AWMA 2010 methane forensics in urban setting
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Using environmental forensics techniques to identify fugitive methane. Techniques included VOCs, fixed gases, stable isotopes, and radioactive carbon to identify soil gas samples from a variety of urban settings.
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AWMA 2010 methane forensics in urban setting
- 1. Source and Fate of Methane Within an Urban Setting Court D. Sandau, PhD, PChem (csandau@chemistry-matters.com) Presented at AWMA Conference 2010 © 2015 Chemistry Matters Inc.
- 2. • Thank you to the City of Calgary for support on this project • Work presented was published in the following citation: • O’Sullivan et al. 2010, Forensics Geo-Gas Investigation of Methane: Characterization of Sources within an Urban Setting, Environmental Forensics, 11, 108-116. Acknowledgements www.chemistry-matters.com 2© 2015 Chemistry Matters Inc.
- 3. Outline • Introduction • Methane Reference Library – Project Background – Sites & Sampling Locations – Forensic Analytical Program • Case Study – Project Background – Site & Sampling Locations – Forensic Analytical Program www.chemistry-matters.com 3© 2015 Chemistry Matters Inc.
- 4. Methane • Colorless, odorless, flammable gas which is typically classified by the process by which it is formed • Thermogenic (aka petrogenic): Abiotic thermal cracking of buried organic material • Bacterial: Anaerobic microbial degradation of organic matter • CO2 +8H++8e- → CH4 + 2H2O (Carbonate Reduction) • CH3COOH → CH4 +CO2 (Acetate Fermentation) www.cartoonstock.com www.chemistry-matters.com 4© 2015 Chemistry Matters Inc.
- 5. Fugitive Methane Emissions Risk = Asphyxiation and Potential for Explosion www.chemistry-matters.com 5© 2015 Chemistry Matters Inc.
- 6. Issues of Concern The City of Calgary has identified fugitive methane gas in the subsurface soils of several different areas of the city – Unknown source – Concerned residents – Possible health risks – Potential legal action www.chemistry-matters.com 6© 2015 Chemistry Matters Inc.
- 7. Forensic GEO-Gas Investigation (FGI) • Collect gas samples from various origins • Characterize each source and create a reference library • Establish the composition and source of the fugitive gases through comparisons with the reference library 3 Landfills 2 Sewage Treatment Facilities 2 Natural Gas 4 Sedimentary Organic Matter* www.chemistry-matters.com 7© 2015 Chemistry Matters Inc.
- 8. Investigation • Historical Review • Field Measurements, Fixed Gases e.g. CH4 • Gas samples were collected in 1-litre gas bag and CarbotrapTM • Tiered Forensic Approach adopted to identify potential sources www.chemistry-matters.com 8© 2015 Chemistry Matters Inc.
- 9. Tiered Forensic Approach Hydrocarbon Content Volatile Organic Carbon Content Level1 Fixed Gas Radio Active Isotope (14C) Stable Isotope Analysis of CH4 Level2 www.chemistry-matters.com 9© 2015 Chemistry Matters Inc.
- 10. Results of Level 1 www.chemistry-matters.com 10© 2015 Chemistry Matters Inc.
- 11. Results: Fixed Gas 0 10 20 30 40 50 60 70 80 90 100 Volume(%) H2S CH4 CO N2 CO2 O2 Ar H2 He * * www.chemistry-matters.com 11© 2015 Chemistry Matters Inc.
- 12. Fixed Gas 0 5 10 15 20 25 30 35 40 45 0 10 20 30 40 50 60 70 80 90 Nitrogen (volume %) CarbonDioxide(volume%) Landfill and Sewage Suspected Sedimentary Organic Matter Thermogenic Similar to Atmospheric Distribution = OM4 and OM3 Ruled out of Library www.chemistry-matters.com 12© 2015 Chemistry Matters Inc.
- 13. Fixed Gases 0 10 20 30 40 50 60 70 80 90 100 0 5 10 15 20 25 30 35 40 45 Carbon Dioxide (% volume) Methane(%volume) Thermogenic Landfill and Sewage Suspected Organic Material CH4 → Biomass CH3COOH → CH4 + CO2 CO2 + 8H+ + 8e- → CH4 + 2H2O CO2 + water → CaCO3 (s) www.chemistry-matters.com 13© 2015 Chemistry Matters Inc.
