and Treat
Very effective for plume containment
7
Impact of P&T on Water Resources
• Analysis for Tucson [Brusseau & Narter, 2013]- year 2010
• Compare aggregate volume of groundwater extracted for all P&T systems to total metropolitan groundwater withdrawal
• Total groundwater withdrawal for all P&T systems = 16.6 M m3
• This is ~20% of the total groundwater withdrawal in Tucson
• Treated water used primarily for potable water or re-injection
• Represents ~6% of total potable water supply
8
Three Chlorinated-Solvent Sites in Arizona
• TCE is Primary COC • Very Low Retardation (R<2) • No Measurable Transformation Processes • V. Low Biogeochemical Attenuation Capacity
Large Plumes (several km long)
11 KM
4.5 KM
9
9 KM
Pump & Treat CMD Data
Composite Measure: CMD = Q * C
- OU1 Q = pumping rateC = concentration
~90% Reduction Currently ~ 1 kg/d
Asymptotic conditions
~2 equivalent pore volumes displaced
10
Constrained Mass Removal & Plume Persistence
Potential Factors: • Uncontrolled DNAPL Sources
• Plume-scale Lower-K Zones and Mass Storage (diffusive mass transfer- “back diffusion”)
• Plume-scale Sorbed-phase Mass Storage (sorption/desorption processes)
• Hydraulic Factors (P&T well-field, etc)
• Low Attenuation Capacity
• Other (Institutional, Analytical, etc)
11
Constrained Mass Removal & Plume Persistence
Need to Determine Relative Significance of Each Factor, and Site-dependent Functionality
Long Known:
12
1989
Tucson International Airport Area Superfund
Site
• TCE/DCE Contamination Identified in 1981
• Site Placed on Superfund NPL in 1983
• Pump and Treat started in 1987 (south plume)
• Source-zone Remediation efforts [SVE, ISCO]
• UA Collaboration since 1993
13
Composite CMD: AFP44
1987
High-resolution Temporal Data set
Asymptotic conditions
Start Pump & Treat
14
Constrained Mass Removal & Plume Persistence
Question: What is the relative significance of each of the various Persistence/Attenuation factors for this site?
Conducted an integrated Laboratory, Field, and Modeling study
15
Plume-scale Modeling Effort
~50 km2
Known Inputs
Conduct series of scenario-testing sensitivity analyses
16
17
Impact of Transport Processes
K Variability & Diffusive Mass Transfer (back diffusion)
18
Impact of Transport Processes
Sorption-desorption (nonlinear, rate limited)
[Sims include physical heterogeneity] 19
Impact of Transport Processes Controlling Factor for Early Phase DNAPL in Source zones
20
Source-zone Architecture, DNAPL Dissolution, and Mass Removal
Multi-scale Investigations of Systems
21
APS
~6 mm ~10 cm ~2 m
Pore Core Intermediate
DNAPL Source Behavior Pore-scale Imaging: 10 um resolution
1 2 3 41
2 3
4
Desorption Control
NAPL Dissolution Control [1-4]: Non-uniform accessibility
No-NAPL Expt
2 3 4
2 3 4
Column Experiments
Rel
ativ
e C
once
ntra
tion
22
DNAPL Source Behavior
Flow-cell Experiments
DNAPL Sn Imaging
1
10
100
1000
10000
100000
0 20 40 60 80 100 120 140 160 180
Con
cent
ratio
n (m
g/L)
Pore Volume
Control- Homogeneous
Mixed Source
Heterogeneous
Heterogeneous-2
Laboratory Experiments - Known DNAPL distributions - Permeability variability - Measure DNAPL in situ
23
DNAPL Source Behavior
Variables:
• Domain size [20 vs 10,000 m2]
• Gradient & Q [natural vs induced]
• Initial DNAPL Mass
Field Data
0.0001
0.001
0.01
0.1
1
10
0 50 100 150 200
CM
D (K
g/d)
Time (month)
AFP44- 3
3 Hangers
Dover- Surf
24
Difficult to conduct comparative analysis
Data Analysis & Interpretation
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Frac
tiona
l Mas
s D
isch
arge
Red
uctio
n
Fractional Mass Reduction
1:1 (First order)
Minimal Reduction (efficient mass removal)
Maximal Reduction (inefficient mass removal)
0.001
0.01
0.1
1
0 5 10 15 20
Rel
ativ
e C
once
ntra
tion
or R
elat
ive
CM
D
Relative Time
1:1
Minimal Reduction
Maximal Reduction
- Employ contaminant mass discharge (CMD) metric
- Determine relationship between reduction in mass discharge and reduction in mass
- Enhances comparative analysis
25
DNAPL Source Behavior
Contaminant Mass Distribution [Accessibility] {source architecture, site age (mass removed)}
Field Data Flow-cell Experiments
0
0.2
0.4
0.6
0.8
1
0 0.2 0.4 0.6 0.8 1
Frac
tion
Red
uctio
n in
CM
D
Fraction Reduction in Mass
TIAA-1
TIAA-2
Visualiz.
