Environmental Geophysics Applied to Site Characterization, Plume - PowerPoint PPT Presentation

Environmental Geophysics Applied to Site Characterization, Plume Mapping, and Remediation Monitoring Dale Werkema, Ph.D. Research Geophysicist ORD, NHEERL, WED, PCEB werkema.d@epa.gov

Why geophysics? • Prior to expensive and invasive surgery we utilize medical imaging. • Each medical imaging method is used for specific purposes. images credit: Lee Slater x-ray of knee MRI of knee • Prior to expensive earth intrusive investigations (e.g., drilling, excavating, etc.) we can utilize geophysical imaging. • Each geophysical method is used for specific purposes 2 Landfill plume mapping Abandoned well mapping

Outline • Locating subsurface objects and infrastructure • Plume detection and monitoring • High resolution characterization and Conceptual Site Model (CSM) Development • GW/SW Interactions • Online resources Geophysical methods include a set of tools in the site investigator’s tool box. 3

Finding USTs & subsurface infrastructure • What are the physical properties of the target, i.e. NORTH UST and associated infrastructure? Ambient Net Body Ø metal?, ferrous metal? fiberglass? Body Anomaly Anomaly • Any potential interference? Likely applicable geophysical methods: 1. Magnetic 2. Electromagnetic 3. Ground Penetrating Radar (GPR) Geometrics G-858 Cesium vapor magnetometer Geophex GEM2 Geonics EM-61 Mala GPR system Geonics EM-31

Finding USTs & subsurface infrastructure Total Magnetic Field Intensity (nT)

Finding USTs & subsurface infrastructure Geonics EM-31 EM 31 Quadrature

Finding USTs & subsurface infrastructure Ground Penetration Radar (GPR) UST and utility examples 500 MHz antenna GSSI antenna • pipes oriented perpendicular to the profile. • Darker reflections show higher amplitude due to greater electrical property impedance. • Faint reflections show 400 MHz antenna muted or low amplitude reflections due to the attenuation of the GPR energy from electrically telephone cable conductive material. steel pipe 2 steel pipes Note: Hyperbolic Reflections PVC pipe GPR sections from Bill Sauck

Mapping contaminant plumes Direct Current (DC) Resistivity Archie's Law for Porous Media w/o clay ρ e = a φ -m S -n ρ w Measured Current potential v source ρ e = resistivity of the earth φ = fractional pore volume (porosity) S = fraction of the pores containing fluid ρ w = the resistivity of the fluid Lines of n, a and m are empirical constants equal potential Current flow lines Resistivity Surveying

Deep Water Horizon (DWH) , Grand Terre, LA. • Uninhabited barrier island impacted by Deepwater Horizon oil spill • No anthropogenic noise makes it ideal to study the long term fate of the oil contamination • Oil contamination is located 40-60 cm below the surface and is bounded by sand 9

DWH Barrier Island Impact DC Resistivity Results Zone of immature oil contamination imaged as resistive layer Oil layer Offshore Inland SE NW thinning of oil layer? Approximate location of ~0.3 Depth (m) -2 m thick oil layer saltwater-saturated sands -4 2 4 6 8 10 12 14 Distance (m) 100 10 Oil Resistivity (Ohm m) layer Oil impact thins away from the shoreline Heenan, J., Slater, L.D., Ntarlagiannis, D., Atekwana, E.A., Fathepure, B.Z., Dalvai, S., Ross, C., Werkema, D.D., and Atekwana, E.A., Geophysics , 2014

DWH Barrier Island Time-Lapse Adaptation of field resistivity system to remote solar power acquisition ave. resistance of anomaly vs. time Microcosm experiments using site samples shows rapid and dynamic hydrocarbon degradation black solid = benzene active black dotted = benzene control red solid = toluene active red dotted = toluene control 15 months resistivity Heenan, J., Slater, L.D., Ntarlagiannis, D., Atekwana, E.A., Fathepure, B.Z., Dalvai, S., Ross, C., Werkema, D.D., and Atekwana, E.A., Geophysics , 2014

NonAqueous Phase Liquid (NAPL) DC resistivity response Controlled Kerosene Spill Conductivity (mS/m) Hydrocarbons are 0.00 1.00 2.00 3.00 4.00 5.00 6.00 0.00 1.00 2.00 3.00 4.00 5.00 6.00 Electrically Resistive (initially) 0 0 ARCHIE ’ S LAW (1942): 0.2 0.2 0.4 0.4 ρ e = a φ -m S -n ρ w 0.6 0.6 Depth (m) 0L 0L 0L ρ e = resistivity of the earth 0.8 0.8 100L 100L 100L φ = fractional pore volume (porosity) 200L 200L 200L 1 1 S = fraction of the pores 343L 343L 343L containing fluid 1.2 1.2 ρ w = the resistivity of the fluid L of Injected 1.4 1.4 n, a and m are constants Kerosene 1.6 1.6 Decreasing conductivity Decreasing conductivity 12 De Ryck et al., 1993

