Methane forensics techniques for source allocation

690 views

Published on

AWMA presentation on the use of stable isotopes and other environmental forensic techniques to determine the source of fugitive methane. Originally presented in 2007 at an AWMA conference in Calgary. The presentation covered an investigative of methane in areas around Calgary using different environmental and geoforensics techniques to identify the sources of methane at the different locations. A variety of analyses were used such as isotopic analysis, VOC analysis, and gas composition analysis.

Published in: Environment, Technology, Business
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total views
690
On SlideShare
0
From Embeds
0
Number of Embeds
5
Actions
Shares
0
Downloads
5
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide

Methane forensics techniques for source allocation

  1. 1. Use of Forensics to Identify Sources of Methane Presented by: Court Sandau, PhD, PChem November 15, 2007 Air and Waste Management Association’s Vapour Intrusion – A Rapidly Developing Environmental Challenge 1 © 2015 Chemistry Matters Inc.
  2. 2. Environmental Forensic Investigation “The application of scientific methods used to identify the origin and timing of a contaminant release” www.chemistry-matters.com 2© 2015 Chemistry Matters Inc.
  3. 3. When to use Environmental Forensics • When contamination may not be yours (remove liability) • When contamination is from multiple sources (share liability) www.chemistry-matters.com 3© 2015 Chemistry Matters Inc.
  4. 4. Implicate or Vindicate? • It may demonstrate your own responsibility • It may show dual responsibility (share the liability) • It may vindicate a party completely www.chemistry-matters.com 4© 2015 Chemistry Matters Inc.
  5. 5. Issues of Concern The client (municipality) 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 5© 2015 Chemistry Matters Inc.
  6. 6. Health Region Guidelines Subsurface Action Levels • Further investigation • Evaluation of indoor levels • Source removal or ventilation system • Further investigation • Monitoring, ventilation recommended • Immediate building evacuation, call 911 • Further investigation • Alarm, ventilation system, evacuation plan for nearby buildings 50,000 (100% LEL) Indoor Methane Concentration (ppm) 5,000 1,000 0 www.chemistry-matters.com 6© 2015 Chemistry Matters Inc.
  7. 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 www.chemistry-matters.com 7© 2015 Chemistry Matters Inc.
  8. 8. Forensic Geo-gas Investigation Multidisciplinary Approach to develop lines of evidence Measurement and interpretation of physical and chemical sampling data Historical documents Witness and knowledgeable individuals Area of highest confidence www.chemistry-matters.com 8© 2015 Chemistry Matters Inc.
  9. 9. Witness and Knowledgeable Individuals • Interview knowledgeable people regarding circumstances surrounding events and non-events www.chemistry-matters.com 9© 2015 Chemistry Matters Inc.
  10. 10. Historical Documents www.chemistry-matters.com 10© 2015 Chemistry Matters Inc.
  11. 11. Measurement and Interpretation Retention Time RelativeResponse S S www.chemistry-matters.com 11© 2015 Chemistry Matters Inc.
  12. 12. 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 Site Investigations indicate elevated CH4 Levels Borrow Pit/ Natural Vegetation www.chemistry-matters.com 12© 2015 Chemistry Matters Inc.
  13. 13. Investigation • Sampling location chosen based on historical data • 1L gas samples taken from 4 sample locations • Tiered Forensic Approach adopted to identify potential sources www.chemistry-matters.com 13© 2015 Chemistry Matters Inc.