Dover-CSF
Dover-Surf
Borden-1
Borden-2
Increasing fraction of poorly accessible mass)
0
0.2
0.4
0.6
0.8
1
0 0.2 0.4 0.6 0.8 1
Frac
tiona
l Red
uctio
n in
CM
D
Fractional Reduction in Mass
Control-homogeneous Mixed Source Heterogeneous-1 Heterogeneous-2
26
Post Source-zone Remediation
Persistence Factors:
• Residual DNAPL Sources (incomplete removal/containment)
• Plume-scale Lower-K Zones and Mass Storage (diffusive mass transfer- “back diffusion”)
• Plume-scale Sorbed-phase Mass Storage (sorption/desorption processes)
• Hydraulic Factors (P&T well-field, etc)
• Other (Institutional, Analytical, etc)
27
Composite CMD: AFP44
SVE Start
ISCO Start
1987
Impacts from Source Remediation efforts
Current CMD = 0.2 kg/d
Pre SZR CMD = 2 kg/d
~90% Reduction
ISCO End
SVE End
28
Plume Persistence after Source Remediation
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Con
tam
inan
t Mas
s D
isch
arge
(Kg/
d) Simulated-
Remediation Simulated- No Remediation Measured
Non-source Factors: *Plume-scale*
1. Mass in Lower-K Zones 2. Sorbed Mass 3. Hydraulic Factors (well field)
*Ideal case- all source mass removed
Predictions for AFP44 Site
0 2 4 6 8 10 12 14
Time (Y) 29
Lower-permeability Zones & Diffusion
0.001
0.01
0.1
1
10
100
0 5 10 15 20 25
Mas
s R
emai
ning
(%)
Relative Time
0 1 3.5 Modflow: Clay-Sand-Clay
Mass R
emoved (%
)
90
99
99.9
99.99
0
0.2
0.4
0.6
0.8
1
0 0.2 0.4 0.6 0.8 1
Frac
tion
Red
uctio
n in
Mas
s D
isch
arge
Fraction Mass Reduction
Model Simulations
Stochastic (random K fields) vs.
Discrete (homogeneous, orthogonal) layers (MODFLOW)
30
0
1
3.5
Modflow: Clay-Sand-Clay
Variance of lnK
Well-field Configuration
0.001
0.01
0.1
1
0 5 10 15 20 25
Rel
ativ
e C
once
ntra
tion
Relative Time
3 longitudinal wells
3 downgradient (transverse) wells 9 uniform-dist wells
Natural gradient (equiv Q)
Model Simulations
3–Layer system (Clay-Sand-Clay) [MODFLOW]
31
Sorption-Desorption Processes
Extensive Elution Tailing
• Observed for all media
• Occurs with short contact times
• Need continuous-distribution domain model
Causative Mechanisms?
0.0000001
0.000001
0.00001
0.0001
0.001
0.01
0.1
1
0 500 1000 1500 2000 2500 3000 3500 4000
Rel
ativ
e C
once
ntra
tion
Pore Volumes
Non-Linear, Rate-Limited Sorption
Linear, Rate-Limited Sorption
Non-Linear, Equilibrium Sorption
Measured
RLS >> NLS
Column Experiments
32
Sorption-Desorption Processes 1
Eustis 0.1
0.01
Progressive increase0.001
in resistance with increasing contact0.0001
time 0.00001
0.000001
0.0000001
2 PV
4 PV
8 PV
20 PV
100 PV
1000 PV
Aged 30 days
Aged 420 days
Aged 4 years
Interaction with Hard Carbon
[sorbate permeation within, and sorbate-induced deformation of,
the HC matrix]
1
0.1 Replication Exp 1
Exp 2
Exp 3
Rel
ativ
e C
once
ntra
tion
0 1000 2000 3000 4000 5000 6000 7000 8000 9000
Pore Volumes
98% quartz sand 2% clay (kaolinite- non-expanding) 0.38% organic carbon 0.14% hard carbon (kerogen, bc)
Rel
ativ
e C
once
ntra
tion Exp 4
0.01 Simulation
0.001
0.0001
0.00001
0.000001 Non-linear sorption Competitive sorption 0.0000001
0 500 1000 1500 2000 2500 3000 3500 4000
Pore Volumes 33
Sorption-Desorption Processes
98-80% quartz, feldspars 2-20% clay (montmorillonite- expanding) 0.03% organic carbon 0.02% hard carbon (kerogen, bc)
Non-linear sorption
Peak Shift = change in d-spacing
AFP 44 Sediment
XRD Analysis: several AFP44 samples and 2 (mont) specimen controls
Clay inter-layer d-spacing = ~0.3-0.6 nm TCE thickness = ~0.3 nm Increase in d-spacing for TCE treatment
= ~0.4 nm
TCE Intercalation [+ HCI]
No apparent aging effect
34
Summary: 3 Hanger Site at TIAA
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0 10 20 30 40 50 60
Con
tam
inan
t Mas
s D
isch
arge
(kg/
d)
Elapsed Time (month)
Hydraulic Source Control
Plume Reduction = ~50%
Identify Relevant Factors:
1. Low-K Zones and DMT 2. Source Residual 3. Well-field Configuration
[~2-3 pore volumes]
35
Measured Model Simulation
Summary: continued
• Source Zones- incomplete removal/containment of contamination, continuing source
• Large, Persistent Plumes- contributing factors
• Site “Architecture” and “Age” key factors – Subsurface properties (permeability field, flow field) – Contaminant distribution (phases, relative accessibility) – Change in contaminant distributions and accessibility as sites age
• Alternatives to P&T ?
