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Welcome to the CLU-IN Internet Seminar

Welcome to the CLU-IN Internet Seminar. Stable Isotope Analyses to Understand the Degradation of Organic Contaminants in Ground Water Sponsored by: U.S. EPA Technology Innovation and Field Services Division Delivered: September 9, 2010, 2:00 PM - 4:00 PM, EDT (18:00-20:00 GMT)

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Welcome to the CLU-IN Internet Seminar

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  1. Welcome to the CLU-IN Internet Seminar Stable Isotope Analyses to Understand the Degradation of Organic Contaminants in Ground Water Sponsored by: U.S. EPA Technology Innovation and Field Services Division Delivered: September 9, 2010, 2:00 PM - 4:00 PM, EDT (18:00-20:00 GMT) Instructor:John T. Wilson, U.S. EPA, R.S. Kerr Environmental Research Center (wilson.johnt@epa.gov) Moderator:Jean Balent, U.S. EPA, Technology Innovation and Field Services Division (balent.jean@epa.gov) 1 Visit the Clean Up Information Network online atwww.cluin.org

  2. Housekeeping Please mute your phone lines, Do NOT put this call on hold press *6 to mute #6 to unmute your lines at anytime Q&A Turn off any pop-up blockers Move through slides using # links on left or buttons This event is being recorded Archives accessed for free http://cluin.org/live/archive/ Download slides as PPT or PDF Go to slide 1 Submit comment or question Report technical problems Move back 1 slide Go to seminar homepage Go to last slide Move forward 1 slide 2

  3. Applications of Stable Isotope Analyses to Understand the Degradation of Organic Contaminants in Ground WaterPart 1. Applications John T. Wilson, U.S. Environmental Protection Agency 3

  4. If you have questions, or want to request a copy of the Powerpoint file, send e-mail to wilson.johnt@epa.gov.

  5. Volatile organic contaminants in ground water are usually composed of carbon, hydrogen and chloride. Each of the these elements have more than one stable isotope. These stable isotopes are not radioactive. The stable isotopes differ from each other in the number of neutrons in the nucleus of the atom.

  6. As organic compounds degrade, the ratio of stable isotopes in the fraction remaining after degradation may change in a predictable way. Compound specific stable isotope analyses (CSIA) can provide an unambiguous conservative boundary on the extent of degradation of organic compounds in ground water.

  7. OSWER Directive 9200.4-17Pin regard to- Sites Where MNA May Be Appropriate • MNA is appropriate as remedial approach only where it: • Can be demonstrated to achieve remedial objectives within a reasonable time frame, and • Meets the applicable remedy selection criteria for the particular regulatory program. To make the evaluation, must know the rate of natural attenuation.

  8. OSWER Directive 9200.4-17Pin regard to- Demonstrating the Performance of MNA Three types of site-specific information may be required: • Historical ground water and/or soil chemistry data demonstrates a trend of declining contaminant concentration. • Hydrogeologic and geochemical data that demonstrate NA processes and rates. • Data from field or microcosm studies which directly demonstrate the occurrence of a particular attenuation process and its ability to degrade the contaminants of concern.

  9. By documenting degradation, CSIA can provide the third line of evidence. In appropriate circumstances, CSIA be used to identify the mechanisms and provide an estimate of the rate of degradation.

  10. Analysis of Stable Carbon Isotope Ratios The ratio of stable isotopes is determined with an Isotope Ratio Mass Spectrometer (IRMS). The IRMS compares the ratio of 13C to 12C in the sample against the ratio of 13C to 12C in a reference standard.

  11. δ13C‰ Delta C thirteen is the conventional unit for the stable carbon isotope ratio in the sample. It is a measure of how much it varies from the standard. Notice that delta C thirteen is expressed in parts per thousand. You will see this expressed as o/oo or permil or per mill.

  12. Where R is the ratio of 13C to 12C in the sample and Rs is the ratio in the standard.

  13. molecules containing 12C are metabolized more rapidly than molecules containing 13C. As the organic compound is biodegraded, the residual compound is enriched in 13C.