  14. 14. Tiered Forensic Approach Calorific Value (BTU Ft3 ) Hydrocarbon Content Volatile Organic Carbon Content Level1 Fixed Gas Radio Active Isotope (14 C) Stable Isotope Analysis of CH4 Level2 www.chemistry-matters.com 14© 2015 Chemistry Matters Inc.
  15. 15. QA-QC • Duplicate sample collected at reference library sampling point • Relative Percent Differences <20% indicates good precision • Lab reported accuracy to within 2% of reference standards www.chemistry-matters.com 15© 2015 Chemistry Matters Inc.
  16. 16. Level 1: Fixed Gas Results Methane and Fixed Gas Data Library 0 10 20 30 40 50 60 70 80 90 100 H istoric Landfill Landfill Landfill Sew age Sew age N aturalG as N aturalG as U nknow n #1 U nknow n #2 Sampling Location Volume(%) O2 % CO2 % N2 % CH4% www.chemistry-matters.com 16© 2015 Chemistry Matters Inc.
  17. 17. Level 1: Hydrocarbon Fingerprinting Results 0 10 20 30 40 50 60 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14 C15 Alkane s Concentrationmg/m3 Natural Gas www.chemistry-matters.com 17© 2015 Chemistry Matters Inc.
  18. 18. Level 1: Hydrocarbon Fingerprinting Results 0 10 20 30 40 50 60 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14 C15 Alkanes Concentrationmg/m3 Landfill www.chemistry-matters.com 18© 2015 Chemistry Matters Inc.
  19. 19. Level 1: Hydrocarbon Fingerprinting Results 0 10 20 30 40 50 60 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14 C15 Alkanes Concentrationmg/m3 Sewage www.chemistry-matters.com 19© 2015 Chemistry Matters Inc.
  20. 20. Level 1: Hydrocarbon Fingerprinting Results 0 10 20 30 40 50 60 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14 C15 Alkanes Concentrationmg/m3 Unknown #1 www.chemistry-matters.com 20© 2015 Chemistry Matters Inc.
  21. 21. Level 1: Hydrocarbon Fingerprinting Results 0 10 20 30 40 50 60 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14 C15 Alkanes Concentrationmg/m3 Unknown #2 www.chemistry-matters.com 21© 2015 Chemistry Matters Inc.
  22. 22. Level 1: Hydrocarbon Fingerprinting Results www.chemistry-matters.com 22© 2015 Chemistry Matters Inc.
  23. 23. Level 1: VOC Fingerprinting Results 0 10 20 30 40 50 60 Volatile Organic Compounds Concentrationmg/m3 Natural Gas: Alkanes and Alkenes www.chemistry-matters.com 23© 2015 Chemistry Matters Inc.
  24. 24. Level 1: VOC Fingerprinting Results 0 10 20 30 40 50 60 Volatile Organic Compounds Concentrationmg/m3 Sewage: Sulfide Compounds www.chemistry-matters.com 24© 2015 Chemistry Matters Inc.
  25. 25. Level 1: VOC Fingerprinting Results 0 10 20 30 40 50 60 Volatile Organic Compounds Concentrationmg/m3 Landfill: Chlorinated Compounds www.chemistry-matters.com 25© 2015 Chemistry Matters Inc.
  26. 26. Level 1: VOC Fingerprinting Results 0 10 20 30 40 50 60 Volatile Organic Compounds Concentrationmg/m3 Unknown #1 www.chemistry-matters.com 26© 2015 Chemistry Matters Inc.
  27. 27. Level 1: VOC Fingerprinting Results 0 10 20 30 40 50 60 Volatile Organic Compounds Concentrationmg/m3 Unknown #2 www.chemistry-matters.com 27© 2015 Chemistry Matters Inc.
  28. 28. Summary of Level 1 Findings • 2 locations had elevated levels of CH4 • Based on calorific and fixed gas data Thermogenic sources were ruled out • Unable to differentiate landfill, sewage sources using level 1 investigation • Need to progress to Level 2 www.chemistry-matters.com 28© 2015 Chemistry Matters Inc.