• Long-term Site Management
36
Acknowledgements
• The many students and post-docs who have contributed to this research; our collaborators and partners with EPA, AECOM, US Air Force, CRA, Tucson Airport Authority, ADEQ.
• Financial support provided by the National Institute of Environmental Health Sciences Superfund Research Program (ES04940), the US Department of Defense Strategic Environmental Research and DevelopmentProgram (ER-1614), the US Air Force, and the Tucson Airport Authority
37
References • Brusseau, M.L.; Nelson, N.T.; Zhang, Z.; Blue, J.E.; Rohrer, J.; Allen, T. 2007. Source-Zone Characterization of a Chlorinated-Solvent Contaminated Superfund Site
in Tucson, AZ. J. Contam. Hydrol., 90:21-40.
• Brusseau, M.L., Hatton, J., and DiGuiseppi, W. 2011. Assessing the Impact of Source-Zone Remediation Efforts at the Contaminant-Plume Scale: Application to a Chlorinated-Solvent Site. J. Contam. Hydrol., 126:130-139.
• Brusseau, M.L., Carroll, K.C., Allen, T., Baker, J., DiGuiseppi, W., Hatton, J., Morrison, C., Russo, A., and Berkompas, J. 2011. The Impact of In-situ Chemical Oxidation on Contaminant Mass Discharge: Linking Source-zone and Plume-scale Characterizations of Remediation Performance. Environ. Sci. Technol., 45:5352-5358.
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• Brusseau, M.L. 2013. Use of Historical Pump-and-Treat Data to Enhance Site Characterization and Remediation Performance Assessment. Water Air Soil Poll., 224: article 1741.
• Brusseau, M.L. and Narter, M. 2013. Assessing the Impact of Chlorinated-Solvent Sites on Metropolitan Groundwater Resources. Groundwater, 51(6): 828-832.
• Brusseau, M.L.; Matthieu III, D.E.; Carroll, K.C.; Mainhagu, J.; Morrison, C.; McMillan, A.; Russo, A.; Plaschke, M. 2013. Characterizing Long-term Contaminant Mass Discharge and the Relationship Between Reductions in Discharge and Reductions in Mass for DNAPL Source Areas. J. Contam. Hydrol., 149: 1-12.
• Chorover, J. and Brusseau, M.L. 2008. Kinetics of Sorption-Desorption, pgs 109-149 in Kinetics of Water-Rock Interaction, S.L. Brantley, J. Kubicki, and A.F. White, Editors, Springer, New York, NY.
• DiFilippo, E.L. and Brusseau, M.L. 2008. Relationship Between Mass Flux Reduction and Source-zone Mass Removal: Analysis of Field Data. J. Contam. Hydrol., 98:22-35.
• DiFilippo, E.L., Carroll, K.C., and Brusseau, M.L. 2010. Impact of Organic-Liquid Distribution and Flow-Field Heterogeneity on Reductions in Mass Flux. J. Contam. Hydrol., 115:14-25.
• Johnson, G.R., Norris, D.K., and Brusseau, M.L. 2009. Mass Removal and Low-concentration Tailing of Trichloroethene in Freshly-amended, Synthetically-aged, and Field-contaminated Aquifer Material. Chemosphere, 75:542–548.
• Matthieu III, D.E., Brusseau, M.L., Johnson, G.R., Artiola, J.L., Bowden, M.L., Curry, J.E. 2013. Intercalation of Trichloroethene by Sediment-Associated Clay Minerals. Chemosphere, 90:459-463.
• Russo, A., Johnson, G.R., Schnaar, G., and Brusseau, M.L. 2010. Nonideal Transport of Contaminants in Heterogeneous Porous Media: 8. Characterizing and Modeling Asymptotic Contaminant-Elution Tailing for Several Soils and Aquifer Sediments. Chemosphere, 81:366-371.
• Schnaar, G. and Brusseau, M.L. 2006. Characterizing pore-scale dissolution of organic immiscible liquid in natural porous media using synchrotron X-ray microtomography. Environ. Sci. Technol., 40:6622-6629.
• Zhang, Z. and Brusseau, M.L. 1999. Nonideal Transport of Reactive Solutes in Heterogeneous Porous Media: 5. Simulating Regional-Scale Behavior of a Trichloroethene Plume During Pump-and-Treat Remediation. Water Resour. Res., 35: 2921-2935. 38