  14. CSIR has two main applications for understanding degradation or organic contaminants. • to establish that degradation is happening. • To estimate rate constants for degradation that can be used to forecast future behavior of contamination.

  15. Enrichment in black dots when the rate of removal of black dots is 75% of the rate of removal of white dots.

  16. original ratio is 1/9 50 % remaining ratio is 1/6 25 % remaining ratio is 1/4 12.5 % remaining ratio is 1/3

  17. If you know the enrichment, you can estimate the extent of degradation

  18. What is the relationship between changes in the ratio of stable carbon isotopes and the extent of Biodegradation?Example for MTBE

  19. Stable Carbon Isotope Ratios of MTBE in Gasoline Worldwide values range from –28 o/oo to –33 o/oo O’Sullivan, G., G. Boshoff, A. Downey, and R. M. Kalin. “Carbon isotope effect during the abiotic oxidation of methyl-tert-butyl ether (MTBE). In Proceedings of the Seventh International In Situ and On-Site Bioremediation Symposium, Orlando, FL, 2003.

  20. 50 40 Natural Range in Gasoline 30 More 13C 20 10 C (per mil) anaerobic biodegradation aerobic biodegradation 0 13 d -10 -20 -30 -40 1 0.1 0.01 0.001 Fraction MTBE remaining (C/Co) 21

  21. 22

  22. ε is the “enrichment factor”, calculated as the slope of a linear regression of 13C on the natural logarithm of the fraction remaining of MTBE (C/Co or F).

  23. 50 40 Natural Range in Gasoline 30 More 13C 20 10 C (per mil) anaerobic biodegradation aerobic biodegradation 0 13 d -10 -20 -30 -40 1 0.1 0.01 0.001 Fraction MTBE remaining (C/Co) 24

  24. 25

  25. e Anaerobic Biodegradation, Isotopic Enrichment Factor = -12 0.001 0.01 Most Conservative Estimate MTBE Fraction Remaining (C/Co) 0.1 1 -40 -30 -20 -10 0 10 20 30 40 50 60 13 o d C ( / ) oo 26

  26. Application for an plume of MTBE from a spill of motor fuel from an underground storage tank

  27. OSWER Directive 9200.4-17Pin regard to- Demonstrating the Performance of MNA Three types of site-specific information may be required: • Historical ground water and/or soil chemistry data demonstrates a trend of declining contaminant concentration. • Hydrogeologic and geochemical data that demonstrate NA processes and rates. • Data from field or microcosm studies which directly demonstrate the occurrence of a particular attenuation process and its ability to degrade the contaminants of concern.

  28. Section 4 in A Guide for Assessing Biodegradation and Source Identification of Organic Ground Water Contaminants using Compound Specific Isotope Analysis (CSIA) EPA 600/R-08/148 | December 2008 | www.epa.gov/ada 29

  29. Google: EPA Ada Oklahoma Select: Ground Water and Ecosystems Restoration Research Go to publications in white menu bar on left. Open: Year Select 2008 Select “A Guide for Assessing Biodegradation and Source Identification of Organic Ground Water Contaminants using Compound Specific Isotope Analysis”

  30. Google: A Guide for Assessing Biodegradation and Source Identification of Organic Ground Water Contaminants using Compound Specific Isotope Analysis

  31. MW-11 318 MTBE (μg/L) N MW-10 <0.5 MW-7 106 MW-16 18 MW-6 490 MW-3 164 MW-8 25 TPHg >1,000 mg/kg TPHg >100 mg/kg MW-14 26,000 MW-12 3.6 MW-15 1 10 meters Underground Storage Tanks MW-9 <0.5 Dispenser Islands Samples collect 2004

  32. TPHg mg/kg ND 820 1 9000 1900 4600 100 feet 10 feet

  33. MW-11 318 N MW-10 <0.5 MW-7 106 MW-16 18 MW-6 490 MW-3 164 MW-8 25 TPHg >1,000 mg/kg TPHg >100 mg/kg MW-14 26,000 MW-12 3.6 MW-15 1 10 meters Underground Storage Tanks MW-9 <0.5 Dispenser Islands

