Presentation Based on: Other References:

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1 M EASUREMENT O F HYDROCARBON NATURAL ATTENUATION RATES IN SOILS USING PASSIVE CO 2 FLUX TRAPS

2 Presentation Based on: McCoy, K., Zimbron, J., Sale, T. and Lyverse, M. (2014), Measurement of Natural Losses of LNAPL Using CO 2 Traps. Groundwater. doi: /gwat Other References: Zimbron, J., T. Sale, and M. Lyverse US Patent. Gas flux measurement using traps. US B2. Issued 4/6/2014. Sihota, N.J., O. Singurindy, and K.U. Mayer CO2-efflux measurements for evaluating source zone natural attenuation rates in a petroleum hydrocarbon contaminated aquifer. Env. Sci. and Tech. 45, no. 2: Molins, S., K.U. Mayer, R.T. Amos, and B.A. Bekins Vadose zone attenuation of organic compounds at a crude oil spill site Interactions between biogeochemical reactions and multicomponent gas transport. J. Cont. Hydrol. 112:15 29.

3 Outline Background Methods Field Measurements Conclusions and Future Work 3

4 Background Biodegradation of petroleum hydrocarbons results in biogas production: C 8 H 18 + H 2 O CO 2 + CH 4

5 Background Mechanisms Volatilization Dissolution Biodegradation after Sihota et al., 2011 Most of the contaminant degradation (~ 98%) is emitted as CO 2 at ground level Mollins et al modeling study

6 NSZD Monitoring Alternatives Multi-Level Sampler CO 2 Flux Chamber 2 CO 2 Trap 2 Former LNAPL Source Monitoring Well CO 2 CO 2 Natural CO LNAPL Groundwater Direct measurements 1 Soil gas gradients 2 Gas flux at surface Lines of evidence 3 Hydrocarbon composition 4 Groundwater chemistry 5 Soil cores

7 Methods: CO2 Traps Atmospheric CO 2 (from diffusion or short-term pressure changes) Integral CO 2 flux measurement 2 sorbent elements Bottom element soil CO 2 Top element atmospheric CO 2 Travel blank for QC Lab analysis for total carbonate Soil CO 2 Soil US Pat, 8,714,034B2

8 Laboratory Tests: Is recovery quantitative? Small scale, closed system SORBENT MEDIA 3 WAY VALVE SOAP FILM FLOW METER GAS FLOW METER Na 2CO 3 SOLUTION N 2 CARRIER GAS HCl SOLUTION SYRINGE PUMP STIR PLATE Mc Coy, K CSU. M.Sc. Thesis

9 Laboratory Tests: Is recovery quantitative? Small scale, closed system SORBENT MEDIA 3 WAY VALVE SOAP FILM FLOW METER GAS FLOW METER Na 2CO 3 SOLUTION N 2 CARRIER GAS HCl SOLUTION SYRINGE PUMP STIR PLATE Large scale, open system Traps capture CO 2 quantitatively Mc Coy, K CSU. M.Sc. Thesis

10 Data from 6 Field Sites 3 former refineries, 2 active refineries, 1 rail yard 117 sampling locations 194 CO 2 Trap measurements

11 Field Deployment of CO2 Traps Traps directly deployed at grade Typical deployment time is 2-weeks Lab analysis for total carbon and isotopic analysis

12 Site 1: Measured CO2 Fluxes Symbol size proportional to measured CO 2 flux (μmol/m 2 /sec). Measured CO 2 fluxes significantly larger over LNAPL body than background locations. Some LNAPL-impacted locations not significantly different from background. Mc Coy, K CSU. M.Sc. Thesis

13 Units CO 2 mmol/m 2 /sec Unit of raw measurement LNAPL gal/acre/yr Unit for remediation metrics Flux tot = Flux background + Flux NA LNAPL

14 Site 1: Calculated LNAPL Losses Symbol size proportional to background corrected LNAPL loss rate (gallons/acre/yr). Calculated LNAPL loss rates (as C 6 H 6 ) range from ,300 gal/acre/yr. Uncolored symbols are not significantly different from background. Mc Coy, K CSU. M.Sc. Thesis

15 Carbon Isotope Analysis 14 C (a.k.a. carbon dating) helps determine fossil fuel fraction (ff) (Avery, et al. 2006) of captured CO 2 13 C -microbes utilize lighter isotopes (Ehrlich, 1996), so microbially produced CO 2 should be 12 C enriched (i.e. 13 C depleted)

16 Isotope Analysis Results

17 Isotope Analysis Results d 13 C LNAPL = -27 Results from 14 C analysis indicate CO 2 produced is from fossil fuel (NAPL) Loss rate calculated from fossil fuel fraction matches loss rate calculated by background correction. 13 C depletion indicates CO 2 production is the result of biodegradation

18 Site 1: In-Well Thermal Profiles Background LNAPL impacted Biodegradation is exothermic: C 8 H 18 + O 2 H 2 O + CO 2 DH = 48 KJ/g

19 Site 1: Temperature Dependence of LNAPL Loss 14,000 BG Adj. LNAPL Loss (gal/acre/yr) 12,000 10,000 8,000 6,000 4,000 2, Maximum Temperature (⁰C)

20 Site 1: Temperature Dependence of LNAPL Loss BG Adj. LNAPL Loss (gal/acre/yr) 14,000 12,000 10,000 8,000 6,000 4,000 2,000 McCoy et al, 2014, Groundwater. Field Data Maximum Temperature (⁰C) Lab Microcosm Data Zeman et al, 2014, Biodegradation.

21 Trap design is simple, robust, easy to use Time-integrated measurements for weeks at a time Measured CO 2 fluxes are large and indicate large LNAPL losses Other lines of evidence for LNAPL natural losses: LNAPL extent Soil temperature (consistent with self-catalyzed exothermic reaction) 14 C as indicator of source age (petroleum vs. recent carbon) 13 C as indicator of generation mechanism Accounting only from petroleum-derived CO 2 is key Carbon isotope ( 14 C) analysis Conclusions Alternatively, use background correction (from unimpacted locations)

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23 NSZD as a remedy Provided other criteria are met, such as lack of migration NSZD as benchmark for active remedies: Hydraulic Recovery SVE systems Data Use Examples Performance Monitoring for Active Remedies

24 Regulatory Acceptance the plan will attain a degree of cleanup and control of hazardous substances such that the property will not present an unacceptable risk to human health or the environment

25 On Going and Future Work Data quality Vs. quality Integration of trap data with other tools

26 On Going and Future Work Additional trap applications: Other contaminants: SVI Other CO 2 flux applications: MNA of chlorinated solvents (i.e., SERDP 2338) Performance monitoring. For example: Chemox Bioaugmentation/biostimulation Others

27 Julio Zimbron, Ph.D.