- 14. Results: VOC Fingerprinting 0 10 20 30 40 50 60 Landfill: Chlorinated Compounds Sewage: Sulfide Compounds Natural Gas: Alkanes and Alkenes Volatile Organic Compounds Concentrationmg/m3 Although CH4 and CO2 dominant: trace gases may also be present www.chemistry-matters.com 14© 2015 Chemistry Matters Inc.
- 15. Results: VOC Fingerprinting 1 0 2 Concentration(mg/m3) OM3: Acetone; potential to be mixed source OM1: BTEXs and Alkybenzenes; potential to be mixed source OM2 Volatile Organic Compounds www.chemistry-matters.com 15© 2015 Chemistry Matters Inc.
- 16. 0 10 20 30 40 50 60 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14 C15 Alkanes Concentrationmg/m3 Natural Gas Results: HC Fingerprint www.chemistry-matters.com 16© 2015 Chemistry Matters Inc.
- 17. 0 10 20 30 40 50 60 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14 C15 Alkanes Concentrationmg/m3 Landfill Results: HC Fingerprint www.chemistry-matters.com 17© 2015 Chemistry Matters Inc.
- 18. 0 10 20 30 40 50 60 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14 C15 Alkanes Concentrationmg/m3 Sewage Results: HC Fingerprint www.chemistry-matters.com 18© 2015 Chemistry Matters Inc.
- 19. Summary- Level 1 Source CH4/CO2 Carbon Analysis VOC Natural Gas + CH4 Low C1 /C1 – C5 Odorants Landfill CO2 = CH4 High C1 /C1 – C5 Chlorinated compounds Sewage CO2 = CH4 High C1 /C1 – C5 Sulfur Containing Natural Organics CO2< CH4 High C1 /C1 – C5 Low www.chemistry-matters.com 19© 2015 Chemistry Matters Inc.
- 20. Results of Level 2 www.chemistry-matters.com 20© 2015 Chemistry Matters Inc.
- 21. Radio Carbon Isotope 14C Naturally occurring isotope with a half life of 5730 yrs Measure in percent Modern Carbon (pMC) www.chemistry-matters.com 21© 2015 Chemistry Matters Inc.
- 22. Radio Carbon Dating Relies on the radioactive nature and influence of events such as nuclear testing and fossil fuel burning www.chemistry-matters.com 22© 2015 Chemistry Matters Inc.
- 23. Results: 14C Post 1950’s -10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 14C-CH4 pMC Landfill (this study) Sewage Sedimentary Organic Soil Natural Gas Glacial Drift Gas Landfill (Coleman et al 1995) Swamp and Marsh www.chemistry-matters.com 23© 2015 Chemistry Matters Inc.
- 24. Stable Isotope Fingerprinting • Atoms of same element with differing masses; same # of protons, different # of neutrons • Highly variable in nature and generally endemic of every organic compound • Ratio of a pair of isotopes e.g. 13C/12C produces a useful tracer p e- Hydrogen,1H n p e- Deuterium,2H, D n p n e- Tritium,3H, T 99% ~1% <1% www.chemistry-matters.com 24© 2015 Chemistry Matters Inc.
- 25. Stable Isotope Analysis Bacterial MF 13C vs 2H on CH4 Fingerprinting 2H-CH4 (‰) 13C-CH4(‰) Bacterial Carbonate Reduction Bacterial migration after Whiticar, M.J., 1999 Organic matter www.chemistry-matters.com 25© 2015 Chemistry Matters Inc.
- 26. Summary of Library Source CH4/CO2 Carbon Analysis VOC 14C – pMC δ13C and δ2H of CH4 Thermogenic + CH4 Low C1 /C1 – C5 Odorants 0 pMC δ13C = -48‰ to - 40‰ δ2H = -250‰ to - 200‰ Landfill CO2 = CH4 High C1 /C1 – C5 chlorinated compounds >100 pMC δ13C = -60‰ to -52‰ δ2H = -400‰ to - 350‰ Sewage CO2 = CH4 High C1 /C1 – C5 sulfur containing >100 pMC δ13C = -52‰ to - 48‰ δ2H = -425‰ to - 375‰ Natural Organics CO2< CH 4 High C1 /C1 – C5 Low <100 pMC δ13C = -63‰ to -50‰ δ2H = -345‰ to - 322‰ Level 1 Level 2 www.chemistry-matters.com 26© 2015 Chemistry Matters Inc.