  34. CH3 CH3 C O CH3 CH3 Tertiary Butyl Alcohol (TBA) is the first product of the biodegradation of MTBE. TBA is also a minor component of the technical grade of MTBE used in gasoline. The accumulation of TBA over time is an indication of the biodegradation of MTBE. CH3 CH3 C O H CH3

  35. 36

  36. e Anaerobic Biodegradation, Isotopic Enrichment Factor = -12 0.001 0.01 MTBE Fraction Remaining (C/Co) 0.1 1 -40 -30 -20 -10 0 10 20 30 40 50 60 13 o d C ( / ) oo 37

  37. MW-11 318 N MW-10 <0.5 MW-7 106 MW-16 18 MW-6 490 MW-3 164 MW-8 25 TPHg >1,000 mg/kg TPHg >100 mg/kg MW-14 26,000 MW-12 3.6 MW-15 1 10 meters Underground Storage Tanks MW-9 <0.5 Dispenser Islands

  38. MW-11 318 N MW-10 <0.5 MW-7 106 MW-16 18 MW-6 490 MW-3 164 MW-8 25 TPHg >1,000 mg/kg TPHg >100 mg/kg MW-14 26,000 MW-12 3.6 MW-15 1 10 meters Underground Storage Tanks MW-9 <0.5 Dispenser Islands

  39. MW-11 318 Does not Degrade N MW-10 <0.5 MW-7 106 Degrades MW-16 18 MW-6 490 MW-3 164 MW-8 25 TPHg >1,000 mg/kg There was substantial anaerobic biodegradation of MTBE in water from many wells. There was no evidence for biodegradation of MTBE in wells at the perimeter of the plume! TPHg >100 mg/kg MW-14 26,000 MW-12 3.6 MW-15 1 10 meters Underground Storage Tanks MW-9 <0.5 Dispenser Islands

  40. An approach to deal with heterogeneity in biodegradation • Determine if biodegradation (when it occurs) is stable over time. • Determine the extent of the core of the plume if controlled by biodegradation. • Determine the extent of the periphery of the plume there is no biodegradation.

  41. Reproducibility of Stable Carbon Isotope Ratios over time at field scale. 42

  42. The average hydraulic conductivity based on slug tests of monitoring wells was 11 meters per day. The average hydraulic gradient was 0.0023 meter/meter based on thirteen rounds of water table elevations. Assuming an effective porosity of 0.25, the average seepage velocity is 37 meters per year.

  43. F is the fraction of MTBE remaining d is the distance between the wells v is the ground water seepage velocity

  44. MW-11 318 Does not Degrade N MW-10 <0.5 MW-7 106 Degrades MW-16 18 MW-6 490 MW-3 164 MW-8 25 TPHg >1,000 mg/kg TPHg >100 mg/kg MW-14 26,000 MW-12 3.6 MW-15 1 10 meters Underground Storage Tanks MW-9 <0.5 Dispenser Islands

  45. =LN (0.0043)/11.7 seepage velocity is 37 meters per year

  46. = 37 meters per year * 0.46 per meter

  47. MW-11 318 N Degrades MW-10 <0.5 MW-7 106 MW-16 18 MW-6 490 MW-3 164 MW-8 25 TPHg >1,000 mg/kg TPHg >100 mg/kg MW-14 26,000 MW-12 3.6 MW-15 1 10 meters Underground Storage Tanks MW-9 <0.5 Dispenser Islands

  48. MW-11 318 Does not Degrade N MW-10 <0.5 MW-7 106 Degrades MW-16 18 MW-6 490 There was no evidence for biodegradation of MTBE in wells at the perimeter of the plume! MW-3 164 MW-8 25 TPHg >1,000 mg/kg TPHg >100 mg/kg MW-14 26,000 MW-12 3.6 MW-15 1 10 meters Underground Storage Tanks MW-9 <0.5 Dispenser Islands

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