Field Site: Bulk Conductivity Profiles in-situ resistivity probes Contaminated location Uncontaminated location Conductivity (mS/m) Conductivity (mS/m) 0 10 20 30 40 0 10 20 30 40 S ilt & C lay S and 227 227 227 227 G ravel S ilt & C lay S and G ravel 226 226 226 226 Elevation (m) 225 225 225 225 224 224 224 224 No LNAPL No LNAPL Residual LNAPL 0 50 100 Residual LNAPL % Grain Size Free LNAPL 0 50 100 Free LNAPL Dissolved LNAPL % Grain Size Dissolved LNAPL Clay - Aquitard Clay - Aquitard Acidobacteria = Common soil bacteria Methylotrophs + Aromatic Hydrocarbon Degraders Iron and sulfur reducers & Hydrocarbon degrading 13 fermenters Werkema Jr., D.D., Atekwana. E.A., Endres, A., Sauck, W.A. and Cassidy. D.P., Geophysical Research Letters , 2003

DC Resistivity of mature LNAPL plume % change conductivity contaminated - clean -100 0 100 200 300 400 -100 0 100 200 300 400 ↑ 142% 10 N o L N A P L 200 200 F r e e L N A P L Depth (cm) L a b F i e l d 227.0 ↑ 250% 160 160 DIC mg C/L Ca 2+ mg/L 20 Elevation (m) 226.5 120 120 ↑ 120% 30 226.0 80 80 ↑ 175% 40 40 40 225.5 wt range 0 0 Lab Field Lab Field Lab C a2+ Field C a2+ Lab D IC Field D IC 225.0 50 % change of Ca 2+ and DIC 224.5 clean 60 contaminated 224.0 No LNAPL aminated Bacteroidetes 70 Residual LNAPL Bacilli Clostridia Free LNAPL Dissolved LNAPL Bacilli Aquitard – Clay α -proteobacteria Unit 16S rRNA gene community composition Geophysical response is coincident with microbiology and geochemical changes Werkema Jr., D.D., Atekwana. E.A., Endres, A., Sauck, W.A. and Cassidy. D.P., Geophysical Research Letters , 2003

Induced Polarization (IP) and Spectral Induced Polarization (SIP) SIP (frequency domain): Real or In-phase: ( σ ‘ = | σ | cos φ ) • fluid chemistry, • electrolytic conduction, and • interfacial component Imaginary, out-of-phase, or quadrature ( σ “ = | σ | sin φ ) IP (time domain): • physicochemical properties at fluid-grain interface • surface charge density, • ionic mobility, • surface area, and V s V • tortousity p t 1 t 2 +V Voltage Voltage 0 -V 0 0.5 1 1.5 2 Time (s) Time (s) t 1 2 φ M V ( t ) dt = ∫ Chargeability = V 15 p t 1 Slide credit: Lee Slater

MNA Field Example with core sample measurements zone of hydrocarbon impact Ex Experimental – biostimulated 1.6E-05 -J2 Co Control 1.5E+05 1.4E-05 Imaginary Conductivity (S/m) Lab cells/g Lab SIP Cell Concentration (cells/g) 1.2E-05 1.0E-05 1.0E+05 8.0E-06 6.0E-06 5.0E+04 4.0E-06 2.0E-06 0.0E+00 0.0E+00 0 10 20 30 40 50 60 0 10 20 30 40 50 60 Time (days) Time (days) 16 n SEM: Day 23 experimental column n SEM: Day 23 control column Abdel Aal, G. Z., Atekwana, E. A., Rossbach, S., and Werkema Jr., D.D., Journal of Geophysical Research , 2010

Relationship of Chlorinated Solvent (CS) abiotic degradation rates and Magnetic Susceptibility • CS abiotic degradation rates in saturated soil vs. Magnetic Susceptibility • Wilson has suggested that MS should be measured at all chlorinated solvent sites to identify abiotic degradation rates. (Wilson, PM, 2013) 17

Magnetic Susceptibility (MS) at Bemidji, MN Bemidji, MN. Proxy (MS) measurements of the accumulation of magnetite may be adopted as a non-invasive technology for monitoring long-term natural attenuation of crude oil in the subsurface? 18 Atekwana, Mewafy, Abdel Aal, Werkema, Revil and Slater, Journal of Geophysical Research, 2014

Magnetic Property Enhancement dissolved phase Y plume χ 10 -4 χ 10 -4 χ 10 -4 χ 10 -4 χ 10 -4 Y ʹ (DPP) 0 100 200 300 0 100 200 300 0 100 200 300 0 100 200 300 0 100 200 300 9014 G0907 G0906 G0903 G0905 432 432 free 430 430 phase Elevation in meter (masl) plume 428 428 Elevation in meter (masl) (FPP) 426 426 HOL HWT HWT HWT HWT 424 HWT 424 LWT LOL LWT LWT LWT LWT 422 422 420 420 418 418 Free phase plume X-X ʹ Free phase plume Y-Y ʹ 160 160 120 120 Dissolved phase plume Dissolved phase plume χ 10 -4 χ 10 -4 80 80 40 40 0 0 9018 503 9014 1101a 1101d 925F 9014 G0907 G0906 G0903 G0905 Vadoze Zone Zone of WT fluctuation Saturated Zone Vadose zone MS above FPP higher FPP MS higher vs. DPP MS values vs. locations above DPP Slide credit: Water table fluctuation zone is the most biogeochemical active Estella Atekwana