- 27. FGI Investigation: Former Nuisance Grounds www.chemistry-matters.com 27© 2015 Chemistry Matters Inc.
- 28. Case History Pre 1940’s 1950’s 1960’s 1970’s 1980’s 1990’s 2000’s 1953: nuisance ground operation began 1963: nuisance ground operation closed 2001-2005: Phase I&II indicate elevated CH4 Levels Borrow Pit/ Natural Vegetation www.chemistry-matters.com 28© 2015 Chemistry Matters Inc.
- 29. 1952 Clearing began but vegetation still evident in northern part of site www.chemistry-matters.com 29© 2015 Chemistry Matters Inc.
- 31. Methane was encountered at four locations www.chemistry-matters.com 31© 2015 Chemistry Matters Inc.
- 32. 0.01 0.10 1.00 Concentration(mg/m 3 ) Volatile Organic Compounds Concentrationmg/m3 Alkane, alkene, cycolalkenes, alkylbenzene, and BTEXs TWO SOURCES? or degradation and one source www.chemistry-matters.com 32© 2015 Chemistry Matters Inc.
- 33. Bacterial MF Clarke Diagram for fingerprinting 2H-CH4 (‰) 13C-CH4(‰) Bacterial Carbonate Reduction Bacterial Stable Isotope Analysis after Whiticar, M.J., 1999 www.chemistry-matters.com 33© 2015 Chemistry Matters Inc.
- 34. Bacterial MF Clarke Diagram for well MW03-001 2H-CH4 (‰) 13C-CH4(‰) Bacterial Carbonate Reduction Bacterial Stable Isotope Analysis after Whiticar, M.J., 1999Date CH4 (%) June 2007 December 2007 May 2009 February 2010 44.12 23.36 27.08 13.24 www.chemistry-matters.com 34© 2015 Chemistry Matters Inc.
- 35. Results: 14CH4 0 20 40 60 80 100 120 140 160 MW04-006-D MW04-011 MW03-001-D MW04-013 MW03-001-J MW04-006-J 14C-CH4(pMC) Winter Summer www.chemistry-matters.com 35© 2015 Chemistry Matters Inc.
- 36. Two bacterial methane sources of different ages Post 1950’s -10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 14C-CH4 pMC Landfill (this study) Sewage Sedimentary Organic Soil Natural Gas Glacial Drift Gas Landfill (Coleman et al 1995) Swamp and Marsh www.chemistry-matters.com 36© 2015 Chemistry Matters Inc.
- 37. Three out of four wells analyzed showed methane oxidation was occurring, suggesting that conditions were naturally present to control the concentration of methane, therefore, no need to go in and dig out whole area Good News for Client www.chemistry-matters.com 37© 2015 Chemistry Matters Inc.
- 38. Results of Study: – Two potential sources identified, landfill and organic material – Use of stable and radio isotope not only indicated source but also gave information pertaining to the risk associated with the fate and behavior of elevated methane which helps client to make decision regarding action needed – Tiered Forensic approach required to confidently identify sources www.chemistry-matters.com 38© 2015 Chemistry Matters Inc.
- 39. Q u e s t i o n s ? www.chemistry-matters.com 39© 2015 Chemistry Matters Inc.
- 40. Contact Info: Chemistry Matters Inc. Court Sandau Cell: 1.403.669.8566 Email: csandau@chemistry-matters.com URL: chemistry-matters.com Twitter: @Chem_Matters Slideshare: www.slideshare.net/csandau © 2015 Chemistry Matters Inc.
Editor's Notes
- Both slides are in… one with the picture of the City and this one. This one has no animation.
- Would it be better to focus this slide on FGI e.g. next slide
- Remove names in charts; start with empty chart then fly in bars and title for multiple samples
- Bacterial oxidation of methane converting to biomass, causes a decrease in methane (make a thermo source resemble a SOM) Acetate from carbs/proteins/lipids fermenting causing increased CH4 and CO2 In the absence of more favourable electron donors (oxygen, ferric iron, manganese, nitrate), bacteria may reduce CO2 to CH4
- Remove names in charts; start with empty chart then fly in bars and title for multiple samples
- Need to improve drawings
- 1: Isotopic signature of source material, 2: Isotopic effect associated with migration and degradation
- A different way to present the findings, might be better at the end for a visual summary. Replacing Garrison Woods info with MGN
- Evolution of lines of evidence
- 1: Isotopic signature of source material, 2: Isotopic effect associated with migration and degradation