  29. 29. Radio Carbon Isotope Dating 14 C •Naturally occurring isotope with a half life of 5730 yrs •The ratio of 14 C contained within CH4 is indicative of age 50% Age 5730 yr 100% Age 0 … …. 25% Age 11,460 yr Natural Gas Landfill Sewage Unknown 14 C (pMc) 0 >100 100-110 141 www.chemistry-matters.com 29© 2015 Chemistry Matters Inc.
  30. 30. Stable Isotope Analysis • Highly variable in nature and generally endemic of every organic compound • Have been used with petroleum exploration for many decades, advance is isotope techniques has led to new areas of applications e.g. archaeology, biomedical sciences, biosynthesis and environmental forensics pp ee-- Hydrogen,1 H nn pp ee-- Deuterium,Deuterium,22 H, DH, D nn pp nn ee-- Tritium,Tritium,33 H, TH, T 99 % ~1 % <1 % www.chemistry-matters.com 30© 2015 Chemistry Matters Inc.
  31. 31. Clarke Diagram for 2D Fingerprinting δ13 C-CH4(‰) Bacterial MF δ2 H-CH4 (‰) Bacterial Carbonate Reduction Bacterial M ixand Transition Early Mature Thermogenic migration Bacterial Oxidation www.chemistry-matters.com 31© 2015 Chemistry Matters Inc.
  32. 32. Combination of Techniques δ13 C-CH4 (‰) C1/[C2+C3] Sewage Plant Sewage Plant Unknown Unknown Landfill Landfill Historic Landfill Natural Gas Natural Gas Bacterial consumption of Methane will cause a reduction in Methane concentration and isotopic shift Migration will cause a change in methane concentration but not a large isotopic shift Migration Migration Oxidation www.chemistry-matters.com 32© 2015 Chemistry Matters Inc.
  33. 33. Summary Source Calorifi c Value (BTU/Ft 3 ) CH4 /CO 2 GC Carbon Analysis VOC 14 C – pMC δ13 C and δ2 H of CH4 Thermogenic ~ 1000 + CH4 Low C1 /C1 – C5 Odorants 0 pMC δ13 C = -48‰ to -40‰ δ2 H = -250‰ to -200‰ Landfill ~600 CO2 = CH4 High C1 /C1 – C5 chlorinated compounds >100 pMC δ13 C = -60‰ to -52‰ δ2 H = -400‰ to -350‰ Sewage ~600 CO2 = CH4 High C1 /C1 – C5 Sulphur containing 100 -110 pMC δ13 C = -52‰ to -48‰ δ2 H = -425‰ to -375‰ Unknown1 ~447 CO2 < CH4 High C1 /C1 – C5 ND 141 pMC δ13 C = -54.5‰ δ2 H = -346‰ Unknown2 ~26 CO2 = CH4 High C1 /C1 – C5 ND 101 pMC δ13 C = -51.5‰ δ2 H = -341‰ Level 1 Level 2 www.chemistry-matters.com 33© 2015 Chemistry Matters Inc.
  34. 34. Summary Source Calorifi c Value (BTU/Ft 3 ) CH4 /CO 2 GC Carbon Analysis VOC 14 C – pMC δ13 C and δ2 H of CH4 Thermogenic ~ 1000 + CH4 Low C1 /C1 – C5 Odorants 0 pMC δ13 C = -48‰ to -40‰ δ2 H = -250‰ to -200‰ Landfill ~600 CO2 = CH4 High C1 /C1 – C5 chlorinated compounds >100 pMC δ13 C = -60‰ to -52‰ δ2 H = -400‰ to -350‰ Sewage ~600 CO2 = CH4 High C1 /C1 – C5 Sulphur containing 100 -110 pMC δ13 C = -52‰ to -48‰ δ2 H = -425‰ to -375‰ Unknown1 ~447 CO2 < CH4 High C1 /C1 – C5 ND 141 pMC δ13 C = -54.5‰ δ2 H = -346‰ Unknown2 ~26 CO2 = CH4 High C1 /C1 – C5 ND 101 pMC δ13 C = -51.5‰ δ2 H = -341‰ Level 1 Level 2 Potentially a mixed source www.chemistry-matters.com 34© 2015 Chemistry Matters Inc.
  35. 35. Conclusion • Main Issue for client was identification of potential sources of fugitive methane emissions • Outcomes – Generation of Library – Use of historical data and Level 1 analysis eliminated thermogenic sources – Level 2 data indicate degradation of landfill material may be responsible for methane found at sampling point with highest concentration – Second sampling point likely to be of a mixed source with landfill and organic soils contributing • Further monitoring may determine the fate and behavior of elevated methane which will help clients to make decision regarding any action needed www.chemistry-matters.com 35© 2015 Chemistry Matters Inc.
  36. 36. 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.

×