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AWMA 2010 methane forensics presentation TRIUM
 

AWMA 2010 methane forensics presentation TRIUM

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Using environmental forensics techniques to identify fugitive methane. Techniques included VOCs, fixed gases, stable isotopes, and radioactive carbon.

Using environmental forensics techniques to identify fugitive methane. Techniques included VOCs, fixed gases, stable isotopes, and radioactive carbon.

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  • 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

AWMA 2010 methane forensics presentation TRIUM AWMA 2010 methane forensics presentation TRIUM Presentation Transcript

  • Source and Fate of Methane Within an Urban Setting Court D. Sandau , PhD, PChem (csandau@triuminc.com)
    • Team at TRIUM:
      • Gwen O’Sullivan, PhD, P.Chem, MRSC
      • B.J. Min, P.Eng
      • Jay Bilyk, B.Sc, P.Chem
    • O’Sullivan et al. 2010, Forensics Geo-Gas Investigation of Methane: Characterization of Sources within an Urban Setting, Environmental Forensics , 11 , 108-116.
    ACKNOWLEDGEMENTS
  • OUTLINE
    • INTRODUCTION
    • METHANE REFERENCE LIBRARY
      • Project Background
      • Sites & Sampling Locations
      • Forensic Analytical Program
    • CASE STUDY
      • Project Background
      • Site & Sampling Locations
      • Forensic Analytical Program
  • 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
        • CO 2 +8H + +8e - -> CH 4 + 2H 2 O (Carbonate Reduction)
        • CH 3 COOH -> CH 4 +CO 2
        • (Acetate Fermentation)
  • Risk = Asphyxiation and Potential for Explosion FUGITIVE METHANE EMISSIONS
  • ISSUES OF CONCERN
    • The client had identified fugitive methane gas in the subsurface soils of several different areas
      • Unknown source
      • Concerned residents
      • Possible health risks
      • Potential legal action
  • 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*
  • INVESTIGATION
    • Historical Review
    • Field Measurements, Fixed Gases e.g. CH 4
    • Gas samples were collected in 1-litre gas bag and Carbotrap TM
    • Tiered Forensic Approach adopted to identify potential sources
  • TIERED FORENSIC APPROACH Hydrocarbon Content Volatile Organic Carbon Content Level 1 Fixed Gas Radio Active Isotope ( 14 C) Stable Isotope Analysis of CH 4 Level 2
  • RESULTS OF LEVEL 1
  • RESULTS: FIXED GAS 0 10 20 30 40 50 60 70 80 90 100 Volume (%) H 2 S CH 4 CO N 2 CO 2 O 2 Ar H 2 He * * OM4 OM1 OM3_a OM3 OM2_a OM2_b Sewage B Sewage A Landfill A Landfill B Landfill C Natural Gas A Natural Gas B
  • FIXED GAS 0 5 10 15 20 25 30 35 40 45 0 10 20 30 40 50 60 70 80 90 Nitrogen (volume %) Carbon Dioxide (volume %) Landfill and Sewage Suspected Sedimentary Organic Matter Thermogenic
  • 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) CH 4 -> Biomass CH 3 COOH -> CH 4 + CO 2 CO 2 + 8H + + 8e - -> CH 4 + 2H 2 O Thermogenic Landfill and Sewage Suspected Organic Material CO 2 + water -> CaCO 3 (s)
  • RESULTS: VOC FINGERPRINTING 0 10 20 30 40 50 60 Volatile Organic Compounds Concentration mg/m 3 Although CH 4 and CO 2 dominant: trace gases may also be present Natural Gas: Alkanes and Alkenes Increasing Molecular Weight
  • RESULTS: VOC FINGERPRINTING 0 10 20 30 40 50 60 Volatile Organic Compounds Concentration mg/m 3 Although CH 4 and CO 2 dominant: trace gases may also be present Sewage: Sulfide Compounds Increasing Molecular Weight
  • RESULTS: VOC FINGERPRINTING 0 10 20 30 40 50 60 Volatile Organic Compounds Concentration mg/m 3 Although CH 4 and CO 2 dominant: trace gases may also be present Landfill: Chlorinated Compounds Increasing Molecular Weight
  • RESULTS: VOC FINGERPRINTING 1 Concentration (mg/m 3 ) Volatile Organic Compounds 0 2 OM3: Acetone; potential to be mixed source OM1: BTEXs and Alkybenzenes; potential to be mixed source OM2 Increasing Molecular Weight
  • RESULTS: HC FINGERPRINT 0 10 20 30 40 50 60 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14 C15 Alkanes Concentration mg/m 3 Natural Gas Landfill Sewage
  • SUMMARY- LEVEL 1 Source CH 4 /CO 2 Carbon Analysis VOC Natural Gas + CH 4 Low C 1 /C 1 – C 5 Odorants Landfill CO 2 = CH 4 High C 1 /C 1 – C 5 Chlorinated compounds Sewage CO 2 = CH 4 High C 1 /C 1 – C 5 Sulfur Containing Natural Organics CO 2 < CH 4 High C 1 /C 1 – C 5 Low
  • RESULTS OF LEVEL 2
  • RADIO CARBON ISOTOPE 14 C Naturally occurring isotope with a half life of 5730 yrs Measure in percent Modern Carbon (pMC)
  • RADIO CARBON DATING Relies on the radioactive nature and influence of events such as nuclear testing and fossil fuel burning
  • RESULTS: 14 C Post 1950’s -10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 14 C-CH 4 pMC Landfill (this study) Sewage Sedimentary Organic Soil Natural Gas Glacial Drift Gas Landfill (Coleman et al 1995) Swamp and Marsh
  • 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. 13 C/ 12 C produces a useful tracer
    99% ~1% <1% p e - Hydrogen, 1 H n p e - Deuterium, 2 H, D n p n e - Tritium, 3 H, T
  • Bacterial MF Clarke Diagram for fingerprinting  2 H-CH 4 (‰)  13 C-CH 4 (‰) Bacterial Carbonate Reduction Bacterial Mix and Transition Early Mature Thermogenic migration Bacterial Oxidation after Whiticar, M.J., 1999 Organic matter Stable Isotope Analysis
  • Level 1 Level 2 SUMMARY OF LIBRARY Source CH 4 /CO 2 Carbon Analysis VOC 14 C –pMC δ 13 C and δ 2 H of CH 4 Thermogenic + CH 4 Low C 1 /C 1 – C 5 Odorants 0 pMC δ 13 C = -48‰ to -40‰ δ 2 H = -250‰ to -200‰ Landfill CO 2 = CH 4 High C 1 /C 1 – C 5 chlorinated compounds >100 pMC δ 13 C = -60‰ to -52‰ δ 2 H = -400‰ to -350‰ Sewage CO 2 = CH 4 High C 1 /C 1 – C 5 sulfur containing >100 pMC δ 13 C = -52‰ to -48‰ δ 2 H = -425‰ to -375‰ Natural Organics CO 2 < CH 4 High C 1 /C 1 – C 5 Low <100 pMC δ 13 C = -63‰ to -50‰ δ 2 H = -345‰ to -322‰
  • FGI INVESTIGATION: FORMER NUISANCE GROUNDS
  • 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 CH 4 Levels Borrow Pit/ Natural Vegetation
  • 1952 Clearing began but vegetation still evident in northern part of site
  • 1969
  • Methane was encountered at four locations
  • Volatile Organic Compounds Concentration mg/m 3 Alkane, alkene, cycolalkenes, alkylbenzene, and BTEXs TWO SOURCES? or degradation and one source
  • Early Mature Thermogenic Bacterial MF Clarke Diagram for fingerprinting  2 H-CH 4 (‰)  13 C-CH 4 (‰) Bacterial Carbonate Reduction Bacterial Mix and Transition STABLE ISOTOPE ANALYSIS after Whiticar, M.J., 1999
  • Early Mature Thermogenic Bacterial MF Clarke Diagram for One Monitoring Well  2 H-CH 4 (‰)  13 C-CH 4 (‰) Bacterial Carbonate Reduction Bacterial Mix and Transition Bacterial Oxidation after Whiticar, M.J., 1999 44.12 23.36 27.08 13.24 STABLE ISOTOPE ANALYSIS Date CH 4 (%) June 2007 December 2007 May 2009 February 2010
  • RESULTS: 14 CH 4 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 14 C- CH 4 (pMC) Winter Summer
  • Post 1950’s -10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 14 C-CH 4 pMC Landfill (this study) Sewage Sedimentary Organic Soil Natural Gas Glacial Drift Gas Landfill (Coleman et al 1995) Swamp and Marsh Two Bacterial Methane Sources of Different Ages
  • 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
  • RESULTS OF STUDY
      • Two potential sources identified, landfill and organic material
      • Stable and radio isotope data
        • indicated sources
        • 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
      • A tiered forensic approach required to confidently identify sources
  • Q u e s t i o n s ? Court Sandau email: [email_address] web: www.triuminc.com blog: http://environmental- qaqc.blogspot.com / We are also on Facebook